exchange surfaces and breathing Flashcards
What are the three main factors that affect the need for an exchange system
- size
- surface area to volume ratio
- Level of activity
How does size affect the need for an exchange system
- In small organisms or the cytoplasm is close the environment in which they live
- diffusion supplies enough oxygen and nutrients to keep the cells alive and active
- multicellular organisms may have several layers of cells
- here any oxygen or nutrients diffusing in from outside have a longer diffusion pathway
- Diffusion is too slow to enable a sufficient supply to the innermost cells
What types of organisms don’t need an exchange system
unicellular organisms like amoeba
How do you work out SA:V
SA=4piR(2)
Volume=4/3piR(2)
What is the surface area to volume ratio in small organisms
- have a large surface area to volume ratio
- Surface area is large enough to supply all the cells with sufficient oxygen
What is a surface area to volume ratio like with larger organisms
- Small surface area to volume ratio
- volume increases but SA doesn’t
How do some large organisms not need an exchange system (shape)
things like the flatworm have a large SA:V of skin so can take in O2
How does the level of activity of an organism affects the need for an exchange system
- some organisms are more active than others
- more metabolic activity takes place
- need good supplies of nutrients and oxygen to supply energy for movement
- This is further increased in animals such as mammals that keep themselves warm
How is a large surface area part of a good exchange surface
provides more space for molecules to pass through
What features make a good ES
- large SA
- Short diffusion distance
- good blood supply
How is a thin barrier a feature of a good exchange surface
reduces diffusion distance
Why is a good supply of blood a feature of a good exchange surface
Maintains a steep conc gradient
What is the need for exchange
Take in O2 and glucose and get ride of waste products (CO2)
What features in organisms make good ES
Intestines: microvilli Lungs Gills Insect tracheal system Leaves Root hair cells
How does the mammalian exchange system work
- Lungs are a pair of inflatable sacks lying in chest cavity
- Air passes into the lungs through the nose and along the trachea bronchi and bronchioles
- finally it reaches tiny airfield sacs called alveoli (surfaces with the exchange of gases takes place)
What is ventilation
-The refreshing of air in the lungs so there is a higher oxygen concentration in the blood and the lower carbon dioxide concentration
How does gaseous exchange in the lungs work
- gases pass by diffusion through the thin walls of the alveoli
- oxygen passes from air in the alveoli to blood in the capillaries
- carbon dioxide passes from blood to the air in the alveoli
- Lungs must maintain a steep concentration gradient in each direction in order to ensure that diffusion can continue
What are the features of the Trachea
- Pipe is supported by a layer of cartilage that holds the trachea open and prevents it from collapsing
- rings are incomplete to allow it to bend when food is entering down the oesophagus behind
- Trachea lined with ciliated epithelium cells and goblet cells that prevent dust and bacteria from Entering
- Glandular tissue is the loose tissue also produces mucus
What are the certain requirements the airways need to work
- large enough to allow sufficient air to flow without obstruction
- supported to prevent collapse when the air pressure inside is low during inspiration
- Flexible in order to allow movement
What are the key features of the Bronci
- similar structure to trachea but narrower
- also supported by rings of cartilage
- Extensions of the Trachea that split into left/right lung
- Cartilage rings hold the pipe open
What is the purpose of goblet and epithelial cells in the airways
- Goblet cells secrete mucous to trap pathogens
- Cilia waft mucous to the back of the throat where pathogens swallowed and neutralized in the stomach
What are the key features of the bronchioles
- the bronchus split into smaller bronchioles
- Not much cartilage and held open by smooth muscle
- when muscles contract the bronchioles contract this is dependent on air flow
Where does gas exchange occur
respiratory bronchioles and aveoli
What does smooth muscle cause
The airway to constrict
How do asthma attacks occur
- bronchioles smooth tissue can be responsible for asthma attacks
- smooth muscle constricts (when smoke enters e.g)
- bronchioles lumen becomes narrower
- difficult to get air to the gas exchange surfaces
- inhalers act to relax the smooth muscle
What do elastic fibers do
reinflate the airways and aveoli if smooth muscle is constricted
- allows recoil
- in all connective tissue
- prevent bursting in aveoli allow them to recoil and return to original shape