urinary system Flashcards
Anatomy of Urinary System
- ureter - most proximal
- urinary bladder
- urethra - most distal
- transport and store
- kidneys - main organ for filtration, reabsorption and secretion
- kidneys are retroperitoneal
- renal cortex = all filtration
- renal medulla = urine concentration and volume
- golmerulus = filtration (no gas exchange)
- afferent arteriole = artery into glomerulus
- peritubular capillaries = reabsorption and secretion
Renal Functions
H+ = acidic HCO3 = basic
1) Filtration (out of blood)
- in the renal cortex
- moves from blood into renal tubules
- filters water, electrolytes, urea, glucose, amino acids
- does NOT filter protein, blood cells
- kidney damage = protein and cells in the urine
* increase filtration of H+ = alkalosis
* increate filtration of HCO3 = acidosis
- The renal filtrate passes from the glomerulus into Bowman’s capsule and contains no blood cells and few blood proteins.
- Filtration pressure is responsible for filtrate formation.
2) Reabsorption (into blood)
- in the proximal convoluted tubules, loop of henle
- water, sodium, glucose, amino acids
- from renal tubules back into the blood
* increase reabsorption of H+ = acidosis
* decrease reabsorption of HCO3 = acidosis
- About 99% of the filtrate volume is reabsorbed; 1% becomes urine.
- Proteins; amino acids; glucose; fructose; and sodium, potassium, calcium, bicarbonate, and chloride ions are among the substances reabsorbed.
- About 80% of the volume is reabsorbed in the proximal tubule and descending limb of the loop of Henle. About 19% is reabsorbed in the distal tubule and collecting duct.
3) secretion (out of blood)
- occurs in the loop of handle and distal convoluted tubules
- from blood back into the tubules
- anything that wasn’t filtered out gets secreted
- amonia, urea, creatinin, ions (hydrogen (acidic)), potassium (secreted when Na+ is reabsorbed)
* decrease secretion of H+ = acidosis
* increase secretion of HCO3 = acidosis
- Hydrogen ions, some by-products of metabolism, and some drugs are actively secreted into the nephron.
hormonal regulation of urine volume
*** Renin Aldosterone Angiotensis System (RAAS), ADH, ANH
1) aldosterone
increase the amount of salt (sodium) reabsorbed into the bloodstream and the amount of potassium removed in the urine. Aldosterone also causes water to be reabsorbed along with salt; this increases blood volume and therefore blood pressure. Thus, aldosterone indirectly regulates blood levels of electrolytes (sodium, potassium and hydrogen) and helps to maintain the blood pH
2) ADH (anti-diueretic hormone)
Its most important function is to conserve the fluid volume of your body by reducing the amount of water passed out in the urine. It does this by increasing the permeability of a specific region of the kidney through which urine flows. Thus, more water returns to the bloodstream, urine concentration rises and water loss is reduced. Higher concentrations of anti-diuretic hormone cause blood vessels to constrict (become narrower), which causes an increase in blood pressure. The deficiency of body fluid can only be finally restored by increasing water intake.
- ADH is secreted from the posterior pituitary when the concentration of blood increases or when blood pressure decreases. ADH increases the permeability to water of the distal convoluted tubule and collecting duct. It increases water reabsorption by the kidney.
3) ANH (atrial naturetic hormone)
in response to increases in blood pressure, acts on the kidney to increase sodium and water loss in the urine.
4) renin
- Renin is secreted from the kidney when the blood pressure decreases or when the concentration of sodium ions decreases in the blood. Renin converts angiotensinogen to angiotensin I which is then converted to angiotensin II by angiotensin-converting enzyme. Angiotensin II stimulates aldosterone secretion, and aldosterone increases the rate of sodium chloride reabsorption from the nephron.
renal pelvis
- most occurrence of kidney stones get stuck here because of the curvature
renal artery
- kidneys can end up killing other organs because it demands so much blood
- 20-25% of all cardiac output runs through the kidney
- kidney demands blood for volume, PH, electrolytes
UTIs
- women at higher risk because: shorter urethra, proximity to anus, and the prostate secretes antibiotics that kill UTI bactera almost always in men
- occur in the trigone
- cysitis = bladder infection
- ecoli causes UTI
urine pathway
renal pyramid –> renal papilla –> minor calyx –> major calyx –> renal pelvis
Nephron
- functional unit of the kidney
- cortical nephrons: loop of hence is smaller, gloermulus further from cortex-medulla junction, efferent arteriole supplies peritubular capillaries. normal blood filtrate and urine production
- Juxtamedullary nephrons: increase concentration of urine, long loop of hence, glomerulus closer to cortex-medulla junction, efferent arteriole supplies vasa recta
juxtaglomerular apparatus (JGA)
- glomerular filtration membrane has a negative charge that keeps out proteins (which are all mostly negative) so you don’t pee out any protein
- The juxtaglomerular apparatus is a microscopic structure in the kidney that regulates the function of each nephron. The juxtaglomerular apparatus is named for its proximity to the glomerulus: It is found between the vascular pole of the renal corpuscle and the returning distal convoluted tubule of the same nephron. This location is critical to its function in regulating renal blood flow and glomerular filtration rate. The three cellular components of the apparatus are the macula densa of the distal convoluted tubule, smooth muscle cells of the afferent arteriole known as juxtaglomerular cells, and extraglomerular mesangial cells.
1) macular densa:
- “detector”
- pressure and oxygen detection. measures sodium, o2 and BP
- when detects decreased pressure and decreased sodium then renin is released
- measure hypoxia
- kidney is the only place that can measure O2
2) juxtaglomerular cells:
- “secreter”
- secretes renin and EPO stimulated by hypoxia and low BP
renal tubules
- structures of the nephron
1) proximal tubule - major site of reabsorption
2) loop of henle - into medullar, urine concentration and blood volume
3) dista tubule - end secretions, 3 hormones (aldosterone, ANH, ADH)
4) collecting duct - secretion and last time to reabsorb anything
Filtration
- increase in BP/Hypertension = too much filtration
Effective Filtration Pressure & Glomerular Filtration Rate
1) Glomerular Hydrostatic Pressure - push out of glomerulus into bowman’s capsule.
- increase BP
- most important and strongest
- increase in BP = increase in GHP
2) Glomerular Osmotic Pressure - pull into glomerulus from bowman’s capsule
- protein and albumin
- 2nd most important
- liver disease when decreased albumin
- decrease in ablumin = increase in glomerular osmotic pressure
3) Capsular Hydrostatic Pressure - push from capsule into glomerulus
- obstruction in nephron increases capilary hydrostatic pressure
- pyelonephritis
4) capsular osmotic pressure - pull into capsule from glomerulus
- very weak force, negligible
- increase pressure from kidney stones = increase COP
reabsorption
- tubule into blood
- proximal convoluted tubule
- movement of electrolytes out of various segments of the rubble back into the blood
- water, electrolytes (sodium, k+, chlorine, magnesium, calcium) glucose, amino acids enter the peritubular blood vessels
- needs ATP because it is active (Na+) and passive (H2O)
- countercurrent exchange affects urine concentration
secretion
- from blood into tubule
- movement of substances from peritubular blood and renal tissues into renal tubule for removal in urine
- secretion of H+, K+, nitrogen, amonia, and urea
concentration and dilution of urine
- urea - should beg in urine
- aldosterone - PCT
- ADH - opp of aldosterone, collecting duct
- ANH - opp aldosterone
- diuretics - opp ADH
angiotensin 2 effects
- systemic vasoconstriction
- increased aldosterone secretion from renal cortex
- increaesd ADH secretion
- increased thirst
- increased BP
- increased blood volume
- hypothalamus increased thirst which increases blood volume
- posterior pituitary secretes ADH which increases H2O reabsorption which increases blood volume and icnreases BP
pathologies
- endothelial dysfunction
- decreased apoptosis = cancer
- atherosclerosis
- increase thrombosis
- increased platelet aggregation
acute rangiotensin 2 is good, chronic = death
