The Kidney

Question 1

What is the functional unit of the kidney?

Answer 1

The nephron, which is the tube system spanning the renal cortex and medulla of the kidney; there are approximately 1 million nephrons in the human kidney; it consists of a tubule and associated vascular component

Question 2

What are renal pyramids?

Answer 2

divisions of the medulla in larger mammals

Question 3

What is the function of the renal pelvis?

Answer 3

Drainage system in the centre of the kidney; connecting ducts fuse to form the renal pelvis

Question 4

What is the function of teh nephron and what are the three basic processes?

Answer 4

Responsible for the formation of urine; 1. glomerular filtration; tubular reabsorption; tubular secretion

Question 5

What is glomerular filtration?

Answer 5

First step in urine filtration; separates the plasma fraction of the blood; the driving force of separation is hydrostatic pressure; small plasma solutes, such as waste products or useful molecules pass through, but no cells enter the ultrafiltrate; also, unless blood pressure is very high, very few proteins will travel into the ultrafiltrate

Question 6

What are the forces are involved in glomerular filtration?

Answer 6

Glomerular capillary blood pressure (higher pressure in the blood, so it wants to move out into the nephron); plasma colloid osmotic pressure (high concentration of proteins wants to pull water back into the blood??); Bowman’s capsule hydrostatic pressure (fluid in the glomerulus pushes back on the fluid trying to exit the capillaries);

Question 7

What is the purpose of the proximal convoluted tubule?

Answer 7

Reabsorption of 65% of filtered water, 67% of filtered sodium, and glucose and amino acids; secretion of protons for acid/base regulation, and organic molecules

Question 8

How does glucose go from the primary urine into the blood?

Answer 8

Through the proximal convoluted tubule; there exists glucose/sodium symporter which helps glucose diffuse into blood (lower glucose conc in blood than primary urine)

Question 9

What is renal threshold?

Answer 9

The point where proximal convoluted tubule glucose-sodium symporters are saturated, and no more glucose can be reabsorbed into the blood, so it starts to appear in the urine

Question 10

What is the purpose of the distal convoluted tubule?

Answer 10

To regulate Na and K in the blood

Question 11

How is sodium transport regulated in the DCT?

Answer 11

Controlled by aldosterone

Question 12

How is permeability to water controlled in the DCT?

Answer 12

Controlled by antidiuretic hormone (ADH)

Question 13

How does the collecting duct decide whether water should be retained or expelled?

Answer 13

Antidiuretic hormone will be released in the case of the dehydration; if water should be expelled, no hormones will act upon the appropriate receptors and thus water will be expelled

Question 14

What roll does vasopressin play in the nephron?

Answer 14

Changes the permeability of the nephron to water; if one is dehydrated, the collecting duct must be permeable to water so water can enter into the medulla; if one is hydrated the water should stay in the collecting duct to be excreted, so therefore the collecting duct becomes impermeable to water

Question 15

What is the danger of ammonium in the body?

Answer 15

Affects intracellular pH; also substitutes for K+ in Na/K ATPase activity; uncouples oxidative phosphorylation by abolshing the proton gradient across the inner mitochondrial membrane; also affects membrane potential; also increases glutamate synthesis, which is a neurotransmitter, and can have several effects on the CNS

Question 16

How is ammonia excreted in ammonotelic animals?

Answer 16

In invertebrates it diffuses out of the body into surrounding water; NH3 is membrane permeable and NH4 is membrane impermeable…?; in fish, it is excreted out of the gills and a little from the kidneys; not all aquatic animals excrete ammonia

Question 17

How do urecotelic animals excrete ammonia?

Answer 17

By combining it with bicarbonate into urea; less toxic than ammonia, and less soluble, so it can be excreted using smaller amounts of water

Question 18

How do uricotelic animals excrete ammonia?

Answer 18

It is formed into uric acid, which precipitates and can be excreted with very little water; non-toxic but it requires a lot of energy; good for animals with limited availability of water

Question 19

What produces the osmotic gradient?

Answer 19

Loop of henle

Question 20

Know that the cortical nephron has a short loop of henle and does not go deep into the medulla; contributes only slightly to formation of primary urine

Answer 20

Ye

Question 21

Know what we focused on is the juxtamedullary nephron

Answer 21

Ye

Question 22

What is the renal corpuscle?

Answer 22

Glomerulus and glimerular capsule

Question 23

How does urea contribute to the osmotic gradient?

Answer 23

Build up in the collecting duct and then leaks out and goes into loop of henle (to bring more water in?)

Question 24

What kind of exchange is the vasa recta?

Answer 24

Countercurrent–maintains osmotic gradient

Question 25

How is permeability regulated in the collecting duct and distal tubule?

Answer 25

ADH

Question 26

How do metenephridia work and what to they do?

Answer 26

Function is osmoregulation and nitrogenous waste excretion; filter coelemic fluid and take small salutes and waste; tubules reabsorb NaCl and other solutes through active transport

Question 27

Permeability of Nh3 and NH4

Answer 27

NH3–membrane permeable

NH4–membrane impermeable

Question 28

What is active secretion and who is it used by?

Answer 28

• Used by invertebrates
○ Instrad of using energy given by pump of heart, use active movement of ions across the nephron
○ This movement forces water ito this organ
○ For open circulatory systems?

Question 29

What do malphigian tubules produce?

Answer 29

Hypo-osmotic urine