B2 Ventilation And Gas Exchange In The Lungs

Question 1

Explain the diffusion of gases into and out of the alveoli

Answer 1

-The deoxygenated blood from the Pulmonary artery has a low concentration of oxygen and a high concentration of carbon dioxide compared with the air inside the
alveoli.

-As the blood reaches the capillaries surrounding the alveoli, the oxygen diffuses into the blood across the squamous epithelial membrane and endothelial wall of the capillary, moving from higher O2 concentration to lower 02 concentration.

-At the same time carbon dioxide moves from the blood into the alveoli as the concentration of CO2 in the blood from the pulmonary artery is greater than that in the inhaled air in the alveoli.

-The blood is then circulated away from the alveoli by contractions of the heart, that move the newly oxygenated blood away from the lungs back to the heart to be pumped around the body.
- Co2 is removed by exhaling.

Question 2

What is a surfactant?

Answer 2

A chemical produced by the lungs to stop the alveoli from collapsing by reducing the surface tension of water

Question 3

Describe how the structure of the alveoli is adapted to its function

Answer 3

• Large surface area- there are millions of alveoli, providing more space for gas molecules to pass through.
• short diffusion pathway- the walls of the alveoli are made of squamous epithelial cells (one cell thick). This reduces the distance these molecules need to diffuse through.
• capillary network- each alveolus is close to a capillary which has a wall that is one cell thick to give short diffusion pathway.
• Diffusion gradients- oxygen diffuses form high conc inside alveoli down a conc gradient to area of low conc in the blood capillary maintained by ventilation.
• moisture layer in alveoli- gases only move across the membrane of dissolved. Oxygen dissolved in order to diffuse through blood in capillaries.

Question 4

What are alveoli’s?

Answer 4

They are small sacs at the end of the bronchioles. They ensure effective and efficient gas exchange.

Question 5

Inspiration/ inhalation

Answer 5

• external intercostal muscles contract pulling rib cage up and down
• diaphragm contracts and flattens
• thoracic cavity vol increases
• pressure in lungs reduces, lower than atmospheric pressure
• air moves into lungs down a pressure gradient from high atmospheric air pressure to lower air pressure of the thoracic cavity.

Question 6

Expiration/ exhalation

Answer 6

• external intercostal muscles relax so rib cage moves down and in
• internal intercostal muscles contract to pull ribs down and in
• diaphragm relaxes and moves up
• thoracic volume decreases
• pressure in lungs higher than atmospheric pressure
• air moves out of the lungs down a pressure gradient.

Question 7

Trachea

Answer 7

-Tube like structure that carries air from mouth to lungs.
-Contains cartilage.
- have thick walls lined with several layers of tissue including smooth muscle.
- lined with epithelium tissue consisting of ciliated epithelium cells and goblet cells.

Question 8

Bronchus

Answer 8

-The trachea splits into 2 bronchi as it enters the lungs which allows air to travel to the left and right lung.
- contains cartilage
- thick walls lined with several layers of tissue including smooth muscle
- lined with epithelium tissue consisting of ciliated cells and goblet cells.

Question 9

Bronchioles

Answer 9

• bronchi divides into smaller branches (bronchioles)
• lined with ciliated epithelial cells
• walls contain smooth muscles
• these then supply the alveoli with air.

Question 10

Intercostal muscles

Answer 10

External intercostal muscles- are responsible for forced and quiet inhalation. They raise the ribs and expand the chest cavity.

Internal intercostal muscles- are responsible for forced exhalation

Question 11

Diaphragm

Answer 11

Dome shaped muscular Patti on that separates the thorax from the abdomen.
- plays a major role in breathing as it’s contraction increases the vol of the thorax and so inflated the lungs

Question 12

Pleural membrane

Answer 12

• a serous membrane with one side lining the body cavity wall and the other lining the lungs.
• the membrane secretes serous fluid that reduces friction and enables the membranes to slide over each other
• this prevents the lungs sticking to the body cavity wall.

Question 13

How to calculate respiratory minute volume (pulmonary rate)

Answer 13

Respiratory mum vol (dm3min-1) = ventilation/ breathing rate (min-1) x tidal volume (dm3)

Question 14

Explain why a person with emphysema produces less atp than a healthy person

Answer 14

• decreased surface area of alveoli
• so less diffusion of oxygen into the blood
• not enough oxygen for increased respiration

Question 15

Explain why soda like is used in the spirometer

Answer 15

• to absorb co2 that is breathed out
• co2 is toxic and can alter breathing rate

Question 16

Ciliated epithelium

Answer 16

• waft mucus up out of the airways
• mucus is secreted by the goblet cells