Kidney Essay

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Homeostasis is the maintenance of a steady state. With changes within and around living cells, conditions are maintained at a constant level. The ‘two major control systems, nerves and hormones, are mainly responsible for co-ordinating homeostatic mechanisms’ (Human Body) whilst using feedback. If a change in condition is detected a corrective mechanism is activated, conditions return to set point and the corrective mechanism is then switched off. The conditions are then at constant level. Some of the factors controlled by homeostatic mechanism are: body temperature, blood glucose level, water content of the body, respiration and urea being carried by the blood.

The changes within the homeostatic system is often referred to as positive or negative feedback. The reverse in change and the extent of the correction is closely monitored by the negative feedback system. The opposite to the negative feedback is the positive feedback which in a situation a change is made and is amplified rather than returned to normal. The picture shows below an example of a homeostasis mechanism, showing the changes the body would make in keeping the blood glucose at set point.

Picture 1

( http://www.bio.miami.edu/~cmallery/150/physiol/c45x10glu-homeostasis.jpg)

In the homeostatic system many organs have specific roles. The kidney as several roles as a homeostatic organ, one of the roles is the regulation of blood PH ‘the kidney excrete a variable amount of hydrogen ions into the urine and conserve bicarbonate ions’ (Principles of human anatomy) as these two activities help regulate the blood PH level.

The urogenital system ‘is a combination of two systems of the body: the reproductive system and the urinary system’ (http://www.wisegeek.com). The two systems share tissues in order to carry out their functions. The urinary system in males and females are very similar. The urinary system ‘consists of two kidneys, two ureters, one urinary bladder, and one urethra’ (Principles of human anatomy). The kidney is the main organ in the urogenital system.

The kidneys are located near the vertebral column on either side. The kidney ‘receives the largest blood supply of any organ, per gram of tissue’ (Human Biology). This ‘is supplied with oxygenated blood via the renal artery and drained of deoxygenated blood by the renal vein’ (generalmedicine). The kidney can be divided in to two main areas the cortex and the medulla. The cortex is the outer region which ‘contains the renal capsules (also called the bowman’s capsules) and the first convoluted and second convoluted tubules (also called the proximal and distal tubules)’ (Human Biology). The medulla consists of ‘the loop of henle and the collecting ducts’ (Human Biology) these ducts enable the delivery of urine into the open space of the kidney called the pelvis.

The nephron is the main functional unit of the kidney. A ‘human kidney contains about a million nephrons’ (Human Biology). The nephrons roles are filtering the blood of small molecules such as sodium, glucose and water but leaving the large molecules untouched. Also reabsorbing the required useful quantities of solutes in which the body still requires.

Picture 2

(http://www.standardofcare.com/mwiki/images/a/ae/Kidney_cIvyRose.JPG)

At ‘one end of the renal tubule is a cup-shaped membrane’ (The human body book) called the Bowman’s capsule that surrounds a knot of capillaries called the glomerulus. The glomerulus is the first step in filtrating blood into urine. Blood flows in at high pressure to the glomerulus, which comes from the afferent arteriole and leaves through the efferent arteriole. The blood plasma travelling in the afferent arteriole ‘of the kidney that becomes glomerular filtrate is the filtration fraction’. (Principles of anatomy and physiology page 1030). Although the filtration fraction will differ depending on your health ‘around (16-20%) is typical’ (Principles of anatomy and physiology) the rest of the...
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