Excretory system

The excretory system is a biological system that removes excess, unnecessary or dangerous materials from an organism. It is responsible for the elimination of oxygen waste products of metabolism as well as other nitrogeneous materials. Since the normal operation of most biological systems creates waste, the excretory system is not necessarily distinct from other systems. Instead, it often represents the various excretory processes of several different systems.

Component organs

Skin

The skin is another part of the excretory system: it releases sweat, which helps cool the body and regulate the concentration of salt. The salt helps the water evaporate, cooling off the skin.

liver

The liver is an organ of the digestive system. It also helps in excreting wastes from the body in a variety of processes. Laboratory analysis reveals a high concentration of a small organelle called a peroxisome, responsible for breakdown of several toxic substances. It also takes in nitrogenous wastes and converts them to urea to reduce their toxicity.

The liver absorbs drugs and other poisonous substances in the blood and changes their chemical structure to make them less toxic and easier to digest. This waste product is called bile and is excreted to the digestive tract, facilitating digestion of fats while also disposing of waste. It is a highly metabolically active organ. The liver is also an erythropoetic organ in newts.

Kidneys

The key 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, though they also regulate blood pressure in a process called osmoregulation and also assist with the production of red blood cells.

Ureter

In human anatomy, the ureters are muscular ducts that propel urine from the kidneys to the urinary bladder. In the adult, the ureters are usually 25–30 cm (10–12 in) long.

In 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. The backflow of urine is prevented by valves known as ureterovesical valves. In the female, the ureters pass through the mesometrium on the way to the urinary bladder.

Urinary Bladder

In anatomy, 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.

Embryologically, 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.

Urethra

In anatomy, the urethra (from Greek οὐρήθρα - 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.

The external urethral sphincter is a striated muscle that allows voluntary control over urine

Secretion

Secretion is the process of producing a substance from the cells and fluids within a gland or organ and discharging it.

References

CLC Biology