Embryology of heart

Question 1

Why does the heart form in embryo

Answer 1

Embryo can no longer supply it nutritional and oxygen requirements by diffusion
Heart develops as an efficient method of acquiring oxygen and nutrients from maternal blood and disposing of CO2 and waste products

Question 2

When the the heart first start to beat and first start to pump blood

Answer 2

First start to beat at 21-22 days and first start to pump blood at 24-25th days

Question 3

What is Vasculogenesis

Answer 3

Formation of new vascular channel by assembly of individual cell precursors called angioblasts
The major vessels, including dorsal aorta and cardinal veins are formed by this

Question 4

What is Angiogenesis

Answer 4

Formation of new vessels by budding and branching from pre-existing vessels

Question 5

How does the cardiogenic region form

Answer 5

Progenitor heart cells migrate through the primitive end streak during gastrulation to form mesoderm and migrate to splanchnic layer of lateral plate mesoderm
Forms horseshoe shaped cluster of cells called primary heart field
The cells are induced by the underlying endoderm to form cadriac myoblasts and blood islands that will form blood cells and vessels

Question 6

where do proginator heart cells originate

Answer 6

Epiblast, adjacent ti the cranial end in the primitive streak

Question 7

How does primitive heart tube form?

Answer 7

Lateral folding of the embryo brings the 2 endocardial tubes together to form a single endocardial tube

Question 8

What unites to form the unpaired descending aorta of the adult

Answer 8

right and left dorsal aortas

Question 9

why does the heart tube bend?

Answer 9

Bulbus cordis and ventricular parts elongate rapidly

But arterial and venous ends are fixed by pericardium

Question 10

how are the atria and ventricle partitioned

Answer 10

Endocardial cushions form on the dorsal and ventral walls of the AV canal
Endocardial cushions approach each other and fuse
Divides AV canal into right and left canal
partially seperating primordial atrium and primodial ventricle

Question 11

What is the septum primum

Answer 11

cresent-shaped membrane that divides common atrium into right and left

Question 12

What is the foramen primum

Answer 12

Gap between the edge of the septum primum and endocardial cushions
Allows blood to pass from left to right
Gets progressivly smaller and disappeares

Question 13

What do the small perforations in septum primum form

Answer 13

joined up to form foramen secundum

Question 14

What is septum secundum

Answer 14

A 2nd thick cresent shaped muscular fold
Adjacent to septum primum
Grows down and overlaps the foramen secundum

Question 15

How does the valve of the foramen ovale form

Answer 15

degradation of septum primum

Question 16

Why can blood flow from right to left through foramen ovale

Answer 16

right atrium at higher pressure than left

Question 17

what happens to foramen ovale after birth

Answer 17

fuses with septum secundum forming fossa ovalis

Question 18

what is mainly involved in dividing the primordial ventricle

Answer 18

Muscular interventricular septum

Question 19

How does the interventricualr foramen close

Answer 19

Formation of membranous interventricular septum, which merges with muscular interventricular septum

Question 20

What opens communication between ventricles and either pulmonary trunk or aorta

Answer 20

fusion of interventricular septum with aorticopulmonary septum

Question 21

How are the aorta and pulmonary trunk separated

Answer 21

Bulbar ridges and truncal ridges develop in the bulbis cordis and truncus arteriosus respectively
ridges grow and fuse at the same time
causes 180 spiralling of the outflow tract creating the sprial shaped septum that makes the seperation

Question 22

what are the 3 pairs fo vessels bringing venous blood to the heart

Answer 22

common cardinal veins
umbilical veins
vitelline veins

Question 23

where does the vitelline vein come from

Answer 23

from yolk sac and developing gastrointestinal tract

Question 24

how is common cardinal vein formed

Answer 24

formed by the union of the anterior and posterior cardinal veins

Question 25

where does the blood in the common cardinal vein come from

Answer 25

Posterior cardinal vein - trunk

Anterior cardinal vein - head region

Question 26

What happens when umbilical vein approaches the liver

Answer 26

Some blood enters liver sinusoids by mixing with portal vein
Rest passes through the ductus venosus behind the liver to enter the IVC
deoxygenated blood brought from lower limb in IVC mixes with the highly oxygenated blood from the placenta

Question 27

What happens to the oxygenated blood that enters the right atirum

Answer 27

mostly shunted through the foramen ovale

Question 28

What vessel moves the blood from the pulmonary trunk across to the decending aorta

Answer 28

ductus arteiosus