Urinary System Flashcards
What are the 3 main functions of kidneys?
1) . Kidneys maintain blood/water homeostasis via the production of urine
2) . Kidneys monitor and affect the acid/base balance (by excreting hydrogen ions during acidosis or bicarbonate ions during alkalosis
3). Kidneys secrete;
Renin - which raises blood pressure
Erythropoietin - which accelerates red blood cell production
What is the function of the ureters?
They conduct urine from. kidneys to the bladder, where it is stored
What is the function of the urethra?
The urethra is the passage out of the body (bladder and out)
Where are the kidneys located?
The kidneys lie, one on each side, on the posterior abdominal wall, high up, under the diaphragm
How are the kidneys protected?
They are retroperitoneal - encapsulated and protected by layers of fascia and fairly. firm renal fat
Describe the function of the contents of a kidney and label one?
Cortex (outer portion)
Medulla (inner portion)
- Has renal pyramids which house the nephrons with their function of filtration and reabsorption, projecting into the minor calyces of the collecting system
-The cortex extends between the medullary pyramids as a renal column
The pyramids in medulla open into minor calyces which converge together to form the major calyx, into the renal sinus merging form the renal pelvis at the hilum of the kidney.
The pelvis then becomes the ureter that transports urine to the bladder
What is the functional unit within the kidney and what is its role?
The nephron - it’s where urine production takes place
What are the regions in a nephron and their functions?
- Draw
1) . Renal corpuscle (glomerulus) - Where the blood supply comes in and filtration takes place
2) . Proximal convoluted tubule (PCT)
3) . Loop of Henle - has a descending and ascending limb with a thick and thin part
4) .Distal convoluted tubule (DCT)
5) . Collecting dust - where a number of different nephrons all merge together
What are the 2 types of Nephron and their functions?
1) . Juxtamedullary Superficial;
- Designed to concentrate urine
- Receives 10% of urine supply
- Situated deeper in the kidney
- Glomeruli in inner cortical regions; long nephron loops that go deep down into the medulla
2) . Superficial;
- Reduce the filtering volume
- Receives 90% of renal supply
- Reabsorbs a large percentage of fluid that filters from vasculature
- Located superficially
- Glomeruli in outer cortical regions; short nephron loops
What is the urine passage in females and males?
Females;
- Ureter brings urine down, passes it posteriorly to ovary, lateral to cervix and vagina and into the bladder
(females have a very short urethra)
Males;
- Ureter comes down from above into the bladder then into the urethra passing through the prostate and into the penis
What muscle relaxes when the bladder fills?
The detrusor muscle
What kinds of waves propels urine down the ureter?
Peristalsis
What kind of epithelium lines the bladder and what does this allow for?
Transitional epithelium (urothelium) lines the bladder as it is urine proof.
What is the glomerulus made up of?
The glomerulus is a ball of many capillaries
Where does the filtrate collect?
The filtrate comes out of the capillaries and into the Bowman capsule where it collects, ready to enter the tubule of the nephron
How is the filtrate removed from the capillaries?
The high pressure in the capillaries forces the plasma through the capillaries and forces out the ultra-filtrate (start of urine production), separating the plasma from cells and proteins.
How is reabsorption done in the kidneys?
Water and solutes are transferred from the lumen of the nephron tubules into the. interstitial so they can come back into circulation again.
What are the 2 reabsorption paths?
Paracellular reabsorption - where the substance being reabsorbed back out of the lumen of the nephron can come through tight junctions back into into interstitial and blood vessels
Transcellular reabsorption - Reabsorption through the cells of a nephron, across the apical membrane then from the cell across the basolateral membrane. For this to occur there are various channels. and transporters. to allow for the transport of many substances across the cell.
What provides energy for the majority of reabsorption ?
NAATPase
How is ion transport powered?
Ion transport creates a voltage gradient between tubule lumen and interstitium, which allows for more. movement of substance across
How are solutes transported across?
Solutes are carried along the water flow by solvent drag
What happens later on in the nephron?
Other substances are secreted back into/ what is remaining of the ultra-filtrate to get rid of that from the body.
What happens in reabsorption?
The ultra-filtrate that has previously been removed from the blood comes back into circulation again
What is the countercurrent multiplication mechanism?
The countercurrent multiplication mechanism makes use of the different tissue gradients of osmolarity that the loop of Henle passes through in order to concentrate the filtrate.
Where about are the high osmalarities and pressure in the loop?
High osmolarity - DTL (descending thin limb) and around the loop
Water exits the tubule driver by the osmotic pressure gradient
How does the Ascending thick limb of the loop prevent water from re-entering and diluting its contents?
It is impermeable so water cannot dilute its contents
Where in the kidney are high and low osmolarities found?
High osmolarity - in the medulla
Low osmolarity - in the cortex
What occurs after the DCT?
Sodium is removed as there is a very high concentration
What. 2 features does the Proximal tubules have, making it better suited to its function?
PT epithelial cells have apical microvilli that increases the surface area + junctions between cells that are leaky. to maximise the free flow of water and solutes
How is reabsorbed fluid returned to the vasculature?
Via the peritubular network
What is micturition?
Getting rid of the urine formed
How is the urine modified after leaving the kidneys?
Urine is not modified after it leaves the kidneys
What is present in an empty bladder?
Rugae (folds) on the walls
What lines ureters and what does this allow?
Ureters are lined with smooth muscle and transitional epithelium that stretches to allow for urine flow
What controls the outflow via the urethra?
The inner and outer sphincters.
How does the body detect when the bladder is full and release urine?
When the bladder wall is stretching mechanoreceptors send signals to the pontine micturition (gets rid of urine) but also sends signals via the spinal chord to initiate micturition reflex which causes the Detrusor muscle to contract and increase luminal pressure
If we can’t go to the bathroom at that moment what happens?
The micturition reflex is. inhibited but the bladder carries on filling
How much can we control. holding in the toilet?
We have a conscious role in when micturition takes. place however, one the bladder reaches. its maximum capacity we don’t
