Kidney - External Macro Anatomy

Kidney Anatomy

Corte

x

Kidney - Internal Macro Anatomy

Base

Medulla

Papillae

Colu

mn

Nephron

Renal Corpuscle

Renal Tubule

Renal Corpuscle

Renal corpuscle – Site of fluid filtration– 2 components

glomerulus – group of capillary loops– fed by afferent

arteriole– removed by efferent

arteriole

glomerular (Bowman's) capsule – double walled epithelial cup– outer wall (parietal layer) separated from inner wall (visceral layer) by

capsular (Bowman's) space

Nephron Renal tubule - where

filtered fluid passes from capsule– proximal convoluted

tubule (PCT)

– distal convoluted tubule (DCT)

– loop of Henle (nephron loop)

– short connecting tubules – collecting ducts – merge to papillary duct

then to minor calyx 30 pap ducts/papillae

Nephron Cortical vs.

juxtamedullary nephrons – Name depends on

length of LofH– 15-20% have long

loops and reabsorptive capabilities

Renal Corpuscle Histology Each nephron

portion has distinctive features

Histology of Glomerular filter– Three layers of tissue– From inside to out

prevents movement of progressively smaller particles

Renal Corpuscle Histology1) Endothelium of glomerulus

– Single layer of endothelium w/ fenestrations– Restricts RBC movement

Renal Corpuscle Histology2) Basement membrane of glomerulus

– Between endothelium and visceral layer of glom capsule– Prevents large protein movement

Renal Corpuscle Histology3) Filtration slits in podocytes

– Podocytes specialized epithelium of visceral layer footlike extensions w/ slits between extensions

– Restrict medium-sized proteins

Renal Corpuscle Histology

Tubule Histology In general, tubule is a single layer of epithelial cells

on basement membrane PCT

– cuboidal w/ brush border of microvilli on apical border surface area for reabsorption

Tubule Histology Descending loop of

Henle, beginning of ascending loop– simple squamous

epithelium– only permeable to

water

Remainder of ascending loop– cuboidal to low

columnar epithelium– only permeable to

ions

Tubule Histology DCT, collecting ducts -

cuboidal w/ some modifications in late DCT collecting ducts– principal cells– intercalated cells

Tubule Histology

– Macula Densa special cells in this area monitor Na+Cl- content in blood able to work w/ JG cells

– Both work together to regulate BP

– Juxtaglomerular (JG) cells modified smooth muscle secrete vasoconstrictors

Juxtaglomerular apparatus (JGA)– Ascending LofH contacts

afferent arteriole

Renal Blood Supply Important in

italics– Renal artery

20-25% of resting CO

1200 ml/min– Segmental

arteries– Interlobar arteries

- through columns – Arcuate arteries– Interlobular

arteries

Renal Blood Supply Important in Italics

– Afferent arterioles - each renal corpuscle receives 1

– Glomerular caps– Efferent arterioles -

drain blood from glomerulus

– Peritubular caps - around PCT and DCT

– Vasa recta - long loop from efferent arteriole around LofH

Renal Blood Supply Important in

italics– Interlobular

veins– Arcuate veins– Interlobar veins– Segmental veins– Renal veins -

exits hilus

Renal Nerve Supply Nerves from renal plexus of SNS Vasomotor nerves that accompany renal

arteries and branches– What is the role of SNS stimulation on renal blood

flow?– Fight or flight– Decrease flow

The Final Common Pathway Ureter

– extension of kidney pelvis

– enter bladder medially from posterior

Histology - 3 layers– mucosa

mucous membrane w/ transitional epithelium

secrete mucous– muscularis - smooth

inner longitudinal outer circular

– serosa

The Final Common Pathway Urinary bladder

– hollow muscular organ– generally smaller in females due to uterus– retroperitoneally in pelvic cavity posteriorly to pelvic

symphysis– freely movable

Structure - trigone

The Final Common Pathway Histology

– mucosa - mucous membrane of transitional epithelium and underlying lamina propria

– muscularis detrusor muscle 3 layers

of inner longitudinal, mid circular, outer longitudinal

around opening to urethra

– circular fibers form internal urethral sphincter

– lower is external urethral sphincter - skeletal muscle for control

– serosa - peritoneum

The Final Common Pathway

The Final Common Pathway Urethra

– small tube from floor of bladder to exterior of body females fairly straight path out through vagina males passes through the prostate gland

– histology female three coats

– inner mucous, intermediate thin layer of spongy tissue w/ plexus of veins

– outer muscular coat continuous w/ bladder male two layers

– inner mucous membrane – outer submucous tissue connects w/ structures that it passes