Term
| What percent of total body weight are the kidneys? |
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Definition
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Term
| What percent of cardiac output do the kidneys use? |
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Definition
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Term
| What happens to H+ and HCO3- if the pH of plasma becomes too acidic? Too basic? |
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Definition
| If acidic, the kidneys will remove H+ and conserve bicarbonate ions (HCO3-), which act as a buffer. If too basic, the kidneys remove HCO3- and conserve H+. |
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Term
| What is the relationship between extracellular fluid volume and blood pressure? |
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Definition
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Term
| Which two major hormones are produced by the kidney? |
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Definition
| Renin (cascade for BP and Na+ balance) and Erythropoietin (RBC production). |
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Term
| Where are the kidneys located? |
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Definition
| In the retroperitoneal position (between peritoneum and bones/muscles of the back) by the T12-T13 vertebrae. The left kidney is typically higher up, and each are about 4.5 inches long. |
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Term
| What is the relationship between hydrostatic pressure and oncotic pressure for filtration? For re-absorption? |
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Definition
| Hydrostatic pressure must be greater than oncotic pressure in the glomerular capillaries for filtration, and less than oncotic pressure for re-absorption. |
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Term
| What are the renal columns of the kidney? |
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Definition
| They are medullary extensions of the renal cortex between renal pyramids (striped because of nephrons). They supply blood vessels to the region. |
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Term
| What is the pelvis of the kidney? |
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Definition
| The site of convergence of the minor and major calyces that funnel into the ureter (hilus). |
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Term
| How many nephrons are there per kidney? |
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Definition
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Term
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Definition
| The group of capillaries that surround the loop of henle in juxtamedullary nephrons (20% of total nephrons). |
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Term
| Describe the path of blood from the renal artery to the renal vein. |
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Definition
| Renal artery --> afferent arterioles --> glomerulus --> efferent arterioles --> peritubular capillaries (vasa recta) --> venules --> small veins --> renal vein. |
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Term
| What composes the renal corpuscle? |
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Definition
| The glomerulus and Bowman's capsule. |
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Term
| Where is the only site of filtration in the nephron? |
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Definition
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Term
| What kind of capillaries compose the glomerulus? |
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Definition
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Term
| What do the podocytes do as part of Bowman's capsule? |
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Definition
| They wrap around capillaries and leave "gaps" or "filtration slits". This restricts most macromolecules from being filtered. They podocytes can contract to lower the renal filtration rate. |
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Term
| What do mesangial cells do? |
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Definition
| They lie between and around the golmerular capillaries and can contract and alter blood flow. They are also phagocytic and associated with immune and inflammatory processes. |
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Term
| What is the basal lamina? |
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Definition
| It separates the capillary epithelium from the epithelial lining of bowman's capsule and acts like a coarse sieve, excluding most plasma proteins from the fluid that filers through it (negatively charged glycoproteins). |
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Term
| How do the kindey arterioles respond to Angiotensin 2? |
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Definition
| The afferent arteriole (smooth muscle) is resistant, whereas the efferent arteriole (smooth muscle) is activated. |
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Term
| What is the primary function of the proximal convoluted tubule? |
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Definition
Bulk reabsorption of isoosmotic fluid (same osmolaity of filtrate entering and leaving.
85% reabsorption of water (transports solutes out of lumen, water follows). Glucose is typically coupled with the Na+ transport. |
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Term
| What drives filtration across the walls of the glomerular capillaries? |
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Definition
| Hydrostatic pressure (Ph ~ 55 mm Hg) - colloid osmotic pressure (presence of proteins in the plasma ~ 30 mm Hg) - hydrostatic fluid pressure (fluid filtering out of the capillaries must displace fluid in capsule ~ 15 mm Hg) = 10 mm Hg of net filtration pressure |
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Term
| How does the renal countercurrent multiplier work? |
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Definition
The thin descending tubule is water permeable, whereas the think ascending tubule is Na+, K+, and Cl- permeable.
The loop of Henle and vasa recta tend to dip down into the more concentrated environment of the medulla and ascend into the cortex again. Also, blood flow in the vasa recta is opposite of the flow of the loop of Henle.
As fluid flow down the descending limb closer to the medulla, water moves by osmosis into the progressively more concentrated interstitial fluid. Blood in the vasa recta removes water leaving the loop because it moves in an opposite direction; it is already highly concentrated. The filtrate becomes progressively more concentrated as it moves deeper into the medulla.
In the ascending limb, active loss of solute from the lumen makes the filtrate less concentrated. Blood in the vasa recta absorbs the solutes. |
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Term
| What is the net result of the countercurrent multiplier? |
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Definition
| To produce hyperosmotic interstitial fluid in the medulla and hypoosmotic filtrate leaving the loop of Henle. 300 mOsm filtrate becomes 100 mOsm filtrate. Without the vasa recta, water moving out of the descending limb would eventually dilute the medullary interstitium. Urea also helps to concentrate the medulla. |
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Term
| What are the functions of the distal convoluted tubule? |
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Definition
| Secretion (from ECF into lumen) of K+ with aldosterone, acidification, and reabsorption of Na+. The final concentration can range from 50 mOsm to 1200 mOsm. |
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Term
| What is the overall RAA system? |
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Definition
Low renal blood pressure is sensed by the macula cells located next to the JG apparatus. This stimulates the JG apparatus to release Renin, which converts Angiotensinogen (from the liver) into Angiotensin I. ACE from the lungs and kidneys (capillary beds)converts I into II.
Angiotensin II causes vasoconstriction, stimulates the sympathetic nervous system, ADH secretion, reabsorption of Na+, Cl-, and water, and absorption of K+. It also triggers the release of aldosterone from the adrenal gland to assist with the ion and water changes.
Angiotensin III is also released, which is a vasoconstrictor. |
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Term
| What is the main function of the collecting duct? |
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Definition
| Concentrating the filtrate (duct is permeable to water and urea). |
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Term
| What does ADH do and where is it produced? |
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Definition
| ADH helps manage water reabsorption in the collecting duct. It is produced by the supraoptic nuclei of the hypothalamus, stored, and then released by the posterior pituitary. |
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Term
| What are the typical ranges of ADH levels? |
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Definition
Low: 87% reabsoprtion, 24 L excretion, Diabetus isipidus (alcohol prevents the release of ADH)
Normal: 98.7% water reabsorption, 1.5 L excretion
High: 99.7% water reabsorption, 0.5 L excretion |
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Term
| What regulates ADH output and how? |
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Definition
| Osmoreceptors in the hypothalamus regulate output. These cells shrink if plasma osmolality is increased 1-2% (also occurs in hypovolemia, low blood volume, triggering the release of ADH. |
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Term
| What are the three layers of the ureters? |
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Definition
| Mucosa, muscularis, and fibrous. |
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Term
| How do ureters prevent urine backflow? |
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Definition
| The ureters run obliquely through the bladder wall, forming a valve. Also, the ureters propel urine via peristaltic waves, not gravity. |
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Term
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Definition
| The trigone is the 2 ureter input into the bladder and the 1 urethra outflow. |
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Term
| What are the two sphincters of the urethra? |
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Definition
| The internal sphincter (smooth muscle) and the external sphincter (skeletal muscle, for control). |
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Term
| What are the three portions of the male urethra? |
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Definition
| The prostatic (travels through prostate, joined by 2 ejaculatory ducts), the membranous (external urethral sphincter), and the cavernous (in Corpus Spongiosum). |
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Term
| Which nervous pathway is most important in controlling micturition? |
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Definition
| The parasympathetic pathway. |
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Term
| At what volume of urine is a person aware of the desire to urinate? |
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Definition
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Term
| What maintains tonus as the bladder fills? |
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Definition
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Term
| What happens during reflex (automatic) urination? |
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Definition
The detrusor muscle contracts, which is an internal structure. The external sphincters relax, and then the bladders empties.
This is common in infants and spinal cord injury patients, and occurs above 200 mL. |
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Term
| What happens during atonic urination? |
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Definition
| The detrusor muscle tone is lost, so dribbling and incontinence (lack of control) occurs. |
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Term
| What happens during controlled urination? |
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Definition
| The cerebral cortex normally inhibits the contraction of the detrusor muscle, and can coordinate the relaxation of sphincters. |
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