The Urinary System Flashcards
Organs of the Urinary System:
Two Kidneys
two Ureters
The Urinary Bladder
THe Urethra
What are the functions of the kidneys?
-filter blood and excrete toxins
-regulate blood volume, pressure, and osmolarity via H2O out put
-regulate acid-base and electrolytes
-secrete erythropoietin
-regulate calcium homeostasis
- clear hormones and drugs from system
detox radicals
- in cases of starvation, help support blood glucose levels
What are the major nitrogenous waste and their sources?
Ammonia - toxic and come from liver.
Urea - liver converts ammonia to urea, which is less toxic.
Uric Acid - produced by catabolism of nucleic acids and creatine phosphate.
Creatinine -produced by catabolism of nucleic acids and creatine phosphate.
What is excretion and the systems used in excretion?
Excretion is the process of separating wastes from the body fluids and eliminating them. 4 organ systems are involved: -resp. system excretes -integumentary system -digestive system -urinary system
Where is the location of the kidneys?
located against the posterior abdominal wall at the level vertebrae T12 to L13. The right kidney is a little lower because of the liver.
What is the appearance of the kidneys?
They are about the size of a bar of soap. Laterally convex and horizontally concave. They have a slit called hilum where the renal veins/arteries enter.
What are the external features of kidneys?
Renal fascia - immediately deep to the parietal peritoneum.
Perirenal fat capsule - cushions kidneys and holds in place
Fibrous capsule - protects from trauma and infection
What are the three regions of the kidneys?
Cortex, Medulla (pyramids and columns), Renal sinus.
What is the blood flow through the kidney?
abdominal aorta, renal artery, segmental artery, arcuate artery, cortical radiate artery, afferent arteriole, glomerulus, efferent arteriole, peritubular cap./vasa recta, cortical radiate vein, arcuate vein, interlobar vein, renal vein, and IVC.
What is the flow of fluid (urine) through kidneys?
Glomerulus, glomerular capsule, PCT, loop of henle, DCT, collecting duct, papillary duct, minor calyx, major calyx, renal pelvis, ureter, urinary bladder, and urethra.
Contrast the juxtamedullary nephrons and the cortical nephrons.
juxtamedullary nephrons - close to medulla, very long nephron loops that extend as far as the apex of renal pyramid.
cortical nephrons - farther from medulla, have short loops that dip just into the outer layer of medulla before turning back.
Describe the nerve supply to the kidney.
Renal plexus - nerve and ganglia wrapped around each renal artery that branch inside kidney.
—Sympathetic innervation - stimulates glomerular blood flow and rate of urine production.
responds to falling BP by simulating the kidneys to secrete renin.
—Parasympathetic — unknown functions
How do kidneys filter blood plasma?
- Glomerular filtration - creates a plasmalike filtrate of the blood.
- Tubular reabsorption - removes useful solutes from the filtrate, and returns them to blood.
- Tubular secretion - removes additional wastes from the blood and adds them to the filtrate.
- Water conservation - removes water from the urine and returns it to blood and concentrates waste.
The relevant cellular structure of the glomerulus.
Fenestrated Glomerular Capillaries - cells are honeycombed with large pores.
The Basement Membrane - have proteoglycan gel.
Filtration Slits - podocyte cells have arms that wrap around capillaries to form a barrier with slits.
Explain the forces that promote and oppose filtration.
PROMOTES-
Blood hydrostatic pressure (BHP) - 60mm Hg
OPPOSE-
Capsular hydrostatic pressure - 18 mm Hg
Blood Colloid Osmotic Pressure (COP) - 32 mm Hg
Filtration Pressure calculation
60 out - 18 in - 32in = 10 mm Hg out
What is the glomerular filtration rate (GFR)?
it is the amount of filtrate (the fluid in any part of a nephron) formed per minute by the kidneys.
How does GFR relate to the amount of reabsorption and urine formation?
Based on total surface area available for filtration, filtration membrane permeability, and net filtration pressure (NFP).
How do the nephron itself (renal autoregulation) regulate filtration?
2 types:
Myogenic mechanism - based on smooth muscle contraction when stretched.
Tubuloglomerular Feedback - macula densa of JGA responds to changes in NaCl and adjust filtration rate.
How do the nervous system regulate filtration?
Stimulated by strenuous exercise or shock. Redirects blood flow and reduces filtration rate.
How do the hormones regulate filtration?
Renin-Angiotensin-Aldosterone Mechanism
- Starts with Baroreceptors detects drop in BP.
- Sympathetic trigger release of renin.
- Renin converts angiotensinogen to angiotensin l.
- ACE converts angiotensin l to angiotensin ll.
- stimulates adrenal cortex to make Aldosterone.
How do the renal tubules reabsorb useful solutes from the glomerular filtrate and return them to the blood?
Transcellular route- substances pass through cytoplasm
Paracellular route - substances pass through gaps between the cells.
Sodium chloride is key to almost everything. it creates osmotic and electrical gradients.
ATP is used as secondary active transport for the Na+ and P+ pump.
Maximum Transport and the issues with it:
The amount of solute that renal tubules can reabsorb is limited by the number of transport proteins. If there is an excess of solutes it can pass into urine.
How do the tubules secrete solutes from the blood into the tubular fluid?
Renal tubules extract chemicals from the capillary blood and secrete them into tubular fluid.
ACid- base balance - by secreting Hydrogen ions and retain bicarbonate.
Waste in blood - via uric acid secretion.
Clearance of drugs and contaminates.
The nephron loop
What are the actions of aldosterone?
The salt retaining hormone.
Triggers aldosterone secretion
Reabsorbs sodium and recreation of potassium.
Water follows the sodium.
What are the actions of atrial natriuretic peptides?
Secreted by hearts atrium.
Caused by high BP.
Dilates afferent arteriole and constricts efferent arteriole.
Inhibits renin and aldosterone secretion.
Inhibits secretion of ADH.
What are the actions ADH?
Secreted by POST. PIT.
Triggers are dehydration, loss of blood volume, and rising blood osmolarity.
ADH makes collecting duct more permeable to water.
What are the actions of parathyroid hormone?
Secreted in response to calcium deficiency.
increase phosphate excretion
increases calcium reabsorption
Stimulates calcitriol synthesis
How does the nephron regulate water excretion?
The nephron controls water by movement of sodium chloride in and out of the filtrate and the water will follow sodium depending on the osmotic gradient.
How do the kidney maintains an osmotic gradient in the renal medulla that enables the collecting duct to function?
In the inner medullary collecting ducts it increases both water and urea permeability, which allows urea to flow passively down its concentration gradient into the interstitial fluid.
Explain how the collecting duct and antidiuretic hormone regulate the volume and concentration of urine.
ADH determine how much water will leave the collecting duct.
Describe the osmotic gradient in the renal medulla.
The osmotic gradient is saltier in the medulla compared to the cortex. The further down blood goes the saltier it becomes thus causing water to exit out of capillaries. Once the blood is leaving the capillaries salt leave (it goes back up becoming less salty) and water enters into the capillaries again.
If ADH is not present how does it effect the medulla and collecting ducts?
Produce very diluted urine.
ADH is present.
Produce very concentrate urine.
What is the composition/properties of urine?
APPEARANCE-
clear to deep amber color. Based on water concentration.
The yellow color is do to urochrome from the breakdown of hemoglobin
ODOR-
bacteria degrade and some foods
Specific gravity- compared to distilled water
Osmolarity - the amount of solutes
Composition- 95% water 5% other solutes
What are the four forms of diabetes?
DIABETES MELLITUS- type 1, type 2, and gestational.
DIABETES INSIPIDUS- effected by ADH.
What are some common diuretics?
A diuretic is a chemical that increases urine volume.
Common diuretics:
Caffeine increases GFR
Alcohol inhibits ADH
What are the functional anatomy of the ureters.
Tubes that extend from each kidney to the urinary bladder.
25cm long
pass posterior to bladder and enter in from below
flap of mucosa at entrance acts a s a valve.
3 Layers-
Adventitia
Muscularis
Mucosa
What are the functional anatomy of the urinary bladder?
Collapsible muscular sac that stores urine.
3 layers:
adventitia
muscularis: detrusor muscle- 3 layers smooth muscle
mucosa- transitional (change shape)
INSIDE
trigone- triangular area where urine fills up
What are the functional anatomy of the male and female urethra?
FEMALE- 3-4 cm long behind urethra is vagina external sphincter-voluntary control MALE- 18 cm long prostatic urethra 2.5 cm membranous urethra .5 cm spongy (penile) urethra 15 cm Internal urethra sphincter external urethra sphincter
Voiding of Urine
Sympathetic nervous system:
causes detrusor muscle to relax
internal urethra constricts.
Somatic motor fibers:
allows voluntary control of external sphincter.
The stretch receptors detects the filling of bladder and send signals to parasympathetic system.
The contracts the detrusor sphincter and relax internal sphincter.
