Urinary System Flashcards
Organs it consists of
The kidneys, ureters, bladder and urethra
Function
Maintains homeostasis by m managing the volume and composition of fluid reservoirs, primary blood
Kidney functions
Regulation of blood ionic composition Na+, K+ and CI- Regulation of blood pH H+, HCO-3 Regulation of blood volume. H2O Regulation of blood pressure Production of hormones Regulation of blood glucose level
Internal renal anatomy
Renal cortex ( Outer Lauer ) Renal Medulla ( Inner region ) Renal Pyramids Renal Columns Papillary ducts ( empty urine into calyces )
Blood and Nerve supply to Kidney
Blood Supply: They receive 20-25% of resting cardiac output
Nerve Supply: Renal nerves primarily carry sympathetic outflow
Regulate blood flow through the kidneys
The Nephron
Renal Corpuscle filters the blood plasma
Renal tubule modifies the filtrate
Renal Corpuscle parts
- Glomerulus is the mass of capillaries
2. Bowman’s capsule has a visceral layer of podocytes which wrap around the capillaries
filter blood
Plasma goes in afferent arteriol e
blood cells and protien stays in
Remaining stuff gets filtered out
and down the proximal convoluted tubule
Renal Corpuscle
The glomeruli endothelial cells have large pores and are leaky. ( pink cells surrounding afferent arteriole )
Basal Lamina lies between the endothelium and podocytes
Podocytes form pedicels between are the filtration slits
Filtration in renal tubule
passes from glomerulus into bowman and into renal tubules, proximal covulated tubule
nephron loop, deascednig and ascending
Then becomes the distal convoluted tubule and then the collecting duct
The juxtaglomerular
Ascending loop contacts the afferent arteriole at the macula dense
Wall of the arteriole contains smooth muscle cells
The apparatus regulates blood pressure in the kidney in conjunction with the ANS
The distal; collecting tubule and collecting duct
Principal cells: Receptors for ADH and aldosterone ( In Distal convoluted tubules )
Allows water to be reabsorbed into the body from kidney tubules, found in distant convoluted tubules, collecting duct and in proximal
Intercalated Cells: Help to manage blood pH
by excreting hydrogen or bicarbonate
Two kinds of nephrons
Cortical and Juxtamedullary nephrons
Juxtamedullary nephrons
Long nephron loops deep in Medulla
Receive blood from pertubular capillaries and vasa recta
Ascending limb has thick and thin regions
Enable kidneys to secrete very concentrated urine
Cortical nephrons
80-85% of nephrons
Renal corpuscle In outer of cortex
Short loops of Helene extend only into outer region of medulla
Create urine with osmolarity similar to blood
Urine formation
3 stpes
Glomerular filtration : Fluid comes out of glomerulus into proximal convoluted tubule
Tubular reabsorption: Blood reabsorbed materials from kidney tubules, most of filtrate is reabsorbed into the blood
Tubular secretion: Occurs primarily in the ladder end of tubules, takes material from blood and dumps it into renal tubules mostly by active transport
Excretion = glomerular filtration + secretion - reabsorption
Glomerular Filtration
Driven by blood pressure
Opposed by capsular hydrostatic pressure and colloid osmotic pressure
water and small molecules move out of glamorous
In one day 150-180 liters of water pass out into the glomerular capsule
Glomerular filtration rate
Amount of filtrate formed by both kidneys each minute
averages 105- 125 mL/min
If GFR is too high substances pass too quickly and are not reabsorbed
If GFR too low all reabsorbed and some waste products not adequately excreted
Controlled by:
Renal Autoregulation
Neural Regulation
Hormonal Regulation
Renal Autoregulation
Consists of smooth muscle cells in the afferent arterioles contracting when blood pressure is too high
= expand and contract and less blood passes into glomerulus
Tubuloglomerular feedback then occurs
High rate of filtration diminished reabsorption. So the macula densa senses too much material and releases nitric oxide and the arterioles constrict
Neural Regulation
Kidneys are richly supplied by sympathetic fibers
Strong stimulation makes afferent arterioles constrict and urine output id reduced
Hormonal Regulation
Angiotensin II: constricts afferents and efferents, diminishing GFR
Atrial Natriuretic peptide : increases GFR and increases urinary output
ANP is secreted in response to stretch of the cardiac atria
Tubular reabsorption & Secretion
Much of filtrate is reabsorbed. H2o,glucose,amino acids, and ions (mostly in proximal convulated tubule )
Secretion: Helps manage pH and rid the body of toxic and foreign substances
Reabsorption routes
Paracellular reabsorption: Passive fluid leakage between cells
Transcellular reabsorption: Directly through the tubule cells
Water reabsorption
90% is obligatory : water follows the solutes that are reabsorbed
10% is facultative water reabsorption
