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Urinary System(Excretory System)By: Will Ineich, Alvin Santos, Isaac Payne31.1 What are the Basic Functions of the Urinary System?Serves many crucial functions relating to homeostasis

And performs excretion of wastes

Excretion?Blood is filtered to remove water and small dissolved moleculesThen nutrients are reabsorbed from the filtrateRemaining water and dissolved wastes are excreted31.2 Excretion for InvertebratesProtonephridia= the first specialized excretory structure that arose during evolutionStill used by flatwormsRegulates water balanceWhich consists of tubes that branch throughout the bodyEnd in flame cells (single celled bulbs)Named for the cilia that extends into the bulbWater is filtered into the bulbs The continuously beating cilia conduct the fluid through the tubes More waste is added and some nutrients are reabsorbedThen it reaches a pore and leaves through diffusion

cilianucleusflamecellfluideyespottubuleextendedpharynxexcretorypores5Figure: 31-1

Title:The simple excretory system of a flatworm

Caption:Hollow flame cells direct excess water and dissolved wastes into a network of tubes. The beating cilia of the flame cells help circulate the fluid to excretory pores. Nephridia in EarthwormsEarthworms, mollusks, and several others have simple kidney like structures (nephridia)Fluid fills the body cavity (coeluom) and surrounds the organs collecting wastesFlows through the nephrostome that reabsorbs salts and nurtients into the blood Leaves behind water and wastes that is stored in a bladder area of the nephridiumThen waste is excreted through the excretory pores (an opening in the body wall)Each segment of an earthworm has its own nephridia

coelom(containscoelomic fluid)nephridiaintestineventral nerve cordnephrostomeexcretory pore7Figure: 31-2

Title:The excretory system of the earthworm

Caption:This system consists of structures called nephridia, one pair per segment. Coelomic fluid is drawn into the nephrostome, and urine is released through the excretory pore. Each nephridium resembles a vertebrate nephron. 31.3 What are the Functions of Vertebrate Urinary SystemsExcretory systems must eliminate dissolved wastes without losing too much water in the processWater may also still contain nutrientsKidneys collect and absorb extra nutrients from blood and other bodily fluidsAt the same time wastes and dangerous chemicals, to be excreted, are also filtered out

Maintains homeostasis by:Regulating blood levels of ions such as sodium, potassium, chloride, and calciumRegulates water content of bloodMaintains pH of bloodRetains nutrients like glucose and amino acidsSecretes hormones such as erythropoietin which stimulates red cell productionEliminates cellular waste such as urea

31.3 ContinuedUrea is a product of amino acid metabolismDigestive system breaks proteins into amino acidsThose are absorbedSome used for new proteinsOthers lose their amino groups (-NH2) and used for energy or to synthesize new moleculesThe amino groups are released as ammonia (NH3) which is toxicThis travels in blood to the liver where it is converted to urea (far less toxic)31.3 continued again The Urea is then filtered from the blood by the kidneysExcreted in urine (fluid containing water, dissolved wastes, and excess nutrients)Mammals avoid ammonias dilapidating effects by excreting it in waterBut then we lose waterReptiles excrete it in uric acid with little loss of water

1 In cells, amino acids are brokeninto simpler molecules, releasingammonia.NH2CHCOROHammonia(NH3)carried in blood2 In the liver, ammonia is combined with CO2 to produce urea.urea carried in bloodNH2CNH2O3 In the kidneys, urea and otherwater soluble wastes are converted into urine.excreted in urineamino acid12Figure: 31-3

Title:A flow diagram showing the formation and excretion of urea

Caption:Question In some animals, ammonia is not converted to urea but instead circulates in the body until it is excreted. In what kinds of environments would you expect to find such animals?Excretory/Urinary System 31.4What Are the Structures and Functions of the Human Urinary System?

By: Alvin Santos

What Are the Structures and Functions of the Human Urinary System?The Urinary System Consists of the: Kidneys- paired organs located on either side of the spinal column and extending slightly above the waist where blood carrying cellular waste enters to be filtered. Renal Artery- The artery which blood enters each kidney.Renal Vein- The vein which blood exits each kidney. Ureter- Muscular tube through which urine leaves each kidney to reach the bladder. Bladder- Hollow, muscular chamber which collects and stores urine.Muscles contained in the walls of the bladder are capable of considerable expansion.Urine is retained in the bladder by two sphincter muscles located at its base. Urethra- Through this narrow tube, urine exits the body. 1.5 inches long in females and 8 inches long in males.

Renal Artery/VeinUrinary SystemWhat Are the Structures and Functions of the Human Urinary System?Structure of the Kidneys:Each kidney contains a sold outer layer where urine is formed, which consists ofthe renal cortex overlying the renal medulla, and a subdivided inner chamber called the renal pelvis, thatcollects urine and funnels itinto the ureter.

More the one million tiny, Individual filters called Nephrons are pack into the Outer layer of each kidney.

What Are the Structures and Functions of the Human Urinary System?The three major parts of the nephron are the glomerulus, the tubule, and the collecting ducts. With the help of these three structures. Each individual nephron is able to filter the blood and produce urine to be excreted.

What Are the Structures and Functions of the Human Urinary System?GLOMERULUS:Within a cup-shaped portion of the nephron- Bowmans Capsule- the arteriole, which supplies each nephron with blood and branches from the renal artery, branches further into the microscopic capillaries that intertwine in a mass called the glomerulus. Within its water permeable walls, pressure is created through difference in diameter between the larger incoming arteriole and the smaller outgoing arteriole. This process is termed filtration, and the resulting fluid is called filtrate. This fluid collects into the Bowmans Capsule and through the nephron. Blood after passing through theglomerulus is more concentrated.

What Are the Structures and Functions of the Human Urinary System?Tubule:Through the processes of tubular reabsorption, which occurs primarily in the proximal tubule and tubular secretion, which occurs primarily in the distal tubule, the tubule of the nephron will restore needed nutrients and most of the water to the blood to the filtrate in the Bowmans Capsule. This will be done while retaining wastes for elimination, maintaining a balance required for homeostasis.

What Are the Structures and Functions of the Human Urinary System?Loop of Henle/Collecting Ducts:Urine can become concentrated because there is an osmotic concentration gradient of salts and urea in the interstitial fluid that surrounds the loop of Henle and the collecting ducts. As filtrate passes through this area, additional water may leave the filtrate through walls of the collecting ducts, while wastes are left behind. This filtrate, as is passes through the ducts, is now called urine. It is important to produce concentrated urine when water is scarce, and to produce dilute, watery urine when there is excess water in the blood. All this depends on the permeability of the collecting duct to water, which is, in turn, controlled by the amount of antidiuretic hormone.

Loop of Henle Disorders of this system include:Gout, also known as gouty arthritis, is incredibly common and painful. People with gout usually first experience pain in the joint of the big toe.A kidney stone, also known as a renal calculus is a solid concretion or crystal aggregation formed in the kidneys from dietary minerals in the urine.Pyelonephritis is an ascending urinary tract infection that has reached the pyelum or pelvis of the kidney. It can lead to kidney failure and death.15.1 How Do Mammalian Kidneys Help Maintain Homeostasis?The kidneys regulate the water content of the bloodHuman kidneys filter out about half a cup of fluid from blood each minuteWithout reabsorption of water, your body would produce 50 gallons of urine dailyThe amount of water reabsorbed is controlled by an antidiuretic hormone (ADH)23


25Kidneys Release Hormones That Help Regulate Blood Pressure and Oxygen LevelsKidneys produce two hormones that are essential to regulating bloodWhen blood pressure fails, the kidneys release renin into the bloodstreamRenin is an enzyme that speeds up the formation of the second hormone, angiotensinAngiotensin is a protein that causes arteries to constrict, raising blood pressure26In response to low oxygen levels, the kidneys release erythropoietinErythropoietin travels to the bone marrow, where the marrow is stimulated to produce more red blood cellsKidney failure leads to anemia , because the kidneys do not produce enough erythropoietin to make the minimal number of red blood cells

27Mammalian Kidneys are Adapted to Diverse EnvironmentsDifferent types of mammals have different kidney structures depending on the availability of water in their habitatThe longer the Henle, the more concentrated the urine is, which means more water is conservedA loop of Henle is what recycles water, the longer the loop, the less diluted the urine is28http://www.youtube.com/watch?v=guOqyi5lUQQ