Lecture 5 - Development of Cardiovascular system

Question 1

When does the first contraction of the heart occurʔ

Answer 1

on day 22 and continues heart development

Question 2

when does heart formation startʔ

Answer 2

in week 3

Question 3

which 3 layers is the heart made up of

Answer 3

Endocardium - derived from the heart tube
myocardium - derived from visceral mesoderm - overlying heart tube
Epicardium - visceral layer of pericardium from visceral mesoderm

Question 4

What is vasculogenesisʔ

Answer 4

endoderm induces some cells of visceral mesoderm to differentiate into angioblasts
Angioblasts differentiate into endothelial cells and form tubes - endocardial tubes

Question 5

how does the primitive heart tube formʔ

Answer 5

Endocardial tubes fuse during lateral folding to form the primitive heart tube
Visceral mesoderm surrounding the heart tube differentiates to form the myocardium.
The myocardium secretes a thick layer of extracellular matrix

Question 6

What brings the developing heart tube into the thorax

Answer 6

Craniocaudal folding

Question 7

What is responsible for the formation of the coronary arteries

Answer 7

the epicardium

Question 8

What separates the myocardium from the endocardium

Answer 8

gelaltinous connective tissue

Question 9

What forms the internal endothelial lining of the heart

Answer 9

endocardium

Question 10

Which 3 unpaired veins drain into the tubular heart of a 4 week embryo via left and right horn of sinus venosus

Answer 10

vitelline vein
umbilical vein
common cardiac vein

Question 11

What connects the 2 dorsal aorta

Answer 11

cranial region

Question 12

Which 5 parts does the heart tube differentiate into

Answer 12

1. truncus arteriosus
2. conus arteriosus
3. ventricle
4. atrium
5. Sinus venosus
   these develop into adult structures of the heart

Question 13

What happens on day 23ʔ

Answer 13

The heart tube starts to fold in prep for dividing into 4 chambers

Question 14

Bulbus cordis moves

Answer 14

caudally, ventrally and to the right

Question 15

Primitve ventricle

Answer 15

is displaced to the left (mainly left ventricle

Question 16

Primitive atrium

Answer 16

displaces cranially and dorsally

Question 17

When does the sinus venosus degenerate

Answer 17

week 5

Question 18

What are the remnants of sinus venosus

Answer 18

part of the right atrium and left horn becomes oblique vein of the left atrium and coronary sinus

Question 19

remnants of the right horn sinus venosus

Answer 19

right horn forms the smooth walled part of right atrium - sinum venarum
rest of atrial wall - trabeculated

Question 20

how are the ventricles formed

Answer 20

majority formed from the primitive ventricle and small contribution from conus arteriosus.

Question 21

What does the conus arteriosus form

Answer 21

The conus arteriosus forms the smooth walls of the left and right ventricles that lead into the aorta and pulmonary trunk (conus arteriosus) respectively
rest of ventricular wall - trabeculated and formed from primitive ventricle - trabeculae carnae

Question 22

Further differentiation of the atria

Answer 22

right atrium enlarges by incorporating right sinus horn and lA undergoes remodelling

Question 23

how does the la remodel

Answer 23

outgrowth in the lA wall forms a single pulmonary vein which bifurcates into right and left and then branches again to form 4 PV

Question 24

what is intussusceptionʔ

Answer 24

in week 5, 4 pulmonary veins are incorporated into the wall of the lA

Question 25

how does septation of the primitive atrium occurʔ

Answer 25

Majority of atrial wall is derived from the primitive atrium
now needs to be divided into right and left
crescent shaped outgrowth - septum primum in week 4
Septum primum extends and diminishing connection - foramen primum

Question 26

how does the atrioventricular septum formʔ

Answer 26

As septum primum extends, endothelial lining boundary expands to form dorsal and ventral endocardial cushions. These will fuse with the midline to form the atrioventricular septum.

Question 27

What happens in week 6

Answer 27

Apoptosis occurs in top part of septum primum to form foramen secundum. Second crescent shaped projection forms - septum secundum

Question 28

how does the foramen ovale form

Answer 28

The septum secundum does not completely form

opening - foramen ovale

Question 29

What does the foramen ovale do

Answer 29

allows blood to flow from right to left atrium, by passing the lungs.

Question 30

What are the 2 origins of the intraventricular septumʔ

Answer 30

A muscular part - projects from the floor of the primitive ventricle towards the endocardial cushions leavind an interventricular foramen in week 4
a membranous part - projects inferiorly from endocardial cushion - to close the interventricular foramen in week 7

Question 31

how do the aorta and pulmonary trunk formʔ

Answer 31

the truncus arteriosus divides into 2 by endocardial swellings - conotruncal ridges - they fuse to form a septum that separate flow of right from left ventricles and fuse with inter-ventricular septum. they spiral around eachother so connection is proper.

Question 32

What do the conotruncal swellings containʔ

Answer 32

neural crest cells - fro the neural tube. they migrate and differentiate into a variety of structures -

Question 33

what are neural crest cells referred toʔ

Answer 33

The 4th germ layer

Question 34

Foetal circulationʔ

Answer 34

O2 blood enters through umbilical vein. some blood enters liver, most enters ductus venosus and then ivc. ivc enters right atrium and then to la through foramen ovale and then aorta. poorly oxygenated blood from lungs and passes through ductus arteriosus and reduces oxygenation of blood in aorta.

Question 35

What happens to circulation after birthʔ

Answer 35

Ductus venosus close and degnerate to ligamentum venosum

Question 36

What happens to the foramen ovale after birthʔ

Answer 36

Blood returning from lungs increases pressure in the left atrium and flimsy septum primum is pushed against the sturdy septum secundum closing the foramen oval.
fossa ovalis in adult