Human Excretion and Kidney Physiology

A supply of amino acids in the blood is kept at a normal level. Any spare which has not been absorbed cannot be stored,  but is converted into the waste products, called urea,  when at the liver, and is then sent to the kidneys to be removed from the body as urine. The remainder of the amino acid molecule is not wasted;   it is changed into a carbohydrate,  that can be used.

It starts from the neck of the Bowman's capsule and it is highly convoluted. It lies in the renal cortex. The wall consists of a single layer of columnar cells bearing a lot of microvilli on the surface. It mainly reabsorbs glucose in the kidney.

It is a V-shaped segment of the nephron, located in the renal medulla. It consists of two straight parallel limbs, a descending limb, which is a continuation of the PCT and enters into the renal medulla and an ascending limb, which re-enters the renal cortex and joins the DCT.

The glomerulus lining is such that it only allows small molecules, to filter through, like glucose, plasma, ions like sodium and potassium, urea, etc. The larger molecules, like blood cells and protein, cannot pass through the glomerulus. So, proteins are not present in glomerular filtrate. The glomerular filtrate consists,  primarily of water, excess salts (primarily Na+ and K+), glucose and urea.

The renal sinus is the cavity within the kidney, which houses the renal pyramid. Nerves and blood vessels pass into the renal sinus,  through the hilus.

The cortex of the kidney is the outer section,  which covers the internal medulla. The cortex is visible near the outer edge of the cross-sectioned kidney. It is composedof blood vessels and urine tubes and is supported by a fibrous matrix.

A hepatic vein carries oxygen depleted blood out of the liver, with highest concentration of urea, into the inferior vena cava. The term vein refers to a blood vessel,  that transports blood back to the heart. The term hepatic, relates to the liver.

The cortex of the kidney is the outer section,  which covers the internal medulla. The cortex is visible near the outer edge of the cross-sectioned kidney. It is composedof blood vessels and urine tubes, and is supported by a fibrous matrix.

Cirrhosis is a condition in which the liver slowly deteriorates and malfunctions due to chronic injury. Scar tissue replaces healthy liver tissue, partially blocking the flow of blood, through the liver.

It contains least amount of urea.Cell waste is discharged in the veins for excretion through the kidneys. The body circulates about 425 gallons of blood through the kidneys on a daily basis, but only about a thousandth of this is converted in urine. The remainder goes back into circulation,  through the renal arteries. From the Bowman's capsule, the blood is carried through the compact network of capillaries,  that forms the glomerulus within the capsule. The capillaries eventually reconverge into small venules,  which lead to the larger renal veins. There are two renal veins, one extending from each lobe of the kidney, and opening into the vena cava.

Glucagon is a hormone, secreted by the pancreas, that raises blood glucose levels. It's effect is opposite that of insulin, which lowers blood glucose levels. The pancreas releases glucagon when blood glucose levels fall too low. Glucagon causes the liver to convert stored glycogen into glucose, which is released, into the bloodstream.

Ultrafiltration occurs at the barrier between the blood and the filtrate, in the renal corpuscle or Bowman's capsule in the kidneys. The Bowman's capsule contains a dense capillary network called the glomerulus. Blood flows into these capillaries through a wide afferent arteriole and leaves through a narrower efferent arteriole. The high pressure forces small molecules, such as,  water, glucose, amino acids, sodium chloride and urea,  through the filter, from the blood in the glomerular capsule across the basement membrane of the Bowman's capsule,  and into the nephron. This type of high pressure filtration is ultrafiltration. The fluid formed in this way is called glomerular filtrate.

The urinary bladder is a hollow muscular organ that stores urine produced by the kidneys until it is excreted from the body through the urethra.

It is a kidney related disorder where due to infection or injury in the basement membrane, there is inflammation of glomerulus. It progressively leads to renal failure or death.

Proximal convoluted tubule is the part of proximal nephron in which maximum reabsorption occurs.