Histo: Urinary System

Front 1

Kidney vascular functions

Back 1

1. glomerula filtration
2. exchange of ions and metabolites with peritubular capillaires
3. maintenanace of gradient necessary for countercurrent exchange mechanism

Front 2

Kidney lobes

Back 2

15 lobes in each kidney
1. medullary pyramid: tip of pyramid projects into minor calyx (spaces produced by expansions of ureter in kidney)

2. overlying cortex
infolding: renal columns envelop each medullary pyramid and supply with blood via lobar branches.

Front 3

Kidney Lobules:

Back 3

Centered on a medullary ray

Medullary ray (pars radiata): cylindrical cluster of stright tubular segments to and from medulla.
2. pras convoluta: convoluated tubes and glomeruli between medullary rays.

Front 4

Uriniferous (Malphiigian) Tubule
Nephron

Back 4

Uriniferous tubule = Nephron + collecting tubules/ducts

1. formed by union of distal tubular of metanephric rudiment and ureteric buds
2. No fusion -> no outflow -> polycystic kidneys.

Nephron: basic functional unit
1. glormerulus:
(a) branhced network of capillary loops in bowman's capsule
(b) surround by basement lamina and podocytes (visceral epithelia cells)
(c) urinary filtration barrier: endothelium, basement lamina, visceral epithlium
2. proximal convoluted tubule (PCT): lumen obscured by tall microvilli, recovery of smlal molecules from filtrate
3. Henle's Loop: has thin limb and desc. asc. thick limbs
4. distal convoluted tubule(DCT): more open lumen than PCT.

Collecting Duct:
1. continuous with DCT
2. embryologically not but functionally part of nephron
3. largest duct (Bellini) onto papilla at tip of medullary pyramid.

Front 5

Glomeruli, PCT, DCT

Back 5

PCT vs. DCT
1. PCT has larger cells with microvillus border that will the lumen.
2. DCT patent lum
3. both have lots mitochondria, infolded basl membrane

Glomeruli in Bowman's capsule
1. afferent/efferent arterioles.
2. parietal epithelial layer : outer boundary of capsule, continue with visceral epithelium
3. urinary space (bowman's sapce): filtrate pass into, external to capillary and visceral epithelium; continuous with PCT lumen at urinary pole.

Front 6

Filtration Apparatus:
Glomerulus cell types

Back 6

1. capillary endothelial cells: fenestrated capillaries wtih increased transendothelial permeability
2. podocytes (visceral epithelial cells of bowman's capsule): in urinary space, branching wtih pedicles covering external surface of capillary loops, filtrate passes through filtration slits b/t pedicles and urinary space.

3. Mesangial cells: phagocytic cells embedded in reticular fiber network (mesangial matric) between adjacent capillaries. Function in filter maintenance.

4. extraglomerular mesangial: vascular pole, contractile.

Front 7

fine structures of filtration barriers

Back 7

Damage to barrier -> protein in urine (molecules larger than 70,000 MW not pass barrier)

Endothelial fenestrae and filtration slits b/t foot processes permit movement of = basement membrane

GAG's reduce permeability negatively charged molecules.

Front 8

Renal Medulla
direction and components

Back 8

All tubules in same direction (all in longitudinal, x-section or oblique)

1. collection ductscolumnar cells, lead to larger ducts of bellini that open on the renal papilla inot minor calyx.
2. thick limbs: ascending and desceding limbs of henle's loops.
3. thin limbs of Henle's lop, capillary sized simple squamous tubules, no red cells.
4. vasa rectae: peritubular capillaries, have rbc's (diff from thin limbs).

Front 9

Blood supply for medulla and cortex
p. 183

Back 9

1. arcuate arteries: along corticomedullary junction of each lobe - supplie dby interlobar arteries at margins of each pyramid and have arteriolar branches to cortex and medulla

2. Cortex
Interlobular branches from arcuate vessle into cortex supply half of each adjacent lobule
(a)afferent artrioles to glomeruli
(b)peritubular capillaries
(c)stellate arteries & veins at capsular surface

3. Medulla
Vasa rectae Capillaires are long recurrent loops paralle wtih Henle's loops supplied by
(a)efferent arterioles from glomeruli in juxtamedullary cortex that traverse directly to medulla (vasa rectae spuriae)
(b) Direct branches from arcuate arteries (vasa rectae verae)
(b)

Front 10

Juxtaglomerular appartus

Back 10

= macula densa + juxtaglomerular cells

1. macula densa: distal convoluted tubule cells
2. juxtaglomerular cells: granules with renin
(a) sm mm of afferent arteriole
(b) aka granular cells with renin
(c) function: detect decreases in filtration rate, respond to change sin Cl is distal tubule, secrete renin.

Angiotensinogen (renin converts) -> angiotensin I (endothelial cells converts) -> angiotensin II -> adrenal cortex (minralcorticoids)

Hormones:
(1) mineralocorticoids: aldosterone, distal convoluted tubules to increase Na reabsorption.
(2) antidiuretic hormone (ADH): secreted by posterior pituitary in response to decrease in blood osmolarity, increase water permeability of collecting ducts to recover water.
(3) atrial naturetic factor: produced when atrial distension, decreases sodium reabsorption at distal convoluted tubule, lose sodium and water, decrease BV. oppo. aldosterone.

Front 11

Urinary Tract: Ureter

Back 11

1. star-shaped lumen with mucosal ofdsl
2. transitional epithelium
3. muscularis: 3 layers (inner & outer longitubdinal, middle circular)
4. look alikes:
(a)vas deferens: thicker muscular wall of compact circular fibers and small irregular lumen
(b) oviduct: mucosal fold lacks symmetry with simple ciliated columnar epithelium

Front 12

Bladder
structure & function

Back 12

1. transitional epithelium
(a) distensibility
(b) osmotic barrier fucntion, hypertonic urinary content is maintained.
2. muscles intermixed middle circular and inner/outer longitudinal
(a)longitudinarl: detrusor muscle
(b) valves at opening of ureter
(c) internal sphincter circular arrangemnet of sm mm at neck of bladder
(d) external sphincter of sk mm under voluntary control.
3. mucosa
(a) well vascularized (blood and lym vessels)

Function:
1. emptying is autonomic reflex overridden by external sphincter (pudental nn)
2. expel urine, internal sphincter relax (by inhibit sympathetic fibers) and relax detrusor mm (inhibit parasym) and contact external sphincter).

Front 13

Urethra:

Back 13

1. urinary epithelium of bladder -> non-keratized stratified squamous -> keratinized eptihelium of skin at external urethral opening
2. F/M embedded in erectile tissue
3. male:
(a) prostatic urethra is transitional
(b)membranous and penile uretha (in corpus spongiosum of penis) are stratified/psydostratified columnar
(c)glans penis is non keratinized squamous.