Topic 3: Exchange and Transport: Surfaces Flashcards
Why is diffusion of oxygen and carbon dioxide enough for single-celled organisms?
-The metabolic activity of a single-celled organism is usually slow so the oxygen demands and carbon dioxide production of the cell are relatively low
-The surface area to volume ratio of the organism is large
Why is diffusion of oxygen and carbon dioxide not enough for larger organisms?
Organisms have high metabolic rates as their oxygen demands are high due to the amount of energy they use, and thedistance between the cells where the oxgen is needed and supply of oxygen is too far for effective diffusion.
Also, larger organisms = smaller sa:v = gases cant be exchanged fast enough or in large enough amounts for survival
Features of specialised exchange surfaces
Specialised exchange surface features:
-Increased surface area (eg root hair cells and villi)
-Thin layers (short diffusion paths, eg alveoli)
-Good blood supply (steeper conc gradient = faster diffusion. Good blood supply maintains gradient)
-Ventilation to maintain diffusion gradient (for gases)
Nasal cavity
Nasal cavity
-Large surface area with a good blood supply which warms the air to body temperature
-A hairy lining - secretes mucus to trap dust and bacteria to protect delicate lung tissue
-Moist surfaces - increases humidity of incoming air to reduce evaporation from the exchange surfaces
After passing through the nasal vacity, air entering the lungs is a similar temp and humidity to air already there
Trachea
-Trachea: wide tube supported by incomplete rings of strong flexible cartilage which stops it collapsing (incomplete so food moves easily)
-Lined with ciliated epithelium with goblet cells between epithelial cells
Role of the goblet cells within the cilliated epithelium inside the trachea
Goblet cells secret mucus onto the lining of the trachea to trap dust and microorganisms - cillia beats and move mucus away from lung to be swallowed and digested by throat
Bronchus
Bronchus - in the chest cavity the trachea divides to form left bronchus leading to the left lung, and the right bronchus leading to the right lungs. Similar structure to trachea - contains smaller cartilage
Bronchioles
Bronchioles:
-diameter 1mm or less
-No cartilage rings
-Walls contain smooth muscle - contracts > bronchioles constrict
Muscle relaxes > bronchioles dilate
Dilation and constriction changes amount of air reaching lungs
-Lined with layer of flattened epithelium > some gaseous exchange
Alveoli
Alveoli
-Tiny air sacs - main gas exchange surfaces
-Diamater around 200-300 micrometers
-Consists of a layer of thin flattened epithelial cells along with some collagen and elastic fibres composed of elastin (helps recoiling)
-Large surface area
-Thin layers (single epithelial cell thick)
-Good blood supply (lots of capillaries)
-Good ventilation
Elastic recoil of the lungs
Elastic recoil of the lungs is when the elastic tissues allow the alveoli to stretch as air is drawn in, then they return to their resting size to help squeeze air out
Inner surface of alveoli
Inner surface of alveoli is covered in thin layer of solution made up of water, salts and lung surfactant
Lung surfactant
Lung surfactant prevents the alveoli from collapsing during exhalation
How does air move in and out of the lungs?
Air moves in and out of the lungs as a result of pressure changes in the thorax (chest cavity) brought about by the breathing movements - ventilation
Role of the rib cage
-The rib cage proves a semi-rigid case within which pressure can be lowered with respect to the air outside it.
-Diaphragm - broad sheet of muscle - forms floor of thorax
-Thorax lined by pleural membranes which surround lungs - the space between them (pleural cavity) is filled with thin layer of lubricating fluid so the membranes slide easily over eachother as we breathe
The thorax of the ribcage
-Thorax lined by pleural membranes which surround lungs - the space between them (pleural cavity) is filled with thin layer of lubricating fluid so the membranes slide easily over eachother as we breathe
Inspiration
Inspiration: taking air in/inhalation : energy using process
Process of inhalation/inspiration
Inhalation/inspiration:
-Diaphragm contracts, flattening and lowering
-External intercostal muscles contract to move ribs upwards and outwards
-Volume of thorax increases so pressure in thorax reduces
-Pressure is now lower than atmospheric air pressure so air is drawn through nasal passages, trachea, bronchi and bronchioles into lungs
-Pressure inside and outside chest equalises
Process of expiration (passive process)
-Diaphragm muscles relax so moves into its resting domed shape
-External intercostal muscles relax so ribs move down and inwards udner gravity
-Elastic fibres in alveoli return to normal length
-Effecte of changes decreases volume of the thorax
-Pressure inside thorax greather than atmospheric air pressure to air moves out until it equalises
Forced exhalation
Forcing exhalation uses energy:
-Internal intercostal muscles contract, ribs pull down hard and fast, absominal muscles contract and force diaphragm up to increase pressure in lungs rapidly
How does good blood supply help specialised exchange systems?
Good blood supply > when oxygen diffuses into blood, it’s rapidly removed > maintains steep concentration gradient
Ways that the volume air drawn in and out of the lungs can be measured
Ways of measuring the volume of air drawn in and out of the lungs:
-Peak flow meter
-Vitalographs
-Spirometer
A peak flow meter
Peak flow meter - device that measures the rate at which air can be expelled from lungs - used for people who has asthma - used as an indication of lung function
Vitalographs
Vitolagraphs - sophisticated versions of peak flow meters - patient breathes out as quickly as they can through a mouthpiece and a graph is produced for the amount of air being breathed in and out.
Whats the volume of air called used for vilatographs
Volume of air is called the forced expiratory volume in 1 second
Spirometer
Spirometer used to measure different aspects of lung volume or to investigate breathing patterns
6 components of the lung volume
6 components of lung volume:
-Tidal volume
-Vital capacity
-Inspiratory reserve volume
-Expiratory reserve volume
-Residual volume
-Total lung capacity
Tidal volume
Tidal volume - volume of air that moves into and out of the lungs with each resting breath.
Adults - around 500cm^3 at rest, which uses about 15% of the vital capacity of the lungs
Vital capacity
Vital capacity - volume of air that can be breathe din when the strongest possible exhalation is followed by the deepest possible intake of breath
Inspiratory reserve volume
Inspiratory reserve volume = - maximum volume of air that you can breathe in over and above a normal inhalation
Expiratory reserve volume
Expiratory reserve volume - the extra amount of air that you can force out of your lungs over an dabove the normal tidal volume of air you breathe out
Residual volume
Residual volume - volume of air that is left in your lungs when you have exhaled as hard as possible. This cannot be measured directly.
Total lung capacity
Total lung capacity - sum of the vital capacity and the residual volume
Recordings from a spirometer
Recordings from a spirometer shows the different volumes of air moved in and out of the lungs
Breathing rate
Breathing rate - number of breaths taken per minute
Ventilation rate
Ventilation rate - total volume of air inhaled in one minute
Ventilation rate calculation
Ventilation rate = tidal volume x breathing rate (per minute)
Movements of oxygen and carbon dioxide in relation to alveoli
Alveoli:
-Oxygen diffuses out of alveoli across alveolar epithelium and capillary endothelium in the blood
-Carbon dioxide diffuses into alveoli from blood and is breathed out
Overall movements of oxygen in the lungs
Oxygen moves down trachea > bronchi > bronchioles > into alveoli (all happens down pressure gradient) > diffuses across alveolar epithelium > capillary endothelium into capillary (down diffusion gradient)
Movement of air in relation to pressure
Air always moves from high to low pressure (down pressure gradient)
Why is it important for organisms to have a steep concentration gradient for diffusion?
A steep concentration gradient > fast diffusion - ensures substances are constantly delivered to and removed from the exchange surface
Why does fish have gills?
Fish use gills in order to absorb oxygen dissolved in the water and release carbon dioxide in the water
Bony plate that covers gills
The bony plate that covers gills is called the operculum
Filaments in the gills
Each gill consists of two rows of gill filaments (primary lamallae) attached to a bony arch
Filaments are thin and is folded into secondary lamallae (gill plates)
Where does exchange take place in fish?
Blood capillaries carry deoxygenated blood close to the surface of the secondary lamallae which is where exchange takes place
Countercurrent flow in fish
Blood flow along gill arch and out along filaments to secondary lamallae > blood flows through capillaries in opposite direction to water flow > this arrangement creates a countercurrent flow that absorbs the maximum amount of oxygen from the water
How has insects evolved their exchange systems?
Exchange systems of insects have evolved to deliver the oxygen directly to the cells and to remove the carbon dioxide in the same way
How does gas exchange take place in insects?
In insects, air enters and leaves the system through the spiracles (Water is lost)
Spiracles
Spiracles are small openings along the thorax and abdomen of most insects
How do insects minimise water loss from spiracles?
Spiracles of insects can be opened or closed by sphincters, and they are usually kept closed as much as possible to minimise water loss especially when inactive
Tracheae in insects
Trachae in insects are the largest tubes of the insect respiratory system, up to 1mm in diameter, and they carry air into the body
-Runs both into and along the insects body
What is tracheae lined with in insects?
In insects, their tracheae is lined by spirals of chitin which keep them open if they are bent or pressed
Chitin in insects
Chitin in insects line tubs of the tracheae, they are relatively impermeable to gases and so little gaseous exchange takes place in the trachea.
Tracheoles in insects
Tracheoles are narrow tubes that branch from the tracheae
-Small diameter
-Each tracheole = single, elongated cell with no chitin lining - permeable ot gases
-Vast amount = greater SA
How does air move along the insect?
Air moves along tracheae and tracheoles > oxygen dissolves in moisture on the tracheole walls > diffuses into surrounding cell
Tracheal fluid
Tracheal fluid - end of the tracheoles, limits the penetration of air for diffusion
What happens when oxygen demands build up in insects ie when flying
When oxygen demands are high in the insect, lactic acid builds up in the tissues resulting in water moving out of the tracheoles by osmosis - exposes more surface are for gaseous exchange
Alternative methods of increasing the level of gaseous exchange in insects
Alternative methods of increasing the level of gaseous exchange in insects:
-Mechanical ventilation of the tracheal system
-Collapsible enlarged trachea or air sacs, which act as air resevoirs
How does mechanical ventilation of the tracheal system in insects aid gases exchange?
Mechanical ventilation of the tracheal system: air actively pumped into system by muscular pumping movements of thorax and/or abdomen > movements change volume + pressure of body > air drawn in/out depending on pressure changes
How does collapsible enlarged trachea or air sacs acting as air resevoirs aid gaesous exchange in insects?
Collapsible enlarged trachea or air sacs which act as air resevoirs = used to increase amount of air moved through system > usually inflated/deflated by ventilating movements of thorax and abdomen
Gas exchange in relation to the diffusion gradient
Oxygen moves down concentration gradient from the air into body cells, carbon dioxide moves down concentration gradient from body cells into air
Ventilation by rhythmic abdominal movements
Ventilation by rhythmic abdominal movements further speeds up the exchange of respiratory gases by generating mass movements of air in and out of the tracheal tubes
Respiratory system in fish
-Gills - gas exchange surface in fish
-Composed of gill filaments stacked together
-Gill lamaellae project at right angles from filaments and serve to increase the surface of gills
-Gill lamallae are few cells thick and contain blood capillaries
Respiratory system in fish
-Gills - gas exchange surface in fish
-Composed of gill filaments stacked together
-Gill lamaellae project at right angles from filaments and serve to increase the surface of gills
-Gill lamallae are few cells thick and contain blood capillaries
Gill lamallae in fish
Gill lamallae - rich blood supply and lagre surface area, main site of gaseous exchange in fish
Gill filaments in fish
Gill filaments occur in large stacks (gill plates) and need a flow of water to keep them apart, exposing large surface area needed for gaseous exchange
Afferent blood vessels in fish
Afferent blood vessels in fish brings blood into the system
Bony gill arch in fish
Bony gills arch supports structure of gills
Effective gas exchange in water
Effective gas exchange in water:
-Parallel flow: conc gradient will level out when blood + water both 50% saturated with oxygen
-Diffusion therefore stops when blood is 50% saturated with oxygen
-In the countercurrent system blood will continue absorbing oxygen from water as conc gradient doesn’t level out
How many pairs of gills do fish usually have and what bony plate do they cover?
Fish gills have 5 plates typically, and cover the operculum plate
Structure of the gill
Gill structure: two rows of filaments over a bony arch, thin filaments folded into secondary lamellae
How does the structure of the gill make it efficient for gas exchange?
Gill structure: large surface area, capillaries carry blood close to surface
Countercurrent flow system
Countercurrent flow system: water flows over the lamellae in the opposite direction to blood flow through capillaries
How ventilation occurs in bony fish
Ventilation in bony fish: water drawn into mouth and forced out over gills, increasing gas exchange
How are the circulatory systems of insects different?
Insects circulatory systems are different due to:
-Open circulatory system
-Presence of body fluid which acts as blood and tissues fluid
Overall structure of insects gas exchange system
Overall structure of insects gas exchange system:
-Air enters via spiracles
-Air transported through tracheae and tracheoles
-Tracheal fluid moves around body and causes gas exchange
How does the expansion and contraction of air sacs aid ventilation?
Expansion and contraction of air sacs:
-Sections of tracheal system have flexible walls which contract and expand changing tracheal volume of the thorax
How do wing movements aid ventilation?
Wing movements:
Changes volume of thorax
Air forced in and out of thorax with pressure changes
How have some insects developed ventilation further?
-Specialised breathing systems
-Coordinated opening and closing of pores
Why do organisms need a circulatory system?
Organisms require a circulatory system because all cells need a constant supply of reactants for metabolism (oxygen, glucose)
Why do large organisms need specialised exchanged surfaces?
Large organisms need specialised exchanged surfaces because of their sa:vol, the diffusion distances are too great
This is overcome by having the lungs and digestive system connected to a circulatory system
Tracheal fluid in insects
Tracheal fluid in insects:
-Tracheal fluid provides muscles (when acitve) with oxygen contraining fluid for respiration
-Lowers pressure in tracheoles which draws more air into spiracles when the fluid is drawn out of tracheoles
-Increases surface area available for oxygen to diffuse down into tracheal walls directly
How does oxygen diffuse into fish?
Movement of oxygen diffusion in fish:
1). Mouth opens - expands buccal cavity: vol of cavity increases and pressure decreases - so water moves into buccal cavity
2). Opercular cavity expands (valves shut) - increases volume and decreases pressure - water moves from buccal cavity into opercular cavity across gills down pressure gradient
3). How air moves out = buccal cavity and opercular cavity constricts : both volumes decreases and both pressures decrease - water pushes valves open > leaves opercular cavity to outside down pressure gradient
Waxy exoskeleton of insects
Insects have a waxy exoskeleton to help with protection and water retention - but due to this gaseous exchange is difficult and so they have the specialised tracheal system
How does larger insects ventilate their tracheal system?
Larger insects ventilate their tracheal system by:
-Air sacs in the tracheal system can be squeezed by flight muscles to push air in + out
-Flight muscles can alter volume of insect thorax to ventilate tracheal system
Insects specialised breathing mechanisms for larger insects
-Abdomen expands - closes spiracles at back of body, opening spiracles at front > O2 enters
-Abdomen contracts: opens up back spiracles, closes front spiracles > CO2 leaves
Lung dissection process
Lung dissection process:
-Sterilise apparatus with ethanol, ensure tools are sharp for clean cuts so structures can be easily cut open
-Open trachea by cutting down gasp in cartilage
-Cut open bronchi and feel tissue (should be spongy)
- Disinfect afterwards
Similarity + difference between trachea of insects + trachea of mammals
Similarity = both held open by rigid material
Difference = lined with chitin in insects, lined with cartilage in mammals
Why is chitin considered a polymer?
Chitin is composed of monomers so that makes it a polymer
Alveolar epithelium
Alveolar epithelium = made up of a single layer of epithelial cells that line the walls of the alveoli = provides short diffusion distance from alvoeli to the capillaries which maximises the rate of gas exchange
Why do insects experience high levels of water loss?
Insects experience high levels of water loss because the walls of the tracheoles are moist and the end of the tracheoles contain tracheal fluid, which means that water vapour can diffuse out of an insect via the spiracles
How do insects reduce water loss?
Insects reduce water loss with having their spiracles be surrounded by a muscular sphincter, which means spiracles can close to prevent water loss, eg when oxygen requirements are low
How have insects have evolved to increase the rate of gas exchange?
-Insects can contract muscles to change the volume of the thorax and abdomen - causes pressure changes in the tracheal systems - controls mass transport of air
-In some insects, the tracheae contain expanded sections called air sacs - air sacs squeezed by pressure changes by changes in volume of thorax - so air moves into tracheoles from the air sacs
