Anaerobic and Aerobic Respiration
Aerobic respiration is the breakdown of simple substances such as glucose, amino acids, sugars etc. to release energy. In this respiration a large number of oxygen is used and as a result water and carbon dioxide is produced. In such respiration a large number of energy is produced. Most organisms on the planet respire aerobically.
Anaerobic respiration is breakdown of simple substances with less oxygen involved in the process. In such respiration a low number of energy is produced. This kind of respiration is commonly observed in humans while intense exercising. When you exercise more than what your body can take such reactions may occur. At the end of the reaction lactic acid will be produced in your muscles. If the exercise continues enough lactic acid is produced to give you a fatigue causing the muscular pain you would feel after exercise.
Inhaling and Exhaling
First you need to understand how lung is connected to the ribs. The lung is structured in the pleural cavity. The pleural cavity is lined with two membranes called pleura (pleuron). The inner pleuron covers the lungs while the outer pleuron covers the wall of the thorax and the diaphagram. There is a lubricating fluid between these two membranes which prevents friction when the lungs expand and contract.
The chest walls are supported by the ribs. The ribs have two kinds of muscles between each one. The internal and external inter-coastal muscles. When one contracts the other relaxes like any other. This is how the lungs freely expand and contract.
When we inhale the external intercoastal muscles contract while the internal intercoastal muscles relax causing the ribs to swing upwards and outwards.
When we exhale the internal intercoastal muscles contract and the external intercoastal muscles relax causing the ribs to swing downwards and inwards.
Tissue respiration has been discussed in previous articles. It is basically oxidation (breaking) of simple molecules so that energy is released. It occurs inside the cell. The mitochondria breaks the simple molecules down and releases energy which is used. The energy which is left out is stored in adenosine triphosphate (ATP). Later the ATP(s) are broken down to collect the energy should the need arises.
This respiration starts from the nostrils and ends at the lungs where oxygen is diffused into blood. We breath in air (inhale/inspiration), the air molecules enters our nostrils. The nostrils have hair in it and its layer is lined with mucus which traps irritant particles and bacteria in the air. The same purpose is fulfilled by the mucus. The mucus also keeps the nostrils warm and moist.
The oxygen which enter with the air molecules move through the pharynx and larynx and into the trachea. The trachea is right in front of the gullet (esophagus). Its wall has rings of cartilage around it which prevent it from closing in. The trachea then splits into two tubes, one for each lung, which are called bronchus. The bronchus then further divides into 2 or 3 bronchial tubes which keeps on dividing until it reach the end of the lobes of the lung. Here the tube does not have cartilage rings and is called bronchial.
The bronchial is connected to smaller air sacs more commonly called alveoli (singular; alveolus). The air then diffuses through the epithelial walls of the alveolus and the blood vessels and enters the blood. It combines with the hemoglobin and forms oxyhemoglobin. The carbon dioxide in the blood diffuses to the alveolus. The blood then provides oxygen to different parts of the body where oxygen is low in concentration.
Respiration in plants
Some may think that plants respire at night and perform photosynthesis in day. This is not true. The plants respire all the time like any organisms on the planet. At night there is no photosynthesis and the process of respiration is fast (or intense). At day time the rate of photosynthesis occurs more rapidly than the rate of respiration causing the oxygen to be given out.
How this works is that at night when all the oxygen is given out the oxygen concentration is low in the plant. So the plant absorbs the oxygen particles from the atmosphere. The oxygen particles enter through the stomata and diffuse from cell to cell until it reaches the area of cells with lower oxygen concentration. All the carbon dioxide collected from this moves through intercellular spaces and is then released through the stomata.
Another way of respiration is that the roots of the plants absorb the oxygen from the water in the soil and diffuse it from cell to cell to the low oxygen areas.
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