urinary system Flashcards
what are the functions of your Kidney?
- removal of toxins, metabolic waste, and excess ions from the blood
- regulation of blood volume, chemical composition, pH
- Regulate blood Vol and Pressure
What is Gluconeogenesis?
formation of new glucose from glycerol and amino acids
what is erythropoietin?
regulation of RBC production
What is Renin?
Regulation of blood pressure and kidney function
What are the components of nitrogenous waste?
Uric acid, ammonia, urea, creatine
what is waste?
any substance useless to the body or present in excess body’s needs
what is metabolic waste?
waste substance produced by the body
what is the process of urea formation?
proteins -> amino acids -> NH2 removed -> forms ammonia -> liver converts ammonia to urea
What is uric acid?
It is the product of nucleic acid catabolism
what is creatine?
product of creatine phosphate catabolism
what does it mean that kidney’s are retroperitoneal?
it means that they are located behind the peritoneum
what is the renal parenchyma?
Glandular tissue that forms urine
what is the renal sinus?
the cavity that contains blood and lymphatic vessels, nerves, and urine-collecting structure
what are the two zones of the renal parenchyma?
- outer renal cortex
- inner renal medulla
what makes up the renal cortex?
granular superficial regions
what makes up the renal medulla?
the cone-shaped medullary (renal) pyramids separated by renal columns
what is the Papilla?
tip of pyramid; releases urine into minor calyx
what is the major calyces?
the branching channels of the renal pelvis that
- collect urine from minor calyces
- empty urine into the renal pelvis
what does the cortex region do for the kidneys?
Peritubular capillaries branch off of the efferent arterioles supplying the tissue near the glomerulus, tje proximal and distal convoluted tubules
what does the medulla region do for the kidneys?
efferent arterioles give rise to the vasa recta, supplying the nephron loop portion of the nephron
what are juxtamedullary nephrons? and what do they do?
- 15% of all nephrons
- very long nephron loop, maintain salinity gradient in the medulla and help conserve water
- efferent arterioles branch into vasa recta around long nephron loop
what are cortical nephrons? and what do they do?
- 85% of all nephrons
- short nephron loops
- efferent arterioles branch into peritubular capillaries around PCT and DCT
about how many nephrons are in each kidney?
1 million
what is the function of kidneys?
To form urine
what are the two main parts of nephrons? and what do they do?
renal corpuscle: filter the blood plasma
renal tubule: long, coiled tube that converts the filtrate into urine
what is the parietal layer of the glomerular capsule made of?
simple squamous epithelium
what is the visceral layer of the glomerular capsule made of?
elaborate cells called podocytes that wrap around the capillaries of the glomerulus
what are the basic stages of urine formation?
1) Glomerular formation: creates a plasma-like filtrate in the blood
2) tubular reabsorption: removes useful solutes from the filtrate, returns them to the blood
3) tubular secretion removes: additional waste from the blood, adds them to the filtrate
4) water conservation: removes water from the urine and returns it to blood; concentrates wastes
what is allowed to pass through glomerular filtration membrane?
- water
- electrolytes
- glucose
- amino acids
- fatty acids
- vitamins
- urea
- uric acid
- creatinine
what does filtration pressure depend on?
hydrostatic and osmotic pressure on each side of the filtration membrane
what are the forces involved in glomerular filtration?
- colloid osmotic pressure of filtrate = 0mm
- blood hydrostatic pressure = 60mm
- colloid osmotic pressure of blood = -32mm
- capsular pressure = -18mm
what is colloid osmotic pressure of filtrate?
pressure exerted by proteins drawing water into the tubules
- opposing force to hydrostatic pressure
what is blood hydrostatic pressure?
high in glomerular capillaries because afferent arteriole is larger that efferent arteriole: a large inlet and small outlet
what is capsular hydrostatic pressure?
due to high filtration rate and continual accumulation of fluid in the capsule
what is osmotic pressure of blood?
pressure exerted by proteins drawing water into the circulatory system
- it is the opposing force ti hydrostatic pressure
what happens if GFR is too high?
- Fluid flows through renal tubules too rapidly for them to reabsorb
the usual amount of water and solutes
– Urine output rises
– Chance of dehydration and electrolyte depletion - Macula densa detects increased filtrate [NaCl], secretes ATP
– Granular cells respond by constricting afferent arterioles
– Constriction reduces blood flow which corrects GFR
what happens if GFR is too low?
- Wastes are not flitered
– Azotemia may occur (abnormally high levels of nitrogen) - Granular cells also contain granules of renin, which they secrete in
response to drop in blood pressure (mechanoreceptors)
– Participate in the renin-angiotensin-aldosterone system that works to
control blood volume and pressure
what is the Average GFR?
125 ml/min
180 L filtered
1.5 L urine made daily
What are the three homeostatic mechanism that control GFR? and what type of regulatory mechanisms are they?
- renal autoregulation: intrinsic reg
- myogenic mechanism
- tubuloglomerular feedback - sympathetic control: extrinsic reg
- Hormonal control: extrinsic reg
what is renal autoregulation?
- The ability of the nephrons to adjust their own blood flow and GFR without external (nervous or hormonal) control
what happens if arterial BP decreases in the myogenic mechanism?
- Afferent arteriole relaxes
- Afferent arteriole dilates and allows blood to flow more easily into
the glomerulus, so that the flow rate remains similar and filtration remains stable
what is the myogenic mechanism?
Based on the tendency of smooth muscle to contract when
stretched
what happens if arterial BP increases in the myogenic mechanism?
- The afferent arteriole is stretched
- Afferent arteriole constricts and prevents blood flow into the
glomerulus from changing
what is tubuloglomerular feedback?
- Glomerulus receives feedback on the status of downstream tubular fluid and adjusts the filtration rate accordingly
- Regulates filtrate composition, stabilizes kidney performance, and compensates for fluctuations in blood pressure
what is the juxtaglomerular apparatus?
complex structure found at the end
of the nephron loop where it has just reentered the renal cortex
what is the Macula Densa?
cluster of modified epithelial cells of the renal tubule
what are granular cells?
modified smooth muscle cells of the afferent arteriole
what does the sympathetic control do?
- they innervate the renal blood vessels
- constrict the afferent arterioles in strenuous exercise
- reduce GFR and urine output
what effect does hormonal control have on GFR?
- The renin-angiotensin-aldosterone mechanism is a system of hormones that helps control blood pressure and GFR
- drop in BP, baroreceptors in the carotid and aorta stimulate the Symp NS
- release renin
what does angiotensin 2 do?
increases BP
- potent vasoconstrictoror
- stimulates the adrenal cortex
- stimulates posterior pituitary to secrete ADH
- stimulate thirst
how much glomerular filtrate does the PCT reabsorb?
65%
what is one of the most important elements that the PCT reabsorbs? and why
Sodium
- Creates an osmotic and electrical gradient that drives the
reabsorption of water and other solutes
What does the PCT include?
- nonregulated reabsorption
- 70% of NA+ and H2) absorbed
- absorbs glucose
- microvilli present
- mitochondria and leaky tight junctions
what happens during tubular reabsorption?
- Kidneys reduce 180 L of glomerular filtrate to 1-2 L of
urine per day - Two-thirds of water in filtrate is reabsorbed in PCT
- Reabsorption of solutes makes the tubule cells and tissue
fluid hypertonic to tubular fluid
what is the name of the water channels in the tubules?
aquaporins
what is the transport maximum?
- The amount of solute that renal tubules can reabsorb is limited by the number of transport proteins in tubule cells’ membranes
when is the transport maximum reached?
when the transporters are saturated
what is the normal plasma glucose?
80-110 mg/dl
what are the purposes of secretion in PCT and the nephron loop?
- Acid–base balance
- Secretion of varying proportions of hydrogen and bicarbonate ions
helps regulate the pH of body fluids - Waste removal
- Urea, uric acid, bile acids, ammonia, and a little creatinine - Clearance of drugs and contaminants
- morphine, penicillin, and aspirin
what does the loop of henle do?
- creates an osmotic gradient in the renal medulla
- critical in water conservation
what does the distal tubule and the collecting duct include?
- smaller and fewer microvilli
- less mitochondria
- tight tight junctions
- hormone secretion ( if secreted become active)
what hormones are regulated in the DCT and collecting duct?
- aldosterone
- antidiuretic hormone
- atrial natriuretic peptide
what does the fluid arriving in the DCT still contain?
- 20% water
- 7% salts
what are the trigger and functions os aldosterone in the DCT and collecting duct?
Trigger:
- when blood Na+ concentration falls or K+ concentration rises
– a drop in blood pressure > renin release > angiotensin II formation > stimulates adrenal cortex to secrete aldosterone
functions:
- stimulates reabsorption of NA+ and secretion of K+
* Water and Cl- follow the NA+
* The net effect is that the body retains NaCl and water
* Helps maintain bV and BP
what are the trigger and functions os adh in the DCT and collecting duct?
Triggers:
– Dehydration, loss of blood volume, and rising blood osmolarity stimulate arterial baroreceptors and hypothalamic
osmoreceptors
– This triggers the release of ADH from the posterior pituitary
Functions:
– ADH makes the collecting duct more permeable to water
– Water in the tubular fluid reenters the tissue fluid and bloodstream rather than being lost in urine
what are the triggers and functions os anp in the DCT and collecting duct?
Triggers:
– Secreted by atrial myocardium of the heart in response to high
blood pressure
Functions:
1. Dilates afferent arteriole, constricts efferent arteriole: GFR
2. Inhibits renin and aldosterone secretion
3. Inhibits secretion of ADH
4. Inhibits NaCl reabsorption by collecting duct
what does the ability of the kidney s to concentrate urine depend on?
salinity gradient
what is the gradient established and maintained by?
- countercurrent multiplier of loop of Henle
- countercurrent exchange system in vasa recta
- urea recycling
what is the avg urine volume?
1 to 2 L/day
what are the factors of the countercurrent multiplier of Loop of Henle?
- PCT, water reabsorption
- LoH, water reabsorption is not automatically
– Descending limb: water moves out - Permeable to water
- Impermeable to salts
– Ascending limb: salts pumped out - Impermeable to water
- Permeable to salts
what is polyuria?
output > 2L/day
what is oliguria?
output < 500 ml/day
what is Anuria?
0 to 100 ml/day
what is urinalysis?
examination of physical and chemical properties of urine
what is the osmolarity of urine?
blood = 300mOsm/L
what is urine pH?
4.5 to 8.3
what is urines chemical composition?
95% water
5% solutes
what diuretics increase and decrease GFR?
increase: caffeine
decrease: Alcohol
what do the ureters do?
muscular tubes that extend from each kidney to the bladder
what is the bladder?
a muscular sac that stores urine
what is the urethra?
the tube that conveys urine out of the body
what is micturition?
act of urinating
