GASEOUS_EXCHANGE.pptx for biology csec students

Gaseous exchange

1. GASEOUS EXCHANGE

2. Is respiration and breathing the same thing What is the difference between breathing and respiration Breathing  is the biological process of inhaling and exhaling of the gases between the cells and the environment. The  mechanism of breathing  involves various respiratory structures such as the windpipe, lungs and nose . Respiration is the process by which the energy in food is made available for a cell to do the work necessary to keep it alive.

3. Breathing – involves in the inhalation and exhalation of air from the lungs due to changes in volume and pressure.

4. Gaseous Exchange Gaseous exchange – involves the exchange of gases across a gaseous exchange surface via the process of diffusion. Eg. alveoli in humans, gill lamellae in fish, leaves of plant, cell membrane of unicellular organisms Common features: All are in contact with the environment, even if they are enclosed deep inside the body Have a large surface area to volume ratio Thin : gases can diffuse through them rapidly Moist : gases can dissolve before they diffuse through the surface They have a rich blood supply to quickly transport gases between the surface and the body cells.

5. Mechanism of gaseous exchange in humans. Gaseous exchange in human occurs in the lungs of humans. Humans have two lungs composed of thousands of passages called Bronchioles and millions of swollen air sacs called alveoli. Each lung is surrounded by pleural membrane which have pleural fluid between it Air enters the nose or mouth and moves down the trachea, the trachea divides into two bronchi. The trachea is supported by rings of cartilage which keeps it open so air can pass easily Each bronchus into smaller tubes called the bronchioles, and at the end of each bronchioles are many tiny air sacs called alveoli and gaseous exchange occurs in the alveoli

6. The walls of the alveoli are the gaseous exchange surface The smallest blood vessels , capillaries are closely wrapped around each alveolus. Blood is brought to and taken away from the alveolus Oxygen Is diffused into the capillary across the walls of the alveolus and the blood become oxygenated Carbon dioxide diffuses from the capillary into the alveolus and is exhaled out of the body The walls of the alveolus and the capillary are very thin so that diffusion can readily occur. Each lungs receives blood from the heart via a pulmonary artery and blood is carried back to the heart via a pulmonary vein

7. The trachea is lined with mucus, slimy substance which traps and holds dust and microorganisms. The trachea is also lined with microscopic hair-like extensions called cilia. These beat in a wave-like manner, moving the mucus containing dust and microorganisms upwards and out of the lungs. The two lungs are surrounded by the ribs which form the chest cavity or thorax. The ribs have intercostal muscles between and a dome-shaped sheet of muscle, the diaphragm Movement of the ribs and diaphragm, brought about by the muscles contracting and relaxing, cause air to move in and out of the lungs. Breathing in is called Inspiration and Breathing out is called Expiration

8. What is the difference between inspiration and expiration

9. Inhaling External intercostals muscles contract and lift the ribs upwards and outwards Muscles in the diaphragm contract and pull the diaphragm down The volume (space) of the chest cavity increases and pressure is made low Air moves into the lungs where the pressure is lower than the pressure outside the body

10. Exhaling External intercostals muscles relax and pull the ribs downwards and inwards Muscles in the diaphragm relax and the diaphragm moves back upwards The volume (space) of the chest cavity decreases and the pressure is made high Air moves into the lungs where the pressure is higher than the pressure outside the body.

11. Di ff erences be t ween inspired and expired air

12. Gaseous Exchange surface in fish Fish use gills to absorb oxygen dissolved in water and release carbon dioxide into the water Most fish have five pairs of gills covered by a bony plate called the operculum. Each gill consists of a bony arch with 2 rows of gill filaments (primary lamellae) attached. The filaments are very thin and the surface of these gill filaments is folded into many gill plates (secondary lamellae), perpendicular to the primary lamellae, to give a large surface area for exchange Blood capillaries carry deoxygenated blood close to the surface of the secondary lamellae, where the exchange takes place

13. Blood flows along the bony arch, down the primary lamellae and into the capillary network of the secondary lamellae. It flows through the capillaries in the OPPOSITE direction to the flow of water over the lamellae, to maximize oxygen absorption

14. Mechanism of gaseous exchange in plants. Gaseous exchange occurs in the leaves, stems and roots of plants by direct diffusion between the intercellular air spaces and all the cells in these organs that are in contact with the air space. Gases diffuse between the atmosphere and the air spaces through the stomata of leaves and the lenticels of bark covered stems and roots. The walls and membranes of all the cells inside the leaves, stems and roots of plants form the gaseous exchange surface. The direction of movement of gases depends on whether the organ of the plant is also carrying out photosynthesis.

15. Gaseous Exchange in Photosynthesizing organs Movements of gases into and out of photosynthesizing organs mainly leaves depends on the time of the day. During the night, only respiration occurs. Oxygen diffuses in and Carbon dioxide diffuses out During the day, the rate of photosynthesis is greater than the rate of respiration. Carbon dioxide diffuses in and Oxygen diffuses out

16. Which gases leave and enter a leaf a 1. 12noon 2. 12 midnight Adaptation of the gaseous exchange surface

17. Effects of smoking cigarettes: Nicotine: Causes cigarettes to be addictive Reduces air flow into and out of the lungs by constricting the bronchioles Paralyses cilia in the trachea which remove dirt and bacteria Raises the blood pressure and heart rate, increasing risk of heart disease Increases risk of osteoporosis

18. Carbon monoxide: Combines irreversibly with hemoglobin in the blood therefore causing less oxygen to be transported in the blood Reduces smoker’s ability to do strenuous exercise Causes breathlessness For pregnant women, low oxygen in the fetus results in low birth weight Tar: Is carcinogenic therefore increases risk of lung cancer Sticks to cells in the lungs Irritates and damages lung tissue Breaks down the alveoli, therefore decreasing the total surface area for gaseous exchange – called emphysema Causes bronchitis which is inflammation of the lining of the air passages which produces mucus leading to ‘ smokers cough ’