Human Excretory System

Human Excretory SystemDefinition of Excretion Excretion - Excretion is the removal of the metabolic wastes of an organism. Wastes that are removed include carbon dioxide, water, salt, urea and uric acid. All excreted wastes travel at some time in the blood.The excretory system is a passive biological system that removes excess, unnecessary or dangerous materials from an organism, so as to help maintain homeostasis within the organism and prevent damage to the body. It is responsible for the elimination of the waste products of metabolism as well as other liquid and gaseous wastes.

Definition of Excretion Excretory systems are special structures in organisms through which waste products of METABOLISM are rid and the proper balance of water and salts in the blood and other body fluids is maintained at the same time. Defecation is the elimination of undigested material from the body and is a function of the DIGESTIVE SYSTEM.

Organs of the Excretory System

Lungs - removal of excess carbon dioxideLiver - produces urea and uric acid as a by-product of the breakdown of proteinsSkin - removal of excess water, salt, urea and uric acidUrinary System - kidneys filter the blood to form urine, which is excess water, salt, urea and uric acid

Organs of the Excretory System

THE SKIN

Two Layers of the SkinEpidermis - outer protective layer without blood vesselsDermis - inner layer containing blood vessels, sensory nerve endings, sweat and oil glands, hairs, and fat cells

Functions of the SkinExcretion - 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.

Functions of the SkinRegulation 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.

Functions of the SkinProtection 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.

THE URINARY SYSTEM

UrineThe first nitrogenous waste to be formed from the breakdown of protein is ammonia, a highly toxic chemical that is quickly converted by the liver to urea and uric acid. These are less toxic than ammonia and are transported in the blood to the kidneys for excretion in urine. Urine consists of excess water, excess salt, urea and uric acid.

Parts of the Urinary System

Renal Arteries - 2 renal arteries constantly transport blood to the kidneys.Kidneys - 2 kidneys composed of millions of nephrons constantly filter about 170 to 200 litres of blood to produce about 1.5 to 2 litres of urine daily.Renal Veins - 2 renal veins return useful nutrients back into the bloodstream.

Parts of the Urinary System

Ureters - 2 ureters carry urine from the kidneys to the urinary bladder.Urinary Bladder - The urinary bladder temporarily stores urine until it is released from the body.Urethra - The urethra is the tube that carries urine from the urinary bladder to the outside of the body. The outer end of the urethra is controlled by a circular muscle called a sphincter.

Parts of the Urinary SystemKidneysThe primary organs in the excretory system of vertebrates. (See protonephridia system for Platyhelminthes, metanephridia for Annelida, or the Malpighian tubes for insects and terrestrial arthropods.) The kidneys are placed on either side of the spinal column near the lower back. They are primarily responsible for filtering blood by removing nitrogenous wastes from metabolism, salts & other excess minerals and excess water.Parts of the Urinary SystemUreterIn human anatomy, the ureters are muscular ducts that propel urine from the kidneys to the urinary bladder. In the adult, the ureters are usually 2530 cm (1012 in) long.

Parts of the Urinary SystemIn humans, the ureters arise from the renal pelvis on the medial aspect of each kidney before descending towards the bladder on the front of the psoas major muscle. The ureters cross the pelvic brim near the bifurcation of the iliac arteries (which they run over). This "pelviureteric junction" is a common site for the impaction of kidney stones (the other being the uteterovesical valve). The ureters run posteroinferiorly on the lateral walls of the pelvis. They then curve anteriormedially to enter the bladder through the back, at the vesicoureteric junction, running within the wall of the bladder for a few centimeters.

Parts of the Urinary SystemUrinary BladderIn anatomy, your bladder produces 11.9 litters of fluid a day. The urinary bladder is the organ that collects urine excreted by the kidneys prior to disposal by urination. A hollow muscular, and distensible (or elastic) organ, the bladder sits on the pelvic floor. Urine enters the bladder via the ureters and exits via the urethra.

Parts of the Urinary SystemEmbryologically, the bladder is derived from the urogenital sinus and, it is initially continuous with the allantois. In males, the base of the bladder lies between the rectum and the pubic symphysis. It is superior to the prostate, and separated from the rectum by the rectovesical excavation. In females, the bladder sits inferior to the uterus and anterior to the vagina. It is separated from the uterus by the vesicouterine excavation. In infants and young children, the urinary bladder is in the abdomen even when empty.

Parts of the Urinary SystemUrethraIn anatomy, the urethra (from Greek - ourethra) is a tube which connects the urinary bladder to the outside of the body. The urethra has an excretory function in both sexes to pass urine to the outside, and also a reproductive function in the male, as a passage for semen during sexual activity.The external urethral sphincter is a striated muscle that allows voluntary control over urine

Diseases and dysfunctions related to each system.

Disease can affect any of the parts of the closely related urinary and genital systems. Both can be infected or malfunction because of a shortcoming in development.

Kidney Inflammations

Glomerulonephritis is a serious inflammatory disease of the kidneys. It usually is triggered by a prior infection, often by streptococcal bacteria, which inflames the glomeruli, the tiny tufts through which blood is filtered. The inflammation may go away after a few weeks or may slowly destroy all the glomeruli. In the early stages, the inflammation may reduce filtration enough to cause blood to retain some excess fluid, salts, and wastes. Blood pressure might also rise. If the inflammation persists, the glomeruli are destroyed, blood pressure soars, and urine formation may stop. Mechanical means must be taken to cleanse the blood.Kidney InflammationsPyelonephritis is a bacterial infection of the inner portions of the kidneys and the urine. If quickly treated, the infection can be cured. If untreated, however, the infection may scar and eventually destroy kidney tubules, resulting in a need for mechanical cleansing of the blood. Once damaged by a bout of pyelonephritis, the kidneys are easily reinfected.

Kidney InflammationsToxemia of pregnancy is a disorder stemming from other kidney problems experienced by some women in the last half of pregnancy. During a pregnancy, the kidneys must work more than usual. However, a woman entering pregnancy with a kidney disease such as glomerulonephritis may not be able to step up kidney function enough to meet the new demands. In severe cases of toxemia, the fetus may die or have to be aborted to save the mother's life. In lesser cases, however, medical treatment poses little risk to either life. Once a woman develops toxemia, she is likely to develop it again in later pregnancies.

Calculi and Other Urinary Disorders

Calculi and Other Urinary DisordersCalculus disease occurs when certain substances in urine crystallize into compact stones called calculi. A stone may be formed within a kidney and become swept by urine into the ureters and the bladder. It may cause pain, obstruct urine flow, or grow large enough to damage the kidney or bladder. Small calculi may be passed in urine, and large ones can be pulverized without surgery by means of energetic sound waves. Calculi can consist of calcium, urates, cystine, or other crystals. The tendency to form kidney stones sometimes runs in families.

Calculi and Other Urinary DisordersPolycystic disease, an inherited failure of normal kidney development, strikes infants as well as adults. Many fluid-filled cysts spring up throughout the kidneys and cause them to malfunction. Polycystic disease sufferers eventually become uremic.

Calculi and Other Urinary DisordersUremia means "urine in blood." It describes the condition in which the kidneys almost totally fail to operate. The blood then retains the nitrogenous products of protein metabolism instead of having them removed by the kidneys. Also, the concentration of many of the electrolytes, or salts, in the blood rises too high. The breath or perspiration of affected persons smells of urine. Each of the previously mentioned kidney ailments could cause uremia. Artificial kidneys have been developed to cleanse the blood of uremic patients. In some cases, patients with destroyed kidneys can receive a human kidney transplant.