Quiz 8: Functions of the Kidney

bruit

an audible swishing sound produced when the volume of blood or the diameter of the blood vessel changes

calculi

stones in the kidney

continence

the ability to voluntarily control emptying of the bladder or colon

cystitis

a bladder inflammation, most often with infection

elimination

the excretion of waste from the body by the GI tract (as feces) and kidneys (as urine)

external urethral sphincter

skeletal muscle that surrounds the urethra and helps to control the exit of urine

incontinence

the involuntary loss of urine or stool

internal urethral sphincter

smooth detrusor muscle of the bladder neck and elastic tissue that helps control the exit of urine

microalbuminuria

the presence of very small amounts of albumin in the urine that are not measurable with usual urinalysis procedures

nephron

the functional unit of the kidney, forms urine by filtering waste products and water from the blood

nocturnal polyuria

increased urination at night

renal threshold

the point at which the kidney is overwhelmed with glucose and can no longer reabsorb

AKA transport maximum

proteinuria

the presence of protein in the urine

uremia

the buildup of nitrogenous waste products in the blood (azotemia)

urethral meatus

the opening at the endpoint of the urethra

urgency

a sense of a nearly uncontrollable need to urinate

Regulatory function of the kidneys

maintain fluid and electrolyte balance and acid base balance through urine elimination and glomerular filtration, tubular reabsorption, and tubular secretions

by processes: filtration, diffusion, active transport, and osmosis

glomerular filtration

first process in urine formation

- as blood passes from the afferent arteriole into the glomerulus, water, electrolytes, and other particles are filtered across the glomerular membrane into the Bowman capsule to form glomerular filtrate

normal glomerular filtration rate

125 mL/min (~180L/day)

GFR is controlled by:

blood pressure and blood flow

- by selectively constricting and dilating the afferne and efferent arterioles

tubular reabsorption

the second process in urine formation

- keeps normal urine output at 1 to 3 L/day and prevents dehydration

vasopressin

increases tubular permeability to water, allowing water to leave the tube and be reabsorbed into capillaries

increases arteriole constriction which alters blood pressure (which affects the amount of fluid and particles that exit glomerular capillaries)

tubular secretion

third process of urine formation

- allows substances to move from the peritubular capillaries in reverse, across capillary membranes, and into the cells that line the tubules

hormones produced by the kidneys

renin

prostaglandins

erythropoietin

activated vitamin D

renin

aids in blood pressure control

- formed and released when there is a decrease in blood flow, blood volume, or blood pressure through the renal arterioles or when too little sodium is present in kidney blood

aldosterone

increases the reabsorption of sodium in the distal tubule of the nephron

prostaglandins

regulate intrarenal blood flow by vasodilation or vasoconstriction

erythropoietin

produced and released in response to decreased oxygen in the kidney's blood supply

- triggers RBC production in the bone marrow

vitamin D

converted to its active form in the kidney

- activated vitamin D is needed to absorb calcium in the intestinal tract and regulate calcium balance