3.1 Exchange Surfaces Flashcards
What are the features of an efficient exchange surface?
Large surface area to provide more space for molecules to pass through - e.g root hairs in plants
Thin barrier to reduce diffusion distance - e.g alveoli in lungs
Good blood supply to maintain steep concentration gradient so diffusion can occur rapidly - e.g gills in fish
Why is ventilation important?
It ensures that the concentration of the oxygen in the air of the alveolus remains higher than that in the blood
The concentration of carbon dioxide in the alveoli remains lower than that in the blood
Maintaining a steep concentration gradient necessary for efficient diffusion
What is the process of inspiration?
The diaphragm contracts to move downwards and flatten
The intercostal muscles contract to raise the ribs
The volume of the thorax increases and pressure drops below atmospheric pressure
Air is moved into the lungs
(Alveolus contains elastic fibres that stretch during inspiration and recoil to help push air out during expiration)
What is the process of expiration?
The diaphragm relaxed and moves upwards
The intercostal muscles relax and the ribs fall - can contract to push air out more forcefully (sneezing, coughing)
The volume of thorax decreases and is above atmospheric pressure
Air is moved out of lungs
What are the functions of the mammalian lung features?
Large surface area to provide more space for molecules to pass through
Thin barrier to exchange which is permeable to oxygen and carbon dioxide - one cell thick, capillary is close to alveolus walls, squamous cells
Good blood supply to maintain steep concentration gradient
How are the trachea and bronchi adapted to be effective?
Allow the passage of air into the lungs and out again
Lined by ciliated epithelium - goblet cells secrete mucus which traps pathogens and cilia move mucus to the top of he airway where it is swallowed
Supported by rings of cartilage - prevents collapse during inspiration
C shaped cartilage - flexibility and space for food to pass down oesophagus
What is the structure of bronchioles?
The bronchioles are much narrower than bronchi
Larger ones may have cartilage but smaller ones don’t
Wall is comprised mostly of smooth muscle and elastic fibres
What is the function of smooth muscle and elastic tissue?
Smooth muscle can connect to constrict the airway making the lumen narrower - restricts flow of air to and from alveoli
- controlling movement of air - harmful substances in air?
- involuntary action - allergic reaction?
Smooth muscle is elongated again by elastic fibres - as muscle contracts, it deforms elastic fibres/as muscle relaxes, they recoil back to shape
…….acts to dilate the airway
What is a spirometer?
A device that measures the movement of air in and out of the lungs as a person breathes
What is a float-chamber spirometer?
Consists of a chamber of air or medical grade oxygen floating on a tank of water
During inspiration, air is drawn from the chamber so the lid moves down
During expiration, air returns to the chamber so the lid raises up
These movements are recorded on a data logger
What allows the measure of oxygen consumption?
The carbon dioxide rich air exhaled is passed through a chamber of soda lime which absorbs carbon dioxide
What are the precautions that should be taken when using a spirometer?
The subject should be healthy and free from asthma
Soda lime should be fresh and functioning
No air leaks in the apparatus
Mouthpiece should be sterilised
Water chamber must not be overfilled or water may enter air tubes
What is vital capacity?
The greatest volume of air that can be moved by lungs in one breath - measured by taking a deep breath and exhaling all e air possible from lungs
Vital capacity depends on a number of factors:
- age and gender
- size of person
- level of regular exercise
Usually in range of 2.5 - 5 dm3
What is the residual volume?
Volume of air that remains in lungs even after forced expiration that remains in airways and alveoli - usually 1.5 dm3
What is the tidal volume?
The volume of air moved in and out with each breath - at rest approx. 1.5 dm3
What is oxygen uptake?
The volume of oxygen absorbed by the lungs in one minute
As oxygen is taken in, carbon dioxide is released and absorbed by soda lime in the spirometer so volume in air chamber decreases
Decrease can be observed and measured in spirometer trace
Assume - volume of carbon dioxide released equals to volume of oxygen absorbed
What are the factors that oxygen uptake depends on?
Breathing rate
Deeper breaths
How can breathing rate be measured?
By counting the number of peaks in each minute
Why do fish have gills?
To absorb oxygen and release carbon dioxide into water
Each gill consists of two rows of gill filaments (primary lamellae) attached to bony arch
Filaments are very thin and folded into many secondary lamellae (or gill plates)
This provides a very large surface area - blood capillaries carry deoxygenated blood to the surface of the secondary lamellae where exchange takes place
What is countercurrent flow?
Blood flows along the gill arch and out along the secondary lamellae (gill plates)
Blood then flows through capillaries in opposite direction to flow of water over the lamellae - countercurrent flow absorbs maximum oxygen from water
How do bony fish ventilate?
The buccal cavity (mouth) opens and water moves in
Mouth closes and water is pushed through gills
Movements of operculum (flap that covers gills) coordinated with mouth - water pushed from mouth, operculum moves outwards
Reducing pressure in opercular cavity (space under operculum) helping water flow through gills
How do insects transport oxygen?
Insects have open circulatory system where blood and tissue fluid both act as bodily fluid
Insects posses tracheal system which supplies air directly to all respiring tissues
Air enters via a pore in each segment called the spiracle and transported through a series of tubes called trachae which divide into smaller tubes called tracheoles
Ends of tracheoles are open and filled with tracheal fluid - gaseous exchange occurs between the air in the tracheole and the tracheal fluid
What happens when insects are very active?
Demand more oxygen
Tracheal fluid can be withdrawn into the body fluid to increase surface area of tracheole wall exposed to air - more oxygen can be absorbed
How do insects ventilate?
Sections of tracheal system are expanded and have flexible walls which act as air sacs and can be squeezed by the action of flight muscles - repetitive expansion and contraction ventilate the tracheal system
Movements of wings alter volume of thorax
Locusts can alter volume of abdomen - as abdomen expands (contract), spiracles at the front (rear) end of the body open and air enters (leave) tracheal system
Why do we need specialised exchange surfaces?
In small organisms, diffusion will supply enough oxygen and nutrients to keep the cells alive and active but multicellular organisms are too large and diffusion is too slow
Multicellular organisms have small SA:V
Metabolic activity - the more energy required, the more the demand for oxygen
