Lecture 7 - Lower Airways in MAMMALS

Question 1

describe the position of the trachea

Answer 1

ventrally located in the neck

Question 2

what and where does the trachea bifurcate into?

Answer 2

two principal bronchi (left and right) at level of the 4-5th thoracic vertebrae

Question 3

how is the trachea supported in mammals

Answer 3

by incomplete dorsal cartilage rings

hyaline cartilage

Question 4

what smooth muscle forms the roof of the trachea?

Answer 4

trachealis muscle

Question 5

What is the function of annular ligaments?

Answer 5

connective tissue joining adjacent cartilaginous rings

Question 6

what is the carina?

Answer 6

cartilaginous ridge at the tracheal bifurcation

Question 7

what sensory innervation/receptors is there to the trachea?

Answer 7

mechanoreceptors sense foreign material or mucus to initiate the coughing reflex

Question 8

what is the cartilaginous structure of the bronchi (principle, lobar, segmental)

Answer 8

interlocking cartilaginous plates

Question 9

what is the bronphopulmonary segment?

Answer 9

a segmental bronchus (3 - parabronchi) and the lung tissue which it ventilates

Question 10

what is the pulmonary acinus and what do they contain?

Answer 10

a respiratory bronchial and the lung tissue which it ventilates
contain many alveoli = units of gas exchange

Question 11

what direction does air flow in mammals?

Answer 11

bi-directional movement of air = inefficient

Question 12

do stale and fresh air mix with bidirectional flow?

Answer 12

yes
at end of expiration stale air in airways and alveoli
on inspiration, fresh air mixes with stale air

Question 13

what embryonic structure does the lower airways develop from?

Answer 13

as an outgrowth from embryonic foregut

Question 14

describe the formation of the laryngotracheal groove and the embryonic development through to lung buds

Answer 14

• larygnotracheal groove forms in endoderm of floor of what will be the oesophagus
• lips of groove fold and fuse = respiratory diverticulum,, occurs on day 17 of gestation in sheep
• resp diverticulum gives rise to epithelium of tracheal mucosa, surrounding mesoderm forms cartilaginous rings of trachea
• resp diverticulum continue to grow caudally into thoracic cavity forming lung buds
• lung buds –> caudal growth –> L & R principle bronchi

Question 15

what is the congenital defect trachea-oesophageal fistula?

Answer 15

failure of separation of laryngotracheal groove from oesophagus –> food enter resp tract

Question 16

what is the congenital defect tracheal hypoplasia

Answer 16

abnormal narrowing of trachea due to defect in growth of cartilage

Question 17

what is the congenital defect of accessory lungs

Answer 17

results from an extra lung bud

may develop in unusual site ie/ neck or abdomen