Renal Anatomy & Histology Flashcards
Organs of the urinary system and function
kidneys, ureters, urinary bladder, and
urethra
Kidneys filter metabolic waste products and toxins from the bloodstream and convert the filtrate into urine; important
role in BP regulation
The ureters, urinary bladder, and
urethra make up the urinary tract
because they store and transport the urine out of the body
Characteristics of Anterior Aspect (location, size, what does it contain)
Retroperitoneal lying about T12-L3 levels
Lower on right
Suprarenal gland above
Size—10 cm long, 5 cm wide, & 2 cm thick
Renal hilum—entrance to renal sinus (area in kidney where BV, renal pelvis, nerves are locate)
Characteristics of Posterior Aspects (plane , what does it contain)
Left hilum near transpyloric plane (—5 cm from median plane)
Transpyloric plane runs through superior pole of right kidney (—2.5 cm lower than left)
Posteriorly, superior parts lie deep to 11th and 12th ribs
Inferior pole of right kidney is approximately index fingers breath superior to iliac crest
Renal Fat (3)
1) Perinephric fat-adjacent kidney
- extends into renal hilum and pelvis
2) Renal fascia— covers fat enveloping kidney and suprarenal gland
- blends and sheaths renal vessels
- superiorly continuous with inferior diaphragmatic fascia
3) Paranephric fat—external to renal fascia
internal anatomy of kidney (9)
1) Capsule—dense irregular CT on surface with inner layer of myofibroblasts
2) Renal cortex—outer portion containing renal corpuscles
3) Renal medulla—collection of renal pyramids and columns
4) Renal pyramids—cone-shaped masses in the medulla projecting into calyx
5) Renal columns—tissue lying between pyramids running from cortex to the calyx
6) Renal lobes—single pyramids plus surrounding adjacent cortex
7) Renal pelvis—collecting funnel for urine
8) Renal calyxes—out-pocketings of the renal pelvis
9) Renal papillae- projections of medullary pyramids apices into calyxes
Renal artery (1) and Ureter branches (6)
Renal arteries
• Segmental arteries
Ureter
1) Renal branches
2) Gonadal branches
3) abdominal aorta branches
4) Iliac branches
5) Superior vesicular branches
6) Pelvic branches- rectal, uterine, vaginal, inferior vesicular
Path of renal blood supply
aorta-> renal artery-> segmental artery-> interlobar artery -> arcuate artery-> cortical radiate artery-> afferent arteriole-> glomerulus (capillaries)-> efferent arteriole-> peritubular capillaries and vasa recta-> cortical radiate vein-> arcuate vein-> interlobar vein-> renal vein-> inferior vena cava
Renal nerve plexus (innervation)
Sympathetic: aorticorenal ganglia
- Lesser Splanchnic (T10-T11)
- Least Splanchnic ( T12)
- Lumbar splanchnic ( L1-L2)
Parasympathetic
- vagus n
What is Urine Carrying Unit made up of? (2)
1) Nephron (urine forming unit)- renal corpuscle and renal tubule
2) cortical and medullar collecting ducts- final concentration of urine
Renal Tubular Structures (12)
Bowman's capsule Proximal convoluted tubule Proximal straight tubule Thin loop of Henle (x2) Thick ascending loop of Henle Macula densa location Distal Convoluted Tubule Collecting Tubule Collecting Duct- Cortical Collecting duct- Medullary Papillary Duct
What does the cortex contain?
renal corpuscles
convoluted tubules
Straight tubules
portions of collecting ducts
What does medulla contain?
renal pyramids ( cone-shaped masses)
Renal columns
What are cortical (medullary) rays? and what do they contain?
aggregation of collecting ducts and straight tubules
runs between renal corpuscle and convoluted tubules within cortex
axis of renal lobule
What is renal interstitium?
Fibroblasts that produce erythropoietin depending on O2 levels
Renal Corpuscle components ( 2 , layers)
1) Glomerulus
- capillaries (tuft)
- fenestrated with truly open pores
- afferent and efferent arterioles
2) Glomerular capsule (Bowmans)
- parietal layer- simple squamous
- visceral layer- podocytes
- glomerular space- primary filtrate
Poles of renal corpuscle (2)
Vascular pole
- afferent arteriole
- efferent arteriole
Urinary pole
- origin of proximal convoluted tubule
Glomerular Endothelium characteristics (4)
- truly open fenestrations
- thick luminal glycocalyx
- lots of aquaporin water channels
- can generate Nitric oxide and PGE2 ( via angiotensin II)
podocytes characteristics (4)
visceral layer of Bowman’s
- forms part of filtration barrier
- single layer of cells having foot-like process (pedicels) that interdigitate to make filtration-like slits
-slits important for regulating size, patency, and selectivity of filtration
Filtration Membrane ( location, functions, layers (4))
- lies between blood and capsular space
FXN:
- restricts passage of blood cells, immunoglobulins and large proteins
- allows passage of water, ions, glucose, amino acids, urea
- one quart passes through per 8 mins ( ~45 gallons per day) but 1 gallon excreted per day
plasma
1) capillary endothelium
2) basement membrane
3) foot processes of glomerular capsule
4) slit diaphragm
Glomerular Basement (content, barriers)
- Type IV and XVIII collagen, laminin, entactin, proteoglycans
- physical barrier- <70kd passes through
- chemical barrier - strong anti-anionic characteristics
- albuminia: urine albumin will show damaged GBM
Mesangial cells function (5)
FXN:
1) support glomerular loops and ECM of podocytes
2) control glomerular filtration rate
3) prevent glomerular distension ( contractile) due to high glomerular BO
4) secrete growth factors and cytokines in response to injury
5) phagocytic- removing cellular debris and protein aggregates
Proximal Convoluted Tubule
location, tissue, content
- in renal cortex
- most abundant and active tubule in resorption and secretion
- simple cuboidal/columnar
- lots of microvilli and mitochondria
- basal and lateral cell membranes
- increase SA
- Na/K Atpase pumps and aquaporins
- Glucose transporters (sGLT2) and amino acid transporters
Proximal Straight Tubule
- less well-developed brush border
- high affinity sodium-glucose cotransporter (sGLT1)
Loop of Henle (path, tissue, function) for thin and thick
Path- down into medulla, up into cortex, terminates near vascular pole
Thin
- simple squamous
- no brush border
- some nuclei bulge into lumen
Thick
- simple cuboidal
- microvilli
- no brush border
FXN:
- set up hyper osmotic gradient to draw water back into tubule
distal convoluted tubule (location, tissue, hormone)
- cortex
- from macula densa of thick ascending Loop of Henle portion
- simple cuboidal epithelium
- little microvilli
- smooth luminal surface
- cells taller than Thick ascending LOH
- Angiotensin II influences Na+ resorption
Collecting duct ( tissue, location, function (2), cell types (2), hormone)
- simple cuboidal (some simple columnar)
- through cortex into deep medulla
- form larger papillary ducts that then drain into renal minor calyx
FXN:
1) water reabsorption
2) receive primitive urine from several nephron
- final urine osmolality determined by resorbing H2O
- individual cells of duct epithelium can be detected
Cell Types
1) Light/Principal cells- target for aldosterone
2) Dark/Intercalated cells- involved H+ and bicarbonate transport
Hormones
- target of both ADH and aldosterone
- increasing Na+ reabsorption and water retention
Types of Capillary Beds (3)
1) Glomerulus- high to low pressure gradient ( afferent arterioles drained by efferent arterioles)
2) Peritubular capillaries
- from efferent arterioles
- surround convoluted tubules
- lined with fenestrated endothelium
- reuptake of H2O and salts
3) Vasa Recta
- thin-walled vessels
- arise from efferent arterioles of juxtamedullary glomeruli
- fenestrated in ASCENDING only
- run alongside loop of Henle
- part of urine concentrating system
Juxtaglomerular Apparatus (components (2))
1) Juxtaglomerular cells - mechanosensory
- secrete renin if BP is low
2) Macula Densa
- distal end of thick ascending LOH
- acts as chemoreceptor (monitor salt levels)
- signal release of renin from juxtaglomerular cells if sodium is low
Function of Renin
Increase sodium retention, blood volume, and blood pressure
Transitional Epithelium (location, layers, content)
- lines urinary tract
Layers
1) superficial- stretched and relaxed
2) intermediate- sliding layer
3) basal- stem cell (epithelial)
Fusiform vesicle
- fuse with plasma membrane when cell is distended
- endocytosed when nondistended
Urothelial plaque
- form impermeable barrier
- uroplakin proteins
Ureters (location, function, tissue, layer)
- long fibromuscular tube
- carry urine from kidney to bladder
- renal pelvis-> bladder
- goes oblique to prevent backflow of urine
- transitional epithelium
Muscularis ( 3 layers)
1) inner longitudinal layer
2) outer circular layer
3) outer longitudinal layer
Adventitia
- typical connective tissue
Urinary Bladder ( characteristic, function, location, content)
- muscular sac
- posterior to pubis
- anterior to uterus/rectus
- expands into abdominal cavity while empty bladder lies entirely within pelvis
- store and expel urine
Trigone
- inferior/posterior wall
- ureter and urethra open
Bladder wall
- transitional epithelium
- 3 layer thick smooth muscle (detrusor muscle)
- fibrous adventitia
Urethra ( General function, tissue)
- connect bladder with exterior
Epithelium depends on location
- Transitional epithelium- near bladder near origin (proximal)
- Pseudo stratified columnar- majority of Urethra
- Stratified Squamous Epithelium- at distal end
female urethra (length, path, components (3), function)
size: 3-5 cm
external urethral orifice (female perineum)
1) Membranous urethra- through urogenital diaphragm
2) Internal urethral sphincter- INVOLUNTARY SMOOTH muscle, part of bladder wall
3) external urethral sphincter- VOLUNTARY SKELETAL muscle inhibit urination , part of pelvic floor
Function
- restrict release of urine until pressure in urinary bladder is high enough
- voluntary activity to release urine
Male Urethra ( size, function (2), regions (3))
size: 20cm in length
function
1) transport urine
2) transport semen
Regions
1) Prostatic urethra- passes through prostate gland
2) Membranous urethra- through urogenital diaphragm ( same in female)
3) spongy (penile) urethra
- passes length of penis
- encased in cylindrical erectile tissue (corpus spongiosum) in penis to reach external urethral oriface
polycystic kidney disease
Autosomal Dominant
Cysts form
- crush tissue and impede drainage
- kidney failure/ infection
- BP mis-regulation
- asymptomatic
- first seen at 30-40 yr
Tx:
- major diet change
- kidney transplant
- dialysis
