Urinary System

two Kidneys, two Ureters, the urinary Bladder and the Urethra.

The Kidneys make up the body’s main purification system. They remove waste products, many of which are toxic, from the blood.

The Ureters carry urine from the kidneys to the urinary bladder

The Urinary bladder a saclike structure which collects urine from the ureters and serve as a urine reservoir

The Urethra a tubular structure, which carries urine from the bladder to the outside the body

The lateral surface of each kidney is convex while the medial surface is concave and has a slit called Hilum. The hilum opens into the Renal Sinus, a cavity that contains fat and connective tissue. The ureter at its superior end forms a funnel-shaped sac called the Renal Pelvis, which is located inside the renal sinus. The pelvis contains Minor Calyces

They filter blood plasma, separate wastes from the useful chemicals and eliminate the waste while returning the rest to the bloodstream. They regulate blood volume and pressure by eliminating or conserving water.The kidneys help regulate the concentration of major ions such as Na+, Cl-, K+, Ca+, and HPO4-2.They secrete variable amounts of H ions to help regulate the extracellular fluid pH. The kidneys secrete a hormone, erythropoietin, which regulates the synthesis of red blood cells in bone marrow. They play a important role in controlling blood levels of Ca2+ by regulating the synthesis of vitamin D.

Renal arteries and veins

Nephrons are called the functional units of the kidney because they are the smallest structural components capable of producing urine. A nephron consists of two principal parts, which are a Renal Corpuscle, where the blood plasma is filtered and a Renal Tubule that processes this filtrate into urine.

Each renal corpuscle consists of the enlarged end of nephron, called Glomerular (Bowman’s) Capsule and a network of capillaries called Glomerulus. The glomerular capsule outer layer (wall) is called Parietal layer, composed of simple squamous epithelial cells. The inner layer is called the Visceral layer, composed of highly modified epithelial cells called Podocytes, which wrap around the glomerular capillaries.

It is a duct that leads away from glomerular capsule and becomes highly coiled and ends at the tip of medullary pyramid.

They have very long nephron loops that extend to the apex of the renal pyramid.-The juxtamedullary nephrons are important because they are solely responsible in regulating water balance

The kidney converts blood plasma to urine in three major stages namely: Filtration, absorption and secretion. The final product, urine produced by the nephrons consists of solutes and water filtered and solutes secreted into the nephron minus the solutes and water that are absorbed.

the glomerular capillaries

Glucose and amino acids are reabsorbed by active transport. Water is reabsorbed by osmosis. Proteins are reabsorbed by endocytosis. Sodium ions are reabsorbed by active transport

It is the process of reclaiming water and solutes from the tubular fluid and returning them to the blood

The rate of filtration varies with the filtration pressure, which changes with the diameters of the afferent and efferent arterioles

The formation of filtrate depends on a pressure gradient, called the Blood Hydrostatic Pressure (BHP) inside the glomerular capillaries.

The Proximal Convoluted Tubule (PCT) reabsorbs a greater variety of chemicals than any other part of the nephron because the epithelial cells in PCT possess microvilli.

Continuous Capillaries and Fenestrated Capillaries