Lecture 18: Respiratory System Flashcards
what comprises lower resp tract
larynx, trachea, bronchi, and lungs
when do lower resp organs begin to form
4th week
respiratory primordium
median outgrowth of ventral wall of pharynx called the laryngotracheal groove
laryngotracheal groove eventually becomes the
laryngotracheal tube
laryngotracheal tube composed of
endoderm and splanchnic mesoderm
endoderm of LT tube
gives rise to epithelium and glands of larynx, trachea, bronchi, and pulmonary epithelium
splanchnic mesoderm of LT tube
connective tissue, cartilage, and smooth muscle
functions of larynx
swallow, respiration, voice production
borders of larynx
upper = epiglottis, lower = cricoid cartilage
larynx communicates with
above: mouth and nasal cavities
below: trachea
what does the epithelial lining develop from(in larynx)
endoderm of LT tube
where does cartilage develop from (in larynx)
4th and 6th pharyngeal arches (come from neural crest)
where to arytenoid swellings come from
mesenchyme at cranial end proliferating rapidly. causes paired swellings.
what do the arytenoid swellings do
grow towards tongue converting primordial glottis into T shaped laryngeal inlet (lumen becomes narrow slit)
when does the laryngeal lumen recanalize
10th week
what is the t shaped glottis bound by
lateral arytenoid swellings and cranial epiglottis
what are the vocal cords formed from
during recanalization, laryngeal ventricles (recesses) form. bound by mucous membranes which form vocal cords.
what does the epiglottis do
covers the larynx
what does the epiglottis develop from
hypobrachial eminence (muscles form from myoblast in 4th-6th arches)
laryngeal web
from incomplete recanalization of larynx in week ten – partial obstruction of airway in a newborn
what controls branching in respiratory tract
mesoderm
what happens at the end of week four
laryngotracheal groove invaginates to form laryngotracheal diverticulum
what do the tracheo-esophageal folds become
the TE septum
what does the TE septum do
divides LT tube from oro-pharync and esophagus
TE fistula
abnormal communication between trachea and esophagus
what is a TE fistula caused by
incomplete division of foregut into resp tracht (trachea) and esophageal parts – incomplete fusion of TE folds
where do lung buds develop
caudal end of LT tube during 4th week
lung buds become
bronchial bud
how many bronchi
2 on L, 3 on R
difference between R and L bronchi
R are larger, shorter, and more vertical
L only have two lobes
bronchopulmonary segment
bronchus and mesenchyme
how many orders of branches at week 24
17
periods in lungs
1) pseudoglandular (5-17 weeks)
2) canalicular (16-25 weeks)
3) terminal sac (24 weeks to birth)
4) alveolar (birth to 8 years)
pseudoglandular period
formation and growth of duct system, branchopulmonary segments not well developed, fetuses cannot survive
canalicular period
bronchi and terminal bronchioles enlarge, highly vascular, alveolar sacs not really differentiated, respiration possible
terminal sac period
epithelium very thing, contact between epi and endothelial cells permit gas exchange, type I alveolar cells line terminal saccules, proliferation of capillary netowrk, type II alveolar cells secrete surfactant
issues with lungs prior to 26-28 weeks
inadequate surfactant, insufficient alveolar surface area, inadequate pulmonary vasculature
alveolar sac
terminal sacs have very thin epithelial lining, alveolocapillary membrane allows gas exchange, terminal saccules = future alveolar ducts
autonomous gas exchange requires
surfactant, transformation of lungs to a gas exchanging organ, establishment of parallel pulmonary and systemic circulations
when do most alveoli develop
95 percent post natally
what does in utero normal lung development depend on
1) adequate thoracic space for lung growth
2) fetal breathing movements
3) amniotic fluid volume
what is the preparation for respiration
1) fetal breathing movements (condition resp muscles, stimulate lung development)
2) at birth, lungs filled with fluid
3) birth - replacement of intra alveolar fluid with air
pharynx connects
to larynx (which goes to trachea) the esophagus
