Module 21 respiratory system (ventilation)

Question 1

What are the four main functions of the respiratory system?

Answer 1

1. Regulate pH levels
2. Bring in oxygen and get rid of carbon dioxide
3. Vocalization
4. Protect from inhaled pathogens

Question 2

What is the pathway of air into the body?

Answer 2

1. Nasal/oral cavity
2. Pharynx
3. Larynx
4. Trachea
5. Primary bronchi
6. Bronchioles
7. Alveolar ducts
8. Alveoli

Question 3

How can bronchioles change shape?

Answer 3

They are surrounded by smooth muscle.

Question 4

What are the defense mechanisms?

Answer 4

Cells can secrete mucous and other cells have cilia like projections that sweep the mucous up into the pharynx where it can be swallowed.

Question 5

Type I alveolar cells

Answer 5

An alveolar sac is made up of a thin layer of Type I alveolar cells. These cells are thin and flat which minimizes the amount of distance gas has to travel during simple diffusion.

Question 6

Type II alveolar cells

Answer 6

These are cells that secrete surfectant

Question 7

Where is the capillary located in the alveolar cells?

Answer 7

It’s located very close to the Type I alveolar cells.

Question 8

What controls breathing? What controls the contractions of the diaphragm?

Answer 8

Motor neurons which use acetylcholine as the neurotransmitter.

Question 9

Bulk flow

Answer 9

Air moves from areas of high pressure to areas of low pressure.

Question 10

Intra-alveolar pressure (P alv)

Answer 10

The pressure within the alveoli

Question 11

What is the pressure in the atmosphere and the alveoli when we inhale?

Answer 11

P(atm) is greater than the P(alv)

Question 12

What is the pressure in the atmosphere and the alveoli when we exhale?

Answer 12

P(alv) is greater than in the P(atm)

Question 13

Why do the lungs increase volume?

Answer 13

Increase the volume (makes more room for gas particles)
The pressure must decrease below the atmospheric pressure. The lungs have lower pressure compared to the atmosphere.

Question 14

Why do the lungs decrease volume?

Answer 14

By decreasing the volume past the atmospheric pressure it forces air to exit the lungs. The lungs have higher pressure compare to the atmosphere.

Question 15

What controls lung volume?

Answer 15

Diaphragm and the intercostal muscles

Question 16

Lung compliance

Answer 16

Refers to the ability of the lungs to stretch. A higher lung compliance means its easier for the lungs to stretch out and easier to change lung volume and inhale.

Question 17

What is lung compliance affected by?

Answer 17

1. Elasticity of lung tissue (allows lungs to return back to original shape)
2. Surface tension inside alveoli

Question 18

Emphysema

Answer 18

This destroys the elastic fibers. While compliance may increase; the ruined elasticity prevents the lungs from returning to the original shape. This affects the ability to properly get the air out of the lungs.

Question 19

How does pulmonary fibrosis affect the lungs?

Answer 19

The formation of the scar tissue negatively impacts the lung compliance (ability to expand).

Question 20

How does surfactant reduce tension?

Answer 20

There is a thin layer of water lining the inside of the alveoli. The surface tension produced by this thin layer of water creates hydrogen bonds that resists the expansion of the lungs. Surfactant which is composed of proteins and lipids lowers this surface tension and allows for expansion making it easier to inhale.

Question 21

Relaxed diaphragm/releaxed intercostals

Answer 21

The diaphragm is in the upwards position. Upside down u-shape is very evident. This supports exhalation of the air because lung volume decreases and the air is pushed out.

Question 22

Contracted diaphragm/contracted intercostals

Answer 22

The diaphragm moves the lungs downwards and the intercostals move the lungs outwards to increase lung volume so air enters.

Question 23

Why is fluid build up in the lungs dangerous?

Answer 23

It increases diffusion distance for gas exchange.

Question 24

How does coronavirus impact the lungs?

Answer 24

The immune system response to covid-19 hurts gas exchange. Type I & II alveolar cells are destroyed
1. Alveolar collapse due to loss of Type II surfactant cells
2. Less oxygen enters the blood stream due to lack of Type I cells
3. More fluid enters the alveolus.

Question 25

The diaphragm contracts (controlled by motor neurons), causing it to flatten
Intercostal muscles contract (controlled by motor neurons), expanding the chest wall
Increased lung volume –> decreased Palv –> air flows in, increasing the pressure
When Palv = Patm then inhale stops

Answer 25

Inhalation

Question 26

During normal breathing, expiration is passive (does not require muscle contraction)
Diaphragm and rib muscles relax
Lungs are elastic, so they will naturally recoil to their smaller resting position
Decreased lung volume –> increased Palv –> air flows out

Answer 26

Exhilation