The Excretory System

Question 1

Liver

Answer 1

Responsible for excreting many wastes by chemically modifying them and releasing them into bile
Deals with hydrophobic or large wastes

Question 2

Urea

Answer 2

synthesized by the liver

Is a carrier of excess nitrogen resulting from protein breakdown

Question 3

Large Intestine

Answer 3

reabsorbs water and ions from feces

Question 4

Skin

Answer 4

Produces sweat which contains water, ions, and urea (similar to urine)

Question 5

Sweat

Answer 5

Controlled by temperature and level of sympathetic nervous system activity

Question 6

Kidneys

Answer 6

Responsible for the excretion of hydrophilic wastes like urea, sodium, bicarbonate, and water
Essential for the maintenance of constant blood pH

Question 7

Homeostasis

Answer 7

Constancy of physiological variables

Question 8

Three main roles of the kidney

Answer 8

Excretion of hydrophilic wastes
Maintenance of constant solute concentration and constant pH
Maintenance of constant fluid volume (important for blood pressure and cardiac output)

Question 9

Filtration

Answer 9

Passage of pressurized blood over a filter

Cells and proteins remain in the blood while water and small molecules are filtered into the renal tubule

Question 10

Filtrate

Answer 10

Fluid in the renal tubule

Question 11

Selective absorption

Answer 11

Reabsorption of useful items like glucose, water, and amino acids

Question 12

Secretion

Answer 12

the addition of substances to the filtrate

Can increase the rate at which substances are eliminated from the blood

Question 13

Concentration and dilution

Answer 13

selective reabsorption of water to determine whether urine is going to be concentrated or dilute

Question 14

Internal Sphincter

Answer 14

Made of smooth muscle (involuntary)

Question 15

External Sphincter

Answer 15

Made of skeletal muscle (voluntary)

Question 16

ADH

Answer 16

When dehydrated: ADH is released by the posterior pituitary and results in increasing water reabsorption in the distal nephron
When hydrated: ADH is not secreted
A drop in blood pressure can also trigger ADH release

Question 17

Aldosterone

Answer 17

Low BP: aldosterone is released by the adrenal cortex and results in increased reabsorption of sodium by the distal nephron. This results in increased plasma osmolarity, increased thirst and water retention, and increases BP
High BP: aldosterone is not released
Other triggers for the release of aldosterone: low blood osmolarity, low blood volume, angiotenisogen II

Question 18

Countercurrent multiplier

Answer 18

This makes the medulla very salty and this facilitates water reabsorption from the collecting duct. This is how the kidney is capable of making urine with a much higher osmolarity than plasma

Question 19

Vasa Recta

Answer 19

form a loop that helps maintain the high concentration of salt in the medulla
Return to the bloodstream any water that is reabsorbed from the filtrate

Question 20

Juxtaglomerular cells

Answer 20

In response to low BP, they release Renin –> converts Angtiotensinogen to Angiotensin 1 –> converted to Angiotensin II by ACE.

Question 21

Angiotensin II

Answer 21

Baroreceptors that monitor systemic blood pressure
Is a vasoconstrictor and increases blood pressure
It also stimulated the release of aldosterone which helps raise BP by increasing water retention

Question 22

Th cells of the macula densa

Answer 22

Chemoreceptions and monitor filtrate osmolarity in the distal tubule
When filtrate osmolarity decreases, the cells of the macula densa stimulate the JG cells to release Renin
Also cause a direct dilation of the afferent arteriole

Question 23

Carbonic Anhydrase

Answer 23

Catalyzes the conversion of CO2 to carbonic acid

Question 24

Calcitonin

Answer 24

Released by the C cells of the thyroid gland
Released in response to high blood Ca2+ levels
Causes Ca2+ to be removed from blood by deposition in bone, reduced absorption by the gut, excretion in the urine

Question 25

Parathyroid hormone

Answer 25

Released by the parathyroid glands and functions in the opposite way as calcitonin

Question 26

EPO

Answer 26

Released by the kidneys and causes increased synthesis of red blood cells in the bone marrow
It is released in response to low blood oxygen levels