Renal Anatomy Flashcards by Chenoa Kannan

What are the functions of the kidneys?

Regulation of blood ionic composition
Regulation of blood volume
Regulation of blood pH
Regulation of blood pressure
Maintenance of blood osmolarity
Production of two hormones
Excretion of wastes and foreign substances

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What is the regulation of blood ionic composition (functions of the kidneys)?

Kidneys help regulate the blood levels of several ions
- Na+
- K+
- Ca2+
- Cl-
- HPO4^2- (Phosphate ions)

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What is the regulation of blood volume (functions of the kidneys)?

Kidneys adjust bld. vol. by conserving/eliminating water in urine.
- Increase in bld. vol. = increases bld. pressure
- Decrease in bld. vol. = decrease bld. pressure

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What is the regulation of blood pH (functions of the kidneys)?

Kidneys excrete variable amt of H+ into urine & conserve HCO3- (impt buffer of H+)

Both these activities help regulate blood

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What is the regulation of blood pressure (functions of the kidneys)?

Kidneys help regulate bld. pressure by secreting enzyme renin = activates renin-angiotensin-aldosterone (RAAS) pathway
- Increased renin causes an inc. in bld. pressure

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What is the maintenance of blood osmolarity (functions of the kidneys)?

Regulates loss of water & loss of solutes in urine (separately) = maintain relatively constant blood osmolarity (~300mOsm/liter)

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What are the two hormones the kidney produces and what do they do (functions of the kidneys)?

Calcitriol - active form of vitamin D = regulate calcium homeostasis

Erythropoietin - stimulates production of RBCs

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What is the excretion of wastes & foreign substances (functions of the kidneys)?

By forming urine, the kidneys help excrete wastes - substances that have no useful function in the body
- Some wastes excreted are from metabolic reactions = e.g. ammonia & urea from deamination of a.a.
- Drugs/environmental toxins

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Slide 6

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What happens at the renal corpuscle?

Production of filtrate

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What happens at the proximal convoluted tubule?

Reabsorption of water, ions, all organic nutrients

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What happens at the descending thin limb of the nephron loop (loop of Henle)?

Further reabsorption of water

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What happens at the thick ascending limb of the nephron loop (loop of Henle)?

Reabsorption of Na+ & Cl-

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What happens at the distal convoluted tubule?

Secretion of ions, acids, drugs, toxins
Variable reabsorption of water, Na+, Ca2+ (under hormonal control)

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What happens at the collecting duct?

Variable reabsorption of water a& reabsorption/secretion of Na+, K+, H+, HCO3-

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What happens at the papillary duct?

Delivery of urine to minor calyx

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What are the renal processes for the formation of urine?

Glomerular filtration
Tubular reabsorption
Tubular secretion

Highly efficient = only 20% of plasma that passes through the glomerulus is filtered –> <1% of filtered fluid is excreted

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What happens during glomerular filtration?

Water & most solutes (minus proteins) in bld plasma moves across the wall of glomerular capillaries
- Filtered and move into glomerular capsule & into renal tubule

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What happens during tubular reabsorption?

The filtered fluid flows through the renal tubules and through the collecting ducts
- Tubule cells reabsorb ~99% of filtered water & many useful solutes
- Water and solutes return to the blood as it flows through the peritubular capillaries & vasa recta

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What happens during tubular secretion?

As filtered fluid flows through the renal tubules & collecting ducts = renal tubule & duct cells secrete other materials (wastes - metabolic, drugs, excess ions) into fluid

REMOVES substance from blood

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What cells are present at the renal corpuscle?

Squamous cells

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What cells are prevent in the proximal convoluted tubule?

Cuboidal cells with abundant microvilli

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What cells are present in the descending thin limb (DTL) of the nephron loop/loop of Henle?

Squamous cells

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What cells are present in the thick ascending limb (TAL) of the nephron loop/loop of Henle?

Low cuboidal cells

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What cells are present in the ascending thin limb (ATL) of the nephron loop/loop of Henle?

Squamous cells

What cells are present in the collecting duct?

Intercalated cells (regulate pH balance) & principal cells (adjust electrolyte conc.)

What cells are present in the papillary duct?

Columnar cells

How to calculate amount of solute excreted?

Amount filtered - amount reabsorbed + amount secreted = amount of solute excreted

What is the outer (parietal) wall of the glomerular (Bowman's) capsule lined with?

Simple squamous capsular epithelium

What is the capsular epithelium continuous with?

Continuous with the visceral epithelium that covers glomerular capillaries, separated by capsular space

What does the visceral epithelium consist of?

Podocytes = large cells With complex processes/"feet" that wrap around specialized dense layer of glomerular capillaries

What are filtration slits?

Narrow gaps between adjacent pedicels. Materials passing out of blood at glomerulus must be small enough to pass b/w filtration slits

The glomeruli are capillaries of what arterioles and form what?

The glomeruli are capillaries of afferent arterioles, which form a small cluster (tuft) within the visceral layer of Bowman's capsule

What are present in the endothelium of the capillaries of the afferent arterioles?

Fenestration! - Gaps in the endothelium - For filtration

Function of podocytes

Filtration, maintenance of the glomerular basement membrane (GBM), shape and integrity of the capillaries and in signal transduction

What is the brush border on the proximal tubule for?

Increases SA = for reabsorption

What lines the proximal convoluted tubules, distal convoluted tubules and collecting ducts?

Simple cuboidal epithelium

What lines the thin segments of the loops of Henle?

Simple squamous epithelium

What is present on the epithelium of the proximal tubule?

Brush borders for reabsorption

What is the distal tubule involved in?

Involved in ion exchange - X much absorption so X brush borders - Simple cuboidal epithelium

Basement membrane

- Charged - Small molecules can pass through - Larger molecules that are charged X pass through - If molecules larger than gaps then def X go through (e.g. RBCs, proteins)

What are juxtaglomerular cells?

Modified smooth muscle cells that secrete renin - In afferent arteriole

What do the cells of the macula densa detect?

Concentration of sodium in tubular fluid

What does the juxtaglomerular apparatus include?

- Macula densa - Juxtaglomerular cells - Extraglomerular mesangial cells (mesangium)

What is the macula densa a part of?

Distal convoluted tubule

What are the two main types of nephrons in the kidney?

- Cortical nephron (85%) - Juxtamedullary nephron (15%)

What does the collecting system include?

- Minor calyces - Major calyces - Renal pelvis

Where does urine from the renal papillae drain into?

Drains into the minor calyces which join to form major calyces

What is the ureter?

Muscular passage for urine from kidney to urinary bladder - Continues from the renal pelvis - Conveys urine to urinary bladder

Where does the ureter cross?

Crosses the pelvic brim in front of the sacroiliac joint - Where the common iliac artery divides into ext. & int. iliac arteries

What does the wall of the ureter contain?

Smooth muscle

What is the ureter lined by?

Transitional epithelium (urothelium)

Where does the renal calculi pass through?

Passed along the ureter - Produce pain which is carried by sensory nerves to T10-L2 segments of spinal cord

Where is renal pain referred to?

Loin & groin - Corresponds with dermatomes T10-L2

What is the urinary bladder lined with?

Transitional epithelium = stretches as bladder fills

What is the detrusor?

Smooth muscle of urinary bladder

What happens when urine is filling up?

- Detrusor relaxes = can expand = inc. vol. - Internal sphincter contracted - Sensation of urine = stimulates stretch receptors of bladder

Is there reabsorption beyond the renal pelvis?

Is the external urethral sphincter smooth or skeletal muscle?

Skeletal muscle = Can control

Is the internal urethral sphincter smooth or skeletal muscle?

Smooth muscle = cannot control

Which are the pelvic splanchnic nerves?

S2-S4

What do the pelvic splanchnic nerves carry?

Parasympathetic nerve fibers - have cell bodies = originate from the sacral segments of the spinal cord (S2-S4)

Effect of the pelvic splanchnic nerves on the detrusor muscle & internal urethral sphincter

Stimulate the detrusor muscle to contract/relax Stimulate internal urethral sphincter to contract/relax

What is the pudendal nerve?

- From the sacral plexus - Mixed spinal nerve = both sensory & motor fibers - Stimulate skeletal muscles in the external urethral sphincter to contract

How is the detrusor muscle stimulated to relax?

- Stretch receptors signals to the sensory neurons - Signal travels back to dorsal root ganglion - Motor neurons signals to the detrusor muscle to relax - Detrusor muscle relaxes & bladder allowed to expand - Motor neurons also signals internal sphincter to contract

Where is angiotensin I converted?

in the lungs - Converted to angiotensin II

Where is angiotensinogen produced?

Liver

What does the zona glomerulosa of the suprarenal gland produce?

Aldosterone

What does the renin-angiotensin-aldosterone system (RAAS) do when blood pressure/volume is low?

- Kidneys release renin - Renin converts angiotensinogen to angiotensin I - Angiotensin I converted to angiotensin II in the lungs by the angiotensin-converting enzyme (ACE) - Angiotensin II causes vasoconstriction & stimulates adrenal glands to release aldosterone - Aldosterone causes kidney to retain sodium & water = inc. bld vol. & pressure

What does angiotensinogen travel through to the heart?

Hepatic veins --> inferior vena cava --> heart

What does aldosterone travel through to the heart?

Suprarenal veins --> inferior vena cava --> heart

How does angiotensin II travel to the kidneys (to stimulate aldosterone release)?

From lungs --> pulmonary veins to heart --> aorta --> suprarenal arteries

How many layers of the cortex of the suprarenal gland?

What does the zona glomerulosa secrete?

Mineralocorticoids --> e.g. aldosterone

What does zona fasciculata secrete?

Corticosteroids --> e.g. cortisol

What does the zona reticularis secrete?

Androgens

What does the medulla of the suprarenal gland secrete?

Cathecholamines (e..g adrenaline) = response to stress = produce 'fight-or-flight' response

What is the epithelium lining the - renal calyces - renal pelvis - ureter - urinary blader called?

Transitional epithelium