Physio Lecture 21 (Final Exam)

Front 1

What are at least six different functions of the kidney?

Back 1

Regulation of : fluid volume, osmolarity, ion concentration, pH, production of hormones, excretion of metabolic wastes and foreign substances

Front 2

Why is the kidney considered an important homeostatic organ?

Back 2

The kidney helps to tightly regulate the blood volume and osmolarity of the blood.

Front 3

Can a person survive with only one kidney?

Back 3

yes

Front 4

Can a person survive without kidneys?

Back 4

A person will die within 2 weeks (or less) of lose of both kidneys without dialysis.

Front 5

What is micturition.

Back 5

Micturation is the clinical term for urination.

Front 6

Approximately what volume of urine is produced/day?

Back 6

The minimum "obligatory" production of urine is 400ml,
but normally about 1-2L of urine per day are produced.

Front 7

What type of neuron stimulates contraction of the urinary bladder?

Back 7

Parasympathetic neurons activate the detrusor muscle of the bladder and relaxation of the internal urethral sphincter.

Front 8

Is there a somatic neuron involved in the release of urine?

Back 8

A somatic neuron (under voluntary control) relaxes to opens the external urethral sphincter

Front 9

About how many nephrons are found in each kidney?

Back 9

About 1 million nephrons are in each kidney.

Front 10

What are the parts of a nephron?

Back 10

The parts of a nephron include: Bowman's capsule, the
proximal convoluted tubule, the descending limb of the Loop of Henle, the ascending limb of the Loop of Henle, the distal convoluted tubules, and the collecting duct.

Front 11

Where does filtration occur?

Back 11

Filtration occurs between the glomerulus
and Bowman's capsule.

Front 12

What portion of the blood is filtered by the nephrons.

Back 12

About 20% of the blood directed to the kidney's is filtered by the nephrons.

Front 13

What is the composition of the
filtrate when it enters the proximal tubule?

Back 13

The filtrate has the same composition as plasma without the proteins.

Front 14

What is the average volume of filtrate formed/day? What % of this is reabsorbed? (hint: compare with volume of urine formed)

Back 14

About 180L of filtrate are formed each day. About 99% of this is reabsorbed

Front 15

How is the glomerular filtration rate (GFR) regulated?

Back 15

GFR can be regulated by vasoconstriction (sympathetic innervation) or vasodilation (absence of sympathetic innervation) of the afferent arteriole

Front 16

What is the effect of the sympathetic nervous
system on the afferent arterioles of the glomeruli? Sympathetic effect on the GFR?

Back 16

vasoconstriction or vasodilation of the efferent arteriole will affect GFR. With sympathetic innervation of the afferent arteriole, the blood flow to the glomeruli will decrease, this will decrease the hydrostatic pressure in the glomerulus and therefore decrease the GFR

Front 17

What two capillary networks are associated with each nephron. Where are they?
.

Back 17

The two capillary networks are the glomerulus, and the peritubular capillary bed (which includes the vasa recta). The glomerulus in surrounded by Bowman's capsule, and the peritubular capillary bed surrounds the entire nephron

Front 18

At what portion of the nephron is most of the filtrate reabsorbed?

Back 18

Most of the reabsorption of filtrates occurs in the proximal convoluted tubule

Front 19

How does reabsorption occur?

Back 19

Active transport occurs
with Na+, glucose, and amino acids (which requires ATP). Passive transport occurs with Cl- and Urea.
And water moves via osmosis.

Front 20

What % of H2O reabsorption occurs before the distal
convoluted tubule? Is this amount obligatory?

Back 20

85% of H2O reabsorption occurs before the distal convoluted tubule. And yes, this amount is always reabsorbed (is obligatory) regardless of the state of hydration of the body.

Front 21

What is the Countercurrent Multiplier System? Why is this system unique?

Back 21

It is the system produced by the nephrons (more specifically the Loop of Henle part of the nephrons) which, due the flow of ultrafiltrate in counter directions and differential movement of molecules and
permeabilities of molecules along the tubule, allows for the creation of a hyperosmotic interstitial fluid environment. This hyperosmotic interstitial fluid allows for almost complete recovery of water (~99
%) by passive diffusion back into the body. It is unique because this is the only area of the body in which osmolality is changed and tolerated by cells (the cells do not creanate due to the hyperosmotic condition).

Front 22

How does the Countercurrent Muliplier System work?

Back 22

The countercurrent flow and proximity of the descending and ascending limbs of the Loop of Henle interact to cause the osmolarity to build in the medulla. Salt pumped in the thick ascending part raises osmolarity around the descending limb, causing more water to diffuse out of the
filtrate. Within the vasa recta, salt enters the vessels and again water follows, so that both salts and water are continually moved from the tubules to the interstitial fluid and into the blood stream. All the fluids transiently experience an increase in osmolarity within the depths of the medulla, but by the time the blood vessels exit the kidneys, the osmolarity is returned to normal (0.3 Osm or 300mosm).

Front 23

Ureter

Back 23

A duct that transmits urine from the kidney to the bladder

Front 24

Urethra

Back 24

A tube that carries urine from the bladder to outside of the body

Front 25

Nephron

Back 25

Functional unit of the kidney that is responsible for forming urine, close to 1 million nephrons per kidney, consists of interrelated vascular and tubular component, smallest unit that can form urine, contains associated blood vessels, glomerular capsule, proximal convoluted tubule, loop of henle, distal convoluted tubule and collecting duct

Front 26

Bowman’s Capsule (Glomerulus)

Back 26

A ball like tuft of capillaries in the kidney’s nephron that filters water and solute from the blood as the first step in urine formation, combined form the renal corpuscle, is the place that glomerular filtration occurs, is considered the first capillary bed, only place where blood from plasma can enter the nephron

Front 27

Proximal Convoluted Tubule

Back 27

Extends between bowman’s capsule and the Loop of Henle in the kidney’s nephron, reabsorption of salt and 33% of water is absorbed here, increases in osmolarity, H+ secretion occurs here and reabsoption of HCO3

Front 28

Loop of Henle

Back 28

Hairpin loop that extends between the proximal and distal tubule of the kidney’s nephron, contains large portions of cholesterol that repel water

Front 29

Distal Convoluted Tubule

Back 29

Extends between the loop of Henle and the collecting duct in the kidney’s nephron, decreases in osmolarity, 85% of water is reabsorbed by the time it reaches here with help from the countercurrent multiplier system,

Front 30

Collecting Duct

Back 30

Last portion of the tubule in the kidney’s nephron where the distal tubule empties into and then empties into the renal pelvis, collects from 8 different nephrons

Front 31

Renal Corpuscle

Back 31

The combined complex of the Bowman’s Capsule and the Glomerulus, it is the place that glomerular filtration occurs

Front 32

Glomerular Filtration/Ultrafiltration

Back 32

Filtration of a protein-free plasma from the glomerular capillaries into the tubular component of the kidney’s nephron as the first step in urine formation, Fluid that enters glomerular capsule whose filtration was driven by blood pressure, blood under pressure forces plasma (filtered blood) into bowmans capsule, this is then called glomerular filtrate and contains electrolytes and water but no large proteins

Front 33

GFR (Glomerular Filtration Rate)

Back 33

The rate at which glomerular filtrate is formed, volume of filtrate produced by both kidneys/min, average is 115 mL/min for women and 125 mL/min in men, 180L/day (45 gallons), major control of this rate comes from the changing of diameter of the afferent arteriole

Front 34

Afferent Arteriole

Back 34

Vessel that carries blood into the glomerulus of the kidney’s nephron, changing diameter of this is a control of GFR, constriction is due to sympathetic activity

Front 35

Efferent Arteriole

Back 35

The rejoining of glomerular capillaries through which blood that was not filtered into the tubular component leaves the glomerulus

Front 36

Obligatory Water Loss

Back 36

The minimum amount of urine eliminated daily necessary to excrete metabolic wastes, 400 ml/day, need to eliminate this waste so it doesn’t become toxic in our blood

Front 37

Reabsorption

Back 37

A highly selective process of the return of essential materials that have been filtered that are returned to the blood, 99% of water, 99.5% of Na, 100% of glucose, 50% urea, 0% phenol, occurs passively and actively (only active transports are Na, Cl, and K), average 124 ml/min get reabsorbed of the 125 ml/min filtered, 85% of filtered H20 and salts are reabsorbed early in tubule system, and the remaining 15% is reabsorbed variably depending on level of hydration and release of hormones, Neither HCO or H can be reabsorbed in their ionic forms they must be converted back by carbonic acid

Front 38

Descending Loop of Henle

Back 38

Part of the Loop of Henle that plunges from the cortex into the medulla, most water osmotically moved out

Front 39

Ascending Loop of Henle

Back 39

Part of the Loop of Henle that traverses back up in to the cortex and returns to the glomerular region of the nephron, Na and Cl and some K reabsorbed here into the vasa recta by Na K Cl pumps, water movement is prevented due to cholesterol

Front 40

Countercurrent Multiplier System

Back 40

As water moves thru PCT only 33% water is reabsorbed thru osmosis, osmotic gradient is formed to draw water back into the body, due to the loop of henle there is a current that increases as osmolarity because water will move out, water is only thing that can move out, 300-1400 mosm as you go down loop of henle

Front 41

Urea

Back 41

Waste product from the breakdown of protein, Contributes to the high osmolarity in the medulla, this deep region is permeable to urea and transports it, indirectly linked to active Na reabsorption, only 50% of filtered urea is passively reabsorbed in a normal person

Front 42

Vasa Recta

Back 42

Able to absorb H20 and salt, loop just inside the loop of Henle that helps with the reabsorbing of the lost nutrients from the osmolarity of ascending and descending loops, Na K Cl pumps (ascending) that pump them into the bloodstreamd into Vasa recta and then becomes diluted as water is absorbed on other side (descending)