GEN BIO 2 | Excretory System

Excretion

process of removing wastes from the body; essential to maintain homeostasis

Ammonia

readily soluble in water but highly toxic

Urea

less toxic and requires more energy to form than ammonia

Uric Acid

relatively nontoxic but more expensive to produce; largely water insoluble

Protonephridia

branching excretory organs common in planarian flatworms that rid the body of excess water and soluble wastes

Nephridia

tubular excretory organs common in earthworms that collect coelomic fluid

Malphigan Tubules

these long thin tubules attach to the gut of insects

Fluid Regulation in Marine Bony Fishes

they lose water by osmosis and replace it by gulping seawater and pumping salt out across its gills

Fluid Regulation in Freshwater Bony Fishes

produces a large volume of dilute urine because water continually enters its body by osmosis

Kangaroo Rats and Water Scarcity

• they remain a cool burrow as their nasal passages capture condensed water from exhaled air.

• They form a hypertonic urine and produce almost completely dry fecal material.

• They can survive not drinking water by using metabolic water from cellular respiration.

Excretory System Organs

help remove waste; also part of other organ systems

Lungs in Excretory System

removes CO2

Liver in Excretory System

removes toxins

Skin

produces sweat

Large Intestine in Excretory System

eliminates feces

Human Urinary System

• Excretion of nitrogenous wastes like urea and uric acid

• maintains water-salt balance and acid-base balance in blood

Adrenal Glands

produce hormones that regulate blood pressure

Kidney

maintains homeostasis in blood composition

Nephron

filters blood and forms urine

Bowman’s Capsule

cup-shaped portion of a nephron that encloses glomerulus and receives filtrate from it

Glomerulus

a cluster of capillaries enclosed by Bowman’s capsule

Proximal Tubule

receives filtrate from Bowman’s capsule

Distal Tubule

delivers filtrate to a collecting tubule

Loop of Henle

u-shaped portion of tubule that conducts urine

Collecting Tubule

receives filtrate from several nephrons and delivers it to renal pelvis

Renal Artery

delivers blood to kidney

Renal Vein

conveys blood to bladder

Ureters

convey urine to bladder

Urinary Bladder

stores urine before elimination

Urethra

conveys urine out of blood

Urine Formation Steps

1. Filtration

2. Reabsorption

3. Secretion

Filtration

• small molecules like water, nutrients, salts, and urea, move to inside the capsule

• plasma proteins and blood cells are too large to be part of the filtrate so they remain in blood

Reabsorption

• returns the vast majority of the filtered water and solutes to blood

• K+, Na+, and Cl- ions, glucose, and amino acids return to blood

Secretion

hydrogen ions, uric acid, salts, ammonia, creatinine, and penicillin are eliminated by secretion to rid the body of harmful compounds not filtered into the glomerulus

Acidic Blood

leads to the excretion of hydrogen ions and re-absorption of bicarbonate ions to maintain homeostasis

Basic Blood

the excretion of hydrogen ions and re-absorption of bicarbonate ions does not occur in this scenario

Scare Intake of Water

this leads to the production of small amounts of concentrated urine as the brain produces more ADH

Surplus Intake of Water

this leads to the production of abundant diluted urine as the brain produces less ADH