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Human Structure - Block 2 > Embryology 6 > Flashcards

Embryology 6 Flashcards

1
Q

Describe the formation of the intraembryonic mesoderm during gastrulation.

A

cells migrate through primitive streak of embryo to form intraembryonic mesoderm

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2
Q

The intraembryonic mesoderm is partitioned into (3)

A

paraxial mesoderm

intermediate mesoderm

lateral mesoderm

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3
Q

What is the ultimate fate of the paraxial mesoderm? (2)

A

segmented into somites, which develop into bones of axial skeleton + associated musculature

develops into dermis

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4
Q

What is the ultimate fate of the intermediate mesoderm?

A

urogenital tract

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5
Q

The lateral mesoderm gets split into

A

two layers: parietal lateral mesoderm + visceral lateral mesoderm

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6
Q

Which embryonic structure develops into a “tube within a tube?”

A

lateral mesoderm

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7
Q

What embryonic structure gives rise to the cardiovascular system?

A

visceral portion of the lateral mesoderm

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8
Q

Label the following diagram.

A
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9
Q

When does the formation of the primitive heart begin?

A

week 3

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10
Q

What is the first step of primitive heart formation?

A

angioblastic cords form from lateral mesoderm

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11
Q

Describe how the angioblastic cords formed from lateral mesoderm further develop. (2)

A

angioblastic cords → 2 endothelial heart tubes

tubes fuse → primitive heart

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12
Q

What are the three layers of the primitive heart?

A

endocardium = lines cavity

myocardium = heart muscle

epicardium = outermost layer

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13
Q

All three layers of the primitive heart derive from what embryonic structure?

A

visceral portion of lateral mesoderm

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14
Q

Where is the primitive heart positioned relative to the foregut and oropharyngeal membrane?

A

ventral to foregut

caudal to oropharyngeal membrane

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15
Q

What five structures are distinguishable along the heart tube?

A

sinus venosus

primitive atrium

primitive ventricle

bulbus cordis

truncus arteriosus

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16
Q

When and how do heart contractions begin in the embryonic heart?

A

begin on day 21-22 as peristaltic waves in sinus venosus

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17
Q

What is the direction of embryonic heart blood flow by week 4?

A

unidirectional

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18
Q

Describe the pathway of embryonic blood flow in the primitive heart. (7)

A

blood enters heart through sinus venosus

enters primitive atrium

goes to primitive ventricle

exits primitive ventricle via bulbus cordis + truncus arteriosus

goes to aortic sac

goes to aortic arches

dorsal aorta

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19
Q

What structures feed blood into the sinus venosus of the embryonic heart? (3)

A

common cardinal veins

umbilical vein

vitelline vein

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20
Q

How does the embryo receive nutrients and oxygen?

A

from mother, via placental transfer

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21
Q

Describe the vascular resistance of the embryonic lung.

A

high vascular resistance, because the lungs are not yet filled with air

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22
Q

Describe blood supply to the lungs and liver in embryonic development.

A

lungs and liver don’t have much of a function in the embryonic stage, so they are bypassed in fetal circulation

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23
Q

Draw a diagram of fetal circulation after its heart has developed.

A
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24
Q

What are the two primary structures of the fetal heart that allow blood to bypass the lungs?

A

foramen ovale

ductus arteriosus

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25
Q

What are the three major changes to the cardiovascular system after birth?

A

lungs inflate = lower resistance to blood flow in lungs

foramen ovale closes

ductus arteriosus closes

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26
Q

What is the remnant of the ductus arteriosus in the adult heart?

A

ligamentum arteriosum

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27
Q

What is the effect of clamping the umbilical cord?

A

reroutes neonatal blood from oxygenation in placenta to oxygenation in aerated lungs

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28
Q

What is the remnant of the ductus venosus in the adult?

A

ligamentum venosum

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29
Q

What is the remnant of the umbilical vein in the adult?

A

ligamentum teres, a.k.a. round ligament of liver

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30
Q

What is the remnant of the umbilical artery/arteries in the adult?

A

medial umbilical ligaments

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31
Q

How many chambers are there in the primitive heart?

A

only 2 - one atrium and one ventricle

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32
Q

What does it mean for the heart to develop a double pump system?

A

right atrium and ventricle drive pulmonary circulation

left atrium and ventricle drive systemic circulation

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33
Q

What anchors the superior end of the primitive heart tube?

A

aortic arches

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34
Q

What anchors the inferior end of the primitive heart tube?

A

septum transversum

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35
Q

What is the embryonic precursor to the diaphragm?

A

septum transversum

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36
Q

What is the result of the rapid growth of the bulbus cordis and primitive ventricle in the embryonic heart?

A

formation of bulboventricular loop

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37
Q

Describe the positioning of the sinus venosus and bulbus cordis within the bulboventricular loop.

A

sinus venosus is dorsal and superior to bulbus cordis

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38
Q

What is the remnant of the bulboventricular loop in adults?

A

transverse pericardial sinus

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39
Q

What structures define the transverse pericardial sinus? (2)

A

anterior = aorta + pulmonary trunk

posterior = SVC + pulmonary veins

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40
Q

What is the structural function of the atrioventricular canal in the primitive heart?

A

connects primitive atrium to primitive ventricle

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41
Q

What structure connects the primitive atrium to the primitive ventricle in the primitive heart?

A

atrioventricular canal

42
Q

What are endocardial cushions?

A

outgrowths of dorsal + ventral walls of atrioventricular canal

43
Q

What eventually happens to the endocardial cushions?

A

grow until they fuse, at which point the atrioventricular canal is now separated into a right and left canal

44
Q

Draw a diagram of the steps that occur in the partitioning of the primitive atrium.

A
45
Q

Describe how the foramen ovale between the atria is closed after birth.

A

higher pressure in left atrium pushes septum primum against septum secondum, which closes foramen ovale

46
Q

What is the remnant of the foramen ovale after birth?

A

fossa ovalis

47
Q

Describe how the primitive ventricle is partitioned.

A

ridge from floor of common ventricle grows upward but a gap (interventricular foramen) persists

48
Q

What is the fate of the interventricular foramen?

A

membranous septum bridges interventricular foramen in week 7, which completely separates the ventricles

49
Q

Describe how the aorticopulmonary septum is formed. (2)

A

bulbar ridges grow out from bulbus cordis and extend into truncus arteriosus as truncal ridges

bulbar and truncal ridges spiral + fuse to produce aorticopulmonary spetum

50
Q

In adults, the bulbus cordis become

A

conus arteriosus (infundibulum)

51
Q

Describe the changes in the sinus venosus at week 7.

A

paired venous system (left and right common cardinal veins draining into sinus venosus) becomes unpaired w/ IVC and SVC

52
Q

Describe the significance of the right portion of the sinus venosus integrating into the right atrial wall.

A

the point of integration is the crista terminalis:

rough surface derives from primitive atrium

smooth surface derives from sinus venosus

53
Q

What is the crista terminalis?

A

the border between smooth and rough portions of the atrial wall

54
Q

What is the embryonic origin of the coronary sinus?

A

left portion of sinus venosus

55
Q

What is the function of the coronary sinus?

A

drains venous blood from heart muscle into right atrium

56
Q

From where do the pharyngeal arches receive the aortic arches?

A

common aortic sac

57
Q

The common aortic sac is a continuation of

A

the truncus arteriosus

58
Q

The third pair of aortic arches develops into (2)

A

the common carotid arteries (from the proximal portion of the third aortic arches)

the internal carotid arteries (from the distal portion of the third aortic arches)

59
Q

What is the embryonic origin of the common carotid arteries?

A

proximal portions of third aortic arches

60
Q

What is the embryonic origin of the internal carotid arteries?

A

distal parts of the third aortic arches

61
Q

The left fourth aortic arch becomes

A

the arch of the aorta

62
Q

The right fourth aortic arch becomes

A

right subclavian artery

63
Q

What is the embryonic origin of the arch of the aorta?

A

left fourth aortic arch

64
Q

What is the embryonic origin of the right subclavian artery?

A

right fourth aortic arch

65
Q

The left sixth aortic arch becomes

A

the left pulmonary artery (proximal portions)

ductus arteriosus (distal portions)

66
Q

What is the embryonic origin of the left pulmonary artery?

A

proximal portions of the left sixth aortic arch

67
Q

What is the embryonic origin of the ductus arteriosus?

A

distal portions of the left sixth aortic arch

68
Q

The right sixth aortic arch becomes

A

the right pulmonary artery (proximal portions)

nothing/degenerates (distal portions)

69
Q

What is the embryonic origin of the right pulmonary artery?

A

proximal portions of the right sixth aortic arch

70
Q

Describe the location of the recurrent laryngeal nerves in the embryonic heart, and how this location changes. (3)

A

initially supply sixth pair of branchial arches and loop around sixth pair of aortic arches

degeneration of 5th/6th aortic arches causes:

right recurrent laryngeal nerve to hook around right subclavian artery

left recurrent laryngeal nerve to stay anchored around ductus arteriosus

71
Q

What are cardiac shunts?

A

patterns of cardiac blood flow that deviate from normal pattern

72
Q

How do cardiac shunts typically occur?

A

when two spaces of the heart (e.g. R and L atria) are abnormally connected

73
Q

What is a left-to-right shunt? (2)

A

abnormal flow from systemic to pulmonary circuit

oxygenated blood is redirected to pulmonary circulation instead of going out to the periphery

74
Q

What is a right-to-left shunt? (2)

A

abnormal flow from pulmonary circuit to systemic circuit

deoxygenated blood enters systemic circulation

75
Q

What is cyanosis?

A

blue appearance of skin/mucous membranes due to lack of oxygen

76
Q

What is the long term effect of a left-to-right shunt?

A

right atrial and ventricular hypertrophy, because the pulmonary circulation has to pump an increased amount of blood

77
Q

What are three classes of congenital heart defects causing left-to-right shunts?

A

atrial septal defects

ventricular septal defect

patent ductus arteriosus

78
Q

Give four subtypes of atrial septal defects.

A

foramen secundum defects

foramen primum defects

sinus venosus atrial septal defects

common atrium

79
Q

If you have defects in the septa that divide the left and right atria in an embryo, what are the consequences?

A

no consequences [assuming this is prior to birth], because the atria are connected by the foramen ovale anyways

80
Q

What are foramen secundum defects?

A

patent foramen ovale due to defects in formation of septum primum or septum secundum

81
Q

What are foramen primum defects?

A

septum primum does not completely fuse with endocardial cushion, resulting in patent foramen primum

82
Q

When do the symptoms of a foramen secundum defect typically manifest?

A

do not manifest in childhood or early adulthood, but typically start at the age of 30

83
Q

What is a common symptom of foramen secundum defects?

A

pulmonary hypertension

84
Q

How are foramen secundum defects treated?

A

with an easy and low-mortality-rate surgery

85
Q

Foramen primum defects are often associated with what other heart defect?

A

cleft in one cusp of mitral valve

86
Q

Sinus venosus atrial septal defects result from

A

incomplete integration of the right sinus venosus into the right atrium

87
Q

A common atrium is the result of

A

complete failure to form septum primum and septum secundum

88
Q

Ventricular septal defects are caused by

A

incomplete growth of membranous or muscular part of interventricular septum

89
Q

Patent ductus arteriosus results from

A

failure of closure of ductus arteriosus after birth

90
Q

Give four examples of congenital heart defects that cause right-to-left shunts, with cyanosis.

A

persistent truncus arteriosus (PTA)

transposition of great arteries

tetralogy of Fallot (TF)

coarctation of aorta

91
Q

Persistent truncus arteriosus is the result of

A

the aorticopulmonary septum (separating aorta from pulmonary trunk) failing to form

92
Q

Transposition of great arteries occurs when

A

aorticopulmonary septum develops in a non-spiral manner, causing aorta to arise from right ventricle and pulmonary trunk arising from left ventricle

93
Q

How is the transposition of the great arteries treated?

A

it’s not compatible with life, unless there’s another shunt

94
Q

Tetralogy of Fallot is caused by

A

defects in development of aorticopulmonary septum and endocardial cushions

95
Q

List the four malformations associated with tetralogy of Fallot.

A

pulmonic stenosis

ventricular septal defect

overriding aorta

hypertrophy of right ventricle

96
Q

What is coarctation of the aorta?

A

narrowing of aorta proximally or distally to junction of aorta and ductus arteriosus

97
Q

What is the function of the ductus arteriosus?

A

connects pulmonary trunk to descending aorta

98
Q

Label the following diagram.

A
99
Q

Label the following diagram.

A
100
Q

Label the following diagram.

A

Human Structure - Block 2 (22 decks)

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