Biology Presentation

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THE PROCESS OF GASEOUS EXCHANGE ACROSS THE SURFACE OF THE ALVEOLUS AND BLOOD CAPILLARIES AND BETWEEN THE TISSUE CAPILLARIES AND BODY CELLS • Gaseous exchange across the alveolus occurs by diffusion.

• The greater the concentration gradient of respiratory gases across the respiratory surface , the greater the rate of diffusion.

THE CHARACTERISTICS OF THE RESPIRATORY SURFACE IN THE ALVEOLI • A large surface area for gaseous exchange • A thin one-cell thick epithelial surface which is moist and permeable to gas • An underlying capillary network , which is also one-cell thick , that carries oxygen away and brings carbon dioxide to be eliminated

PARTIAL PRESSURE OF GAS • The partial pressure of a gas is : (a) The pressure exerted by that particular gas (b) A measure of its concentration (c) Is higher if its concentration is greater

2.Atmosphere is a mixture of different gases of different concentration 3.A gas diffuses from a place of high partial pressure to a place of low partial pressure

IN THE BLOOD CAPILLARIES… … 1.Blood which enters the blood capillaries surrounding the alveoli has a higher partial pressure of carbon dioxide 2.Carbon dioxide diffuses out of the blood capillaries into the alveoli and is then expelled through the nose or mouth into the atmosphere

IN THE LUNGS…… • The partial pressure of oxygen (concentration of oxygen) in the air of the alveoli is higher compared to the partial pressure of oxygen in the blood capillaries • Oxygen dissolves in the film of water on the surface of the alveoli and then diffuses across the blood capillaries into the blood

Blood leaving the blood capillaries (higher partial pressure of oxygen, lower partial pressure of carbon dioxide)

Oxyge n Carbon dioxide Exhaled air Inhaled air Oxygen diffuses into the blood capillary and combines with haemoglobin in red blood cells to form oxyhaemoglobin

Carbon dioxide diffuses outRed of the blood blood plasma into cell the alveoli

Blood capillaries

Blood entering the blood capillary (higher partial pressure of carbon dioxide, lower partial pressure of oxygen)

Capillaries wall

PARTIAL PRESSURE OF OXYGEN AND CARBON DIOXIDE IN THE ALVEOLI AND BLOOD CAPILLARIES PARTIAL PRESSURE GAS

Oxygen Carbon dioxide

AIR IN THE ALVEOLI

High

Low

BLOOD CAPILLARIES

EFFECTS

Low

Oxygen diffuses from the alveoli into the blood capillaries

High

Carbon dioxide diffuses from the blood capillaries into the alveoli

PARTIAL PRESSURE OF OXYGEN AND CARBON DIOXIDE IN THE TISSUE CAPILLARIES AND BODY CELLS PARTIAL PRESSURE

GAS

Oxygen Carbon dioxide

TISSUE CAPILLARIES

High

Low

BODY CELLS

EFFECTS

Low

Oxygen diffuses from the tissue capillaries into the body cells

High

Carbon dioxide diffuses from the blood capillaries into the alveoli

THE TRANSPORT OF RESPIRATORY GASES IN HUMANS 1.Transport of Oxygen 2.Transport of Carbon dioxide

TRANSPORT OF OXYGEN • Oxygen in the blood that leaves the alveoli is transported to the body cells for cellular respiration • The transport of oxygen is carried out by the blood circulatory system lungs Haemoglobin + oxygen  oxyhaemoglobin • Oxygen combines with the body cells respiratory pigment called haemoglobin in the red blood cells to form an unstable product called oxyhaemoglobin • When blood passes through tissues with low partial pressure of oxygen , the oxyhaemoglobin dissociates itself to release oxygen molecules

TRANSPORT OF CARBON DIOXIDE

• About 7% of the carbon dioxide is transported as dissolved carbon dioxide in the blood plasma • Another 23% of the carbon dioxide binds to the haemoglobin and is transported in the form of a substance known as carbaminohaemoglobin • The remaining 70% is transported in the blood in the form of bicarbonate ions (HCO3-)

THE TRANSPORT OF CARBON DIOXIDE FROM THE BODY CELLS TO THE TISSUE CAPILLARIES • Body cells release carbon dioxide •

Carbon dioxide diffuses into the blood plasma and then combines with the red blood cells

•

Carbon dioxide reacts with water to form carbonic acid (H2CO3)

•

Red blood cells contain the enzyme carbonic anhydrase to catalyses this reaction

•

The carbonic acid then dissociates into a hydrogen ion (H+) and a bicarbonate ion (HCO3-)

•

Most of the bicarbonate ions diffuse into the blood plasma and are carried in the blood plasma to the lungs

THE TRANSPORT OF CARBON DIOXIDE FROM THE BLOOD CAPILLARIES TO THE ALVEOLI • The process which takes place in the lungs is the reverse of what happens in the tissue capillaries • The bicarbonate ions diffuse from the blood plasma into the red blood cells and form carbonic acid again • Carbonic acid breaks down to carbon dioxide and water • Carbon dioxide diffuses from the blood capillaries into the alveoli. Thereafter , it is expelled during exhalation

THE EXCHANGE OF RESPIRATORY GASES BETWEEN THE BLOOD AND BODY CELLS 1. The partial pressure of oxygen in the blood is higher than the partial pressure of oxygen in the cellls 2. Cellular respiration depletes the oxygen content in the cell 3. The oxyhaemoglobin breaks down and release oxygen then diffuses through the capillary walls into cells 4. Cellular respiration produces carbon dioxide 5. The partial pressure of carbon dioxide in the cell higher than the pressure in the tissue capillaries

THE COMPOSITION OF INHALED AND EXHALED AIR CONTENT INHALED AIR EXHALED AIR REASON Oxygen

21.9%

16.4%

Used in cellular respiration

Carbon dioxide

0.03%

4.1%

Produced in cellular respiration

79.0%

Neither used nor produced in cellular respiration

Saturated

Product of cellular respiration. Evaporation from the lungs during expiration

Nitrogen

79.0%

Water vapour

Varies and is never saturated

Temperature

Room temperature (atmospheric temperature)

Body temperature

Air warmed by body temperature

CREDITS

SPECIAL TO TAN CHEE LEI THANK

Background Music

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THANK YOU THE END LOW XIN YI CHANG JIT KANG Presentation Designer/Editor CHEONG SHI HUI Assistants

TAN LI MIN TAN LI PENG NG THEN JACK KUGENESWAREN

TAN SHEA LEE THOO ZHIJIN PUNEETHA RAJ VASANTHAN