PROCESS OF URINE FORMATION

Each kidney has very minute tubular and convoluted structures known as urniferous tubules. Nephron has a double walled cup shaped structure called bowman’s capsule at its upper end.

The bowman’s capsule has numerous capillaries called glomerulus. The short region after the Bowman’s capsule is called the neck. After this the tubule is narrow and coiled. It consists of a proximal convoluted region, a Henle’s loop and a distal convoluted tubule. The post end of nephron is called collecting tubule.

Collecting tubule opens into the renal pelvis, which opens into the ureter

The waste material along with blood is brought to kidneys by the renal arteries. Blood is filtered out from blood capillaries into Bowman’s capsule under pressure which is known as Ultrafiltration. This filtrate passes through the lumen of tubular parts of nephron. During this useful products such as water, glucose, amino acid, materials, ions etc. are reabsorbedby blood capillaries surrounding the nephron. The remaining fluid contains excretory substance and is called urine. From the ureter urine passes into urinary bladder where is is stored. When the bladder is filled with urine, it contracts and urine passes out of the body.

Nephron





THE SKIN

2 Layers of the Skin

Epidermis – outer protective layer without blood vessels
Dermis – inner layer containing blood vessels, sensory nerve endings, sweat and


Functions of the Skin

Excretion – Wastes such as excess water, salt, urea and uric acid are removed from the body in sweat.
Waterproofing – The skin with its oil glands prevents the entry of water into, and loss of water out of the body.
Protection from Disease – The intact skin prevents invasion of micro-organisms and dust into the body.
Protection from Ultraviolet Rays – Pigments reduce the intake of UV rays.
Regulation of Body Temperature – The thin layer of fat cells in the dermis insulates the body. Contraction of small muscles attached to hairs forms ‘goosebumps’ and creates an insulating blanket of warm air. Also, sweat produced by sweat glands uses excess body heat to evaporate, providing a cooling effect.
Sensory Detection – The nerve endings or receptors in the dermis detect heat, cold, touch, pressure and pain.