Embryology Flashcards
Where does the heart come from?
At 3 weeks, myoblasts and blood islands are present in mesoderm from which heart develops
Name labelled structures of 3 week old embryo (pic)
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
What else forms at 3 weeks other than the beginnings of the heart?
Neural tissue forms from ectoderm
How does heart develop from lateral plate mesoderm?
Cells differentiate to form blood islands which will eventually form tube-like structure
Look at the structures at different stages of lateral folding (pic)
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How does the heart reach its final position?
Lateral and cranio-caudal (longitudinal folding)
Explain the process of lateral folding of the embryo (2)
- Edge of endoderm brought together by lateral folding forming gut tube
- Mesoderm also travels and fuses along midline forming very early heart tube
What is cardiac jelly?
Connective tissue associated with very early heart tube
Explain the process of longitudinal folding of the embryo (2)
- Heart tube with surrounding pericardial cavity will move ventrally and caudally
- Will eventually move into thorax through further folding of embryo
Look labelled structures at different stages of cranio-caudal folding
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Label the structures of the heart tube (pic)
A - sinus venosus B - atrium C - ventricle D - bulbus cordis E - Truncus arteriosus
What is the heart tube made up of?
5 dilatations that develop into adult heart structures
What does sinus venosus develop into? (2)
- Right horn develops into smooth part of right atrium
* Left horn retained on back of heart as coronary sinus
What does atrium develop into?
Trabeculated part of both atria
What does ventricle develop into?
Trabeculated part of LEFT ventricle
What does bulbus cordis develop into? (2)
- trabeculated part of right ventricle
* Outflow part of both ventricles
What does trunks arteriosus develop into? (2)
Divides into 2 to give:
- Aorta
- Pulmonary trunk
What is the direction of blood flow through the primitive heart?
Inflow at caudal end and outflow at cranial end
What structure is found at the caudal end?
First part is sinus venosus (right and left horns) which will unite and open into atrium
What structure is found at the cranial end?
Truncus arteriosus
What happens at day 23 of embryonic development?
Heart begins to loop and fold
Name structures on left lateral view of primitive heart
A - pericardium B - bulbus cordis C - pericardial cavity D - Aortic roots E - Primitive left atrium F - Left ventricle
Name structures on anterior view of primitive heart
A - trabeculated part of right ventricle B - conus cordia C - Primitive right atrium D - Truncus arteriosus E - Primitive left atrium F - Interventricular sulcus
Describe the looping and folding of the heart tube (4)
- Folds on itself forming U shape
- Atrium moves dorsally and cranially
- Ventricle moves left
- Bulbus cordis moves inferiorly, ventrally and to the right
What is truncus arteriosus connected to in primitive heart?
Right atrium
What separates the atria and ventricles on the surface? Within the primitive heart?
- Coronary groove (atrioventricular groove)
* AV groove appears as a deep invagination within the heart
Video on slide 9??
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Name the labelled structures of embryo (pic)
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
What does vasculature develop as? Example
Pairs that eventually fuse e.g. dorsal aortae becomes singular aorta
What vasculature is present within the yolk sac? What is the purpose of these vessels?
- Vitelline vessels (arteries and veins)
* Give rise to vessels that supply the gut
What is the expansion of the trunks arteriosus called? What is its purpose?
- Aortic sac
* Will give rise to important vessels (aortic arches)
What is the other name for aortic arches? How many pairs of vessels are associated with aortic arches?
- Pharyngeal arches
* 6 pairs of vessels (5th pair disappears but others give important contributions to vasculature)
What do the 6 pairs of pharyngeal/aortic arches do?
- 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
Look at diagrams illustrating development of aortic arches (pic)
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Explain the process of development of the aortic arches (4)
- 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
