The lungs and disease

Question 1

Which muscles involved in ventilation?

Answer 1

• Intercostal muscles between ribs, responsible for movement • External – contracts – ribs move up and out - inspiration • Internal – contract – ribs move down and in - expiration • Diaphragm – muscular sheet which separates thorax from abdomen

Question 2

Tell me about the trachea…

Answer 2

It has: • Rings of cartilage prevent tube collapsing when internal pressure drops. • Lined with ciliated epithelium.

Question 3

What happens at the end of the trachea?

Answer 3

• Trachea divides into 2 bronchi. • These tubes enter each lung, supported by cartilage

Question 4

Tell me about the alveoli (5)

Answer 4

• Spherical thin sacs, one cell thick • Major site of gas exchange, moist, lined with surfactant • 100μm in diameter, surrounded by capillaries • Lined with flattened epithelial cells (approx 300 million) • Makes a vast area for exchange (40-60m2)

Question 5

In ventilation, if the volume increases, what happens to the pressure and the air?

Answer 5

It decreases and air is forced in

Question 6

What sort of epithelium do we find in the alveoli?

Answer 6

the epithelium is flattened (squamous)

Question 7

Explain how inspiration occurs. (5)

Answer 7

Diaphragm contracts/moves down/ flattens; External intercostal muscles contract rib cage upwards and out Increases volume (of thorax); Decrease in pressure; Air moves from high to lower pressure in lungs

Question 8

A thin surface and a diffusion gradient are both features of gas exchange surfaces. Describe how these are achieved at the gas exchange surfaces of a mammal.

Answer 8

Wall of alveoli / capillaries have single epithelial layer/ Alveoli and capillaries are close together; the epithelium is flattened (squamous) Ventilation maintains high O2/low CO2 concentration(in alveoli); blood flow/circulation maintains high CO2 / low O2 concentration(in blood);

Question 9

Describe and explain the difference in the composition of gases in inhaled and exhaled air. (6)

Answer 9

1 inhaled air contains more oxygen than exhaled air; 2 inhaled air contains less carbon dioxide than exhaled air; 3 inhaled air contains less water (vapour); 4 relative amount/percentage of nitrogen also changes; 5 respiration results in lower blood O2 / higher blood CO2; 6 oxygen enters blood / carbon dioxide leaves blood in alveoli; 7 by diffusion; 8 water vapour diffuses from moist surface;

Question 10

How do we calculate pulmonary ventilation?

Answer 10

Pulmonary ventilation = ventilation rate x tidal volume

Question 11

How can the ventilation rate can be calculated from the pressure graph?

Answer 11

by measuring the time taken for one ventilation cycle and using the formula: Ventilation rate (breaths/minute) = 60 ÷ time for 1 cycle

Question 12

What is tidal volume?

Answer 12

The tidal volume is the normal volume of air breathed in each breath (also called the breathing depth).

Question 13

What is asthma caused by?

Answer 13

Asthma is caused by physical factors called allergens in the environment. These allergens include pollen, dust mites, faeces and fur. These allergens trigger an inflammatory response by the immune system

Question 14

How do mast cells help to narrow the bronchioles in asthmatics?

Answer 14

Mast cells release histamines, which cause the smooth circular muscles of the bronchioles to contract, narrowing the airways (bronchoconstriction).

Question 15

What are the symptoms of asthma?

Answer 15

Difficulty breathing due to constriction of airways and mucus build up. Wheezing due to narrow pathway and sir flowing through it Tight feeling in the chest due to constriction of smooth muscle Heavy coughing to remove obstructions

Question 16

Describe the transmission and course of infection of pulmonary tuberculosis. (6)

Answer 16

1 (Bacteria transmitted in) droplets / aerosol; 2 (Bacteria) engulfed / ingested by phagocytes / macrophages; 3 (Bacteria) encased in named structure e.g. wall / tubercle / granuloma / nodule; 4 (Bacteria) are dormant / not active / not replicating; 5 If immunosuppressed, bacteria activate / replicate / released; 6 Bacteria destroy alveoli / capillary / epithelial cells; 7 (Leads to) fibrosis / scar tissue / cavities /calcification; 8 (Damage) leads to less diffusion /less surface area / increases diffusion distance; 9 (Activation / damage allows bacteria) to enter blood / spreads (to other organs);

Question 17

People with emphysema may feel weak and tired. Explain why.

Answer 17

Alveoli break down: Less surface area for gas exchange Walls thicken (scar tissue): increases diffusion distance Loss of elastin (elastic tissue) due to elastase from white blood cells involved: Alveoli cannot recoil so it is more difficult to expel air Reduced diffusion gradient Less oxygen enters blood and then tissues; Less respiration / less energy released / less ATP produced;

Question 18

Describe Pulmonary fibrosis (5)

Answer 18

Scars form on the epithelia that are damaged, increasing the diffusion pathway, loss of elasticity in lung tissue, which reduces the concentration gradient, narrowing of vessels, reducing air flow and concentration gradient. Results in shortness of breath, dry cough, tiredness (insufficient oxygen for respiration)