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Afferent arterioles are branches fr interlobular arteries that . . . .
deliver fresh blood that hasnt been exposed to renal sys to glomerulus
Blood leaves the nephrons through ____ ____ & travels to ____ ____ that surround proximal & distal convoluted tubules.
- Efferent Arterioles
- Peritubular Capillaries
What is filtrate?
A protein free solution that is the product of solution
Describe the process filtration.
In the renal corpuscle BP forces fluid & dissolved solutes out of glomerular capillaries & into surrounding capsular space
What are the 2 parts of the renal corpuscle?
- Bowman's capsule
The Bowman's capsule forms . . . .
- outer wall of the renal corpuscle & encapsulates glomerular capillaries
- place where filtrate is collected & sent out thru proximal convoluted tubule
The glomerulus projects into. . . .
Bowman's capsule much like the heart projects into the pericardial cavity
Describe the glomerulus.
- Capillary network where filtration takes place
- Afferent arteriole goes thru Bowman's capsule & becomes efferent arteriole
Describe the Proximal Convoluted Tubule.
- First segment of renal tubule
- Absorbs organic nutrients, plasma nutrients & ions fr tubular fluid & releases them into interstitial fluid around renal tubule
What are the 2 parts Loop of Henle.
- Descending Loop - travels toward renal pelvis
- Ascending Loop - returns to cortex
What does the Ascending Limb of the Loop of Henle do?
- Actively transports Na & chloride ions out of tubular fluid
- Limb NOT permeable to water
- Causes high solute concentration in medulla
What does the Descending Limb of the Loop of Henle do?
- Descends into medulla where H2O moves out by osmosis
- Limb is permeable to H2O
What are 2 important functions of the DCT?
- Active secretion of ions, acids, drugs & toxins
- Selective reabsorption of Na ions fr tubular fluid
What is the macula densa?
- Epithelial cells that are closest to the glomerulus
- Usually tall w/ nuclei clustered together
The juxtaglomerular apparatus consists of ____ & ____.
- Macula Densa
- Juxtaglomerular Cells
What is the juxtaglomerular apparatus?
Endocrine structure that secretes the hormone erythropoietin & enzyme renin
The ____ ____ receiving urine fr ____ & merge into papillary ducts.
The ____ ____ delivers urine to a minor calyx
The collecting sys on a whole does what?
Makes final adjustments to urine by reabsorbing H2O or reabsorbing or secreting various ions
What does ADH do?
- Ctrls amt of H2O reabsorbed along DCT & collecting duct
- W/O ADH DCT & collecting duct impermeable to H2O
If circulating ADH levels are low what happens?
- Little H2O is reabsorbed
- Virtually all H2O reaching DCT is lost to urine
If circulating ADH levels are high what happens?
- DCT & collecting duct are very permeable to H2O
- Person produces sm amt of highly concentrated urine
The DCT & collecting ducts contain ion pumps that respond to the ____ ____ which is produced in the ____ ____.
- Hormone Aldosterone
- Adrenal Cortex
What causes aldosterone to be secreted?
In response to lowered Na+ concentrations or elevated K+ concentrations in blood
The higher the aldosterone levels are in the DCT & collecting tubes what happens?
The more Na+ are reclaimed & the more K+ are lost
What is the effect of angiotensin II on peripheral capillary beds?
Brief but powerful Vasoconstriction causing BP elevation in renal arteries
What is the effect of angiotensin II @ the nephron?
Triggers constriction of efferent arterioles elevating glomeruler pressures & filtration rates
What is the effect of angiotensin II in the CNS as it relates to urinary sys.
Triggers release of ADH stimulating reabsorption of H2O & Na ions causing sensation of thirst
What is the effect of angiotensin II @ the adrenal gland?
Stimulates secretion of aldosterone by adrenal cortex & epi/norepi by adrenal medullae causing increase in systemic BP
At the kidney aldosterone stimulates . . . . .
Na reabsorption along DCT & collecting sys
What does renin do?
- Part of the renin- angiotensin sys
- Converts inactive angiotensinogen to angiotensin I which a converting enzyme activates angiotensin II
What is the renin-angiotensin system?
Causes release of renin by juxtaglomerular apparatus in response to low glomerular pressures due to decrease in blood volume, fall in systemic pressures or blockage of renal artery or its tributaries
What is secretion?
- Transport of solutes out of peritubular capillaries, across tubular epithelium & into filtrate
- Can further lower plasma concentration of undesirable materials
Why is secretion necessary?
B/c filtration does not force all dissolved materials out of blood
What is reabsorption?
- Removal of water & solute molecules fr filtrate & their reentry into circulation @ peritubular capillaries
- Occurs aft filtrate enters renal tubule
Describe process of reabsorption.
- A selective process that involves simple diffusion or the activity of carrier proteins in the tubular epithelium
- H2O reabsorption occurs passively thru osmosis
What is the primary purpose of urine production?
Maintain homeostasis by regulating vol & composition of blood
What 3 dissolved solutes are excreted with urine?
What is Urea?
Organic waste created during breakdown of amino acids
What is creatinine?
Metabolic waste created in skeletal muscle thru breakdown of creatine phosphate
What is Uric Acid?
Metabolic waste created during breakdown & recycling of RNA
What is filtration pressure?
Around 10 mmHg
What is the Glomerular Filtration Rate?
- Amt of filtrate produced in kidneys each minute
- About 125mL/min
What is a minor calyx?
Cup shaped drain that ducts within the renal papilla discharge urine into
What makes up a major calyx?
- 4 or 5 minor calyces merged together
- 2 major calyces merge to form funnel shaped chamber or renal pelvis
What is the renal pelvis?
- funnel shaped chamber made up of both major calyces
- Connected to ureter thru which urine drains out of kidney
What is the hilum the site of?
- Exit of ureter fr kidney
- Place where renal artery & renal nerve enter kidney
- Renal vein exits kidney
Where does the renal artery originate & go?
- Starts @ abd aorta
- Enters renal sinus & divides branches that supply interlobular arteries
The renal vein receives blood fr where?
Interlobular veins -> arcuate -> interlobar -> renal veins & out of the kidney
What are peritubular capillaries?
- Network of capillaries that surround proximal & distal convoluted tubules
- Provide route for p/u or delivery of substances reabsorbed or secreted by this portion of the nephron
What is the vasa recta?
Long, straight capillaries that parallel loop of henle deep into the medulla
What is the difference between juxtamedullary & cortical nephrons?
Juxtamedullary nephron structure is located mostly within the medulla where as a cortical is located within the cortex
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