Kidney and Osmoregulation Quiz

Question 1

General Steps of Kidney Filtration Process

Answer 1

-Renal artery brings “unclean” blood to each kidney (from body).
-In the cortex, this blood is filtered (in the glomerulus and bowman’s capsule - forming a fluid called “filtrate”), and essential nutrients are then reabsorbed back into it (in the proximal convoluted tubule).
-In the medulla, water is reabsorbed into the blood (loop of Henle and collecting duct).
-“Clean” blood flows out of the kidney and back to the body through the renal vein.
Urine (urea, toxins, and excess water) collects in the renal pelvis and goes to the urinary bladder (where it is temporarily stored prior to excretion) through tubes called ureters.

Question 2

Explain how the structure of the nephron and its associated blood vessels enable the kidney to carry out its functions.

Answer 2

-Excretion of nitrogenous waste «is a function of the» kidney
-Ultrafiltration in the glomerulus
-glomerulus permeable to smaller molecules
-Basement membrane acts as filter/prevent loss of «large» «proteins» and blood cells
-High «blood» pressure in glomerulus due to larger afferent than efferent arteriole
-«Selective» reabsorption of glucose in proximal convoluted tubule
-Microvilli give large surface area
-Water reabsorbed in descending limb «of loop of Henle» and collecting duct
-Active transport of sodium ions out of ascending limb «from filtrate to medulla»
-Ascending limb is impermeable to water
-Loop of Henle creates solute gradient in medulla
-Distal convoluted tubule adjusts pH
-Collecting duct permeability to water varies due to number of aquaporins (ADH)

Question 3

Ultrafiltration

Answer 3

First process which begins removing wastes from blood. It is the non-specific filtration of blood under extremely high pressure (in Bowman’s capsule of the nephron).

Question 4

How is the structure of the glomerulus/ Bowman’s capsule adapted to its function?

Answer 4

-Wide afferent arteriole (a small branch of renal artery) and narrow efferent arteriole
-Because afferent (coming in) arteriole is much wider than efferent (going out) arteriole, this creates extremely high pressure glomerulus (which forces blood into capsule and facilitates filtration)
-Highly branched inside Bowman’s capsule
-Increases surface area for filtration
-Vessels contain fenestrations
-Allow blood contents to pass through vessel membranes into Bowman’s capsule (open under high pressure)

Question 5

Explain how the structure of the proximal convoluted tubule (PCT) facilitates its function (selective reabsorption).

Answer 5

-Filtrate flows inside the PCT within its lumen (the interior portion of the tube)
-Epithelial cells that line the wall of the PCT contain microvilli, which project into the lumen (to increase surface area for reabsorption)
-The epithelial wall of the PCT is only ONE CELL THICK (decreases diffusion distance and increases diffusion rate) and cells contain mitochondria for active transport
-A network of capillaries (called the peritubular capillary bed) surrounds the PCT for reabsorption

Question 6

General control/ monitoring of blood solute levels

Answer 6

-solute concentration of blood monitored by the hypothalamus
-pituitary gland secretes ADH
n. negative feedback

Question 7

When blood concentration is too high… (hypertonic)

Answer 7

-ADH secreted by the anterior pituitary when solute concentration is high/a person is dehydrated
-collecting duct more permeable to water
-opens aquaporins «in the plasma membrane of collecting duct cells»
f. «more» water reabsorbed by osmosis «into the medulla»
-medulla is hypertonic so water can be reabsorbed from filtrate»
-small volume of urine produced «with ADH»

Question 8

When blood solute concentration is too low.. (hypotonic)

Answer 8

-no /less ADH secreted if «blood» solute concentration is too low
-collecting duct less permeable to water less water reabsorbed/large volume of urine produced/dilute urine produced «with low /no ADH»
-urine becomes more dilute less concentrated / higher volume

Question 9

Blood glucose regulation (liver)

Answer 9

k. insulin causes blood glucose «concentration» to be reduced
l. glucose stored as glycogen in the liver
m. glucagon causes blood glucose «concentration» to be increased

Question 10

Osmoregulators

Answer 10

-Osmoregulators are animals whose internal tissues maintain different solute concentrations than their environment
-Osmoregulation requires more energy to maintain, but it ensures that internal solute concentrations are strictly controlled (they vary less)

Question 11

Osmoregulators Examples

Answer 11

birds, mammals, humans, freshwater fish

Question 12

Osmoconformers

Answer 12

-Osmoconformers are animals whose internal tissues maintain the same solute concentrations as their environment (they are iso-osmotic to their surroundings).
-Osmoconforming requires less energy to maintain internal osmotic conditions, and minimizes water movement in and out of cells, but it is more affected by the environment (and organisms are HIGHLY restricted to where they can live).

Question 13

Examples of Osmoconformers

Answer 13

Sharks, squid, jellyfish, crabs, mussels

Question 14

Composition of Blood in Renal Artery vs. Renal Vein: Urea

Answer 14

-Higher in the renal artery
-Lower in the renal vein
-Urea removed through ultrafiltration and excretion

Question 15

Composition of Blood in the Renal Artery vs. Renal Vein: Oxygen

Answer 15

-Higher in the renal artery
-Lower in the renal vein
-Oxygen used to make ATP for active transport of essential substances (glucose, amino acids) back into blood

Question 16

Composition of Blood in the Renal Artery vs. Renal Vein: Carbon Dioxide

Answer 16

-Lower in the renal artery
-Higher in the renal vein
-Waste product of cell respiration in kidney cells as make ATP for active reabsorption

Question 17

Composition of Blood in the Renal Artery vs. Renal Vein: Glucose

Answer 17

-Higher in the renal artery
-A LITTLE Lower in the renal vein
-Used in cellular respiration in kidney cells to make ATP (but close to the same as all reabsorbed in PCT)

Question 18

Composition of Blood in the Renal Artery vs. Renal Vein: Sodium and Chloride Ions

Answer 18

-Higher in the renal artery
-Lower in the renal vein
-Pumped into medulla (or excess excreted) and diluted if ADH secreted

Question 19

Composition of Blood in the Renal Artery vs. Renal Vein: Water

Answer 19

-Higher in the renal artery
-Lower in the renal vein
-Used to dilute urea (more reabsorbed if ADH secreted)

Question 20

Composition of Blood in the Renal Artery vs. Renal Vein: Drugs/Toxins

Answer 20

-Higher in the renal artery
-Lower in the renal vein
-Excreted in urine

Question 21

Composition of Blood in the Renal Artery vs. Renal Vein: Blood cells, proteins, and platelets

Answer 21

Identical in the renal artery
Identical in the renal vein
Too large to pass through basement membrane during ultrafiltration

Question 22

Outline an adaptation of the kidney to maintain osmolarity in desert animals.

Answer 22

-A longer loop of Henle is an adaptation for water conservation in animals that live in arid (desert) environments

-Example: Kangaroo rats

-Almost all water comes from food they eat (as water is so scarce) and they are nocturnal (to preserve water as well)
-Have VERY LONG loops of Henle (more surface area so more water is reabsorbed rather than excreted in urine).

Question 23

Ammonia

Answer 23

-Produced by: Fish (and most aquatic animals)
-Disadvantages: VERY toxic (must be removed from body quickly and diluted with LARGE amounts of water)
-Why it’s used: Fish live in water so have unlimited supply of water to dilute ammonia and it does not require much energy to make

Question 24

Urea

Answer 24

-Produced by: Mammals, amphibians, sharks
-Disadvantages: Requires some water for dilution and requires more energy to produce than ammonia
-Why it’s used: Urea only toxic at higher levels; kidneys prevent excessive build up.
-Requires some water for dilution but not as much as ammonia (mammals have less access to water than fish); can be stored (short-term) in bladder

Question 25

Uric Acid

Answer 25

-Produced by: Birds, many reptiles, and insects
-Disadvantages: Requires A LOT of energy to produce
-Why it’s used: Insoluble in aqueous solutions (so CAN be stored with reptile and bird embryos in developing eggs - no toxicity of ammonia); requires little to no water for dilution (excreted in concentrated form) and removal from body, so do not need to find water as frequently

Question 26

Malpighian tubes in insects and kidneys carry out…

Answer 26

osmoregulation and removal of nitrogenous waste.

Question 27

Explain how insects excrete nitrogenous wastes.

Answer 27

-Malpighian tubules remove wastes from the hemolymph (fluid analogous to blood), and they CONNECT to the digestive system.
-Branch off intestinal tract in insects.
-At the far ends, they filter salts and ammonia (active transport), and water out of the hemolymph (these then pass INTO the gut)
-Salts, solutes, and water are reabsorbed back into the
hemolymph in the hindgut and ammonia (converted to uric acid) forms a precipitate and combines with undigested food and is excreted with feces via the rectum/ anus.

Question 28

Urinalysis

Answer 28

-Blood cells: Urine should not have blood cells in it (they are too large to fit through the fenestrations in the glomerulus).
-Blood cells indicate infection, kidney malfunction, and/ or bleeding in the renal tubes.
-Glucose: should all be reabsorbed in the PCT
-Excess glucose that is unable to be reabsorbed by PCT indicates diabetes.
-Proteins: are too large to pass through fenestrations in the glomerulus
-Proteins indicate disease, hormonal conditions, or even pregnancy
-Drugs: not naturally found in body

Question 29

Hemodialysis

Answer 29

-Filtering blood through an external apparatus called a dialyzer.
-Dialyzer contains semi-permeable membranes (restricting passage of larger substances) and dialysis fluids called dialysates (to remove wastes and maintain concentration gradients).
-Takes up to 4 hours and can be done up to 3 times per week (short-term solution though; only a few years)

Question 30

Kidney Transplant

Answer 30

-long-term treatment
-Requires close genetic match (and Immunosuppressant drugs)
-Kidney grafted into abdomen and connected to recipient’s vessels (often from family, as can live with only one)