exchange surfaces Flashcards
why do organism need to exchange substances
To supply oxygen and glucose for aerobic respiration and other metabolic activities and to excrete the waste products such as carbon dioxide and water
why do multicellular organism need a specialised exchange surface
As organisms increase in size their SA:V ratio decreases. The greater volume results in a longer diffusion distance to the cells and tissues of the organism therefore large multicellular animals and plants have evolved adaptations to facilitate the exchange of substances between their environment. Multicellular organism have a higher metabolic rate so they use up oxygen and glucose faster
what are the features of an efficient exchange surface
“Large surface area
Short diffusion distance (thin)
Good blood supply
Ventilation mechanism “
how are root hair cells adapted to have efficient exchange surfaces
They have root hair cells which increase their surface area which helps increase the rate of absorption of water by osmosis and mineral ions from the soil
how are alveoli adapted to have a efficiency exchange surfaces
“The walls of the alveoli are only one cell thick and these cells are flattened (alveolar epithelium)
This means that gases have a very short diffusion distance so gas exchange is quick and efficient “
how do the alveoli have a good blood supply and ventilation system
They are surrounded by large capillary network which gives each alveolus its own blood supply which constantly takes oxygen away and brings more carbon dioxide. The lungs are ventilated when you breathe in and out so air in alveoli is constantly replaced which helps maintain concentration gradients of oxygen and carbon dioxide
how do fish gills have a good blood supply and ventilation system
Gills have a large network of capillaries that keeps them well supplied with blood and are well ventilated due to the fresh water that constantly passes over them. These help maintain concentration gradient of oxygen.
“what happens when air enters the body ”
It enters the trachea which splits into two bronchi which leads to each lung. Each bronchus branches of into smaller tubes called bronchioles which end in small sacs called alveoli
“function of goblet cells ”
“Present in the trachea, bronchi and bronchioles Secretes mucus which traps microorganism and dust particles in the inhaled air which prevents them reaching the alveoli “
“function of ciliated epithelial cells ”
“Present in trachea, bronchi and bronchioles They have cilia which sweep mucus, dust and bacteria upwards and away from the lungs towards the throat “
“functions of elastic fibres ”
“Found in the alveoli They enable the lung to stretch and recoil which controls the flow of air. This ability to recoil is what makes expiration a passive process “
“function of smooth muscles
“
Smooth muscle can be found throughout the walls of the bronchi and bronchioles. It helps to regulate the flow of air into the lungs by dilating when more air is needed and constricting when less air is needed
“function of cartilage
“
to support the trachea and ensure it stays open while allowing it to move and flex while we breathe. Prevents trachea from collapsing
what happens during inspiration
External intercostal muscles contract and internal intercostal muscles relaxes which causes the ribcage to move outwards and up and diaphragm contracts and flattens. Volume of the thorax increases and the pressure decreases so air is drawn in to the lungs. Its a active process so requires energy
what happens during expiration
External intercostal muscles relax, which causes the ribcage to go downwards and inwards and the diaphragm relaxes and becomes curved . The volume of thorax decreases and the pressure increases so air is forced out of the lungs. It’s a passive process so it doesn’t require energy.
