Exam 4--kidney

Question 1

what do the kidneys do?

Answer 1

• remove nitrogenous waste in the form of urea
• maintain fluid volume in the body
• excrete or maintain salts as needed
• contribute importantly to maintaining blood pH

Question 2

what is the basic functional unit of the renal system

Answer 2

nephron

Question 3

what does the beating of the heart do for the kidneys?

Answer 3

produces a hydrostatic pressure that forces the fluid out of the capillaries in the glomeruli

Question 4

how does the kidney receive blood?

Answer 4

renal artery

Question 5

what drains the kidney?

Answer 5

renal vein

Question 6

how fast do the kidneys receive blood?

Answer 6

• 1200ml/min

- 20-25% of blood flow goes into the kidneys

Question 7

how is the kidney organized?

Answer 7

• a cortex

- a medulla

Question 8

where is the blood from the renal artery delivered to?

Answer 8

the cortical region of the kidney

Question 9

what are the different parts of the nephron?

Answer 9

• glomerulus
• Bowman’s capsule
• the ascending and descending limb
• distal convoluted tubule

Question 10

what does the distal convoluted tubule empty into?

Answer 10

the collecting duct, which is not a part of the nephron

Question 11

where is the glomerulus encapsulated?

Answer 11

in bowman’s capsule (glomerular capsule) and it is made up of epithelial cells called podocytes

Question 12

what is bowman’s capsule made up of?

Answer 12

podocytes

Question 13

what causes the fluid to be forced out of the glomerular capillary?

Answer 13

hydrostatic pressure or blood pressure (55mmHg)
-the gaps between the endothelial cells of the capillary are sufficiently large to permit water ions and small molecules such as glucose and amino acids to pass easily from the blood into Bowman’s capsule–the formed elements and plasma proteins are mostly retained in the capillaries

Question 14

albumin

Answer 14

major protein in blood plasma which remains in the glomerular capillary and creates an osmotic pressure (30mmHg) that permits water to reenter the glomerular capillary from Bowman’s capsule

Question 15

what does the collection of fluid in Bowman’s capsule create?

Answer 15

hydrostatic pressure (15mmHg) which forces water out of the capsule

Question 16

net filtration pressure

Answer 16

10mmHg
[55(30+15)]
causes the net movement of fluids and solutes –ions, glucose, amino acids, and urea from the capillary into the capsule

Question 17

glomerular filtration rate (GFR)

Answer 17

• rate at which fluid moves from the glomerulus into Bowman’s capsule
• normally this is about 125 ml/minute

Question 18

what does the normal function of the kidney require?

Answer 18

that hydrostatic pressure in the glomerulus remain constant

Question 19

myogenic regulation

Answer 19

• relies on the tendency of smooth muscle to contract when stretched
• increases in systematic blood pressure stretch smooth muscles in the renal arteries and arterioles causing them to contract and restrict the diameter of the artery
• this reduces the amount of blood flowing into the kidneys
• thereby reduces blood pressure in the renal arteries to ultimately reduce the pressure in the glomerular capillaries

Question 20

macula densa

Answer 20

• located in the distal convoluted tubule near its junction with the afferent arteriole and Bowman’s capsule help control GFR
• monitor the osmolality of the filtrate in the nephron and release molecules that regulate the degree of constriction of the afferent arterioles
• helps maintain a constant GFR

Question 21

dilution of the afferent renal arteries

Answer 21

increases blood flow and blood pressure in the glomerulus to increase GFR and vice versa

Question 22

juxtaglomerular cells

Answer 22

• modified smooth muscle cells
• regulate blood pressure both in the kidney and systematically
• regulates blood flow to the glomerulus
• located mostly on the afferent arterole
• release renin

Question 23

renin

Answer 23

• released by the juxtaglomerular cells
• an enzyme that leads to vasoconstriction through the production of angiotensin 2
• causes constriction of the efferent arteriole to increase hydrostatic pressure in the glomerulus
• increases the release of aldosterone from the adrenal cortex–increases Na+ resorption from the distal convoluted tubule and increases blood volume

Question 24

where does bowman’s capsule lead to

Answer 24

the proximal convoluted tubule

Question 25

proximal convoluted tubule

Answer 25

- return of water, glucose, amino acids, and ions from the nephron begin returning - this is called resorbtion - about 65% of the Na+ and water is resorbed here - lined by a simple epithelium--apical in the lumen and basilar adjacent to basal lamina

Question 26

how does sodium move into the proximal convoluted tubule

Answer 26

- diffuses down its concentration gradient from the filtrate into the epithelial cells of the convoluted tubule (Na channels) - moves into epithelial cells by a cotransporter

Question 27

Na+ driven cotransporters

Answer 27

when a transport protein on the apical surface of the epithelial cells binds a Na+ ion and a molecule of glucose at the same time which leads to a conformational change in the shape of the molecule so that the Na+ and the glucose are both transported across the epithelial cell membrane into the epithelial cell -amino acids are also cotransported this way

Question 28

paratubular capillaries

Answer 28

- surround the proximal convoluted tubule - after the amino acids and glucose diffuse out through the basilar membranes into the interstitial space they then diffuse into the paratubular capillaries - ion concentrations are low because much of the solutes were forced out of the capillaries in the glomerulus

Question 29

Na/K ATPase

Answer 29

-pump the Na+ out of the epithelial cells across the basilar membrane into the interstitial fluid

Question 30

proximal convoluted tubule--

Answer 30

the descending limb

Question 31

the descending limb

Answer 31

- the epithelial cells contain many aquaporins | - the apical membrane is nearly devoid of ion channels making the membrane nearly impervious to the movement of ions

Question 32

medulla of the kidney

Answer 32

- an ionic gradient is established - the ionic concentration increases as it dips into the medulla because water leaves the descending limb and enters the interstitial space

Question 33

hairpin turn

Answer 33

-the ionic concentration in the filtrate reaches about 1200 milliosmoles

Question 34

the ascending limb

Answer 34

- impermeable to water - permits ions to cross - the ionic concentration of the filtrate falls as it ascends the tubule

Question 35

what are the two hormones the distal convoluted tubule is affected by

Answer 35

- aldosterone | - antidiuretic hormone (ADH)

Question 36

aldosterone

Answer 36

- produced by adrenal cortex regulates the resorbtion of Na+ - affects epithelial cells in the distal convoluted tubule--it induces Na+ channel production and insertion in the apical region of the tubular epithelial cells - increases the synthesis of Na/K Pase in the basolateral membrane - pump Na+ out of the epithelial cells of the distal convoluted tubule and into the interstitial space - the net effect is to transfer Na+ from the tubule into the paratubular capillaries - steroid hormone

Question 37

ADH

Answer 37

- the permeability of the collecting ducts to water is under the control of ADH - released from the posterier pituitary and regulates the incorporation of aquaporins into the epithelial cells in the distal convoluted tubule and in the collecting ducts - little ADH=little water leaves the collecting ducts=dilute urine - great deal of ADH=water leaves the collecting ducts and consequently concentrates the ions that remain in the collecting ducts--concentrated urine is produced

Question 38

cortico-medullary gradient

Answer 38

- extends from the cortex into the medulla of the kidney - 1200milliosmoles deep in the medulla - maintained by the loop of henle and the vasa recta which leads to the movement of ions, h2o, and urea into the ascending and descending help establish the gradient - can't be maintained without the vasa recta

Question 39

vasa recta

Answer 39

- extension of the tubular capillaries that extend deep into the medulla - is little hydrostatic pressure and the blood moves very smoothly - osmolality in the vasa recta is nearly the same as the interstitial fluid

Question 40

urea

Answer 40

- as urine moves through the deep medullary regions, urea reaches equilibrium with the interstitial fluid - water leaves the tubule through aquaporins and the remaining ions are destined to enter the bladder - remains in the tubule until it reaches the deep medullary regions where the tubular epithelial cells are permeable to urea