Kidneys Flashcards
(45 cards)
Function of kidneys
▪️excrete waste products of metabolism as urine
▪️controls water and electrolyte balance in the body- BP
▪️maintain blood composition
▪️regulate calcium levels
Position of kidneys
▪️high on posterior abdominal wall
▪️lies behind peritoneum (retroperitoneal)
▪️right kidney is lower than the left due to right lobe of the liver being bigger than the left
▪️right -rib 12 to L2
▪️left - ribs 11/12 to L1
Renal tubular system
▪️collecting ducts ▪️minor calyx ▪️major calyx ▪️renal pelvis ▪️ureter
Anterior relations of the kidneys
▪️superior-super-renal glands
-right
▪️upper part-liver (peritoneum)
▪️middle medial- descending part of duodenum (direct)
▪️middle lateral- right colic flexure (direct)
▪️lower part- small intestine (peritoneum)
-left
▪️upper medial- stomach (peritoneum)
▪️upper lateral- spleen (peritoneum)
▪️middle medial- pancreas (direct)
▪️middle lateral- left colic flexure (direct)
▪️lower lateral- descending colon (direct)
▪️lower medial- jejunum (peritoneum)
Artery branches
▪️aorta ▪️renal artery ▪️segmental artery ▪️interlobar artery ▪️arcuate artery ▪️cortical radiate arteries ▪️afferent arteriole ▪️glomerulus
Vein branches
▪️efferent arteriole ▪️peritubular capillaries (around the tubules) ▪️cortical radiate vein ▪️arcuate vein ▪️interlobar vein ▪️renal vein ▪️inferior vena cava
Urine formation
▪️filtration - 180litres of fluid per day (body has 5-6 so is recycled)
▪️reabsorption- 70% in PCT and LoH, DCT and CD influenced by ADH
▪️secretion- additional substances are secreted in tubular fluid, enhances kidneys ability to remove waste and toxins
▪️excretion- final composition of urine
Ureters position
▪️retroperitoneal
▪️start at renal pelvis to bladder
▪️descend inferior and medially along the lumbar transverse processes
▪️position leads to constricts in 3 places
▪️lower part is closely associated with the uterine artery which supplies uterus- common to damage one or the other during surgery
Ureters function
▪️muscular tubes that contract to aid movement of waste products
▪️delivers urine from kidneys to bladder
Ureter blood supply
▪️quite extensive-branches from different sources
-upper-renal
-middle-gonadal
-lower-internal iliac
▪️can sometimes get lumbar arteries branching from abdominal aorta
Ureteric constrictions
▪️pelviureteric junction- coming out of renal pelvis- gets narrower
▪️as it crosses pelvic brim- kink where kidney stones can become lodges
▪️as it enters the bladder-narrows
Histology of kidneys
▪️macular densa cells- thickening of DCT which regulates GFR as part of feedback loop.
▪️mesangial cells- middle of afferent and efferent arteries where they join glomerulus- modified smooth muscle cells- effect GFR
▪️podocytes- have feet like projections (pedicels) which weave together and leaves slits in between where filtrate flows through- stops large molecules from passing through.
▪️granular cells- juxtaglomerular cells- specialised smooth muscle cells-synthesise and store renin- walls of AA and EA
Histology of ureter
▪️similar to blood vessels- has layers of tissues
▪️adventitia- fibroelastic connective tissue - anchors to surrounding structure so it can move with other structures and not get damaged
▪️circular and longitudinal layer- thick muscular layers-peristalsis-active contraction
▪️epithelial layer- mucosal layer- protection
Embryology of kidneys
▪️3 successive stages- pronephros, mesonephros, metanephrons
▪️metanephros ascends from S1-S2 to T12-L3 which happens at Week 6-9
▪️as they rise, branches of vessels also rise with them
▪️rotate 90 deg as they rise to face medially
Congenital abnormalities of kidneys
▪️pelvic kidney -remains in pelvic location
▪️horseshoe kidneys-inferior poles fused together and gets stuck on inferior mesenteric artery
▪️unilateral double kidney-migration to one side
-not a functional issue, diagnostic issue
-different referred pain as in different position
-can be prone to strangulation by SI
Congenital abnormalities of ureters
▪️double pelvis
▪️bifold ureter- can join together or stay apart
▪️ectopic ureteric orifice-skip bladder into urethra- less control of urine
▪️megaloureter- bulgy and thick
▪️postcaval ureter- wraps around artery and veins
Kidneys affect on Blood pressure
▪️maintains constant blood flow through and around nephrons
▪️regulates nephron blood pressure indecent of systemic one
Nephron function
▪️glomerulus- filters out substances- no large molecules
▪️bowman capsule- captures filtrate and directs to PCT
▪️PCT-reabsorbs 2/3 of Na+ therefore 2/3 water, glucose, organic nutrients
▪️loop of Henle- 20% of salt and water is absorbed here
▪️DL of loop- absorbs water as is only permeable to water
▪️AL of loop- absorbs Na+ and Cl- as is only permeable to them
▪️DCT- 10% is reabsorb here- only if needed- secretion of waste and toxins
▪️CD-influenced by ADH to absorb more water if needed
Types of nephron
▪️cortical nephron- 70%- short and majority in cortex of kidneys
▪️juxamedullary nephron- longer and majority in medulla of kidneys
-JMN are more in desert animals who conserve their water as it is scarce.
Glomerulus
▪️3 layers make up filtration unit
▪️podocytes- modified epithelial feels, feet like process that weave together and stop large proteins from being filtration
▪️basement membrane- cell layer containing -ively charged glycoproteins, has pores to filter out different sized molecules
▪️capillary endothelium- flat and thin layer, sensory but not robust.
-afferent arteriole is larger than the efferent which increases pressure therefore GFR
Echoes
Filtration of molecules
▪️uncharged molecules <30,000 daltons (measures proteins)
▪️salts, glucose, amino acids, water
▪️RBCs,WBCs, plasma protein- all stay in vessel- creates a colloid pull which tries to draw water back in
▪️not all the salts, water and glucose are taken out 2/3- as it keeps circulating
Pressure in bowman capsule
▪️pressure created by AA being bigger than EA causes molecules to be forced out of filtration slits in to bow and capsule
▪️hydrostatic pressure- the pressure a liquid experts on something
-glomerular HP (HPg)- pressure of liquid being forever out =60mmHg (out)
-capsular HP (HPc)- pressure of capsule (rigid) pushing against liquid =18Hg (in)
-blood colloid osmotic pressure (OPg)- pressure of proteins trying to draw fluid back in to the vessel =32mmHg (in)
▪️net filtration pressure (NFP)- in a normal kidney the sure of OPg and HPc should be lower than HPg.
(60-(32+18))=10mmHg (out)
How to determine GFR
▪️marker of kidney health in GFR
▪️compare a substance in the blood to urine- how long does it take for the substances to be passed out.
▪️substance needs to be:
-filtered freely- stays in blood (<30,000 daltons)
-not secreted or reabsorbed- more or less affects the time it would take
-not toxic
-not broken down- may not be recognised in urine
GFR Calculation
▪️ GFR= solute conc in urine x vol of urine excreted per min / solute conc in plasma
▪️GFR= UV/P