Development Of The Heart

Question 0

What tissue is responsible for forming the horse-shoe shaped endothelial cord?

Answer 0

Splanchnic mesoderm cells

Question 1

The heart develops in what region?

Answer 1

Cardiogenic mesoderm

Question 2

Describe the formation of the primitive heart tube from the paired angioplasties cords.

Answer 2

The lateral sides of the horse shoe shaped endothelial tube fold in centrally and medially, approaching each other at the midline to fuse, forming a single heart tube.

Question 3

How does head folding in the 4th week reposition the heart and pericardial cavity? Prior to head fold

Answer 3

The heart is

• rostral to oropharyngeal membrane
• ventral to pericardial cavity

Question 4

How does head folding in the 4th week reposition the heart and pericardial cavity? Post head fold

Answer 4

The heart is:

• caudal to oropharyngeal membrane
• dorsal to pericardial cavity
• ventral to the foregut
• rostral to the septum transversum

Question 5

What is the fate of the dorsal mesocardium?

Answer 5

Degenerates to form the transverse pericardial sinus

Question 6

Heart folding/ formation of the cardiac loop forms in what days?

Answer 6

22-28

Question 7

Heart septation occurs in what days?

Answer 7

27-37

Question 8

What is the adult derivative of the sinus venosus right horn?

Answer 8

Sinus venarum

Question 9

What is the adult derivative of the sinus venosus left horn?

Answer 9

Coronary sinus

Question 10

What is the adult derivative of the primordial atrium?

Answer 10

Right and left auricles and portions of the atria

Question 11

What is the adult derivative of the primordial ventricle?

Answer 11

Only left ventricle

Question 12

What is the adult derivative of the proximal bulbus cordis?

Answer 12

Right ventricle

Question 13

What is the adult derivative of the conus cordis?

Answer 13

Outflow tract of ventricles

Question 14

What is the adult derivative of the truncus arteriosus?

Answer 14

Pulmonary trunk and aorta

Question 15

Describe how the cranial and caudal ends of the heart tube come to be repositioned in the formation of the cardiac loop

Answer 15

As the heart folds, it’s cranial end will shift centrally, caudally, and to the right. It’s caudal end will shift dorsally and superiorly.

Question 16

Describe the direction of blood flow through the tubular heart.

Answer 16

Sinus venosus-> through sinoatrial canal-> to primordial atrium-> through atrioventricular canal-> to atrioventricular sulcus-> to primordial ventricle-> through primary interventricular foramen -> to bulboventricular sulcus-> to bulbus cordis-> to aortic sac and pharyngeal arch aa.

Question 17

Describe the changes developing in the sinus venosus as blood flow to the heart gradually shifts to enter the right atrium

Answer 17

Originally the sinus venosus opens directly into the central dorsal wall of the primordial atrium. Blood flow to the heart gradually shifts to the right side due to the remodeling of the vitelline, umbilical, and anterior cardinal vv. As a result, the right horn of the sinus venosus becomes larger than the left.

Question 18

Describe the direction of blood flow through the primordial heart prior to septation

Answer 18

Sinus venosus-> primordial atrium-> AV canal -> left ventricle ( primordial ventricle)-> interventricular foramen-> right ventricle-> conus cordis-> truncus arteriosus-> aortic sac -> pharyngeal aa-> dorsal aortae

Question 19

What are the three paired veins that drain into the sinus venosus?

Answer 19

Vitelline vv, umbilical vv, common cardinal vv.

Question 20

From what structure is the smooth walled portion of the right atrium derived?

Answer 20

Sinus venosus rt horn

Question 21

From what structure is the smooth walled portion of the left atrium derived?

Answer 21

the primordial pulmonary v and portions of its branches

Question 22

Describe ventricular septal defect

Answer 22

• most common congenital heart defect (1:1000)
• failure of IV septum to completely form
• most cases it’s the membranous portion that fails to form

Question 23

Describe transposition of the great vessels

Answer 23

• occurs 1:2500
• the aorticopulmonary septum grows in straight instead of spiraling
• aorta arises from the right ventricle
• pulmonary trunk arises from left ventricle

Question 24

Describe Tetralogy of Fallot

Answer 24

The aorticopulmonary septum divides outflow tract unequally, resulting in stenosis of pulmonary trunk and overriding aorta. International house of pancakes 1. Interventricular septal defect 2. Hypertrophy of right ventricle 3. Overriding aorta 4. Pulmonary stenosis

Question 25

Describe the formation of the atrioventricular septum that develops to separate the atria from the ventricles

Answer 25

Dorsal and ventral endocardial cushions develop and fuse together, forming a AV septum that divides the AV canal into right and left AV canals.

Question 26

Describe the formation of the first step (septum primum) of the interatrial septum that develops to separate the right and left atria.

Answer 26

- Septum primum grows inferiorly to fuse with the endocardial cushions. The opening between the inferior edge of the septum & the endocardial cushions is the foramen primum. - Septum primum fuses with endocardial cushions, and foramen primum gradually closes off. As this happens, holes are forming in center of septum primum through apoptosis. These holes will unite to form the foramen secundum.

Question 27

Partitioning the primordial atrium involves what two septa that will fuse together to form the interatrial septum?

Answer 27

Septum primum (1st) and septum secundum (2nd)

Question 28

Describe the formation of the first step (septum secundum) of the interatrial septum that develops to separate the right and left atria.

Answer 28

- As holes in the septum primum coalesce to form the foramen secundum, a thicker septum secundum develops from the roof of the primordial atrium, slightly to the right of the septum primum. - Septum secundum grows inferiorly and develops an opening: the foramen ovale (oval foramen)

Question 29

Describe fetal circulation as compared to adult circulation.

Answer 29

Before birth: blood flows from right to left atrium through the foramen ovale After birth: foramen ovale closes off and there is no flow between atria

Question 30

What happens to the cranial portion of the septum primum?

Answer 30

It degenerates

Question 31

What happens to the caudal portion of the septum primum?

Answer 31

It forms the valve of the foramen ovale

Question 32

What is the fossa ovalis?

Answer 32

After birth, blood pressure within L atrium now exceeds that in the R atrium. This pushes the valve of foramen ovale against septum secundum and they fuse, closing off the foramen ovale. The foramen ovale closes off as a depression in the wall of the R atrium - the fossa ovalis (oval fossa)

Question 33

Describe the formation of the interventricular septum

Answer 33

The muscular portion if the IV septum grows crainally toward the AV septum, but does not fuse with it. The opening between the R and L ventricles is the IV foramen. The final portion of the IV septum is formed by the membranous portion.

Question 34

From what is the membranous portion of the septum derived?

Answer 34

Mesenchyme of the endocardial cushion tissue.

Question 35

Describe the formation of the aorticopulmonary septum that will divide the common outflow tract into two separate outflow tracts: the aorta (receiving blood from the left ventricle) and pulmonary trunk ( receiving blood from the right ventricle).

Answer 35

Aorticopulmonary septum fuses inferiorly with membranous IV septum, closing off blood flow between the ventricles and creating a separate outflow tract for each ventricle