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24 Cards in this Set

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  • Back
What is excretion?
Removal of metabolic wastes produced in the body
What is elimination?
Removal of of indigestible material from the body
What waste does aerobic respiration lead to?
What waste does deamination of amino acids in liver lead to?
Nitrogenous wastes like urea and ammoniea
How does excretion occur in protozoans and cnidarians?
All cells in contact with external, aqueous environment

Water soluble wastes like ammonia and CO2 pass via simple diffusion

Some freshwater protozoa (paramecium) possess contractile vacuole for active transport of water out (allowing for water pressure and volume maintenance)
How does excretion in annelids occur?
In earthworms, CO2 excretion occurs via moist skin

Two pairs of nephridia in each body segment excrete water, mineral salts, and nitrogenous wastes in the form of urea
How does exretion in arthropods occur?
In insects, CO2 is released from tissue in tracheae which exit to air in spiracles

Nitrogenous wastes are excreted in form of solid uric acid crystals (adaptation for minimizing water loss)

Mineral salts and uric acid accumulate in malphigian tubules and are then transported to the intestine to be expelled
What are the principle organs of exretion in humans?
lungs, liver, skin, kidneys
How are lungs involved in excretion?
CO2 and water vapor diffuse from blood and continually exhaled
How is skin involved in excretion?
Sweat glands in skin excrete water and dissolved salts and small amount of urea
How is the liver involved in excretion?
Process nitrogenous wastes, blood pigment wastes, and other chemicals for excretion

Urea is produced by deamination of amino acids in the liver and diffuses into blodd for ultimate excretion in the kidneys
What do the kidneys do?
Maintain osmolarity of the blood, excrete numerous waste products and toxic chemicals, conserve glucose, salt, water
What is the subunit of a kidney called and how many are there per kidney?
Nephron w/ 1 million per kidney
What are the three regions of the kidney in->out?
Renal Pelvis -> inner medulla -> outer cortex
What are the parts of a nephron?
Bulb called Bowman's capsule -> proximal convoluted tubule -> loop of henle -> distal convoluted tubule -> (cortex, medulla, pelvis, ureter, urinary bladder)
What is the nephron mostly surrounded by?
Complex peritubular capillary network to facilitate reabsorption of amino acids, glucose, salts, and water
What are the three steps in urine formation?
Filtration, Secretion, Reabsorption
How does the filtration part of urine formation occur?
Blood pressure forces 20% of blood plasma entering glomerulus through capillary walls into surrounding Bowman's Capsule

Fluid and small solutes entering nephron are called filtrate

Filtrate is isotonic with blood plasma

Particles too large to filter through glomerulus such as blood cells and albumin, remain in circulatory system

Passive process driven by hydrostatic pressure of the blood
How does the secretion part of urine formation occur?
Nephron secretes substances such as acids, bases, ions like potassium and phosphate from the interstitial fluid into the filtrate by both passive and active transport

Materials are secreted from the peritubular capillaries into the nephron tubule
How does the Reabsorption part of urine formation occur?
Essential substances (glucose, salts, amino acids) and water are reabsorbed from filtrate and returned to the blood

Occurs primarily in proximal convoluted tubule and is an active process

Movement of molecules is accomplished via passive movement of water, this results in concentrated urine, which is hypertonic to the blood
How is the nephron able to function?
Through selective permeability of its walls and the maintenance of an osmolarity gradient, nephron reabsorbs nutrients, salts, and water from the filtrate and returns them to the body, thus maintaining bloodstream's solute concentration
What is the osmolarity gradient and how is it established?
Selective permeability of the tubules establishes an osmolarity gradient in the surrounding interstitial fluid

Tissue osmolarity increases from cortex to medulla

Urea and Salt maintain this gradient
How is the concentration of urine achieved?
Counter-current system causes the medium in the medulla of the kidney to be hyperosmolar with respect to the dilute filtrate flowing in the collecting tubule

As filtrate passes through this region of kidney, water flows out via osmosis into capillaries

Osmosis of water is dependent upon permeability of collecting tubules to water which is regulated by ADH (vasopressin)
What is excretion in plants all about?
No specific excretory system in plants

Plants are able to use many of the "waste" products

Excess is released through stomata