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