communication and excretion Flashcards
what is excretion?
the removal from the body of unwanted products of metabolism. The metabolic products are completely natural.
why do substances need to be excreted?
Almost all the products that are formed in excess by the chemical processes occurring in the cells must be removed by the body. This must happen in order to prevent a build-up which could inhibit enzyme-activity or become toxic.
what is metabolic waste?
A substance that is produced in excess by metabolic processes in the cells; it may become toxic.
what are the 3 main excretory products?
- Carbon dioxide from respiration
- Nitrogen-containing compounds such as Urea (i.e. nitrogenous waste)
- Other compounds, such as the bile pigments found in faeces
what is egestion?
egestion is the elimination of faeces from the body. faeces are the undigested remains of food and are not metabolic products.
name the 4 excretory organs?
- The lungs
- The liver
- The kidneys
- The skin
how are the lungs involved in excretion?
every living cell in the body produces carbon dioxide as a product of respiration
carbon dioxide is passed from the cells of respiring tissue –> bloodstream
from the bloodstream it is transported (mostly in the form of HCO3- ions) –> lungs
in the lungs the carbon dioxide diffuses –> alveoli to be excreted as one breathes out
how is the liver involved in excretion?
the liver has many metabolic roles and some of the products will be passed –> bile for excretion with faeces e.g. the pigment bilirubin
the liver converts excess amino acids –> urea
How are amino acids broken down?
amino acids are broken down by the process of deamination
the nitrogen containing part of the compound is then combined with carbon dioxide to make urea
how are the kidneys involved in excretion?
the urea is passed into the bloodstream to be transported –> kidneys
in the kidneys the urea is removed from the blood to become part of urine
urine is stored in the bladder before being excreted from the body via the urethra
how is urea transported to the kidneys?
urea is transported in solution by being dissolved in plasma
how is the skin involved in excretion?
excretion is not the skin’s primary function. Sweat contains a range of substances including salts, urea, water, uric acid and ammonia. urea, uric acid and ammonia are all excretory products.
what is the importance of the loss of water and salts through sweat?
The loss of water and salts through sweat is important in homeostasis.
What is homeostasis?
Maintaining the water potential of the blood and the body temperature.
how is most carbon dioxide transported in the body as?
most carbon dioxide is transported in the blood as hydrogencarbonate ions
