Kidneys are complex organs; they perform three vital, life-sustaining functions: They clean waste materials and extra fluids from the body, they also filter the blood and maintain normal body chemistry, and they regulate blood pressure and the production of red blood cells.
The kidneys are two bean shaped organs that lie on either side of the vertebral column below the diaphragm and liver. A fibrous capsule encases the kidney, this is known as the renal capsule. (Foster & Smith 2005) The renal capsule provides an impermeable barrier to infections of the kidney surface. This is the first of three protective layers around the kidneys. Outside the renal capsule is a middle layer of fat, this is called the adipose capsule. The fat tissue of the capsule helps cushion the kidney against blows. Outside the adipose capsule is the renal fascia, the fascia is composed of dense fibrous connective tissue that helps to protect the kidney whilst anchoring it to the nearby tissues. (Alcamo 1997)
Each adult kidney weighs about 160g and is about 11cms long, 5 7cms wide and 2.5 cm thick. A kidney each contains about 160km of blood vessels, and more than a million separate lengths of extremely fine tube called kidney tubules, which have a combined length of approximately 60km. The indentation of the bean-shaped organ is known as the hilus. This is the point where the blood vessels, ureter, and nerves enter or exit the kidney. (Becket 1982).
[...] One afferent arteriole is distributed to each nephron, where the arteriole divides into a tangled network of around fifty fenestrated capillaries called the glomerulus. The glomerulus is surrounded by the Bowman's capsule The Bowman's capsule is the cup shaped mouth of the nephron which is made of simple squamous epithelium, which makes up the parietal (outer) epithelium. The visceral (inner) epithelium consists of podocytes, which have numerous small feet called pedicels. (Vieira Lazaroff 2004) Pedicels interdigitate, like the fingers of a clasped hand, as they wrap around the glomerular capillaries. [...]
[...] (Parker 2001) As well as reabsorption of materials from the filtrate to the blood, other materials are placed into the filtrate by a process known as secretion. Secretion plays a big part in the balance of ions in the blood. An excess amount of could cause cardiac arrest, the level is lowered by secreting it into the collecting duct. When blood gets to acidic, ions are secreted into the PCT and the collecting duct, this raises the pH to normal. [...]
[...] A thin layer of spongy erectile tissue lies immediately beneath the mucous coat. The mucous coat is pale and it is lined by stratified squamous epithelium. It is the action of the sphincters that regulate the process or urination, which is sometimes known as micturation. Micturation is controlled by a reflex centre located in the spinal cord. A full bladder activates stretch receptors that send pulses to the micturation centre. As a result, parasympathetic neurons are activated causing rhythmic contractions of the bladder and relaxation of the internal urethral sphincter. [...]
[...] The solution is constantly replaced to maintain a favorable concentration gradient for diffusion of waste and excess solutes in the blood. (Tortora & Grabowski 2001) (www.ikidney.com/NR/rdonlyres) Bibliography Alcamo, I (1997) Anatomy Coloring Workbook USA, Princeton Review Publishing Anon (2002) The Urinary System: Kidney Structure and Function < http://bioweb.usc.edu/courses/2002-spring/documents/bisc113-kidneys.pdf> (Accessed 22nd February 2005 15:32) Anon (2002) Your Kidneys and How They Work < http://kidney.niddk.nih.gov/kudiseases/pubs/yourkidneys/> (Accessed 20th February 2005 18:30) Anon (2005) Kidney Function < http://www.nwkidney.org/yourhealth/yourkidneys/ (Accessed 19th February 2005 19:25) Beckett, B.S (1982) Biology : A Modern Introduction Oxford, UK, Oxford University Press Chute, R.M. [...]
[...] (Fox 1999) Bladder The bladder is a triangle-shaped, hollow muscular sac that is used for the temporary storage of urine. It is located in the lower abdomen and it is held in place by ligaments that are attached to other organs and the pelvic bones. The bladder has three layers of flexible muscular walls, the inner layer is called the mucous coat and it consists of several layers of transitional epithelial cells. The second layer, the subserous coat, consists of fibrous tissue which contains many elastic fibers. [...]
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