Unit 3- Gas exchange in humans

Question 1

Why do we need a gas exchange system?

Answer 1

-getting oxygen into the blood for respiration
-Get rid of carbon dioxide made from respiring cells

Question 2

What are the two types of intercostal muscles?

Answer 2

-Internal
-External

Question 3

What does ventilation consist of?

Answer 3

-Inspiration (breathing in)
-Expiration (breathing out)

Question 4

What is ventilation controlled by?

Answer 4

Movement of the diaphragm, i external and internal intercostal muscles and the ribcage

Question 5

Explain what happens during inspiration

Answer 5

-External intercostal muscles and diaphragm contract
-Ribcage moves upwards+ outwards
-Diaphragm flattens, increases volume of the thoracic cavity
-Lung pressure decreases to below atmospheric pressure
-air flows down the trachea and into the lungs

Question 6

Is inspiration an active process?

Answer 6

-Yes- it requires energy

Question 7

Explain what happens during the expiration

Answer 7

-External intercostal and diaphragm muscles relax
-Ribcage moves downwards+ inwards
-Diaphragm curves again
-Volume of thoracic cavity decreases
-Air pressure increases to above atmospheric level
-Air is forced won the pressure gradient and out of the lungs

Question 8

Is normal expiration active or passive?

Answer 8

Passive-Does not require energy

Question 9

What happens when the intercostal muscles are antagonistic?

Answer 9

-External relax
-Internal contract pulling the ribcage down and in

Question 10

Where does the gas exchange occur

Answer 10

The alveoli

Question 11

What are the alveoli surrounded by?

Answer 11

A network of capillaries

Question 12

What is the structure of an alveolus?

Answer 12

-Wall is made up of a single thin layer of flat cells called alveolar epithelium
-These walls contain a protein called elastin
-The wall of each capillary is made up of capillary endothelium

Question 13

What is the purpose of elastin in an alveolus wall?

Answer 13

-Helps the alveoli to recoil to their normal shape after inhaling and exhaling

Question 14

How does air (containing oxygen) reach the alveoli?

Answer 14

-Trachea
-Bronchi
-Bronchioles
-Alveoli
-Down a pressure gradient

Question 15

Why does carbon dioxide move down its own diffusion + pressure gradient?

Answer 15

-Moves in an opposite direction to O2 so it can be breathed out

Question 16

How does oxygen move across the gas exchange system?

Answer 16

-Trachea =pressure gradient
-Bronchi =pressure gradient
-Bronchioles =pressure gradient
-Alveoli =pressure gradient
-Alveolar epithelium =Diffussion gradient
-Capillary endothelium =Diffussion gradient
-Blood (into haemoglobin)=Diffussion gradient

Carbon dioxide moves in the opposite direction

Question 17

What features of the alveoli speed up the rate of diffusion?

Answer 17

-Thin exchange surface- Alveolar epithelium is only one cell thick, short diffusion pathway
-Large SA- millions of alveolili
-Steep concentration gradient of oxygen and carbon dioxide between alveoli and capillaries (maintained by flow of blood and ventilation

Question 18

Do lung diseases affect ventilation or gas exchange?

Answer 18

Both

Question 19

What is tidal volume?

Answer 19

The volume of air in each breath (usually between 0.4dm3 and 0.5dm3)

Question 20

Define ventilation rate.

Answer 20

The number of breaths per minute (about 15)

Question 21

What is the forced expiratory volume?

Answer 21

The maximum volume of air that can be breathed out in 1 second

Question 22

What is forced vital capacity?

Answer 22

The maximum volume of air possible to breathe out of the lungs after a deep breath in

Question 23

Tuberculosis is a disease caused by bacteria, immune system cells build a wall around the bacteria in the lungs which form turbcles, infected tissue within these dies and the gas exchange surface is damaged what effect does this disease have on the gas exchange?

Answer 23

-Reduced tidal volume
-TB also causes fibrosis which further decreases it
-As a result, they have an increased ventilation rate

Question 24

Fibrosis is the formation of scar tissue in the lungs which can form after an infection. Scar tissue is thicker and less elastic than regular tissue which means the lungs cannot expand as much, what effect does this have?

Answer 24

-Reduced tidal volume
-Reduced FVC
-Diffusion is slower across a thicker scarred membrane #
-Faster ventilation rate to get enough oxygen into the lungs to oxygenate the blood

Question 25

Asthma is a condition where the airways become inflamed and irritated. During an asthma attack, the smooth muscle lining and bronchioles contract and a large amount of mucus is produced which causes constriction of the airway. Airflow out of the lungs is also severely reduced. What effect would this have?

Answer 25

-Less oxygen enters the alveoli and moves into the blood
-The FEV is severely reduced

Question 26

Emphysema is when foreign particles become trapped in the alveoli which causes inflammation and attracts phagocytes which break down elastin (the protein found in the walls of the alveoli) . What effect does this have on the gas exchnage?

Answer 26

-Elastin helps alveoli to return to their normal shape after inhaling and exhaling
-Loss of this causes the alveoli to not be able to recoil to expel air as well
-Leads to destruction of the alveoli walls so the gaseous exchange rate is reduced
-Have an increased ventilation rate

Question 27

What do all 4 of the diseases reduce?

Answer 27

The rate of gas exchnage in the alveoli

Question 28

What effect does this have on the person?

Answer 28

-Less oxygen can diffuse into the bloodstream
-The body cells receive less oxygen
-Rate of aerobic respiration is reduced
-Less energy is released causing the person to feel tired and weak

Answer 29

Percentage change final value -original value
———————————– x100
original value