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Anatomy > G31 - Circulatory System Dev > Flashcards

G31 - Circulatory System Dev Flashcards

1
Q

How does the embryo get nourished during weeks 1-2 of development?

A

Diffusion from surrounding structures

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2
Q

When does the cardiovascular system begin to develop?

A

Week 3

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3
Q

What does the cardiovascular system develop from?

A

Three primordial: extraembryonic mesoderm, intraembryonic splanchnic mesoderm, neural crest

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4
Q

What does extraembryonic mesoderm form?

A

The vitelline vessels of the yolk sac, vessels of the umbilical cord, vessels in the chorion (fetal side of the placenta)

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5
Q

What does the intraembryonic splanchnic mesoderm form?

A

Cardinal veins, dorsal aortae, and primitive heart

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6
Q

What does the neural crest form?

A

Atrioventricular valves, aorta, pulmonary trunk

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7
Q

What are the 2 ways blood vessels can form? Describe each.

A

Vasculogenesis - mesenchyme differentiates into angioplasts beginning in the walls of the yolk sac and chorion and these angioblasts coalesce to form primitive blood vessels lined by endothelial cells
Angiogenesis - sprouting of new BVs from existing BVs

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8
Q

When does vasculogenesis begin?

A

Days 17-21

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9
Q

What forms blood vessel smooth muscle and connective tissue?

A

Surrounding mesoderm

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10
Q

What are the primitive blood vessels of the embryo?

A

Dorsal aortae and cardinal veins

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11
Q

What do the dorsal aortae do?

A

They are paired arteries that carry blood from the heart tube to the inferior parts of the embryo and they fuse together to form the descending aorta

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12
Q

What do the cardinal veins do?

A

They are paired vessels that return deoxygenated blood from the embryo to the heart tube

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13
Q

What do the vitelline veins and arteries do? What do they give rise to?

A

Veins (2) - return deox blood from yolk sac to heart tube, give rise to parts of IVC and hepatic portal vein
Arteries (2) - send ox blood to the yolk sac, fuse to form celiac trunk (foregut) and superior mesenteric artery (midgut)

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14
Q

What do the umbilical vessels do and what do they give rise to?

A

Arteries (2) - send deox blood from fetus to placenta, give rise to inferior mesenteric artery (hindgut)
Veins (2) - sends ox blood from placenta to fetal heart, not noted

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15
Q

When is development of the four chambers and valves of the heart completed?

A

By weeks 7-8

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16
Q

What tissue type is the cardiogenic area made of and where is it located?

A

Splanchnic mesoderm
Cranial to oropharyngeal membrane

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17
Q

What do biomolecular signals initiate around day 22/week 4 of dev?

A

Formation of paired endocardial tubes in the cardiogenic region of the splanchnic mesoderm

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18
Q

What happens during folding of the cardiogenic region?

A

The endocardial tubes migrate medially and ventrally into thoracic region anterior to gut tube and they fuse to form the primitive heart tube

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19
Q

What does the heart tube consist of?

A

Inner endocardial tube (gives rise to endocardium), surrounded by layer of myocardium and epicardium

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20
Q

What is cardiac jelly? What does it do?

A

Layer of ECM proteins secreted by myocardium that surround the endocardial tube

Supports the endothelial cells and contributes to the formation of the heart valves

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21
Q

What do the cells of the myocardium do?

A

They intrinsically contract and cause the heart tube to pulsate rhythmically and propel blood caudal to cranial through the tubes

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22
Q

Is the cardiac activity from the cells of the myocardium considered a heartbeat?

A

No! Because valves and conduction system have not yet formed

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23
Q

When is the SA node identifiable?

A

Week 7

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24
Q

What are the 5 regions (dilations) of the heart tube (from caudal to cranial blood flow)?

A
  1. Sinus venous (SV)
  2. Primitive atrium (A)
  3. Primitive ventricle (V)
  4. Bulbus cordis (BC)
  5. Truncus arteriosus (TA)
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25
Q

Where does the sinus venosus (SV) receive blood from?

A

Vitelline, cardinal, and umbilical veins

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26
Q

What does the primitive ventricle turn into and after what?

A

Primitive left ventricle
After the trabeculae carnae form

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27
Q

What does the atrioventricular (coronary) sulcus form between (but is external channel)?

A

The primitive atrium and primitive ventricle

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28
Q

What does the atrioventricular canal form between?

A

The primitive atrium and primitive ventricle (but is internal channel)

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29
Q

What does the caudal part of the bulbus cordis develop into?

A

Trabeculae carnae and primitive right ventricle l

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30
Q

What is the conus cordis?

A

The cranial part of the bulbus cordis

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31
Q

What does the truncus arteriosus (TA) do?

A

Connects to the paired R and L aortic arches

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32
Q

What are the venous parts of the heart tube?

A

Sinus venosus (SV) and primitive atrium (A)

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33
Q

What are the arterial parts of the heart tube?

A

Primitive ventricle (V), bulbus cordis (BC), truncus arteriosus (TA)

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34
Q

What happens around days 23-28/week 4 of development?

A

Cardiac looping begins:
1. Venous end of the heart moves cranially and dorsal to the arterial end (D-loop)
2. Venous part of heart (SV, A) forms the base of the heart
3. Primitive ventricle projects ventrally and the truncus arteriosus protrudes superiorly from pericardial sac

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35
Q

What happens around week 5?

A

Septation - heart tube begins to partition into 4 chambers

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36
Q

When are the pulmonary and systemic circulations functionally separate?

A

After birth

37
Q

What happens after cardiac looping?

A
  1. The truncus arteriosus (anterior) presses on the primitive atrium (posterior) which partially divides the chamber into primitive R and L atria. No septum has formed yet and the atria remain connected.
  2. Opening of the sinus venosus shifts from midline to right so that sinus venosus only opens into the developing right atrium
  3. Undivided atrioventricular canal shifts from L side to midline so that blood passes from primitive atria into both primitive ventricles
38
Q

What is the path of blood flow through the developing heart?

A

Sinus venosus —> primitive R atrium —> primitive L atrium —> atrioventricular canal —> primitive L ventricle —> primitive R ventricle —> conus cordis —> truncus arteriosus —> R/L aortic arches

39
Q

How do the heart valves form?

A
  1. Neural crest cells migrate into cardiac jelly surrounding endocardial tube and make tissue swell (endocardial cushions)
  2. Endocardial cushions fuse which divides the atrioventricular canal into R and L atrioventricular openings
  3. Tricuspid and bicuspid (mitral) valves arise from endocardial cushion tissue
40
Q

What does endocardial cushions tissue give rise to?

A

Atrioventricular valves (tricuspid and bicuspid)

41
Q

How does definitive right atrium form?

A
  1. Opening between the R atrium and sinus venosus enlarges
  2. R horn of sinus venosus incorporates into wall of definitive R atrium
42
Q

What part of the adult right atrium came from the sinus venosus? What part came from the primitive right atrium?

A

Smooth posterior wall
Pectinate muscles

43
Q

What does the L horn of the sinus venosus turn into? What is the structure’s function?

A

The coronary sinus - drains into the R atrium

44
Q

How does the definitive left atrium form?

A

Primitive L atrium extends vein buds out to the developing lungs, vein buds branch repeatedly and enlarge to become pulmonary veins, and the proximal parts of the pulmonary veins form the wall of the definitive L atrium

45
Q

What is the remnant of the primitive L atrium?

A

L auricle

46
Q

What is a remnant of the primitive R atrium?

A

R auricle

47
Q

What begins around day 32/week 5?

A

The interatrial septum begins forming

48
Q

Describe the steps of formation of the interatrial septum.

A
  1. Around week 5, the septum primum grows from the roof of the primitive atrium toward the endocardial cushions
  2. It fuses with the endocardial cushions and closes the foramen primum, separating the R and L atria
  3. Just prior to closure, a new opening (foramen secundum) appears at the cranial part of the septum primum and blood can still flow from the R atrium to L because of this
  4. Around week 7, the septum secundum grows inferiority from the atrial roof on the right side of the septum primum
  5. The septum secundum grows, covers the foramen secundum, except for a oval-shaped opening that remains called the foramen ovale
49
Q

How does blood flow through the layers of the interatrial septum and why?

A

From the R atrium —> foramen ovale —> foramen secundum —> L atrium
The septum primum overlaps the foramen ovale so that the two openings (foramen secundum and foramen ovale) are not in direct line with each other

50
Q

Which compartment of the heart has higher pressure at birth and what does this pressure differential cause?

A

The L atrium (compared to the R atrium) caused by the first breaths taken at birth - pressure differential forces the septum primum against the septum secundum and they fuse together typically one year after birth to close the openings between the R and L atria

51
Q

What is the fossa ovalis an embryological remnant of? Where can you find it?

A

Foramen ovale
Interatrial septum in adult heart

52
Q

Where are the potential locations that atrial septal defects may occur?

A
  1. Foramen secundum (most common)
  2. Foramen primum
  3. Sinus venosus (rare)
  4. Coronary sinus (rare)
53
Q

What does an atrial septal defect do? What are the effects of this?

A

Allows blood to shunt between the R and L atria —> mixes oxygenated and deoxygenated blood and overloads lungs with blood potentially leading to pulmonary arterial hypertension, permanent damage to the pulmonary vessels, right ventricle hypertrophy, and heart failure

Also increased susceptibility to infection

54
Q

What is patent foramen ovale (PFO)?

A

When the foramen ovale fails to close and blood can leak through the atria

55
Q

How is the patent foramen ovale (PFO) functionally closed normally?

A

Higher left side arterial pressure

56
Q

What does the definitive L ventricle arise from?

A

The primitive ventricle

57
Q

What does the definitive R ventricle arise from?

A

The caudal part of the bulbus cordis

58
Q

When does the primitive ventricle begin partitioning?

A

Around week 4 of development

59
Q

Describe the steps of formation of the interventricular septum.

A
  1. Muscular ridge between the primitive ventricles and heart apex grows cranially toward the atrioventricular endocardial cushions
  2. Muscular part of the septum eventually completely separates the primitive ventricles except for a small area close to the AV valves
60
Q

What overlaps the outflow of both primitive ventricles and also forms their superior pats?

A

The conus cordis

61
Q

What divides the truncus arteriosus (TA) and conus cordis (CC)?

A

Aorticopulmonary septum

62
Q

Describe the steps the lead to the formation of the aorticopulmonary septum.

A
  1. Neural crest cells migrate into the paired truncal and bulbar ridges in the walls of the truncus arteriosus and conus cordis
  2. The truncal and bulbar ridges project into the lumen of the TA and CC and fuse together to form the aorticopulmonary septum which divides the lumen longitudinally
  3. The aorticopulmonary septum spirals as it grows caudally
63
Q

The aorticopulmonary septum divides the TA into what and the CC into what?

A

TA: The ascending aorta and the pulmonary trunk
CC: right and left side

64
Q

What are the left and right sides of the conus cordis continuous with and what do they form?

A

L: ascending aorta, superior part of the definitive L ventricle
R: pulmonary trunk, superior part of the definitive R ventricle

65
Q

Why is it common to see facial and cardiac anomalies in the same individual?

A

Because neural crest cells contribute to both cardiac and craniofacial development

66
Q

What does the aorticopulmonary septum eventually fuse with?

A

The muscular part of the interventricular septum, forming the membranous part of the interventricular septum

67
Q

What does the aorticopulmonary septum bisect and eventually create?

A

A 4-cusp valve present in the truncus arteriosus, which creates the pulmonary and aortic valves (3 cusps each)

68
Q

How are ventricular septal defects caused? What do they lead to?

A

Defects in the superior membranous part of the interventricular septum due to abnormalities in partitioning the TA and CC —> causes oxygenated blood to be shunted from the L side of the heart to the R —> pulmonary hypertension

69
Q

What does persistent truncus arteriosus result from and what effects does it lead to? Can it be treated?

A

Failure of the aorticopulmonary septum to develop so the TA and CC don’t divide
Results in superior ventricular septal defect (VSD) —> mixed blood from both ventricles being shunted around —> cyanosis due to inadequate oxygenation
Can be treated via surgical correction in infancy

70
Q

What is cyanosis? What condition could cause it?

A

Bluish tint to skin, lips, nails due to inadequate oxygenation.
Persistent truncus arteriosus that leads to superior ventricular septal defect (VSD)

71
Q

How does transposition of the great arteries (defect) occur? What does it lead to?

A

The aorticopulmonary septum descends linearly rather than spiraling which causes the aorta to originate from the the R ventricle (should be L) and the pulmonary trunk to originate from the L ventricle (should be R)

Leads to oxygenated blood being pumped to lungs and deoxygenated blood being pumped to body and it should be the opposite

72
Q

How will a fetus survive if they have transposition of their great arteries?

A
  1. If they have a septal defect as well (atrial or ventricular)
  2. If their ductus arteriosus fails to close as well

Both of these conditions allow deox and ox blood to mix so that the fetus can get oxygen

73
Q

What is tetralogy of fallout and how is it caused? What defects does it lead to? Can it be treated?

A

Combo of 4 cardiac defects

Caused by unequal division of the TA and CC by the aorticopulmonary septum

Defects: 1.) PROVe (pulmonary trunk stenosis and abnormally large ascending aorta, right ventricular hypertrophy due to high R ventricle pressure from pulmonary trunk stenosis, overriding aorta (overlaps both ventricles), and ventricular septal defect); 2.) Cyanosis

Yes, surgically

74
Q

What are the large arteries in the heart that develop during the embryological stages? What do they supply?

A

6 pairs of aortic arch arteries that turn into:
1. Aortic arch
2. R/L common carotid
3. R/L subclavian
4. R brachiocephalic

Supply the head, neck, and upper extremities

75
Q

What do the 6 pairs of aortic arches arise from? What do they connect to? What are they associated with?

A

The truncus arteriosus
The ipsilateral dorsal aorta
The paired pharyngeal arches that give rise 4to structures in head/neck

76
Q

What does the L side aortic arch form? What does it do?

A

The ductus arteriosus - connects the arch of the aorta and the left pulmonary artery

77
Q

Why does the L recurrent laryngeal n loop under the aorta instead of the subclavian artery (which occurs on the R)?

A

The presence of the ductus arteriosus and transformation of the aortic arches which takes up space

78
Q

What is the ligamentum arteriosum?

A

Embryological remnant of the ductus arteriosis that constricted at birth and filled with connective tissue

79
Q

What can lead to anomalies of the great vessels?

A

Errors in regression and fusion in the aortic arch arteries

80
Q

Describe the flow of prenatal circulation.

A
  1. oxygen and nutrient depleted blood with waste products drains from fetus via the R/L umbilical arteries into the placenta where gas/nutrient exchange occurs
  2. Oxygenated/nutrient rich blood returns to the fetus via the single umbilical vein
  3. 3 shunts divert more oxygenated and nutrient-rich blood to the cranial half of the developing body: 1.) foramen ovale which shunts oxygenated blood from the R to L atrium, 2.) ductus venosus which connects the umbilical vein to the IVC and allows incoming liver blood to bypass liver capillaries, 3.) ductus arteriosus which shunts blood between the L pulmonary artery and arch of the aorta
  4. Have highly oxygenated blood from the IVC entering the R atrium —> lungs
  5. Have highly oxygenated blood in the L atrium entering the L ventricle and pumped to ascending aorta —> rest of body
81
Q

Describe how highly oxygenated blood enters the R atrium? Where does it end up?

A
  1. Oxygenated blood returning to the fetus enters the R atrium via the IVC
  2. Some IVC blood passes through the openings in the interatrial septum to the L atrium AND some IVC blood also mixes with small amount of deox blood from the SVC in the R atrium
  3. Small amount of mixed blood passes through tricuspid valve into R ventricle
  4. From R ventricle goes to pulmonary trunk —> pulmonary arteries —> developing lungs
  5. Blood in lungs shunted from pulmonary arteries to arch of aorta via ductus arteriosus
82
Q

Describe how highly oxygenated blood in the L atrium is sent to the rest of the body.

A
  1. Enters left ventricle and then pumped into the ascending aorta
  2. Most aortic arch blood distributed to the cranial half of the body via the brachiocephalic trunk, L common carotid, and L subclavian arteries (BCS)
  3. Remainder of blood in aortic arch mixes with reduced oxygen blood from the ductus arteriosus and distributes to the caudal half of the fetus
83
Q

What happens to fetal circulation at the time of baby’s first breath?

A
  1. Resistance in the pulmonary circuit decreases —> pressure drop in R atrium and ventricle
  2. L side of heart now has greater pressure than R
  3. Increased L atrium pressure pushes the septum primum against the septum secundum which closes the foramen ovale and foramen secundum
  4. Septum primum and secundum fuse together to create the interatrial septum with no opening
  5. Fossa ovalis is now in place of foramen ovale
  6. Umbilical vessels and shunts close
84
Q

Outline the steps of closure of the umbilical vessels and shunts after the baby is born.

A
  1. Ductus arteriosus constricts and its lumen is replaced with fibrous connective tissue, creating the ligamentum arteriosum, until it fully closes around 8 weeks-1 year after birth
  2. Ductus venosus collapses and closes by day 7 postnatal and becomes the ligamentum venosum
  3. The umbilical arteries constrict and their lumen fill with fibrous connective tissue, creating the medial umbilical ligaments of the anterior abdominal wall, but the proximal parts branch to urinary bladder (superior vesicle arteries)
  4. The umbilical veins collapse and fill with fibrous connective tissue, becoming the round ligament of the liver (ligamentum teres hepatic) which is in the inferior margin of the falciform ligament of the liver
85
Q

What is the ligamentum venosum an embryological remnant of?

A

Ductus venosus

86
Q

What is patent ductus arteriosus? What might it lead to? What infant population is it common in? Is there treatment?

A

Condition where ductus arteriosus fails to close —> can lead to pulmonary hypertension and heart enlargement

Premature infants and those whose mothers were infected with rubella

Treat with ibuprofen/indomethacin to close the duct

87
Q

Which embryonic tissue develops into the definitive endocardium of the adult heart?

A

Splanchnic mesoderm

88
Q

The part of the right ventricle with trabeculae develops from which of the following structures?

A

Caudal part of the bulbus cordis

Anatomy (9 decks)

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