Lecture 16 - anatomy of the respiratory tract

Question 1

What does the respiratory tract do?

Answer 1

Regulates pH, CO₂ and O₂ levels, produces sound, defends the body from pathogens, and does olfaction

Question 2

Upper respiratory tract: what is it composed of and what are its functions?

Answer 2

Nose
Pharynx
Paranasal sinuses
Larynx

Warming, moistening, and filtering the air
Olfaction
Resonating sound

Question 3

Lower respiratory tract: what is it composed of and what are its functions?

Answer 3

Trachea
Bronchi
Bronchioles
Alveoli

Gas exchange
Surfactant production

Question 4

The nose: what does it do and what are its adaptations

Answer 4

Moistens, warms, and filters the air
Olfactory cells for olfaction
Modifies speech sound

• Vibrissae - Hair inside the nose to filter air
• Conchae - Shelf-like projections from the lateral wall which produce turbulence, allowing more time for the air to be warmed and moistened
• Pseudostratified ciliated columnar epithelium
  with goblet cells which produce mucous to trap particles while the cilia waft the trapped particles to the pharynx where they can be swallowed.

Question 5

Pharynx: what is it and what is it composed of?

Answer 5

Acts as a communal pathway for both respiratory and gastrointestinal systems

Nasopharynx - posterior to the nose
Oropharynx – posterior to the mouth
Laryngopharynx – posterior to the larynx

Question 6

Larynx: what does it do and what is it composed of?

Answer 6

Maintains an open airway
Prevents food and drink from entering the lungs
Sound production

Epiglottis - blocking food from entering the lungs
Hyoid bone - Holds tongue, larynx and helps transmit forces to the jaw
Thyroid cartilage - Supports and protects the vocal cords and forms the voice’s sound
Cricoid cartilage - Provides an attachment point for muscles, ligaments, and cartilage, which function in the opening and closing of the vocal cords
Arytenoid cartilage - production of vocal sound

Question 7

Trachea: what is it, what is its structure, and what is it attached to?

Answer 7

A tough flexible tube that extends from the larynx to the carina and lies anterior to the oesophagus

Lined with pseudostratified ciliated columnar epithelium and contains 15-20 horseshoe-shaped cartilage muscles for support of the trachea

Attached to trachealis muscle at the posterior ends of the trachea which constricts during coughing

Question 8

Bronchi

Answer 8

Series of tubes that got smaller in diameter due to decreased height of epithelial cells, amount of smooth muscle, and amount of cartilage

Composed of primary, secondary, and tertiary bronchi

Question 9

Primary bronchi

Answer 9

Around 2-3cm long, the right is wider than the left, contains C-shaped cartilage

Supply the lungs with gas

Question 10

Secondary bronchi

Answer 10

Contains small plates of cartilage as support

Supply lobes with gas (3 on the right, 2 on the left)

Question 11

Tertiary bronchi

Answer 11

Contains small plates of cartilage as support

Supply segments with gas (10 on the right, 8 on the left)

Question 12

Bronchioles

Answer 12

Contain no cartilage, composed of smooth muscle layers so they can constrict or dilate

Branches out into 50-80 terminal bronchioles

Question 13

Terminary bronchioles

Answer 13

Composed of simple columnar epithelium with cilia (no goblet cells or mucous glands) and Clara cells so they can produce surfactant

Each gives rise to 2 or more respiratory bronchioles

Question 14

Respiratory bronchioles

Answer 14

Simple cuboidal epithelia (no cilia) and Clara cells so they can produce surfactant

Alveoli extend from the lumen, gas exchange occurs here

Question 15

Alveoli: how many are in each lung, what does it do, and what are the specific sections of the respiratory bronchiole before the alveoli?

Answer 15

150-250 million per lung

The site of gas exchange between the nearby capillary bed and the gas in the alveoli

Respiratory bronchiole - alveolar duct - sac - alveoli

Question 16

Alveolar ducts

Answer 16

Elongated airways with walls made of alveoli (sacs)

Question 17

Alveolar sacs

Answer 17

Spaces surrounded by clusters of alveoli

Question 18

Structure of an alveolus

Answer 18

Type I alveolar cells that make up the thin simple squamous epithelium of the alveoli

Type II alveolar cells that secrete surfactant which balances surface tension pressure so the lungs don’t collapse

Macrophages which phagocytise inhaled pathoges

Question 19

Respiratory membrane

Answer 19

Type I cell epithelium on top of the type I cell basement membrane and the capillary basement membrane underneath the capillary epithelium

Since the basement membranes are usually fused, the membrane usually looks like l|l

Question 20

The two portions of the respiratory tract

Answer 20

The conductive portion involves filtering, warming, and moistening the air and transferring it into the lungs

The respiratory portion involves gas exchange

Both portions are involved in pathogen defence

Question 21

Parts of the conductive portion of the respiratory tract

Answer 21

Nasal cavity - paranasal sinuses - pharynx - larynx - trachea - primary bronchi - secondary bronchi - tertiary bronchi - bronchioles - terminal bronchioles

Question 22

Parts of the respiratory portion of the respiratory tract

Answer 22

Respiratory bronchioles - alveolar ducts - alveolar sacs - alveoli