embryology

Question 1

when does gastrulation occur

Answer 1

3rd week

Question 2

what happens during gastrulation

Answer 2

embryoblast develops into trilaminar structure = gastrula

Question 3

what are the 3 germ layers of the gastrula

Answer 3

ectoderm, mesoderm, endoderm

Question 4

what does the ectoderm develop into

Answer 4

skin, nervous system, neural crest

Question 5

what does the mesoderm develop into

Answer 5

all types of muscle, most systems, kidneys, blood

Question 6

where does most of CVS system come from (gastrula layer)?

Answer 6

mesoderm - some from cardiac neural crest cells = ectoderm

Question 7

what does the endoderm develop into

Answer 7

Gi tract, endocrine organs

Question 8

what are the 3 parts of the mesoderm

Answer 8

paraxial plate, intermediate plate, lateral plate

Question 9

what does the paraxial plate of the mesoderm give rise to

Answer 9

somites which give rise to supporting tissue of the body;

myotome (muscle tissue), sclerotome (cartilage/ bone), dermatome (dermis of skin)

Question 10

what does the intermediate plate mesoderm give rise to

Answer 10

UG system; kidneys, gonads, and their duct systems

Question 11

what does the lateral plate mesoderm give rise to

Answer 11

somatic (parietal layer) that forms future body wall and splanchnic (visceral) layer that forms circulatory system, connective tissue for glands, muscles/ connective tissue/ peritoneal components of gut wall

Question 12

where is the lateral plate mesoderm

Answer 12

at periphery of embryo

Question 13

what does the 1st heart field develop into

Answer 13

future left ventricle

Question 14

what does the 2nd heart field develop into

Answer 14

atria, future right ventricle outflow tract

Question 15

where is the heart formed from in an embryo

Answer 15

cardiogenic region

Question 16

what shape is the cardiogenic region

Answer 16

horseshoe

Question 17

what happens in day 19 cardiac embryology

Answer 17

2 endocardial tubes form

Question 18

what happens in day 21 of cardiac embryology

Answer 18

lateral folding leads to 2 endocardial tubes fusing to form single heart tube

Question 19

what happens in day 22 of heart embryology

Answer 19

heart begins to beat

Question 20

what happens on day 23 of heart embryology

Answer 20

heart begins to fold

Question 21

what happens on day 35 of heart embryology

Answer 21

bulbous corpus moves inferiorly, anteriorly and to embryo’s right, primitive ventricle moves to embryo’s left, primitive atrium and sinus venous move superiorly and posteriorly so sinus venous is now posterior to primitive atrium

Question 22

what happens on day 50 of cardiac embryology

Answer 22

fully functioning heart made

Question 23

describe the pressure shunt in a foetus

Answer 23

Increased vascular resistance in pulmonary arterial circulation as lungs aren’t fully functioning, so pressure greater in R so most shunted into LA down pressure gradient

Question 24

what happens at the end of the 4th week

Answer 24

septum primum starts to grow towards endocardial tissue

Question 25

what opening allows blood to be shunted from RA to LA in foetus

Answer 25

foramen ostium primum

Question 26

what forms the foramen ostium primum

Answer 26

diminished opening between septum primum and endocardial cushion

Question 27

what forms after the foramen ostium primum

Answer 27

foramen ostium secundum

Question 28

what is the difference between foramen ostium primum and secundum

Answer 28

primum is thin and membranous, secundum is thick and muscular

Question 29

what happens by the 6th week of cardiac embryology

Answer 29

septum secundum stops growing and contains a permanent opening = foramen ovale

Question 30

what happens to the foramen ostium secundum past the 6th week

Answer 30

enlarges and upper part of septum primum degenrates

Question 31

what forms the valve of the foramen ovale

Answer 31

lower part of septum primum

Question 32

describe the passage of blood in the heart past week 6

Answer 32

Ra through foramen ovale, pushes valve of foramen ovale to left, enter RA

Question 33

what happens to blood pressure in the chambers after birth

Answer 33

pressure in right side drops so pressure in left is greater, blood in LA pushes valve of foramen ovale against muscular septum secundum so passage closes and fuse to form solid interatrial septum about 6 months after birth

Question 34

describe endocardial tissue formation leading to division of the av canal

Answer 34

endocardial cushion grows from superior and inferior sides of AV canal to partition it into 2 separate openings which form r and L AV canal

Question 35

what does the bulbus cordis become

Answer 35

right atrium proximal 1/3 forms muscular right ventricle conus cordis forms smooth outflow portion of R/ L ventricles Truncus cordis forms proximal aorta and pulmonary trunk

Question 36

what does the primitive ventricle become

Answer 36

left ventricle

Question 37

what does the primitive atrium become

Answer 37

anterior parts of RA, entire LA, L and R auricles

Question 38

what does the sinus venosus become

Answer 38

part of RA, VC and coronary sinus

Question 39

what does the truncus arteriosus become

Answer 39

aorta and pulmonary trunk

Question 40

when does Vasculogenesis begin

Answer 40

day 18

Question 41

what are blood islands in an embryo

Answer 41

core of hemoblasts surrounded by endothelial cells that act as blood supply for the foetus

Question 42

where do blood islands form in an embryo

Answer 42

extra embryonic mesoderm

Question 43

when do blood islands begin to form

Answer 43

day 17

Question 44

describe Vasculogenesis

Answer 44

angioblasts from splanchnopleuric mesoderm coalesce to form angioblastic cords throughout embryonic disc

Question 45

why do some vessels become arteries and some become veins

Answer 45

embryonic signals in endothelial cells

Question 46

what does the 1st aortic arch form

Answer 46

small parts of maxillary artery

Question 47

what does the 2nd aortic arch form

Answer 47

artery to stapedius

Question 48

what does the 3rd aortic arch become

Answer 48

common carotid arteries and proximal carotid arteries

Question 49

where do distal carotid arteries come from

Answer 49

extensions of dorsal aorta

Question 50

what does the 4th aortic arch become on the right

Answer 50

joins with right dorsal aorta and acquires a branch - the 7th cervical intersegmental artery - which grows into the r upper limb and forms the r subclavian artery

Question 51

what does the 4th aortic arch become on the left

Answer 51

joins with left dorsal aorta and joins L 7th cervical intersegmental artery to grow into left subclavian artery

Question 52

what does the 5th aortic arch become

Answer 52

NOTHING - IT DOESN'T EXIST

Question 53

what does the 6th aortic arch become

Answer 53

R becomes pulmonary trunk | L becomes ductus arteriosus

Question 54

how does oxygenated blood from the placenta get to the foetus

Answer 54

through umbilical vein

Question 55

describe the passage of blood from the placenta through the foetus

Answer 55

umbilical vein then bypasses liver via ductus venosus and combines with deoxygenated blood in IVC then combines with deoxygenated in SVC, enters into RA, shunted through foramen ovale to LA , returns to placenta via umbilical veins

Question 56

what happens to circulation after 1st breath

Answer 56

increased alveolar O2 pressure so vasodilation occurs in pulmonary vessels

Question 57

what does the umbilical vein become

Answer 57

ligamentum teres

Question 58

what does the umbilical arteries become

Answer 58

medial umbilical ligaments

Question 59

what does the ductus arteriosus become

Answer 59

ligamentum arteriosum

Question 60

what does the ductus venosus become

Answer 60

ligamentum venosum