Urinary system Summary PDF

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Urinary system summary notesGeneral Functions: Removal of metabolic wastes & toxins Elimination of excess nutrients & excess hormones Regulation of blood volume & pressure Regulation of electrolytes & body pH Erythropoiesis Aid in calcium absorption Urinary SystemOrgans: Kidneys – cl...

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Urinary system summary notes General Functions: 1. Removal of metabolic wastes & toxins 2. Elimination of excess nutrients & excess hormones 3. Regulation of blood volume & pressure 4. Regulation of electrolytes & body pH 5. Erythropoiesis 6. Aid in calcium absorption

Urinary System Organs: Kidneys – clean and filter blood Ureters – tubes that take urine to bladder Bladder – stores urine until eliminated Urethra – removes urine from body 1. 2. Ureters -the rest of urinary system is “plumbing”  renal pelvis funnels urine to paired ureters  ‡tubular extensions of renal pelvis  peristalsis moves urine along to bladder 3. Bladder  small, size of walnut when empty  can hold up to 800 ml (24 oz) voluntarily  where urethra passes through pelvic floor it is encircled by and external urethral sphincter of skeletal muscle‡ provides voluntary control 4. Urethra  male:~18 cm long  female: tube 3-4 cm long Kidney Histology Gross Anatomy  Location - retroperitoneal ‡ behind parietal peritoneum, just above waist  surrounded by renal capsule ‡ barrier against trauma and spread of infections (tough layer of dense regular connective tissue)  hilum = indentation where vessels and ureter attach  The kidney is organised into many lobes, organised in a pyramidal structure, where the outer portion is made up of cortex, and the inner portion is made up of the medulla.  Functional unit - Consists of (a) nephron, (b) blood vessels, (c) interstitium, and (d) collecting tubule. Frontal Section of Kidney  Cortex -outer zone of kidney  Medulla -interior of kidney 

Renal cortex contains o Upper portions of nephrons (glomerulus/bowman’s capsule & tubules) o Upper portions of the collecting ducts

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Renal medulla consists of o Parts of nephrons called loops of Henle o The major portions of the collecting ducts that transport urine to the calyces. o The major calyces and minor calyces that carry the urine to the renal pelvis

Nephron = Kidney Functional Unit Afferent arteriole and Efferent Arteriole Renal Corpuscle Glomerulus Bowman’s Capsule Renal Tubules Proximal convoluted tubule Descending Loop of Henle, thin Ascending Loop of Henle, thick Distal convoluted tubule Kidney Cortex Collecting Duct with glomeruli (surrounded Bowman’s capsule) and

tubules

Kidney Medulla (Collecting ducts, tubules, loop of Henle)

A. Renal Corpuscle - Glomerulus (filtration)+ Bowmans Capsule 1. Histology a) Glomerulus (Tuff of capillaries)  Capillary, thin walled, fenestrated with large pores no diaphragm in pores b) Bowman’s Capsule  Visceral Layer (contact with glomerulus)  Podocytes – modified epithelial cells  Parietal Layer (external, outer wall  Simple Squamous Epithelium  Basement membrane with a thin layer of elastic fibers

B. Renal tubules Proximal Convoluted Tubule, PCT Histology Cuboidal epithelium with round, centrally located nucleus Cytoplasm, acidophilic Cell margins difficult to see Lumen, large in living, collapsed (reduced) in fixed tissue Brush border (Microvilli Base of cells folded with many mitochondria. Located in the cortex but then descends into the medulla to become continuous with the loop of Henle Function Reabsorption (90% of solutes) & Secretion 100% of glucose reabsorbed Water reabsorption by osmosis Active Transport & Passive Diffusion Loop Of Henle Histology Consists of several parts: Descending limb, thin with wide lumen Ascending limb, thin segment- Squamous epithelium Thick segment resembles DCT (simple cuboidal) Function Counter Current Produces Sodium concentration gradient in the adrenal medulla Distal Convoluted Tubule, DCT ascends into the cortex Histology Cuboidal Epithelium Smaller than PCT, more cells per cross section Less Acidophilic cytoplasm

No Brush Border, Larger Lumen Poor lateral margins Function Secretion of uric acid, ammonia, creatinine + + Aldosterone Na in and K out Collecting Duct Histology Straight through Cortex and Medulla, open in a renal papilla Small collecting ducts = Cuboidal Epithelium Large collecting ducts, near Papilla = Columnar Epithelium Cytoplasm stains weakly, clear halo around nucleus Clear Lateral margins Function Impermeable to water ADH controls permeability to water Transports filtrate and Empties into Calyces of renal pelvis Renal blood supply: renal artery to interlobar arteries to afferent arterioles which give rise to the capillaries in the glomeruli. Efferent arterioles leave the renal corpuscle.

Calyces, Renal Pelvis, Ureter, Urinary Bladder  Similar Histological Structures Mucosa - Transitional epithelium Lamina Propria - Loose and Dense Connective tissue Smooth Muscle - woven sheath, helical arrangement Urinary Bladder Histology Wall – thick and muscular – folded into rugae when empty 3 wall layers: Mucosa - Transitional epithelium (approx. 5 rows) Muscularis – 3 layers of Smooth Muscle - woven without distinct layers, runs in all directions Adventitial – fibrous, anchors bladder to pelvic floor

Lumen

Transitional epithelium

LOCT of lamina propria

Ureter Histology (one per kidney) – is a long, straight muscle-walled tube Mucosa - Transitional epithelium, thick,fibroelastic lamina propria,  No mucosal or submucosal glands and no submucosa Layer of Smooth Muscle outside the mucosa - woven sheath, helical arrangement - Smooth Muscle becomes longitudinal as it reaches the Bladder ureter

Urethra Histology  single tube, connects bladder to environment  -lined with transitional epithelium (male)  -passes through band of skeletal muscle that forms external urethral sphincter, under voluntary control, relaxation results in micturition

Summary of renal epithelium       

Bowman’s Capsule – simple squamous epith. PCT– simple cuboidal epith. with microvilli DCT - simple cuboidal epithelium Collecting Duct – simple columnar epithelium (predominant type) Thick Loops of Henle – simple cuboidal epith. Thin Loops of Henle – simple squamous epithelium Ureter, Bladder, Urethra – urothelium (transitional epithelium)

View chart on Wheater’s page 325...