Ventilation And Gas Exchange In The Lungs

Question 1

describe the lungs

Answer 1

a pair of lobed structures made up of a series of highly branched tubules (bronchioles) which end in tiny air sacs (alveoli)

Question 2

describe the trachea

Answer 2

airway supported by rings of cartilage, tracheal walls are made of muscle, lined with ciliated epithelial cells and goblet cells

Question 3

describe bronchi

Answer 3

similar structure to trachea, also supported by cartilage to some extent, lined with ciliated epithelial cells and goblet cells

Question 4

describe bronchioles

Answer 4

walls are made of muscle (allows contraction and constriction, therefore controlling airflow) lined with epitheliated cells

Question 5

describe alveoli

Answer 5

air sacs at the end of the bronchioles, lined with squamous epithelial cells. between alveoli are collagen and elastic fibres .
elastic fibres allow alveoli to expand to fill with air high in O2 and spring back to expend CO2 laden air

Question 6

describe ventilation

Answer 6

air is brought in and out of the lungs due to changes in volume, and therefore pressure.
the changes in volume and pressure are controlled by three muscles
- diaphragm
- internal intercostal muscles
- external intercostal muscles

Question 7

what are inspiration and expiration?

Answer 7

inspiration = inhale
expiration = exhale

Question 8

when does inspiration occur?

Answer 8

when pressure in the lungs decreases below atmospheric pressure, air is forced into the lungs

Question 9

when does expiration occur?

Answer 9

when pressure in the lungs increases above atmospheric pressure, air is forced out of the lungs

Question 10

describe the muscle actions involved in inspiration?

Answer 10

• both external intercostal muscles and diaphragm (lowers and flattens) contract
• internal intercostal muscles relax
• the ribs are pulled outwards and upwards
• volume of thorax increases whilst pressure decreases
• air is drawn into the lungs down the pressure gradient

Question 11

describe the muscle actions involved in expiration?

Answer 11

• both external intercostal muscles and diaphragm relax
• internal intercostal muscles contract
• the ribs are pulled inwards and downwards
• volume of thorax decreases whilst pressure increases
• air is forced out of lungs

Question 12

how do you calculate pulmonary ventilation rate?

Answer 12

pulmonary ventilation rate
= tidal volume (dm^3) x breathing rate (min^-1)

Question 13

how do the alveoli provide good gas exchange surface?

Answer 13

• many small alveoli, provides a large surface area
• alveoli wall is thin (one cell thick)
• ventilation and circulation maintain the concentration gradient for carbon dioxide and oxygen
• each pulmonary artery is very narrow so red blood cells are flattened against the wall meaning short diffusion distance and more time for diffusion