Excretion
Excretion in Plants
Two waste products: Carbon dioxide and oxygen
- CO2 is produced in respiration
- Oxygen is a product of photosynthesis
Excretion in Humans
The metabolic activities in human cells produce many toxic waste products that need to be excreted.
Carbon dioxide is a waste produced from respiration.
- If it remained in cells, it would change their pH and affect the activity of enzymes
- It is removed by diffusion from respiring cells into the plasma and then into the lungs
The skin also plays a minor part in excretion
- Sweat contains water and some minerals such as sodium and chloride ions (salt)
Waste products of many cell processes dissolve in the blood and are carried to the kidneys, where they are
excreted.
- These products include urea, produced from the breakdown of excess amino acids by the liver
- People who eat a lot of protein, produce a lot of urea
The urinary system
Humans have two kidneys under the rib cage
- Kidneys are supplied with blood through the renal arteries and leaves through the renal veins
Inside the kidneys, the blood is filtered to remove waste substances
- Including: water, urea, mineral ions = urine
Urine flows out of the kidneys down the ureters and into the bladder.
The urine is stored in the bladder until a ring of muscle at the base is relaxed.
The urine then flows out the bladder, through the urethra.
Urinary system: structure and function
Kidney Blood is filtered here to remove waste substances, water is regulated and urine is formed
Ureter This carries the urine from the kidneys to the bladder
Bladder This is where the urine is stored until a ring of muscle at the base is released
Urethra This is how urine flows out of the bladder to the environment
Organs of excretion
1. Lungs
2. Kidneys
3. Skin
,
Excretion in Plants
Two waste products: Carbon dioxide and oxygen
- CO2 is produced in respiration
- Oxygen is a product of photosynthesis
Excretion in Humans
The metabolic activities in human cells produce many toxic waste products that need to be excreted.
Carbon dioxide is a waste produced from respiration.
- If it remained in cells, it would change their pH and affect the activity of enzymes
- It is removed by diffusion from respiring cells into the plasma and then into the lungs
The skin also plays a minor part in excretion
- Sweat contains water and some minerals such as sodium and chloride ions (salt)
Waste products of many cell processes dissolve in the blood and are carried to the kidneys, where they are
excreted.
- These products include urea, produced from the breakdown of excess amino acids by the liver
- People who eat a lot of protein, produce a lot of urea
The urinary system
Humans have two kidneys under the rib cage
- Kidneys are supplied with blood through the renal arteries and leaves through the renal veins
Inside the kidneys, the blood is filtered to remove waste substances
- Including: water, urea, mineral ions = urine
Urine flows out of the kidneys down the ureters and into the bladder.
The urine is stored in the bladder until a ring of muscle at the base is relaxed.
The urine then flows out the bladder, through the urethra.
Urinary system: structure and function
Kidney Blood is filtered here to remove waste substances, water is regulated and urine is formed
Ureter This carries the urine from the kidneys to the bladder
Bladder This is where the urine is stored until a ring of muscle at the base is released
Urethra This is how urine flows out of the bladder to the environment
Organs of excretion
1. Lungs
2. Kidneys
3. Skin
,
