Unit 3.4 Water

1. What are the functions of the urinary system? Eliminates organic waste Regulates plasma ion levels Regulates blood volume and blood pressure Adjusts for water loss Stabilizes blood pH Controls extracellular fluid volume and composition Conserve nutrients

2. What are the major organs of the urinary system? Kidney filters blood and forms urine Ureters carries urine to the urinary bladder Urinary bladder stores the urine until the body is ready to release it Urethra carries urine out of the body

3. What is the general structure of the kidney and how does this structure relate to kidney function? The kidneys receive blood through the renal artery, process it, and return the processed blood to the body through the renal vein. The kidneys also make a protein (BMP-7) that stimulates bone growth. The renal capsule is a membrane that protects the organ. The cortex is the lightly colored outer region and the medulla is the darker colored inner region. The renal pelvis collects the urine that has formed and directs it into the ureter.

4. How does the kidney form urine? The kidneys filter 20% of the plasma and non-cell parts of blood, reabsorbing the components the body needs back into the blood and secreting the unwanted portions. Excretion of dissolved solutes Metabolic waste Urea Creatinine Uric acid Excess ions

5. What is the relationship between blood and urine? The nephron is the basic filtering unit of the kidney and there are about a million of them in each kidney. They filter every bit of blood about 20- 25 times per day! The renal corpuscle is composed of Glomerulus Knot of interconnected capillaries with a spherical shape Bowman’s capsule Encloses glomerulus with squamous epithelium Afferent arteriole Blood supply to glomerulus Efferent arteriole Blood drainage from glomerulus

6. What is the function of the nephron? Production of filtrate glomerulus Reabsorption of nutrients PCT Reabsorption of water and ions DCT, Collecting duct Unwanted materials (ions, small molecules, waste products, extra fluids) turn into filtrate (urine) in the nephrons and leave the body. No red blood cells get filtered out, so there should never be blood in the urine

7. How does filtration in the nephron help maintain a fluid and electrolyte balance in the body? Blood undergoes glomerular filtration where it gets filtered under pressure in the glomerulus (capillaries surrounded by Bowman’s capsule). The filtrate becomes urine (made of excess fluids and unneeded substances) and passes into the proximal tube.

7. How does secretion in the nephron help maintain a fluid and electrolyte balance in the body? Waste substances like ammonia, ions (H˖, K˖ & bicarbonate ion), urea, creatinine, and certain drugs move into the distal and collecting tubules for removal from the body. Secretion is the opposite of reabsorption, moving substances out of the blood and turning them into urine. Secretion helps maintain pH balance by removing excess ions.

7. How does reabsorption in the nephron help maintain a fluid and electrolyte balance in the body? Occurs in: PCT - reabsorbs 65% of filtered Na ions, 2/3 of water, most other stuff Loop of Henle - reabsorbs 25 % of filtered Na. Distal tubule - reabsorbs 8 % of filtered Na. Collecting duct - reabsorbs the remaining 2 % only if the hormone aldosterone is present. Reabsorption moves substances back into the blood. Small molecules like glucose, amino acids, vitamin C, and ions (K+, Ca2+, Cl- & Na+) get grabbed by transporter proteins (located in the PCT) and reabsorbed out of the filtrate. Water is reabsorbed through osmosis. The reabsorption of sodium controls the reabsorption of most other substances (including water). The higher the concentration of a molecule & the slower the rate of flow, the more that is reabsorbed.

8. How do the hormones ADH and aldosterone affect the nephron and the body’s overall water balance? BOTH ALDOSTERONE Released by the pituitary gland Increases permeability of collecting tubule to water Causes constriction of arterioles Stimulates thirst Alcohol inhibits ADH resulting in an increase in urine output   Act on Distal Convoluted Tubule Increase water reabsorption Increase blood volume Increase blood pressure Decrease urine volume Stimulated by humoral factors Released by adrenal cortex Regulates salt content of blood, especially Na+ and K+ Increases reabsorption of Na+ and K+ As Na+ is reabsorbed, water follows passively

How the amount of water is controlled in the body:

9. What is urinalysis? Urinalysis measures the products excreted from the body via urine & can be used to detect many different diseases in the body

10. How can the composition of urine provide clues about problems in other human body systems? TEST NORMAL POSITIVE RESULTS INDICATE LEUKOCYTES Negative Infection, Allergy NITRITE Gram-negative bacteria PROTEIN Renal inflammation, Allergy GLUCOSE Diabetes, Allergy KETONES Energy from fats, not carbohydrates UROBILINOGEN Compromised conjugation of bile BILIRUBIN Hemoglobin destruction BLOOD Infection, Hypertension, Menses HEMOGLOBIN Cell damage-oxidation, Allergy