1 urinary system

7/30/2019 1 Urinary System

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URINARY SYSTEM

1. Kidneys2. Ureters

3. Urinary Bladder

4. Urethra


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KIDNEYS

Excrete excess water and waste products

of metabolism

Maintain extracellular fluid volume

Control Acid-Base balance

Endocrine function- Erythropoietin

- Renin


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URINIFEROUS TUBULES

NEPHRON- Renal Corpuscles

- Tubules

COLLECTING TUBULE


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Renal Corpuscle


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GLOMERULUS

1. Podocytes

2. Basement membrane

3. Endothelial cells4. Mesangial cells


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PODOCYTES

Free ribosomes

Few RER

Few mitochondria

Prominent GOLGI

Abundant ACTIN


9/46Filtration Slits


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Filtration slits- 25 nm wide

Diaphragm 6 nm thick


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Basement Membrane

- Fusion of two basal laminae

- Electron microscope:

Lamina densa- collagen IV, lamininLamina rara- fibronectin

matrix- heparan SO4 (negative charge)

- Filtration barriera. physical lamina densa

b. charge- anionic matrix


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Endothelial Cells

Fenestrated (70-90 nm diameter)


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BLOOD FILTER

FENESTRATED ENDOTHELIUM

BASAL LAMINA

FILTRATION SLITS


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Mesangial Cells

- extracellular matrix synthesis

- support to capillary walls

- may act as macophages


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TUBULES


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PROXIMAL TUBULE

-Acidophilic cytoplasm

-Brush border & canaliculi

-Pinocytic vesicles

-Abundant mitochondria

-Na/K ATPase pump at basolateral membrane


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PROXIMAL TUBULE CELLS


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PROXIMAL TUBULE

Reabsorbs glucose and amino acids from

the glomerular filtrate

Reabsorbs Sodium and water (70% of

glomerular filtrate)

- Sodium Potassium ATPase Pump


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LOOP OF HENLE

Involved in water retention

Maintain hypertonicity of

the medulla

- active transport of NaCl

from tubule to interstitium

- impermeable to waterexcept thin descending


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DISTAL CONVOLUTED TUBULE

-Lack microvilli & canaliculi

-Larger lumen

-Elaborate basal membrane invaginations

-Basal mitochondria


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DISTAL TUBULE

Active reabsorption ofSodium and

Chloride ions (ALDOSTERONE)

Impermeable to water

MACULA DENSA

- columnar cells

- closely packed nuclei

- golgi complex in basal region


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MACULA DENSA

-Regulate GFR

-Sensitive to Chloride ion content in tubular fluid

-Produce molecular signals that constrict afferent arterioles


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Distal Tubule

Ion exchange site

- Na absorption & K secretion

(Aldosterone influenced)

Acid- base balance

- secretes Hydrogen & ammonium ions

into tubular urine


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COLLECTING TUBULES &

DUCTS


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COLLECTING TUBULES &

DUCTSCuboidal to columnar epithelium

Penetrate the medulla to form the Papillary

Ducts of Bellini & drain into minor calyces

- Responsive to ADH

- water absorption (retention)


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COLLECTING DUCT

CONTROL OF ACID BASE BALANCE

Resorption of bicarbonates (carbonic

anhydrase) = acidification of urine

STIMULATED BY HORMONES

- Antidiuretic Hormone- Atrial Natriuretic factor


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Nephrons

Filtration, absorption & secretionCortical Nephron

Juxtamedullary Nephron

- establish hypertonicity of medulla

- basis for kidney ability to produce

hypertonic urine

- very long Henles loop extending to

medulla (short thick descending, long thin

descending & ascending, thick

descending)


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JUXTAGLOMERULAR COMPLEX

Adjacent to renal corpuscle

MACULA DENSA

JUXTAGLOMERULAR CELLS- afferent arteriole with modified

smooth muscle

- secrete RENIN

EXTRAGLOMERULAR MESANGIAL

CELLS


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JUXTAGLOMERULAR COMPLEX


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ANGIOTENSINOGEN

ANGIOTENSIN I

ANGIOTENSIN II

RENIN

CONVERTING ENZYME

VASOCONSTRICTION ALDOSTERONE SECRETION

BLOOD SUPPLY


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BLOOD SUPPLY


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HISTOPHYSIOLOGY

BLOOD SUPPLY

1,200 ml/min

GLOMERULAR FILTRATE

125 ml/min

URINE OUTPUT

1 ml/min

Urine production

Filtration, absorption & secretion


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Filtration

Positive pressure

- Hydrostatic pressure of blood (45 mmHg)

Opposing pressure- Plasma osmotic pressure (20 mmHg)

- Bowmans fluid hydrostatic pressure

(10mmHg)Glomerular Filtrate = Plasma - Proteins


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COUNTERCURRENT MECHANISM


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VASA RECTA


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Urinary Passages & Bladder

Calyces

Renal pelvis

UreterUrinary bladder

Urethra


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TRANSITIONAL EPITHELIUM

PELVIS AND CALYCES= 2-3 CELLS THICK

URETER= 4-5 CELLS THICK

URINARY BLADDER= 6-8 CELLS THICK

Luminal surface

- Covered with thick plates

- Rich in CEREBROSIDE


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URETER


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URINARY BLADDER


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Urinary BladderEpithelium

Lamina propriaMuscular layer

- indistinct arrangement

- at bladder neck:

a. inner longitudinal circular at prostatic urethra &entire urethra of females (involuntary urethral sphincter)

b. middle layer

c. Outer longitudinal- continue up to prostate in

males & meatus in females

Adventitia/Serosa


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MALE URETHRA

PROSTATIC URETHRA (pars prostatica)

Transitional Epithelium

- ejaculatory ducts

- openings ofprostate gland ducts

MEMBRANOUS URETHRA (pars membranacea)Pseudostratified to Stratified Columnar Epithelium

- Striated mm= External Sphincter Urethrae

PENILE URETHRA (pars spongiosa)

Stratified Columnar Epithelium

- Ducts ofBulbourethral glands

- Ducts ofglands of Littre


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FEMALE URETHRA

Stratified Squamous Epithelium

-Mucous Secreting Cells

Lamina Propria

- Venous plexus

Smooth Muscle Layer

- Inner longitudinal

- Outer circumferential

STRIATED mm- Sphincter

1 urinary system

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