Trachea, Bronchi, Lungs Flashcards
The lower respiratory organs i.e. larynx, trachea, bronchi and lungs begin to form during the — week
•The respiratory primordium appears as a median outgrowth from the —- wall of the foregut- ——- groove
The lower respiratory organs i.e. larynx, trachea, bronchi and lungs begin to form during the fourth week
•The respiratory primordium appears as a median outgrowth from the ventral wall of the foregut- laryngotracheal groove
Respiratory Diverticulum
•By the end of — week, the laryngotracheal groove has evaginated to form a pouch-like structure called —-
•This diverticulum elongates and is invested with ——mesenchyme and its distal end enlarges to form a globular —//
Respiratory Diverticulum
•By the end of 4th week, the laryngotracheal groove has evaginated to form a pouch-like structure- respiratory diverticulum
•This diverticulum elongates and is invested with splanchnic mesenchyme and its distal end enlarges to form a globular respiratory bud
Soon 2 longitudinal ridges separate respiratory bud from the foregut by —-
•Subsequently the 2 ridges fuse to form the —-
•Dividing the foregut into a —- part-laryngotracheal tube (primordium of larynx, trachea, bronchi and lungs) and a —- part (primordium of oropharynx and esophaus)
Soon 2 longitudinal ridges separate it from the foregut- tracheoesophageal ridges
•Subsequently the 2 ridges fuse to form the tracheoesophageal septum
•Dividing the foregut into a ventral part-laryngotracheal tube (primordium of larynx, trachea, bronchi and lungs) and a dorsal part (primordium of oropharynx and esophaus)
After formation of the septum , the laryngotracheal tube separates from the foregut and forms the;
➢——
➢——
After formation of the septum , the laryngotracheal tube separates from the foregut and forms the;
➢Trachea
➢The bronchial (lung) buds.
Development of Trachea
•The endodermal lining of the laryngotracheal tube differentiates into the —- and —— of the trachea and the —— epithelium
•The cartilages, CT, and muscles of the trachea are derived from the ——- mesenchyme surrounding the laryngotracheal tube
Development of Trachea
•The endodermal lining of the laryngotracheal tube differentiates into the epithelium and glands of the trachea and the pulmonary epithelium
•The cartilages, CT, and muscles of the trachea are derived from the splanchnic mesenchyme surrounding the laryngotracheal tube
DEVELOPMENT OF THE BRONCHI
•The resp bud that developed at the caudal end of laryngotracheal tube during the 4th week divides into two outpouches called – ——
•These endodermal buds grow laterally into the ——— canals, the primordia of the pleural cavities
• Together with the surrounding splanchnic mesenchyme, the bronchial buds differentiate into —- and their ramifications in the —-
DEVELOPMENT OF THE BRONCHI
•The resp bud that developed at the caudal end of laryngotracheal tube during the 4th week divides into two outpouchings – pry bronchial buds.
•These endodermal buds grow laterally into the pericardioperitoneal canals, the primordia of the pleural cavities
• Together with the surrounding splanchnic mesenchyme, the bronchial buds differentiate into bronchi and their ramifications in the lungs
—- week each of the pry bronchial buds enlarge to form the — or —- bronchi.
•The main bronchi subdivides into —- bronchi.
•Lobar bronchi divides into —- bronchi around the — week.
5THweek- each of the bud enlarge to form the main or principal bronchi.
•The main bronchi subdivides into lobar bronchi.
•Lobar bronchi divides into segmental bronchi around the 7th week.
Each segmental bronchus with its surrounding mass of mesenchyme is the primordium of a —— segment
•By — weeks respiratory bronchioles have developed
•The lungs acquire a layer of visceral pleura from the —— mesoderm
•——mesoderm layer covering body wall becomes parietal pleura
•Space btw the two mesoderms form the —-
Each segmental bronchus with its surrounding mass of mesenchyme is the primordium of a bronchopulmonary segment
•By 24 weeks respiratory bronchioles have developed
•The lungs acquire a layer of visceral pleura from the splanchnic mesoderm
•Somatic mesoderm layer covering body wall becomes parietal pleura
•Space btw the two- pleural cavity
Maturation of the lungs is divided into five periods:
Embryonic
Pseudoglandular
Cannicular
Terminal sac
Alveolar
EMBRYONIC PERIOD
●It occurs between the — to — week of gestation.
•During this period the tracheobronchial bud divides to form the ———— to the level of the segmental bronchi.
EMBRYONIC PERIOD
●It occurs between the 4th to 6th week of gestation.
•During this period the tracheobronchial bud divides to form the proximal airways to the level of the segmental bronchi
PSEUDOGLANDULAR PERIOD
— to — weeks
•The terminal bronchiole resembles an —— gland during this period.
•Branching has continued to form ——
•No respiratory bronchioles or alveoli are ——
•By — weeks all major elements of the lung have formed, except those involved with gas exchange.
PSEUDOGLANDULAR PERIOD(6- 17 WEEKS)
•The terminal bronchiole resembles an exocrine gland during this period.
•Branching has continued to form terminal bronchioles.
•No respiratory bronchioles or alveoli are present.
•By 17 weeks all major elements of the lung have formed, except those involved with gas exchange.
CANNALICULAR PERIOD
—- to — week
• Each terminal bronchioles divides into two or more —-.
•These bronchioles divides into — to — alveolar ducts.
•These ducts end in —— (primitive alveoli)
•The tissues become more vascular as capillaries develop.
CANNALICULAR PERIOD (17-26 WEEKS)
• Each terminal bronchioles divides into two or more respiratory bronchioles.
•These bronchioles divides into 3 to 6 alveolar ducts.
•These ducts end in terminal sacs (primitive alveoli)
•The tissues become more vascular as capillaries develop.
TERMINAL SAC PERIOD
•Terminal period (— weeks to —-)
•Many more terminal sacs (primitive alveoli) develops and their epithelium becomes very ——.
•Capillaries begin to bulge into these developing —-.
•The intimate contact between epithelial and endothelial cells establishes the ——-barrier.
•This permits adequate gas exchange
TERMINAL SAC PERIOD
•Terminal period (24 weeks to birth)
•Many more terminal sacs (primitive alveoli) develops and their epithelium becomes very thin.
•Capillaries begin to bulge into these developing alveoli.
•The intimate contact between epithelial and endothelial cells establishes the blood-air barrier.
•This permits adequate gas exchange for
TERMINAL SAC PERIOD
•By — weeks, the terminal sacs are lined mainly by —- epithelial cells of endodermal origin
➢——- cells or —- - gas exchange function.
➢——- cells — which secrete pulmonary surfactant.
Sufactant production begins in the — week and increases during the last —wks of pregnancy.
•fetuses born prematurely at — to — wks after fertilization may survive intensive care but may suffer respiratory distress because of surfactant deficiency
•Survival has improved with the use of antenatal ———
Corticosteroids induces —— production, also administration of maternal ——during pregnancy speed up fetal lung development and surfactant production
Sufactant production begins in the 20th week and increases during the last 2 wks of pregnancy.
•fetuses born prematurely at 24-26 wks after fertilization may survive intensive care but may suffer respiratory distress because of surfactant deficiency
•Survival has improved with the use of antenatal corticosteroids
Corticosteroids induces surfactant production, also administration of maternal glucocorticoid during pregnancy speed up fetal lung development and surfactant production
ALVEOLAR PERIOD (LATE FETAL PERIOD TO CHILDHOOD)
•Structures analogous to alveoli are present at — weeks of gestation
•At the beginning of the alveolar period, each respiratory bronchiole terminates in a cluster of thin-walled ——
•Characteristic mature alveoli do not form until after birth; about —% of alveoli develop postnatally
ALVEOLAR PERIOD (LATE FETAL PERIOD TO CHILDHOOD)
•Structures analogous to alveoli are present at 32 weeks of gestation
•At the beginning of the alveolar period, each respiratory bronchiole terminates in a cluster of thin-walled terminal sacs.
•Characteristic mature alveoli do not form until after birth; about 95% of alveoli develop postnatally
