- filtration of solutes from blood

- selective, controlled reabsorption of water & filtrates

- acid-base control & management

- excretion of wastes as urine

- endocrine secretion/modification (erythropoietin, renin)

Function of Urinary System

- this renal structure is contiguous with CT filling renal sinus and covers renal pelvis

Renal Capsule

- renal corpuscles

- convuluted tubules (proximal and distal)

- collecting ducts

- vascular network

- medullary rays (associated with "cortical nephrons")

Renal Cortex

- Henle's loop

- vasa recta

- collecting ducts

- renal columns and pyramids

Renal Medulla

- anatomic unit of medullary pyramid with its overlying cortex and surrounding renal columns

Renal lobe

- functional unit of collecting ducts of a medullary ray and all the nephrons they drain

Renal lobule

Renal corpuscle --> proximal convuluted tubule --> Loop of Henle --> Distal convolutued tubule --> Collecting tubule

Nephron

- confluence of collecting ducts, drains to renal pelvis

Renal papillae

- region where urine accumulates to drain into the ureter

- calyces which cover the tips of renal papillae

- lined by urothelium

Renal Pelvis

Renal artery => Interlobar arteries => arcuate arteries => interlobular arteries => afferent arterioles => capillaries of the glomerulus => efferent arterioles => veins

Renal Vasculature

- efferent arterioles of these nephrons are peritubular capillaries which interact with convoluted tubules

Cortical nephrons

- efferent arterioles of these nephrons form vasa recta which interact with Henle's Loop and participate in countercurrent exchange that concentrates urine

Juxtamedullary nephrons

- has a "vascular pole" and a "tubular pole"

- surrounded by two layers that create Bowman's capsule

- contain afferent and efferent arterioles

Renal Corpuscle

- space between the visceral and parietal layers where the glomerular filtrate collects to drain into the proximal convoluted tubule

Urinary Space

- support the glomerular capillaries (contraction/phagocytic properties)

- secrete cytokines, prostaglandins, growth factors

- support the juxtaglomerular apparatus (Lacis cells)

Mesangial cells

- visceral capsule epithelial cells that surround glomerular capillary loops

- connected by nephrin that makes a semi-permeable membrane

- have cytoplasmic processes called "pedicels"

Podocytes

- fusion of basal laminae of both endothelial and epithelial cells

- laminin, fibronectin, type IV collagen, negative charge

- major barrier to filtration of large molecules

- damage can result in abnormal loss of large molecules

Glomerular basement membrane (GBM)

- made of simple cuboidal epithelium with a prominent apical brush border and plasma membrane infolding with mitochondria

- major site for reabsorption of water and solutes (glucose, proteins)

Proximal convoluted tubules

- thick => thin descending portion, then vice versa

- simple cuboidal => squamous

- returns to vascular pole of glomerulus (as part of juxtaglomerular apparatus)

- ascending limb impermeable to water

- Vasa Recta accompany tubules

Loop of Henle

- Renin-Angiotensin system resulting in Aldosterone secretion

- Macula Densa, Juxtaglomerular cells, Lacis cells

- function to regulate sodium/chloride concentrations in the urinary fluid

Juxtaglomerular apparatus

- made from distal tubule

- located where TAL meets vascular pole of its glomerulus

- composed of modified modular epithelial cells (larger, taller, more closely packed)

- sense sodium and/or chloride concentrations in urine

Macula Densa

- made from afferent arteriole

- modified smooth muscle cells of tunica media of glomerular arterioles containing granules of renin

- release renin by exocytosis into blood

Juxtaglomerular cells (JG cells)

- made from extraglomerular mesangium

- similar function to intraglomerular mesangial cells

- gap junctions connected them and communicate signals to glomerulus

- at vascular pole support the JGA

Lacis cells

- composed of simple cuboidal w/o brush border

- same as proximal otherwise

- Na/K pumps regulated by aldosterone

- last portion is collecting tubule, resembles collecting ducts

Distal convoluted tubule

- multiple nephrons join to form these

- different embryologic origin as nephrons

- simple epithelium (cuboidlal to low columnar)

- has Principal and Intercalated/Dark cells

- rich in aquaporins that are inserted into plasma membrane following ADH stimulation

Collecting Ducts

- located in outer cortex

- shorter loops of Henle

- thick portion may begin even before U-turn of the loop

Cortical nephrons

- located just above the medulla

- long loops of Henle accompanied by vasa recta

Juxtamedullary nephrons

- probable source of the growth hormone erythropoietin

Peritubular interstitial cells

- hollow muscular organ lined by urothelium

- loosa lamina propria and incomplete, ill-defined muscularis mucosa

- muscularis propria has smooth muscle arranged in "three" layers in different directions

Bladder

- lipid rafts that allow for urothelium to stretch into "umbrella cells" when the lumen is full and distended

Uroplakins

- prostatic, membranous and cavernous portions

(prostate gland, urogenital diaphragm, penis)

- urothelium => columnar => stratified squamous

Urethra