Unit 3: Renal System

Question 1

Kidneys Purpose

Answer 1

1. filter blood plasma, separate wasted from useful chemicals and eliminate the waste while returning to the blood stream
2. regulate blood volume and pressure by ruminating or conversing water as necessary
3. regulate similarity of body fluids by controlling the relative amounts of water and solutes eliminated

Question 2

Kidney Secretion

Answer 2

• secretes renin activated hormonal mechanisms that control BP and electrocute balance
• secretes erythropoietin, controls RBC
• works with lungs to regulate the pCO2 and acid-base balance of the body fluids
• contributing to calcium homeostasis through synthesis of vitamin D
• detoxifying free radicals and drugs

Question 3

Uremia

Answer 3

• syndrome of diarrhea, vomiting, suspension and cardiac arrhythmia caused by toxic effects of nitrogenous wastes based on the loss of kidney function
• kidney failure requires hemodialysis to remove nitrogenous wastes from the blood

Question 4

Kidney Structure

Answer 4

• medial surface is concave and has a slit (hilum) where kidneys connect to renal nerves, blood vessels, lymphatic and ureter
• renal parenchyma is glandular tissue that forms urine and is divided into the outer renal cortes and an inner renal medulla facing the sinus
• extensions of the cortex are renal columns and project toward the sinus to divide the medulla into 6-10 renal pyramids; each pyramid is conical with a broad base facing the cortex and a blunt poring renal papilla facing the sinus
• each papilla is nestled into a mini calyx (collects urine); 2-3 major calyces merge in the sinus to form a renal pelvis
• ureter is a tubular continuation of the renal pelvis, drains urine to the urinary bladder

Question 5

Circulation through the Kidney

Answer 5

• supply is by the renal artery from the aorta and divides into interlobar arteries
• each interlobar artery penetrates each renal column toward the corticomedymllary junction; where afferent arterioles branch out a right angles, each supplying one nephron and leads to a spheroidal mass of capillaries called glomerulus
• just outside the glomerular capsule, afferent and efferent arterioles contact the first part of the distal convoluted tubule in a nephron and form a juxtaglomerular apparatus
• network of capillaries called the vasa recta supply the renal medulla; lead to venues that ascent and empty into the arch are and interlobular veins

Question 6

Nephron

Answer 6

• functional unit of the kidney
• juxtamedullary nephron makes concentrated urine; more inside medulla
• cortical nephron; more inside cortex
• each consists of a renal corpuscle where the blood plasma is filtered, and a long renal tubule that processes this filtrate into urine

Question 7

Renal Corpuscla

Answer 7

consists of the glomerulus and a two-layered glomerular (Bowmans) capsule that encloses it

• the outer layers is a simple squamous epithelium, the inter consists of elaborate podocytes wrapped around the capillaries of the glomerulus
• fluid that filters from glomerular capillaries collects in capsular space; then flows to renal tubule on one side of the capsule
• larger afferent arterioles enters the capsule and brings blood to the glomerulus, with a large inlet and a small outlet; efferent carries blood away

Question 8

Renal Tubule

Answer 8

• duct that leads away from the glomerular capsule and ends at the tip of a medullary pyramid divided into the proximal convoluted tubule, nephron loop, distal convoluted tubule and collecting duct
• collecting duct receives from many nephrons

Question 9

Proximal Convoluted Tubule

Answer 9

• arises from the capsule

- longest and most coiled region; micro villi and cuboidal epithelium

Question 10

Nephron Loop

Answer 10

• divided into a thick and thin segments; thick have simple cubodial epithelium at the initial part of the descending limb and all of the ascending limb
• cells are heavily engaged in active transport; high metabolic activity
• in the renal medulla, U-shaped loop

Question 11

Distal Convoluted Tubule

Answer 11

• in the renal cortex
• shorter and less convoluted than PCT with a cubodial epithelium and almost no microvilli
• drains to the collecting duct which passes into the medulla

Question 12

Urine Formation

Answer 12

1. filtration; fluid and solutes are filtered through the glomerulus and enter the capsule
2. tubular reabsorption; recovered useful solutes and water
3. tubular secretion; eliminates wastes from blood
4. water conservation; waster is recovered from filtrate, resulting in urine which passes to collecting ducts

Question 13

Glomerular Filtration

Answer 13

• water and solutes in blood plasma are pushed under pressure from the capillaries of the glomerulus into the capsular space
• fluid passes through three barriers for filtration;
  1. fenestrated endothelium; endothelial cells in capillaries with large filtration pores, small enough to exclude blood cells from filtrate
  2. basement membrane; a proteoglycan he what excludes molecules larger than 8nm, and are (-)
  3. filtration slits; podocytes of capsule extend around capillaries, which have (-) 20nm slits

Question 14

Kidney Infection or Trauma and Filtration

Answer 14

• can allow albumin or blood cells to filter through; hence blood in grime in kidney disease (proteinuria and hematuria)
• distance athletes can experience temporary due to strenuous exercise reducing perfusion of the kidneys, glomerulus deteriorates under prolonged hypoxia

Question 15

Blood Hydrostatic Pressure

Answer 15

• much higher in glomerulus than elsewhere; 60mmHg rather than 10-15; b/c afferent arterioles is larger than efferent
• pressure in capsular space is 18mmHg; from high rate of filtration. occurring and the continual accumulation of fluid in the capsule
• creates 10mmHg net filtration pressure to push fluid through the glomerulus, leaving little safety margin of arterial BP fails; low BP = kidney failure
• BHP drops along the glomerular capillaries but remains high that they are engaged in filtration and resort little or no fluid
• high BP in glomerulus makes kidneys vulnerable to hypertension and hypotension

Question 16

Glomerular Filtration Regulation

Answer 16

• must be precisely controlled; if too high, fluid flows through renal tubules too rapidly for them to reabsorption water and solutes
• if too low, fluid flows slowly so they reabsorption wastes
• regulation is by glomerular BP; by translate auto regulation, sympathetic control, hormones

Question 17

Auto regulation

Answer 17

• ability of the kidney to maintain a stable GFR despite fluctuation in BP
• if glomerulus filtration rises, it increases flow of tubular fluid and NaCl reabsorption; masculine densa senses variations in flow or fluid composition and secretes paracrine messenger that stimulates juxtaglomerular cells to contract afferent arteriole, reducing filtration to normal
• if glomerular filtration falls, macula densa secretes different messenger; causes afferent arteriole and mesangial cells to relax, blood flow increase and glomerular filtration rises back to normal

Question 18

Macula Densa

Answer 18

• a group of special cells that function as a sensory receptor for NaCl levels, triggering auto regulatory response inhibiting the secretion of renin from the juxtaglomerular apparatus
• located in thick portion of ascending limb; when it loops and comes into contact with efferent and afferent arterioles
• 70-80mmHg range allows filtration to remain stable
• less than filtration and urine output stop as efferent arteriole dilate, above 180mmHg causes pressure damage and construction of efferent arterioles

Question 19

Sympathetic Control

Answer 19

• in strenuous exercise or a ute conditions like circulatory shock, the SNS and adrenal epinephrine construct afferent arteriole
• reduces glomerular filtration, redirecting blood from the kidneys to the heart, brain, and muscles

Question 20

Renin-Angiotensin Mechanism

Answer 20

• lowering in blood volume and pressure occurring together with reduced amount of NaCl and water in the filtrate is ended by the juxtaglomerular apparatus cells that secrete renin in the blood
• renin acts on angiotensin to creat angiotensin I
• in lungs and kidneys, angiotensin-converting enzyme removes two amino acids making angiotensin II, for vasoconstriction
• Raising BO, construction both arterioles and aldosterone release for sodium and water retention
• stimulates ADH and promotes thirst, increase BV and BP; high BP suppresses renin secretion

Question 21

Angiotensin II

Answer 21

• stimulates sodium reabsorption by promoting sodium transporters in tubules
• stimulates vasoconstriction of efferent and afferent arterioles, decreases filtration rate and sodium excretion

Question 22

PCT Reabsorption and Secretion

Answer 22

• reabsorbs most of filtrate and removes some substances from blood and secretes them into tubule for disposal
• secretes unwanted chemicals into tubule for excretion
• large mitochondria for ATP for active transport
• reabsorbs most variety than anywhere else via;
  1. transcultural route in which substances pass through the cytoplasm and out the base of epithelial cells; depends on active transport and facilitated diffusion to drive movement across apical and basolateral membranes
  2. paracellular route in which substances pass between epithelial cells
• sodium reabsorption creates osmotic and electrical gradients
• first have of PCT, sodium is absorbed by symptom proteins that bind glucose, amino acids, phosphate or lactate; on other side of cell; Na/K ATPase exchanges Na for K which favors recovery of ions
• has a maximum above which recovery of solutes is no longer possible
• CO2 from carbonic anhydride breakdown of bicarbonate in tubular fluid diffuses into the cell to react with water to produce carbonic acid; pumped into extracellular space and hydrogen ions into the tubule
• bicarbonate combines with H+ making carbonic acid; carbonic anhydride converts it to water and CO2 into renal tubule cells for reverse reaction
• H is secreted by secondary active transport, H2CO3 is reabsorbed by facilitated diffusion

Question 23

Loop of Henle Reabsorption and Secretion

Answer 23

• countercurrent multiplier mechanism; adjusting Na transport to alter osmotic strength or urine
• thin wall descending limb is permeable to water and urea, impermeable to Na
• thick wall ascending limb is impermeable to water, contains high concentration of ion pumps
• when flow starts in tubular fluid, descending limb is carrying higher osmolarity towards base of the loop in equilibrium with interstitial fluid; fluid in ascending limb moved up is exposed to lower interstitial fluid ion concentrations so ion concentrations fall
• with flow, gradient is established that is limited only by the ability of ions to diffuse up or down around the loop
• vasa recta around LOH has slow moving blood supply to provide energy to maintain gradient

Question 24

Countercurrent Multiplier Mechanism

Answer 24

1. interstitial fluid is hypertonic due to NaCl pumped out of ascending limb
2. water leaves descending limb by osmosis, making filtrate hypertonic into ascending limb
3. more NaCl in ascending limb can be pumped out into the interstitial fluid
4. greater concentration of interstitial fluid draws more water from descending limb
5. filtrate in ascending limb becomes more concentrated
6. continues until max [NaCl] of inner medulla is reached

Question 25

Distal Convoluted Tubule Reabsorption and Secretion

Answer 25

• tubular fluid in DCT is hypo-osmotic due to pumps in ascending LOH
• much short than PCT and less metabolically active, though can reabsorb ions, secrete ammonia, hydrogen ions, potassium and toxins

Question 26

Collecting Ducts

Answer 26

• concentrating the urine is done as in order to exit kidney, grind arriving in CDs has to pass through the medulla, exposed to the LOH concentration traction gradient
• have squalor in channels on luminal side to facilitate water transport; in presence of ADH
• with ADH, osmosis can be used to recover large amounts of water as urging moves down collecting ducts via AQP2 channels; pumps more urea into interstitial fluid
• impermeable to water with no ADH; produces hypotonic urine

Question 27

Bladder and Micturition

Answer 27

• urine passed into ureters to the bladder; storage sac for grime, changes shape based on urine volume
• stored until pressure on wall triggers sympathetic reflex that causes contraction of the muscle wall of the bladder and relaxation of the internal sphincter at the base of the bladder; relaxation allows urine into urethra
• the external sphincter controls voluntary skeletal muscle

Question 28

Mammalian Adaptions to Extreme Environments

Answer 28

• in deserts, animals generate water by burning fat to get ATP -!: conserve by excreting concentrated thing by having kidneys with lots medullary LOH
• marine animals don’t have access to fresh water, make a concentrated urine and get water from their food
• hibernating animals reduce body temperature and metabolic rate, recycle urea into protein for less protein waste; reabsorb water from urine to limit urinating

Question 29

Kidney Stones

Answer 29

• hard objects formed in the kidney made of calcium phosphate and calcium oxalate
• form when individual is dehydrated
• structure stones following a UTI
• uric acid stones with gout
• cystine stones in cystinuria
• stones < 5mm can pass in the ureter