Ch 25 terms

Anuria

absence of urine produced; production of 50 mL or less per day

aquaporin

protein-forming water channels through the lipid bilayer of the cell; allows water to cross; activation in the collecting ducts is under the control of ADH

Bowman’s capsule

cup-shaped sack lined by a simple squamous epithelium (parietal surface) and specialized cells called podocytes (visceral surface) that participate in the filtration process; receives the filtrate which then passes on to the PCTs

calyces

cup-like structures receiving urine from the collecting ducts where it passes on to the renal pelvis and ureter

cortical nephrons

nephrons with loops of Henle that do not extend into the renal medulla

detrusor muscle

smooth muscle in the bladder wall; fibers run in all directions to reduce the size of the organ when emptying it of urine

diuretic

compound that increases urine output, leading to decreased water conservation

external urinary sphincter

skeletal muscle; must be relaxed consciously to void urine

glomerular filtration rate (GFR)

rate of renal filtration

glycosuria

presence of glucose in the urine; caused by high blood glucose levels that exceed the ability of the kidneys to reabsorb the glucose; usually the result of untreated or poorly controlled diabetes mellitus

incontinence

loss of ability to control micturition

juxtaglomerular apparatus (JGA)

located at the juncture of the DCT and the afferent and efferent arterioles of the glomerulus; plays a role in the regulation of renal blood flow and GFR

loop of Henle

descending and ascending portions between the proximal and distal convoluted tubules; those of cortical nephrons do not extend into the medulla, whereas those of juxtamedullary nephrons do extend into the medulla

medulla

inner region of kidney containing the renal pyramids

micturition

also called urination or voiding

nephrons

functional units of the kidney that carry out all filtration and modification to produce urine; consist of renal corpuscles, proximal and distal convoluted tubules, and descending and ascending loops of Henle; drain into collecting ducts

oliguria

below normal urine production of 400–500 mL/day

polyuria

urine production in excess of 2.5 L/day; may be caused by diabetes insipidus, diabetes mellitus, or excessive use of diuretics

renin

enzyme produced by juxtaglomerular cells in response to decreased blood pressure or sympathetic nervous activity; catalyzes the conversion of angiotensinogen into angiotensin I

trigone

area at the base of the bladder marked by the two ureters in the posterior–lateral aspect and the urethral orifice in the anterior aspect oriented like points on a triangle

urethra

transports urine from the bladder to the outside environment

urochrome

heme-derived pigment that imparts the typical yellow color of urine

brush border

formed by microvilli on the surface of certain cuboidal cells; in the kidney it is found in the PCT; increases surface area for absorption in the kidney

fenestrations

small windows through a cell, allowing rapid filtration based on size; formed in such a way as to allow substances to cross through a cell without mixing with cell contents

macula densa

cells found in the part of the DCT forming the JGA; sense Na⁺ concentration in the forming urine