1.2 : TRANSPORT OF OXYGEN What is DIFFUSION ?

v Gas molecules move from a place where there are many molecules (higher concentration) to a place with fewer molecules (lower concentration)

v Example ???

Prepared  by  Ms  Sue  Soh  

1.2 : TRANSPORT OF OXYGEN Diffusion of OXYGEN from the ALVEOLI into BLOOD

CAPILLARIES

•  Alveoli are surrounded by blood capillaries

•  Inhalation : –  fresh air (more

oxygen) is taken into the alveoli

– Oxygen from alveoli diffuses into the blood capillaries

Prepared  by  Ms  Sue  Soh  

1.2 : TRANSPORT OF OXYGEN Diffusion of OXYGEN from the ALVEOLI into BLOOD

CAPILLARIES

•  Oxygen combines with haemoglobin in red blood cells producing oxyhaemoglobin

•  Blood that contains oxyhaemoglobin is called oxygenated blood (bright red)

Prepared  by  Ms  Sue  Soh  

1.2 : TRANSPORT OF OXYGEN Diffusion of OXYGEN from the ALVEOLI into BLOOD

CAPILLARIES

•  At the same time, CO2 in the blood capillaries (higher concentration) diffuses into the alveoli (lower concentration) to be expelled during exhalation

Prepared  by  Ms  Sue  Soh  

1.2 : TRANSPORT OF OXYGEN Why ALVEOLUS allows the diffusion of gases?

Present in large numbers

in the lungs

Richly supplied

with blood capillaries

Moist wall

One-celled thick wall

Prepared  by  Ms  Sue  Soh  

1.2 : TRANSPORT OF OXYGEN Transport of OXYGEN to the BODY CELLS

•  Oxygenated blood surrounding the alveoli first flows to the heart

•  Heart pumps the blood out to the body cells which require oxygen

Alveolus

Body cells Prepared  by  Ms  Sue  Soh  

1.2 : TRANSPORT OF OXYGEN Transport of OXYGEN to the BODY CELLS

•  Gases exchange (diffusion) happens between CO2 and O2 –  Body cells

receive O2 and CO2

–  Blood capillaries release O2 and receive CO2

–  Blood capillaries carry deoxygenated blood (dull colour)

Prepared  by  Ms  Sue  Soh  

1.2 : TRANSPORT OF OXYGEN Transport of OXYGEN to the BODY CELLS

•  Deoxygenated blood is carried back to the heart and then to the blood capillaries surrounding the alveoli in the lungs

•  Deoxygenated blood releases CO2 to the alveoli & absorbs O2, forming oxygenated blood again.

Prepared  by  Ms  Sue  Soh