Respiratory Embryology Flashcards
What occurs at week 4-5 in development of the respiratory system?
Respiratory diverticulum forms and branches into left and right bronchial buds
Stem of the diverticulum will differentiate into trachea and larynx
Respiratory development begins at week 4 when respiratory diverticulum forms and branches into left and right bronchial buds. The stem of the diverticulum will differentiate into trachea and larynx during week 5.
What occurs at week 5-6 in development of the respiratory system?
Branching yields secondary bronchial buds, which represent future lung lobes
What occurs between week 6 and 7 in development of the respiratory system?
Branching yields tertiary bronchial buds, which represent future bronchopulmonary segments
At what week of development do the terminal bronchioles form? What other important developmental process has just been completed?
Week 16
Formation of pericardial sac is complete at this point
What events take place between week 16 and 28 in the development of the cardiopulm system?
Respiratory bronchioles form, surrounding mesenchyme becomes highly vascular; the first terminal sacs (primitive alveoli) form
Pleuroperitoneal membranes have closed off pericardioperitoneal canals; diaphragm begins to differentiate
At what point in development of the respiratory system do the terminal sacs begin to differentiate into mature alveoli? When are the alveoli fully mature?
At birth; alveoli will then continue to form through the eighth year of life
__________ _________ = median outgrowth that appears in the floor of the primitive pharynx
Laryngotracheal groove
The laryngoracheal groove is the median outgrowth that appears in the floor of the primitive pharynx. It will form the _________ _________, or lung bud which is the primodium of the _________ _________
Laryngotracheal diverticulum
Tracheobronchial tree
What is the embryologic origin of the pulmonary epithelium and glands of larynx, trachea, and bronchi?
Endoderm of laryngotracheal groove
What is the embryologic origin of the connective tissue, cartilage, and smooth muscle in the structures of the tracheobronchial tree, thus surrounding the foregut of the developing embryo?
Splanchnic mesoderm (from lateral plate)
During development of the lungs, the distal end of the laryngotracheal diverticulum (lung bud) forms the ________ ________, which grows in the ______ direction and bifurcates at day 26-28
Respiratory bud; ventrocaudal
After the respiratory buds grow ventrocaudally and bifurcate around day 26-28, they will undergo further branching. The branching pattern of the lung _________ is regulated by surrounding __________
Endoderm; mesoderm
How many orders of airways form after birth? How many rounds of branching does this require?
7 orders of airways form after birth
Goes through 16-17 rounds of branching
The primary bronchial buds are rudiments of what structures?
Lungs and primary bronchi
When do primary bronchial buds begin branching to form secondary bronchial buds?
During the 5th week of development
What structures to the secondary bronchial buds form?
Right: Superior, middle, inferior (3)
Left: Superior, inferior (2)
_________ bronchi form by the 7th week
Segmental
Segmental bronchi form by the 7th week. What structures have formed by 24 weeks?
Bronchopulmonary segments
By 24 weeks, the bronchopulmonary segments have formed. These consist of what 2 components?
What other structures have formed at this point?
Segmental bronchi + mesenchyme
Respiratory bronchioles have also formed
Maturation of the lung epithelium begins at 5-17 weeks with ____________ epithelium, which may appear similar to exocrine gands
Pseudoglandular
Maturation of the lung epithelium begins at 5-17 weeks with pseudoglandular epithelium, which may appear similar to exocrine gands. All major elements of the lung have formed, except which ones? Can the fetus survive at this point?
All major elements have formed except those involved with gas exchange, so the fetus cannot survive
Lung epithelium is pseudoglandular between 5-17 weeks. Pseudoglandular then overlaps with development of ________ epithelium between 16-25 weeks which is associated with vascularization of lung tissue
Canalicular
Lung tissue is canalicular between 16-25 weeks. What lung structures have formed at this point? Can the fetus survive?
Respiratory bronchioles
Primordial alveoli and sacs present (primitive alveoli)
+/- survival rates depending on thickness of these alveoli at birth (want them thin enough for adequate gas exchange)
During maturation of the lungs:
5-17 weeks = pseudoglandular
16-25 weeks = canalicular
What forms between 24 weeks-birth? Can the fetus survive?
Terminal sac
At this point numerous alveoli form, epithelium is thin with increased vascularization
Gas exchange can occur, so the fetus can survive
When the terminal sac forms between 24 weeks and birth, numerous alveoli form and epithelium is thin with increased vascularization. What 3 things are associated with this epithelium?
Type I pneumocytes
Type II pneumocytes
Lymphatic capillaries
During maturation of the lungs:
5-17 weeks = pseudoglandular
16-25 weeks = canalicular
24 weeks-birth = terminal sac
What is the next phase in lung development, occurring between 32 weeks and 8 years of age?
Alveolar
Formation of alveolocapillary membrane, primitive alveoli, and mature alveoli
T/F: approximately 5% of mature alveoli develop postnatally
False! About 95% of mature alveoli develop postnatally
Alveolar development is largely completed at what age?
3 years
[however, new alveoli are added until 8 years of age]
As the bronchi develop, ______ ______ is critical to the formation of cartilaginous bronchial plates, bronchial smooth muscle and CT, and pulmonary CT + capillaries
Splanchnic mesoderm
As the bronchi develop, the splanchnic mesoderm is critical to the formation of what 3 things?
Cartilaginous bronchial plates
Bronchial smooth muscle + CT
Pulmonary CT + capillaries
Lungs acquire a layer of ______ _______ from the splanchnic mesenchyme. With expansion, the lungs and pleural cavities grow in the _____ direction into the mesenchyme of the body wall, and are soon positioned close to the heart
Visceral pleura; caudal
Lungs acquire a layer of visceral pleura from the splanchnic mesenchyme. With expansion, the lungs and pleural cavities grow in the caudal direction into the mesenchyme of the body wall, and are soon positioned close to the heart.
The thoracic body wall becomes lined with a layer of parietal pleura which is derived from _______ _________
Somatic mesoderm (from lateral plate mesoderm)
** contrast with visceral pleura which is derived from splanchnic mesoderm (also from lateral plate mesoderm)
What is the space called between the parietal and visceral pleura?
Pleural cavity
The proximal end of the laryngotracheal diverticulum forms what 2 structures?
Trachea and larynx
The larynx opens into the pharynx via the _______; the passageway is located at the original point of evagination of the diverticulum.
Glottis
[note: the glottis eventually becomes associated with the vocal folds]
Structures between the trachea and lung have similar embryologic origin; the cartilage, CT, and smooth muscle of the trachea is derived from ______ ______, while the glands and epithelium are ________ derived
Splanchnic mesoderm
Endodermally
________ _______ = condition also known as “blind esophagus” where the esophagus contains a pouch that does not go anywhere. Food may become trapped –> infection risk, and there is diminished ability to maintain nutrition
Esophageal atresia