Kai's Embryology Flashcards
1
Q
Describe what happens in the 1st week
A
Fertilisation and formation of the blastocyst
2
Q
Describe what happens in the 2nd week
A
implantation and formation of the bilaminar embryonic disc
3
Q
Describe what happens in the 3rd week
A
further development of the embryo and formation of the trilaminar embryonic disc
4
Q
Describe what happens in the 4th week
A
folding of the embryo
5
Q
Describe what happens from the 5th- end of the 8th week
A
development of all organs
6
Q
Describe what happens in the 8th week (end)
A
the embryo looks like an adult and is called a foetus (up to 9th week = foetal period)
7
Q
Name the steps from zygote to embryoblast and trophoblast
A
- zygote
- 2cell, 4cell, 8cell
- 16cell morula
- enters uterus
- blastocyst
- embryoblast and trophoblast
8
Q
What does the embryoblast give rise to?
A
bilaminar disc which gives rise to the epiblast and the hypoblast
9
Q
What does the epiblast give rise to?
A
amnioblasts (line the amniotic cavity) and the primtive streak
10
Q
what does the hypoblast give rise to?
A
cells of the blastocyst cavity and inner surface of the trophoblast = exocoelomic cavity/primitive yolk sac
11
Q
how does the trilaminar disc form?
A
via gastrulation
12
Q
In the trilaminar disc, what does epiblast give rise to?
A
ectoderm
13
Q
In the trilaminar disc, what does the hypoblast give rise to?
A
endoderm
14
Q
How is mesoderm formed?
A
from the invagination of some epiblast cells in the primitive streak
15
Q
What does the notochord develop from?
A
mesoderm
16
Q
What does the trophoblast give rise to?
A
cytotrophoblast and syncitiotrophoblast
17
Q
What does the syncitiotrophoblast do?
A
invades maternal tissue, develops blood filled lacunae and establishes placental circulation
18
Q
Where does the embryonic mesoderm grow?
A
between the cytotrophoblast and the exocoelomic membrane
19
Q
What does extraembryonic mesoderm give rise to?
A
splanchopleuric and somatopleuric plates
20
Q
What is the extraembryonic mesoderm responsible for?
A
vascularisation of embryo from placenta and gives rise to chorionic villi which are responsible for the nutrition of the foetus
21
Q
Where is the oropharyngeal membrane?
A
at the cranial end
22
Q
where is the cloacal membrane?
A
at the caudal end
23
Q
What does the oropharyngeal membrane become?
A
The future opening of the oral cavity
24
Q
What does the cloacal membrane become?
A
the future opening of the anal cavity
25
What does cephalocaudal and lateral folding do?
Brings head and tail together and brings yolk sac into the embryo
26
What does ectoderm give rise to? (inc. neural crest cells)
CNS, PNS, Sensory epithelia of the nose eye and ear, pituitary, mammary and sweat glands and enamel of teeth
27
What are the 3 plates of the mesoderm?
paraxial plate, intermediate plate and lateral plate
28
What does the paraxial plate give rise to?
(paired somites)
Myotomes - skeletal muscle
Scleratomes- cartilage and bone
Dermatomes- dermis of the skin
29
What does the intermediate plate give rise to?
kidneys and their ducts, gonads and their ducts
30
What does the lateral plate give rise to?
Somatic/parietal layer- future body wall
Splanchnic/visceral layer- circulatory system, connective tissue for glands and muscle connective tissue and peritoneal compartments of gut wall
31
What does endoderm give rise to?
- Epithelial lining of GI tract, respiratory tract and bladder
- Epithelia of the tympanic cavity and auditory tube
- Parynchyma of thyroid, parathyroid, liver and pancreas
- Hepatocytes in the liver
32
What is the cardiovascular system mostly derived from?
mesoderm
33
What does the first heart field become?
future left ventricle
34
What does the second heart field become?
future right ventricle and future atria
35
What is the right atrium derived from?
Primitive atrium and sinus venosus
36
What is the left atrium derived from?
4 primitive pulmonary veins
37
What is the right ventricle derived from?
Bulbous cordis
38
What is the left ventricle derived from?
Primitive ventricle
39
What is the pulmonary trunk/aorta derived from?
Bulbous cordis/trunkus arteriosus
40
What are the SAN/AVN/bundle derived from?
sinus venosus/AV canal
41
What is the pericardium derived from?
septum transversum
42
What do the pharyngeal arches arise from?
aortic sac
43
What do the 1st pharyngeal arches give rise to?
small part of the maxillary artery
44
What do the 2nd pharyngeal arches give rise to?
Artery to the stapedius
45
What do the 3rd pharyngeal arches give rise to?
common carotid and proximal internal carotid arteries
46
What do the 4th pharyngeal arches give rise to?
Right: Right subclavian
Left: arch of aorta between origin of left carotid and ductus arteriosus
47
What do the 5th pharyngeal arches give rise to?
They never form!
48
What do the 6th pharyngeal arches give rise to?
Right: Proximal- right pulmonary artery
Distal- regresses
Left: left pulmonary and ductus arteriosus
49
What are the 3 foetal circulation changes at birth?
Foramen ovale becomes fossa ovale
Ductus arteriosus becomes ligamentum arteriosum
Ductus venosus becomes ligamentum venosum
50
What is the function of the ductus arteriosus and foramen ovale?
to bypass the pulmonary circulation
51
What is the function of the ductus venosus?
to bypass the liver
52
What is the respiratory system derived from?
The foregut as an outpouching of the oesophagus
53
What does the outpouching of the oesophagus give rise to?
respiratory diverticulum -> splits into left and right buds -> bronchi
54
What does the pseudoglandular stage give rise to?
main structural units i.e. cartilage, smooth muscle, angiogenesis, glands
55
What does the cannalicular stage give rise to?
vascularisation, respiratory bronchioles and alveolar ducts
56
What does the alveolar stage give rise to?
alveolar sacs, T1 and T2 pneumocytes
- T2 from 34 weeks with a dramatic increase pre birth, if baby born premature, may struggle with breathing, so given surfactant
57
What are the boundaries of the foregut?
oropharyngeal membrane -> liver bud
58
What are the boundaries of the midgut?
Liver bud -> 2/3 along the transverse colon
| Remains temporarily attached to the yolk sac via the vitelline duct
59
What are the boundaries of the hindgut?
final 1/3 of transverse colon -> cloacal membrane
60
What are pharyngeal pouches?
Invaginations of endoderm
61
How many pharyngeal pouches are there?
4
62
What does the 1st pharyngeal pouch give rise to?
middle ear and eustachian tube
63
What does the 2nd pharyngeal pouch give rise to?
palatine tonsils
64
What does the 3rd pharyngeal pouch give rise to?
inferior parathyroid gland
65
What does the 4th pharyngeal pouch give rise to?
thyroid gland cells and superior parathyroid gland
66
What are pharyngeal clefts?
invaginations in ectoderm
67
How many pharyngeal clefts are there?
4
68
What does the 1st pharyngeal cleft give rise to?
external auditory meatus and epithelium of eardrum
69
What do the 2nd-4th pharyngeal clefts give rise to?
cervical sinus
70
What is the greater omentum derived from?
dorsal and ventral mesentery (4 layers)
71
What is the lesser omentum derived from?
ventral mesentery only
72
What aspects of the gut does dorsal mesentery cover?
lower foregut, midgut and most of the hindgut
73
What aspects of the gut does ventral mesentery cover?
only foregut
74
Describe stomach rotation
- 90 degrees clockwise
- left becomes anterior
- right becomes posterior
(same for vagal trunks)
75
What creates the lesser sac?
stomach rotation
76
What causes the duodenum to become C- shaped
stomach rotation
77
How is the midgut connected to the yolk sac?
via the vitalline duct
78
Describe the development process of the midgut
Elongation- forms primary intestinal loop with cephalic/proximal and caudal/distal parts
Herniation- loop is expelled through umbilical cord
Rotation- 270 degrees anticlockwise- 90 during herniation and 180 during its return inside
Retraction- reversal of herniation, begins with jejunum
Fixation- some regions lose dorsal mesentery and become retro peritoneal
79
What is the rectum derived from?
endoderm
80
What is the upper 2/3rds of the anal canal derived from?
endoderm
81
What is the lower 1/3rd of the anal canal derived from?
ectoderm
82
When does the anal membrane rupture?
week 7- joins the two parts of the canal
83
How is the liver bud formed?
it is an endodermal outgrowth of the proximal duodenum
84
Describe what happens to the liver bud
Proliferates as cords and penetrates the ventral mesentery
pars hepatica becomes bile duct
pars cystica becomes gall bladder and cystic duct
hepatic sinusoids become hepatocytes
85
What is the pancreas derived from?
endodermal lining of the duodenum which gives rise to a dorsal and a ventral bud
86
What do the dorsal and ventral buds of the duodenum endoderm give rise to?
Dorsal- head, body and tail of pancreas
Ventral- uncinate process of pancreas
Rotation brings the two buds together
87
On what day does the neural plate form?
Day 19- it forms and begins to thicken via differential mitosis and the neural groove appears
88
What happens between day 24 and day 28 to the neural plate?
the neural plate ends join to form the neural tube = neuralation
89
What do neural crest cells give rise to?
- melanocytes and dermis
- adrenal medulla
- cranial nerves 5,7,9,10
- bony skull
- meninges
90
What does lateral migration give rise to?
dorsal root ganglia
91
what does ventral migration give rise to?
sympathetic ganglia
92
What does the anterior neural tube become?
brain
93
What does the posterior neural tube become?
spinal cord
94
What does the anterior neural tube divide in to?
prosencephalon
mesencephalon
rhombencephalon
95
What does the prosencephalon give rise to?
```
telencephalon = cortex
diencephalon = thalamus and hypothalamus
```
96
What does the mesencephalon give rise to?
midbrain
97
What does the rhombencephalon give rise to?
```
metencephalon = pons
myencephalon = medulla
```
98
What are the kidneys derived from?
mesoderm
99
What happens to the pronephros?
degrades 4th week
100
What happens to the mesonephros?
appears 4th week, degrades 6th week
- made of ridge and duct
- combines with genital ridge = urogenital ridge
- forms mesonpheric tubules and glomerulus
101
What happens to the metenephros?
appears 5th week, made from:
- metanephric blastema- nephrons
- uteric bud- renal pelvis, minor and major calyces, collecting ducts
102
Where do the kidneys begin to develop?
Develops in the pelvis and moves cranially
- blood supply from pelvic aorta
- abdominal branches usually degrade but not always
103
What are the bladder and urethra formed from?
endoderm
104
What is the cloaca divided by?
the urogenital septum (of mesoderm)
- this gives rise to:
urogenital sinus and anorectal canal
105
What does the urogenital sinus give rise to?
- bladder
| - prostatic/ membranous/ penile urethras (sup-inf)
106
What are the genital organs derived from?
intermediate mesoderm (sex characteristics at week 7)
107
What is the indifferent stage in genital embryology?
Mesonephric/ Wolffian ducts -> Male
| Paramesonephric/ Mullerian ducts -> Female
108
What are the primitive sex cords derived from?
Primordial germ cells from the epiblast that migrate to the genital ridge and proliferate
109
What is the external genitalia derived from?
mesenchyme
110
Describe the steps from mesenchyme to scrotal/labial swellings
- mesenchyme
- elevated cloacal folds unite
- genital tubercle
- urethral (anterior) and anal (posterior) folds
- scrotal and labial swellings
111
where do the testis develop?
develop retroperitoneal and descend through the inguinal canal
112
What do the primitive sex cords give rise to?
testis cords (contain primordial germ cells, sertolli cells and Leydig cells) and rete testis
113
What do Leydig cells produce?
Testosterone and DHT
114
What do testosterone and DHT do?
causes differentiation of genital ducts (Wolffian) and external genitalia
115
What is tunica albuginea derived from?
genital ridge
116
What is the distal urethra derived from?
ectoderm
117
What 6 things does oestrogen make develop?
- Mullerian ducts
- Urogenital sinus
- This tissue plate
- Urethral folds
- Genital swellings
- Genital tubercle
118
What do the Mullerian ducts become?
uterine tubes, uterus, cervix, upper vagina
119
What does the urogenital sinus (female) become?
lower vagina
120
What does the thin tissue plate (female) become?
hymen, separates lumen of vagina from urogenital sinus
121
What do the urethral folds (female) become?
labia minora
122
What do the genital swellings (female) become?
labia majora
123
What does the genital tubercle (female) become?
clitoris
