3.7b Development of Air Passageways

Question 1

Respiratory primordium:

Answer 1

-develops as a ventral groove in the floor of the foregut

Question 2

Laryngo-tracheal groove:

Answer 2

-located at about 4th pharyngeal arch
-deepens and forms an elongated outgrowth

Question 3

Laryngo-tracheal groove becomes separated:

Answer 3

-from foregut by 2 tracheo-oesophageal grooves (one on each side)
>approach towards each other and fuse to form the trachea-oesophageal septum

Question 4

Portion of foregut cranial to trachea-oesophageal area:

Answer 4

-will become the pharynx

Question 5

Laryngo-tracheal tube:

Answer 5

-eventually splits into 2 bronchial buds

Question 6

Primitive trachea:

Answer 6

-endodermally lined but mesenchyme around it is neural crest derived and gives rise to cartilaginous tracheal rings

Question 7

Primitive trachea mesenchyme:

Answer 7

-contributes to smooth muscle of trachea

Question 8

Primitive trachea endodermal lining:

Answer 8

-comes ciliated, pseudo-stratified respiratory epithelium
>rich in Goblet cells

Question 9

Periods of bronchi and lungs:

Answer 9

-embryonic
-fetal
-postnatal

Question 10

Embryonic period: simple

Answer 10

-primordium of lungs and bronchi formed

Question 11

Fetal period: simple

Answer 11

-ramified bronchi are formed and preliminary structures produced for gas exchange

Question 12

Fetal period subdivided:

Answer 12

-pseudo-glandular
-canalicular
-saccular
-alveolar

Question 13

Postnatal period: simple

Answer 13

-definitive structures for gas exchange called alveoli develop
-lungs take on their adult form

Question 14

Embryonic period: lung buds

Answer 14

-fork or grow caudo-laterally becoming principle bronchi
>left bud grows more laterally
*branching morphogenesis

Question 15

Principle bronchi (embryonic period):

Answer 15

-bud into lobar bronchi

Question 16

Lobar bronchi (embryonic period):

Answer 16

-push into developing pleural cavity
-surrounded by mesenchyme that forms pleura
-bud into segmental bronchi

Question 17

Tracheal bronchus (embryonic period):

Answer 17

-cattle, sheep and pigs
-develops from trachea to supply right cranial lobe

Question 18

Left and right pleuro-pericardial cavity:

Answer 18

-surround the initially developing heart and lungs

Question 19

One pericardial cavity:

Answer 19

-when ventral and dorsal mesocardium are lost
>heart is suspended in one cavity

Question 20

Pleuro-pericardial folds (folds of mesoderm):

Answer 20

-grow medially into left and right part of the pleuro-pericardial cavity
*eventually fuse to separate the pleural from the pericardial cavity

Question 21

Pseudo-glandular period:

Answer 21

-gland like branching occurs with Segmental bronchi dividing up to 20 times (species dependant) into Terminal bronchioles

Question 22

Terminal bronchioles:

Answer 22

-lined with endodermal derived epithelium

Question 23

Canalicular period:

Answer 23

-terminal bronchioles divide further into Respiratory bronchioles
>more divisions creates secondary tubules called canalicules or alveolar ducts

Question 24

Saccular period:

Answer 24

-Terminal saccules divide further into Blind Saccules that will differentiate into Alveoli

Question 25

Alveolar period:

Answer 25

-Alveoli differentiation occurs most distally first
-epithelium differentiates into squamous Type I alveolar cells and cuboidal Type II alveolar cells
*provided primitive alveoli that allowed newborn to breath
>mature alveoli form after birth

Question 26

During gestation:

Answer 26

-lungs were filled with fluid secreted from developing alveolar cells and glands in system and from amniotic fluid that was aspirated by fetus (this gets expelled)

Question 27

Postnatal period:

Answer 27

-marked by extensive growth of respiratory bronchioles, saccules and alveolar development
-any remaining fluid is absorbed by epithelial cells

Question 28

NEED TO KNOW?

Avian lungs:

Answer 28

-do not change in volume during inspiration and expiration
-abdominal inspiratory muscles dilate air sacs to reduce pressure and thus air-rushes in

Question 29

-do not change in volume during inspiration and expiration
-abdominal inspiratory muscles dilate air sacs to reduce pressure and thus air-rushes in

Answer 29

-compress air sacs forcing outward movement of air

Question 30

Avian lungs consist of:

Answer 30

-primary bronchus (mesobronchus)
-secondary bronchus
-tertiary bronchus (parabronchus)
-atria
-air capillaries

Question 31

Mesobronchus: (primary bronchus)

Answer 31

-lined by pseudostratified ciliated columnar epithelium with small cartilaginous plates supporting the wall

Question 32

Secondary bronchus:

Answer 32

-arise form primary bronchus
-lined by simple columnar ciliated or pseudostratifed columnar ciliated epithelium with intraepithelial glands

Question 33

Parabronchus: (tertiary bronchus)

Answer 33

-arise from secondary bronchus
-both ends of it open into 2 different secondary bronchi
-lined by simple cuboidal epithelium

Question 34

Atria:

Answer 34

-small air spaces that open into parabronchi
-simple squamous to simple cuboidal epithelium

Question 35

Air capillaries:

Answer 35

-open-ended tubes
-both ends are open to an atrium
-simple squamous epithelium
-numerous blood capillaries surround air capillaries where gaseous exchange takes place

Question 36

Air sacs: ‘names’

Answer 36

-unpaired cervical
-paired clavicular
-thoracic
-abdominal

Question 37

Air sacs: function

Answer 37

*communicate with lungs through bronchi
-do NOT participate in gas exchange
-simple squamous to cuboidal epithelium