SS2 Biology Lesson Note on The Kidney

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THE KIDNEY

The kidney is the major excretory and osmo-regulatory organ of mammals. All vertebrate have a pair of kidney. The kidney has a rich supply of blood and regulates the blood composition. It ensures the composition of the tissue fluid is maintained at an optimum level for the cells bathe by it and enables the cell to function efficiently at all times.

Structure of the kidney

The human kidney plays dual role of removal of waste (mainly nitrogenous waste) from the body and also osmo-regulation maintaining the body water level and ensuring adequate aqueous medium for the body metabolic processes.

Each kidney is a bean shaped brown organ attached to the dorsal wall of the abdominal cavity. The concave part of the kidney called the hilum is connected to the renal vein and renal artery which carry blood into and out of kidney respectively. The third tube, ureter leads downwards from each kidney to the bladder (the bladder is connected to the outside via urethra.

Kidney

Approximately one million nephrons (right) compose each bean-shaped kidney (left). The filtration unit of the nephron, called the glomerulus, regulates the concentration within the body of important substances such as potassium, calcium, and hydrogen, and removes substances not produced by the body such as drugs and food additives. The filtrate, urine, leaves the nephron through the long renal tubule. Chemical signals triggered by the body’s need for water and salt cause the walls of the tubule to become more or less permeable to these substances, which are reabsorbed accordingly from the urine.

A longitudinal section of kidney shows three distinct regions: the outer contex, an inner medullar and the funnel shaped pelvis. The cortex and pyramid is the location of the urinary tubules which are the structures responsible for separating waste from the blood. There are millions of them and their function is enhanced by their connection with the rich network of capillaries in the kidney.

Each urinary tubule consists of a cup-like capsule known as the Boman’s capsule leads away a coiled section of the tubule called the proximal convoluted tubule.

Beyond the cortex in the medulla the tube forms a U-shaped loop called the loop of Henle. The far arm of the loop leads to another coiled section of the loop called the distal convoluted tubule which is also richly supplied with capillaries connected to the renal veins. After this point, the tubule leads back into the cortex to join other tubules which eventually leads out through the pyramid into the pelvis.

Ebola Virus Infection

The Ebola virus is highly infectious and can spread through the use of unsterilized needles or through contact with an infected individual or the corpse of someone who has died from the disease. About one week after infection, the virus begins attacking blood and liver cells (1). As the disease swiftly progresses, the virus may destroy vital organs such as the liver and kidneys (2), leading to massive internal bleeding (3). Shock and respiratory arrest soon follow, then death.

Functions of the kidney

The main function of kidney is osmo-regulation, excretion and secretion of hormones. The removal of waste products from the body by the kidney is known as excretion. The kidney also function as endocrine gland by producing two namely erythropoietin and calcitrol. Erythroprorethin acts on the bone marrow to increase the production of red blood cells, while calcitro promotes the absorption of calcium from food in the intestine and acts directly on bones to shift calcium to the blood stream.

Osmoregulation is controlled by variation of quantities of water returned to the blood from the kidneys during selective reabsorption as follows:

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