Unit IV: RegulationUrinary System

Chapter 24: pp. 885-891

Chapter 23: pp. 847-856

Water Balance

• Total body water for 150 lb. male = 40L

• Fluid compartments

– 65% ICF

– 35% ECF

• 25% tissue fluid

• 8% blood plasma, lymph

• 2% transcellular fluid (CSF, synovial fluid)

Water Movement in Fluid Compartments

Osmosis Capillary filtration

Capillaries; Cells; or Lymphatic System

• Electrolytes play principle role in water distribution and total water content

Fluid Balance

Preformed water

Water Loss

• Loss varies greatly with environment and activity

– respiratory loss : with cold, dry air or heavy work

– perspiration loss : with hot, humid air or heavy work

• Sensible water loss– urine and abundant sweating

• Insensible water loss

– breath and cutaneous transpiration

• Obligatory water loss

– Expired air, cutaneous transpiration, sweat, feces, minimum urine output (400 ml/day)

Regulation of Fluid Intake

Hypothalamus

Regulation of Output

•Controlled by urine volume

•Support existing fluid levels and slow rate of loss

•Na+ reabsorption and ADH

•Osmoreceptors – group of neurons in hypothalamus, respond to osmolarity

Urinary System

2 kidneys

2 ureters

Urinary bladder

Urethra

Kidney Functions

Primary role in excretion, other functions:

• Filters blood plasma

• Regulates

– osmolarity of body fluids, blood volume, BP

– acid base balance

• Secretes

– erythropoietin and renin

– calcitriol

• Gluconeogenesis

Nitrogenous Wastes

• Urea– proteinsamino acids NH2 removed

forms ammonia, liver converts to urea

• Uric acid– nucleic acid catabolism

• Creatinine– creatine phosphate catabolism

Thermometer

Shunt

ArteryVein

Bloodpump

Bubbletrap

Cutaway viewof dialysischamber

Flowmeter

Todrain

Dialysisfluid

Dialysistubing

Renal Failure

• Blood urea nitrogen (BUN)– 10-20 mg/dL– azotemia: BUN, nitrogenous wastes in blood

– uremia: toxic effects as wastes accumulate

• Renal insufficiency– Hemodialysis:

Excretion

• Separation of wastes from body fluids and eliminating them.

– respiratory

– integumentary: water, salts, lactic acid, urea

– digestive: water, salts, CO2, lipids, bile pigments, cholesterol

– urinary: many metabolic wastes, toxins, drugs, hormones, salts, H+ and water

Anatomy of Kidney

• CT coverings– renal fascia– perirenal fat capsule (adipose capsule)– fibrous (renal) capsule

Anatomy of Kidney

• Renal Parenchyma:

– Renal cortex: outer 1 cm

– Renal medulla: renal columns, pyramids - papilla

• Renal sinus

– Minor calyx

– Major calyx

– Renal pelvis ureter

Renal vein

Arcuate vein

Interlobar veins

Renal artery

Cortical radiate veins

Segmental artery

Interlobar artery

Arcuate artery Cortical radiate arteries

Afferent arterioles

Glomerulus toefferent arterioles

to capillaries ofthe nephron

Renal Circulation

Efferent arteriole

Glomerulus inrenal corpuscle

Afferent arteriole

Peritubular capillaries

To the corticalradiate vein

A cortical nephron

Renal Circulation

Efferent arteriole

Capillaries ofthe vasa recta

Afferent arteriole

Peritubular capillaries

To corticalradiate vein

A juxtamedullary nephron

NephronRenal Corpuscle

• Glomerulus and Bowman’s capsule (glomerular)• Glomerular filtrate collects in capsular space flows into renal

tubule

NephronRenal Tubule

• Proximal convoluted tubule (PCT)– simple cuboidal with brush border

• Nephron loop - descending and ascending limbs– thick segment (simple cuboidal)– thin segment (simple squamous)– Creates osmotic gradient thru counter-current multiplication

• Distal convoluted tubule (DCT)– Cuboidal epithelium; end of nephron

• Collecting duct– simple cuboidal– Papillary duct

Renal medulla

The thin descendinglimb is permeable to water, but impermeableto solutes, includingurea.

KEY

Urea

Renal cortex

ClNa

The thick ascendinglimb of the nephronloop is impermeable to water and solutes.

The DCT andthe collectingducts areimpermeableto urea buthave variablepermeabilityto water.

Waterreabsorption

Variable waterreabsorption

NephronRenal Tubule

Flow of Filtrate

– Bowman’s capsule PCT nephron loop DCT collecting duct papillary duct minor calyx major calyx renal pelvis ureter urinary bladder urethra

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Renal capsule

Collecting ductNephron

(a)

(c)

Cortical nephron

CortexMedulla

GlomerulusGlomerular capsule

Renal corpuscle:

Nephron loop:Descending limbAscending limb

Thick segmentThin segment

Flow of tubular fluidFlow of blood

Key

(b)

Renalcortex

Renalmedulla

Renalpapilla

Minorcalyx

Efferentarteriole

Afferentarteriole

Proximalconvolutedtubule (PCT)

Distalconvolutedtubule (DCT)

Collectingduct (CD)

Papillaryduct

Collectingduct

Nephronloops

Juxtamedullarynephron

Convoluted tubules(PCT and DCT)