Development of Lung Flashcards
Appearance of lung buds in 4 weeks old embryo
Initially the lung buds appear as ____
a respiratory (or laryngotracheal) diverticulum, a ventral outgrowth of foregut endoderm.
Appearance of lung buds in 4 weeks old embryo
Initially the lung buds appear as a respiratory (or laryngotracheal) diverticulum, a ventral outgrowth of ____
foregut endoderm.
Appearance of lung buds in 4 weeks old embryo
Initially the lung buds appear as a respiratory (or laryngotracheal) diverticulum, a ventral outgrowth of foregut endoderm.
→ It is _____ (name of the process?)
a mesoderm dependent process
Appearance of lung buds in 4 weeks old embryo
Initially the lung buds appear as a respiratory (or laryngotracheal) diverticulum, a ventral outgrowth of foregut endoderm.
→ It is a mesoderm dependent process: Retinoic acid produced by adjacent mesoderm induces expression of TBX4 in some foregut endoderm cells and leads to their ___
differentiation to respiratory diverticulum.
Appearance of lung buds in 4 weeks old embryo
Initially the lung buds appear as a respiratory (or laryngotracheal) diverticulum, a ventral outgrowth of foregut endoderm.
→ It is a mesoderm dependent process: _____ produced by adjacent mesoderm induces expression of TBX4 in some foregut endoderm cells and leads to their differentiation to respiratory diverticulum.
Retinoic acid
Appearance of lung buds in 4 weeks old embryo
Initially the lung buds appear as a respiratory (or laryngotracheal) diverticulum, a ventral outgrowth of foregut endoderm.
→ It is a mesoderm dependent process: Retinoic acid produced by adjacent mesoderm induces expression of ____ in some foregut endoderm cells and leads to their differentiation to respiratory diverticulum.
TBX4
Appearance of lung buds in 4 weeks old embryo
Initially the lung buds appear as a respiratory (or laryngotracheal) diverticulum, a ventral outgrowth of foregut endoderm.
→ It is a mesoderm dependent process: Retinoic acid produced by adjacent mesoderm induces expression of TBX4 in some ___ and leads to their differentiation to respiratory diverticulum.
foregut endoderm cells
Separation of the trachea and esophagus
____ invaginates the surrounding mesenchyme.
The respiratory diverticulum
Separation of the trachea and esophagus
The respiratory diverticulum invaginates the surrounding mesenchyme.
→ ___ appear above the respiratory diverticulum.
→ These longitudinal ridges eventually fuse to separate trachea from esophagus.
The respiratory diverticulum
Separation of the trachea and esophagus
The respiratory diverticulum invaginates the surrounding mesenchyme.
→ Tracheo-esophageal (or esophago-tracheal) ridges appear above the respiratory diverticulum.
→ These longitudinal ridges eventually fuse to separate ____ from ____
trachea from esophagus.
Separation of the trachea and esophagus
First ___ is formed, which is followed by the separation of the trachea and the esophagus.
a tracheo-esophageal septum
Development of Larynx
Cartilages and muscle originate from the mesenchyme of ____ and ____
the 4th and 6th Pharyngeal Arches
Development of Larynx
All laryngeal muscles are innervated by branches of the 10th Cranial Nerve (Vagus Nerve)
- Superior Laryngeal Nerve comes from ___ (branchial arch?)
- Recurrent Laryngela Nerve ______ (branchial arch?)
- 4th arch
- 6th arch
Development of Larynx
Cartilages and muscle originate from the mesenchyme of the 4th and 6th Pharyngeal Arches
→ Mesenchyme of the two arches create the cartilages which are ___- (3)
- Thyroid
- Cricoid
- Arytenoid
Development of Larynx
____ proliferates so that the lumen of the organ is temporarily occluded
The laryngeal epithelium
Development of Larynx
The laryngeal epithelium proliferates so that the lumen of the organ is temporarily occluded
→ By then it is recanalized to create ____
the Laryngeal Ventricles
(Definition of recanalization
: the process of restoring flow to or reuniting an interrupted channel of a bodily tube(such as a blood vessel or vas deferens))
Development of Larynx
The laryngeal epithelium proliferates so that the lumen of the organ is temporarily occluded
→ By then it is recanalized to create a pair of lateral recesses called the Laryngeal Ventricles which are bounded by folds of tissue that become both____ and ____
the False and True Vocal Folds
Development of Larynx
Cartilages and muscle originate from the mesenchyme of the 4th and 6th Pharyngeal Arches
→ ____ changes its shape from a sagittal slit to a T-shaped opening
Laryngeal orifice
Development of Larynx
All laryngeal muscles are innervated by branches of____
the 10th Cranial Nerve (Vagus Nerve)
Development of the trachea
Endodermal lining distal to the larynx differentiates into the ___ and ___
epithelium and glands of the trachea.
Development of the trachea
The cartilage, connective tissue and muscles of the trachea derive from ____
the mesoderm.
Patterning of the lung
What is branching (dichotomic) morphogenesis?
- The process of repetitive growth and branching
Patterning of the lung
Trachea branched into ____
two primary bronchi (left and right)
Patterning of the lung
Trachea branched into two primary bronchi (left and right)
→ Left primary bronchus into _____
two secondary bronchi (corresponding to the two lobes of the left lung)
Patterning of the lung
Trachea branched into two primary bronchi (left and right)
→ Left primary bronchus into two secondary bronchi (corresponding to the two lobes of the left lung)
→ _____ form on the right
Three secondary buds (corresponding to the 3 lobes of the right lung)
Patterning of the lung
Trachea branched into two primary bronchi (left and right)
→ Left primary bronchus into two secondary bronchi (corresponding to the two lobes of the left lung)
→ Three secondary buds form on the right (corresponding to the 3 lobes of the right lung)
→ ____ form in the right lung
Ten tertiary (segmental) bronchi
Patterning of the lung
Trachea branched into two primary bronchi (left and right)
→ Left primary bronchus into two secondary bronchi (corresponding to the two lobes of the left lung)
→ Three secondary buds form on the right (corresponding to the 3 lobes of the right lung)
→ Ten tertiary (segmental) bronchi form in the right lung
→ ____ form in the left lung
Eight bronchi
Patterning of the lung
Trachea branched into two primary bronchi (left and right)
→ Left primary bronchus into two secondary bronchi (corresponding to the two lobes of the left lung)
→ Three secondary buds form on the right (corresponding to the 3 lobes of the right lung)
→ Ten tertiary (segmental) bronchi form in the right lung
→ Eight bronchi form in the left lung
→ establishing ___ of the adult human lung.
the 18 brochopulmonary segments
Patterning of the lung
By the end of the sixth month, ___ have formed to produce respiratory bronchioli.
→ Additional divisions occur during postnatal life for a total of 23 branching events.
17 generations of subdivisions
Patterning of the lung
By the end of ____ (month?), 17 generations of subdivisions have formed to produce respiratory bronchioli.
→ Additional divisions occur during postnatal life for a total of 23 branching events.
the sixth month
Signaling molecules driving lung budding and branching morphogenesis
____ induce mesenchyme to secrete fibroplast growth factor 10 (FGF10), which acts on FGF receptor 2 to induce epithelial growth.
Tbx4 together with retinoic acid
Growth of lungs into the body cavity
____ is surrounded by visceral (splanchnopleuric) mesoderm and suspended in body wall by dorsal mesentery
Foregut endoderm
Growth of lungs into the body cavity
Foregut endoderm is surrounded by ____ and suspended in body wall by dorsal mesentery
visceral (splanchnopleuric) mesoderm
Growth of lungs into the body cavity
Foregut endoderm is surrounded by visceral (splanchnopleuric) mesoderm and suspended in body wall by dorsal mesentery
→ As lungs grow, they expand into ____
the body cavity
Growth of lungs into the body cavity
The epithelial components of the lung are derived from ____
the endoderm
Differentiation of pleural membranes
The lungs buds expand in the pleural cavities surrounded by ____ and _____.
the parietal and visceral pleura
Differentiation of pleural membranes
The lungs buds expand in the pleural cavities surrounded by the parietal and visceral pleura.
→ They “punch” into the visceral mesoderm.
visceral mesoderm
Differentiation of pleural membranes
The lungs buds expand in the pleural cavities surrounded by the parietal and visceral pleura.
→ They “punch” into the visceral mesoderm.
→ Consequently, the visceral pleura extends between ____
the lobes of the lung.
Differentiation of pleural membranes
The mesoderm, which covers the outside of the lung, develops into ____
the visceral pleura.
Differentiation of pleural membranes
___ which covers the outside of the lung, develops into the visceral pleura.
The mesoderm
Differentiation of pleural membranes
The somatic mesoderm, covering the body wall from the inside, becomes____
the parietal pleura.
Differentiation of pleural membranes
____, covering the body wall from the inside, becomes the parietal pleura.
The somatic mesoderm
Differentiation of pleural membranes
The mesoderm, which covers the outside of the lung, develops into the visceral pleura.
The somatic mesoderm, covering the body wall from the inside, becomes the parietal pleura.
→ The space between is ___
the pleural cavity.
Maturation of lung is divided into 4 periods which are
- Pseudoglandular (5 - 17 weeks)
- Canalicular (16 - 25 weeks)
- Saccular (24 weeks - birth)
- Alveolar (late fetal period - childhood)
(These periods overlap each other because the cranial segments of the lungs mature faster than the caudal ones.)
Maturation of the lung - Pseudograndular period (5-17 weeks)
Developing lungs somewhat resemble ____
By 17 weeks all major elements of the lung have formed except for those involved in ___
- an exocrine gland during this period.
- gas exchange (alveoli).
Maturation of the lung - Pseudograndular period (5-17 weeks)
What is not possible during this period?
→ Will the fetuses be survived during this period?
Respiration is NOT possible.
→ Fetuses born during this period are unable to survive.
Maturation of the lung - Canalicular period (16-25 weeks)
Lung tissue becomes highly ___
vascular (vascularization).
Maturation of the lung - Canalicular period (16-25 weeks)
Lung tissue becomes highly vascular (vascularization).
→ ___ and ____ become larger.
Lumen of bronchi and terminal bronchioles
Maturation of the lung - Canalicular period (16-25 weeks)
Lung tissue becomes highly vascular (vascularization).
→ Lumen of bronchi and terminal bronchioles become larger.
→ By 24 weeks each terminal bronchiole has given rise to___
two or more respiratory bronchioles.
Maturation of the lung - Canalicular period (16-25 weeks)
Lung tissue becomes highly vascular (vascularization).
→ Lumen of bronchi and terminal bronchioles become larger.
→ By 24 weeks each terminal bronchiole has given rise to two or more respiratory bronchioles.
→ The respiratory bronchioles divide into ____ that make up the alveolar ducts. Thus, airspaces are multiplicated by partitioning (septation).
3 to 6 tubular passages called canaliculi
Maturation of the lung - Canalicular period (16-25 weeks)
Lung tissue becomes highly vascular (vascularization).
→ Lumen of bronchi and terminal bronchioles become larger.
→ By 24 weeks each terminal bronchiole has given rise to two or more respiratory bronchioles.
→ The respiratory bronchioles divide into 3 to 6 tubular passages called canaliculi that make up ______ Thus, airspaces are multiplicated by partitioning (septation).
the alveolar ducts.
Maturation of the lung - Canalicular period (16-25 weeks)
Lung tissue becomes highly vascular (vascularization).
→ Lumen of bronchi and terminal bronchioles become larger.
→ By 24 weeks each terminal bronchiole has given rise to two or more respiratory bronchioles.
→ The respiratory bronchioles divide into 3 to 6 tubular passages called canaliculi that make up the alveolar ducts.
→ Thus, airspaces are multiplicated by ____
partitioning (septation).
Maturation of the lung - Canalicular period (16-25 weeks)
____ develop at the end of respiratory bronchioles (differentiation)
Some thin-walled terminal sacs (primordial alveoli)
Maturation of the lung - Canalicular period (16-25 weeks)
Some thin-walled terminal sacs (primordial alveoli) develop at the end of ____ (differentiation)
respiratory bronchioles
Maturation of the lung - Canalicular period (16-25 weeks)
Is respiration possible in this period? Will fetuses be survived?
Respiration is possible at the end of this period.
Fetus born at the end of this period may survive if given intensive care (but often die because of the immaturity of respiratory as well as other systems)
Maturation of the lung - Saccular period (24 weeks-birth)
Many more ___ develop.
terminal sacs
Maturation of the lung - Saccular period (24 weeks-birth)
Many more terminal sacs develop.
→ The epithelial cells of the alveoli and the endothelial cells of the capillaries come in intimate contact and establish ____
the blood-air barrier.
Maturation of the lung - Saccular period (24 weeks-birth)
The terminal sacs are lined by ___- (2 types)
Squamous type I pneumocytes and
Rounded secretory, type II pneumocytes, which secrete surfactant (a mixture of phospholipids and special proteins
Maturation of the lung - Alveolar period (32 weeks-8 years)
At the beginning of the alveolar period, each respiratory bronchiole terminates in _____, separated from one another by loose connective tissue.
a cluster of thin-walled terminal saccules
Maturation of the lung - Alveolar period (32 weeks-8 years)
At the beginning of the alveolar period, each respiratory bronchiole terminates in a cluster of thin-walled terminal saccules, separated from one another by loose connective tissue.
→ These terminal saccules represent _____
future alveolar sacs.
Maturation of the lung - Alveolar period (32 weeks-8 years)
What is alveolization?
terminal sacs
Development of the lung after birth
Growth of lungs after birth is due primarily to____
increase of respiratory bronchioles and alveoli
(not to the growth of the size of alveoli.)
Breathing movements of the fetus
Take ____ into the pulmonary tree
amnionic fluid
The role of surfactant proteins
Surfactant A?
activates macrophages to elicit uterine contractions
The role of surfactant proteins
Surfactant B?
the protein organizes into tubular structures, which are efficient at reducing surface tension
The role of surfactant proteins
Surfactant C?
enhances the functioning of surfactant phospholipids
The role of surfactant proteins
Surfactant D?
important in host defense
