Embryology of respiratory system Flashcards
The median outgrowth where the embryological development of the respiratory system start is known as what?
laryngotracheal groove
- The laryngotracheal groove is the primordium for which structures and also where do this groove appear?
- Name the pharyngeal pouch pair where the laryngotracheal groove is formed.
Primordium of tracheobronchial tree and lungs
Found on the floor caudal end of anterior foregut (Primordial pharynx)
2. 4th pair
- The endodermal lining of laryngotracheal groove forms which structures?
- The splanchnic mesoderm surrounding foregut forms?
- Pulmonary (Respiratory) epithelium of trachea, and larynx and bronchi
- also forms glands for this structures. - connective tissue, smooth muscle, cartilage of larynx, trachea and bronchi
By end of 4th week
1. Laryngotracheal groove has protruded to form pouch-like —————-
2. Lies ventral to caudal part of ————–
3. Diverticulum elongates and becomes invested with ————-
4. Distal end of diverticulum enlarges to form globular ————-
5. Single bud from which ————— arises
6. Right and left primary bronchial buds First appear as two lateral outpouchings on either side of ——————
- Laryngotracheal diverticulum
- Foregut
- splanchnic mesenchyme
- respiratory (lung) buds
- tracheobronchial tree
- tracheal primordium
- Laryngotracheal diverticulum separates from ——–A———–
Maintains communication via ———B————-
Tracheoesophageal folds develop in ——-C———-
Come together and fuse to form ——–D—— - All this happen by end of which week.
1.A. Primordial pharynx
B. primordial laryngeal inlet
C. Diverticulum
D. tracheoesophageal septum
2. end of week 5
The tracheoesophageal septum divide cranial end of foregut o which parts and explain their primordium
Septum divides cranial end of foregut into:
Ventral part
Laryngotracheal tube
Primordium of larynx, trachea, bronchi, and lungs
Opening into pharynx becomes primordial laryngeal inlet.
Dorsal part
Primordium of oropharynx and esophagus
The endoderm of the cranial end of laryngotracheal tube from?/
respiratory epithelium lining.
thye laryngeal cartilages are formed from which arch/ arches
4 and 6 pairs of pharyngeal arches
the laryngeal cartilages develop from which cells and layer
mesenchyme derived neural crest cells
mesenchyme cells at the cranial end of laryngotracheal tube proliferate rapidly to form which structure?
paired arytenoid swelling.
which grow towards the tongue
from T shaped laryngeal inlet
Reduce the developing laryngeal lumen to a narrow slit.
what result as a temporal occlusion of laryngeal lumen?
the rapid proliferation of the laryngeal epithelium.
by which week does the above recanalization occur?
10 week
what structure of the larynx form during the process of recanalization?
laryngeal ventricles
what happens to the hypopharyngeal eminence?
it protrusion is produced by the proliferation of mesenchyme in the 3rd and 4th pharyngeal arches
.
results of the protruded hypopharyngeal eminence?
caudal/ posterior—- forms epiglottis
ventral/ anterior — forms posterior 1/3 part of the tongue
Where does the laryngeal muscle develop?
from the myoblast in the 4th and 6th pairs of the pharyngeal arches
innervation of the laryngeal muscle ?
Innervated by laryngeal branches of vagus nerves that supply these arches
The high position of the larynx allow the epiglottis too?
come into contact with the soft palate
the relationship between the epiglottis and soft palate
provide an almost separate respiratory and digestive tract.
What does the splanchnic mesenchyme surrounding laryngotracheal tube form?
cartilage, connective tissue and laryngeal muscle.
what develops during the 4th week at the caudal end of the laryngotracheal diverticulum?
respiratory Bud
in which canals do primary bronchial buds grow laterally into?
pericardioperitoneal canals
pericardioperitoneal canal are primordial of what ?
pleural cavity
Bronchial buds (together with surrounding splanchnic mesenchyme) form:
bronchus and their branches in the lungs
early in the fifth week: connection of each bronchi with trachea enlarges to form primordia of main bronchi
by which do the segmental bronchus form:
by 7th week.
Segmental bronchi (with surrounding mesenchyme) form:
primordia of bronchopumonary segmements
Segmental bronchi (with surrounding mesenchyme) form:
primordia of bronchopumonary segmements
By 24 weeks:
- Approximately 17 orders of branches have formed
- Respiratory bronchioles have developed
Additional seven orders of airways develop after birth
Splanchnic mesenchyme surrounding developing bronchi form:
- Cartilaginous plates of bronchi
- Bronchial smooth muscle & connective tissue
- Pulmonary connective tissue and capillaries
Name the layer acquired by lungs from the splanchnic mesenchyme?
Visceral layer.
content of pseudogladnular stage
- Cartilaginous plates of bronchi
- Bronchial smooth muscle & connective tissue
- Pulmonary connective tissue and capillaries
The canalicular stage
16 - 25 Weeks
Overlaps pseudoglandular stage
- Cranial segments of lungs mature faster than
caudal segments
Lumina of bronchi and terminal bronchioles become larger
Lung tissue becomes highly vascular
what happens during the 24th week of the canalicular stage?
By 24 weeks:
- Each terminal bronchiole has formed two or
more respiratory bronchioles
Each respiratory bronchiole will divide into multiple primordial alveolar ducts
during which week is the pseudoglandular stage occur?
5th and 17th week
Histologically, developing lungs resemble exocrine glands
what happens to the 16th week of the pseudoglandular stage?
all major element of the lungs are developed
expect the one for respiratory exchange
respiration is not possible
fetuses born at this stage will not survive
The saccule stage
many more terminal sac hat have developed and their epithelium thins
capillaries bulge into terminal sacs
what is established by close contact of ————- and ————cells
close contact between epithelium and endothelium cells establishes a blood-air barrier
name the blood-air barrier
alveolar capillary membrane
per
what lines the terminal sacs at the 26th weeks
mainly lined by type 1 pneumocytes
- Squamous epithelial cells of endodermal origin - Gas exchange occurs across these cells
Type II Pneumocytes scattered amongst Type I Pneumocytes
- Rounded secretory epithelial cells of same endodermal
origin
- Secrete pulmonary surfactant
pulmonary surfactant secreted by the type 2 pneumocyte does what?
counteracts/prevents surface tension forces at the air-alveolar interface.
Facilitates expansion of terminal sacs by preventing
collapse of sacs during exhalation
production of surfactant begins.——–?
at 20-22 week
does not reach the needed level till the 24th week -late fetal period.
the production of surfactant increase during———-weeks of pregnancy
last 2 weeks
alveolar stage
terminal sacs comparable to alveoli are present at 32 weeks
-with thin squamous epithelial layer
late fetal peroid
Lungs capable of respiration
- Alveolocapillary membrane thin enough for
effective gas exchange
- Although lungs do not perform this function until birth
- Well developed to function at/from birth
fetal alveolar stage
Primordial alveoli enlarge as lungs expand
Greatest increase in size of lungs increase in number of respiratory bronchioles and primordial alveoli
(rather than increase in size of alveoli)
AFTER Birth
Lung development during first few months after birth characterized by exponential increase in surface area of the air–blood barrier
- Multiplication of alveoli and capillaries
Approximately 150 million primordial alveoli (½ adult number) present in full-term neonate
Adult number of 300 million alveoli achieved by 8 years
name the 3 factors important for normal lung development.
- Adequate thoracic space for lung growth
- Fetal breathing movements
- Adequate amniotic fluid volume
Define Areation of lung
involves rapid replacement of interalveolar fluid with air
how is the fluid in lungs cleared?
via mouth and nose by pressure on fetal thorax during vaginal delivery
into pulmonary capillaries, arteries and veins
respiratory distress syndrome
Results from surfactant deficiency
Lungs are underinflated and alveoli contain a fluid that resembles a hyaline membrane
Prolonged intrauterine asphyxia (impaired or absent gas exchange) may cause irreversible changes in Type II Pneumocytes making them incapable of surfactant production
Other factors such as sepsis and pneumonia may inactivate surfactant
