Urinary System Flashcards
How is water gained in the body?
- food
- drink
- metabolic water
How is water lost?
- urination
- defacation
- evaporation (breath and sweat)
Function: kidneys
Produce urine
Function: ureters
Transport urine to bladder
Function: bladder
Stores urine
Function: urethra
Passes urine to the outside
Function: renal cortex
Filters the blood
Function: renal medulla
Concentrates the filtrate
Where does urine enter the bladder from?
From below
How does urine get transported from kidneys to bladder?
Urine from renal pelvis stretches ureters
Peristalsis wave
Involuntary control of urination
- stretch receptors in bladder wall activated
- signals travel to sacral spinal cord
- motor nerves cause contraction of bladder and relaxation of internal sphincter
What are the parts of the nephron?
Renal corpuscle (glomerulus and bowmans capsule) Proximal convoluted tubule Loop of Henle Distal convoluted tubule Collecting duct
Flow of filtrate
Nephron - papillary duct - minor calyx - major calyx - renal pelvis
What is glomerular filtration?
Creates a plasma like filtrate of the blood
What is tubular reabsorption?
Removes useful solutes from the filtrate and returns them to the blood
What is tubular secretion?
Removes additional wastes from the blood and adds them to the filtrate
What is water conservation?
Removes water from the urine and returns it to the blood, concentrates filtrate
Why does the afferent arteriose have a larger diameter than the efferent arteriole?
Generates a large hydrostatic pressure forcing solutes out of the blood and into the filtrate
What three layers must something entering the filtrate pass through?
- endothelium of glomerular capillaries (filtration pores)
- basement membrane
- filtration slits between the podocyte cell extensions
Bowmans capsule structure
- parietal layer: simple squamous epithelium
- visceral layer: podocytes which wrap around the capillaries
- capsular space: between two layers, filtrate collects here
What does not pass through the filter?
- blood cells
- plasma proteins
- large anions
What is proteinuria?
Protein in urine
What is hematuria?
Blood in urine
Proximal convoluted tubule structure and function
- simple cuboidal epithelium with microvilli
- absorption
Thin loop of henle structure and function
- simple squamous epithelium
- very permeable to water so water moves out
Thick loop of henle structure and function
- simple cuboidal epithelium with many mitochondria
- active transport of salts out of filtrate
Distal convoluted tubule epithelium
Simple cuboidal with no microvilli
Transport maximum
Renal threshold
What does ADH do and where does it act?
Increases water permeability of DCT and CD
What is the stimulus for ADH?
- increase of blood osmotic pressure
- decreases in blood volume
What is diabetes insipidus?
Lack of ADH
What is the function of the change in concentration (osmotic pressure) from cortex to medulla in humans?
- concentration gradient increases from 300mOsmol/L to 1200mOsmol/L across the medulla
- when filtrate travels through the medulla, water in the CD can be pulled out of the filtrate by the higher osmotic pressure in the sureounding interstitial fluid providing that the collecting duct is permeable to water
What does the anatomy of the human kidney (cortical length vs medullary length) tell you about the type of environment that humans evolved in?
- Human have a quite deep medulla
- humans can concentrate their urine
- humans can to some extent deal with fairly dry environments, but are not as well adapted as desert mammals
- fossils have been found near lakes (access to water) but humans would have had to move away from water source to hunt and collect food
How does ADH reduce the volume of urine?
- increases permeability of DCT and CD to water
- water is able to move along its concentration gradient out of the nephron
- this concentrates urine, and hence decreases volume
How does alcohol increase the volume of urine?
- drop in ADH decreases permeability of CD and DCT to water
- more water is retained in the filtrate
- increases volume of urine
