1. Unit 3.4
Water

2. 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

3. 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

4. 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.

5. 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

6. 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 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

7. 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

8. 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.

9. 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.

10. 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.

11. 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

12. How the amount of water is controlled in the body:

13. 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

14. 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