DEVELOPMENT OF RESPIRATORY SYSTEM by Shapi. MD.pdf

HUMAN ANATOMY
• EMBRYOLOGY
• DEVELOPMENT OF THE
RESPIRATORY SYSTEM
• Dr. Chongo Shapi, (BSc. HB, MBChB)
• Medical Doctor
26/11/22 Dr. Chongo Shapi (BSc. HB, MBChB) 1

FORMATION OF THE LUNG BUDS
• In 4 weeks old embryo, the respiratory
diverticulum (lung bud) appears as an outgrowth
from the ventral wall of the foregut.
• Epithelium of the internal lining of the larynx,
trachea, and bronchi, as well as that of the lungs,
is entirely of endodermal origin.
2

3

FORMATION OF THE LUNG BUDS
• The cartilaginous, muscular, and connective tissue
components of the trachea and lungs are derived
from splanchnic mesoderm surrounding the
foregut.
• Two tracheoesophageal folds fuse to form the
tracheoesophageal septum which divides the
foregut into a dorsal portion, the esophagus, and
a ventral portion, the trachea and lung buds.
• This septum divides the cranial part of the foregut
into a ventral part, the laryngotracheal tube and a
dorsal part, oropharynx and esophagus
4

5

DEVELOPMENT OF LARYNX
• The internal lining of the larynx: From
Endoderm
• The cartilages and muscles: From
mesenchyme of the 4th and 6th Pharyngeal
arches.
• Proliferating mesenchyme of the two arches
transforms into the thyroid, cricoid, and
arytenoid cartilages.
• Temporary occlusion of the laryngeal lumen
occurs due to the proliferation of laryngeal
epithelium.
7

DEVELOPMENT OF LARYNX
• Recanalization produce a pair of lateral recesses,
the laryngeal ventricles (recesses are bounded by
folds of tissue that differentiate into the false and
true vocal cords)
• Since musculature of the larynx is derived from
mesenchyme of the 4th & 6th pharyngeal arches, all
laryngeal muscles are innervated by branches of
the 10th cranial nerve (vagus nerve).
• The superior laryngeal nerve innervates derivatives
of the fourth pharyngeal arch, and the recurrent
laryngeal nerve innervates derivatives of the sixth
pharyngeal arch.
8

Development of Larynx
9
Pharyngeal arches: Each arch contains a cartilaginous component, a
cranial nerve, an artery, and a muscular component.

DEVELOPMENT OF TRACHEA, BRONCHI & LUNGS
• During its separation from the foregut, the lung bud
forms the trachea and two lateral outpocketings, the
bronchial buds.
• At the beginning of the 5th week, each of these buds
enlarges to form right and left main bronchi.
• The right then forms three secondary bronchi, and
the left, two.
• By the end of the 6th month, approximately 17
generations of subdivisions have formed.
12

DEVELOPMENT OF TRACHEA, BRONCHI & LUNGS
▪ Before the bronchial tree reaches its final shape,
however, an additional six divisions form during
postnatal life.
▪ As the lungs develop they acquire a layer of visceral
pleura from splanchnic mesenchyme
▪ The thoracic body wall becomes lined by a layer of
parietal pleura derived from the somatic mesoderm
13

15
DEVELOPMENT OF TRACHEA, BRONCHI &
LUNGS

17

19
MATURATION OF THE LUNGS

• Scattered among the squamous epithelial cells are rounded secretory epithelial cells, type
II alveolar cells or pneumocytes
• Type II pneumocytes secrete a mixture of phospholipids called surfactant
20
MATURATION OF THE LUNGS

DEVELOPMENT OF PLEURA
• The pleuroperitoneal and pleuropericardial folds
separate the pericardioperitoneal canals from the
peritoneal and pericardial cavities, respectively, and
the remaining spaces form the primitive pleural
cavities.
• The splanchnic mesoderm, which covers the outside
of the lung, develops into the visceral pleura.
21

22
Growth of the lung buds into the pericardioperitoneal canals.
Note the pleuropericardial folds.

23

• The somatic mesoderm layer, covering the body
wall from the inside, becomes the parietal pleura.
• The space between the parietal and visceral pleura
is the pleural cavity.
24

25
The Visceral and Parietal Pleura

CONGENITAL ANOMALIES OF THE RESPIRATORY
SYSTEM
• Abnormalities in partitioning of the esophagus
and trachea by the tracheoesophageal septum
result in esophageal atresia with or without
tracheoesophageal fistulas (TEFs).
26

CONGENITALANOMALIES OF THE
RESPIRATORY SYSTEM
27

CONGENITAL ANOMALIES OF THE RESPIRATORY
SYSTEM
▪ Respiratory distress syndrome (RDS) or
(Hyaline membrane disease): When surfactant is
insufficient,
the air-water (blood) surface membrane tension becomes
high,
so alveoli will collapse during expiration.
▪ Blind-ending trachea with absence of lungs.
▪ Agenesis of one lung.
28

CONGENITAL ANOMALIES OF THE
RESPIRATOR SYSTEM
• Abnormal divisions of the bronchial tree.
• Ectopic lung lobes arising from the trachea or
esophagus from additional respiratory buds of
the foregut that develop independently of the
main respiratory system.
• Congenital cysts of the lung, which are formed
by dilation of terminal or larger bronchi.
29

THANK YOU!
THE END!

DEVELOPMENT OF RESPIRATORY SYSTEM by Shapi. MD.pdf

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