Urinary System Flashcards
What organ creates urine?
Kidney
T/F: if you’re dehydrated enough, your kidneys won’t produce urine
FALSE: obligate urine production
What are other functions of the kidney aside from urine production?
Control blood volume/BP, pH, hormone production, vit D metabolization (Ca++ reuptake)
What hormones are produced in the kidneys?
Renin (BP regulator), Erythropoietin
Describe the position of the kidneys in the thorax
Retro-peritoneal; posterior to the peritoneal cavity
What protects the kidneys?
Relatively little compared to the rest of the thoracic organs; surrounded by fat to provide shock absorption
What is the functional unit of the kidney?
Nephron
What is the glomerulus?
Specialized (fenestrated) capillary bed at the beginning of a nephron; site of filtration of blood
What is the renal tubule?
Location in a nephron where blood filtrate becomes urine
Describe blood flow through the kidney
Enters through renal artery, afferent arteriole->glomerular capillaries, exits glom cap thru efferent arteriole->peritubular capillaries to venule to renal vein… PORTAL SYSTEM
What are the steps in urine formation?
1: Glomerular filtration
2: Tubular Reabsorption
3: Tubular Secretion
What is glomerular filtration?
Filtration of liquid out of the glomerular capillary and into the renal tubules of the kidney
What structure captures glomerular filtrate BEFORE entering the renal tubule?
Bowman’s capsule
What pressures affect GFR (glomerular filtration rate)?
Glomerular hydrostatic pressure (pressure pushing fluid out, glom.->capsule); colloid osmotic pressure (plasma proteins, pull fluid back in); bowman’s capsule hydrostatic pressure (pushing fluid back in, capsule->glom.)
What happens to glomerular hydrostatic pressure when the afferent arteriole constricts?
Decreases; less blood flow into the glomerulus means less pressure
Describe the interactions of pressures around the glomerulus
Opposing pressures; GHP wants to push fluid out of the capillary, COP wants to pull fluid back into the capillary, BCHP wants to push fluid back to the capillary
What are the cells of the bowman’s capsule?
Podocytes; wrap around glomerular capillary, filtrate can escape capillary through filtration slits (space between podocyte arms)
What can escape the capillary through fenestrations and filtration slits?
Everything in the plasma EXCEPT blood cells and proteins (restricted by basal lamina/basement membrane)
What unit is responsible for urine formation?
Nephron; about 1 million of them in each kidney!
How much urine is filtered daily?
About 200L of blood -> 1-1.5L urine/day
