respiration

function of nostrils

1. hairs and mucus trap dust and foreign particles

2. mucus warms and moistens air

3. sensory cells in mucus membrane detect harmful chemicals

trachea

supported by C-shaped cartilage rings to ensure the trachea is always kept open

function of epithelium of trachea and bronchi

• gland cells in the epithelium secrete mucus, which traps dust and foreign particles

• ciliated cells have ciliated which sweep dust and foreign particles up the bronchi and trachea, into the pharynx

(the mucus can then be coughed out through the pharynx pe swallowed into the oesophagus)

function of alveoli

• site of gas exchange

gas exchange at alveoli

• gas exchange at the alveoli occurs via diffusion

• blood flowing to the lungs has a lower concentration of oxygen and a higher concentration of carbon dioxide than the atmospheric air entering the lungs

• hence, a concentration gradient for oxygen and carbon dioxide is set up between the blood into the capillaries and the air in the alveolus

adaptations of lungs and alveoli for efficient gas exchange

lungs:

1. numerous alveoli in lungs - provides a large surface area to volume ratio for more efficient gaseous exchange

alveoli:

1. alveoli is one-cell-thick - shortens diffusion distance for gases, for more efficient diffusion of gases in and out of the alveoli

2. thin film of moisture in alveoli - allows gas to dissolve in thin film of moisture

3. each alveolus is surrounded by a network of blood capillaries - continuous flow of blood maintains concentration gradient of gases

how is oxygen absorbed form the lungs into the blood into the cells of tissues

• air in alveoli contains a higher concentration of oxygen

• oxygen dissolves in the thin film of moisture in the inner walls of the alveolus and then diffuses into the blood capillaries

• oxygen combines reversibly with haemoglobin to form oxyhaemoglobin

• when the blood passes through tissues ooor in oxygen, the haemoglobin releases oxygen, which diffuses through the walls of the blood capillaries onto the cells of the tissues

breathing in

• diaphragm muscles contract, diaphragm flattens downwards

• external intercostal muscles contract, while internal intercostal muscles relax

• ribs swing upwards and outwards

• volume of thoracic cavity increases

• air pressure in the lungs decreases

• atmospheric pressure is now higher than air pressure within the lungs, so air is forced into the lungs

breathing out

• diaphragm muscles relax and diaphragm arches upwards and becomes dome shaped

• external intercostal muscles relax, while internal intercostal muscles contract

• ribs swing downwards and inwards

• volume of thoracic cavity decrease

• this increases air pressure in the lungs

• atmospheric pressure is now lower than air pressure within the lungs, which forces air out of the lungs

nicotine

carbon monoxide

tar

irritant particles

chronic bronchitis

emphysema

lung cancer

aerobic respiration

anaerobic respiration

differences between aerobic respiration and anaerobic respiration