Embryology Flashcards
(170 cards)
1
Q
What does genetic mixing require?
A
Adaptation of the sexes - anatomical, physiological, behavioural. 2 haploid gametes.
System to make gametes, allow them to meet, allow individual to develop, and control the whole process.
2
Q
What does the male internal genitalia consist of?
A
Testis, duct system (epididymis, vas deferens, urethra), seminal vesicles, prostate gland, bulbs-urethral glands
3
Q
What does the male external genitalia consist of?
A
Penis, scrotum
4
Q
What does the female internal genitalia consist of?
A
Ovaries, duct system (fallopian tube, uterus, cervix vagina)
5
Q
What does the female external genitalia consist of?
A
Vagina, vestibule, labia minora, labia majora, clitoris
6
Q
Where does reproductive tract functional development occur?
A
After birth
7
Q
When does reproductive tract maturation development occur?
A
Puberty
8
Q
Where does structural tract functional development occur?
A
In utero
9
Q
What are the stages of maturation?
A
Childhood followed by adolescence
10
Q
What are the male secondary sexual characteristics?
A
Increased (relative) body size Body composition and fat distribution Hair and skin Facial hair Male pattern baldness CNS effects Smell
11
Q
What are the female secondary sexual characteristics?
A
Decreased (relative) body size Subcutaneous fat distribution Hair and skin Breast development CNS effects
12
Q
What is the urogenital ridge?
A
Region of intermediate mesoderm giving rise to both the embryonic kidney and the gonad.
13
Q
From what type of embryonic tissue is the reproductive tract primarily derived from?
A
Mesoderm
14
Q
What is the gonad derived from embryologically?
A
Intermediate mesoderm plus primordial germ cells (extragonadal)
15
Q
What are primordial germ cells?
A
Special population, ‘seed’ for the next generation (very important!). Allocated shortly after initiation current generation. Arise from yolk sac and migrate into retroperitoneal, along the dorsal mesentery.
16
Q
Where do primordial germ cells arise from embryologically?
A
Arise from yolk sac and migrate into retroperitoneal, along the dorsal mesentery.
17
Q
How do primordial germ cells, which arise in the yolk sac, get into the future reproductive organs?
A
Migrate into retroperitoneal, along the dorsal mesentery.
18
Q
Expression of what genes drives the development of the male?
A
SRY
19
Q
What drives development of female characteristics?
A
Absence of Y chromosome, absence of SRY gene expression.
20
Q
What do mesonephric tubules do?
A
Perform a primitive renal function. Along with mesonephric duct form the primitive kidney.
21
Q
What is the mesonephric duct also known as?
A
Wolffian duct
22
Q
What is the cloaca?
A
Early in development, GI, urinary, and reproductive tracts end in single structure, called the cloaca.
23
Q
What is the urogenital sinus formed from?
A
Created from hindgut by urorectal septum
24
Q
What is the paramesonephric duct also known as?
A
Müllerian duct
25
How does the Müllerian duct appear?
As invagination of the epithelium of the urogenital ridge. Caudally makes contact with the cloaca (urogenital sinus). Cranially opens into the abdominal cavity.
26
Describe what happens to the ducts in the early XY embryo
Testis develop - androgen secretion supports the mesonephric duct. Testis secrete Müllerian inhibiting substance, therefore paramesonephric duct degenerates
27
Describe what happens to the ducts in the early XX embryo
Ovary develops - no androgen, therefore mesonephric duct degenerates. (No testis derived Müllerian inhibiting substance)
28
What happens to the mesonephric duct in the absence of testis derived testosterone?
Degenerates
29
Under what circumstances does the paramesonephric duct degenerate?
In the prince of testis derived MIH
30
What is present in the indifferent stage of development of the external genitalia?
Basic components (genital tubercle), genital folds, genital swellings
31
What happens to the genital tubercle in the male?
Elongates
32
What happens to the genial folds in the male?
Fuse to form the spongy urethra
33
What causes the changes that form the male external genitalia?
Influence of testis derived androgen h
34
What happens to the genital folds in the female?
No fusion occurs. Urethra opens into vestibule
35
Describe the descent of the ovary
Gubernaculum attaches ovary inferiorly to labioscrotal folds. Ovary descends to the pelvis. Round ligament of the uterus in inguinal canal.
36
List some possible structural defects of the reproductive tract
Cloacal partitioning defects, hypospadias, uterine structural defects (e.g. Bicornuate uterus)
37
What occurs during the fetal period?
Growth and physiological maturation of the structures created during the (much shorter) embryonic period. Preparation for transition to independent life after birth
38
What characterises the embryonic period?
Intense activity (organogeneic period), but absolute growth is very small (except placenta). Growth and weight gain accelerated in fetal period.
39
Outline what occurs in the embryonic stage
Intense morphogenesis and differentiation, little weight gain, placental growth most significant
40
Outline what occurs in the early fetus
Protein deposition
41
Outline what occurs in the late fetus
Adipose deposition
42
How might one assess fetal wellbeing?
Mother - fetal movements
Regular measurements of uterine expansion (symphysis-fundal height)
Ultrasound scan
43
When is an obstetric USS generally carried out?
Approx 20 weeks
44
Why is obstetric USS carried out at approx 20 weeks
Fetus sufficiently large enough to be able to spot abnormalities, but not too late to intervene if needed
45
What is assessed during an obstetric USS?
Calculate age of fetus, rule out ectopic pregnancy, number of fetuses...
46
How is fetus age estimated?
From date of last menstrual period (prone to inaccuracy)
Developmental criteria (allows accurate estimation of fetal age)
Crown-rump length, measured between 7 and 13 weeks to date pregnancy and estimate EDD
47
What is the scan in T1 used to determine?
Location, check number, viability (fetal bradycardia bad)
48
When might the biparietal diameter be used?
Used in combination with other measurements to date pregnancies in T2 and T3
49
What might abdominal circumference and femur length of an embryo be used for?
In combination with BPD for dating ad growth monitoring. Also useful for anomaly detection.
50
What is considered to be the average birth weight?
3500g
51
Below what weight is a baby considered to have had growth restriction?
2500g
52
Above what weight is the macrosomia?
4500g
53
List some Reasons babies might have a low birth weight
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Premature (importance of accurate dating!)
Constitutionally small (small mother)
Growth restriction (associated with neonatal morbidity and mortality)
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54
What develops during the embryonic period, with regards to the lungs?
Only the bronchopulmonary tree
55
When does functional specialisation of the lungs occur?
In the fetal period
56
What occurs with regards to lung development during weeks 8-16?
Pseudoglandular stage. Duct system begins to form within the bronchopulmonary segments created during the embryonic period (bronchioles)
57
What occurs with regards to lung development during weeks 16-26?
Canicular stage - formation of respiratory bronchioles. Budding from bronchioles formed during the pseudoglandular stage
58
What occurs with regards to lung development during weeks 26-term?
Terminal sac stage. Terminal sacs begin to bud from the respiratory bronchioles. Differentiation of type 1 and type 2 pneumocytes. Surfactant.
59
What occurs during the fetal period to prepare the lungs for life?
'Breathing' movements (conditioning of respiratory muscles). Fluid filled (crucial for normal lung development)
60
What implications does lung development have for preterm survival?
Threshold of viability. There is a limit beyond which the lungs will not be sufficiently developed to sustain life. Viability is only a possibility once the lungs have entered the terminal sac stage of development. (I.e. Over 24 weeks)
61
What is infant respiratory distress syndrome?
Often in those born prematurely. Insufficient surfactant production
62
What can be done if it is known a baby is going to be born prematurely?
Glucocorticoid treatment to mother, increasing surfactant production in fetus
63
Approx when is th definitive fetal HR achieved?
Around 15weeks
64
When does fetal kidney function begin?
Week 10
65
What is oligohydramnios?
Too little amniotic fluid. Placental insufficiency, fetal renal impairment
66
What is polyhydramnios?
Too much amniotic fluid. Fetal abnormality e.g. Inability to swallow
67
When does the fetus begin to show coordinated voluntary movements?
4th month
68
When does the fetus start to move?
8th week
69
When is the mother generally aware of fetal movements?
Approx week 17 onwards
70
What has happened by the end of the 4th week?
Embryo has folded, creating the primitive gut tube, and primitive pharynx
71
What is there embryologically, with regards to head and neck structures, by the end of the 4th week?
Embryo has folded, creating the primitive gut tube and primitive pharynx. There are no distinguishing features on the face. Head and neck represent approx 1/2 of the embryo
72
Where is the pharynx embryologically?
Extends from the base of skull to the inferior border of the cricoid cartilage of the larynx.
Nasal - superior to soft palate
Oral - between soft palate and larynx
Laryngeal - posterior to the larynx
73
Where is the nasal pharynx?
Nasal - superior to soft palate
74
Where is the oral pharynx?
Oral - between soft palate and larynx
75
Where is the laryngeal pharynx?
Laryngeal - posterior to the larynx
76
What are the pharyngeal arches?
A system of mesenchymal proliferations in the neck region of the embryo. There are 5 in total (numbered 1,2,3,4,6)
77
What are the pharyngeal arches called individually?
There are 5 in total (numbered 1,2,3,4,6). 5 does not exist in humans.
78
What does the neural tube do?
Neurotube signals cause overlying ectoderm to thicken. Slipper-shaped neural plate. Edges elevate out of the plane of the disk and curl towards each other, creating the neural tube. Anterior edge of neural tube begins to form the brain.
79
What does the brain arise from embryologically?
Anterior edge of neural tube
80
What is the embryological prosencephalon?
Forebrain (cranial most)
81
What is the embryological mesencephalon?
Midbrain
82
What is the embryological rhombencephalon?
Hindbrain (caudalmost)
83
How are cranial nerves classified?
On basis of function and embryological origin.
84
Which cranial nerves come from the pharyngeal arches?
CN V, VII, IX and X
| CN XI and XII also have relationship with pharyngeal arch system
85
What do the cranial nerves of the pharyngeal arches supply?
Mixed sensory and motor functions. Supply the derivatives of the pharyngeal arches.
86
What is the facial skeleton derived from?
The frontonasal prominence and the 1st pharyngeal arch
87
Where do the muscles of mastication derive from?
Pharyngeal arch 1
88
Where do the muscles of facial expression arise from?
Pharyngeal arch 2
89
What are the muscle derivatives of the 3rd pharyngeal arch?
Stylopharyngeus
90
What are the muscles derivatives of the 4th pharyngeal arch?
Cricothyroid, levator palatine, constrictors of the pharynx
91
What are the muscle derivatives of the 6th pharyngeal arch?
Intrinsic muscles of the larynx
92
What does CN V (trigeminal) nerve supply?
Principal sensory nerve of the head. Skin of the face and lining of the mouth and nose. Motor innervation to muscles of mastication and muscles derived from mandibular process
93
Which pharyngeal arch does the trigeminal nerve arise from?
1st
94
To which pharyngeal arch does the CN VII (facial) arise from?
2nd arch
95
What does the CN VII (facial) nerve supply?
Passes through the stylomastoid foramen and parotid gland. Mostly motor (muscles of facial expression, and muscles derived from 2nd Ph Arch). Small sensory component (taste buds in anterior 2/3 tongue)
96
To which pharyngeal arch does the CNXI (glossopharyngeal) nerve arise from?
3rd arch
97
What does the CN XI (glossopharyngeal) supply?
Stylopharyngeus muscle and provides general and special sensory information
98
From which pharyngeal arch does the CN X (vagus) nerve arise?
4th and 6th arches
99
What does the superior laryngeal branch of the vagus CN X supply?
Cricothyroid, constrictors of the pharynx
100
What does the recurrent laryngeal branch of the vagus CN X supply?
Intrinsic muscles of the larynx
101
What is the 1st pharyngeal arch cartilage known as?
Meckels
102
What is the 2nd pharyngeal arch cartilage known as?
Reicherts
103
What are the cartilage of pharyngeal arches 4 and 6 known as?
The cartilages of the larynx
104
What does the 1st pharyngeal arch divide into?
Maxillary and mandibular prominences
105
What does the mandibular prominence of the 1st pharyngeal arch go on to develop?
Meckels cartilage (prominent). Malleus and incus, provides 'template' for mandible which forms by membranous ossification
106
What does the 2nd arch cartilage (reichers) go on to develop?
Stapes (middle ear bone). Additional skeletal contributions (styloid process and hyoid bone, lesser cornu and upper body)
107
What is derived from the 3rd arch cartilage?
The hyoid bone
108
Where is the aortic sac located embryologically?
In the floor of the pharynx
109
What happens to the 1st aortic arch?
Disappears
110
What happens to the 2nd aortic arch?
Disappears
111
What happens to the 3rd aortic arch?
Becomes the internal carotid artery
112
What happens to the 4th aortic arch?
Left becomes the arch of aorta
| Right becomes brachiocephalic artery
113
What happens to the 6th aortic arch?
Becomes the pulmonary arch
114
What happens to the 2nd pharyngeal pouch?
Epithelial proliferation, followed by colonisation by lymphoid precursors
115
What happens to the 3rd and 4th pharyngeal pouches?
Divide into dorsal and ventral components
116
What happens to the 3rd and 4th pharyngeal pouches dorsal component?
Becomes parathyroid
117
What happens to the 3rd pharyngeal pouches ventral component?
Becomes the thymus
118
What do the middle ear ossicles derive from embryologically?
Cartilage bars
119
What do the tympanic cavity and auditory tube derive from embryologically?
1st pharyngeal pouch
120
Which pharyngeal clefts remain?
Only the 1st!
121
What happens to the 2nd pharyngeal cleft?
Grows down to cover others, obliterating all other clefts
122
What drives development of the face?
Expansion of the cranial tube
Appearance of a complex tissue system associated with the cranial gut tube and the outflow of the developing heart
Development of the sense organs, and the need to separate the respiratory tract from the GI tract
123
What has each of the pharyngeal arches got? (6 things)
```
Artery (aortic arch artery)
Vein
Nerve
Mesenchymal 'filling'
Ectodermal covering
Endodermal lining
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124
What is the neural crest?
A specialised population of cells that originate within the neuroectoderm. Sometimes referred to as a 'fourth germ lineage'
125
Where does the neural crest originate?
Within the neuroectoderm
126
Where is the neural crest found?
On the lateral border of the neuroectoderm. Becomes displaced and enters mesoderm
127
What happens to the neural crest?
Migrates from the lateral border of the neuroectoderm and enters the mesoderm. Contributes to a variety of head and neck structures
128
What are the major features of the face to be achieved embryonically?
Palpebral fissures
Oral fissures
Philtrum
Nares
129
What does the facial primordai consist of?
1st pharyngeal arch
| Frontonasal prominence FNP (surrounds ventrolateral part of the forebrain. Primordial of eyes)
130
What, with regards to the premordial face, originates as the 1st pharyngeal arch?
Maxillary prominence
| Mandibular prominence
131
How does the nose appear embryologically?
Nasal placodes appear on frontonasal prominence, then sink to become nasal pits. Medial and lateral nasal prominences form on either side of the pits.
132
How do maxillary prominences grow?
Grow medially, pushing the nasal septa closer together in the midline. Maxillary prominences then fuse with medial nasal prominences. Medial nasal prominences then fuse in the midline.
133
What creates the intermaxillary segment?
Fusion of the medial nasal prominences
134
What does the maxillary prominence give rise to?
Two palatial shelves. These grow vertically downwards into the oral cavity on each side of the developing tongue
135
How do the 2 palatal shelves grow in the embryological mouth?
These grow vertically downwards into the oral cavity on each side of the developing tongue. Once the mandible grows large enough to allow the tongue to 'drop' the palatal shelves grow towards each other and fuse in the midline. The nasal septum develops as a midline down-growth and ultimately fuses with the palatal shelves.
136
What is a lateral cleft lip?
Failure of fusion of medial nasal prominence and maxillary prominence
137
What is a cleft lip and cleft palate?
Failure of fusion of medial nasal prominence and maxillary prominence, Combined with failure of palatal shelves to meet in midline
138
What is the fate of the frontonasal prominence?
Forehead, bridge of nose, medial and lateral nasal prominences
139
What is the fate of the medial nasal prominence?
Philtrum, primary palate, mid upper jaw
140
What is the fate of the lateral nasal prominence?
The sides of the nose
141
What is the fate of the maxillary prominence?
Cheeks, lateral upper lip, secondary palate, lateral upper jaw
142
What is the fate of the mandibular prominence?
Lower jaw and lip
143
When does development of the eyes begin?
4th week
144
How does development of the eyes begin?
Outpockets of the forebrain which grow out to make contact with overlying ectoderm.
145
Describe the embryological development of the eyes
Outpockets of the forebrain grow out to make contact with overlying ectoderm. Optic vesicle grows out towards surface to make contact with lens placode. Lens placode then invaginates and pinches off. Optic placode then gives rise to the lens.
146
What is the retina derived from embryologically?
Diencephalon (forebrain)
147
What gives rise to the eyes lens?
Optic placode
148
Where are the first eye primordia found?
On the side of the head. As facial prominences grow, the eyes move to the front of the face (binocular vision)
149
From what is the external auditory meatus derived from?
First pharyngeal cleft
150
What do the auricle say develop from embryologically?
Proliferation within the 1st and 2nd arches, surrounding the meatus
151
Where do the external ears initially develop?
In the neck. As the mandible grows the ears ascend to the side of the head to lie in line with the eyes
152
What physical features do all common chromosomal abnormalities have in common?
Abnormalities with the external ear
153
What is effected by alcohol in an embryo?
Neural crest migration as well as development of the brain are known to be extremely sensitive to alcohol.
154
What are the lobes and functions of the pituitary?
Anterior - neuroendocrine
| Posterior - endocrine
155
Outline how the pituitary gland forms
Infundibulum - the pituitary has ectoderm and neuroectoderm origins. Downward outgrowth of the forebrain, grows towards the roof of the pharynx.
Rathke's pouch - outpocketing of ectoderm of the stomatodeum. An evagination of the roof of the oropharynx. Grows dorsally towards the developing forebrain.
156
What is the tongue?
Lies partially in the oral cavity, and partially in the pharynx. Highly mobile - lingual frenulum. Comprised of extrinsic and intrinsic muscles.
157
How does the tongue develop embryologically?
Primordial of the tongue appear at about the same time as the palate begins to form. Receives a component from each of the pharyngeal arches.
Lateral lingual swellings over-grow the tubercular impar. The 3rd arch component of the cupola over-grows the 2nd arch component. Extensive degeneration occurs, freeing tongue from the floor of the oral cavity - lingual frenulum.
158
What is the tongue comprised of embryologically?
2 lateral lingual swellings (Ph arch 1)
| 3 median lingual swellings (Ph arch 1 - tuberculum impar, Ph arch 2, 3 (+4) - cupola, Ph arch 4 - epiglottal swelling)
159
Describe the embryological reason for the sensory sensation of the tongue
Mucosa of the anterior 2/3 derived from Ph arch 1 and 3 - general sensory innervation by CN V and CN IX
Posterior 1/3 derived from Ph arch 3 (+4) - general and special sensory innervation by CN IX and X.
Taste buds develop in the papillae - special sensory innervation by CN VII
160
Where do taste buds develop?
Taste buds develop in the papillae - special sensory innervation by CN VII
161
Describe the embryological explanation for the motor innervation of the tongue
Both intrinsic and extrinsic muscles of the tongue develop from myogenic precursors that migrate into the developing tongue. CN XII
162
Outline the embryological development of the thyroid gland
Primordium of the thyroid gland appears in the floor of the pharynx between the tuberculum impar and the cupola. Final position is anterior neck. Descent of the thyriod
163
Outline the descent of the thyroid
Point of origin of descent of thyroid is later marked by foramen cecum. Bifurcates and descends as a bi-lobed diverticulum connected by the isthmus.
164
What is the thyroglossal duct?
During its descent, the thyroid gland remains connected to the tongue by the thyroglossal duct. Pyramidal lobe, approx 50% of population
165
List the constituents of the thyroid gland
Follicular cells - thyroxine and triiodothyronine
Parafollicular cells (c-cells) - calcitonin
Thyroid diverticulum
Ultimobranchial body of the 4th Ph pouch
166
List some thyroid abnormalities
Thyroglossal cysts and fistulae
| Ectopic thyroid tissue
167
What is first arch syndrome?
A spectrum of defects in development of eyes, ears, mandible and palate. Thought to result from failure of colonisation of the 1st arch with neural crest cells
168
What is Treacher-Collins syndrome?
Characterised by hypoplasia of mandible and facial bones. Inherited, autosomal dominant condition
169
What is Di-George syndrome?
Congenital thymic aplasia and absence of parathyroid glands. Syndrome includes a variety of defects 'catch 22', deletion of chromosome 22. Abnormal development of neural crest.
170
What is charge syndrome ?
```
CHD7 (chromodomain helicase DNA-binding domain, ATP dependent chromatin remodeller)
CHD7 heterozygous mutation. CHD7 expression for the production of multipotent NC.
C - Coloboma
H - Heart defects
A - choanal Atresia
R - growth and developmental Retardation
G - Genial hypoplasia
E - Ear defects
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