B6 The Excretry System Review

Question 1

What is the role of the excretory system?

Answer 1

-Regulates the volume and composition of bodily fluids by removing waste and returning needed substances to the body for reuse

Question 2

Describe kidneys

Answer 2

-Contain nephrons
-release urine into the ureters
-urine is moved by peristalsis to the urinary bladder
-urine release is controlled by a voluntary and involuntary sphincter

Question 3

What are nephrons?

Answer 3

-Tubule system where wastes are collected and excreted
-closely connected to the blood supply

Question 4

What are the 3 processes of nephrons?

Answer 4

1. Filtration: occurs at the glomerulus
2. Reabsorption: materials moving from the nephron back into the blood
3. Secretion: materials moving from the blood into the nephron

Question 5

Describe filtration in the glomerulus

Answer 5

-Glomerulus is a high pressure capillary bed
-all materials in plasma expect blood cells and proteins are filtered
-porous capillaries
-filtration depends on permeability of capillaries and blood pressure
-filtrate: material filtered into the nephron from plasma (chemical composition is similar to plasma minus blood cells and protein)

Question 6

Describe Reabsorbtion

Answer 6

~65% of filtrate passing through the proximal tubule is reabsorbed
-proximal tubule has many mitochondria (make ATP)
-active transport of Na+, glucose and other solutes into the blood
- (-) charged ions move passively, attracted by electric charge
-water follows by osmosis

Question 7

What is the loop of henle? (re-absorption)

Answer 7

-Reabsorbs water and ions from filtrate
-descending loop is permeable to water, so at the bottom of the limb Na+ concentration is the highest
-ascending loop is impermeable to water and permeable to solutes
-Na+ diffuses into the blood passively then by active transport

Question 8

What is the distal tubule? (Reabsorption)

Answer 8

-Passive reabsorption of negative ions

Question 9

What is the collecting duct? (Reabsorbtion)

Answer 9

-Water is reabsorbed (osmosis)

Question 10

Describe secretion

Answer 10

-Occurs primarily in the distal tubule
-K+ ions are actively secreted into the distal tubule from capillaries
-H+ is secreted to maintain Ph
-other substances not part of the body such as drugs are secreted as well

Question 11

What are osmoreceptors?

Answer 11

-Cells sensitive to osmotic (water) pressure
-located in the hypothalamus (brain)
-send impulses to pituitary gland to release ADH

Question 12

What is ADH?

Answer 12

-Antidiuretic hormone
-increases the permeability of the distal tubule and the collecting duct to water
-allows more water to be reabsorbed
-travels through the blood to the kidney

Question 13

What happens if blood plasma concentration increases? (Water regulation)

Answer 13

-Osmoreceptors signal ADH to be released which allows more water to be reabsorbed
-decreased water in urine

Question 14

What happens if blood plasma concentration decreases? (water regulation)

Answer 14

-Osmoreceptors stop or prevent the release of ADH which allows more water to be excreted in urine
-solutes are concentrated in the blood

Question 15

What is diabetes insipidus?

Answer 15

-ADH is insufficient and individuals urinate often, thirst is high and dehydration can occur

Question 16

Describe aldosterone

Answer 16

-Stimulates Reabsorbtion of Na+ from the collecting ducts and distal tubules
-stimulates the secretion of K+ into the distal tubules and collecting ducts if K+ concentration in the blood is to high
-produced in the adrenal cortex (lies outside the kidney)
-Reabsorbtion of Na+ is followed passively by chloride ions and water
-aldosterone has a net affect of retaining both salt and water

Question 17

What is juxtaglomerulus apparatus (JGA)?

Answer 17

-Found near the glomerulus
-contains blood pressure receptors which detect low blood pressure
-releases renin

Question 18

What is renin?

Answer 18

-Enzyme which converts angiotensinogin (inactive) into angiotensin (active)

Question 19

What is angiotensin?

Answer 19

-Causes constriction of blood vessels (blood pressure increases)
-initiates the release of aldosterone (causes fluid levels to increase)

Question 20

Describe dialysis

Answer 20

-Diffusion of dissolved substances through a semi-permeable membrane
-hemodialysis: utilizes an artificial membrane in an external device that is connected to an artery and a vein in a persons arm
-peritoneal dialysis: utilizes the lining of the intestines called peritoneum as the dialysis membrane