Resp Lecture 6

Front 1

What are the components of the lower airways?

Back 1

Trachea-->principle bronchus-->lobar bronchus (secondary)--> segmental bronchus (tertiary)--> small bronchus-->bronchiole-->terminal bronchiole (no further branching)--> respiratory bronchiole (these contain some alveolus-the units of gas exchange)-->alvelolar duct (walls are only alvelous)--> blind ended alveolar sac

Front 2

What is the trachea?

Back 2

Flexible, semi-rigid tube
Ventrally located in the neck

Continues into thorax through thoracic inlet where it bifurcates into two principle bronchi at the level of the 4/5th thoracic vertebrae.
Supported by hyaline cartilage rings (incomplete dorsally in mammals, complete in birds). Annular ligaments connect the ajoining rings.

Front 3

Trachealis muslce

Back 3

forms the roof of the trachea

Front 4

Carina

Back 4

is the cartilaginous ridge at the tracheal

Front 5

What is the sensory innervation of the trachea?

Back 5

mechanoreceptors sense foreign material or mucus to initiate coughing reflex.

Front 6

What are the bronchi?

Back 6

Similar in structure to trachea, but with cartilaginous plates instead of rings; a little more narrow. One principle bronchus enters each lung. Each principle bronchus branches and te tubing continues to get smaller and smaller

Front 7

What is the bronchopulmonary segment?

Back 7

A segmental bronchus and the lung tissue which it ventilate. All of the structures that receive air from a segmental bronchus

Front 8

Pulmonary acinus?

Back 8

A respiratory bronchiole and the lung tissue which is ventilates (a respiratory bronchiole and anything that receives air from the bronchiole). Contains many alveoli, arranged in walls of respiratory bronchioles, alveolar ducts, and alveolar sacs.

Front 9

How is ventilation in mammals described?

Back 9

It is considered bidirectional. At the end of expiration, stale air remains in the airways and alveoli. On inspiration, fresh air mixes with the stale air, pushing the stale air into the alveoli before any of the fresh air can get in. Once the fresh air does get in, mixes with the stale air.

Front 10

How do the lower airways develop?

Back 10

Develop as an outgrowth from embryonic foregut (the point where the pharynx ends, there's a groove that forms, the laryngotracheal groove).
The laryngotracheal groove forms in endoderm of floor of prospective oesophagus. The lips of the groove fold in and fuse creating a tube (respiratory diverticulum). This occurs as early as D 17 in sheep. Grows ventrally and caudally into splenic mesoderm maintaining crainial connection to foregut at pharynx

Front 11

What is the respiratory diverticulum?

Back 11

Gives rise to epithelium of tracheal mucosa and surrounding mesoderm forms connective tissue and cartilage rings of trachea.
It continues to grow caudally into the thoracic cavity and branches to form 2 lung buds. The lung buds continue caudal growth giving rise to the principle bronchi. Continued branching of bronchi to form smaller bronchioles.

Front 12

What are some of the congenital defects in airway development?

Back 12

Tracheo-oesophageal fistulas

Tracheal hypoplasia

Accessory lungs

Front 13

Tracheo-oesophageal fistulas

Back 13

Failure of separation of caudal laryngotracheal groove from foregut, food is able to enter the respiratory tract

Front 14

Tracheal hypoplasia

Back 14

abnormal narrowing of the respiratory tract due to defect in growth cartilages

Front 15

Accessory lungs

Back 15

Result from extra lung bud, may develop in unusual site

Front 16

What are the components of the lower airways in the bird?

Back 16

Trachea
Syrinx
Bronchi
Air sacs
lungs

Front 17

Describe the trachea in the bird

Back 17

Supported by complete overlapping cartilaginous rings, palpable on RT side of neck.
Bifurcates to base of heart

Front 18

What is the syrinx?

Back 18

Vocal organ of the bird. Located at bifurcation of trachea (partly in trachea, partly in bronchi. Tracheal part: strong cartilages

Front 19

Describe the bronchi openings in the bird

Back 19

Bronchial openings are separated by vertical wedge-shaped cartilages (pessulus) otherwise no cartilage in walls. Lateral and medial walls contain typanic membranes (produce sound by vibration)

Front 20

Describe the bronchi in the bird

Back 20

Two principle bronchi: run along ventral aspect of lungs where secondary bronchi arise. Secondary bronchi are connected to each other via tertiary bronchi (Parabronchi). Air capillaries are located in the walls of the parabronchi, this is where gas exchange occurs

Front 21

Secondary bronchi

Back 21

Secondary bronchi enter the lungs at regular intervals (they also enter into the air sacs)About 40-50 secondary bronchi (connected to each other in the lung via tertiary bronchi-parabronchi)

Front 22

What are parabronchi

Back 22

About 400-500 arise from each secondary bronchus. 1-2mm in diameter. Anatomose with each other. Loops between secondary bronchi

Front 23

What are the air capillaries

Back 23

Located in the walls of the parabronchi.
Forms loops from walls of parabronchi through lung tissue back to parabronchi, where gas exchange occurs.

Front 24

What are the air sacs?

Back 24

Fill up with air upon inspiration and empty the air out on expiration. They push the air through the lungs NOT the site of gas exchange. Expansion of respiratory tract for air intake occurs here because lungs are rigid, act as bellows.
Large thin walled sacs connected to secondary bronchi to lungs and principle bronchi.
Lay between organs (thoracic and abdominal); no diaphragm. Abdominal muscles compress the air sacs and push the air through.
Lighten body by extending into medullary cavities of pneumatic bones. Allows for maximal respiratory while minimizing weight.
Sit in cranial and caudal groups. Allow for unidirectional airflow

Front 25

Why are fractures serious in birds?

Back 25

Can result in subcutaneous emphysema (air comes out of the bones and into the tissues).

Front 26

What are the crainal sacs?

Back 26

Cervical
Clavicular
Cranial thoracic
Cervicocephalic
Receive stale air from lungs and expels through trachea

Front 27

Cervical air sacs

Back 27

Unpaired; within and adjacent to cervical and thoracic vertebrae

Front 28

Clavicular air sacs

Back 28

Unpaired; large fills thoracic inlet and extends into sternum and humeri

Front 29

Cranial thoracic air sacs

Back 29

Paired, between sternal ribs, heart and liver

Front 30

Cervicocephalic air sacs

Back 30

Only some species (strong fliers) extends over the head and along the neck; communicates with infraorbital sinus, direct communication with nasal cavity

Front 31

What are the caudal air sacs?

Back 31

Caudal thoracic
Abdominal
They supply fresh air to the lungs

Front 32

What are the caudal thoracic air sacs?

Back 32

Paired between the body wall and abdominal viscera

Front 33

What are the abdominal air sacs?

Back 33

Paired; caudodorsal abdominal cavity, extending into adjacent vertebral and pelvic bones.

Front 34

Describe the ventilation that occurs in birds

Back 34

On inspiration, fresh air flows into the lungs and the caudal air sacs, and stale air moves from lungs into cranial air sacs
On expiration air sacs are compressed (NOT lungs). Fresh air from caudal air sacs moves into lungs and stale air expelled from cranial air sacs via trachea.
O2 rich air enters the lungs on BOTH inspiration and expiration. This helps meet the high needs for O2 during flight.
The system has no valves, but unidirectional flow probably maintained due to anatomical orientation of secondary bronchial openings of cranial group of air sacs.