Module 3 Flashcards
why are specialised exchange surfaces needed/not needed?
- Single celled organisms don’t need them as they have low metabolic activity so low demands for oxygen and CO2 exchange. Mammals use lots of energy on temperature regulation which they maintain independent of the environment.
- Also have high SA:Vol ratio
- Land mammals need water and gas exchange, but the conditions needed for gas exchange like moist lining are ideal for evaporation of water. Systems help minimise water loss.
- They have also developed a waterproof surface to minimis water loss stopping gases diffusing through
features of a good exchange surface:
- Large SA (folding walls and membranes)
- Thin barrier reducing diffusion distance
- Maintenance of diffusion gradient by good supply and removal (blood) so occurs faster
- Ventilation helps maintain gradient in gases eg. Flow of water in fish
- Active transport also used to increase rate
difference between respiration and breathing?
Respiration: a chemical reaction at cellular level
Breathing: exchange of gases in blood. CO2 is very important to remove as a build-up can dissolve in blood and is acidic, affecting pH and enzymes. Intercostal muscles move rib cage in and out during deeper breathing
We breathe so we can respire
Ficks law
rate of diffusion is directly proportional to SA x conc. gradient
/ diffusion distance
what surrounds the lungs and what does this do?
Lungs are surrounded by double membranes called pleural membranes which have fluid in the pleural cavity. This provides lubrication between lungs and rib cage
Nasal cavity features
- Has a large SA with good blood supply warming air to body temp
- Hair lining which secretes mucus to trap dust and bacteria protecting lung tissue from irritation and infection
- moist surfaces which increase humidity of incoming air reducing evaporation from exchange surfaces
trachea features
- tube is supported by incomplete rings of strong, flexible cartilage which prevent it collapsing. They are incomplete so food can move easily down oesophagus behind trachea, and in-between rings flexibility Is retained. Ends of cartilage rings are joined by smooth muscle and elastic fibres
- is lined with ciliated epithelium and goblet cells that trap dust and microorganisms that escaped the nose lining and are wafted back up to the throat to be swallowed and digested.
bronchus features
- in chest cavity trachea splits into left and right bronchus leading to each lung
- when in the lungs the bronchi divide to form many small bronchioles with smooth muscle and elastic fibres on walls. This muscle can contract and relax changing the amount of air entering the lungs, but the smallest bronchioles only have elastic fibres not muscle.
- They are lined with a thin layer of flattened epithelium making gas exchange possible
- Bronchi have full rings of cartilage as wont rub against oesophagus, but bronchioles have none. Smallest bronchioles have no goblet cells or cilia.
alveoli features
• Tiny air sacs which are main gas exchange surface. Walls have flattened epithelium cells, collagen and elastic fibres, helping it stretch as air is drawn in and squeeze air out- elastic recoil makes expiration a passive process.
what cells make the wall of the alveoli and capillary?
- Squamous epithelium cells make the wall of the alveoli
- Endothelial cells make the wall of the capillary
what is the function of the capillary network in lungs?
• is mostly pulmonary capillaries
• Forms a dense network around each alveolus
• Alveolar macrophages (type of phagocytic white blood cell)
digest any foreign particles (dust and pathogen) that have reached
the alveoli
what is the function of the epithelial cells in lungs?
- Squamous epithelial cells
- Type 1 and type 2 pneumocytes
- Type 1 are large and flat that make up most of cell wall
- Type 2 secrete surfactant which has antibacterial properties
connective tissue structure and function:
- Forms a supporting layer beneath the epithelium
- Consists of fine collagen and elastin fibres and fibroblast cells
- Allows stretch and recoil of lung tissue with breathing, preventing alveoli bursting. The recoil also helps expel air.
cartilage structure and function:
• Form a connective tissue composed of cells surrounded by a material consisting of mucopolysaccharides, which are complex polysaccharides containing amino groups.
support preventing collapse
What is surfactant and what does it do?
- A mixture of lipids and proteins which helps reduce surface tension of liquid lining the inner surface of alveoli
- Speeds up transport of gases between the air and liquid lining alveolus
- Kills bacteria
- Helps alveoli remain inflated and they stick together as you exhale
Location and function of structures in respiratory system: Cartilage smooth muscle elastic fibres goblet cells ciliated epithelium
trachea and bronchi
support preventing collapse
bronchioles
contracts to constrict airways to control airflow
bronchioles
as smooth muscle relaxes fibres recoil so airways dilate
trachea and bronchi
secrete mucus to trap particles in air
trachea and bronchi
waft mucus up the throat by synchronised beating
why do insects a need gas exchange system?
• They have a tough exoskeleton which doesn’t allow gas exchange and have no blood pigment to carry oxygen
How is the amount of air entering insects gas exchange system managed?
- Has small openings called spiracles along the thorax and abdomen which allow water and air to leave and also for water to escape. There are a pair of spiracles pre abdomen segment.
- Sphincters can open and close the spiracles, and they are kept closed as much as possible to reduce water loss, especially when inactive so oxygen demand is low and there is little CO2 (this is minimised by fluttering when they open and close v quick)
- In discontinuous gas exchange there are 3 stages: open, closed and fluttering . When the spiracles are closed CO2 diffuses into the bodily fluids and is held in the process buffering.
What happens to air after it enters through the spiracles?
- Tracheae lead away from the spiracles, running into and along the body and are the largest respiratory tubes at 1mm diameter.
- Tracheae are lined with chitin which keeps them open if they get bent or pressed. As its relatively impermeable to gases little gas exchange occurs in the trachea
- Tracheae branch into narrower tracheoles diameter 0.6-0.8 um, which are single elongated cells with no chitin lining, therefore are permeable to gases. As they are very small, they run through tissues and through individual respiring cells allowing gas exchange and provide a large SA.
- The movement of air occurs by diffusion usually, and oxygen dissolves in the moisture of the tracheole walls.
How is the supply of oxygen increased in insects?
What can happen if oxygen demand is too high?
• When there is a high oxygen demand (flying) then lactic acid builds up in the tissues causing water to osmose out of the tracheoles, exposing more SA for gas exchange
• Some larger insects like bees have high energy demands so have other methods of increasing gas exchange:
- Mechanical ventilation of the tracheal system is where muscular pumping of the thorax/abdomen actively pump air into the system, by changing the volume of the body, therefore changing the pressure in the tracheae and tracheoles, drawing air in or forcing it out. When the body expands air is sucked in.
- Collapsible enlarged tracheae or air sacs act as air reservoirs which are inflated or deflated by the contractions of the thorax and abdomen. They help increase the amount of air moved through the gas exchange system.
Why do bony fish need an exchange system?
• Although they don’t have to prevent water loss like insects, they have to overcome the viscosity of water (100x more than air)
• Also the lower oxygen content causing slow diffusion rates
large active fish like cod cannot rely on diffusion alone to reach the inner cells due to their small SA:Vol ratio
scaly outer surface doesn’t allow gas exchange
• It can also be hard to maintain a constant flow of water over the gills when the fish isn’t moving, and this water flow is necessary to keep the gill filaments apart, exposing their large SA.
What are the adaptations of the gills?
- Tips of adjacent gill filaments overlap, increasing the resistance to the flow of water over the gills slowing it down so more time for gas exchange
- filaments/lamellae increase SA
- rakers trap food and absorb it into the blood
- The water moving over the gills and the blood in the (gill filaments- where?) flows in different directions to maintain a steep concentration gradient so that the water always has higher concentration than water?? and a counter current exchange system is set up. Parallel/concurrent systems only extract 50% of oxygen flowing past as they reach equilibrium halfway through compared to 80% with bony fish
Where are the gills found and what are their features?
- They have gills in the gill cavity covered by a protective operculum (bony flap) which helps maintain flow of water over gills.
- The gills have a large SA- lamellae
- good blood supply
- thin layers
- a one-way flow of water across them to reduce the energy used to move the viscous water in and out of respiratory systems like lungs.
What method of ventilation do some primitive fish use and what do bony fish use?
- For some primitive cartilaginous fish like sharks when they stop moving the flow of water stops and the gills can’t be ventilated, as they rely solely on this- ram ventilation.
- Bony fish have another system: the mouth is opened and the floor of the buccal cavity (mouth) is lowered, increasing its volume and decreasing the pressure so that water moves in. Whilst this is happening the opercular valve is shut and the opercular cavity containing gills expands, lowering the pressure below the buccal cavity. The floor of the buccal cavity starts to move up increasing the pressure, so water moves out of it and over the gills.
- When the mouth closes the operculum opens and the sides of the opercular cavity move inwards. This increases pressure in the opercular cavity forcing water out the operculum. The floor of the buccal cavity is steadily moved up, so a steady flow of water is over the gills.