The Kidney

Question 1

What jobs does the kidney do?

Answer 1

1. Water balance (ECF volume, blood pressure, osmolarity)
2. Ion homeostasis (remove excess Na+)
3. PH balance
4. Excretion of water soluble wastes (nitrogenous waste such as urea)
5. Production of hormones (epinephrine)

Question 2

Main purpose of kidneys

Answer 2

Filter blood every 5-6 min which allows us to intake different food/drinks while maintaining homeostasis.

Question 3

Outer part of the kidney

Answer 3

Cortex

Question 4

Inner part of the kidney

Answer 4

Medulla

Question 5

Functional Unit of the kidney

Answer 5

Nephron

Question 6

These nephrons make up only 20% of the kidney but are primarily responsible for secretion / reabsorption

Answer 6

Juxtamedullary Nephron

Question 7

The capillary beds around juxtamedullary nephrons

Answer 7

Vasa recta

Question 8

The Renal Corpuscle

Answer 8

Glomerulus + Bowman’s Capsule

Question 9

The parts of the nephron (in order)

Answer 9

1. Bowman’s capsule 2. Proximal Convoluted Tubule 3. Loop of Henle (descending, ascending) 4. Distal Convoluted Tubule 5. Collecting Duct

Question 10

Renal Pelvis

Answer 10

Where all the collecting ducts meet to funnel into the ureter, which leads to the bladder

Question 11

Three Main Forms of Nitrous Waste

Answer 11

Ammonia, Urea, Uric acid

Question 12

This determines what kind of nitrous waste you produce

Answer 12

Storage requirements! Ammonia is very caustic, so needs to be diluted; uric acid is very expensive to make, but requires very little water, which is why birds produce.

Question 13

Where does the water in our body come from

Answer 13

Diet (about 30%), derived from metabolism (10%), ingested via liquid (60%)

Question 14

In what ways is liquid from our bodies excreted

Answer 14

Feces (5%), evaporation (35%), urine (60%)

Question 15

Where does a kangaroo rat get most of its water??

Answer 15

Metabolism!!

Question 16

What surrounds any average old nephron

Answer 16

Peritubular Capillaries

Question 17

Three key processes of nephron

Answer 17

Glomerular filtration, Tubular secretion, Tubular reabsorption

Question 18

How much of what is filtered is reabsorbed?

Answer 18

99% or MORE!

Question 19

% Water reabsorbed

Answer 19

99%

Question 20

% glucose reabsorbed

Answer 20

100% or you’re in trouble

Question 21

% sodium reabsorbed

Answer 21

99.5%

Question 22

% urea reabsorbed

Answer 22

44%

Question 23

What does glomerulus do

Answer 23

Creates the filtrate, and it is the ONLY place in nephron that filters; pushed out everything EXCEPT large molecules and blood cells. Water and small molecules pass through fenestrations.

Question 24

How does glomerulus filter

Answer 24

Blood pressure! Anatomy increases blood pressure here, and it is greater than the combined force of osmotic pressure (which would pull liquid back into bloodstream) and fluid pressure in Bowman’s capsule. Net pressure about 10 mm Hg.

Question 25

Journey of molecules from glomerulus to Bowman's Capsule

Answer 25

First push through fenestrations in capillary epithelium, then move through basal lamina, then through slit pores in Bowman's capsule epithelium created by weird Dr. Seuss like cells called 'podocytes'. THREE LAYERS OF FILTRATION!

Question 26

Glomerular Filtration Rate

Answer 26

The volume filtered through the kidneys per unit time, many kinds of hormonal regulations will regulate GFR

Question 27

Autoregulation of GFR

Answer 27

Controlled by constriction / dilation of afferent & efferent arterioles: constrict afferent arteriole and reduce flow to glomerulus, ergo reduce GFR; constrict efferent arteriole and pressure builds up in glomerulus, ergo increase GFR.

Question 28

Myogenic Feedback

Answer 28

Control of GFR via myogenic response, aka smooth muscle in arterioles. If blood flow too high, arterioles constrict, reducing flow. If blood flow too low, arterioles relax, allowing more flow through.

Question 29

Tubuloglomerular Feedback

Answer 29

1. GFR increases. 2. Flow through Loop of Henle increases. 3. Macula densa cells sense this. 4. Paracrine signal (unclear what this is) from macula densa to afferent arterioles. 5. Constriction of afferent arterioles 6. Reduction of GFR

Question 30

What is the difference between filtrate and plasma?

Answer 30

Filtrate is destined to be excreted unless reabsorbed; plasma contains large molecules, blood cells, proteins, etc.

Question 31

What is the difference between filtrate and urine?

Answer 31

Urine WILL be excreted. Filtrate is still undergoing process of secretion and reabsorption. Only becomes urine once leaves collecting duct (point of no return).

Question 32

What the PCT Reclaims

Answer 32

Glucose, amino acids, most ions - and water follows

Question 33

How is everything reclaimed in the PCT?

Answer 33

Symports - and these are usually symports powered by sodium gradient! (Water follows solute, so doesn't need any help)

Question 34

How Sodium is Reclaimed in PCT

Answer 34

ENaC (Epithelial Sodium Channel) on apical membrane takes sodium down gradient into low concentration of cell. Sodium potassium pump then returns to interstitial fluid (where sodium is high).

Question 35

Apical Membrane

Answer 35

The side of the cell that faces the lumen (usually has villi)

Question 36

Basolateral membrane

Answer 36

The side of the cell that does NOT face the lumen but instead faces the bloodstream

Question 37

How Glucose is Reclaimed in PCT

Answer 37

SGLT carrier protein symport takes sodium down gradient and glucose up gradient across apical membrane. The glucose goes into blood down gradient via GLUT. Sodium leaves via pump, as always.

Question 38

Any restrictions on the GLUT transporter?

Answer 38

Yes, transport maximum. If this gets maxed out, reach renal threshold and excrete glucose in urine. Diabetes!

Question 39

Renal Threshold

Answer 39

Point at which saturation of GLUT carrier protein occurs and kidneys begin to excrete glucose

Question 40

Filtration of Glucose

Answer 40

NEVER AFFECTED because no transport proteins. No matter how much glucose, will ALL get filtered. The trouble is with reabsorption in the PCT and transport max of GLUT.

Question 41

Pressure gradient beyond Bowman's capsule

Answer 41

Changes to filter reabsorption: so hydrostatic pressure decreases and colloidal osmotic pressure increases. Net 20 mm Hg pressure to reabsorb.

Question 42

Clearance

Answer 42

A way of determining GFR. If you know that something should be totally excreted, the rate at which it is excreted also tells you the rate at which it is filtered

Question 43

Inulin clearance

Answer 43

Plant-derived molecule that will neither be secreted nor absorbed. So its clearance rate can tell us GFR by proxy

Question 44

Glucose clearance

Answer 44

NO glucose should be cleared (none should be excreted). ALL should be reabsorbed.

Question 45

Urea clearance

Answer 45

Where filtration > excretion, there is net reabsorption. This happens with urea.

Question 46

Penicillin Clearance

Answer 46

When filtration < excretion, there is net secretion (movement from bloodstream into filtrate). This happens with penicillin.

Question 47

Micturition

Answer 47

aka peeing 1. Stretch receptors in bladder fire 2. Parasympathetic neurons fire. This causes the TONIC internal sphincter of bladder to release. 3. Motor neurons STOP firing. This causes the 'voluntary' external sphincter at bottom of urethra to open, as well. 4. Smooth muscle contracts. 5. TALLY HO!

Question 48

The Bladder at Rest

Answer 48

Bladder surrounded by smooth muscle is not stretched. Internal sphincter, controlled by smooth muscle (not voluntary control) is contracted. External sphincter controlled by SKELETAL MUSCLE (ergo voluntary) is also contracted.