Exchange surfaces and Transport in animals Flashcards
NEED FOR EXCHANGE SYSTEM: size
-in very small organisms, such as singled celled organisms, cytoplasm very close to environment in which they live
-diffusion supply enough oxygen and nutrients to keep cells alive
-multicellular organisms may have several layers of cells
-any oxygen or nutrients diffusing in from outside have longer diffusion pathway therefore insufficient
NEED FOR EXCHANGE SYSTEM: surface area to volume ratio
-small organisms have small surface area and small volume -meaning their surface area to volume ratio large and all cells can be supplied with sufficient oxygen
-larger organisms have larger surface area but also larger volume - they have smaller surface area to volume ratio therefore need an exchange system
NEED FOR EXCHANGE SYSTEM: level of activity
-some organisms are more active than others
-metabolic activity uses energy from food and requires energy released from oxygen in aerobic respiration
-cells of an active organism need good supplies of nutrients and oxygen to supply energy for movement
-this needs for energy is increased in those animals such as mammals, that keep themselves warm
Features of a good exchange system
-large surface area to provide more space for molecules to pass though
-thin barrier to reduce diffusion pathway - must be permeable to substances being exchanged
-good blood supply to maintain steep concentration gradient so diffusion can occur rapidly
How is gas exchanged in the lungs
-gases pass by diffusion through thin walls of alveoli
-oxygen passes from air in alveoli to blood in capillaries
-carbon dioxide passes from blood to air in alveoli
-lungs must maintain steep concentration gradient to ensure diffusion continues
-alveoli provide a very large surface area and are lined by thin layer of moisture which evaporates and is lost as we breathe out
-alveoli also produce surfactant that coats internal surface of alveoli to reduce cohesive forces between water molecules as these forces tend to make alveoli collapse
Describe permeability of exchange barrier
-barrier to exchange is comprised of wall of alveolus and wall of blood capillary
-cells and plasma membranes readily allow diffusion of oxygen and carbon dioxide as molecules small and non-polar
Why is exchange barrier thin
-alveolus wall is one cell thick
-capillary wall one cell thick
-both walls consist of squamous cells - flattened and very thin
-capillaries in close contact with alveolus walls
-capillaries so narrow that red blood cells squeezed against capillary wall - reducing rate of flow
Why does exchange have good blood supply
-helps maintain steep concentration gradient
-blood system transport carbon dioxide from tissues to lungs; ensures concentration of CO2 in blood is higher than in air - CO2 diffuses into alveoli
-blood transports oxygen away from lungs - ensures that concentration of O2 in blood kept lower than that in alveoli so oxygen diffuses into blood
What is ventilation
-ventilation ensures that concentration of oxygen in air of alveolus remains higher than that in blood; concentration of carbon dioxide in alveoli remains lower than that in blood - concentration gradient necessary so diffusion maintained
Steps of inspiration
1) diaphragm contracts to move don and become flatter displacing digestive organs down
2) external intercostal muscles contract to raise ribs
3)volume chest cavity increased
4)pressure chest cavity drops below atmospheric pressure
5)air moved into lungs
Steps of expiration
1) diaphragm relaxes and pushed up
2) external intercostal muscles relax and ribs fall
3)volume chest cavity decreased
4) pressure in lungs increases and rises above pressure in atmosphere
5) air is moved out of the lungs
Describe lung tissue
-lungs consist of large numbers of tiny air-filled sacs called alveoli - compromised of squamous epithelium and are surrounded by blood capillaries so diffusion pathway short
-alveolus walls contain elastic fibres that stretch during inspiration but then recoil to help push air out during expiration
What are the requirements of the airways
-trachea, bronchi and bronchioles allow passage of air into lungs in and out again
-be large enough to allow sufficient air to flow without obstruction
-be supported, preventing collapse when air pressure is low during inspiration
-be flexible in order to allow movement
How are airways lined
-airways lined by ciliated epithelium - goblet cells in epithelium release mucus, trapping pathogens
-cilia then move mucus up to top of airway where swallowed
-glandular tissue in loose tissue also produces mucus
Describe structure of trachea and bronchi
-these airways supported by rings of cartilage which prevent collapse during inspiration
-rings of cartilage in trachea are C shaped allowing flexibility and space for food to pass down oesophagus
Describe structure of bronchioles
-larger bronchioles have some cartilage but smaller ones have none
-wall is compromised mostly of smooth muscle and elastic fibres
-smallest bronchioles end in clusters of alveoli
Describe the tissues in bronchus
-goblet cell secretes mucus which increases dust and bacteria
-ciliated epithelium; cilia move mucus along airway
-smooth muscle contracts to constrict airway
-loose tissue containing elastic fibres, glands and blood vessels
-small blood vessels
-cartilage supports airway preventing collapse
Describe smooth and elastic tissue
-smooth muscle contract, constricting airway
-makes lumen of airway narrower, restricting flow of air to and from alveoli - controlling this is important if there are harmful substances in air
-contraction of smooth muscle and control of airflow is not voluntary and may be result of allergic reaction
-once smooth muscle contracted, cannot reverse on its own
-when is contracts it deforms elastic fibres
-as muscle relaxes elastic fibres recoil to original size and shape, dilating airway
How is lung volume measured
-lung volumes can be measured using spirometer
-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 chamber so lid moves down
-during expiration air returns to chamber, raising lid
-movements may be recorded on data logger
-carbon dioxide rich air exhaled is passed through chamber of soda-lime, absorbing carbon dioxide - this allows measurement of oxygen consumption
Precautions when using a spirometer
-subject should be healthy, free from asthma
-soda-lime should be fresh and functioning
-should be no air leaks in apparatus as this gives inaccurate results
-mouthpiece should be sterilised
-water chamber must not be overfilled
-use nose clip
Describe the lung volumes
-vital capacity is maximum volume of air that can be moved by lungs in one breath
-vital capacity is affected by size of person, age and gender and their level of regular exercise
-vital capacity typically 2.5-5dm3 but may rise in trained athletes
-residual volume is volume of air that remains in lungs after forced expiration - approximately 1.5dm3
-tidal volume is volume of air moved in and out with each breath
-usually measured at rest - typically 0.5dm3
How is oxygen uptake measured
-breathing supplies oxygen for respiration and removes carbon dioxide
-as person breaths from spirometer, oxygen absorbed by blood and replaced by carbon dioxide
-carbon dioxide absorbed by soda lime in spirometer so that volume of air in chamber decreased
-this decrease can be observed and measured on spirometer trace
-we can assume volume of carbon dioxide released and absorbed by soda lime equals volume of carbon dioxide absorbed by blood
-therefore measuring gradient of decrease in volume enables us to calculate rate of oxygen uptake
How is breathing rate measured
-breathing rate can also be measured from spirometer trace - simply count number of peaks in a minute
-breathing rate at rest usually 12-14 breaths per minute
-oxygen uptake will depend upon number of factors
-increase oxygen uptake will result from increased breathing rate of deeper breaths
Describe the exchange system of bony fish
-bony fish must exchange gases with water in which they live
-they use gills in order to absorb oxygen dissolved in water and release carbon dioxide in eater
-oxygen concentration typically much lower than air
-most bony fish have 5 pairs gills which are covered by bony plater called operculum
-each gill consist of two rows of gill filaments attached bony arch
-filament are very thin and surface folded into secondary lamellae providing large surface area
-blood capillaries carry deoxygenated blood close to surface of secondary lamellae where exchange takes place
Describe the counter-current flow
-if did not have counter current flow, blood would reach equilibrium
-blood flows along gill arch and out along filaments to secondary lamellae
-blood flows through capillaries in opposite direction to the flow of water over lamellae
-this arrangement creates counter current flow that absorbs maximum amount of oxygen from water via steep concentration gradient
Describe the ventilation in bony fish
-bony fish can keep water flowing over gills by using buccal opercular pump
-the buccal cavity can change volume
-floor of mouth moves downwards drawing water into buccal cavity
-mouth closes and flow raised again pushing water through gills
-movements of operculum are coordinated with movements of buccal cavity - as water pushed through buccal cavity, operculum moves outwards
-this movement reduces pressure in opercular cavity, helping water to flow through gills
Describe the exchange system of insects
-insects do not transport oxygen in blood
-haemolyph not in vessels
-insects have open circulatory system in which the body fluid acts as both blood and tissue fluid
-circulation slow and affected by body movements
-insects possess an air filled tracheal system which supplies air directly to all respiring tissues
-air enters system via pore in each segment called spiracle
-air is transported into body through series of tubes called tracheae - these divide into smaller tubes called tracheoles
-ends of tracheoles are open and filled with fluid called tracheal fluid
-gaseous exchange occurs between air in tracheole and tracheal fluid - some exchange can occur across thin walls of tracheoles
-many insects very active and need good supply oxygen
-when tissues active, tracheal fluid can be withdrawn into body fluid to increase surface area- more oxygen absorbed when insect active
Describe the ventilation in insects
-in many insects, sections of tracheal system are expanded and have flexible walls - these act as air sacs which can be squeezed by action of flight muscles
-repetitive expansion and contraction of these sacs ventilated the tracheal system
-in some insects, movement of wings alter volume of thorax as thorax volume decreases, air in tracheal system is put under pressure and pushed out; when thorax volume increases, pressure inside drops and air pushed into tracheal system
-some insects have developed this ventilation even further
How is ventilation of locusts specialised
-locusts can alter volume of abdomen by specialised breathing
-these are coordinated with opening and closing valves in spiracles
-as abdomen expands, spiracles at front end of body open and air enters tracheal system
-as abdomen reduces in volume, spiracles at rear end of body open and air can leave tracheal system
Why do animals need transport system
-larger animals with complex anatomy will have more than two layers of cells therefore diffusion distance becomes too long and diffusion alone will be too slow to meet requirements:
-supply of oxygen and nutrients for growth and survival
-removal of waste products so they don’t build up to become toxic
Why does size affect transport system
-cells inside large organism are further from its surface - diffusion pathway increased
-diffusion rate is reduced and diffusion too slow to supply all requirements
-also outer layer of cells use up supplies, so less will reach cells deep inside body
How does surface area to volume ration affect transport system
-larger animals have smaller surface area to volume ration
-each gram of tissue has smaller area of body surface for exchange
How does level of metabolic activity affect need for transport system
-animals need energy from food so they can move around
-releasing energy from food by aerobic respiration requires O2
-if animal very active, its cells need good supplies of nutrients and oxygen to supply energy for movement
-animals that keep themselves warm, need even more energy
Features of an effective transport system
-a fluid or medium to carry nutrients, oxygen and waste around body - the blood
-a pump to create pressure that will push the fluid around body - this is heart
-exchange surfaces that enable substances to enter blood and leave it again where needed - this is capillaries
