Final Flashcards
(482 cards)
1
Q
At what # cell stage of development do the round blastomeres begin to flatten?
A
At 8-cell stage, developing an inside-outside polarity that maximizes cell-to-cell contact among blastomeres.
2
Q
What is the functional matrix theory of growth?
A
It states that there is innate growth potential in the long bones, but neither the cartilage of the mandibular condyle nor the nasal septum is a determinant of jaw growth (contradicts our text book which considers the nasal septum as a primary growth center, and that is what we will go with in this class). It says that neither bone nor cartilage is the determinant for growth of the craniofacial skeleton, and that means that the control would be in the adjacent soft tissue. It also says that growth of the face occurs as a response to functional needs, and neurotrophic influences, and is mediated by the soft tissue in which the jaws are embedded. So the soft tissue grows, and both bone and cartilage react to his form of epigenetic (indirect control). The theory says that stimuli emanating in the growing head and body (the functional matrix), directly or indirectly, function to turn on or off cellular organelle activity in genetic material. This concept is not intended to explain how the actual morphogenic process works, but rather describe what happens to achieve the complex combination of actions. Moss theorized that the major determinant of growth of the maxilla and the mandible is the enlargement of the nasal and oral cavities, which grow in response to functional needs (Moss is unsure how functional needs are transmitted to these tissues).
3
Q
What is the purpose of Mitosis?
A
Before a cell can divide, it must replicate its DNA first so that each new daughter cell will receive a complete copy of the DNA.
4
Q
What forms the nasal septum?
A
While the secondary palate is forming, ectoderm and mesoderm of the frontonasal process proliferate to form the nasal septum that grows down from the roof of the nasal cavity to fuse with the upper surface of the primary and secondary palates, divides the nasal cavity into two nasal passages.
5
Q
What is a LeFort I fracture?
A
A horizontal fracture through the maxilla that passes through the septum medially, and these result in a mobile hard palate.
6
Q
Which arteries does the six pharyngeal arch give rise to?
A
The ductus arterious and the definitive pulomonary arteries
7
Q
What is interstitial growth?
A
Growth that occurs at all points within the tissue, and this involves growth of soft tissues that occurs by a combination of hyperplasia and hypertrophy.
8
Q
What does the second arch cartilage, which originates from neural crest cells, give rise to?
A
Stapes, styloid process, styloid hyoid ligament, lesser horn of hyoid bone, upper rim of body of hyoid bone.
9
Q
What happens during Anaphase of Mitosis?
A
Anaphase begins when the duplicated centromeres of each pair of sister chromatids separate, and the now-daughter chromosomes begin moving toward opposite poles of the cell due to the action of the spindle. Depending on where the centromere is located along the chromosome, a characteristic shape appears during chromosome movement. There are V and J shapes. J in the middle and V on edges. At the end of anaphase, a complete set of chromosomes has assembled at each pole.
10
Q
During what stage does the enamel organ form?
A
Bell stage, and it forms from the dental lamina.
11
Q
What percent of Down Syndrome cases are hereditary vs random?
A
1% hereditary, 99% random.
12
Q
What kind of head and face abnormalities do down syndrome patients have?
A
Hypodontia, protrude tongue, brachycephaly, epicanthal folds, short hard palate, enlarged tongue, flat facial profile, hypoplasia of midface, high incidence of class III occlusion and open bites because of it.
13
Q
How many amino acids does PTH consist of?
A
84 amino acids, and is secreted in response to hypocalcemia and hyperphosphatemia.
14
Q
How does the growth of the mandible primarily take place?
A
It occurs by both endochondral proliferation at the condyle and by apposition and resorption of bone at the bony surfaces. It seems clear that the mandible is translated in space by growth of muscles and other adjacent soft tissues and that addition of new bone at the condyle is in response to these soft tissues changes.
15
Q
What is DiGeorge syndrome?
A
It is caused by a deletion in the long (q) arm of chromosome 22. 22q11.2 deletion. And this deletion leads to hypoplasia of 3rd and 4th pouch derivatives.
16
Q
What is Treacher Collins Syndrome?
A
A generalized lack of mesenchymal tissue in the lateral part of the face, a genetic disorder, about 1 in 50,000. Usually have very small cheek bones and micrognathia, cleft palate, eyes that slant downward, coloboma, normal intelligence. Patients are referred to specialist between 4 and 7 for surgery.
17
Q
What does the intermaxillary suture contain when an individual is growing?
A
Cartilage. This allows us to move the palate with an expansion device up to the age of 9 and 10.
18
Q
What are the four main functions of saliva?
A
- Buffering ability2. Provides a cleansing effect3. Has antibacterial action4. Maintenance of oral environment
19
Q
During Meiosis I or II is the chromosomal number reduced from diploid 2n to haploid 1n?
A
During Meiosis I
20
Q
Which artery does the second pharyngeal arch give rise to?
A
The stapedial artery
21
Q
What does the tongue develop from?
A
From endodermal covered swellings on the floor of the pharynx.
22
Q
What is Craniofacial Microsomia?
A
Caused by lack of neural crest cells, those that migrate to lateral and lowest parts of face have defects. They also usually have deformed external ear.
23
Q
What is chromatin?
A
The combination of DNA, histone, and other proteins that make up chromosomes and is found inside the nuclear envelope of eukaryotic cells.
24
Q
Dentinogenesis takes place throughout our entire lives. True or False?
A
True. Secondary dentin production happens.
25
What does sagittal synostosis result in?
Bitemporal narrowing and prominence in frontal and occipital.
26
What do all cleft lip and palate patients receive before undergoing surgical repair?
Pre-surgical orthopedic treatment.
27
What is the difference between growth sites and growth centers?
A growth site is merely a location at which growth occurs, a growth center is a location at which independent (genetically controlled) growth occurs.
28
What are some bodily physical abnormalities in down syndrome patients?
Small stature, dysplasia of pelvis, dysplasia of midphalanx of fifth finger, short metcarpals and phalanges, simian crease, cardiac anomalies (often needed to consult with cardiologist for antibiotic prophylasix, wide gap between first and second toe.
29
What are the two ways that help the maxilla grow downward and forward relative to the cranium and cranial base?
1. A push from behind created by the cranial base growth 2. Growth at the sutures -Before the age of 7, it is largely the cranial base growth doing the work, and at 7, the cranial base growth stops and sutural growth is the only mechanism for bringing the maxilla forward. This is accomplished by growth of the soft tissue.
30
When can a neonatal mandibular distraction osteogenesis be used?
It can be used to treat Pierre Robin syndrome. It starts with an osteotomy on both sides of lower jaw, and a small metal device is placed under the skin, two days later, a callus forms, and the device is activated and slowly opens the osteotomy gap and moves the lower jaw forward and opens the baby's airway, and weeks later, the device is removed.
31
What is the main cause of a teratoma?
When a primordial germ cell becomes stranded during migration to the dorsal body wall, they can rest at extragonadal sites and can give rise to a teratoma.
32
What are some factors that affect growth besides genetic factors?
Nutrition, health, illness, physical ativity, etc.
33
How does fusion of the secondary palate take place?
First ventrally and then proceeds dorsally along the midline.
34
What is minor clefting?
Involves only the soft tissue of the lip and results in a notch in the vermillion border of the lip just lateral to the philtrum called a partial cleft.
35
Why is Vitamin D essential and what can it's deficiency lead to?
It is essential for the body to absorb calcium, for bone development, immune functioning, and alleviation of inflammation. It's deficiency can lead to rickets, weakened immune system, osteomalacia, etc. Too much of it though can lead to increased risk of heart disease and kidney stones because of body absorbing too much calcium.
36
Amelogenesis takes place throughout our entire lives. True or False?
False. it only happens once, and ends once the ameloblasts are lost within eruption within the REE.
37
What are the two main drugs that can cause cleft lip?
1. Phenytoin - anticonvulsant2. Vitamin A (Accutane)
38
What happens during Metaphase of Mitosis?
The centrosomes are at opposite poles of the cell, and the chromosomes are highly coiled condensed and arranged at the metaphase plate. Each sister chromatid is attached to a kinetochore microtubule coming from the closest pole.
39
With TNM staging, what is N2a, N2b, and N2c?
N2a is when it has spread to one lymph node on the same side as the primary tumor and it measures from 3-6 cm across.N2b is when it has spread to 2 or more lymph nodes on same side and none larger than 6 cm across.N2c is when it has spread to one or more lymph nodes on both sides of neck or opposite side of tumor, and none larger than 6 cm across.
40
What does the fourth pharyngeal pouch develop into?
Dorsal portion of fourth pharyngeal pouch develops into the superior parathyroid gland, while ventral portion develops into the ultimobranchial body, which is a sac or pouch
41
Is there more growth of the lower limbs or the upper limbs during postnatal life?
Lower limbs
42
What is a secondary tumor?
A tumor that formed from cells that have spread.
43
What are the main three synchondroses in the cranial base?
1. Spheno-occipital synchondroses 2. Inter-sphenoid synchondroses 3. Spheno-ethmoid synchondroses
44
What is the primitive choana?
It is formed when the oronasal membrane ruptures during the seventh week to form an opening called the primitive choana.
45
What is the name of the area formerly known as the blastocyst cavity once Heuser's membrane has formed?
It is now called the primary yolk sac.
46
What do the maxillary swellings do during the fifth week?
They enlarge and grow ventrally and medially simultaneously.
47
What does the cap stage consist of?
Dental lamina with a mesenchymal invasion below called the dental papilla.
48
With TNM staging, what is T0?
Carcinoma in situ, still localized and contained within top layers of cells lining oral cavity or oropharynx.
49
What are some symptoms of ankylosis of the TMJ or scar tissue development?
Limited openings and excursive movements, deviation of opening, cross-bites, short ramus height, hyper-eruption of the teeth on opposite side.
50
What is the process of compaction involving cleavage?
Compaction is when the blastomeres that are being cleaved, their outer surface become convex and their inner become concave, it changes their cytoskeleton. This segregates some of the blastomeres to the center of the morula and others to the outside.
51
B what day does the morula does it begin to absorb fluid? And which fluids?
By day 4. The trophoblast express a basally polarized Na/K pump, which pumps sodium into the interor of the morula, and water follows, and as the hydrostatic pressure increases, a large cavity called the blastocyst cavity (blastocoel) forms within the morula.
52
What are the two most common missing teeth?
Maxillary lateral incisors and mandibular 2nd premolars
53
What is the N number and ploidy at the start and end of Mitosis?
In mitosis, a diploid 2N cell replicates its DNA becoming a diploid 4N cell, and undergoes a single division to yield two diploid 2N daughter cells. For Big N, just count the number of chromosomes (or what I like to call chromatids). And the only haploid cells will be at the end of Meiosis I (secondary spermatocytes and secondary oocyts), and the end of Meiosis II (gametes).
54
What does PTH do to the kidney and what does it act on?
PTH stimulates the 1-alpha hydroxylase activity in the kidney, resulting in an increase in 1,25 dihydroxyvitamin D production. It also increases the reabsorption of calcium in the distal renal tubules. It also decreases the reabsorption of phosphorus in the proximal renal tubules.
55
What innervates the third pharyngeal arch?
The glossopharyngeal nerve IX
56
What is the name of the cells that detach as neurulation occurs? And what do they do?
Neural crest cells, and they undergo an epithelial to mesenchymal transformation and migrate to numerous locations in the body. The route they take and where they stop determines what they will be.
57
What is the process of remodeling?
The balance of apposition and resorption, with new bone being formed while old bone being removed. It is seen at the surfaces of bones that are growing by endochondral replacement as well as bones that are formed directly within a connective tissue membrane.
58
What are the epithelial cell rests of Malassez?
When HERS disintegrates with the formation of the PDL, these are their remnants, and can cause future periodontal problems if cystic.
59
What becomes the permanent teeth?
The dental lamina superficial to each primary tooth bud produces a small diverticulum, that migrates and becomes the bud of the permanent tooth.
60
Between what two cavities does the bilaminar disc lay?
Between the amniotic cavity and the blastocyst cavity (blastocoel)
61
What causes a facial cleft?
Complete or partial failure of fusion between any of the five facial swellings. Can be unilateral or bilateral.
62
What did the Journal of Orthodontics study in 1998 say about third molar removal affecting mandibular incisor crowding?
Their removal does not reduce or prevent late incisor crowding.
63
What needs to take place for ameloblasts to form?
As soon as mineralized dentin is formed, cells of the IEE differentiate into the ameloblasts, and begin to secrete enamel prisms.
64
What is aneuploidy?
When a cell contains an incorrect number of chromosomes. Usually happens because of failure to line up at metaphase plate.
65
What happens during Telophase of Mitosis?
The chromosomes assemble in sets at the two poles, they begin to uncoil. A nuclear envelope reforms around each chromosome set, the spindle disappears, and the nucleolus reforms. Nuclear division by mitosis is complete at this point.
66
What is the name of the midline swelling that the second pharyngeal arch develops in developing the tongue?
Copula
67
What changes with growth with mineralized tissues?
Hyperplasia, hypertrophy, and secretion of extracellular material can only occur on the surface, not within the mineralized mass. Direct addition of new bone occurs through the activity of cells in the periosteum, and is called direct or surface apposition of bone.
68
What is though to be the most common cause of congenital mental retardation in the western world?
Alcohol
69
What is the end result of Meiosis?
Produces four mature gametes (meiocytes) containing 23 chromosomes (one of each pair) in each cell and are said to be haploid 1N.
70
Does more bone deposition occur on the sphenoid or occipital part of the spheno-occipital synchondrosis?
Occipital
71
What is the Bolton discrepancy?
It is when the tooth size ratio of the maxillary and mandibular teeth will not accommodate a proper occlusal relationship. Common with Kinefelter syndrome.
72
What are the characteristics associated with myelomeningoceles?
Most serious type of Spina Bifida, with this, a sack of fluid comes through the opening in the baby's back, and in this sack is part of the spinal cord and nerves.
73
Which cells secrete calcitonin? And when?
Thyroid gland parafollicular cells, also called C cells. Extra calcium in blood elicits the C cells to release Calcitonin, and calcitonin reduces blood calcium by inhibiting the activity of osteoclasts, and by decreasing the re-absorption of calcium in the kidneys, which leads to lower blood calcium levels.
74
What needs to happen for amelogenesis and dentinogenesis to occur?
A message is sent from the newly differentiated odontoblasts to the IEE, causing the epithelial cells to turn into active secretory ameloblasts, and dentinogenesis is in turn dependent on signals from the differentiating IEE in order for the dentinogenesis process to continue.
75
What innervates the maxillary and mandibular processes of the first arch?
The maxillary and mandibular branches of the trigeminal nerve V
76
What is intramembranous ossification?
It is the embryonic development of flat bones from the embryonic tissue called the mesenchyme.
77
At what plaque pH can remineralization start to occur?
Above 5.5. Above this pH, interbacterial plaque fluid and saliva return to being saturated and then supersaturated, with respect to hydroxyapatite.
78
What is the bilaminar disc made up of?
An epiblast (primary ectoderm) and a hypoblast (primary endoderm)
79
Why don't ploidy and N number always coincide?
Because each chromosome contains one or two molecules of DNA at different stages of the cell cycle (whether mitotic or meiotic)
80
Around day 11-13, what is the name of the region that begins to anastamose with maternal capillaries and become filled with blood?
The cytrotrophoblastic lacunae
81
With TNM staging, what is N1?
The cancer has spread to one lymph node on the same side of the head or neck as the primary tumor, and the lymph node is smaller than 3 cm across.
82
What nerve innervates all of the small salivary glands in the insides of the cheeks, lips, and hard palate, above the level of the oral fissure?
Greater petrosal branch of the Facial nerve - CN VII
83
What is the name of the daughter cells that they zygote is divided up into during cleavage? And what is the name of the 32-cell stage?
Blastomeres. Morula.
84
What is the articular cartilage on the mandible?
It is found on the condyle and is part of the condylar cartilage that isn't converted to bone.
85
What is the nasolacrimal duct?
When ectoderm at the floor of the nasolacrimal groove groove invaginates into the underlying mesenchyme, it forms a tube called the nasolacrimal duct.
86
What gives rise to the primary palate?
The floor of the nasal cavity is formed by a posterior extension of the intermaxillary process called the primary palate.
87
From where does the maxilla initially form?
From a center of mesenchymal condensation in the maxillary process
88
What are the aortic arches?
They are a series of six paired embryological vascular structures which give rise to several major arteries.
89
What has cleft lip been attributed to?
Underdevelopment of the mesenchyme of the maxillary swelling, which results in inadequate contact of the maxillary swelling with the intermaxillary process.
90
What is the name of the process of cell migration, invagination, and ingress that occurs around the beginning of week 3?
Gastrulation
91
What is the most common feature of Turner syndrome?
Short stature, and you can usually tell by age 5. Most Turners have normal intelligence.
92
At what pH can damage start happening to fluoroapatite structures?
4.5
93
What is holoprosencephaly?
HPE is a birth defect of the brain, which effects the development of midline facial features, including closely space eyes, microcephaly, cleft lip, cleft palate. It is caused by failure of the prosencephalon (forebrain) to divide into the doubles lobes of the cerebral hemisphere. It ranges from mild to severe. Sever cases only have one nostril, one joined eye, triangular skull. Mutations in the gene encoding the sonic hedgehog protein, which is involved in the development of the CNS, can cause holoprosencephaly. Also, toxins such as alcohol can cause it.
94
At what age does the condylar growth rate peak? And at what age is it complete?
12 to 14 years old, usually by age 20.
95
By what type of ossification do the maxilla, zyogmatic, and temporal bones form?
Intramembranous ossification
96
What is cleidocranial dysplasia?
It is a skeletal dysplasia with delayed closure of the cranial sutures, hypoplastic clavicles, and multiple dental problems. Supernumerary teeth, short stature, extra set of adult teeth, wide-open fontanelles, narrow sloping shoulders, brachydactyly, wide-open metopic suture in front.
97
What is the neural plate?
It appears as a thickening of the ectoderm on either side of the midline, cranial to the primitive node.
98
What is the name of the membrane that the hypoblast produces that helps form the definitive yolk sac?
It is called the endodermal lining of the definitive yolk sac. And remember that the hypoblast also helps form the extraembryonic endoderm, that turns into Heuser's membrane, which then surrounds the newly formed primary yolk sac.
99
What three main things is bone made up of?
1. Collagen2. Calcium-phosphate mineral complexes 3. Bone cells (osteoclasts, osteoblasts, osteocytes)
100
Which way do the enamel rods face?
Their heads face the cusp tip and the tails face the cervical margin. Each rod is about 1 to 3 mm in length.
101
What happens during Meiosis I - Anaphase I and Telophase I?
In anaphase I, homologous chromosomes separate by moving to separate poles. The cell then proceeds through telophase I, with one double-stranded chromosome of each homologous pair distributed to each daughter cell, the cell then undergoes cytokinesis and the cell divides. Each of the two daughter cells is now Haploid 2N, with half the number of chromosomes per nucleus.
102
What nerve supplies the motor component of the tongue? What is the exception?
CN XII-Hypoglossal nerve, except for the palatoglossus muscle, which is supplied by the pharyngeal branch of the CN X-Vagus nerve.
103
What are the two kinds of chromatin?
Euchromatin and Heterochromatin
104
Where does the center of ossification of the maxilla appear?
It appears in the angle between the anterosuperior alveolar nerve and the inferior orbital nerve.
105
With TNM staging, what is T4a and T4b?
T4a is when the tumor is growing into nearby structures, at this stage it is called a moderately advance local disease.T4b is when the tumor has grown through nearby structures and into deeper areas. At this stage it is called a very advanced local disease.
106
On what day of human development is the notochordal process complete?
Day 20
107
What do polar microtubules do?
They meet in the middle and overlap for a second and attach to each other. The polar and aster stabilize mitosis the most.
108
What packages chromosomes into the condensed structure called chromatin?
Histone proteins
109
What is the name of the layer that the hypoblast is replaced by when the ingressing epiblast cells invade and displace their cells?
The definitive endoderm
110
What is an NTD?
Neural tube defect
111
What is growth of the cranial base primarily the result of?
The endochondral growth and bony replacement at the synchondroses, which have independent growth potential but are perhaps also influenced by growth of the brain.
112
What nerve supplies sensory to the parotid gland?
The auriculotemporal nerve of the mandibular branch of the trigemincal nerve - CN V.
113
What type of sperm are constantly undergoing mitosis in the testes so that the number of them doesn't decrease
Spermatogonia. They progress through the seminiferous epithelium supported by Sertoli cells and undergo the two meiotic divisions which give rise to four future-spermatazoa, with each containing half the normal human genetic content, which can then combine with an oocyte to form a diploid zygote.
114
In what direction does the notochordal plate form from the hollow notochordal process fusing with the underlying endoderm?
In a caudal to cranial direction
115
What does the parotid gland develop from?
A groove-like invagination of ectoderm that forms in the crease between the maxillary and mandibular swellings during week six, the groove turns into a tubular duct which sinks into the underlying mesenchyme toward the ear, then later on is transferred to the inner surface of the cheek, and the opposite end of the tube becomes the parotid gland, and the tube becomes the parotid duct. The submandibular and sublingual glands develop similarly, from invaginations of the endoderm in the floor of the oral cavity and in the paralingual sulci on either side of the tongue, respectively.
116
What is heterochromatin?
It is the condensed chromatin that is folded, tightly coiled like a telephone cord, which allows the cell's DNA to be packed into the nucleus
117
What do cranial base synchondroses serve as and which one has particular importance because of its late ossification and important contribution to post-natal cranial base growth?
They serve as growth centers of the craniofacial skeleton, and the spheno-occipital synchondrosis is very important. The inter-sphenoid and spheno-ethmoid synchondroses are typically stable and show very little growth after 7 years of age.
118
What is the caudal eminence?
As gastrulation proceeds the primitive streak regresses cranially to caudally and by day 26, so during week 4, it leaves a caudal midline mass of mesoderm behind called the caudal eminence.
119
What are the three secondary cartilages that develop between the 10th and 14th week?
1. Condylar cartilage 2. Coronoid cartilage 3. Symphyseal cartilage
120
Not all skeletal cartilage acts the same when transplanted. True or False?
True. If a piece of epiphyseal plate (a growth center) of a long bone is transplanted, it will continue to grow in a new location or in culture. The same applies for transplanting the nasal septum (a growth center). However, little or no growth of the mandibular condylar cartilage (a growth site) was seen after transplantation.
121
What does the mesenchyme that covers the dorsal side of the neural tube end up giving rise to?
The vertebral arches and skull.
122
What are the four growth areas of the craniofacial complex?
1. Cranial vault (the bones that cover the upper and outer surface of the brain) 2. Cranial base (the bony floor under the brain, which also is the dividing line between the cranium and the face) 3. Nasomaxillary complex (Nose, maxilla, and associated small bones) 4. Mandible
123
From what three pairs of cartilaginous precursors does the chondocranium develop from?
1. Ethmoid prechordal cartilage2. Sphenoid hypophyseal cartilage3. Occipital parachordal cartilage
124
What ploidy are mature gametes like spermatozoa and a definitive oocyte?
They are haploid
125
How many pairs of autosomes vs sex chromosomes in each nucleus?
22 pairs of autosomes and 1 pair of sex chromosomes (XX or XY)
126
What happens to most of the anterior surface of the maxilla has it grows downward and forward?
It is remodeled and bone is removed.
127
What will be the blood calcium, phosphorus and renal calcium and phosphorus levels in Hyperparathyroidism (high PTH)?
High calcium, low phosphorus, and high urinary calcium and phosphorus.
128
What is the process of cleavage?
Subdividing the zygote without increasing its size.
129
What forms the intermaxillary process?
By the end of week 7, the inferior tips of the medial nasal processes expand laterally and inferiorly and fuse to form the intermaxillary process.
130
What does the hypoblast form when it sends out a proliferation of cells that lines the cytotrophoblast by day 9? And the part that lines the former blastocyst cavity, what is the name of this membrane?
It forms the extraembryonic endoderm. Heuser's membrane. And at the same time of all this, the extraembryonic mesoderm forms
131
What becomes the tooth pulp?
The inner mesenchyme of the dental papilla.
132
What is Apert's syndrome?
Caused by nucleotide alterations resulting in amin-acid substitutions, leading to mutation in FDFR2 gene located on chromosome 10. Craniosynostosis and symmetric syndactyly of the extremities are hallmarks. Wide-set eyes, mid-face hypoplasia, class III occlusion.
133
What is Crouzon's syndrome?
Premature fusion of certain skull bones (craniosynostosis), and this leads to wide-set bulging eyes from underdevelopment of midface, vision problems, eyes that do not point in same direction (strabismus), beaked nose, underdeveloped jaw. This is the most frequent occurring member of Craniosynostosis syndromes. It arises because of prenatal fusion of superior and posterior sutures of the maxilla along wall of orbit, which produces distortions. Also caused by mutation in FGFR2 gene, which provides instruction for making a protein called fibroblast growth factor receptor 2.
134
What innervates the sixth pharyngeal arch?
The recurrent laryngeal branch of vagus nerve X
135
Does the embryo grow faster in length or in width?
In length, cranially and caudally.
136
Around the TMJ, two clefts appear in the mesenchyme producing the upper and lower joint cavities, but what does the mesenchyme surrounding the developing joint become?
The intra articular disk
137
What is the nasolacrimal groove or furrow?
It is a groove between the lateral nasal process and the adjacent maxillary swelling.
138
During what stage does amelogenesis occur?
During the bell stage
139
What has now blanketed the entire (except for a small region at the abembryonic pole) implanted blastocyst by day 9?
The syncytiotrophoblast
140
At what age do most kids born with cleft lip or palate have surgery to repair them?
Within the first 12-18 months of life
141
What does the third arch cartilage, which originates from neural crest cells, give rise to?
The lower rim of the hyoid bone and the greater horn of the hyoid
142
What does Diploid or 2n mean?
When a cells chromosomal number consists of two sets of chromosomes (one from mother and one from father), it is referred to as Diploid and can be denoted as 2n
143
How many chromosomes are formed during Telophase II?
Four haploid nuclei (containing chromosomes with single chromatids) are formed in Telophase II. And these four cells are not identical because of the genetic diversity that took place in Meiosis I.
144
How does the remodeling of the palatal vault differ from the remodeling of the maxilla?
The palatal vault is carried downward and forward along with the rest of the maxilla but at the same time, bone is removed on the nasal side and added on the oral side, thus creating an additional downward and forward movement of the palate.
145
What does the third pharyngeal pouch develop into?
Dorsal portion of third pharyngeal pouch develops into the inferior parathyroid gland, while ventral portion develops into the thymus
146
What are the characteristics associated with meningoceles?
With this type, a sack of fluid comes through an opening in the baby's back, but the spinal cord is not in this sac, and usually little or no nerve damage.
147
What is the name for the two identical chromosomes resulting from DNA replication?
Sister chromatids
148
What generates bioelectric charges in bone as it pertains to theories of growth?
Distortions of the collagen crystals in bone cause a minute deformation of the bone matrix due to mechanic strain, generating bioelectric signals or charges in the immediate area of deformation. These altered electric potentials appear to relate either directly or indirectly to the triggering of osteoblastic and osteoclastic responses.
149
What innervates the fourth pharyngeal arch?
The superior laryngeal branch of vagus nerve X
150
What do the neural crest cells that migrate to lower regions of the facial area help form?
Aorta, pulmonary artery, aortic arch, etc. This is why many syndromic patients have heart defects.
151
During what week of embryonic development does the embryoblast split into two layers forming a bilaminar disc?
Second week
152
What are the three layers of the enamel organ?
1. IEE2. Middle enamel reticulum3. OEE
153
What is the name of the structure that the thyroid gland originates from?
It is the foramen cecum, and it is found on the developing tongue
154
Does more bone deposition occur on the ethmoid or sphenoid part of the spheno-ethmoidal synchondrosis?
Ethmoid
155
In which direction does closure of the neural groove (fusion of the neural folds) take place?
It begins at the occipitocervical region and proceeds both cranially and caudally.
156
What does the ultimobrachial body do?
The ultrimobranchial body releases signaling factors to induce migration and differentiation of nearby neural crest cells into the parafollicular cells of the thyroid gland.
157
What structure appears at the beginning of the third week? And what three structures does it contain?
The primitive streak (faint midline structure), which contains the primitive groove, the primitive pit, and the primitive node.
158
What innervates the taste component of the anterior 2/3 of the tongue?
It is supplied by the chorda tympani branch of CN VII-facial nerve, which innervates all taste buds except the circumvallate papillae.
159
At what stage is the embryo called blastocyst?
When the morula has absorbed fluid and formed a blastocoel along with the inner cell mass.
160
By the end of what week do all five facial swellings appear by?
End of the fourth week
161
What is the most important trimester for normal embryological development?
First, 12 weeks.
162
What resembles Mitosis more, Meiosis I or Meiosis II?
Meiosis II
163
What did the Gilhuus-Moe and Lund study demonstrate regarding a mandibular condyle fracture?
That in a child, there was an 80% chance that the condylar process would regenerate to approximately its original size. The condyle regenerates directly from periosteum at the fracture site, because all of the original bone and cartilage resorb.
164
The maxilla grows more and later than the mandible. True or False?
False. Just think that the maxilla is closer to the brain, which also grows slower.
165
What percentage of conceptions result in spontaneous abortion because of chromosomal abnormalities?
40-50%
166
Where are motor proteins found and how do they move along?
They are found on the spindle microtubules and utilize ATP hydrolysis to move along. They are required for spindle formation, chromosome alignment, and segregation, and are required for the cell to avoid aneuploidy, a hallmark of cancer.
167
What is the concept of pattern?
The change of proportional relationships over time
168
What are the two most common types of facial clefts?
Cleft lip and cleft palate
169
When the intraembryonic mesoderm cells migrate LATERALLY, what do they organize into and form, and what does this end up giving rise to?
They form the somitomeres (somites), which give rise to vertebral columns, skeletal musculature, and dermis.
170
What is found at the outer end of each epiphyseal plate?
A zone of actively dividing cartilage cells. As long as the rate at which cartilage cells proliferate is equal to or greater than the rate at which they mature, growth will continue.
171
What is the name of the layer that is formed when some of the epiblast cells migrate through the primitive streak into the space between the epiblast and definitive endoderm?
The intraembryonic mesoderm
172
What is the difference between the primitive and definitive choana?
Once the nasal septum forms, the nasal passages open into the pharynx behind the secondary palate through the primitive choana, but is now called the definitive choana.
173
What causes Down Syndrome?
Embryos formed by fusion of a gamete with two copies of chromosome 21 and with a normal gamete results in trisomy 21. 95% of all Down Syndrome cases are caused this way.
174
Is a suture a growth site or growth center?
Growth site
175
How does growth of the mandible differ from growth of the maxilla?
In contrast to the maxilla, both endochondral and periosteal activity are important in growth of the mandible, and displacement created by growth of the cranial base plays a negligible role.
176
Normally, is most of the calcium that enters glomerular filtrate reabsorbed back into the blood, or excreted?
Reabsorbed back into blood to preserve blood calcium.
177
What causes anencephaly?
It happens if the upper part of the neural tube does not close all the way, and babies are born without front part of brain, cerebrum, or remaining parts are not covered by bone or skin.
178
What forms the cementoblasts?
The inner cels of the dental sac/follicle differentiate into the cementoblasts.
179
What is a teratogen?
Chemical and other agents capable of producing embryologic defects if given at a critical time. At high levels, can cause death.
180
When do the ameloblasts lose their ruffled borders?
As enamel maturation nears completion.
181
During what phase of the cell cycle does DNA replication take place, and how long does it take?
Occurs during S phase (S for synthesis) and takes about 10-12 hours, and makes up half of the cell-cycle time in a cell. Whereas the M phase for chromosome segregation and cell division only takes an hour.
182
During what month is there an in-growth of blood vascular elements into various points of the chondocranium?
Fourth month. These areas become centers of ossification, at which cartilage is transformed into bone (endochondral ossification) and islands of bone appear in the sea of surrounding cartilage.
183
What four things is Tetralogy of Fallot composed of?
1. Pulmonary stenosis2. Right ventricular hypertrophy3. Overriding aorta (is huge and arises from both left and right instead of just left ventricle.4. Ventricular septal defect (VSD)
184
What type is 3-4% of all cases of Trisomy 21 due to?
Robertsonian Translocation. Which is when two breaks occur in separate chromosomes, usually 14th and 21st. So there is triplication of the 21st chromosome material. Partial trisomy 21 is when these people have only triplication of part of the 21st instead of the whole chromosome, and this is inherited.
185
What is translocation?
When a copy of chromosome 21 in a developing gamete becomes attached to the end of another chromosome, suchas chromosome 14, during the first or second division of meiosis. This can also cause Down Syndrome.
186
When do most gene mutations occur?
After you're born, and they are not inherited. Smoking, radiation, viruses, carcinogens, obesity, hormones, and a lack of exercise can all cause gene mutations. And these gene mutations combine and can make us more likely than others to develop a specific type of cancer.
187
What is the NAM device?
It is a NasoAlveolar Molding device, and can be elaborate or passive. it consists of an intraoral acrylic plate held in place with extraoral elastics and tape. And in later phases, wire outriggers are added that apply protracting forces to the vestibule of the nares.
188
What is the lateral cervical sinus?
It is when the second pharyngeal arch overgrows clefts 2, 3, and 4 and fuses caudally with the cardiac eminence to form this transient ectoderm-lined structure, which normally just disappears. However, it occasionally persists on one or both sides in the form of a cervical cyst, just anterior to sternocleidomastoid muscle.
189
What is the name glycoprotein layer that surround a zygote?
The zona pellucida, and it surrounds the zygotes plasma membrane. It plays a role in zygote development, protection, fertilization, and preventing premature implantation.
190
What are the main errors that cause cleft palate?
Inadequate growth of the palatine shelves, failure of shelves to elevate at correct time, excessively wide head, failure of shelves to fuse, secondary rupture after fusion.
191
With Pierre Robin syndrome, does the relationship between the upper and lower teeth improve or get worse as the child grows?
It improves.
192
Where does the actual growth of the mandible occur?
The chin is translated downward and forward as the actual growth occurs at the mandibular condyle and along the posterior surface of the ramus.
193
What two structures is enamel mostly made up of?
Hydroxyapatite and fluoroapatite
194
What type of bone forms the roof of the skull and the viscerocranium, which supports the pharyngeal arches and their derivatives?
Membranous bone
195
Where do the odontoblasts come from, and during what stage?
During the bell stage, the outermost cells of the dental papilla become organized into a layer just adjacent to the inner enamel epithelium, and these cells become the odontoblasts.
196
How much of the total body does the head take up at the third month of intrauterine development?
Almost 50%
197
What is distraction osteogenesis?
A technique that uses a device to pull the midface slowly forward after surgery and move it further forward than a single surgery can.
198
What is the name of the cartilage of the second arch?
Reichert's cartilage
199
What is the largest secondary cartilage associated with the mandible? And what does it give rise to?
Condylar cartilage, gives rise (through endochondral ossification) to the condyle head and neck of the mandible.
200
What is endochondral ossification?
The bones of the chondrocarnium are preformed in cartilage and ossify by the process of endochondral ossification.
201
What is the embryoblast the main source of?
The embryo itself, and is also called the inner cell mass
202
What is the chondrocarnium?
It is the cartilaginous portion of the cranium that represents a continuous plate of cartilage. Cartilage is nearly avascular tissue that is thin.
203
What does the first pharyngeal pouch develop into?
The eustachian tube and middle ear cavity
204
What did James Scott say about the Nasal Septum Cartilage?
He reasoned that the cartilaginous nasal septum has features and occupies a strategic position that answers the question of what motor causes the midface to displace anteriorly and inferiorly as it grows in size. If the sutures of the maxilla served as reactive areas, they would respond to nasal cartilage growth by forming new bone when the sutures were pulled apart by forces for the growing nasal septum.
205
The growth of the cranium occurs almost entirely in response to the growth of which structure?
In response to the growth of the brain.
206
What is the definition of development?
An increasing degree of organization, complexity, or specialization.
207
What is the definition of growth?
An increase in size, but it can tend to be more linked to change than anything else.
208
What regulates parathyroid hormone and what does PTH help control?
It is regulated by the four parathyroid glands, and PTH helps control calcium, phosphorus, and vitamin D levels in the blood and bone. PTH increases the amount of calcium in the blood, and helps us avoid hypoparathyroidism, which is a huge symptom of DiGeorge Syndrome. So we get low calcium levels and high phosphorus levels in the blood.
209
What do the outer cells of the dental sac/follicle form?
Alveolar bone formation and the PDL. Fibroblasts from the dental sac secrete collagen, which interacts with fibers on bone and cementum, and occlusion continues to shape these, to form the always changing PDL fibers.
210
What does bilateral coronal synostosis result in?
Prominent frontal bone and flattened occipital.
211
What is the mechanostat as it pertains to theories of growth?
It is a model describing bone growth and bone loss, and is a refinement of Wolff's law. it says that bone growth and bone loss is stimulated by the local mechanical elastic deformation of bone. The reason for this elastic deformation of bone is because of the peak forces caused by muscles. Bone mass, bone geometry and bone is adapted according to the every-day usage and needs. Because of this control loop, there is a linear relationship in the healthy body between muscle cross sectional area and the bone cross sectional area. These relations are super important for bone loss situations like osteoporosis, since an adapted training utilizing the needed maximum forces on the bone can be used to stimulate bone growth and prevent or help to minimize bone loss.
212
What is a common side effect cleft palates?
Buildup behind the eardrum, which affects hearing.
213
What is the difference between neural plate, neural grooves, neural fold, neural tube, neural canal, and neural crest cells?
The neural plate bends and forms neural folds at the lateral edges, consisting of neuroepithelium and adjacent surface ectoderm. The two elevated folds form the neural groove in the middle, overlying the notochord. And when the two neural folds elevate, rotate, and fuse, this forms the neural tube and neural canal (within the neural tube). And forming in the interface between these epithelial layers are the neural crest cells.
214
What does the first arch cartilage give rise to?
Two ossicles of the middle ear (incus and malleus) and other bony elements
215
What is the name of the midline swelling that the third and fourth pharyngeal arches give rise to that overgrows the copula on the tongue?
Hypopharyngeal eminence
216
What forms the nasal fin?
The floor and posterior wall of the nasal sac proliferate to form a thickened, plate like fin of ectoderm separating the nasal sac from the oral cavity called the nasal fin.
217
Is the thyroid gland ectodermal, mesodermal, or endodermal in origin?
It appears in the late fourth week as a small solid mass of endoderm proliferating at apex of foramen cecum. But remember that the thyroid gland is not derived from any of the pharyngeal arches. It arises from a midline thyroid diverticulum that forms from the endoderm in the floor of the pharynx just caudal to the first pharyngeal arch. And these endoderm cells differentiate into the follicular cells of the thyroid gland.
218
What gives rise to the parafollicular cells of the thyroid?
The neural crest cells of the ultimobranchial body migrate into the gland and give rise to the parafollicular cells of the thyroid.
219
What is the centrosome?
It is an organelle located near the nucleus in the cytoplasm that divides and migrates to opposite poles of the cell during mitosis. It consists of two centrioles, oriented at right angles and embedded in a mass of amorphous material containing more than 100 different proteins. Just before mitosis, the two centrosomes move apart until they are on opposite sides of the nucleus.
220
What is the definition of Ploidy?
Refers to the number of full, single set(s) of chromosomes in a cells nucleus, not including duplicated DNA set(s) in the nucleus.
221
What is Cytokinesis?
It is the division of cytoplasm, and is usually in progress before nuclear division is complete. In animal cells, cytokinesis involves formation of a cleave furrow.
222
What innervates the second pharyngeal arch?
The facial nerve VII
223
What does the oval nasal pit from the nasal placode help form?
It helps divide the nasal placode into a lateral nasal process and a medial nasal process, and happens during week 6.
224
Are girls or boy more likely to have encephaloceles in front or back of skull, respectively?
Girls = backBoys = frontNorth America = backSoutheast Asia = front
225
What is osteogenesis imperfecta?
May be seen alone or with dentinogenesis imperfecta, and it is a genetic disorder where bones break for no apparent cause, and is caused by mutations in one of several collagen producing genes, COL1A1 and COL1A2, creating a loss in the production of collagen. The teeth are discolored and show bulbous crowns and small pulp chambers.
226
Bone is always formed as a primary tissue. True or False?
False. It always replaces a preexisting support tissue, it is never formed as a primary tissue.
227
What is HERS?
At the base of the tooth crown, the confluence of the inner and outer enamel epithelium elongate to form a bilayered Hertwig's epithelial root sheath. It is an extension formed by the free edge of the enamel organ on the developing tooth which goes beyond the DEJ and molds the dental papilla to form the root of the tooth. It also initiates formation of dentin in the root of a tooth by causing the differentiation of odontoblasts from the mesenchyme of the dental papilla.
228
What ends up forming the posterior one third of the tongue?
Hypopharyngeal eminence
229
What are the structures that each arch has?
Nerve, cartilage, artery, pharyngeal pouch, pharyngeal cleft, mesenchymal core of somatic mesoderm and neural crest mesenchyme, pharyngeal membrane made up of endoderm and ectoderm.
230
Does growth occur at sutures, condyles, and synchondroses by pushing the bones apart?
It is clear now that sutures and the periosteal tissues more generally are not primary determinants of craniofacial growth. If the area of a suture between two facial bones is transplanted to another location, the tissue does not continue to grow. And it has been shown that growth at the sutures does not respond to outside influences (craniosynostosis, intermaxillary sutural expansion).
231
What are bivalent chromosomes?
They are the homologous chromosomes that are pair up during Prophase I at their centromeres, and these are said to be in synapsis. And it is during synapsis that crossovers can occur between the paired bivalents, leading to genetic recombination.
232
What happens to pharyngeal clefts 2, 3, and 4?
They are overgrown by expansion of the 2nd pharyngeal arch and are usually obliterated
233
How does the growth of the maxilla and its associated structures primarily take place?
Occurs from a combination of growth at sutures and through direct remodeling of the surfaces of the bone. The maxilla is translated downward and forward as the face grows, and new bone fills in at the sutures. The extent to which growth of cartilage of the nasal septum leads to translation of the maxilla remains unknown, but both the surrounding soft tissues and the nasal septum probably contribute to the forward positioning of the maxilla.
234
What is the oronasal membrane?
It separates the nasal sac from the oral cavity, similar to the nasal fin, but forms when vacuoles develop in the nasal fin, fuse with the nasal sac, enlarging it and thinning the fin to a thin membrane called the oronasal membrane.
235
During what weeks is the basic morphology of the face created by?
During weeks 4 through 10
236
What are the five principle stages in craniofacial development?
1. Germ layer formation2. Neural tube formation and initial formation of the oropharynx3. Origin, migration, and interactions of cell population, especially neural crest cells4. Formation of organ systems, especially the pharyngeal arches and the primary palate and secondary palates5. Final differentiation of tissues
237
What are the two main possible reasons why there is such a large range and variability of symptoms and diseases with down syndrome people?
One possible reason for the variability is due to mosaicism and the difference in the genes that are triplicated. Another reason is because of gene penetrance.
238
What are the two groups of cells that the cleaving embryo first divides into?
The trophoblast and the embryoblast
239
What is mosaicism?
It denotes the presence of two or more populations of cells with different genotypes in one individual who has developed from a single fertilized egg. The extra chromosome 21 is lost from a subset of cells during cleavage sometimes, resulting in an embryo that develops as a mosaic of normal and trisomy 21 cells called mosaicism. So it is a condition in which cells within the same person have a different genetic makeup. They may show down syndrome.
240
What does the developing thyroid gland travel through?
The thyroglossal duct, and it keeps going and reaches its position just inferior to the cricoid cartilage by the seventh week, so it takes about 2-3 weeks.
241
What is cleft palate?
Results from failure of the two palatine shelves to fuse with each other along the midline.
242
With TNM staging, what is N3?
The cancer has spread to a lymph node that measures more than 6 cm across.
243
What is amelogenesis imperfecta?
It can be inherited as an x-linked autosomal recessive or AD condition. Mutations in AMELX, ENAM, and MMP20 genes cause it. These genes provide instructions for making proteins essential to tooth development.
244
Artificial saliva can also help stimulate salivary gland production. True or False?
False. Just helps lubricate and replace moisture lost.
245
What is a LeFort III Osteotomy?
It is a surgery that moves the middle portion of the face forward and aligns the upper and lower jaw to create a larger airway, and is often done in childhood with kids who have craniosynostosis.
246
What is the name of an undifferentiated germ cell that gives rise to oocytes?
Oogonia
247
What is the name of the series of mitotic cell divisions that the Zygote undergoes as it travels down the oviduct with 24 hours after fusion?
Cleavage
248
What is the name of the process during the fourth week of folding along the neural groove that converts the neural plate into a hollow neural tube, which sinks into the body wall and begins to differentiate into the brain and spinal cord?
Neurulation
249
What does metopic synostosis result in?
A trigone-shaped skull with protrusion of the parieto-occipital region.
250
What is the trophoblast the main source of?
The placenta and the associated membranes
251
What is the secondary oocyte?
It is one of the four cells from Meiosis that gets the nutrients and is the only one to survive. The other ones are polar bodies and die quickly.
252
The growth of the chondrocranium contributes directly to the formation of the maxillary bone. True or False?
False, it does not.
253
What is the skeleton of the head and pharynx made up of in vertebrates?
Chondrocranium
254
When does the migration of neural crest cells conclude?
During the fourth week
255
What innervates both the sensory and taste coponents of the posterior 1/3 of the tongue? What are the exceptions?
CN IX, glossopharyngeal nerve. Two two exceptions are that the sensory branch of CN IX-glossopharyngeal nerve supplies the circumvallate papillae, and sensory fibers of the superior laryngeal branch of CN X-Vagus nerve innervates a small mucosa region on the dorsal side of the posterior tongue.
256
What structure is just cranial to the oropharyngeal membrane, and what will it give rise to?
The cardiogenic area (it is horseshoe shaped), the heart.
257
Which arteries does the fourth pharyngeal arch give rise to?
Arch of the aorta, right subclavian artery and original pulmonary arteries
258
What is another name for the small areas of cartilage that represent the old chondocranium?
Synchondroses
259
What is intrauterine molding?
It is an arm pressed against the fetal face which can cause midface deficiency, a fetus head flexed tightly against the chest prevents the mandible from growing forward normally, whatever it is, it is caused by pressure against the developing face prenatally.
260
What is Wolff's law as it pertains to theories of growth?
It states that bone in a healthy person or animal will adapt to the loads under which it is placed, so if loading on a particular bone increases, the bone will remodel itself over time to become stronger to resist that sort of loading.
261
What roles does calcium have?
Blood clotting, conduction of nerve impulses, salivary function, contraction and relaxation of muscles and blood vessels, regulation of body fluids, including hormones and enzymes.
262
What is the definition of the N number?
Refers to the number of full, single set(s) of chromosomes including duplicated DNA sets in the nucleus.
263
Where do the buds of the permanent molars come from?
They arise during postnatal life from a pencil-like extension of the dental lamina that burrows back into the posterior jaw from the primary second molar tooth bud.
264
What is the theory of growth involving sutures, condyles, and synchondroses?
This theory was a major thrust at the idea of master growth centers which control development, and states that the mechanism for translation of the maxilla was considered to be the result of pressure created by growth of the sutures so that the maxilla was literally pushed downward and forward. If this theory is correct, growth at the sutures should occur largely independently of the environment and it would not be possible to change the expression of growth at the sutures very much.
265
Chronologic age is often not a good indicator of the individuals growth status. True or False?
True
266
What gives rise to the laryngeal cartilages?
The lateral plate mesoderm of the fourth and sixth pharyngeal arches
267
What is the central shaft of a long bone called?
Diaphysis
268
What kind of learning/behavioral disorders/autoimmune disorders do people with DiGeorge syndrome have?
ADHD, autism, depression, anxiety, rheumatoid arthritis, Grave's disease, poor vision, poor kidney function, short stature.
269
How common is cleft lip and cleft palate?
They can occur in about 1 or 2 of every 1,000 in the US. More common in Asian, Latino, or Native American descent.
270
With TNM staging, what is M0 and M1?
M0 is no metastasis and M1 means that the oral cancer has spread to distant sites outside the head and neck region.
271
What is the dental sac?
It is the mesenchyme surrounding both the dental lamina and dental papilla.
272
What is a LeFort II fracture?
It is a pyramidal fracture that passes through the nasal bridge medially extending laterally through the frontal process of the maxilla, lacrimal bones, orbital floor, anterior wall of maxillary sinus, passing below the zygoma, and transecting the pterygomaxillary junction to interrupt the pterygoid plates. It results in a pyramid-shaped mobile bone fragment that includes nasal complex and entire maxilla, including the hard palate.
273
How is genetic diversity achieved during Meiosis I?
Through crossing over and through independent assortment, the random positioning of homologous chromosomes.
274
What is the timeline for addressing an infant with cleft lip and cleft palate?
3 months - repair of cleft lip6 months - pre-surgical orthopedics9 months - speech therapy begins9-12 months - repair of cleft palateAge 1 -7 - orthodontic treatmentAge 7-8 - alveolar bone graft8+ - orthodontic treatment
275
Phosphorus has no direct stimulatory effect on the parathryoid glands. True or False?
False. It has been shown recently to have an effect.
276
What two things is a tooth bud composed of?
Dental lamina and mesenchymal concentration below.
277
What is nondisjunction?
When two copies of chromosome 21 fail to separate during the first or second meiotic division, which results in one cell having 24 chromosomes and the other having 22 chromosomes. More common in gametogenesis of older females.
278
What is the name of the mass of cytoplasm which helps begin the implantation of the blastocyst into the uterine wall?
Syncytiotrophoblast. It is formed when the blastocyst contacts the uterine endometrium and the trophoblasts are induced at the embryonic pole to proliferate, and they lose their cell membranes, and become this.
279
What does the chondrocranium form?
The skull base and supports the brain, olfactory organs, eyes, and inner ears.
280
What is fetal alcohol syndrome?
FAS is a mild form of holoprosencephaly. Each year between 5,000 to 12,000 American babies are born with it. They may grow slower than other children, have facial abnormalities, mental retardation. Facial features include small eyes with drooping upper eyelid, short upturned nose, flattened cheek, small jaw, thin upper lip, flattened philtrum. FAS is due to deficiencies of midline tissue of the neural plate very early in embryonic development.
281
What are the main phases of the cell cycle?
M - MitosisG1 - GrowthS - DNA replicationG2 - Growth
282
What is spina bifida?
Is a set of malformations of the spinal cord caused by failure of closure of the neural tube and lack of fusion of the vertebral arches, soft tissues, and skin that covers the back. Usually seen in the lumbosacral area, but can involve the entire spinal cord. Can cause physical and intellectual disabilities, depending on the size and location of the opening in the spine.
283
With TNM staging, what is T3?
Tumor is larger than 4 cm across
284
What is a homolog?
The 46 chromosomes in the nucleus of most human cells consist of 23 pairs of homologous chromosomes, or homologs, meaning that each of these pairs is alike, but not necessarily identical.
285
What is Turner Syndrome?
Results when one normal X chromosome is present in a female's cells and the other sex chromosome is missing or structurally altered. Affects development before and after birth. Happens in about 1 in 2500 births. 30% of females with Turner have extra folds on skin of the neck. They also have a low hairline at the back of the neck, have lymphedema of hands and feet, and have early loss of ovarian function.
286
What is gametogenesis?
The development and production of the male and female mature gametes.
287
By what two methods can bone shape be changed with intramembranous ossification?
1. Resorption2. Apposition
288
What are the two types of cementum? Characteristics? Which one forms first?
1. Cellular2. Acellular-Acellular forms first as cementoblasts differentiate from the dental follicular cells, which only reach surface of tooth once HERS is gone. -Cellular cementum develops after most of tooth formation is complete, it forms around fiber bundles of the PDL, and their cementoblasts become trapped in the cementum they produce.
289
What is it called when an encephalocele emerges along with the meninges? Along with ventricular system (CSF)?
Meningoencephalocele, Meningohydroencephalocele
290
What is the center of ossification of the maxillary process closely associated with?
The cartilage of the nasal capsule, which is located on the lateral surface of the nasal capsule at the most anterior part of the chondrocranium.
291
What needs to happen for the notochordal plate to turn into the notochord?
It needs to disengage with the endoderm to form the solid notochord.
292
What does the TMJ develop from?
The mesenchyme lying between the developing mandibular condyle below, and the temporal bone above.
293
Do growth sites contain primary or secondary cartilage?
Secondary cartilage
294
The growth of the chondrocranium contributes to the lengthening of the head and anterior displacement of the maxilla. True or False?
True
295
Which state reports to have among the highest rates of orofacial clefts in the US and internationally?
Utah, also has the highest recorded incidence of cleft lip and palate in the US. The average lifetime medical cost is $100,000.
296
What is the process of dentinogenesis?
It begins with the odontoblasts beginning to secrete the nonmineralized matrix of dentin, predentin, which later calcifies to form dentin.
297
What does the cells of the bilaminar disc develop into?
The embryo proper
298
Does ossification progress from posterior to anterior or anterior to posterior with the chondrocranium?
From posterior to anterior
299
What do aster microtubules do?
They come out from the centrosome and point away from the spindle equator and attach to the cell's cortex. The polar and aster stabilize mitosis the most.
300
What does the somatic mesoderm of the second pharyngeal arch give rise to?
The muscles of facial expression (orbicularis oculi, buccinator, orbicularis oris, etc.), posterior belly of digastric, stapedius, , stylohyoid
301
What are the three stages of amelogenesis?
1. Inductive2. Secretory3. Maturation
302
Where do primordial germ cells migrate to and rest during four and six weeks?
They migrate from the yolk sac to the wall of the gut tube, and then to the dorsal body wall. And it is here where these cells rest on either side of the midline in loose mesenchymal tissue.
303
What are taurodont molars?
Extension of pulp chamber well below the level of alveolar crest and CEJ, pulp floor moves apically, it is caused by failure of Hertwig's root sheath to invaginate at the proper horizontal level. Can really happen with any tooth.
304
Cleft palate and cleft lip are not common in DiGeorge. True or False?
False
305
What is a primordial germ cell?
It is a cell that gives rise to gametes in both males and females and their lineage constitutes the germ line.
306
What happens during inductive stage of amelogenesis?
Dentin is not mineralized, and the IEE has a cuboidal or low columnar appearance, with centralized nuclei and poorly developed Golgi. The IEE cells then elongate and become preameloblasts, but no Tomes process yet. It is at this stage that the ameloblasts send a signal across the DEJ to stimulate dentinogenesis.
307
What is the name of the area between the epiphysis and diaphysis that is made up of uncalcified cartilage?
Epiphyseal plate (growth plate). This is the major center for growth in long bones. While periosteum plays a role in adding thickness and reshapes external contours.
308
How early can a primordial germ cell be identified, and where is it identified?
During the 4th week of gestation, and within the extraembryonic membrane called the yolk sac.
309
What is the centromere?
It is a constriction point which divides the chromosome into two sections or arms. The location of the centromere on each chromosome gives the chromosome its characteristic shape, and can be used to help describe the location of specific genes.
310
By day 12-13, when the extraembryonic mesoderm is split into two layers, what is the name of the cavity that forms in between these layers?
The chorionic cavity, or the extraembryonic coelom.
311
What will the four occipital and first two cervical somitomeres that have differentiated into somites by day 21 from the cranial and caudal portions of the paraxial mesoderm eventually give rise to?
Skeletal muscle, tendons, cartilage, and bone.
312
What is the main force responsible for embryonic folding?
Differential growth of various embryonic structures. The embryonic disc and amnion grow vigorously but the yolk sac hardly grows at all causing the disc to balloon into a cylindrical shape. While the notochord, neural tube, and somites stiffen the dorsal axis.
313
What days do the cranial and caudal ends close by?
Cranial 24 and Caudal 26
314
Are older people more or less likely to meet their vitamin D requirements by sunlight alone?
Less, because their skin pigmentation deteriorates with age, so the conversion of UV light is much less efficient, and they do not spend as much time outdoors.
315
What are the four phases of Mitosis?
PMATProphaseMetaphaseAnaphaseTelophase
316
The mandible in embryonic life develops in the same area as what?
Meckel's cartilage
317
By the end of the second week, what should the developing embryo look like?
The definitive yolk sac and the bilaminar germ disc should be suspended in the chorionic cavity by a thick connecting stalk.
318
What are the three distinct types of microtubule fibers that the mitotic spindle is composed of?
1. Kinetochore2. Polar3. Aster
319
What causes encephaloceles?
It happens early in a woman's pregnancy when part of the developing skull doesn't close completely. It can cause part of baby's brain to stick out of skull. It can be located in base of skull, are of nose sinus and forehead, or around the back of skull. They are rare, 1 in 5000.
320
What forms the ossification center in intramembranous ossification?
Centrally located stem cells within the mesenchyme differentiate into osteoblasts, forming the ossification center.
321
What is the process of kinetochore microtubules during the Mitosis phases?
During prophase, a kinetochore microtubule grows from the centrosome, and by prometaphase, it finds a kinetochore and grabs a sister chromatid from each side. This serves to balance opposing forces, and results in alignment of the chromosomes at the spindle equator during metaphase.
322
What is a mitotic spindle fiber?
As mitosis proceeds, microtubules grow out from each centrosome with their + ends growing toward the metaphase plate. These clusters of microtubules are called mitotic spindle fibers. They all serve to pull and push the sister chromatids apart toward the opposite spindle poles.
323
What is the name of the two membranes on each side of the bilaminar membrane that form during the third week when two faint depressions appear in the ectoderm, one at the cranial, and one at the caudal?
The cranial membrane is called the buccopharyngeal membrane and the caudal membrane is called the cloacal membrane.
324
What layer do all three germ layers derive from during gastrulation?
Epiblast
325
What is the name of the structure that will give rise to the future mouth of the embryo, and where is it located?
The oropharyngeal membrane, and it is located at the thin area located cranial to the neural plate of the embryonic disc.
326
What is the N number and ploidy at the start and end of Meiosis?
In meiosis, a diploid 2N germ cell replicates its DNA becoming diploid 4N cells and undergoes two successive nuclear cell divisions to yield four haploid 1N cells. For Big N, just count the number of chromosomes (or what I like to call chromatids). And the only haploid cells will be at the end of Meiosis I (secondary spermatocytes and secondary oocyts), and the end of Meiosis II (gametes).
327
What is gene penetrance? Complete vs Incomplete?
It refers to the proportion of individuals carrying a particular variant of a gene that also expresses an associated phenotype. Complete means the gene for a trait are expressed in all the population who have the gene. Incomplete means that the genetic trait is expressed in only part of the population, and that appears to be what happens in the variability with trisomy 21. So Down syndrome = incomplete penetrance = variability with patients.
328
What do remnants of Meckel's cartilage transform into?
A portion of the middle ear
329
What is the current thinking regarding the genetic blue print model?
A key factor is that these genetic tissues do not actually govern their own function, but are rather controlled by epigenetic (indirect) influences from other tissue groups and their functional, structural, and developmental input signals.
330
What are the three possibilities for growth that occur in skeletal growth?
1. Hypertrophy2. Hyperplasia (a more prominent feature in all forms of growth)3. Cells secrete extracellular material (which can later mineralize to form bone)
331
What are the three kinds of amelogenesis imperfecta?
1. Hypoplastic - defect in amount of enamel (pitted). Pitted-Has normal thickness, pitted surface, normal hardness. Generalized-reduced thickness, smooth surface, normal hardness2. Hypomaturation - defect in final growth and maturation of enamel crystallities and hypomineralization. Has normal thickness, chipped surface, less hardness, opaque white coloration.3. Hypocalcified - defect in initial crystallite formation followed by defective growth and hypomineralization. Has normal thickness, smooth surface, less hardness.
332
What does the somatic mesoderm of the first pharyngeal arch give rise to?
Muscles of mastication (masseter, temporalis, pterygoids) tensor tympani, mylohyoid, tensor palatini, and anterior belly of digastric.
333
What are the final cells produced by spermatogenesis?
Sperm or spermatozoa
334
What is ectodermal dysplasia?
Inherited disorders that affect the hair, nails, sweat glands, teeth. You need two of these to be considered. It is genetic, but you can be first in family due to a mutation. Teeth can be missing, pointed, widely spaced, prone to cavities because of defective enamel, multiple denture replacements are needed as child grows, implants may be an option as well, and ortho.
335
What nerve innervates all of the small salivary glands in the insides of the cheeks, tongue, lips, floor of mouth, sublingual gland, and submandibular gland, which are all below the level of the oral fissure?
Chorda tympani branch of the Facial nerve - CN VII
336
What are all cancer types traced back to?
Harmful mutations multiplied by mitosis. Cancer occurs when normal "checkpoints" regulating mitosis are ignored or over-riden by a cancer cell, resulting in uncontrolled cell division.
337
What innervates the sensory component of the anterior 2/3 of the tongue?
It is supplied by the lingual branch of the mandibular branch (V3), which comes off of CN V-Trigeminal nerve
338
Through which two mediums does cancer usually spread or metastasize?
Through the lymph system or bloodstream.
339
What happens during maturation stage of amelogenesis?
Ameloblasts transport substances used in the formation of enamel.These cells become striated and have a ruffled border. The ruffled border on the distal aspect helps increase the surface area of the ameloblast to help deliver matrix proteins. The prisms in the enamel grow in thickness, but not in length here.
340
What separates the two plates of mandibular bone?
The mandibular symphysis
341
When do the symphyseal cartilages appear during embryonic development and when are they replaced by bone?
Between the 10th and 14th week, and during the first year after birth.
342
What are the main factors controlling the stability of enamel?
Active concentrations of free calcium, phosphate, and fluoride in salivary solution.
343
What are the characteristics associated with Spina Bifida Occulta?
Mildest type of spina bifida, with this, there is a small gap in the spine, but no opening or sac on the back, and this might not even be discovered until late childhood.
344
Sutures have intrinsic growth potential. True or False?
False, they do not, unlike endochondral growth plates, which expand through chondrocyte hypertrophy. Rather sutures produce new bone at the sutural edges of the bone fronts in response to external stimuli, such as signals arising from the expanding neurocranium, which allows growth of the cranial vault to be coordinated with growth of the neurocranium. Too little bone growth results in wide-open fontanelles, and too much results in osseous obliteration of the sutures or craniosynostosis.
345
What are the two layers that make up the reduced enamel epithelium?
A layer of ameloblast cells and cuboidal cells from the outer enamel epithelium.
346
What nerve supplies parasympathetic innervation to the parotid gland?
Glossopharyngeal nerve - CN IX
347
What are the disproven and most widely held current theory of tooth eruption?
Tooth is pushed upward by growth of root, by bone around the tooth, by vascular pressure. But probably a combination of root, PDL, dental follicle.
348
Where is a common location for the mandible to fracture when the side of the jaw is struck sharply?
Just below the opposite mandibular condyle, it is a relatively fragile area. When this happens, the condyle fragment is usually retracted anteriorly well away from its previous location by the pull of the lateral pterygoid muscle.
349
What does the somatic mesoderm from the third pharyngeal arch give rise to?
The stylopharyngeus muscle
350
What do the three cranial base synchondroses look like?
They look like a two-sided epiphyseal plate with an area of cellular hyperplasia in the center and bands of maturing cartilage cells extending in both directions, that will eventually be replaced by bone.
351
Is a condyle a growth site or a growth center?
Growth site
352
What was the mandible once viewed as, as it pertains to theories of growth? And what do we believe now?
As a long bone that had been modified into a horseshoe shape with its epiphyseal plates being the condylar heads. However, this is incorrect, and the mandibular condyles are growth sites, not growth centers.
353
What are the main four drugs that influence neural crest cell migration?
1. Alcohol2. Thalidomide3. Accutane4. Retinoic acid
354
Which cells in bone does PTH stimulate?
The osteoclasts to cause bone resorption and increase blood calcium.
355
What is the end result of Mitosis?
It is a process of cell division that creates two identical daughter cells, each carrying a copy of the original cell's DNA.
356
Which bones are derived from neural crest mesenchyme from the first pharyngeal arch?
Maxilla, mandible, zyogamatic, and squamous portion of temporal bone
357
Once embryonic development is complete, how is intramembranous bone growth achieved?
Through bone formation within a periosteum or by bone formation at sutures. It is entirely the result of periosteal activity at the surfaces of the bones and contains no cartilage. The growth happens between adjacent skull bones called the cranial sutures.
358
What is the name of the long arm of the chromosome?
Q arm
359
How many days after fertilization does the blastocyst perform zona hatching?
5 days, the zona pellucida degenerates and decomposes, and is replaced by the underlying layer of the trophoblast cells now called the cytotrophoblast, which is now free to implant with the endometrium.
360
What is the name for a trisomy of sex chromosomes?
Klinefelter syndrome. Males that have an extra X chromosome in most of their cells. They can have one extra X or even multiple. It occurs in about 1 out of 500-1000 baby boys.
361
What is given to babies with cleft lip or palate to help them eat?
Obturator
362
What can defects in the development of the first pharyngeal cleft result in?
Preauricular cysts and or fistulas, and may even threatn the facial nerve VII if it becomes infected
363
What is the name of the epiblast layer once the ingressing of the epiblast cells is complete?
Ectoderm, and this is now when the bilaminar disc is called Trilaminar
364
What ploidy are immature gametes like spermatogonia and oogonia?
Diploid 2N, and they are produced from the primordial germ cells. They undergo a process called meiosis where they are changed from diploid 2N to haploid 1N.
365
What is the Latham device?
It is indicated for babies with complete clefts of the lip and palate, which are widely space, and is considered pre-surgical orthopedics. It is designed to bring the two pieces of the cleft palate closer together, it is worn for about 6-8 weeks, and does require surgery to install it. It has a screw that you turn every day. And then closure of the lip is performed when the baby weighs as least 10 pounds, 3-6 months of age, at same time Latham is removed.
366
What do the mesenchymal cells that appear under and around each of the 20 dental lamina growths consist of and where are they migrating from?
They consist of neural crest derived cells and are migrating from the caudal region of the mesencephalon and the cranial region of the metencephalon.
367
What does Vitamin D do with calcium?
It helps the intestines absorb calcium, but vitamin D must first be activated by PTH. Vitamin D also increases re-absorption of urinary calcium and phosphorus in the renal tubules. And Vitamin D has a direct effect on the parathyroid gland to suppress PTH secretion when we have too much of it.
368
What is euchromatin?
It is the first level of packaging represented as the "beads on a string" structure
369
What are sharpey's fibers?
They are also called extrinsic fibers and form when collagen fibers formed by fibroblasts of the PDL form and incorporate into the cementum.
370
What is the name of the layer that replaces the degenerating zona pellucida?
Cytotrophoblast, which is the layer (along with the syncytiotrophoblast) that helps implants into the endometrium. Happens about 5 days after fertilization.
371
Chromosomes are always visible in the cell's nucleus under microscope. True or False?
False. Only when they are dividing.
372
When does the coronoid cartilage completely disappear by?
Before birth. It gives rise to the coronoid process.
373
What does the development of the mandible begin as?
A condensation of mesenchyme just lateral to Meckel's cartilage, at the angle formed by the division of the incisive and mental nerves and proceeds entirely as an intramembranous bone formation.
374
What is the gene associated with Turner syndrome?
SHOX - Short Stature Homeobox gene, which provides instructions for making a protein that regulates the activity of other genes, and especially important for making skeleton.
375
What are the three basic components of innervation of the tongue?
Motor, sensory, taste
376
Are more recently graduated orthodontists more or less likely to recommend prophylactic removal of third molars to prevent anterior crowding?
Less likely
377
What are the four main drugs that cause cleft lip?
1. Phenytoin2. Vitamin A (Accutane)3. Prednisone4. Cigarette smoking (hypoxia)
378
What are the main oral differences to watch for with Down Syndrome patients?
High mouth breathing = decreased saliva, fluoride toothpaste to help with cariesFissured Tongue = Show them how to brush their tongueAngular Cheilitis = usually by candidaDelayed tooth eruptionMicrodontiaClass III occlusionEarly orthodontic clinical and x-ray eval is importantOcclusal sealants are recommendedDecay in primary dentition should be treated (because of delayed and missing permanentEarly severe periodontal disease (96% with adults)
379
At what week is closure of the vertebral arches completed?
Week 11
380
What helps form the bony hard palate?
Mesenchymal condensations in the ventral portion of the secondary palate form the bony hard palate.
381
What is a LeFort III fracture?
It passes through the nasal bridge medially, extending laterally through the medial orbital rim, nasolcarimal groove, ehtmoid bones, floor of orbit, lateral orbital wall, and zygomatic arch. They separate the entire midface from the cranium, and results in a bone fragment that includes the nasal complex, inferior half of orbit, zygoma, entire maxilla.
382
What is the clinical appearance of Klinefelter?
Enlarged breastsMalocclusionsIncreased pulmonary disordersIncreased autoimmune disordersDiabetes mellitus in 8%Cleft palateBolton discrepancyTaurodontism
383
What are the main differences between Aperts and Carpenter syndromes?
They both have acrocephaly, mental retardation, syndactyly of hands and feet, but Carpenter's is passed by autosomal recessive, has mild obesity, and mutation is RAB23 gene, whereas Apert is autosomal dominant and passed on FGFR2 gene.
384
What is the difference between primary and secondary cartilage?
They differ in embryonic origin and in histological organization, and are generally considered to have a different mode of growth. During development, primary cartilage reacts primarily to systemic growth stimuli such as hormones. Whereas secondary cartilage only secondarily follows these overall stimuli after additional modulation by local growth factors.
385
What is the rod sheath?
It is a space that contains an increased amount of residual matrix proteins.
386
What is the name of the foot like processes that the flattened epiblast cells around week 16 develop? And what is their function?
Pseudopodia, and they allow the epiblast cells to migrate through the primitive streak into the space between the epiblast and the hypoblast.
387
What type of symptoms can present in early children that should be checked for craniosynostosis?
Hydrocephalus, bulging anterior fontanelle, irritability, lethargy, rapidly increasing head size, vomiting, vision impairment, difficulty breathing through nose.
388
What is the most complex structure of the human skeleton?
The cranial base. Its shape is a multifactorial product of numerous developmental and functional interactions
389
What is a chiasma?
It is the point at which paired chromosomes remain in contact crossing over and exchanging genetic material. So similar to them being in synapsis.
390
What does the second pharyngeal pouch develop into?
Crypts of the palatine tonsil, and later, lymphocytes from the bone marrow and thymus infiltrate the underlying lamina propria to establish the definitive palatine tonsil
391
What is the lingula in the adult mandible?
The ramus of the mandible develops by a rapid spread of ossification posteriorly into the mesenchyme turning away from Meckel's cartilage, and this point of divergence is the lingula.
392
What is Monosomy 21?
When an embryo is formed by fusion of a gamete lacking chromosome 21 with a normal gamete, they die rapidly.
393
The growth of the cranial base and the brain is closely interdependent. True or False?
False. The independent growth potential of synchondroses are also evident from the observation that their growth continues for a longer duration than that of the brain, meaning that their growths are not closely interdependent. Studies suggest that synchondroses are genetically coded in craniofacial growth and will develop even in the absence of functional activity.
394
What is Pierre Robin syndrome?
Is present at birth, infant has smaller than normal lower jaw, tongue falls back in throat, difficulty breathing. Can be caused by intrauterine folding or by changes in the DNA near the SOX9 gene. Usually not inherited. Also includes cleft soft palate, receding chin, small jaw, natal teeth. These babies frequently experience breathing difficulties, choking, congestive heart failure, low blood oxygen and brain damage, pulmonary hypertension.
395
What serves as the major sites of bone expansion during postnatal craniofacial growth?
Sutures. For them to function as an intramembranous growth site, they need to remain in an unossified state, yet allow net bone to be formed at the edges of the overlapping bone fronts.
396
When does the development of the tongue begin, and how?
At the end of the 4th week, it begins when the **1st pharyngeal arch** forms a median swelling called the median tongue bud, then later the **1st pharyngeal arch** develops an additional pair of lateral swellings called the distal tongue buds, which rapidly expand to overgrow the median tongue bud. These swellings (distal tongue buds) continue to grow throughout embryonic and fetal life and form the anterior two thirds of the tongue.
397
What does the somatic mesoderm from the sixth pharyngeal arch give rise to?
The intrinsic muscles of the larynx
398
PTH has no direct established activity on the intestine. True or False?
True, but indiretly it increases intestinal calcium and phosphorus absorption via stimulation of 1,25 dihydroxyvitamin D production.
399
What helps guarantee ionic exchanges directed towards the tooth surfaces that begin with tooth eruption resulting in post-eruptive maturation?
High concentrations of calcium and phosphate in saliva.
400
What are some treatment options for amelogenesis imperfecta?
Crown, over-dentures, implants.
401
What is PGD?
Preimplantation genetic diagnosis, and it is is a screening test used to determine if genetic or chromosomal disorders are present in embryos produced through in vitro fertilization (IVF). Blastomeres are used for this. This is usually performed on patients with increased age, and or when there is a high risk of transmitting a disease-causing mutation.
402
How do synchondroses differ from sutures in regards to their growth potential?
Cranial base synchondroses are endowed with an independent growth potential and are comparable to epiphyseal plates with regards to their tissue-separating capacity.
403
What are the spindle microtubules composed of?
Alpha and beta tubulin subunits. They grow by the addition of tubulin subunits to the + end of the polymer (polymerization) or shrink by the loss of tubulin subunits (depolymerization). The plus end is the growing part and the minus end is the one attached to the centrosome.
404
What happens to thymus gland with DiGeorge syndrome?
It is small or missing, and mature T cells are absent and results in poor immune function and frequent infections.
405
With TNM staging, what is T1?
Tumor is 2 cm or smaller
406
What does the intermaxillary process give rise to?
The philtrum of the upper lip.
407
What happens during Meiosis I - Metaphase I?
Each pair of bivalents (two chromosomes, four chromatids total) align in the metaphase plate. And the position on the plate is random, creating genetic diversity, 50-50 chance for the daughter cells to get either the mother or father's homolog for each chromosome. Also here, the kinetochore fibers from the centrosomes attach to one of the chromosomes of the homologous pair at the centromere, separating the homologous pair.
408
What does the cartilage that form within the pharyngeal arches 1-3 develop from?
The neural crest cells of the midbrain and hind brain regions.
409
What type of bone formation gives rise to the flat bones of the cranial vault?
Intramembranous bone formation
410
How many paired pharyngeal arches are there and how many are externally visible on the embryo?
5, and only four are visible. 1, 2, 3, and 4.
411
What is the first region of the skull to reach adult size?
The cranial base
412
In what structure can primordial germ cells first be identified in humans?
In the definitive yolk sac.
413
When does the dental lamina form?
During the sixth week, a U shaped ridge of epidermis called the dental lamina appears on the upper and lower jaws, and in the seventh week, 10 centers of epidermal cell proliferations (primary teeth) develop at intervals on each dental lamina and grow down into underlying mesenchyme.
414
All tissue systems of the body grow at the same rate. True or False?
False
415
What are the two types of errors or mutations that occur when DNA is improperly copied or Mitosis screws up?
Silent mutations and Missense mutations. Silent have no impact on DNA sequence, while missense does and messes with the function.
416
What structure is just cranial to the cardiogenic area, and what does it give rise to?
The septum transversum, and will give rise to the initial partition separating the coelom into thoracic and abdominal cavities, as well as the diaphragm, stomach, and duodenum. It appears as a thickened bar of mesoderm.
417
What happens during Prophase of Mitosis?
Chromosomes thicken and coil and the nucleolus (the site in the nucleus where rNA transcription and processing/ribosome assembly occurred) shrinks and disappears. The mitotic spindle in the cytoplasm forms between the two pairs of centrioles. The nuclear envelope disappears at the end of prophase, which signals for a substage called prometaphase to take place.
418
What is the name for G1, S, and G2 phases of the cell cycle combined?
Interphase
419
What happens with anomalies of the thyroid development?
It can result in ectopic thyroid tissue and/or cysts present along the course of the thyroglossal duct, and these would be around the midline, wheras the cervical cysts happen as remnants of pharyngeal clefts 2-4 and are found lateral to the sternocleidomastoid muscles.
420
What are the three main types of Spina Bifida?
1. Myelomeningocele2. Meningocele3. Spina Bifida Occulta
421
What are the names of the two poles of the blastocyst called?
Embryonic pole by the inner cell mass, and the Abebmbryonic pole by the blastocoel.
422
What is the name of the central cartilages that arise from the mandibular swellings of the first arch?
Meckel's cartilages
423
What does the definitive endoderm end up giving rise to?
The gut and gut derivatives
424
How many crossover events occur on each pair of human chromosomes during Meiosis I?
Between two and three
425
What is the name of the spaces that allow the skull to be deformed during birth?
Fontanelles
426
What does the first pharyngeal membrane develop into?
The tympanic membrane
427
What does the somatic mesoderm inside the pharyngeal pouches contribute to? And how about the neural crest mesenchyme inside the pharyngeal pouch?
The arch artery as well as skeletal muscle tissue. The neural crest mesenchyme develops into bone, cartilage, and connective tissue in each arch.
428
What has to happen for Meiosis II to be completed?
Fertilization has to occur, resulting in a fertilized zygote (mature oocyte) and second polar body.
429
What does cephalocaudal gradient of growth mean?
It means that there is an axis of increased growth extending from the head toward the feet.
430
Which two organs does PTH mainly act on?
Bone and Kidney
431
When does the 1st pharyngeal arch appear, and at what week do we have all 5 arches?
It appears at the beginning of the 4th week, and we have all by the end of the 4th week.
432
What is Carpenter syndrome?
Mutation in the RAB23 gene, located on chromosome 6, unlike most craniofacial syndromes, this is passed in an autosomal recessive fashion. You get acrocephaly with this, which is premature closure of lambdoid and coronal sutures, extra fingers and toes, short fingers and toes, mental retardation, obesity, short neck, heart disease.
433
What are the five facial swellings that all originate from the first pharyngeal arch?
1. unpaired frontonasal process2. Two maxillary swellings3. Two mandibular swellings
434
Only primary cartilage exists in the maxillary process. True or False?
False. No primary cartilage exists.
435
What is cleft lip?
Failure of maxillary swelling to fuse with the intermaxillary process.
436
What is ACP?
It is amorphous calcium phosphate, and is given ti help release calcium and phosphate ions to convert to apatite for patients with impaired salivary flow to help with tooth remineralization.
437
What are facial features typical of people with DiGeorge syndrome?
Small low-set ears, wide-set eyes, hooded eyes, long face, small mandible, bowing up upper lip.
438
The maxilla is a paired bone. True or False?
True. 2 hemimaxillas are connected together by the intermaxillary suture.
439
Because there is no cartilage replacement in the development of the maxilla, how does growth occur?
It occurs by apposition of bone at the sutures that connect the maxilla to the cranium and cranial base, and also by surface remodeling. Surface remodeling is minimal with the cranial vault but it is very important for maxillary growth.
440
What will the neural plate give rise to?
Its broad cranial portion will give rise to the brain, and a narrow caudal portion will give rise to the spinal cord.
441
On what day does the amniotic cavity appear usually?
On day 8. Fluid then begins to collect between the cells of the epiblast and the overlying trophoblast (or cytotrophoblast).
442
Is a synchondroses a growth site or a growth center?
Growth center
443
What are the palatine shelves?
During weeks 8 and 9, the medial walls of the maxillary processes produce a pair of thin medial extensions called the palatine shelves. They grow downward parallel to the lateral surface of the tongue at first and then they rotate rapidly upward into a horizontal position and fuse with each other and the primary palate, forming the secondary palate.
444
What is the bony cap on each end of a long bone called?
Epiphysis
445
The cartilage that covers the surface of the mandibular condyle at the TMJ is identical to the cartilage found in an epiphyseal plate or synchondroses. True or False?
False, it is different. But hyperplasia, hypertrophy, and endochondral replacement do occur here.
446
What forms the periosteum?
The blood vessels on the outside of the spongy bone condense to form the periosteum.
447
What happens during Meiosis I Prophase I?
Genetic diversity takes place here, and the chromosomes condense, with the two chromosomes of each homologous pair pairing up at their centromeres to form a four limbed structure.
448
What is the name of the muscle that attaches to the posterior aspect of the maxillary palatal shelves?
Superior pharyngeal constrictor muscle, every time we swallow this muscle pulls on the separated palatal shelves. The orbicularis oris muscle is also involved.
449
What is the structure that divides the sensory and taste into two components of the tongue (posterior 1/3 and anterior 2/3)?
Terminal sulcus
450
What nerve supplies sympathetic innervation to the parotid gland?
The superior cervical sympathetic ganglion, and the function is mainly vasoconstriction. It travels around the external carotid artery.
451
Where is the primary palate situated in patients with cleft lip?
Too far forward beyond the tip of the nasal septum.
452
When do the ectodermal thickenings called the nasal placodes begin to appear on the frontonasal process?
During week 5
453
What are chromosomes made up of and where are they found?
They are made up of DNA tightly coiled around histones and are found in the nucleus of each cell.
454
What is a syndrome that can be caused by intrauterine folding?
Pierre Robin syndrome
455
How does cytokinesis right after Meiosis I differ with spermatogenesis and oogenesis?
Spermatogenesis, it happens right down the middle of the parent cell (symmetrical). Oogenesis, it occurs unevenly (asymmetrical). And during this asymmetrical cytokinesis, a secondary oocyte cell and a polar body cell are formed.
456
Does the mandible grow downward and forward, or does it grow upward and backward?
It grows upward and backward in response to translational growth of the soft tissue.
457
What is the difference between a germ cell and an oocyte?
The germ cells develop in the fetus and before birth begins mitosis, then DNA replication, and then freezes right at the start of the first meiotic prophase division. And when they are stopped, they are now called primary oocytes, at very start of Meiosis I. And only when signaled by hormones does one single primary oocyte pick up meiosis where it left off.
458
What is dentinogenesis imperfecat?
It is an autosomal dominant inheritance and is caused by a mutation in the DSPP gene, which provides instructions to cleave the protein dentin sialophosphoprotein for making two proteins essential for normal tooth development. It breaks them into dentin sialoprotein and dentin phosphoprotein (for hardening of collagen).
459
With TNM staging, what is T2?
Tumor is larger than 2 cm across, but smaller than 4 cm
460
What are other causes of enamel defects?
Vitamin A deficiency, measles, antibiotics, fluorosis
461
What two ions are needed to remineralize a carious lesion before cavitation occurs?
Calcium and phosphate
462
What does the bell stage consist of?
This is when the dental papilla has deeply invaginated the dental lamina, and it looks like a bell. Happens during 10th week.
463
What does the first pharyngeal cleft develop into?
The external auditory canal
464
Which arteries does the third pharyngeal arch give rise to?
The common carotid artery and internal carotid artery
465
When the hypoblast produces a new membrane around day 12 that migrates out, what is it called?
The new layer is the endodermal lining of the definitive yolk sac. And as the definitive yolk sac develops, the primary yolk sac breaks up and is reduced to a collection of vesicles.
466
What artery does the first pharyngeal arch give rise to?
The terminal branch of the maxillary artery
467
What is the name of the small plug of acellular material that seals the small hole where the blastocyst implanted?
The coagulation plug
468
What are the main five factors known to increase the risk of cancer?
1. Age2. Habits3. Family History4. Health conditions (especially chronic conditions)5. Environment
469
Do growth centers contain primary or secondary cartilage?
Primary cartilage
470
What 14 teratogens can cause craniofacial malformations?
1. Alcohol - central midface deficiency2. Hydantoin (anticonvulsant drugs)3. Accutane - treacher collins4. Toluene5. Cigarette smoking - cleft lip and palate6. Ionizing radiation - microcephaly7. Aminopterin (chemotherapy) - anencephaly8. Aspirin - cleft lip and palate9. Cytomegalovirus - microcephaly, hydrocephaly10. Dilantin - cleft lip and palate11. Rubella virus - microphthalmia, cataracts, deafness12. Thalidomide - treacher collins13. Valium - treacher collins14. Vitamin D excess - premature suture closure
471
What happens during secretory stage of amelogenesis?
Ameloblast cells are columnar now and they release enamel proteins and contribue to enamel matrix, which is then mineralized by the enzyme alkaline phosphatase. The tome's process develops here when the ameloblasts move away from the dentin, and the process is in contact with the DEJ, and is lays down the crystals of the enamel matrix. The tome's processes are angled as well.
472
What helps form the nasal sac?
The deepening nasal pits fuse to form a single, enlarged ectodermal nasal sac.
473
What secretes the bony matrix called osteoid?
Osteoblasts
474
How many chromosomes do the nuclei of most human cells contain?
They contain 46 chromosomes
475
What ends up forming the anterior two thirds of the tongue?
Distal tongue buds
476
What does the somatic mesoderm from the fourth pharyngeal arch give rise to?
Constrictors of the pharynx, cricothyroid, and levator palatini muscles
477
When do craniosynostosis syndromes typically occur or form?
After 8 weeks, during fetal period rather than embryological period. They result form early closure of the sutures between the cranial and facial bones.
478
What is the name of the cells in the parathyroid glands that sense the low blood levels and help make more PTH?
Chief cells
479
What is the name of the short arm of the chromosome?
P arm
480
When the intraembryonic mesoderm cells migrate CRANIALLY, what do they organize into and form, and what does this end up giving rise to?
They form the notorchordal process (is hollow) and the prechordal plate. The prechordal plate gives rise to the endodermal layer of the oropharyngeal membrane, which forms the mouth opening, and participates in the patterning of the cranial neural tube.
481
What kind of heart defects can accompany DiGeorge syndrome?
Because of lack of blood, you can get a ventricular septal defect, only one large vessels instead of two (truncus arteriosus), or four abnormal heart structures (tetralogy of Fallot)
482
What is the name of the central cartilages that arise from the maxillary swellings of the first arch?
Palatoperygoquadrate cartilages
