GAS EXCHANGE IN HUMANS

Question 1

Ventilation

Answer 1

ventilation consists of inspiration(breathing in) and expiration (breathing out) which is controled by the movement of internal and external intercoastal muscles, diaphragm and ribcage.

Question 2

whre does human gaseous exchange takes place

Answer 2

in the alveoli

Question 3

alveoli

Answer 3

lungs contains lots of microscopic air filled sacs called alveoli where the gas exchange occurs.

Question 4

alveolar epithelium

Answer 4

each alveoli is made up of single layer of thin flattened cells called the alveolar epithelium

Question 5

adaptations of alveoli

Answer 5

• large number of alveoli in the lungs so a larger surface area for gas exchange.
• alveolar epithelium is only one cell thick so there is a shorter diffusion pathway and speeds up the diffusion.
• steep concentration gradient of oxygen and carbon dioxide between alveoli and capillaries which increases the rate of diffusion.

Question 6

direction of oxygen flow

Answer 6

• oxygen diffuses out of the alveoli across the alveolar epithelium and capillary endothelium and into the haemoglobin in the blood.

Question 7

inspiration mechanism

Answer 7

• external intercoastal muscles and the diaphragm contract.
• this causes the ribcage to move upwards and outwards flattening the diaphragm which then increases the volume of the thoracic cavity.
• as the volume of the thoracic cavity increases, the lung pressure decreases.
• air flows from a region of higher pressure to a region of lower pressure so air flows down the trachea into the lungs.
• inspiration is an active process, it requires energy.

Question 8

expiration mechanism

Answer 8

• the external intercoastal muscles and the diaphragm relaxes.
• this causes the ribcage to move inwards and downwards causing the diaphragm to go back in curve shape again and decreases the volume of the thoracic cavity.
• this causes pressure to increase.
• air is forced down the concentration gradient and out of the lungs
• normal expiration process doesnot need energy however forced expiration does.

Question 9

tuberculosis and gas exchange

Answer 9

• gaseous exchange surface is damaged, so the tidal volume decreases.
• reduced tidal volume means less air is inhaled in each breath.
• ## inorder to take enough oxygen, patients need to breath faster which increases the ventilation rate.