Embryology

Question 1

Steps of embryo formation

Answer 1

ovulation, fertilisation, clevage, morula, blastocyst, implantation

Question 2

Blastocyst

Answer 2

outer epithelial layer (trophoblast) and inner cell mass
trophoblast forms extraembryonic structures (part of placenta)

Question 3

Two germ layer stage

Answer 3

inner cell mass splits
embryonic disc forms
epiblast and hypoblast formed

Question 4

gasturlation

Answer 4

formation of primitive streak: defines all major body axes
formation of 3 germ layers: ectoderm, mesoderm, endoderm

Question 5

Formation of the primitive streak

Answer 5

on epiblast a line of thickened cells appear (primitive streak)
primitive streak invaginates to form primitive groove

Question 6

Formation of the derms

Answer 6

Cells of the epiblast migrate medially and into primitive groove
first cells move into hypoblast to form embryonic endoderm
later cells move into space between epiblast and endoderm to become mesoderm
cells left in epiblast become ectoderm

Question 7

Formation of notochord

Answer 7

cartliage-like, transient structure
important for the induction of the neural tube

Question 8

Neural plate

Answer 8

induced by notochord
cranial to primitive node
ectodermal cells differentiate to form neuroectoderm

Question 9

neural tube

Answer 9

formation= neurulation
invagination of the neural plate= neural groove

Question 10

neural crest cells give rise to

Answer 10

dorsal root ganglia, enteric ganglia, schwann cells, melanocytes, sympathetic and parasympathetic ganglia

Question 11

mesoderm

Answer 11

divided into:
paraxial mesoderm
intermediate mesoderm
lateral mesoderm

Question 12

fate of paraxial mesoderm

Answer 12

dermis of skin, axial skeleton, axial and limb muscles

Question 13

fate of lateral mesoderm

Answer 13

heart and vasculature
wall of gut
bones of the limbs

Question 14

fate of intermediate mesoderm

Answer 14

the urogenital system: kidneys, gonads, duct systems

Question 15

Mullerian duct

Answer 15

oviduct, uterus, upper vagina

Question 16

Wolffian duct

Answer 16

epididymis, vas deferens, seminal vesicles

Question 17

In males

Answer 17

1.AMH > degeneration of mullerian duct
2. testosterone > wolffian duct develops into epididymis, vas defs, seminal vesicle

Question 18

In females

Answer 18

No AMH > mullerian duct develops into oviduct, uterus, upper part of vagina
No testosterone: wolffian duct disappears

Question 19

vasculogenesis (fate of lateral mesoderm)

Answer 19

haemangioblast migration > blood island formation > cell differentiation > pericyte recruitment

Question 20

Angiogenesis (fate of lateral mesoderm)

Answer 20

blood vessels formation from pre-existing vasculature
outgrowth and tube formation
stabilisation

Question 21

endoderm

Answer 21

forms lining of digestive tract, pharynx, heart and blood vessels

Question 22

allantois

Answer 22

endodermal, surrounded by blood vessels
sac-like structure
helps with gas exchange and excretion

Question 23

development of the gut

Answer 23

closed at cranial and caudal end
3 parts: foregut, midgut, hindgut
(three regions defined by there blood supply)

Question 24

development of the stomach

Answer 24

enlarges and broadens ventro-dorsally
dorsal part grows faster than ventral part: greater curvature of the stomach
rotation 90 degrees clockwise
rotation superiorly bends duodenum into C-shape

Question 25

derivatives of the foregut

Answer 25

thyroid, parathyroid, thymus, lungs, liver, gall bladder, pancreas

Question 26

derivatives of the hindgut

Answer 26

urinary bladder

Question 27

each pharyngeal arch contains

Answer 27

central cartilaginous skeletal element striated muscle rudiment arch specific cranial nerve aortic arch artery

Question 28

primordial germ cells

Answer 28

precursors of sperm and egg at base of allantois (not in gonads)