Excretory System

Figure 44.8a

Most aquaticanimals, includingmost bony fishes

Mammals, mostamphibians, sharks,

some bony fishes

Many reptiles(including birds),

insects, land snails

Ammonia Urea Uric acid

Figure 44.2

Selectively permeablemembrane

Solutes Water

Net water flow

Hyperosmotic side: Hypoosmotic side:

Lower free H2Oconcentration

•

Higher soluteconcentration

•

Higher free H2Oconcentration

•

Lower soluteconcentration

•

Figure 44.14b

Kidney Structure

Renalcortex

Renalmedulla

Renal artery

Renal vein

Ureter

Renal pelvis

Figure 44.14d Nephron OrganizationAfferent arteriolefrom renal artery Glomerulus

Bowman’s capsule

Proximaltubule

Peritubularcapillaries

Distaltubule

Efferentarteriolefrom glomerulus

Collectingduct

Branch ofrenal vein

Vasarecta

Descendinglimb

Ascendinglimb

Loopof

Henle

200

m

Blood vessels from a human kidney. Arterioles and peritubular capillaries appear pink; glomeruli appear yellow.

Figure 44.14e

Figure 44.19-2

ThirstHypothalamus

ADH

Pituitarygland

Osmoreceptors inhypothalamus trigger

release of ADH.

STIMULUS:Increase in blood

osmolarity (forinstance, after

sweating profusely)

Homeostasis:Blood osmolarity

(300 mOsm/L)

Drinking reducesblood osmolarity

to set point.

H2O reab-sorption helpsprevent further

osmolarityincrease.

Increasedpermeability

Distaltubule

Collecting duct

Collectingduct

ADHreceptor

COLLECTINGDUCT CELL

LUMEN

Second-messengersignaling molecule

Storagevesicle

Aquaporinwater channel

Exocytosis

H2O

H2O

ADH

cAMP

Figure 44.20