Excretory: Disposal & Osmoregulation

Excretion: Disposal of nitrogen-containing wastes

Osmoregulation: Control of gain and loss of water and solutes

Osmoregulation based largely on regulating solutes

Water follows the movement of solutes by osmosis

Excretion: Aquatic Animals

Animals must dispose of nitrogenous waste Metabolism produces nitrogenous wastes from breakdown of proteins and nucleic acids

Most aquatic animals dispose of their nitrogenous wastes as ammonia

Highly soluble in water Diffuses rapidly across cell membranes

Excretory: Saltwater Fish

Excretion: Land Animals

Land animals convert ammonia to less toxic compounds Can be safely stored and transported in the body Released periodically by excretory system Requires energy for conversion Different adaptations and type of reproduction determine excretion as urea or uric acid

Excretory: Disposal & Osmoregulation

Urea Excreted by mammals, most amphibians, sharks, and some bony fishes

Can be stored in concentrated solution but requires water for disposal

Uric acid Excreted by birds, reptiles, insects, some amphibians

Excreted as solid paste for water conservation

Uses more energy for excretion

Excretory

Excretory: Waste Protein and nucleic acid breakdown - nitrogen-containing wastes toxic by-products of Ammonia poisonous but soluble and easily disposed of

Urea less toxic, easy to store and excrete

Some land animals save water by excreting a virtually dry waste

Excretory: Waste in Urine Urea – from amino acid breakdown

Uric Acid – from nucleic acid breakdown

Creatinine – muscle metabolism waste product

Excretory System The excretory system

expels wastes regulates water and salt balance

Two human kidneys each contain ~ million nephrons

Urine leaves kidneys via ureters

Stored in urinary bladder

Excretory Systen

Each nephron: folded tubule and associated blood vessels

Nephrons extract filtrate from blood

Refine filtrate into much smaller amount of urine

Figure 25.9D

Bowman’s capsule

Arteriolefrom renalartery

Arteriolefrom glomerulus

Branch ofrenal vein

Glomerulus

Capillaries

Fromanothernephron

Collectingduct

1 Proximal tubule

2 Loop of Henlewith capillarynetwork

3 Distaltubule

D. DETAILED STRUCTURE OF A NEPHRON

LE 25-11

Blood

Bowman’scapsule

Cortex

Medulla

Proximal tubule

Nutrients H2OHCO3NaCI

HSomedrugsand poisons

Loop ofHenle

H2O

NaCI

NaCI HCO3

H2O

HK

NaCI

Collectingduct

Distal tubule

H2O

Urea

NaCI

Urine (to renal pelvis)

Filtrate compositionH2ONaCI

H

HCO3

Urea

GlucoseAmino acidsSome drugs

Reabsorption

Secretion

– –

–

Excretory: Filtration Filtration (Bowman’s capsule)

Blood pressure forces water and many solutes from blood (glomerulus) into nephron

Excretory: Reabsorption / Secretion Controlled secretion of H+ and reabsorption of bicarbonate ions help regulate blood pH

Secretion also includes active transport of drugs and poisons

Reabsorption of salts and urea allow osmotic reabsorption of water

Excretion: Reabsorption / Secretion PROXIMAL TUBULE – always reabsorb glucose and amino acid- sometimes water, sodium, potassium, calcium depending on need

Secretionurea, creatinine, ions, drugs and toxins

Excretory: Reabsorbing Water LOOP OF HENLE- much water reabsorbed via active transport of salt

- salt concentration in kidney higher in medulla

- Longer loop – more water conservation (desert animals)

Excretory: Reabsorption/Secretion DISTAL TUBULE- specialized “Urine fine tuning”

- Aldosterone hormone – increases amount of sodium reabsorbed into blood (water follows)

Excretory: Water Reabsorption in Collecting Duct Water reabsorbed ADH (antidiuretic hormone) – cause collecting walls to be permeable to water to be reabsorbed

Caffeine interferes with ADH (dehydration)

Excretory: Regulates Blood Pressure Releases RENIN when blood pressure low- enzyme that causes production of chemical (angiotensin II) to constrict blood vessel

- Angiotensin II increase aldosterone production

Excretory: Dialysis

Homeostasis: Liver It assists the kidneys by making urea from ammonia

breaking down toxic chemicals

Liver Blood from intestines flows through the liver before distribution to the rest of the body Allows liver to adjust blood’s chemical content