Urinary physiology

Question 0

renal cortex function

Answer 0

protects kidney, holds everything together, made out of connective tissues

Question 1

structure of urinary system

Answer 1

urine forming organs ( kidneys)
-structures that carry urine from kidneys to the outside for elimination from the body ( ureters, urinary bladder, urethra)

Question 2

order of renal blood supply

Answer 2

renal artery- segmental artery- interlobar artery- arcuate artery- interlobular artery - afferent arteriole- glomerulus- efferent arteriole

Question 3

each nephron has its own

Answer 3

afferent arteriole, capillary tuft, and efferent arteriole

Question 4

vasa recta

Answer 4

they are efferent arterioles from the peritubular capillaries that wraps around nephron structure.
- the loop structure enables them to pick up interstitial fluid without removing excess solute

Question 5

function of kidney

Answer 5

regulate blood ionic composition, maintain blood osmolarity, regulate blood volume, blood pressure, acid and base balance, excretion of waste products, endocrine functions

Question 6

structure of kidneys

Answer 6

bean-shaped, concave side inward

• located in posterior part of abdomen on each side of the spine, top of kidney at 12th thoracic vertebrae
• right kidney sits below liver
• left kidney sits below diaphragm

Question 7

urinary bladder

Answer 7

• stores urine temperature

- a hollow, distensible, smooth-muscle walled sac

Question 8

Urethra

Answer 8

• urine is emptied from bladder to outside through this due to bladder contraction
• female is short and straight
• male is longer and curving course, serves as a passageway for semen

Question 9

Nephron

Answer 9

is the functional unit of kidney, about 1 million nephron per kidney

• has 2 components: vascular and tubular
• regulate water and solute ( especially electrolytes) by filtering blood under pressure and then reabsorbing necessary fluid and molecules back into blood while secreting other unneeded molecules.

Question 10

vascular component

Answer 10

glomerulus: ball like tuft of capillaries through which part of the water and solutes is filtered from blood passing through

afferent arteriole: where blood is carried to glomerulus

efferent arteriole: where blood is exiting

peritubular capillaries: supply renal tissue, exchange with fluid in tubular lumen

Question 11

tubular component

Answer 11

bowman’s capsule: collects the glomerular filtrate

proximal tubule: uncontrolled reabsorption and secretion of selected substances

loop of henle: establishes an osmotic gradient in renal medulla that is important in the kidney’s ability to produce urine

distal tubule and collecting duct: variable, controlled reabsorption of Na and water, secretion of potassium and hydrogen ions occur here, fluid leaving collecting duct is urine, which enters renal pelvis

Question 12

combined vascular/tubular component

Answer 12

Juxtaglomerular apparatus: produces substances involved in the control of kidney function

Question 13

Glomerular filtration

Answer 13

where a portion of the blood plasma is filtered into kidney
-passes through 3 layers (fluid): walls of capillaries, basement membrane, inner layer of Bowmann’s capsule (podocytes): narrow slits in between capsular filtration slites

Question 14

GFR rate

Answer 14

determined by filtration pressure in glomeruli and permeable surface of glomerular membrane

• pressure varies from different end of glomerulus to efferent end ( pressure from capsule and afferent arteriole)
• normal GFR is 125 for male and 115 for female

Question 15

Forces in GFR

Answer 15

net filtration pressure: total pressure that promotes filtration

glomerular capillary blood pressure: hydrostatic pressure by fluid and colloidal ( protein and albumin)

plasma colloid osmotic pressure: plasma protein distribution and back pressure in bowman’s capsule ( constant in normal condition, change in abnormal condition)

Question 16

2 major control mechanisms

Answer 16

autoregulation: prevents changes in GFR, include myogenic mechanism aka muscle generated tissues AND tubuloglomerular feedback

extrinsic sympathetic control ( long term regulation of arterial blood pressure): by SNS input to afferent arterioles and baroreceptor reflex

Question 17

role of mesangial cells

Answer 17

located around glomerular capillaries, regulate SA available for filtration (contraction decrease SA, relaxation increase SA)
-lower SA, increase filtration pressure

Question 18

Tubuloglomerular feedback aka negative feedback

Answer 18

• each nephron can regulate its own GFR
• Juxtaglmerular apparatus controls this process, include glomerulus, macular densa, specialized juxtaglomerular cells: produce and release Renin

Question 19

Macula densa cells

Answer 19

sample the NaCl content in the distal tubule, signal the juxtaglomerular apparatus to make appropriate adjustments in GFR

Question 20

Hormonal regulation of GFR

Answer 20

1. Atrial natriuretic peptide ( ANP)- INCREASE GFR
   - stretching of the atria that occurs with an increase in blood volume cause hormonal release
   - inhibits sodium reabsorption
   - promotes diuretic effects
2. Angiotensin II: DECREASE GFR
   - potent vasoconstrictor that narrows both afferent and efferent arterioles

Question 21

Tubular reabsorption

Answer 21

involves the transfer of substances from the tubular lumen back into the peritubular capillaries

• involves transepithelial transport ( cross 5 barriers)
• cross luminal membrane, pass through cytosol, cross basolateral membrane, diffuse through interstitial fluid, penetrate capillary wall to enter blood plasma

Question 22

Reabsorption of glucose

Answer 22

• glucose filter freely across glomerular membrane
• reabsorbed in proximal tubule by sodium dependent cotransporter
• if cotransporter has too much glucose, it can lead to glycosuria and reach renal threshold where the glucose begins spilling in the urine

Question 23

renal threshold (tubular max)

Answer 23

maximum ability of the kidney to absorb

• active reabsorption required carrier
• carrier is substance specific, so nothing beyond is absorbed except for sodium
• 275 mgm of glucose per min

Question 24

tubular secretion

Answer 24

transfer of selective substances from peritubular capillaries into tubular lumen - mainly H+ and K+ ions, organic anions and cations - Hydrogen is secreted in proximal, distal, and collecting tubules - Potassium is secreted in distal and collecting duct - Organic ions is secreted in proximal tubules

Question 25

H+ and K+ secretion effects

Answer 25

when body is too acidic, more hydrogen ions are secreted, so potassium is retained in body fluids. -Na and H are secreted in exchange for Na reabsorption

Question 26

excretion

Answer 26

- end product that includes excess ions, water, molecules, toxins, foreign molecules - include nitrogenous waste, ammonium, excess urea - urine output is 1 to 1.5L a day

Question 27

Medullary countercurrent mechanism

Answer 27

- happens in juxtamedullary nephrons - contributes to vertical osmotic gradient - Descending limb: thin epithelium and permeable to water only, NO sodium reabsorption - Ascending limb: thick epithelium and IMpereable, actively transports NaCl out of tubular lumen into interstitial fluid

Question 28

benefits of countercurrent mechanism

Answer 28

- effective water reabsorption | - final adjustment depends on condition of body fluid

Question 29

Role of Vasopressin

Answer 29

- distal and collecting tubules are impermeable to water in absence of ADH - has no influence on loop of henle and proximal tubule

Question 30

role of aldosterone

Answer 30

- acts on distal and collecting tubule - through activation of RAAS - Na reabsorption

Question 31

renal endocrine function

Answer 31

kidney normally secrete erythropoietin, a growth factor for RBC and active vitamin D, a cofactor for calcium reabsorption -in chronic renal failure, anemia and osteodystrophy are consequences

Question 32

Erythropoietin

Answer 32

- peptide growth factor that stimulates RBC development in bone marrow - increased release with hypoxia and decrease circulating red cell mass

Question 33

Vitamin D

Answer 33

- Kidney performs second hydroxylation of vitamin D to form 1,25 hydroxycholecalciferol, an active form of vitamin D needed for calcium reabsorption - facilitate calcium reabsorption in kidney tubules

Question 34

Renal plasma clearance

Answer 34

volume of plasma cleared of a particular substance per minute - clearance rate is U times V/P - U is urine concentration - V is urine flow rate/min - P is plasma concentration of substance

Question 35

creatine and insulin clearance

Answer 35

creatine- end product of muscle metabolism, filtered, not reabsorbed, slightly secreted insulin- syn. carb, more accurate measurement of GFR

Question 36

Dialysis

Answer 36

separation of large solutes from smaller ones through use of selectively permeable membrane - hemodialysis: filter blood through artificial kidney machine - peritoneal dialysis: catheter or peritoneum

Question 37

net filtration pressure formula

Answer 37

glomerular capillary blood pressure - opposition blood pressure = NFP - favour filtration - about 20% of plasma entered is filtered at NFP

Question 38

transepithelial transport

Answer 38

passive is no energy active is glucose, amino acid, sodium, phosphate -active can be Na-K ATPase pump: where most is reabsorbed in the proximal tubule

Question 39

Countercurrent mechanism extra info

Answer 39

- descending loop is permeable to water and equilibrates with the rising interstitial solute concentration - so when filtrate reaches ascending loop, it is more concentrated, allowing ascending loop to further increase the osmolarity of the interstitial fluid