Urinary Flashcards
Which renal vein is longer? Why?
Left because it has to cross over the aorta
Why does the testicular vein drain into the renal vein on the left but not on the right?
The left renal vein is longer because it crosses over the aorta.
What spinal levels are the kidneys found at?
Left - T11/12
Right - T12/L2
Which kidney is usually lower? Why?
Right because it is pushed down by the liver
Which areas make up the parenchyma of the kidney?
The cortex and the medulla
Describe the flow of urine as it leaves the collecting ducts.
Minor calyx - major calyx - renal pelvis - ureter - bladder - urethra
How can you identify the ureters on an X-ray?
Follow the path of the transverse spinous processes
In which operations do the ureters frequently get damaged? Why?
Hysterectomy
Because the uterine artery (which has to be cut) travels over the ureter and it is pulsatile so looks slightly arterial
Water under the bridge
Where are the three most common sites for kidney stones?
Top - pelvoureteric junction
Middle - as ureter passes over the iliac crest
Bottom - vesicoureteric junction
Describe the type of pain caused by renal stones. Why does it feel like this?
Loin to groin in the T11-L2 dermatomes
Colicky because ureter is a pulsatile tube, pushing intermittently against the stone
Where is the perinephric fat?
Around the hilum of the kidney. (Where everything else enters)
What is the kidney capsule?
Dense fibrous covering which surrounds each kidney.
What is the structure in the kidney that allows filtration to occur?
Glomerulus
Glomerular tuft of arterioles inside the Bowman’s capsule
Give three important locations of terminal arteries.
Brain, kidney, retina
Which embryological tissue does the urinary system derive from?
Intermediate mesoderm
Name the 3 embryological stages of urinary development.
Pro nephros
Meso nephros
Meta nephros
What are the two components of the mesonephros and what are their derivatives?
Ureteric bud - turns into collecting system and drives metanephros
Mesonephric duct - vas deferens
How does the metanephros develop?
Ureteric bud drives development de novo from intermediate mesoderm
What is the cloaca and how is it divided?
Where the GI tract and urogenital sinus merge.
It is divided by the growth of the urorectal sinus.
What is the urachus? What is its adult derivative? What happens if it remains patent?
Duct that joins urogenital sinus (future bladder) to the umbilicus
Turns into umbilical ligament
If it remains patent, urine leaks from umbilicus
Describe the ascent of the metanephros.
Begins in the hindgut and the trunk grows around it, so that it appears to ascend to the level of t11. Renal arteries develop along the ascent.
Why are there often supernumerary renal arteries?
Form and reform during the ascent of the kidney.
What causes a horseshoe kidney?
Kidneys rotate and fuse during their ascent. The isthmus (fused part) stops it travelling higher than the inferior mesenteric artery.
What causes an ectopic ureter? What complication can be associated with it?
2 ureteric buds form - either de novo or by one splitting.
If the ectopic ureter opens inferior to the bladder it can lead to incontinence.
What causes a urorectal fistula? What are the symptoms?
Failure of the urorectal sinus to fuse with the perineum.
Faecal contents leak out of urethra and high risk of UTI.
Which type of epithelia are found in the proximal convoluted tubule? State two specialisations.
Simple cuboidal
- Lots of microvilli to increase surface area for mass reabsorption
- Lots of mitochondria to supply the Na/k atpase which sets up the sodium gradient for passive reabsorption
Which type of epithelia are found in the loop of Henle?
Simple squamous
Which type of epithelia are found in the distal convoluted tubule?
Simple cuboidal.
Few microvilli and few mitochondria
Where are transitional epithelia found?
Minor calyx down to the superior urethra.
What are the four parts of the urethra and the type of epithelia found there?
Pre prostatic - transitional
Prostatic - transitional
Membranous - Pseudostratified columnar
Spongy - stratified squamous
What two factors influence whether a particle is filtered at the glomerulus?
Size - only small get through the endothelial wall and the filtration slits in the podocytes
Charge - negative are repelled by glycoprotein basement membrane so positive get through more easily
What are the three layers a that separate the blood from the ultra filtrate at the Bowman’s capsule?
Fenestrated endothelial
Glycoprotein basement membrane
Podocytes with filtration slits
In the glomerulus, is the afferent or efferent arteriole wider? Why?
Afferent to produce a hydrostatic pressure that forces some of the blood to be filtered.
What are the three pressures acting on the blood at the glomerulus?
Hydrostatic into the filtrate - from the different diameters of the afferent and efferent arterioles
Hydrostatic back pressure of the filtrate
Oncotic draw of the concentrated proteins in the plasma.
By which two mechanisms does the glomerulus auto regulate the filtration rate?
Myogenic regulation
Tubuloglomerular feedback
If the pressure in the afferent arteriole to the glomerulus increases, how will the myogenic auto regulation respond?
Increase in pressure risks an increase in GFR.
Smooth muscle senses the stretch and contracts to prevent extra blood reaching the glomerulus.
If the pressure in the afferent arteriole to the glomerulus decreases, how will the myogenic auto regulation respond?
Decrease in pressure risks an decrease in GFR.
Smooth muscle senses the relaxation and dilates to allow extra blood to reach the glomerulus.
If the pressure in the afferent arteriole to the glomerulus increases, how will the tubular glomerular auto regulation respond?
There is a brief increase in GFR. More NaCl reaches the distal tubule.
This is sensed by the macula dense cells and the juxtamedullary apparatus releases adenosine to vasoconstrict the afferent arteriole and stop the increase in GFR.
If the pressure in the afferent arteriole to the glomerulus decreases, how will the tubuloglomerular auto regulation respond?
There is a brief decrease in GFR. Less NaCl reaches the distal tubule. This is sensed by the macula densa cells and the juxtamedullary apparatus release prostaglandins to vasodilate the afferent arteriole and increase the GFR back to normal.
Why does the distal tubule travel up to the glomerulus and nestle between the afferent and efferent arterioles?
So that it can communicate with the juxtamedullary apparatus and regulate the filtration rate based on how much NaCl it senses.
What is glomerular filtration rate? What is a normal rate?
Rate of kidney function
Should be over 90 ml/min
How do we calculate GFR? Why is it a slight overestimate?
Clearance of creatinine.
Creatinine is slightly secreted into the tubule so it appears that clearance is greater than it is.
What are the ideal characteristics of a substance we could use to calculate GFR?
- Freely filtered
- Not re absorbed
- Not secreted
What is creatinine? What type of person would have higher natural levels?
Product of muscle breakdown
Muscular, young, male
By what process does the kidney control blood volume?
Reabsorption of Na
Where does bulk Na reabsorption occur? How much of the total is reabsorbed?
Proximal convoluted tubule
67%
Which Na transporters are present in the PCT?
Early - Na glucose
Later - Na H
Which Na transporters are present in the Descending limb of the loop of Henle?
None. Just loose junctions and aquaporins for water to set up gradient for the ascending limb.
Which Na transporters are present in the thin ascending limb of the loop of Henle?
Just the Na k atpase.
Na moves passively out here due to the gradient set up in the descending limb.
Which Na transporters are present in the thick ascending limb of the loop of Henle?
Nak2cl
And ROMk to leak k and keep the Nak2cl functioning.
Which Na transporters are present in the DCT and collecting duct?
ENaC and associated k channel
Which part of the nephron is most sensitive to hypoxia?
Thick ascending limb because the nak2cl uses most atp.
Why is 67% of the Na always absorbed at the pct and not a fixed amount? What is this mechanism called?
Keeps the Na that travels through the rest of the nephron more constant than if a fixed amount was absorbed.
Glomerulotubular balance.
How is osmolarity and electro neutrality maintained through the pct?
As Na is removed, opposing ions eg cl and urea are left behind and make up a greater proportion of the filtrate. So elctroneutrality of ions is maintained. These also attract a similar level of water as the Na.
What 3 factors can increase renin release?
- Decreased NaCl in distal tubule detected by macula densa cells
- Decreased perfusion in afferent arteriole
- Increased sympathetic stimulation
Where is renin released?
Granular cells in Juxtaglomerular apparatus
What is the action of renin?
Angiotensinogen - angiotensin 2
What is the action of angiotensin converting enzyme? (ACE)
Angiotensin 1 - 2
Give 4 actions of angiotensin 2.
Increased sympathetic stimulation
Vasoconstrict
Increased Na/H action in the pct (increased Na absorption)
Aldosterone release from adrenal cortex
What is the main action of aldosterone?
Increase ENaC action and associated k channel in the DCT. Increased reabsorption of Na.
What are 3 actions of anti diuretic hormone?
Increased action of nak2cl channel in thick ascending limb of loop of Henle. Therefore increased reabsorption of Na.
Up regulation of aquaporin 2 channels
Increase urea reabsorption
What stimulates thirst and release of adh?
Osmoreceptors sense low osmolarity in hypothalamus - posterior pituitary
How do beta blockers inhibit raas?
Decreased sympathetic stimulation.