Embryology

Question 1

Where does the heart come from?

Answer 1

At 3 weeks, myoblasts and blood islands are present in mesoderm from which heart develops

Question 2

Name labelled structures of 3 week old embryo (pic)

Answer 2

A - myoblasts and blood islands 
B - neural plate
C - edge of amnion
D - primitive node
E - primitive streak 
F - intraembryonic cavity 
G - splanchnic mesoderm layer 
H - blood islands
I - endoderm 
J - pericardial cavity 
K - ectoderm
L - allantois
M - connecting stalk 
N - notochord 
O - cariogenic field

Question 3

What else forms at 3 weeks other than the beginnings of the heart?

Answer 3

Neural tissue forms from ectoderm

Question 4

How does heart develop from lateral plate mesoderm?

Answer 4

Cells differentiate to form blood islands which will eventually form tube-like structure

Question 5

Look at the structures at different stages of lateral folding (pic)

Answer 5

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Question 6

How does the heart reach its final position?

Answer 6

Lateral and cranio-caudal (longitudinal folding)

Question 7

Explain the process of lateral folding of the embryo (2)

Answer 7

• Edge of endoderm brought together by lateral folding forming gut tube
• Mesoderm also travels and fuses along midline forming very early heart tube

Question 8

What is cardiac jelly?

Answer 8

Connective tissue associated with very early heart tube

Question 9

Explain the process of longitudinal folding of the embryo (2)

Answer 9

• Heart tube with surrounding pericardial cavity will move ventrally and caudally
• Will eventually move into thorax through further folding of embryo

Question 10

Look labelled structures at different stages of cranio-caudal folding

Answer 10

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Question 11

Label the structures of the heart tube (pic)

Answer 11

A - sinus venosus 
B - atrium 
C - ventricle 
D - bulbus cordis 
E - Truncus arteriosus

Question 12

What is the heart tube made up of?

Answer 12

5 dilatations that develop into adult heart structures

Question 13

What does sinus venosus develop into? (2)

Answer 13

• Right horn develops into smooth part of right atrium

* Left horn retained on back of heart as coronary sinus

Question 14

What does atrium develop into?

Answer 14

Trabeculated part of both atria

Question 15

What does ventricle develop into?

Answer 15

Trabeculated part of LEFT ventricle

Question 16

What does bulbus cordis develop into? (2)

Answer 16

• trabeculated part of right ventricle

* Outflow part of both ventricles

Question 17

What does trunks arteriosus develop into? (2)

Answer 17

Divides into 2 to give:

• Aorta
• Pulmonary trunk

Question 18

What is the direction of blood flow through the primitive heart?

Answer 18

Inflow at caudal end and outflow at cranial end

Question 19

What structure is found at the caudal end?

Answer 19

First part is sinus venosus (right and left horns) which will unite and open into atrium

Question 20

What structure is found at the cranial end?

Answer 20

Truncus arteriosus

Question 21

What happens at day 23 of embryonic development?

Answer 21

Heart begins to loop and fold

Question 22

Name structures on left lateral view of primitive heart

Answer 22

A - pericardium 
B - bulbus cordis 
C - pericardial cavity 
D - Aortic roots 
E - Primitive left atrium 
F - Left ventricle

Question 23

Name structures on anterior view of primitive heart

Answer 23

A - trabeculated part of right ventricle 
B - conus cordia 
C - Primitive right atrium 
D - Truncus arteriosus
E - Primitive left atrium 
F - Interventricular sulcus

Question 24

Describe the looping and folding of the heart tube (4)

Answer 24

• Folds on itself forming U shape
• Atrium moves dorsally and cranially
• Ventricle moves left
• Bulbus cordis moves inferiorly, ventrally and to the right

Question 25

What is truncus arteriosus connected to in primitive heart?

Answer 25

Right atrium

Question 26

What separates the atria and ventricles on the surface? Within the primitive heart?

Answer 26

• Coronary groove (atrioventricular groove)

* AV groove appears as a deep invagination within the heart

Question 27

Video on slide 9??

Answer 27

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Question 28

Name the labelled structures of embryo (pic)

Answer 28

A - Vitelline vein 
B - Heart
C - aortic sac
D - Internal carotid artery 
E - Aortic arches (II and III)
F - Anterior cardinal vein 
G - common cardinal vein 
H - dorsal aorta 
I - posterior cardinal vein 
J - Chorionic villus 
K - Chorion 
L - Umbilical vein and artery 
M - Vitelline artery

Question 29

What does vasculature develop as? Example

Answer 29

Pairs that eventually fuse e.g. dorsal aortae becomes singular aorta

Question 30

What vasculature is present within the yolk sac? What is the purpose of these vessels?

Answer 30

• Vitelline vessels (arteries and veins)

* Give rise to vessels that supply the gut

Question 31

What is the expansion of the trunks arteriosus called? What is its purpose?

Answer 31

• Aortic sac

* Will give rise to important vessels (aortic arches)

Question 32

What is the other name for aortic arches? How many pairs of vessels are associated with aortic arches?

Answer 32

• Pharyngeal arches

* 6 pairs of vessels (5th pair disappears but others give important contributions to vasculature)

Question 33

What do the 6 pairs of pharyngeal/aortic arches do?

Answer 33

• 1 - Maxillary artery
• 2 - stapedial artery
• 3 - common carotid artery and first part of internal carotid artery
• 4 - right subclavian artery and part of aortic arch
• 5 - absent
• 6 - pulmonary artery and ductus arteriousus on left

Question 34

Look at diagrams illustrating development of aortic arches (pic)

Answer 34

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Question 35

Explain the process of development of the aortic arches (4)

Answer 35

• Right dorsal aorta fuses with the left to form the aorta
• As later aortic arches form, the others begin to regress (e.g. arches 1 and 2 disappear when 3 is forming)
• 3rd arch gives common carotid arteries and ICA, ICAs connect to dorsal aortae
• Arches continue to form and regress until only the arch of the aorta is left