Definitions

Kidney

• Either of two glandular organs situated at the back of the abdominal cavity close to the spinal column in vertebrates, serving to separate waste products from the blood and to excrete them as urine

  • Aldosterone

    • A hormone produced by the adrenal glands that stimulates the reabsorption of Na⁺ by the distal convoluted tubules, causing water to follow (because of osmosis)

  • Angiotensin

    • A plasma protein in the blood, activated by renin, that causes constriction of arterioles and stimulates the adrenal glands to produce aldosterone (though always in the blood, only the active form, angiotensis II, acts as a hormone) 

  • Antidiuretic hormone (ADH)

    • A hormone that increases the permeability of the distal convoluted tubules and the collecting ducts to water, so that more is reabsorbed,  in the event that the osmolarity of the blood is too high (normally signifying excessive water loss).  ADH  also induces thirst

  • Atrial natriuretic protein

    • A hormone released by the walls of the heart's atrium in response to increased blood volume and pressure which inhibits the release of renin and aldosterone

  • Cortex

    • The outer layer of the kidney

  • Juxtaglomerular apparatus (JGA)

    • A specialized tissue near the afferent arteriole that realease the enzyme renin when blood pressure is too low

  • Medula

    • The inner, hyperosmotic layer of the kidney

  • Renal artery

    • The artery from which blood enters the kidneys

  • Renal pelvis

    • Where urine formed in the cortex and medulla drain;  leads to the ureter

  • Renal vein

    • The vein from which blood leaves the kidneys

  • Renin

    • An enzyme produced by the juxtaglomerular apparatus that activates the plasma protein angiotensin in the blood

  • Ureter

    • The duct by which urine passes from the kidneys to the urinary bladder

  • Urethra

    • The duct by which urine is discharged from the urinary bladder, emptying near the vagina (in females) or through the penis (in males)

  • Urinary bladder

    • A muscular, membranous sac that stores urine before excretion

  • Urine

    • A liquid containing body wastes, secreted by the kidneys, stored in the urinary bladder

Nephron

• The part of the kidneys that actually separates waste from the blood, consisting of a renal tubule and blood vessels

  • Afferent arteriole

    • The artery that subdivides into the capillaries that compose the glomerulus

  • Bowman's capsule

    • The cup-shaped capsule that encompasses the glomerulus and draws filtrate from the blood

  • Brush border

    • Microscopic protrusions that increase the surface area for reabsorption

  • Cortical nephron

    • A nephron whose loop of Henle does not extend past the cortex

  • Distal convoluted duct

    • The portion of the renal tubule in the nephron between the ascending limb of the loop of Henle and the collecting duct

  • Efferent arteriole

    • The artery that is formed when the capillaries in the glomerulus converge

  • Filtrate

    • The fluid in the renal tubule which consists of water, urea, salts, and other small molecules found in blood

  • Filtration

    • The process by which filtrate enters the renal tubule without allowing blood

  • Glomerulus

    • A ball of capillaries that secretes filtrate into the Bowman's capsule

  • Juxtamedullary nephron

    • A nephron whose loop of Henle extends past the cortex and well into the medulla

  • Loop of Henle

    • A long, narrow portion of the renal tubule which extends into the deeper tissue of the kidney

  • Peritubular capillaries

    • The capillaries that weave around and between the proximal and distal convoluted tubules

  • Podocytes

    • Selectively permeable cells on the capillaries of the glomerulus that allow water and small solutes into the Bowman's capsule, but not blood

  • Proximal convoluted duct

    • The portion of the renal tubule in the nephron between the Bowman's capsule and the descending limb of the loop of Henle

  • Reabsorption

    • The movement of substances from the filtrate back into the interstitial fluid so as to be readmitted into the blood stream

  • Renal tubule

    • The tube through which filtrate passes as it is converted into urine in the nephron

  • Secretion

    • The addition of plasma solutes into the filtrate from the interstitial fluid