Histo Urinary System

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ANATOMY EVALS 8: Urinary System

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TOPIC: Histology Urinary SystemLECTURER: Dr. Ed Gonzales

DATE: December 2012

TRANSCRIBED BY: MAE PANTOLLA

BATCH 2016

Component Organs

A. Kidneys- performs all functions of systemB. Ureters- passageways for urineC. urinary bladder- temporary storage of urineD. urethra- passageway for urine.A. Kidney

a. Functions- homeostasis

o maintainance of normal composition and volume of body fluidso by eliminating metabolic waste products from body via urine

- production of hormones and other biologically active substanceso renino erythropoietin,o thrombopoietino kininso calcitrol (1, 25-dihydroxycholecalciferol).

b. Hilus- fissure on medial surface- entry for renal artery- exit for renal vein- exit for renal pelvis

c. Renal Sinus- hilus leads to it- 2.5 cm deep space within kidney- fat-filled- contains renal blood vessels, nerves and renal pelvis and calyces.

d. Capsule-

thin but tough (fibrous); easily stripped off from organ- at hilus,i. lines renal sinusii. becomes continuous with walls of calyces.


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e. Region on longitudinal section:

1. medulla inner portion striated

2. cortex outer portion reddish and granular

(note: arcuate vessels demarcate junction of cortex and medulla).

MEDULLA CORTEX

1. renal pyramids 10-15 conical structures that

make up medulla

renal papilla- apex ofpyramid

2. renal columns (of Bertin) inward extension of cortex

that separate pyramids.

- medullary rays (of Ferrein)o grossly:

longitudinal streaks from base of pyramids

o microscopically: collecting tubules segments of the loop of Henle

f. lobe renal pyramid

cortex that overlies base of pyramid corresponding cortical tissue in renal column (of Bertin)

g. lobule1. cortex

medullary ray (of Ferrein)- center of lobule

nephrons that drain into collecting tubules in medullary ray blood vessels, CT, nerves

2. medulla terminal segments of collecting tubule papillary ducts segments of loop of Henle that dip into medulla blood vessels, nerves, CT

h. blood vessells average blood flow to kidneys = 1.2 liters per minute

renal artery - from abdominal aorta

Interlobar arteries - enters renal sinus- traverses medulla and proceeds to cortex

Arcuate arteries - at corticomedullary junction- no anastomoses between arcuate arteries

Interlobular arteries

RENAL ARTERY INTERLOBAR ARTERY ARCUATE ARTERY INTERLOBULAR ARTERY


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Efferent arterioles

peritubular capillary network vasa recta

- supplies tubules around glomerulus- supply medulla

INTERLOBULAR ARTERIES AFFERENT ARTERIOLE GLOMERULAR CAPILLARIES EFFERENT ARTERIOLE

SUPERFICIAL AND

DEEP CORTICAL VEINSTELLATE VEINS INTERLOBULAR VEIN MEDULLARY VEIN ARCUATE VEIN

INTERLOBAR

VEIN

i. Uriniferous tubule1. Nephron2. intrarenal ducts

a. collecting tubulesb. papillary ducts.

Interlobular arteries

- straight branches of arcuate- located between renal lobules- form outer boundaries of lobules- terminally, supplies capsule.

Afferent arterioles - supply lobules

Glomerular capillaries - each has 20-50 loops

Efferent arterioles - drains glomerulus- then breaks up two ways:

superficial cortical veins - drain outer cortex and capsuledeep cortical veins - drain rest of cortexmedullary veins - a.k.a ascending segment of vasa rectae

- drain medulla


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NEPHRON INTRARENAL DUCTS

- functional unit of kidney- 1 to 1.5 million per kidney.Parts:

a. Renal corpuscle1. glomerulus

a) glomerular capillariesb) mesangeal matrix (mesangium)c) glomerular mesangeal cells

2. Bowmans capsule (glomerular capsule)a) Parietal layerb) Visceral layer

b. Renal tubule.segments:

1. proximal convoluted tubule2. Henles loop

a) thick descending limbb) thin limbc) thick ascending limb

3. distal convoluted tubule- juxtaglomerular complex

a. juxtaglomerular cellsb. macula densac. extraglomerular mesangial cells

a. collecting tubulessegments:

- arched collecting tubules- straight collecting tubules - main components of

medullary rays

b. papillary ducts- a.k.a. papillary duct (of Bellini)- formed by convergence of straight collecting

tubules- empties into a minor calyx; about 25 papillary

ducts/ minor calyx

- lined by tall columnar epithelium- functions of both:

o serve as conduits for urineo secrete potassium and acidify urine

(collecting tubules)

- epithelium : simple cuboidal but progressivelybecomes taller

a. Renal corpuscle- a.k.a. Malpighian corpuscle- located in cortex- forms proximal end of nephron.- vascular pole: entry point of afferent arteriole to, and exit of efferent arteriole- urinary pole: area where renal tubule begins.Parts:

1. glomerulus2. Bowmans capsule (glomerular capsule)


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1. GLOMERULUSa) glomerular capillariesb) mesangeal matrix (mesangium)c) glomerular mesangeal cells

GLOMERULAR CAPILLARIES MESANGEAL MATRIX

(MESANGIUM)

GLOMERULAR MESANGIAL CELLS

- result from break up of anafferent arteriole

- 20-50 highly convoluted loops- drain into a single efferent

arteriole.

- fenestrated-

not covered by a diaphragm- but very thick basal lamina

- amorphousmaterial similar to

basement

membrane

- between glomerular capillaries- stellate-shaped cells similar to pericytes.- cytoplasmic processes in between endothelial

cells to reach the capillary lumen

- produce mesangial matrix- contractile and can influence luminal diameter

of capillaries- phagocytickeeps glomerular filtration barrierfree of debris

2. BOWMANS CAPSULE

double-walled structure (each a single layer of epithelial cells)PARIETAL LAYER VISCERAL LAYER

outer wall simple squamous epithelium continuous with visceral layer at vascular pole continuous with epithelium of renal tubule at urinary pole.

covers glomerulus intimately epithelial cells are modified (podocytes).

capsular space (Bowmans space; subcapsular space; urinary space)- between visceral and parietal layers.

Vascular pole

urinary pole


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Podocytes

- modified simple squamous epithelial cells- associated intimately with glomerular capillaries- provided with processes

o major processes vary in shape & size

o minor processes (foot processes or pedicels) given off by major processes wrap around capillary walls interdigitate with pedicels of neighbors.

- subpodocytic spaceso spaces between processes of podocytes and capillaries

- filtration slitso narrow slits between the closely packed pedicelso covered by a thin electron-dense membrane (slit membrane or slit diaphragm).

Glomerular Filtration Barrier

- separates blood in glomerular capillaries from Bowmans capsular space- components

1. endothelium of glomerular capillaries2. basal lamina where endothelial cells and pedicels rest3. slit membrane of filtration slits.

- glomerular filtrationo

filtration barrier acts as sieve to allow ultrafiltrate ofblood (glomerular filtrate) to seep to Bowmans space

- glomerular filtrateo product of glomerular filtrationo flows from Bowmans space into renal tubule.

b. RENAL TUBULE- functions:

o tubular reabsorption - reabsorption of some water and solutes from glomerular filtrateo tubular secretion- addition of some solutes to glomerular filtrate.

- segments:1. proximal convoluted tubule2. Henles loop

a) thick descending limbb) thin limbc) thick ascending limb

3. distal convoluted tubule.PROXIMAL CONVOLUTED TUBULE HENLES LOOP DISTAL CONVOLUTED TUBULE

- direct continuation of Bowmanscapsule

- longest segment of nephron- functions:

o reabsorbs 70%-80% ofwater and sodium ions

present in glomerular

filtrate.o reabsorbs other

substances notably

glucose, amino acidsand chloride ions.

- simple cuboidal epitheliumcomprises entire wall

- cells with microvilli (brush border)- nucleus centrally located- lateral cell boundaries indistinct- basal striations (infolding of cell

membrane filled with

mitochondria)

- dips into medulla, makes hairpinturn, then returns to cortex

- types of nephrons based onlength of loop:

1. short-looped (cortical)nephrons

great majority renal corpuscles in

outer portions of cortex

loops form part ofmedullary rays butbarely make it to

medulla

2. long-looped(juxtamedullary) nephrons

1/7thof nephrons in cortex but near

corticomedullary

junction

loops go deep intomedulla.

- Subsegmenta) thick descending limbb) thin limbc) thick ascending limb

- starts at point of contact ofascending thick limb of loop of

Henle with vascular pole of renal

corpuscle

- functions: reabsorbs a little

amount of water and

sodium ions from

glomerular filtrate secretes potassium and

hydrogen ions intoglomerular filtrate.

- shorter, less convoluted andbigger lumen than proximal

convoluted tubule

- cuboidal epithelial cells have nobrush borders

- distinct cell boundaries


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Henles loop

- Subsegments:THICK DESCENDING LIMB THIN LIMB THICK ASCENDING LIMB

a.k.a. descending straighttubule; proximal straight

tubule

partly in cortex; partly inmedulla

same structure andfunction as proximal

convoluted tubule.

diameter = 15m (descending straight=60m)

lined by simple squamous epithelium further concentrates glomerular filtrate

morphologically identicalwith distal convoluted

tubule.

JUXTAGLOMERULAR COMPLEX

- a.k.a.: JG complex; Jg apparatus- Three (3) atypical cells associated with each

other in vascular pole of renal corpuscle

a. juxtaglomerular cellsb. macula densac.

extraglomerular mesangial cells

JUXTAGLOMERULAR (JG)

CELLSMACULA DENSA

EXTRAGLOMERULAR MESANGIAL

CELLS

- in tunica media ofafferent arteriole before

arteriole enters vascular

pole

- polyhedral cells that arelarger than ordinary

smooth muscle cells

- produce renin andpossibly, erythropoietin

and thrombopoietin.

- modified epithelial cells of tubule- at start of distal convoluted tubule that is in

contact with vascular pole of parent renal

corpuscle

- cellso crowded and narrowero nuclei appear intensely stainingo intimately close to JG cells of afferent

arterioleo sensitive to ion content and volume of

fluid in convoluted distal tubule

o generate molecular signals that promoterenin secretion by JG cells

- a.k.a. pole-cushion cells;lacis cells; Goormaghtigh

cells; polkissen

- light-staining cells betweenmacula densa and afferentarteriole

- probably involved in signaltransmission between

macula densa and

glomerular mesangial cells


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2. intrarenal ductsa. collecting tubulesb. papillary ducts- functions of both:

o serve as conduits for urineo secrete potassium and acidify urine (collecting tubules)

collecting tubules

- segments:- arched collecting tubules- straight collecting tubules - main components of medullary rays

- epithelium : simple cuboidal but progressively becomes taller

papillary ducts

- a.k.a. papillary duct (of Bellini)- formed by convergence of straight collecting tubules- empties into a minor calyx; about 25 papillary ducts/

minor calyx

- lined by tall columnar epithelium

j. Interstitium- refers to scanty connective tissue in peritubular and periarterial spaces

o extracellular substance glycosaminoglycan-rich ground substance collagenous fibers

o cellular elements fibroblasts mononuclear cells: probably belonging to mononuclear phagocyte system interstitial cells

fibroblast-like cells but processes thinner

some say they produce prostaglandins while others say they secrete ahormone whose effects are opposite those of renin.

k. Intrarenal urinary passages- histology similar to ureter and urinary bladder- minor calyx : receives urine from papillary ducts- major calyx: union of several minor calyces- renal pelvis: union of major calyces

B. URETER, URINARY BLADDER AND URINARY PASSAGEIN KIDNEY

histologic layers1. mucosa2. muscularis3. adventitia/serosa

(note: no distinct submucosa).


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MUCOSA MUSCULARIS ADVENTITIA/ SEROSA

- epithelium :o transitional

- lamina propria:o devoid of glands except for mucus

glands near internal sphinter of

urinary bladder

- poorly defined- outer layer - mostly circularly-arranged- inner layer - mostly longitudinally-arranged- in urinary bladder, well-developed

o three indistinct but definite layerso middle layer contains the

circularly-arranged muscles

- adventitiaexcept for

upper part of

bladder which is

serosa.

C. URETHRAMALE FEMALE

segments:

1. prostatico proximal segment, 3-4 cm longo traverses prostate gland

2. membranouso second segment, about 1 cm longo traverses sphincter urethrae muscle

3. spongy (penile urethra; cavernous urethra)o third and longest segment, about 15 cm

long

o traverses peniso terminates in external urethral orifice

(meatus).

- much shorter than male; only 4 cm long- also penetrates sphincter urethra muscle- mucosa

o epithelium is transitional in initial segment butnonkeratinized stratified squamous

epithelium in rest.

o many small, mucus-secreting urethral glandsthat open into lumen

- muscular coat like in male- distal segment surrounded by circularly-arranged

striated (voluntary) muscle fibers that belong to

sphincter urethrae muscle (external sphincter of

urethra).


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MALE URETHRA FEMALE URETHRA

Male urethra segments:

PROSTATIC MEMBRANOUS SPONGY (PENILE URETHRA; CAVERNOUS

URETHRA)- contains opening of prostate gland

and ejaculatory duct (common

passageway for sperms and secretions

of seminal vesicle)

- transitional epithelium- lamina propria

o small urethral glands of (Littre) branched, tubuloalveolar,

mucus-secreting glands (also

present in other segments of

male urethra)

- external to lamina propria are smoothmuscle fibers - form internal urethral

sphincter.

- structurally similar toprostatic urethra

- but epithelium ispseudostratified columnar

- surrounded by circularly-arranged striated

(voluntary) muscle fibers

that belong to the

sphincter urethrae muscle

(the external sphincter of

the urethra)

- pseudostratified columnarepithelium except at external

urethral meatus where epithelium

becomes stratified squamous,

nonkeratinized

- receives ducts of bulbourethralglands (of Cowper)

- pair of glands; 1 cm in diametereach

- embedded in sphincter urethraemuscle on either side of

membranous urethra.

SPONGY (PENILE URETHRA; CAVERNOUS URETHRA)

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