Excretion T2 W8

Excretion and elimination

Excretion definition

Removal of metabolic waste (metabolic = metabolism)

Metabolic waste definition

Left over substacnes from metabolic processes (e.g cellular respiration), which cannot be used by the body and must be removed.

Metabolic waste includes

Water, carbon dioxide, lactic acid, salts, bile pigmets and nitrogenous wastes (ammonia, urea, uric acid and creatinine).

What happens when waste isn’t removed

Reaches a harmful concentration and then interfers with cell’s ability to carry out its function.

Elimination definition (is not a excretory process but removes bile pigment)

Elimination is the removal of indigestible materials, bacteria and bile pigments from the body.

What is bile pigment and how is it removed from body

•The haemoglobin in old red blood cells is broken down in the liver.

•Bilirubin is a by product of this reaction, which is excreted into the bile.

•It is removed from the body as bile pigments in the faeces

Lungs excretory function

Remove from the body the two major cellular waste products of cellular respiration – carbon dioxide and water.

Skin excretory function

⚬The skin has many roles, one of which is the cooling mechanism of sweating.

⚬Sweat contains metabolic wastes: water, salt, urea, lactic acid.

Alimentary canal excretory function

⚬Removal of bile pigments in faeces.

⚬These pigments are the breakdown products of haemoglobin from red blood cells.

Liver excretory function

⚬Liver processes excess amino acids to form nitrogenous wastes like urea (deamination).

⚬Breaks down haemoglobin.

⚬Detoxifies alcohol and other drugs like antibiotics.

⚬Deactivates many hormones.

Kidneys excretory function

⚬The main organs of excretion - produce urine.

What does urine contain

￭Water

￭Salts

￭Nitrogenous wastes – urea, ammonia, uric acid, creatinine

￭Hormones

￭Medications like antibiotics

Examples of nitrogenous wastes

•Ammonia

•Urea

•Uric Acid - produced by the metabolism of purines, which come from the breakdown of nucleic acids

•Creatinine - produced in muscle cells from the breakdown of creatine phosphate, an energy-rich molecule (you are not required to know this)

Gout

•Gout is a form of arthritis (inflammation) that is characterised by sudden, severe attacks of pain, redness and tenderness in joints, usually the big toe.

•Uric acid is a waste product formed from the breakdown of a molecules called purines (nitrogenous bases).

How is gout caused

Gout is caused by deposits of uric acid crystals in a joint.