Lecture 18: Embryonic Respiratory System

Question 1

lower respiratory tract consists of

Answer 1

epiglottis, larynx, trachea, left and right lung, pulmonary blood vessels, heart, upper lobes, middle lobe (r), lower lobes

Question 2

when/where laryngothracheal groove forms

Answer 2

week 4

lower/back part of throat, connects w/ surface ectoderm of mouth

Question 3

respiratory primordium is

Answer 3

laryngotracheal groove; median outgrowth of ventral wall of pharynx

Question 4

respiratory diverticulum

Answer 4

bud outpouching of tissue of ventral wall of foregut, will form 2 lungs

Question 5

laryngotracheal tube tissue layers

Answer 5

endoderm, sphlancnic mesoderm

Question 6

endoderm of laryngotracheal tube becomes

Answer 6

epithelium and glands of larynx, trachea, bronchi, and pulmonary epithelium

Question 7

sphlancnic mesoderm of laryngotracheal tube becomes

Answer 7

connective tissue, cartilage, and smooth muscle

Question 8

larynx functions

Answer 8

communicates with mouth/nasal cavities for swallowing, respiration, voice production

Question 9

larynx borders

Answer 9

upper: epiglottis
lower: cricoid cartilage

Question 10

artenoid swellings

Answer 10

cranial end of L-T tube; are 4th and 6th pharyngeal arches mesenchyme that proliferate

Question 11

laryngeal inlet

Answer 11

T-shaped region of mesenchymal tissue formed by meeting of artenoid swellings; temporarily occludes respiratory tract before recanalizing

Question 12

vocal cord formation

Answer 12

after recanalization of larynx, laryngeal ventricles/cartilages become vocal cords

Question 13

epiglottis function

Answer 13

covers the larynx so food doesn’t get into the lungs

Question 14

epiglottis derivation

Answer 14

caudal hypobranchial eminence 4th-6th arch myloblasts

Question 15

laryngeal web

Answer 15

non-lethal anomaly, occurs when recanalization of larynx isn’t complete (week 10) and get partial obstruction of newborn’s airway

Question 16

trachea derivation

Answer 16

lung buds that separate from foregut become trachea and 2 bronchial buds

Question 17

laryngothracheal (L-T) diverticlum timing

Answer 17

end of week 4

Question 18

tissue layers of L-T tube

Answer 18

mesoderm, endoderm

Question 19

where long bud forms

Answer 19

distal end of L-T diverticulum

Question 20

T-E folds become

Answer 20

T-E septum

Question 21

number of lobes of each lung

Answer 21

Left: 2; Right:: 3

Question 22

what T-E septum separates

Answer 22

laryngotrachel tube from oro-pharynx, esophagus

Question 23

T-E fistula is

Answer 23

when T-E folds don’t completely separate the trachea and esophagus, get abnormal communication between trachea and esophagus

Question 24

most common anomaly of lower respiratory tract

Answer 24

T-E fistula; 85% associated with esophegeal atresia

Question 25

incidence of T-E fistula

Answer 25

1/3000-1/4500 live births; male>females; 85% associated w/ esophageal atresia

Question 26

what surrounds alveoli/why

Answer 26

capillaries; take in oxygen

Question 27

where lungs form

Answer 27

within pericardioperotneal canals (2)

Question 28

1st branch off trachea on each side

Answer 28

primary bronchus

Question 29

branches of primary bronchus

Answer 29

secondary bronchi; 2 on L, 3 on R

Question 30

characteristics of right secondary bronchi

Answer 30

larger, shorter, more vertically oriented 3 secondary bronchi more likely to get something stuck in bronchi because of verticality

Question 31

characteristics of left secondary bronchi

Answer 31

2 secondary bronchi with 2 lobes more horizontal orientation

Question 32

number of orders of branching of bronchi by 24 weeks

Answer 32

17 orders

Question 33

bronchopulmonary segment made of

Answer 33

bronchus + mesenchyme

Question 34

lung maturation stages

Answer 34

1. pseudoglandular pd 2. canalicular pd 3. terminal sac pd 4. alveolar pd

Question 35

pseoduglandular period

Answer 35

1st period of lung development, 6-16 weeks formation and growth of duct systems bronchopulmonary segments not well developed fetuses can's surive inefficient/impossible oxygen exchange

Question 36

canalicular period

Answer 36

16-25 weeks (2nd pd of lung development) bronchi and terminal bronchioles enlarge, encompass capillaries highly vascular alveolar sacs not truly differentiated respiration possible

Question 37

terminal sac period

Answer 37

26 weeks to birth capillaries bulge into alveoli epithelium very thin so no intervening mesoderm for oxygen to get across contact between epithelial and endothelial cells permit gas exchange type II alveolar cells secrete surfactant

Question 38

function of surfactant

Answer 38

from type II alveolar cells form monomolecular fil over internal walls of terminal saccules lower surface tension reaches adequate levels in late fetal period

Question 39

respiratory distress syndrome

Answer 39

babies born prior to 26-8 weeks; due to lack of surfactant, insufficient alveolar surface area, inadequate pulmonary vasculature

Question 40

alveolar period

Answer 40

gestation/birth to 8 years old capillaries are immediately adjacent to alveoli- gas exchange easy terminal saccules will be future alveolar ducts

Question 41

percentage of alveoli formed after birth

Answer 41

95%

Question 42

what autonomous gas exchange requires (in alveolar pd)

Answer 42

surfactant transformation of lungs to a gas exchanging organ est of parallel pulmonary and systemic circulations

Question 43

what increases after birth re: lungs

Answer 43

surface area of air-blood barrier, via growth of alveoli and capillaries

Question 44

number of capillaries from birth to age 8

Answer 44

50 million to 300 million

Question 45

chest xray of newborn infant vs adult

Answer 45

will be dense

Question 46

how does fetus prepare for breathing

Answer 46

fetal breathing movements that condition respiratory muscles, stimulate lung development

Question 47

at birth, what exchanges re: lungs?

Answer 47

intra-alveolar fluid exchanges with air

Question 48

what in-utero normal lung development depends on

Answer 48

adequate thoracic space for lung growth, fetal breathing movements, amniotic fluid volume

Question 49

why amniotic fluid matters for lung development

Answer 49

keeps muscles of uterus from collapsing on baby's lungs/chest

Question 50

respiratory distress syndrome

Answer 50

caused by lack of surfactant production, so alveoli don't inflate properly occurs in 2% live newborns treat with berthamethasone, a steroid mother takes that causes fetal lung cells to make surfactant

Question 51

what causes esophageal atresia with a TE fistula

Answer 51

incomplete fusion of T-E folds