Embryology Of The Respiratory And Cardiovascular Systems Flashcards

1
Q

What occurs during early lung development?

A

Development of the lung primordium and primary lung bud formation.

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2
Q

What occurs during late lung development?

A

Bronchial branching and cytodifferentiation.

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3
Q

When does development of the respiratory system begin?

A

Week 4.

The laryngeotracheal diverticulum is first created.

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4
Q

What gene positions specifies the respiratory diverticum and also positions the lung on the esophagus?

A

TBX4

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5
Q

What dermal layer is the lining of the lungs composed of?

A

Endoderm.

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6
Q

The outgrowth of the foregut spreads to what dermal layer?

A

Splanchnic mesoderm

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7
Q

What divides the trachea and the esophagus?

A

Tracheoesophageal septum.

The laryngeotracheal diverticulum grows distally and is separated from the esophagus dorsally by this septum.

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8
Q

What is the most common formation of the tracheoesophageal septum?

A

Teachoesophageal fistula.

It results from an abnormal communication between the trachea and esophagus.

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9
Q

What causes a tracheoesophageal fistula?

A

Improper formation of trachoesophageal septum.

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10
Q

Polyhydramnios (too much amniotic fluid) can be a sign that there is a tracheoesophagel fistual or esophagel atresia. How is this so?

A

Because the fetus is not swallowing amniotic fluid.

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11
Q

Why is polyhyramnios?

A

A high volume of amniotic fluid.

It is associated with esophageal atresia and TEF

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12
Q

What are signs and symptoms of tracheoesophageal fistula?

A

Infants with excessive drooling, choking (especially when fed), coughing and sneezing.

The infant may become cyanotic and may stop breating as the overflow of fluid from the blind pouch is aspirated fom the trachea and lungs.

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13
Q

How is tracheoesophageal fistula treated?

A

The region of the esophagus with the fistula is surgically removed. The two ends of the esophagus are then sutured back together.

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14
Q

When does the bronchi divide into 2 bronchial buds?

A

During week 5.

They will become the main or primary bronchi.

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15
Q

Secondary bronchial buds are formed how?

A

By undergoing a long series of branchings to form respiratory bronchioles.

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16
Q

True or false: each bronchopulmonary segment is a discrete anatomical and functional unit.

A

True.

This means that a bronchopulmonary segment can be surgially removed without affecting the function of the others.

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17
Q

What does the splanchnic mesoderm differentiate into?

A

Smooth muscle

Nerves

Blood vessels of the lungs.

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18
Q

What are the stages in lung development?

A

Embryonic (weeks 4 - 7)

Pseudoglandular (weeks 8 - 16)

Canalicular (weeks 17 - 26)

Terminal sac (weeks 26 - birth)

Postnatal (alveolar)

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19
Q

What occurs during the embryonic stage of lung development?

A

The initial formation of respiratory diverticulum up to formation of all major bronchopulmonary segments.

Lungs grow into pleural cavities.

Pleura differentiate.

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20
Q

What occurs during pseudoglandular stage of lung development?

A

Major formation and growth of duct systems within bronchopulmonary segments.

Histologically, the structures resemble a gland.

No gas exchange occurs yet.

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21
Q

What occurs during the canalicular stage of lung development?

A

The formation of respiratory bronchioles and terminal sacs

Increased vascularization

Capillaries found in walls.

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22
Q

What is found in the terminal sacs?

A

Epitheilium lining the alveoli, which have developed from respiratory bronchiles.

They differentaiate into two cells types.

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23
Q

What is needed for functioning lungs?

A

Capillaries

Alveoli

Surfactant of lungs

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24
Q

What is the function of type I pneumocytes?

A

They form part of the blood-air barrier.

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25
Q

What is the function of type II pneumocytes?

A

They are secretory cells that produce surfactant. They reduce surface tension and facilitate alveolar expansion.

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26
Q

When are most of the alveoli formed?

A

After birth.

The primary mechanism is septation of pre-existing alveoli.

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27
Q

When are fetuses generally viable (e.g. They have lungs developed enough to survive)?

A

Around 22 weeks.

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28
Q

What is infant respiratory distress syndome?

A

A deficiency or absence of lung surfactant. It results in a collpse or incomplete expansion of a whole lung.

It occurs mostly in infants less than 37 week’s gestation and can be treated with artificial surfactant.

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29
Q

What is pulmonary agenesis?

A

A complete absence of lungs, bronchi and vasculature.

It can occur bilaterally or unilaterally.

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30
Q

What is pulmonary hypoplasia?

A

A poorly devloped bronchial tree.

It may be a partial (small segment) or total (entire lung) that is poorly developed.

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31
Q

What is congenital diaphragmatic hernia?

A

When the septum by the diaphragm does not fully form and the abdominal contents are herniated into the thoracic cavity.

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32
Q

The absence or poor development of what membrane near the diaphragm results in congenital diaphragmatic hernia?

A

Pleuroperitoneal membranes.

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33
Q

What septum surrounds most of the diaphragm?

A

Septum transversum

34
Q

What is the cause of congenital diaphragmatic hernias?

A

Failure of pleuroperitoneal membranes to fuse with other components.

Clinical signs are a flat abdomen, breathlessness and cyanosis.

35
Q

How is congenital diaphragmatic hernia treated?

A

The trachea is tied off so that anything that the lungs make cannot get out. This fills the lungs with fluid, which pushes the abdomen down and the diaphragm will move and keep it in place. When the infant is delivered, ligature is taken off of the trachea.

36
Q

When does the cardiovascular system initially begin to develop?

A

Around week 4.

It is the first system to develop.

37
Q

What are major trends in the development of the heart?

A

The heart is converted into a 2 chambered and then 4 chambered structure.

The embryonic vascular system separates into system and pulmonary portions.

Systemic arterial outflow -> L
Systemic venous return -> R

38
Q

What is the embryonic circuit?

A

A series of aortic arches that connect to dorsal aorta.

The dorsal aorta subdivide into smaller vessels to supply the embryo.

39
Q

What drains blood in the embryonic circuit?

A

Anterior and posterior cardinal veins

40
Q

What are nutritional circuits?

A

Circuits that are needed in development only and have different functions later.

41
Q

What is the vitelline system?

A

Arteries and veins that drain the yolk sac.

42
Q

The umbillical vein carries oxygenated blood from the ____.

A

Placenta

43
Q

The aorta and pulmonary trunk arise from what embryonic structure?

A

Truncus arteriosus

44
Q

The smooth parts of the right and left ventricles arise from what embryonic structure?

A

Bulbus cordis

45
Q

The primitive ventricle gives rise to what adult structures?

A

Trabeculated part of right and left ventricles

46
Q

The primitive atrium gives rise to what adult structures?

A

The trabeculated part of right and left atria

47
Q

The smooth part of the right atrium, coronary sinus and oblique vein of the left atrium are derived from what embryonic structure?

A

Sinus venosus

48
Q

What is the endocardial cusion?

A

A region in the early hear that other things are attached to.

49
Q

What occurs to the heart as it develops?

A

The heart loops ventrally, and th heart bends to the left.

50
Q

What is dextrocardia?

A

When the heart bends to the left instead of to the right.

Great vessels are also found on the right side.

51
Q

After folding, the atrium and ventricle are separated by a narrow AV canal. The dorsal and ventral blocks of tissue grow together to form what?

A

Endocardial cushions.

52
Q

What is the function of the endocardial cushions?

A

They divide a single AV canal into separate right and left AV canals.

53
Q

What is the function of AV canals?

A

They regulate blood flow from the atria to the ventricles.

54
Q

What is the first critical step in the development of the 4-chambered heart?

A

The formation and fusion of the endocardial cushions.

If it does not fuse, there is large communication between chambers that occurs.

55
Q

Where does the muscular portion of the interventricular septum develop?

A

On the floor of the primitive ventricle.

It grows upward towards the endocardial cushions and downgrowing bulbar ridges.

56
Q

What separates the right and left ventricles?

A

The interventricular septum

57
Q

What is a ventricular septal defect?

A

When the septum that separates the right and left ventricle is not fully developed. It requires surgical correction to prevent shunting of blood.

58
Q

What occurs during the formaition of the atrial septum?

A

The foramen primum closes and the septum secundum grows towards the foramen ovale.

Once the septum secundum and foramen ovale close, the septumprimum degenerates.

59
Q

What is the flow of blood in the heart before birth?

A

Blood is shunted from the right atrium to the left atrium, where there is lower pressure. There is a gap between the septum secundum and the foramen ovale.

60
Q

How is the flow of blood in the heart affected after birth?

A

The septum primum has extended to the septum secundum to close and form the fossa ovalis.

Blood is no longer shunted from the right atrium to the left atrium, and there is higher pressure in the left atrium.

61
Q

What are atrial septal defects?

A

Defects in the septum of the atria.

They include formem primum and secundum types of defects.

62
Q

Where does the sinus venous initially open?

A

Into the dorsal wall of the primitive atrium

63
Q

How does the sinus venosus change as the heart develops?

A

The right horn enlarges as blood is shunted from the left to the right ventricle.

The shunts involve nutritional vascular circuits and embryonic circuits.

64
Q

What are the nutritional circuits?

A

Viteline and umbillical.

During development, all systemic inflow is moved to the right side.

65
Q

What are the embryonic circuits?

A

Cardinal veins

66
Q

What do the vitelline veins become incorporated into?

A

Liver and hepatic sinusoids, hepatic veins, part of IVC and some of the veins that drain the GI tract.

67
Q

What is the umbillical shunt?

A

During development, it loses direct connection with the heart and joints the ductus venosus.

The umbillical vein is connected with the IVC.

It also bypasses the liver and diverts oxygenated blood into the heart.

68
Q

What is the ductus venosus?

A

It connects the umbillical vein with the inferior vena cava. It bypasses the liver and diverts oxygenated blood to the heart.

69
Q

What happens to the sinus vensus during development?

A

There is a loss of vitelline veins, which are re-used as part of the GI system.

Re-routing of umbillical veins to utilize the ductus venosus to by-pass the liver do not have a direct connection to the right atrium yet.

70
Q

What happens to the cardinal veins during development?

A

The anterior cardinal veins become connected.

An anastomosis becomes the left brachiocephalic vein.

The right anterior cardinal and common cardinal become the superior vena cava.

71
Q

During development, the right anterior cardinal and common cardinal veins become what major vein?

A

The superior vena cavae

72
Q

How does shunting of blood affect the right horn?

A

It greatly increases the size of the right horn.

73
Q

A partition of the AV canal will form what valves?

A

Bicuspid and tricuspid valves.

74
Q

Partition of the TA will form what valves?

A

Aortic and pulmonary semilunar vavles.

75
Q

Neural crest cells invade ridges the form in the ____ and ____

A

Neural crest cells invade ridges that form in the bulbus cordis and truncus arteriosus.

76
Q

What is teratology of fallot?

A

A heart condition that results from a ventricular septal defect. There is also a tiny pulmonary trunk, which causes right ventricular hypertrophy.

77
Q

How many pairs of aortic arches are there?

A

6.

They connect the aortic sac/TA to dorsal aortae.

78
Q

What is patent ductus arteriosus?

A

An abnormal connection between the aorta and the pulmonary artery in the heart.

It causes mixing of blood from the aorta in the pulmonary artery.

79
Q

How is patent ductus arteriousus treated?

A

With a ligation so that the aorta and pulmonary trunk will be separated.

80
Q

The esophageal system is an extension of what?

A

The foregut.