Lecture 27 Flashcards
What germ layers does the respiratory system derive from?
the endoderm and mesoderm
What is the order of lung development at week 4?
Laryngotracheal groove> Laryngotracheal diverticulum anterior to the foregut> distal end turns to Respiratory buds
What does splanich mesoderm surrounding the laryngotracheal diverticulum develop into?
cartilage, connective tissue, and muscles of the trachea
What does the tracheoesophageal septum divide the foregut into?
Ventral: laryngotracheal tube
Dorsal: Orophayrnx and esophagus
how many pharyngeal pouches are there and which one disintegrates? what do they form?
There are 6 and the 5th one disintegrates
1,2,3= tongue
hypopharyngeal= posterior part of tongue
4th and 6th= respiratory system
What germ layer does laryngeal epithelium come from?
endoderm of cranial part fo the laryngotracheal tube ( larynx+ trachea)
How are laryngeal cartilages derived from?
migration of neural crest cells into the mesenchymal of 4th and 6th pairs of pharyngeal arches
What do laryngeal muscles develop from?
mesenchymal myoblasts form the 4th and 6th pair of pharyngeal arches
Where do arytenoid swellings come from?
mesenchyme at cranial end of laryngotrachael tube
where are epiglottal swellings derived from?
from the caudal part of hypopharyngeal eminence ( from 3rd and 4th pharyngeal arches)
What forms the laryngeal ventricles?
formed by recanalization of the laryngeal lumen
How many lobes on each side of the lungs?
on the right there are 3 lobes on the left 2 lobes
The lung bud divides and forms what?
2 primary bronchial buds.
the secondary and tertiary buds grow laterally from the primary buds into the pericardioperitoneal canals.
Segmental bronchus with surrounding mesenchyme is called what?
bronchopulmonary segments
At what week do the respiratory bronchioles develop?
By week 24 ( 17 orders of branches are formed)
7 more generation of branches formed after birth to 8 years (24 branches)
Define Atresia
obstruction/ blockage/ abnormal closure of a passage, due to failure of recanalization of the lumen
Define stenosis
narrowing/ partial closure of a passage. Due to unequal partitioning of the foregut
Define fistula
abnormal communication/passage due to incomplete division of a tube. ( incomplete division of cranial part of foregut into respiratory system and esophagus)
Type I versus II and III atresia of trachea and esophagus
Type 1: superior part of trachea did not develop and inferior sticks to esophagus (m
Type2: no inferior or superior esophagus
Type 3: only bronchial buds are developed, lacks a trachea, nothing connects the buds.
LOOK AT PIC
Atresia with distal fistula
atresia means wrong communication:
this case is the stomach is connected to the trachea ( below so distal) and the esophagus is just closed/ blind, not connected to the stomach
Atresia with proximal fistula
the esophagus is bound to the trachea and the stomach tube is blind
Treacheoesophageal fistula
the stomach and the esophagus are linked by the same tube but they are both connected/communicated to the trachea
can be component of VACTERL= vertebral anomaly, anal atresia, cardiac defects, TEF, Esophageal atresia, Renal anomalies, and limb defects
can also be due to polyhydramnios= excessive quantity of amniotic fluid in fetal life.. the fluid is supposed to enter the stomach but instead goes to amniotic cavity.
Atresia with double fistula
the stomach and esophagus are not connected but each is connected to the trachea on their own
Esophageal atresia
abnormal blockage/ development of the esophagus mainly due to failure of recanilization of lumen
nothing is connected. both tubes are blind just stop. failure of recanalization of the lumen
What sex commonly has tracheoesophageal fistula?
males
What caused tracheoesophageal fistula?
incomplete division of cranial forgut into respiratory system and esophagus
what are signs and symptoms of tracheoesophageal atresia?
coughing and choking during feeding, pneumonia, polyhydramnios in fetal life
At what week is the pseudoglandular stage?
5-17 week… major elements of lungs but no respiratory bronchioles
at what week is the Canalicular period?
16-25 week, terminal bronchioles divides into 2 major respiratory bronchioles, which in turn divide into 3-6 alveolar ducts.
TYPE 2 alveolar cells that produce SURFECTANT appear.
At what week does surfactant secretion occur?
week 20, increases a lot during the last 2 weeks of pregnancy important for survival at weeks 22-26 ( this is when produce is enough to survive in ICU)
week 26-28; can survive if born prematurely with adequate terminal sacks and surfactant.
At what week Is the terminal sac period?
week 24 to birth; terminal sacs formed lined by squamous epithelium; capillaries establish close contact.
At what week is the alveolar period?
week 32 to 8-10 years.
primitive alveoli with well developed epithelial-endothelial capillary contacts ( blood-air barrier after birth)
Mature alveoli are formed after birth as the lungs expand ( alveoli formation continues unto 8-10 years)
What produces surfactant?
surfactant is a lipoprotein produced by type 2 alveolar cells
what is the purpose of surfactant?
it reduces surface tension and facilitates expansion of terminal sacs
What causes respiratory distress syndrome and hyaline membrane disease?
a surfactant deficiency/ rapid labored breathing 1-2% of babies mostly premature ones
what occurs with prolonged intrauterine asphyxia?
irreversible changes in type II cells rendering them incapable of producing surfactant
What medications can accelerate fetal lung movements and surfactant?
glucocorticoids during pregnancy, surfactant production ( corticosteroids, or exogenous surfactant)
what are signs and symptoms of reduced surfactant?
under-inflated lungs, amorphous protein deposits in lungs and respiratory distress
What occurs with a diaphragmatic hernia in an infant?
lung cannot develop normally because there is very little thoracic space, the intestines are there.
What occurs to a still born’s lungs?
the still born lungs are firm and they sink in water as they have no air, only fluid.
in a normal baby, they have a little amniotic fluid in their lungs but it is taken up by capillaries and lymphatics
what can oligohydroamnios lead to?
insufficient amount of amniotic fluid may lead to retarded development of lungs pulmonary hypoplasia
What is the primordium of future body cavities?
intraembryonic coelom
Where does the intraembryonic coelom develop?
lateral mesoderm
What are the two layers that the lateral mesoderm is divided into?
somatopleure ( somatic)= parietal layer of serous pericardium, pleura, and peritoneum
Splanchopleure ( splanchnic)= visceral pericardium, pleura, peritoneum
What does head folding of the embryo do?
brings the heart and pericardial cavity anterior to the foregut and the septum transversum forms
what does the septum trasnversum partition separate ? ( head folding)
the pericardial and abdominal cavities and the heart is suspended by the dorsal mesocardium
what does lateral folding of embryo do?
pericardial coeloms fuse forming the pericardial cavity. The pericardial cavity is lined by a visceral and parietal layer. the pericardial cavity is continuous with the pericardioperioneal canal.
How is pleural cavity formation?
bronchial buds grow into pericardioperitoneal canal.
membranous ridges develop from lateral wall.
Cranial ridge: pleuropericardial fold
Caudal ridge: Pleuroperitoneal fold
What separates the pleural cavity from pericardial cavity? and what fuses to form the fibrous pericardium?
Pleuropericardial membrane
What is the septum transversum?
the primordium of central tendon of diaphragm
what results in final closure of the pleuroperitoneal canal of diaphragm?
migration of myoblasts
Anteromedial defect
diaphragmatic hernia
rare 2-5 %
defect between costal and sternal musculature
Central defect
congenital hiatal hernia of esophagus
esophageal hiatus is abnormally large
posterolateral defects
- congenital diaphragmatic hernia.
- defect of pleuroperitoneal membrane
- abdominal contents herniate into thorax
- more common on left side.
( foramen of bochdalek)
Abdomen is empty when lying flat because the contents herniate into the thorax, the lung is compressed and hyplastic ( high mortality rate) requires urgent surgery.
Eventration of diaphragm
defective musculature on half of the diaphragm because of failure of the muscle tissue from body wall to extend into the pleuroperitoneal membrane. the affected side moves up with the contraction of diaphragm during respiration=== PARADOXICAL RESPIRATION.
PIC looks like the diaphragm is at the arm
