Exam 2 Flashcards
Urinary system components and functions
- Kidneys: form urine
- Ureters: deliver urine to bladder
- Bladder: stores urine
- Urethra: expels urine from body
renal anatomy
- Kidneys are retroperitoneal and protected by lower ribs and adipose tissue
- Renal hilum: indented area that’s an entrance for renal artery, renal vein, ureter, nerves, lymphatics
External layers of renal anatomy: has connective tissue (superficial to deep)
- Renal fascia: anchors kidneys to other structures
- Adipose capsule: protects kidneys
- Renal capsule: adheres to kidney surface and protects spread of infection
Internal renal anatomy:
- Renal cortex: highly vascularized outer layer of kidneys with granular appearance
- Renal medulla: inner region used to creates concentrated urine
- Renal pyramids: urine-secreting apparatus and tubules
- Renal columns: anchors cortex
Cortical nephron:
- short loops of Henle that only extend to medulla’s outer region
- Renal corpuscle in outer portion of cortex
- Creates dilute urine with osmolarity similar to blood
- If hydrated ⇒ cortical dilutes water since there’s enough to spare
Juxtamedullary nephron:
- long loops of Henle that goes deep in medulla
- Renal corpuscle deep in cortex
- Receives blood from peritubular capillaries and vasa recta
- Ascending limb has thick and thin regions
- Enables kidneys to secrete very concentrated urine
- If dehydrated ⇒ juxtamedullary retains more water
What are the 2 parts of the renal corpuscle
- glomerulus
- glomerular (bowman’s) capsule
what is the glomerulus and what are the 3 layers of filtration?
- mass of capillaries that’s fed by afferent arteriole and drains to efferent arteriole
1. Glomerular endothelial cells: have fenestration (large pores) that are leaky = allowing for stuff from blood plasma to move in/out
2. Basement membrane: prevents filtration of larger proteins
3. Slit membrane between pedicels: prevents filtration of medium-sized proteins
what is the Glomerular (Bowman’s) Capsule and its function?
- has visceral layer of podocytes that wrap around capillaries
- Filtrate collected between visceral and parietal layers
Juxtaglomerular Apparatus
- region where ascending loop makes contact with afferent arteriole at macula densa
- arteriole walls have granular cells
- Regulates blood pressure in kidneys with help of autonomic nervous system
Renin-Angiotensin-Aldosterone System
Low salt levels ⇒ lowers blood volume b/c of inhibition of ADH secretion ⇒ pee more ⇒ less water reabsorbed in CT and more excreted in urine ⇒ lowered blood volume detected by granular cells that secrete renin to afferent arteriole ⇒ converts angiotensin → angiotensin I ⇒ angiotensin-converting enzyme (ACE) converts angiotensin I → angiotensin II ⇒ stimulates adrenal cortex to make aldosterone that stimulates K+ excretion and Na+ H2O reabsorption from CT ⇒ increases water reabsorption ⇒ increases blood volume and raises blood pressure
Glomerular Filtration + Secretion – Reabsorption = Excretion of Solute
- Glomerular filtration: blood plasma and dissolved substances get filtered in glomerular capsule
- Tubular secretion: happens along renal tubule and CT where substances and excess ions get secreted from peritubular capillaries to renal tubule to be excreted in urine
- Tubular reabsorption = happens along renal tubule and CT where water, ions, substances get reabsorbed from renal tubule to peritubular capillaries to be in blood
Glomerular filtration:
- Driven by blood pressure
- Opposed by capsular hydrostatic pressure and blood colloid osmotic pressure
- Capsular hydrostatic pressure: pressure of the fluid inside a capsule space
- Blood colloid osmotic pressure: amount of proteins in blood
- More proteins in blood than glomerulus space ⇒ opposes b/c it would want to drive things back into blood
- Water and small molecules move out of glomerulus
Glomerular filtration rate
- amount of filtrate formed by both kidneys each minute
- Homeostasis requires kidneys to maintain relatively constant GFR
- High GFR ⇒ substances pass too quickly and aren’t reabsorbed ⇒ higher BP
- Low GFR ⇒ almost all substances reabsorbed and some waste products not adequately excreted ⇒ lower BP
what are the 3 ways the kidneys are regulated?
- autoregulation (myogenic and tubuloglomerular)
- neural
- hormonal
2 types of autoregulation
- Myogenic mechanism:
- High BP ⇒ smooth muscle cells in afferent arterioles contract (b/c high BP means filtrate substances pass too fast and aren’t reabsorbed)
- Low BP ⇒ smooth muscle cells in afferent arteriole dilate (b/c low BP means almost all filtrate substances reabsorbed and barely any secreted)
- Tubuloglomerular feedback:
- High GFR ⇒ no reabsorption ⇒ macula densa inhibits release of nitric oxide (vasodilator) ⇒ afferent arterioles constrict
Neural regulation
strong sympathetic stimulation ⇒ afferent arterioles constrict ⇒ reduced urine output ⇒ more blood available for other organs
Hormonal regulation
- High GFR?
- High BP?
-High GFR ⇒ angiotensin II constrict afferent and efferent arterioles ⇒ decreases GFR
- High BP ⇒ Atrial natriuretic peptide (ANP): released in response to stretch of cardiac atria when BP is too high and relaxes mesangial cells in glomerulus ⇒ increases capillary surface area ⇒ low BP
Angiotensin II:
- stimulates adrenal cortex to make aldosterone
- constricts afferent and efferent arterioles
Aldosterone
stimulates K+ excretion and Na+ reabsorption which also reabsorbs H2O because it follows Na+
ADH
stimulates insertion of aquaporins in CD ⇒ increases H2O reabsorption to peritubular capillaries
ANP: atrial natriuretic peptide
during High BP ⇒ inhibits secretion of aldosterone and ADH ⇒ suppresses reabsorption of Na+ and H2O in PCT and CD ⇒ increases excretion of Na+ in urine ⇒ increases urine output ⇒ decreases blood volume and BP
PTH
stimulates opening of Ca2+ channels in DCT ⇒ increases reabsorption of Ca2+
Renin
converts angiotensinogen → angiotensin I