Chapter 19 The Kidneys

Question 1

The kidneys regulate

Answer 1

extracellular fluid volume, bp, and osmolarlarity

maintain ion balance, regulate pH, excrete wastes and foreign substances

participate in endocrine pathways

Question 2

urinary system

Answer 2

composed of 2 kidneys, two ureters, a bladder, and a urethra

Question 3

kidneys

Answer 3

have about 1 million microscopic nephrons

arranged into an outer cortex and an inner medulla

Question 4

Renal blood flow

Answer 4

afferent arteriole - glomerulus - efferent arteriole - peritubular capillaries

vasa recta capillaries dip into the medulla

Question 5

Fluid filters

Answer 5

from the glomerulus into the Bowmans capsule - proximal tubule - the loop of Henle - distal tubule - collecting duct - drains into the renal pelvis

Urine then flows through the ureter to the urinary bladder

Question 6

filtration

Answer 6

the movement of fluid from plasma into Bowmans capsule

allows most components of plasma to enter the tubule

excludes blood cells and almost all plasma proteins

Question 7

reabsorption

Answer 7

movement of filtered materials from tubule to blood

Question 8

secretion

Answer 8

movement of selected molecules from the blood to tubule

Question 9

average urine volume

Answer 9

1.5 L/day

Question 10

osmolarity

Answer 10

varies between 50 - 1200 mOsM

Question 11

solute excreted

Answer 11

= # filtered - # reabsorbed + # secreted

Question 12

how much renal plasma flow filters into the tubule lumen

Answer 12

1/5

Question 13

filtration fraction

Answer 13

percentage of total plasma volume that filters

Question 14

podocytes

Answer 14

specialized cells in the bowman capsule epithelium

they wrap around the glomerular capillaries and create filtration slits

Question 15

mesangial cells

Answer 15

support the glomerular capillaries

Question 16

path of filtered solutes

Answer 16

glomerular capillary endothelium - a basement membrane - podocyte filtration slits - then reaches the lumen of Bowmans capsule

Question 17

hydrostatic pressure in glomerular capillaries

Answer 17

averages 55 mm Hg, favoring filtration

opposing filtration = colloid osmotic pressure = 30 mm Hg

and hydrostatic capsule fluid pressure = 15 mm Hg

the net driving force is 10 mmHg, favoring filtration

can be altered by changing resistance in the afferent and efferent arterioles

Question 18

glomerular filtration rate

Answer 18

(GFR) amount of fluid that filters in Bowman’s capsule per unit time.

Average GFR is 125 mL/min or 180 L / day

Question 19

autoregulation of glomerular filtration

Answer 19

is accomplished by a myogenic response of vascular smooth muscle in response to pressure changes

and tubuloglomerular feedback

Question 20

macula densa cells

Answer 20

when fluid flow through the distal tubule increases it sens a paracrine signal to the afferent arteriole, which constricts

Question 21

reflex control of GFR

Answer 21

mediated through systemic signals such as hormones, and through the autonomic nervous system

Question 22

reabsorption

Answer 22

most takes place in the proximal tubule

finely regulated reabsorption takes place in the more distal segments of the nephron

for passive reabsorption of urea and other solutes; active transport of Na+ and other solutes creates concentration gradients

most involves transepithelial transport; some solutes and water are reabsorbed by the paracellular pathway

Question 23

na+ linked secondary active transport

Answer 23

absorbs glucose, amino acids, ions, and various organic metabolites

Question 24

renal transport

Answer 24

is mediated by membrane proteins and exhibits saturation, specificity, and competition

Question 25

transport maximum

Answer 25

transport rate at saturation

Question 26

renal threshold

Answer 26

plasma concentration at which a substance first appears in the urine

Question 27

peritubular capillaries

Answer 27

reabsorb fluid along their entire length

Question 28

secretion

Answer 28

enhances excretion by removing solutes from the peritubular capillaries

K+, H+, and a variety of organic compounds are secreted

can be slowed