EXCRETION IN HUMANS
• Metabolic wastes → diffuses from cells via tissue fluid into blood.
• Metabolic waste in blood → to various excretory organs →removes waste from
bloodstream & excreted out of the body.
EXCRETORY ORGANS
LUNGS:
Excretes CO2, water vapour, & heat
KIDNEYS & BLADDER:
• Excretes urine.
• Urine: excess water, mineral salts, nitrates (urea, uric acid, creatine).
• Urea: transports via blood to kidneys + excreted in urine.
• Gall pigments: end up in small intestine as bile salts in faeces.
SKIN:
• Sweats via sweat glands
• Sweat: excess water, salt, small amount of urea
Metabolic wastes and their origins
• CO2 → product of cellular respiration
• Excess water → product of cellular respiration & ingestion of fluids + food
• Urea → formed through deamination of excess amino acids in liver.
• Uric acid → end product of metabolism of nucleic acid.
• Creatine → formed in cells by creatine phosphates.
• Gall pigments → formed during breakdown of haemoglobin in liver
, STRUCTURE
• Consists of the two kidneys, two ureters, bladder, & urethra
• 2 types of blood vessels, renal arteries & veins
• 2 kidneys → in abdominal cavity, either sides of spinal column, just underneath
diaphragm.
• Kidneys receive oxygenated blood, rich in metabolic wastes, through renal
artery.
• O2 -rich blood → transported away from kidneys through renal veins once
filtered from all the metabolic wastes.
• 2 thin tubules, the ureters, each connect separately to bladder.
• Bladder → thin-walled, muscular sac that temporarily stores urine.
• Urethra → tube that transports urine from bladder to external environment.
• Sphincter → at base of bladder, controls flow of urine to urethra.
STRUCTURE OF THE KIDNEYS
EXTERNAL STRUCTURE
• Kidneys → dark red, bean-shaped organ, concave side towards spinal column.
• Indent in middle of concave side, called the hilum (renal port), where renal artery
enters kidney & where renal vein + ureter exits kidney.
• Metabolic wastes → diffuses from cells via tissue fluid into blood.
• Metabolic waste in blood → to various excretory organs →removes waste from
bloodstream & excreted out of the body.
EXCRETORY ORGANS
LUNGS:
Excretes CO2, water vapour, & heat
KIDNEYS & BLADDER:
• Excretes urine.
• Urine: excess water, mineral salts, nitrates (urea, uric acid, creatine).
• Urea: transports via blood to kidneys + excreted in urine.
• Gall pigments: end up in small intestine as bile salts in faeces.
SKIN:
• Sweats via sweat glands
• Sweat: excess water, salt, small amount of urea
Metabolic wastes and their origins
• CO2 → product of cellular respiration
• Excess water → product of cellular respiration & ingestion of fluids + food
• Urea → formed through deamination of excess amino acids in liver.
• Uric acid → end product of metabolism of nucleic acid.
• Creatine → formed in cells by creatine phosphates.
• Gall pigments → formed during breakdown of haemoglobin in liver
, STRUCTURE
• Consists of the two kidneys, two ureters, bladder, & urethra
• 2 types of blood vessels, renal arteries & veins
• 2 kidneys → in abdominal cavity, either sides of spinal column, just underneath
diaphragm.
• Kidneys receive oxygenated blood, rich in metabolic wastes, through renal
artery.
• O2 -rich blood → transported away from kidneys through renal veins once
filtered from all the metabolic wastes.
• 2 thin tubules, the ureters, each connect separately to bladder.
• Bladder → thin-walled, muscular sac that temporarily stores urine.
• Urethra → tube that transports urine from bladder to external environment.
• Sphincter → at base of bladder, controls flow of urine to urethra.
STRUCTURE OF THE KIDNEYS
EXTERNAL STRUCTURE
• Kidneys → dark red, bean-shaped organ, concave side towards spinal column.
• Indent in middle of concave side, called the hilum (renal port), where renal artery
enters kidney & where renal vein + ureter exits kidney.
