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| 1. | anatomical sphincter | smooth or skeletal muscle surrounding the lumen of a vessel or hollow organ that can restrict flow when contracted |
| 2. | angiotensin II | protein produced by the enzymatic action of ACE on inactive angiotensin I; actively causes vasoconstriction and stimulates aldosterone release by the adrenal cortex |
| 3. | angiotensin I | protein produced by the enzymatic action of renin on angiotensinogen; inactive precursor of angiotensin II |
| 4. | angiotensin-converting enzyme | (ACE) enzyme produced by the lungs that catalyzes the reaction of inactive angiotensin I into active angiotensin II |
| 5. | angiotensinogen | inactive protein in the circulation produced by the liver; precursor of angiotensin I; must be modified by the enzymes renin and ACE to be activated |
| 6. | anuria | absence of urine produced; production of 50 mL or less per day |
| 7. | 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 |
| 8. | 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 |
| 9. | 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 |
| 10. | calyces | cup-like structures receiving urine from the collecting ducts where it passes on to the renal pelvis and ureter |
| 11. | cortical nephrons | nephrons with loops of Henle that do not extend into the renal medulla |
| 12. | countercurrent multiplier system | involves the descending and ascending loops of Henle directing forming urine in opposing directions to create a concentration gradient when combined with variable permeability and sodium pumping |
| 13. | 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 |
| 14. | distal convoluted tubules | portions of the nephron distal to the loop of Henle that receive hyposmotic filtrate from the loop of Henle and empty into collecting ducts |
| 15. | diuretic | compound that increases urine output, leading to decreased water conservation |
| 16. | efferent arteriole | arteriole carrying blood from the glomerulus to the capillary beds around the convoluted tubules and loop of Henle; portion of the portal system |
| 17. | endothelins | group of vasoconstrictive, 21-amino acid peptides; produced by endothelial cells of the renal blood vessels, mesangial cells, and cells of the DCT |
| 18. | external urinary sphincter | skeletal muscle; must be relaxed consciously to void urine |
| 19. | 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 |
| 20. | filtration slits | formed by pedicels of podocytes; substances filter between the pedicels based on size |
| 21. | forming urine | filtrate undergoing modifications through secretion and reabsorption before true urine is produced |
| 22. | glomerular filtration rate | (GFR) rate of renal filtration |
| 23. | glomerulus | tuft of capillaries surrounded by Bowman's capsule; filters the blood based on size |
| 24. | 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 |
| 25. | incontinence | loss of ability to control micturition |
| 26. | intercalated cell | specialized cell of the collecting ducts that secrete or absorb acid or bicarbonate; important in acid-base balance |
| 27. | internal urinary sphincter | smooth muscle at the juncture of the bladder and urethra; relaxes as the bladder fills to allow urine into the urethra |
| 28. | inulin | plant polysaccharide injected to determine GFR; is neither secreted nor absorbed by the kidney, so its appearance in the urine is directly proportional to its filtration rate |
| 29. | 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 |
| 30. | juxtaglomerular cell | modified smooth muscle cells of the afferent arteriole; secretes renin in response to a drop in blood pressure |
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