Anatomy of Lower Respiratory Tract

Question 1

Trachea

Answer 1

• 10-12 cm long, 2 cm in diameter
• reinforced by C-shaped cartilage rings (solid part that keeps tracheal wall open)
• trachealis muscle completes the supportive ring (smooth muscle)
• lined with ciliates mucosa that pushes mucus towards the larynx

Question 2

Bronchial tree

Answer 2

All passages of the conducting zone:
- primary bronchi
- secondary bronchi
- tertiary bronchi
- bronchioles 
- terminal bronchioles
(R primary bronchi is shorter, wider, straighter, more likely to be obstructed)
-each bronchus enters the lung at the hilium

Question 3

Epithelium histology of bronchial tree

Answer 3

-walls always contain elastic fibers
-increased amount of smooth muscle
-goes from pseudostratified columnar to simple columnar to simple cuboidal
(Few mucus producing cells/cilia in bronchioles)

Question 4

Alveoli

Answer 4

• blind (discontinuous), pouch-like structure whose walls are richly supplied with capillaries
• alveolar pores connect with neighbouring alveoli
• type 1, type 2, alveolar macrophages

Question 5

Type 1 alveolar cells

Answer 5

• majority
• makes up the walls of the alveolus
• thin simple squamous epithelium

Question 6

Type 2 alveolar cells

Answer 6

• secretes surfactant (soap like substance to reduce surface tension, not produced by fetus until 28-30 weeks)
• secretes antimicrobial proteins
• cuboidal epithelial cells (prevents cells from collapsing, and easier to inflate)

Question 7

Respiratory distress syndrome

Answer 7

-premature infants have trouble breathing

Question 8

Alveolar macrophages

Answer 8

• immune cells, “dust cells”

- digest any debris and bacteria that have gotten past the cilia and mucus

Question 9

Respiratory membrane

Answer 9

• air-blood barrier
• formed from walls of capillaries and alveoli, and their fused basement membrane
• alveolar walls surface area is 40x greater than the entire skin
• thin enough to allow diffusion to happen easily (0.0005 mm thick)

Question 10

Lungs

Answer 10

• cone-like structure containing elements of the Bronx hill tree and respiratory zone
• large size, 2.5 lbs
• mostly elastic connective Tissue
• divided lives by fissures (R:3, L:2 bronchopulmonary segments)

Question 11

Pleurisy

Answer 11

• decreased serous fluid: friction and pain

- increased serous fluid: compressed lungs