THE URINARY SYSTEM

1. THE URINARY SYSTEM By: Priscilla Mejia Erika Tan JeanaLindo

2. FUNCTIONS • Excretion of Metabolic Wastes • Process: • Kidneys excretes metabolic wastes, which are usually nitrogenous(containing nitrogen) wastes. • In the liver amino acids breakdown, releasing ammonia which combines with carbon dioxide to produce urea • Urea: byproduct of amino acid metabolism. • The liver does this because ammonia is too toxic and bodies excreting just ammonia would have to urinate in large quantities to dilute the toxins. • The function: to remove these toxic byproducts from the blood and eliminate them from the body

3. FUNCTIONS • Preservation of Water-Salt Balance • The principle function of the kidneys is to maintain appropriate water-salt balance of the blood. • Blood volume is associated with the salt balance of the body. Salts have the ability to cause osmosis (diffusion of water) into the blood. The more salts present in blood, the greater the blood volume. • Kidneys maintain appropriate level of ions (electrolytes): • potassium, bicarbonate, calcium in the blood

4. FUNCTIONS • Maintenance of Blood Pressure • Blood pressure: products of cardiac output and peripheral resistance. Kidneys influence these two. • By preserving salt and water balance, the kidneys maintain a normal blood volume • Blood volume: determines heart’s stroke volume and cardiac output • kidneys influence peripheral resistance by producing the enzyme renin, which activates plasma protein andgiotensin(constricts blood vessel, smooth muscle, increasing resistance).

5. FUNCTIONS • Maintenance of Acid –Base Balance • Kidneys regulate • Since Blood pH of a healthy person should be around 7.4, kidneys monitor and control blood pH mainly by excreting hydrogen ions from the blood into the urine while reabsorbing bicarbonate ions and returning them to blood as needed • Urine usually has pH of 6 or lower because our foods usually contain acids

6. FUNCTIONS • Secretion of Hormones • Kidneys help endocrine system in hormone secretion by releasing the enzyme renin whenever their own blood supply decreases. • The kidneys activate angiotensin and secrete the hormone aldosterone (produced by the adrenal cortex) which promotes reabsorption of sodium ions and water by the kidneys. • Whenever the oxygen carrying capacity of the blood is reduced, the kidneys secrete erythropoietin which stimulates red blood cell production • Kidneys also help activate vitamin D from the skin. Vitamin D leads the whole hormone calcitriol which promotes calcium absorption for digestive tract

7. STRUCTURES OF THE URINARY SYSTEM

8. STRUCTURES OF THE URINARY SYSTEM • Kidneys • Each kidney is usually held in place by connective tissue called renal fascia. Masses of adipose tissue stick to each kidney. An injury to the back can dislodge a kidney and produce what is called a floating kidney. • Covered by a tough capsule of fibrous connective tissue called renal capsule. The side of the kidney has a depression called the hilum where a renal artery enters a renal vein and a uterer exits the kidney.

9. ANATOMY OF THE KIDNEY

10. STRUCTURES OF THE URINARY SYSTEM • Ureters • Extend from kidneys to bladder and are small muscular tubes about 25 cm long and 5 mm in diameter • Each descends behind the partial peritoneum from the hilum of a kidney, to enter the bladder posteriorly behind at its interior, inferior surface • The wall of the ureter has 3 layers • Inner layer: mucosa (mucous membrane) • Middle layer: consists of smooth muscle • Outer layer: fibrous coat of connective tissue • Urine enters the bladder at the rate of 1-5 spurts/minute

11. STRUCTURES OF THE URINARY SYSTEM • Urinary Bladder • Function: store urine until its expelled from the body. • Has 3 openings • 2 for the ureters 1 for the urethra • Drains bladder • The trigon: smooth triangular area at the base of the bladder outlined by these 3 openings • Muscle layer of the bladder wall are called detrusor muscle • Wall contains middle layer of circular fiber in 2 layers of longitudinal muscle and it can expand. The transitional epithelium of the mucosa becomes thinner and folds in the mucosa called rugae disappear as the bladder fills and enlarges • After urine enters the bladder, small folds of bladder mucosa act as a wall to prevent backward flow. • Two close sphincters are found where the urethra leaves the bladder • Internal sphincter occurs around the opening to the urethra • External sphincter (inferior to internal sphincter) is composed of skeletal muscle that can be voluntarily controlled • Sphincter: ringlike muscle that normally maintains constriction of a body passage; relaxes as required by normal physiological functioning.

12. STRUCTURES OF THE URINARY SYSTEM • Renal blood supply • Renal artery: large branch of abdominal aorta brings blood into the kidney on the outside of the cavity. Kidneys are said to “float” • Renal vein: drains filtered blood out of the kidney • Kidneys receive up to 20 % of all blood pumped by the heart each minute • Kidney tissues • Under the capsule, kidneys tissue are organized in more or less concentric layers. • Cortex (outer layer) and beneath the cortex is the medulla, several fan-shaped structures compressing a membrane that is folded into conical structures-- renal pyramids which secrete urine at their tips into sac-like structures. • The renal pelvis (inner most layer) carries the urine from the sacs into the ureter.

13. STRUCTURES OF THE URINARY SYSTEM • Nephrons • Microscopic in size, and the kidneys filtering unit • Two parts: • Renal corpuscle • Glomulerus: special kind of capillary bed derived from the arterioles, branching from the renal artery • Glomerular capsule or Bowman’s capsule (double-walled epithelial cup that partially encloses the glomulerus) • Renal tubule

14. ANATOMY OF NEPHRON

15. URINE FORMATION • Glomerular Filtration: • Occurs when whole blood enters the afferent arteriole and glomerulus • Filtration: water and small molecules are pushed from the glomerulus to the inside of the glomerular capsule • Large molecules and formed elements will be unable to push through the capillary wall • So the blood in the glomerulus has 2 portions: • Glomerular Filtrate: • Contains small dissolved molecules in about the same concentration as plasma • Small molecules that escape that are being filtered and the non-filterable components leave the glomerulus through the efferent arteriole • Nephrons in kidneys filter 180 liters of water/a day with salt and sugar • If composition of urine were same as that of the glomerular filtrate, the body would constantly lose water, salts, and nutrients in the urine • DOES NOT HAPPEN TO HEALTHY PEOPLE • The composition of original filtrate is altered significantly as the fluid passes through the remainder of the tubule

16. URINE FORMATION • Glomerular filtrate • It is important to be aware that many small chemicals are freely filtered from the blood • Once in filtrate, chemicals cannot be reabsorbed and will be passed in urine • That’s why urinalysis is able to give history of chemicals recently present in the blood, and detect illegal drug use

17. URINE FORMATION • Tubular reabsorption • Happens as molecules and ions are both passively and actively reabsorbed from the nephron into the blood of the peritubular capillary network • peritubular capillary network: located in the renal tube; tiny blood vessels that travel alongside nephrons and allow reabsorption and secretion between blood and the inner lumen of the nephron • Osmolarity of blood is maintained by plasma proteins and salt being present • Glucose and amino acids return to the blood by the proximal convoluted tubule • Only molecules recognized by carrier proteins built into tubular cell membranes will be actively reabsorbed • Every substance has a maximum rate of transport • Excess in filtrate will appear in urine

18. URINE FORMATION *Example: In untreated diabetes, excess glucose takes place in the blood because of either lack of insulin or abnormal response of insulin receptors • Without function of insulin, glucose can’t be transported into the cells and liver and muscle won’t be able to store the glucose as glycogen • The excess blood glucose is filtered in tubular fluid and then passed through the urine since the kidneys aren’t able to reabsorb it • Those who have untreated diabetes will experience frequent urination and increased thirst because of the increased osmolarity of glycogen in the filtrate compared to blood, which causes less water to be reabsorbed into the peritubular capillary network

19. URINE FORMATION • Filtrate that enters the proximal convoluted tubule is divided into 2 portions: • Reabsorbed components from tubule into blood • Most water • Nutrients • Required salts • Some urea and uric acid • Non-reabsorbed components (continue to pass through nephron and into urine) • Some water • Much nitrogenous waste • Excess salts • Creatinine and urochrome • Molecules not recognized by carriers

20. URINE FORMATION • Tubular Secretion • 2nd way substances can be removed from blood and actively transported into the tubular fluid • Some of these substances: • Hydrogen ions • Potassium ions • Creatinine ions • Drugs like penicillin • By the end, urine will contain: • Substances that have undergone glomerular filtration but have not been reabsorbed • Substances that have undergone tubular secretion

23. Maintaining Homeostasis • The kidneys , under hormonal control, are the key organs for maintaining the chemical homeostasis of blood and other body fluids.

24. Maintaining Homeostasis • Concentration of electrolytes such as Na+ help determine the blood volume because the kidneys push water into the blood or withdraw to bring concentrations of these electrolytes to normal homeostatic ranges. • Important factor in circulation. • The greater the blood volume, the harder the heart will work to pump to blood and the greater the fluid pressure in the arteries.

25. Maintaining Homeostasis • The urinary system when working properly maintains blood chemistry, even if it requires putting it before the needs of the other systems. • Adult body contains: • 23 pints of extracellular fluid (16% of bodyweight) • 6 pints of plasma(4% of bodyweight) • Both of which are similar chemically and along with intracellular fluid help control the movement of water and electrolytes throughout the body. • Important ionized components of intestinal fluid: • Protein • Mg+ • K+ • Cl- • Ca+ • Certain sulfates

26. Maintaining Homeostasis • The renin-angiotensin system • Called into action when toxins in the blood signals low blood pressure in the glomeruli appear. • Specialized kidney cells secrete renin who set off a series of reactions in different organ systems, resulting in the production of the hormone angiotenogenase II, a powerful vasoconstrictor. • Stimulates secretion of the hormone aldosterone from the adrenal cortex which causes Na+ to be reabsorbed from the nephrons into the blood. • Where salt goes water follows, the movement of water into the blood increases blood volume, which helps the effectiveness of the glomerular filtration.

27. Maintaining Homeostasis • Medications for hypertensions act by disrupting the production of an enzyme that catalyzes the crucial reaction in this pathway the produces angiotensin II, which are angiotensin-conversion enzyme inhibitors. • Without angiotensin, the kidneys don’t receive the signal to increase the water content of the blood.

28. Maintaining Homeostasis • Pituitary gland secretes ANH when the hypothalamus senses dehydration, Sodium is reabsorbed by the nephrons but not enough water follows so ANH causes more water to be reabsorbed from the urine , which decreases the amount of urine and helps maintain normal blood pressure and volume. • ANH (atrialnatriuretichoromone)- a polypeptide hormone secreted by heart muscle cells in response to signals from sensory cells in atria hat blood volume is too high • Prevents kidneys from secreting renin • Acts to reduce the water, sodium, adipose, loads on the circulatory system, thereby reducing blood pressure

29. PROBLEMS WITH KIDNEY FUNCTION • The composition of urine changes if: • disease has tampered with body metabolism • Kidney function is abnormal • Urinalysis: • Examination of the physical, chemical, and microscopic properties of the urine • To help determine state of the body • Diabetes, hypertension, and inherited conditions are able to cause progressive renal disease and renal failure • Renal failure can cause patients to go through a kidney transplant operation • Survival rate receives from a relative is 97% • Survival rate received from non-relative is 90% • Must take antirejection medication for the rest of her life • Urinary tracts are particularly common in females because their urethra is much shorter than of males’

31. PROBLEMS WITH KIDNEY FUNCTION • Urethritis: infection that is located in the urethra • Cystitis: infection that invades the urinary bladder • Pyelonephritis: infection that causes the kidneys to be affected • Glomerular damage leads to blockage of the glomeruli • glomerular filtration does not occur or allow large substances to pass through • If the glomeruli are too absorbent, albumin, white blood cells, even red blood cells will appear in urine • Uremia: • glomerular damage is so extensive that more than 2/3 of the nephrons aren’t able to operate • Urea and other wastes come together in the blood • Retention of water and salts is a great concern • Eventually causes edema, fluid accumulation in the body tissues • Will cause an imbalance in the ionic composition of body fluids • Loss of consciousness and to heart failure

32. PROBLEMS WITH KIDNEY FUNCTION • Hemodialysis: when patients have to either use an artificial kidney machine or continuous ambulatory peritoneal dialysis (removes wastes, chemicals, and extra fluid from your body) because of renal failure • In an artificial kidney machine, the patient’s blood is passed through a membranous tube that is in contact with a dialysis solution (dialysate) • Substances that are more concentrated in the blood diffuse into the dialysate • Substances that are more concentrated in the dialysate diffuse into the blood • The dialysate is continuously replaced to maintain favorable concentration gradients • So the artificial kidney can be used to either extract substances (waste products, toxic chemicals and drugs) from the blood or add them into the blood • Dialysis: diffusion of dissolved molecules through a semipermeable natural or synthetic membrane that has pore sizes so that only small molecules are able to pass through

34. REGULATORY FUNCTIONS OF KIDNEYS • Maintain fluid, electrolyte, and acid-base balance of the blood • By keeping this balance within normal limits, kidneys also maintain blood volume and blood pressure • If they fail, either hemodialysis or a kidney transplant is needed Really brief overview of kidney function: http://youtu.be/qdP3zBaDCv0

35. FLUID AND ELECTROLYTE BALANCE • Average adult male body – 60% water by weight • Average adult female body – 50% water by weight; because they generally have more subcutaneous adipose tissue, which has less water • Of the water in human bodies, abt. 60% is intracellular fluid and the rest is tissue fluid, plasma and lymph (extracellular fluid). It is also found in cerebrospinal and synovial fluid.

37. REABSORPTION OF WATER • As salt is reabsorbed, so is water until the osmolarity is the same on both sides of the plasma membrane Somehow we produce hypertonic urine, which is: having the higher osmotic pressure of two solutions • We produce hypertonic urine by way of the loop of Henle and the collecting duct.

38. THE LOOP OF HENLE AND THE COLLECTING DUCT • Loop of Henle has a descending limb that connects with the medulla • and an ascending limb that moves back into the cortex of the kidney • The ascending limb has 2 portions: narrow, thinner walled portion which passively diffuses salt (NaCl) & wide, thick walled portion which actively transports salt into the tissue of the renal medulla • Water does not move out of the ascending limb, however, because it is impermeable to water.

39. Here's an awesome explanation video http://youtu.be/XbI8eY-BeXY

40. THE LOOP OF HENLE AND THE COLLECTING DUCT • Loop of Henle has a descending limb that connects with the medulla • and an ascending limb that moves back into the cortex of the kidney • It is a countercurrent mechanism • The ascending limb has 2 portions: narrow, thinner walled portion which passively diffuses salt (NaCl) & wide, thick walled portion which actively transports salt into the tissue of the renal medulla Water does not move out of the ascending limb, however, because it is impermeable to water. The loop's movement of salt creates a concentration gradient so that water can move along through osmosis. It moves to the descending limb which IS water-permeable. Water then moves out of the descending limb and into the ascending vasa rectaewhich produces the blood to normal osmotic pressure of the body.

41. ANTIDIURECTIC HORMONE (ADH) ADH - produced by hypothalamus Antidiuretic - against a flow of urine If solutes in blood too concentrated (due to lack of water consumption), ADH is produced to lessen urine formation.It does this by increasing water absorption through the opening of aquaporins in the collecting duct. This also raises blood volume and pressure.

42. REABSORPTION OF ELECTROLYTES • Osmolarity determined by concentration of certain electrolytes. • Electrolytes: compounds and molecules that are able to ionize (carry an electrical current) • Common electrolytes in plasma: • Sodium-needed for formation of nerve action potential signal and muscle contraction. Concentration of sodium in blood=best indicator of osmolarity • Potassium-needed for formation of nerve action potential signal and muscle contraction. Low potassium concentration can lead to cardiac arrest • Bicarbonate ion-helps maintain pH of blood • Other ions-calcium&phosphate-bone formation and cellular metabolism-excretion by kidneys regulated by hormones

43. REABSORPTION OF ELECTROLYTES • Kidneys – over 99% of sodium filtered & glomerulus is returned to blood. • Aldosterone-hormone that promotes excretion of potassium and reabsorption of sodium (followed by reabsorption of water) thus inscreasing blood volume & pressure the kidneys trigger the release of aldosterone through a series of secretions and enzymes released when blood volume and pressure is insufficient for glomerular filtration • Atrial Natriuteric Peptide-hormone secreted by atria of heart when blood volume is increased decreases blood volume&pressure by preventing release of aldosterone and promoting excretion of sodium

44. Diuretics • inhibit secretion of ADH • Lower blood pressure as result of lower cardiac output

45. Acid-Base Balance • Alkalosis - blood pH too alkaline (over 7.4) • Acidosis – blood pH too acidic (under 7.4) • Acid-Base Buffer Systems-buffers keep pH around 7.4 by absorbing excess hydrogen/hydroxide. Amino acids can combine w/release hydrogen ions as needed • Respiratory regulation of acid-base balance - increasing respiratory rate provides body w/ rapid way to remove excess free hydrogen ions from blood • Renal (Metabolic) regulation of acid-base balance – reabsorb bicarbonate ions and excrete hydrogen ions as needed to maintain the normal pH of the blood • Ammonia and phosphate buffer hydrogen ions in urine • KIDNEYS' CONTROL OVER pH IS VERY IMPORTANT Video: http://youtu.be/i_pTaTveCCo

46. EFFECTS OF AGING • Kidneys decrease in size and have significantly fewer nephrons • Kidney stones • Improper diet, inadequate fluid intake, and kidney infections • Probability of infections of the urethra, bladder, ureters, and kidneys increase • Enlargement of prostate occurs in males • Lead to urine retention and kidney disease • Cancer of the prostate and bladder are the most common cancers of the urogenital system • Incontinence • Uncontrollable loss of urine • Bladder capacity of an elderly person is less than half of a young adult • Often contains residual urine