Development of the Respiratory System

Question 1

What does fertilisation of a haploid egg by a haploid sperm give rise to?

Answer 1

A single diploid cell

Question 2

When do cells become pluripotent stem cells?

Answer 2

At 16 cell stage

Question 3

When is 16 cell stage reached by?

Answer 3

End of day 3

Question 4

What occurs at day 5?

Answer 4

Hollow ball of cells the blastocyts has outer trophoblast and inner cell mass

Question 5

What does trophoblast give rise to?

Answer 5

Foetal placenta whereas inner cell mass into embryo

Question 6

What happens at day 6?

Answer 6

Inner cell mass implanted to uterine endometrium and endrometrial gland enlarges - known as decidua more vascularised

Question 7

What happens at day 8?

Answer 7

Cell mass differentiates into hypoblast (primitive endoderm) and Epiblast (primitive ectoderm)

Question 8

What does hypoblast and epiblast together form?

Answer 8

Bilaminer embryonic disc within forms amnion

Question 9

What happens to amninon?

Answer 9

Extends surrounds full embryo forming embryonic cavity - hypoblast cells migrate and flatten form exocoelomic membrane around inner surface of blastocyst

Question 10

What happens at day 9?

Answer 10

Hypoblast forms walls of the egg sac and enbryonic position between amniotic cavity and yolk sac

Question 11

What do cells in york sac develop into?

Answer 11

Gonad and yolk sac in week 4 creates GI tract

Question 12

What happens in week 3?

Answer 12

Gastrulation

Question 13

What happens in gastrulation?

Answer 13

Bilaminer disc into trilaminer structure 3 germ layers ectoderm (skin cns) mesoderm (CT and muscle)Endoderm (epithelia of gi and organs)

Question 14

What day does gastrulation start?

Answer 14

15 with migration of cells from epiblast forming primitive streak - groove on dorsal surface extends from posterior tail to anterior node of bilaminar disc

Question 15

What happens when primitive disc is formed?

Answer 15

Epiblast cells migrate inwards below primitive streak some displace hypoblast to form endoderm other to form mesoderm

Question 16

What do epiblast cells form?

Answer 16

Ectoderm

Question 17

What happens at day 16?

Answer 17

mesoderm cell from node migrate to head of embryo to form notochord

Question 18

What forms in week 3?

Answer 18

Oropharyngeal membrane on dorsal surface of anterior

Question 19

Where does cloacal membrane form?

Answer 19

Dorsal surface of posterior

Question 20

What does oropharyngeal do in week 4?

Answer 20

Breakdown to connect oral cavity to pharynx and gi trict

Question 21

What does cloacal break to form?

Answer 21

Anal, urinary and reproductive tracts

Question 22

What happens to embryo in week 4?

Answer 22

Embryonic folding - due to unequal growth rates

Question 23

What does medial plane form?

Answer 23

Head and tail

Question 24

What does lateral folds give rise to?

Answer 24

Coalom and pinches off yolk sac giving rise to primitive gut

Question 25

What does primitive gut have?

Answer 25

3 regions - foregut, midgut and hindgut

Question 26

What happens at time of folding?

Answer 26

Several pharyngeal arches on either side of head as internal pharyngeal pouches and from ventral wall of foregut

Question 27

Where does respiratory develop from?

Answer 27

Ventral wall of foregut 4th and 6th pharyngeal arches the respiratory system develops

Question 28

What grows during week 4?

Answer 28

Lung bud or respiratory diverticulum appear as outgrowths from ventral wall of foregut

Question 29

What does lung bud have?

Answer 29

Opening common to foregut and extends it seperates from foregut by oesophagotracheal ridges

Question 30

What do oesophagotracheal ridges form?

Answer 30

Fuse to create oesophagotracheal septum divides the foregut into dorsal oesophagus and ventral trachea - maintained within laryngopharynx

Question 31

What is lining if larynx and respiratory system?

Answer 31

Endodermal, in origin it is mesodermal from mesenchyme of 4th6th pharyngeal arches

Question 32

What do mesenchymal cells rapidly divide into?

Answer 32

Laryngeal opening for t shaped opening - differentiates into thyroid cricoid and arytenoid cartilages

Question 33

What happens as laryngeal cartilages form?

Answer 33

Epithelium proliferates temp blocks lumen of diverticulum - followed by vascularisation and recanalisation resulting in forming laryngeal ventricles for true and false vocal chords

Question 34

What does diverticulum divide into at week 5?

Answer 34

Seperates from foregut - 2 lateral branches for L and R primary bronchi, R forms 3 secondary bronchi, L 2 secondary bronchi continue to grow till ten tertiary on right and 8 on left

Question 35

What do bronchi give rise to?

Answer 35

Bronchopulmonary segments of the lungs

Question 36

Whats formed at month 6?

Answer 36

Bronchioles and upto 17 more divisions, before bronchial tree final occurs 6 more divisions postnatal

Question 37

What are pericardioperitineal canals?

Answer 37

Narrow either side of foregut - fill as lung bunds sub divide visceral and paritel pleura derived from mesoderm, pleural cavity forms filled with pleural fluid

Question 38

What happens at month 7?

Answer 38

bronchial subdivisions are narrower and steady vascularisation - respiration possible when cuboid bronchial endothelium flatten to squamous

Question 39

What extends from respiratory bronchioles?

Answer 39

Primitive alveoli and terminal sacs for type 1 and type 2 alveolar cells

Question 40

WHt is type 1 and type 2 alveolar associated with?

Answer 40

Type 1 - blood and lymph capillaries | Type 2 - secretes surfactant to prevent collapse of lung

Question 41

How long does lung grow?

Answer 41

Till 10 of postnatal life

Question 42

What is oesophageal atreasia?

Answer 42

Oesophagus terminates in a blind ending passag

Question 43

What is TEF tracheoaphageal fistula?

Answer 43

abnormal opening forms between oesopahgus and trache in 90% together , babies cyanotic and stop breating

Question 44

What is the vacterl association?

Answer 44

Vertebral, Anal atresia, Cardiac, TEF, Eosophageal atresia, Renal and Limb defects

Question 45

How do congenital cysts arise?

Answer 45

Abnormal budding of diverticulum resulting in dilated and poorly vascularised terminal or larger bronchioles - in radiographs honeycomb appearece, cysts are air or fluid filled, treated with resp support, antibiotic and surgery

Question 46

What are other abnormalities of the bronchial tree?

Answer 46

Formation of ectopic lung lobes from trachea or oesophagus , loss of lung lobe or enter lung and formation of blind ending trachea with lung absnece

Question 47

When does respiratory distress syndrome occur?

Answer 47

insuffiecient quantities of surfactant produce, most common death - collapsed alveoli filled with protein rich fluid and form hyaline membrane filled with CT cells

Question 48

How to treat RDS?

Answer 48

Resp support with glucocorticoids - enhance surfactant production and synthetic surfactants - signs are rapid and shallow breating, nostrils flare, retraction of chest wall