Embryology of Resp. System Flashcards

1
Q

What week does gastrulation occur?

A

Week 3

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2
Q

Which 2 layers of the germ layer are most important for the development of the resp. system?

A

Endoderm and mesoderm

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3
Q

What does the endoderm form and what does the mesoderm form?

A

Endoderm: Epithelial lining and glands
Mesoderm: muscles, cartilage, connective tissue

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4
Q

What is needed for the appearance and location of the lung bud and what is it’s importance?

A

Retinoic acid: It is needed for the upregulation of the transcription factor TBX4 expressed in the gut tube

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5
Q

What is the role of TBX4?

A

Induces formation of lung bud and its continued growth and differentiation

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6
Q

How many pharyngeal arches , pouches, and clefts are there and where do they derive from?

A

5 pharyngeal arches: mesoderm
4 pouches: endoderm
4 pharyngeal clefts/grooves: ectoderm

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7
Q

What structure is derived from the 1st pharyngeal arch?

A

Mandibular (maxillary and mandibular processes)

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8
Q

What are the nerve supply derivatives of the 1st arch?

A

CN V : Trigeminal–> maxillary and mandibular divisions

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9
Q

What are the muscles of the 1st pharyngeal arch?
(MMATT)

A

Mastication (temporal, masseter, medial, lateral, pterygoids), Mylohyoid, Anterior belly of digastric, Tensor Palatine, Tensor tympani

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10
Q

What are the skeletal derivatives of the 1st pharyngeal arch

A

Premaxilla, maxilla, zygomatic bone, part of temporal bone, meckel cartilage, mandible malleus, incus, anterior ligament of malleus, sphenomandibular ligament

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11
Q

what is the derivative of the 2nd pharyngeal arch?

A

Hyoid

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12
Q

What is the nerve innervation from the 2nd pharyngeal arch?

A

Facial- CN7

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13
Q

What are the muscle derivatives of 2nd arch?
(Face posteriorly, side by side)

A

Facial expression (buccinator, auricularis, frontalis, platysma, orbicularis oris, orbicularis oculi), posterior belly of digastric, stylohyoid, stapedius

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14
Q

What is the nerve innervation from the 3rd pharyngeal arch?

A

Glossopharyngeal -CN IX

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15
Q

What is the muscle derivative of 3rd pharyngeal arch?

A

Stylopharyngeus

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16
Q

What are the skeletal derivatives of the 3rd pharyngeal arch?

A

Greater horn and lower portion of body of hyoid bone

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17
Q

What are the skeletal derivatives of the 2nd pharyngeal arch?

A

stapes, styloid process, stylohoid ligament, lesser horn and upper portion of body of hyoid

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18
Q

What are the nerve derivatives of the 4th and 6th pharyngeal arches?

A

Vagus-X
4th: Superior laryngeal branch
6th: Recurrent laryngeal branch

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19
Q

What are the muscle derivatives of the 4th arch?

A

cricothyroid, levator veli palatini, constrictors of pharynx

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20
Q

What are the muscle derivatives of the 6th arch?

A

Intrinsic muscles of larynx

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21
Q

What are the skeletal derivatives of the 4th and 6th arch?

A

laryngeal cartilages: thyroid, criciod, arytenoid, corniculate, cuneiform

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22
Q

Which week does the trachea and lung develop ? Explain what happens during this week.

A

4th week
Edothelial cells coming off foregut forms lung bud. Tracheoesophageal groove forms, Bronchial bud forms, and tracheoesophageal septum forms

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23
Q

Which arches do the muscles and cartilage derive from?

A

4th and 6th

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24
Q

Explain role of tracheoesophageal septum

A

Separates the anterior lung bud (resp. diverticulum) from the posterior foregut

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25
Q

What takes place during week 5 of tracheal and lung development?

A

Tracheoesophageal septum closes
Endoderm from gut tube forms glands and epithelial lining
Splanchnic mesoderm forms muscles, cartilage, and CT
Stages of lung development starts

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26
Q

______ is the abnormal communication between trachea and esophagus due to defective development of the tracheoesophageal septum. May be associated with esophageal atresia

A

Tracheoesophageal fistula
-sometimes seen when the esophagus ends blindly

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27
Q

What else can be seen with TEF?

A

Poly-hydramnios
Baby can’t pass meconium
Baby will choke immediately during feeding
Cyanosis
Spina bifida
Renal anomalies

28
Q

Why does the infant choke with TEF?

A

The choke due to accumulation of fluid in the mouth/resp. tract which may pass into the lungs- causes pneumonitis/ lung infection

29
Q

____ forms the parietal pleura

A

Somatic mesoderm

30
Q

____ forms the visceral pleura

A

Splanchnic mesoderm

31
Q

_____ separates the pleural cavities from the pericardial cavity and fuses to form form fibrous pericardium

A

Pleuropericardial folds

32
Q

_____ separates pleural cavities from the peritoneal cavity. They fuse with the septum transversum & dorsal mesentery of esophagus to form the posterolateral parts of the diaphragm

A

Pleural-peritoneal folds

33
Q

When do the two folds form and where do they form from??

A

When the lung bud continues to grow into the pericardio-peritoneal canals; the two folds form in each canal
-forms from lateral walls of the canals

34
Q

What are the 5 stages of lung development?

A

Embryonic
Pseudo-glandular
Canicular
Saccular (terminal sac)
Alveolar

35
Q

Describe what takes place during pseudo-glandular stage and when does it take place?

A

Takes place during weeks 5-16
Primary left and right bronchi form–> Right splits into 3 lobar bronchi/ secondary bronchi & Left splits into 2 lobar/secondary bronchi–> Right and left lobar splits into tertiary bronchi–> Terminal bronchioles form for both
-Only conducting unit formed

36
Q

Can a fetus born before 20 weeks survive?

A

NO

37
Q

Describe what takes place during the canalicular stage and when does it take place?

A

Takes place during weeks 16-26
Terminal bronchioles become Resp. bronchioles–> Resp. bronchioles divide into 3-6 alveolar ducts —> angiogenesis and BLOOD AIR BARRIER forms–> Pneumocytes form (Type 1 and 2)—> Baby can survive with intensive care

38
Q

Describe what takes place during the saccular stage and when does it take place?

A

Takes place during weeks 26 to birth
More resp bronchioles form, so more alveoli, more pulmonary capillaries form–> Type 1 cells perform gas exchange and type 2 cells form surfactant for preventing alveolar collapse

39
Q

Describe what takes place during the embryonic stage and when does it take place?

A

Takes place during weeks 3-8
Organ start to develop and this when errors can occur

40
Q

Describe what takes place during the alveolar stage and when does it take place?

A

Takes place from week 36 til ~ 8 years of age
Increase number of capillaries, increase number of alveoli, septa forms in alveoli to increase surface area, more surfactant

41
Q

What takes place before birth

A

In utero breathing occurs via aspiration and expulsion of amniotic fluid–> increases resistance through gestation

42
Q

What takes place after birth?

A

Fluid gets replaced with air–> decreased pulmonary vascular resistance

43
Q

Describe Infant Resp Distress Syndrome and what is another name for it?

A

Another name: Hyaline membrane disease
-if baby is born premature not enough surfactant so increased surface tension, increased collapsing pressure so alveolar may collapse when born

44
Q

What can treat Infant Resp. Distress?

A

Maternal steroid before birth: glucocorticoids which accelerates fetal lung movement and surfactant production, exogenous surfactant for infant

45
Q

What factors influence normal development of lungs and what damages the factors?

A

Thoracic space for growth: congenital diaphragmatic hernia
Fetal breathing movements: having no air lungs at birth
Amniotic fluid volume: Oliogohydramnios

46
Q

How do the lungs appear with Infant Resp. Distress?

A

They look quite dense and white due to collapse of lung tissue. Air in lung is small and chest xray has ground-glass appearnace

47
Q

What is congenital lung cysts?

A

It is formed by the dilation of terminal bronchioles that may be due to disturbance in development during late fetal life. Cysts drain poorly so frequently causes chronic infection

48
Q

What is agenesis?

A

Failure of lung bud to develop
-Unilateral agenesis : could live

49
Q

What are the 2 portions of the diaphragm?

A

Peripheral: Muscular part (sternal costal lumbar)
Central : Aponeurotic part (central tendon)

50
Q

Which cervical vertebrae keeps the “diaphragm alive”?

A

C3,C4,C5

51
Q

What forms the diaphragm?

A

The septum transversum, pleuro-peritoneal membrane, Dorsal mesentery of esophagus

52
Q

What nerve supplies the diaphragm?

A

Phrenic nerve

53
Q

What forms the musculature part of the diaphragm?

A

Cervical myotomes: C3-C5

54
Q

What forms the Central tendon?

A

Septum transversum

55
Q

What forms the posterolateral parts of diaphragm?

A

Pleuro-peritoneal folds

56
Q

What forms the crura of diaphragm?

A

dorsal mesentery of esophagus

57
Q

What is a congenital diaphragmatic hernia?
-what causes it and what is the mortality rate ?
-which side of the chest is this most commonly seen?
-what type of defect is it: postero lateral or parasternal ?

A

When a hole/hernia in diaphragm allows the stomach and intestine to enter into the chest due to failure of pleuroperitoneal membranes to close the pericardioperitoneal canal
-Posterolateral
mortality rate: 76% due to pulmonary hypoplasia
Causes lung to not develop properly
seen on left side

58
Q

What is pulmonary hypoplasia?

A

Caused by CDH: the lungs do not develop properly so they are small and cannot circulate oxygenated blood properly

59
Q

Name 2 type of CDH

A

Retro/parasternal hernia
Postero-lateral hernia

60
Q

What forms the alveoli?

A

The endoderm of the foregut

61
Q

Explain how the larynx is formed?

A

After gastrulation around week 5, the laryngeal orifice forms and the endodermal cells invade the orifice and forms the vocal cord.
-The mesoderm forms the muscles and the cartilages
-It also forms the epiglottic swelling that forms above the orifice and the arytenoid swelling that forms above the orifice

62
Q

Which week does the mature larynx form and what does the orifice become?

A

12 and laryngeal inlet

63
Q

Name the epithelium around the larynx?

A

Psuedostratified ciliated columnar epithelium

64
Q

Which germ layer does the vagus nerve derive from and what part of the larynx does it supply?

A

Mesoderm and it supplies the epithelial lining

65
Q

Which week do all the lower resp. organs form?

A

4

66
Q

Which end of the diverticulum forms the larynx?

A

Cranial end

67
Q

What divides the lateral plate mesoderm into the somatic and splanchnic mesoderms?

A

Intra-embryonic coelom