Structure And Function Of Airways

Question 1

What kind of branching does the lung have

Answer 1

Dichotomous
Every tube splits into two

Question 2

What area trachea held open by

Answer 2

C shaped cartilage rings

Question 3

What property does cartilage provide the airway with

Answer 3

Mechanical stability

Question 4

Why does the back of the trachea not have cartilage

Answer 4

To allow oesophagus to run down the back to swallow food

Question 5

What is the name of the point at which the bronchi enter the lungs at?

Answer 5

Hilium

Question 6

Type I cells alveolus

Answer 6

Facilitate gas exchange
Very thin delicate barrier

Question 7

Type II cell alveolus

Answer 7

• Replicate to replace type I cells
• Secrete surfactant (reduces surface tension) and antiproteases
• Xenobiotic metabolism (breakdown of drugs and noxious chemicals that enter alveoli)

Question 8

Explain the distribution of type I and type II alveolar cells in the alveolar region

Answer 8

Type I - Cover ~95% of alveolar surface; lesser in number than type II, but are much larger.

Type II - Greater numbers than type I, but only cover ~5% of surface.

Question 9

What do macrophages and fibroblasts do

Answer 9

Clean debris and viruses
Produce ECM matrix holding the whole thing together

Question 10

What part of the alveolar region is where gas exchange takes place?

Answer 10

Alveolar sac

Question 11

• What is the main function of the respiratory airways?

Answer 11

To conduct O2 to alveoli and CO2 out of the lung (gas exchange)

This is facilitated by cartilage which gives mechanical stability, control of calibre (smooth muscle) and protection + cleaning mechanisms

Question 12

Pharynx function

Answer 12

Common passageway for food liquid and air

Question 13

What is the function of conchae

Answer 13

Highly vascular contribute to warming and humidification of intra nasally inhaled air

Question 14

What do nasal hairs do?

Answer 14

Filter out large particles

Question 15

What do the conchae, meatuses and paranasal sinuses produce?

Answer 15

Mucous traps debris

Question 16

Describe the structure of the airway wall

Answer 16

Submucosal gland partially embedded within the contractile smooth muscle ring; goblet cells within the epithelium contribute to the production of mucous, lies superficially above the ciliated epithelial layer

Mucociliary transport to release the pollutants

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Question 17

What assists in the removal of mucous and debris from the nasal cavity?

Answer 17

Cilia

Question 18

Lining cells

Answer 18

• Ciliated
• Intermediate
• brush
• basal

Question 19

Contractile cells

Answer 19

Smooth muscle

Question 20

Secretory cells

Answer 20

• Goblet (epithelium)
• Mucous
• ## Serous (glands)

Question 21

Connective tissue

Answer 21

Fibroblasts
Interstitial cell

Question 22

Neuroendocrine cells

Answer 22

• Nerves
• Ganglia
• Neuroendocrine cells
• Neuroepithelial bodies

Question 23

Vascular cells

Answer 23

• Endothelial
• Pericyte
• Plasma cell
• Smooth muscle

Question 24

Immune cells

Answer 24

• Mast cell
• Dendritic cell
• Lymphocyte
• Eosinophil
• Macrophage
• Neutrophil

Question 25

What do mucin granules contain and how is it hydrated

Answer 25

Mucin granules contain mucin in goblet cells; highly condensed forms of mucin requires hydration, this is hydrated through water absorption in trachea ( Airway liquid comes into granule→ Expansion of mucin generates expansive mucous

Question 26

Why do the epithelial cells have so many mitochondria?

Answer 26

Cillia need energy to move and waft mucous along surface

Question 27

Acini

Answer 27

Mucous producing units

Question 28

What do serous acini secrete?

Answer 28

Anti-bacterial enzymes e.g. lysozyme Water and salts like Na+ and Cl-

Question 29

What is the arrangement of ciliary structures?

Answer 29

9+2 microtubule arrangement

Question 30

What is the rhythm of ciliary beating?

Answer 30

Metachronal- different lines of ciliary hair move at different times to waft mucous down to back of throat

Question 31

List all the airway epithelium functions

Answer 31

1. Secretion of **mucin, water and electrolytes** (Components of mucous + plasma, mediators) 2. Movement of mucus ****by cilia - **Mucociliary clearance** 3. **Physical barrier** against inhaled insult 4. Production of regulatory and **inflammatory mediators**:

Question 32

List the inflammatory mediators

Answer 32

**Nitric oxide secreted by nitric oxide synthase (NOS)** which could control cilia beating **Carbon Monoxide by haem oxygenase (HO)**; enzyme catalyses the degradation of haem to produce biliverdin, Fe2+ (ferrous iron) and CO. Products activate vasodilatory pathways **Arachidonic acid metabolites** (COX, **prostaglandins**) **Chemokine** (IL-8) **Cytokines** (GM-CSF) **Proteases**

Question 33

- What does brown-staining on a histological section in the human airway show?

Answer 33

**Anti-NOS antibody** results in **brown staining to identify NOS** **Significant presence of NO** exhibits a regulatory function on ciliary beat - high presence within the epithelium

Question 34

What does contraction of this smooth muscle lead to?

Answer 34

Contraction of smooth muscle **stimulates** **secretion into epithelial lining** Also closes airway to prevent something going down airways

Question 35

What are the (3) functions of airway smooth muscle cells?

Answer 35

- Structure of airway- contribute to it - Tone (airway caliber) and contract + relax - Secretion of mediators, cytokines, chemokines- normally it is a little Under inflammation - Structure- contribute more towards structure via hypertrophy and proliferation e.g. in asthma - Still contribute to tone - Secrete a lot more mediators, cytokines, chemokines - Produce prostaglandins, adhesion + NO molecules

Question 36

What is the name of the airway vasculature?

Answer 36

Tracheo-bronchial systemic circulation

Question 37

How does blood return from tracheal circulation?

Answer 37

Systemic veins

Question 38

How does blood return from bronchial circulation to both sides of the heart?

Answer 38

Bronchial and pulmonary veins

Question 39

List all the functions of tracheo-bronchial circulation (4)

Answer 39

- Direct gaseous exchange between systemic circulation in the tissue of sub-epithelial micro-vasculature. Highly vascular system facilitates direct **gas exchange** between tissues and blood - Direct **good gas exchange** (directly between airway tissues and blood) - Contributes to **warming** and **humidification** of inspired air - **Clearance** of **inhaled drugs** (Benefit is dependent on the mechanism of delivery of drug) - Supplies airway tissue and lumen with **inflammatory cells**; in addition to proteinaceous plasma (mechanism of plasma exudation)

Question 40

Nerves- what different types of nerves control airway function

Answer 40

- Parasympathetic- cholinergic - Nitrous oxide sympathetic adrenergic pathway - Sensory nerves

Question 41

Outline the parasympathetic 'motor' pathway for airway control

Answer 41

Innervation via vagus nerve through corticospinal tract, motor pathway Secretion of ACh NT via cholinergic synapse of postganglionic fibre and gland This stimulates the **bronchostriction** and contraction of smooth muscles within trachea + stimulates submucosal glands to **secrete mucous**

Question 42

Outline the “sympathetic” and nitric oxide (NO) pathway for airway control

Answer 42

Sympathetic - **Adrenergic** reflex causes **bronchodilation**, smooth muscle relaxes, dilating the airways Adrenaline is secreted by adrenal gland, and directly relaxes the airways Nitric Oxide - NO is a NT of neuronal pathway that **dilates** and opens airways Adrenaline and the neuronal pathway producing nitric work to relax the airways **We DON'T have sympathetic nervous relaxant pathway which release NA- we have NO secreting nerves instead which causes airway smooth muscle to relax**

Question 43

Name 3 respiratory diseases associated with loss of airway control

Answer 43

Asthma, COPD and cystic fibrosis - all common conditions (These diseases are associated with abnormalities of airway inflammation and obstruction)