Heart and Embryology

Question 1

What 2 pleura surround the heart?

Answer 1

-Visceral pericardium (epicardium)
-Parietal pericardium

Question 2

List the 5 layers that are passed through if you move from the heart out towards the lungs

Answer 2

1. Visceral pericardium
2. Pericardial cavity
3. Parietal pericardium
4. Connective tissue layer
5. Mediastinal pleura

Question 3

In which species does the left coronary artery go down the subsinuosal groove?

Answer 3

Dogs and ruminants

Question 4

In which species does the right coronary artery go down the subsinuosal groove?

Answer 4

Horses and pigs

Question 5

Is the paraconal groove more cranial or caudal?

Answer 5

Cranial

Question 6

Is the subsinuosal groove more cranial or caudal?

Answer 6

Caudal

Question 7

What is a primary difference between the left ventricle and the right ventricle?

Answer 7

Left ventricle contains a much thicker muscular wall, while the right ventricle is made of thinner muscle

Question 8

Why does the left ventricle contain more muscle than the right ventricle?

Answer 8

Because the left ventricle has to push blood systemically; the right ventricle only has to pump to the lungs

Question 9

What is the ossa cordis?

Answer 9

A fibrous structure of the heart that supports the valves. Sometimes becomes ossified in cattle

Question 10

What is the function of the septomarginal band?

Answer 10

Provides a conduit for conductive fibres so contraction is more even across muscles

Question 11

Where is the SA Node located in the heart?

Answer 11

In the terminal crest (under the cranial vena cava)

Question 12

What is the function of the intervenous tubercle?

Answer 12

Directs blood over the AV valve and into the right ventricle from the superior vena cava

Question 13

What is the fossa ovales?

Answer 13

The remnant of the foramen ovale that closes once the animal is born

Question 14

How would heart failure appear on a radiograph?

Answer 14

The heart would appear enlarged due to dilations in the atria

Question 15

What are the 3 layers of a trilaminar embryo?

Answer 15

Ectoderm
Mesoderm
Endoderm

Question 16

What are the 4 components of an early embryo heart?

Answer 16

Truncus arteriosus
Ventricle
Atria
Sinus venosus

Question 17

What to the aortic arches eventually branch off of during development?

Answer 17

Truncus arteriosus

Question 18

What are the steps of the division of the atrium?

Answer 18

Endocardial cushions begin to form, which then extend inward towards each other forming the atrio-ventricular canal. Once both sides meet each other, they form the septum intermedium and separate the right and left atrio-ventricular openings

Question 19

What part of the heart is the sinus venosus incorporated into?

Answer 19

The right atrium. Contributes to the left coronary sinus in the adult heart

Question 20

What structure forms the valve of the foramen ovale?

Answer 20

Septum primum

Question 21

In what region do the aortic arches form?

Answer 21

Pharyngeal region

Question 22

What happens to the 1st aortic arch as the others start developing?

Answer 22

It gets lost

Question 23

What does aortic arch 3 form?

Answer 23

-Common carotids
-External carotids
-Internal carotids

Question 24

What does aortic arch 4 form?

Answer 24

-Aorta
-Right and left subclavian arteries
-Brachiocephalic trunk

Question 25

What does aortic arch 6 form?

Answer 25

-Pulmonary trunk
-Left and right pulmonary arteries

Question 26

In dogs, what do the right and left subclavian arteries branch from?

Answer 26

Right: Brachiocephalic trunk
Left: Aorta

Question 27

What do the carotids branch from in all species?

Answer 27

Brachiocephalic trunk

Question 28

In cows and horses, what do the left and right subclavian arteries branch from?

Answer 28

Both branch from the Brachiocephalic trunk

Question 29

What structure does the ductus arteriosus become in an adult?

Answer 29

Ligamentum arteriosum

Question 30

What does the right recurrent laryngeal nerve loop under?

Answer 30

The right subclavian artery

Question 31

What does the left recurrent laryngeal nerve loop under?

Answer 31

The ligamentum arteriosum

Question 32

How would pathology of the heart affect the recurrent laryngeal nerves?

Answer 32

If the heart is enlarged, it would put pressure on the LEFT recurrent laryngeal nerve. The RIGHT recurrent laryngeal nerve would be unaffected as it is located cranial to the heart

Question 33

What can happen if the heart fails to migrate during development?

Answer 33

Since the heart develops in the pharyngeal region, if it fails to migrate caudally then the animal can be born with their heart in their neck. This is not fatal, but it greatly reduces protection of the heart.

Question 34

What structures are only present in a fetus?

Answer 34

Ductus venosus (liver)
Ductus arteriosus
Foramen ovale

Question 35

Describe the path of blood through fetal circulation (sorry)

Answer 35

-Deoxygenated blood from body goes into right atrium and the right ventricle
-Pumped into pulmonary trunk, through ductus arteriosus, and into aorta to bypass the lungs
-Goes into umbilical arteries and to placenta for oxygen/nutrients/waste
Umbilical vein carries blood to liver in ductus venosus and back to heart
-Blood enters right atrium and goes through foramen ovale into left atrium
-Goes into left ventricle and pumped to body

Question 36

What organs does the placenta function as for a fetus?

Answer 36

Lungs
GI tract
Kidneys

Question 37

What occurs when the fetus is born?

Answer 37

-Umbilical arteries and vein closed off
–> this reduces pressure in caudal vena cava, increasing pressure in left atria and pushes foramen ovale closed
-Lungs expand and reduce circulatory resistance to blood flow in pulmonary circulation
-Muscles around ductus arteriosus constrict and close it, making it forms the ligamentum arteriosum

Question 38

Why can it be normal to hear murmurs in neonates?

Answer 38

Because it takes some time for the ductus arteriosus and foramen ovale to fully close