What is a secondary tumor?
A tumor that formed from cells that have spread.
What kind of head and face abnormalities do down syndrome patients have?
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.
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.
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
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.
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?
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.
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.
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.
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.
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.
Between what two cavities does the bilaminar disc lay?
Between the amniotic cavity and the blastocyst cavity (blastocoel)
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.
With TNM staging, what is T2?
Tumor is larger than 2 cm across, but smaller than 4 cm
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.
What are the three main types of Spina Bifida?
1. Myelomeningocele 2. Meningocele 3. Spina Bifida Occulta
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.
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).
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.
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.
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.
What is it called when an encephalocele emerges along with the meninges? Along with ventricular system (CSF)?
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.
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.
What is aneuploidy?
When a cell contains an incorrect number of chromosomes. Usually happens because of failure to line up at metaphase plate.
What is the name of the small plug of acellular material that seals the small hole where the blastocyst implanted?
The coagulation plug
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.
At what week is closure of the vertebral arches completed?
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.
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.
What does the somatic mesoderm from the third pharyngeal arch give rise to?
The stylopharyngeus muscle
What are the main phases of the cell cycle?
M - Mitosis G1 - Growth S - DNA replication G2 - Growth
Which bones are derived from neural crest mesenchyme from the first pharyngeal arch?
Maxilla, mandible, zyogamatic, and squamous portion of temporal bone
What does the first pharyngeal cleft develop into?
The external auditory canal
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.
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.
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.
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.
Which arteries does the six pharyngeal arch give rise to?
The ductus arterious and the definitive pulomonary arteries
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.
What is the name of the central cartilages that arise from the maxillary swellings of the first arch?
What is the clinical appearance of Klinefelter?
Enlarged breasts Malocclusions Increased pulmonary disorders Increased autoimmune disorders Diabetes mellitus in 8% Cleft palate Bolton discrepancy Taurodontism
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
What does the second arch cartilage, which originates from neural crest cells, give rise to?
Stapes, styloid process, styloid hyoid ligament, lesser horn of hyoid bone, upper rim of body of hyoid bone.
What is the bilaminar disc made up of?
An epiblast (primary ectoderm) and a hypoblast (primary endoderm)
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.
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.
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.
What is the name of the long arm of the chromosome?
What are the two groups of cells that the cleaving embryo first divides into?
The trophoblast and the embryoblast
What is the name of an undifferentiated germ cell that gives rise to oocytes?
What layer do all three germ layers derive from during gastrulation?
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.
How many chromosomes do the nuclei of most human cells contain?
They contain 46 chromosomes
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.
What artery does the first pharyngeal arch give rise to?
The terminal branch of the maxillary artery
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.
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.
What are the main five factors known to increase the risk of cancer?
1. Age 2. Habits 3. Family History 4. Health conditions (especially chronic conditions) 5. Environment
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).
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.
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
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.
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.
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.
What is chromatin?
The combination of DNA, histone, and other proteins that make up chromosomes and is found inside the nuclear envelope of eukaryotic cells.
At what stage is the embryo called blastocyst?
When the morula has absorbed fluid and formed a blastocoel along with the inner cell mass.
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.
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.
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.
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.
What are the four phases of Mitosis?
PMAT Prophase Metaphase Anaphase Telophase
Are girls or boy more likely to have encephaloceles in front or back of skull, respectively?
Girls = back Boys = front North America = back Southeast Asia = front
What does the definitive endoderm end up giving rise to?
The gut and gut derivatives
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.
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.
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.
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.
What days do the cranial and caudal ends close by?
Cranial 24 and Caudal 26
Which artery does the second pharyngeal arch give rise to?
The stapedial artery
What innervates the third pharyngeal arch?
The glossopharyngeal nerve IX
What are the main oral differences to watch for with Down Syndrome patients?
High mouth breathing = decreased saliva, fluoride toothpaste to help with caries Fissured Tongue = Show them how to brush their tongue Angular Cheilitis = usually by candida Delayed tooth eruption Microdontia Class III occlusion Early orthodontic clinical and x-ray eval is important Occlusal sealants are recommended Decay in primary dentition should be treated (because of delayed and missing permanent Early severe periodontal disease (96% with adults)
Which arteries does the third pharyngeal arch give rise to?
The common carotid artery and internal carotid artery
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
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.
What is the name of the central cartilages that arise from the mandibular swellings of the first arch?
What is the name of the cartilage of the second arch?
With TNM staging, what is T1?
Tumor is 2 cm or smaller
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.
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.
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.
What innervates the maxillary and mandibular processes of the first arch?
The maxillary and mandibular branches of the trigeminal nerve V
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.
What is euchromatin?
It is the first level of packaging represented as the "beads on a string" structure
On what day of human development is the notochordal process complete?
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.
What is the name for the two identical chromosomes resulting from DNA replication?
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.
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.
What are the two kinds of chromatin?
Euchromatin and Heterochromatin
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.
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.
At what # cell stage of development do the round blastomeres begin to flatten?
At 8-cell stage, developing an inside-outside polarity that maximizes cell-to-cell contact among blastomeres.
How many pairs of autosomes vs sex chromosomes in each nucleus?
22 pairs of autosomes and 1 pair of sex chromosomes (XX or XY)
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.
What is the purpose of Mitosis?
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.
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
Does the embryo grow faster in length or in width?
In length, cranially and caudally.
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
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.
What happens during Anaphase of Mitosis?
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.
What does the first arch cartilage give rise to?
Two ossicles of the middle ear (incus and malleus) and other bony elements
In what structure can primordial germ cells first be identified in humans?
In the definitive yolk sac.
What is an NTD?
Neural tube defect
What innervates the fourth pharyngeal arch?
The superior laryngeal branch of vagus nerve X
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.
Chromosomes are always visible in the cell's nucleus under microscope. True or False?
False. Only when they are dividing.
What ploidy are mature gametes like spermatozoa and a definitive oocyte?
They are haploid
What are the three distinct types of microtubule fibers that the mitotic spindle is composed of?
1. Kinetochore 2. Polar 3. Aster
During Meiosis I or II is the chromosomal number reduced from diploid 2n to haploid 1n?
During Meiosis I
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?
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.
What does the cells of the bilaminar disc develop into?
The embryo proper
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.
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)
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
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.
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.
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).
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.
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.
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
What is the name for G1, S, and G2 phases of the cell cycle combined?
What is the trophoblast the main source of?
The placenta and the associated membranes
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.
What innervates the sixth pharyngeal arch?
The recurrent laryngeal branch of vagus nerve X
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.
What are the final cells produced by spermatogenesis?
Sperm or spermatozoa
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.
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.
What has now blanketed the entire (except for a small region at the abembryonic pole) implanted blastocyst by day 9?
What does the first pharyngeal membrane develop into?
The tympanic membrane
What percent of Down Syndrome cases are hereditary vs random?
1% hereditary, 99% random.
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.
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
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.
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
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?
What packages chromosomes into the condensed structure called chromatin?
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.
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.
What is the neural plate?
It appears as a thickening of the ectoderm on either side of the midline, cranial to the primitive node.
What gives rise to the laryngeal cartilages?
The lateral plate mesoderm of the fourth and sixth pharyngeal arches
What is the most common feature of Turner syndrome?
Short stature, and you can usually tell by age 5. Most Turners have normal intelligence.
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.
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
What is the name of the process of cell migration, invagination, and ingress that occurs around the beginning of week 3?
How many crossover events occur on each pair of human chromosomes during Meiosis I?
Between two and three
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.
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.
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.
Through which two mediums does cancer usually spread or metastasize?
Through the lymph system or bloodstream.
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.
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.
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.
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.
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.
In what direction does the notochordal plate form from the hollow notochordal process fusing with the underlying endoderm?
In a caudal to cranial direction
What does the first pharyngeal pouch develop into?
The eustachian tube and middle ear cavity
What percentage of conceptions result in spontaneous abortion because of chromosomal abnormalities?
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.
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.
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.
With TNM staging, what is T0?
Carcinoma in situ, still localized and contained within top layers of cells lining oral cavity or oropharynx.
What is the embryoblast the main source of?
The embryo itself, and is also called the inner cell mass
During what week of embryonic development does the embryoblast split into two layers forming a bilaminar disc?
What is gametogenesis?
The development and production of the male and female mature gametes.
With TNM staging, what is N3?
The cancer has spread to a lymph node that measures more than 6 cm across.
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.
What are the aortic arches?
They are a series of six paired embryological vascular structures which give rise to several major arteries.
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.
Which arteries does the fourth pharyngeal arch give rise to?
Arch of the aorta, right subclavian artery and original pulmonary arteries
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.
What innervates the second pharyngeal arch?
The facial nerve VII
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.
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
How is genetic diversity achieved during Meiosis I?
Through crossing over and through independent assortment, the random positioning of homologous chromosomes.
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.
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.
What resembles Mitosis more, Meiosis I or Meiosis II?
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.
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.
What happens to pharyngeal clefts 2, 3, and 4?
They are overgrown by expansion of the 2nd pharyngeal arch and are usually obliterated
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.
What does the mesenchyme that covers the dorsal side of the neural tube end up giving rise to?
The vertebral arches and skull.
What does the somatic mesoderm from the sixth pharyngeal arch give rise to?
The intrinsic muscles of the larynx
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.
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.
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.
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
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.
What does the somatic mesoderm from the fourth pharyngeal arch give rise to?
Constrictors of the pharynx, cricothyroid, and levator palatini muscles
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.
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.
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.
With TNM staging, what is T3?
Tumor is larger than 4 cm across
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.
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
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.
What is the name of the short arm of the chromosome?
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.
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.
What is Monosomy 21?
When an embryo is formed by fusion of a gamete lacking chromosome 21 with a normal gamete, they die rapidly.
What is the process of cleavage?
Subdividing the zygote without increasing its size.
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.