Cardiogenesis/Vasculogenesis

Question 1

What marks the beginning of Vasculogenesis in the developing embryo?

What (2) types of cells primarily arise?

Answer 1

Blood islands (mesoderm aggregations) form in the Yolk Sac (additional sites of blood cells/vessels form in the placenta, umbilical cord, and embryo proper).

Blood islands segregate into Hemoblasts (future blood cells) and Endothelial cells (Forms the lining of the blood vessels).

Question 2

What are the (4) Major primarily blood vessels that arise?

From where do they arise?

Answer 2

(2) Endocardial tubes (L&R) and (2) Dorsal Aorta (L&R); All extending the full length of the embryo.

Endocardial tubes are derived from Splanchnopleuric mesoderm, while the Dorsal Aortae are from Dorsal Mesenchyme near the Notochord

Question 3

Where do the (4) major primary blood vessels converge; what is the name of this region; and what is it’s significance?

Answer 3

They converge at the Cardiogenic Region (horseshoe-shaped), located cranial to the Neural plate and buccopharyngeal membrane. This region will give rise to most of the tissues of the Heart.

Question 4

How does lateral folding effect the Endocardial tube location? What does this facilitate?

Answer 4

Endocardial tubes move from Lateral to the Endoderm to a position Ventral to the Gut tube

This facilitates the fusion of the endocardial tubes to form endothelial lining (part of the Tunica Intima) of the developing Heart.

Question 5

What affect does Cranial folding have on the Cardiogenic region?

Answer 5

During cranial folding, the fusing endocardial tubes are pulled (ventrally, caudally, then dorsally) into the thorax, dragging along the anterior portions of the Dorsal Aortae.

-Results in a single heart tube in the thoracic region

Question 6

Following Cranial folding, What are the (3) major types of veins and where do they converge?

Answer 6

1. L&R Common Cardinal Veins
2. Villetine Vein
3. Umbilical Vein

All veins converge at the Sinus Venosus, located at the caudal end of the developing heart tube

Question 7

What is the Aortic sac?

Answer 7

The Aortic Sac is a single tube at the cranial end of the fused endocardial tubes (heart tube) which gives rise to the First Aortic Arches (L&R), continuing on as the L&R Dorsal Aortae

Question 8

How many aortic arches arise and how are they oriented?

Answer 8

There are (5) aortic arches (numbered 1, 2, 3, 4, & 6) which travel laterally and dorsally around the developing Gut tube forming a cage-like structure.

Question 9

What does the 1st arch become?

What does the 2nd arch become?

Answer 9

• Both the L&R 1st arch become Maxillary arteries within the Jaw
• Both the L&R 2nd arch become Stapedial arteries within the ear, however these arteries are only present during development of the ear and are not present at birth/adult

Question 10

What do the 3rd arches develop into?

Answer 10

Both the L&R 3rd arches develop into the L&R Common Carotid

• The Internal and External Carotids sprout from the Common Carotids

Question 11

How do the 4th arches develop?

Answer 11

Left 4th Arch: Becomes part of the Aortic arch

Right 4th Arch: Becomes part of the Subclavian artery

Question 12

How do the 6th arches develop?

Answer 12

Left 6th Arch: Becomes the Ductus Arteriosus; The pulmonary artery sprouts from the 6th arch

Right 6th Arch: Lost/ Disappears

Question 13

Maxillary Arteries are derived from what arches?

Answer 13

L&R 1st Arch

Question 14

Stapedial arteries are derived from which arches?

Answer 14

L&R 2nd Arches

Question 15

The Common Carotids are derived from which arches?

Answer 15

L/R 3rd arches

Question 16

The internal Carotid is derived from which vessels?

Answer 16

L&R 3rd arch + segment of the Dorsal Aorta

Question 17

The External Common Carotids are derived from which vessels?

Answer 17

L&R Common Carotid

Question 18

The Right Subclavian Artery is derived from which vessels?

Answer 18

Right 4th arch

Right 7th Intersegmental

Right Dorsal Aorta

Question 19

The Left Subclavian Artery is derived from which vessels?

Answer 19

Left 7th Intersegmental

Question 20

The Brachiocephalic artery is derived from which vessels?

Answer 20

Portion of the Aortic Sac

Question 21

The Aortic Arch is derived from which vessels?

Answer 21

Left 4th arch

Left Dorsal Aorta segment

portion of the Aortic Sac

Question 22

The Ascending aorta is derived from what vessels?

Answer 22

Portion of the Aortic Sac

Question 23

The Descending Aorta is derived from which vessels?

Answer 23

Left Dorsal Aorta Segment

Question 24

The Ductus Arteriosus is derived from which vessels?

Answer 24

Left 6th Arch

Question 25

The Pulmonary Trunk is derived from which vessels

Answer 25

The 6th arch\*

Question 26

What are the (3) Initial major veins and what are their functions?

Answer 26

1. Common cardinal veins: - Anterior ccv drains the top portion of the embryo - Inferior ccv drains the bottom portion of the embryo 2. Vitelline Vein: Drains the GI tract 3. Umbilical vein: Oxygenated blood returning from the placenta All of which converge at the Sinus venosus; Left side veins converge at the Left horn while right side converge at the Right Horn

Question 27

What is the function of the lymphatic system and what are the major ducts during development? How do they change from symmetrical to asymmetrical?

Answer 27

The lymphatic system is responsible for draining the water from tissues that is moved into the tissues by the cardiovascular system. Right & Left Lymphatic ducts connect at the midline; Right Superior and Left Inferior ducts disappear, resulting in a Main Thoracic Duct beginning on the right, crossing the midline, and ending on the left.

Question 28

What are the (2) Mesodermal layers that give rise to cardiac and vascular tissues?

Answer 28

1. Splanchnic Mesoderm 2. Somatic Mesoderm

Question 29

Which of the Cardiac/Vascular tissues are derived from Splanchnic Mesoderm?

Answer 29

1. Endocardial Tubes (thus, Heart) 2. Visceral Pericardium (Epicardium)

Question 30

Which of the Cardiac/ vascular tissues are derived from somatic Mesoderm?

Answer 30

Dorsal Aorta Parietal Pericardium

Question 31

What is the Dorsal Mesocardium?

Answer 31

The Dorsal Mesocardium is connective tissue that connects the heart to the dorsal body wall (similar to dorsal mesentery)

Question 32

What is the Transverse Pericardial Sinus?

Answer 32

The Transverse Pericardial Sinus is the space created by the degradation of the Dorsal Mesocardium.

Question 33

What are the major subdivisions of the Heart prior to folding?

Answer 33