The excretory system

THEExcretorysystem

SEE YOUR BODY FROM THE INSIDE

Functions

Kidneys

• Removes wastes from blood • Removes harmful substances From blood • Regulates body fluids • Maintains homeostasis

The human excretory system

• Urea, excess water and excess ions are removed from the blood by the kidneys

• Kidneys produces urine which flows down the pari of tubes called ureters

• Urine flows into the bladder where it is stored 

• Contraction of sphincter muscle keeps the urine in the bladder 

• When the sphincter muscle relaxes, urine flows out of the bladder and out of the body through the urethra

How urea is made in the liver

•Urea is a nitrogenous compound, a waste product of protein metabolism produced in the liver as we are unable to store them, therefore any excess needs to be broken down to urea and excreted

How kidney are made?

Each kidney contains about one million tiny units called nephrons. It is composed of a renal corpuscle and a renal tubule. The renal corpuscle consists of a tuft of capillaries called a glomerulus and a cup-shaped structure called Bowman's capsule. The renal tubule extends from the capsule. The capsule and tubule are connected and are composed of epithelial cells with a lumen

kidney

Each kidney is composed of three sections: (renal) cortex, (renal) medulla (middle part) and (renal) pelvis. Kidneys are surrounded by adipose tissue – capsula adiposa The cortex is where the blood is filtered. The medulla contains the collecting ducts which carry filtrate (filtered substances) to the pelvis. The pelvis is a hollow cavity where urine accumulates and drains into the urether

How the apparatus works

To produce urine, nephrons and collecting ducts carry out three basic functions: glomerular filtration, tubular reabsorption, and tubular secretion. The first step in urine production is glomerular filtration. In this process, water and most of the solutes in blood plasma pass through the wall of glomerular capillaries, first into the glomerular capsule and then into the renal tubule. The product of glomerular filtration is referred to as glomerular filtrate. During tubular reabsorption, cells of the tubule reabsorb almost all water and a variety of solutes from the filtrate as it flows through the renal tubule and collecting duct. These reabsorbed substances are then returned to the blood in the peritubular capillaries and vasa recta. In contrast to absorption, in which new substances enter the body, reabsorption refers to substances that have been removed from the blood being returned to the blood. In the process of tubular secretion, renal tubule and collecting duct actively transport substances from the blood in the peritubular capillaries. Secretion, in this case, refers to the removal of substances from the blood. In contrast, the secretion of hormones or enzymes, for example, refers to cells releasing substances into blood, ducts, and interstitial fluid.

ADH

ADH - anti-diuretic hormone • The reabsorption of water back into the blood (at the medulla) is controlled by the anti-diuretic hormone (ADH) produced by the pituitary gland Vena cava • ADH is produced by the part of the brain that monitors water levels in the blood. • It is then carried in the blood to its target organ - the kidneys. • When the brain detects lower than normal water levels in the blood, ADH is produced. • In the medulla, ADH causes more water to be reabsorbed from the urine back into the blood. This produces a lower volume of more concentrated urine and returns blood water levels to normal. When the brain detects higher than normal water levels in the blood (e.g. from drinking more thannormal), less or no ADH is produced • In the medulla, less water is reabsorbed back into the blood. • This produces a larger volume of dilute urine and returns blood water levels to normal.

What is the renin-angiotensin-aldosterone system (RAAS)?

The renin-angiotensin-aldosterone system (RAAS) is the system of hormones, proteins, enzymes and reactions that regulate your blood pressure and blood volume on a long-term basis.It regulates your blood pressure by increasing sodium (salt) reabsorption, water reabsorption (retention) and vascular tone (the degree to which your blood vessels constrict, or narrow). The RAAS consists of three major substances, including: Renin (an enzyme). Angiotensin II (a hormone). Aldosterone (a hormone). Enzymes are proteins that help trigger chemical reactions in your body. They build some substances and break others down. Hormones are chemicals that coordinate different functions in your body by carrying messages through your blood to your organs, muscles and other tissues. These signals tell your body what to do and when to do it.

Homeostasis

Homeostasis is defined as a self-regulating process by which a living organism can maintain internal stability while adjusting to changing external conditions.The urinary system's function is to remove waste products (in the urine), regulate blood volume, blood pressure and red blood cells and to keep in a steady state. This system is the most powerful regulator of the body's internal environment (the maintenance of homeostasis).

The main organs of the urinary system • Bean-shaped organs in your abdomen that filter blood and remove waste.

What are the kidneys?