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Write a detailed reasoned explanation of the physiology of the three systems (cardiovascular, respiratory and digestive) in relation to energy metabolism.

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Write a detailed reasoned explanation of the physiology of the three systems (cardiovascular, respiratory and digestive) in relation to energy metabolism. Respiratory system The thorax (chest), is n airtight box containing the lungs and their associated tubes, the bronchi and the heart. Air can enter the thorax via the nose or the mouth. The nose contains fine bones on its side walls which are curled like scrolls and covered with moist ciliated mucous membrane, rich in blood capillaries. This arrangement produces a large surface area over which incoming air flows. During the passage through the nose, the air is warmed and moistened by he close contact with the mucous membrane and filtered by the ciliated cells. By the time the air reaches the throat, it is warmed at almost body temperature, moistened to almost saturation point and most foreign materials such as dust, carbon particles and many pathogens have been filtered out. The trachea starts at the back of the throat, or pharynx, and divides into two main bronchi, each serving one lung on each side of the heart. ...read more.


This means that when the chest wall moves in breathing, the lungs move with it. Each bronchus after repeatedly dividing ends in a group of ingle-layered globe-shaped structures called alveoli. The wall of the alveoli consist o very thin, flat simple squalor epithelium, and each alveolus is surrounded by the smallest blood vessels known as capillaries. The walls of the capillaries are also composed of simple squamous epithelium, in a single layer. This means that the air entering the alveoli during breathing is separated from the blood by only two single-layered, very thin wall. There are elastic fibres around the alveoli enabling them to expnd and recoil with inspiration and expiration. A film of moisture lines the inside of each alveolus to enable the air gases to pass into solution. As the 2 layers of epithelium are very thin and semi-permeable, the dissolved gases can eaily ad rapidly pass through, in the process called gaseous exchange. Ventilation is the movement of air in and out of the thorax to replenish the oxygen supply and remove surplus waste products (carbon dioxide + water). ...read more.


Diffusion will stop in time, as the numbers o molecules become more evenly distributed. In the human body, where diffusion is a common of transport, the state of equilibrium is not desirable as it means overall transport would cease. To prevent equilibrium being attained, the high concentration must be continually kept high and the low concentration must also be maintained. Diffusion can only occur here there is no barrier at all to the molecules or where the barrier is thin. The rate of diffusion is enhanced with an increased surface area- usually by folds or similar structures to alveoli, and with temperature, since warmth increases the random motion of molecules. The oxygen in the air we breathe combines with the haemoglobin in red cells through the alveolar-capillary membrane. This O2 is delivered to the cellular capillaries via the circulatory system. There the O2 is utilized in glucogenesis. The waste product is CO2 which is combined in the blood with H2O making H2CO3 (carbonic acid). The CO2 disassociates into CO2 and H2O in the pulmonary capillary bed and the CO2 diffuses into the alveoli and is exhaled into the air. Kathryn Munnis M1 + D1 ...read more.

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