3.1 - Exchange surfaces and breathing Flashcards
larger organisms SA:V…
smaller
why do larger organisms need specialised exchange substances?
- diffusion through the relatively small surface is not efficient enough to supply the large volume
- diffusion pathway too long
- rate too slow
why can expiration be passive
- DOESNT INVOLVE MUSCLE CONTRACTION
- NO ENERGY REQUIRED
passage of air
- nose
- trachea
- bronchus
- bronchioles
- alveoli
cartilage in trachea
c - shaped ring
bronchi are … compared to trachea
narrower
bronchi cartilage
irregular
inner lining of trachea and bronchi
- ciliated epithelium
- goblet cells
inside surface of cartilage has
smooth muscle + elastice fibres (and blood vessels)
cartilage job
- supports trachea and bronchi
- prevents tubes from collapsing when pressure drops during inspiration
ciliated epithelium job
- in bronchi, bronchioles and trachea
- moves mucus up tubes , towards the throat to be coughed out, to prevent reaching lungs and infection
goblet cells
- cells in trachea, bronchus, bronchioles
- secrete mucus to trap dust and pathogens
during inspiration
- EXTERNAL intercostal muscles contract, INTERNAL relax
- ribcage moves up and out
- diaphragm contracts, flattens, and moves down
- vol in THORAX increases, pressure decreases
- Pressure gradient created between lungs and atmospheric, so air drawn in
during expiration
- EXTERNAL intercostal muscles realx, INTERNAL contract IF FORCEDD EXPIRATION
- ribcage lowers and in
- diaphragm relaxes and rises upwards
- volume in thorax decreases, pressure increases
- air forced OUT of lungs
features of efficient gas exchange surface
- large surface area (eg root hair cells)
- thin / short diffusion pathway (alveoli)
- steep concentration gradient (blood supply)
trachea
- wide tube with c shaped cartilage to SUPPORT and keep air passage open during pressure changes
- lines by ciliated epithelium cells which move mucus (secreted by goblet cells) to the throat to be SWALLOWED , preventing lung infections
alveoli are lined with
squamous epithelium cells
why do single celled organisms not need systems
- substances can enter efficiently as distance to travel is short
- ## RATE FAST
rib cage purpose
protects lungs
where does gas exchange ACTUALLY occur
alveoli
why do fish need a specialised exchange surface?
- small SA:V
- impermeable membrane, gases cant diffuse through skin
ventilation in fish
- fish opens mouth by lowering floor of BUCCAL CAVITY. volume increases, pressure decreases, water flows in across pressure gradient
- operculum valve is shut,+BUCCAL CAVITY RAISED: opercular cavity expands. volume increases, pressure decreases
- water forced from buccal cavity OVER the gills into the opercular cavity due to pressure gradient
- BC and OC constrict- vol decreases, pressure increases, forces opercular valves open, water rushes out of valves across pressure gradient
operculum
- acts as a valve and pump for water (lets it in and out)
no. of pairs of gills in bony fish
4
gills in bony fish
- 4 pairs
- each supported by an arch, which have projections called gill filaments
- on the gill filaments are the lamellae
blood and water flow across lamellae
COUNTER CURRENT (opposite direction)
why cant fish survive long out of water?
- gill filaments held apart by water flow
- stick together without water
do insects have a transport system
NO
result of no transport system in insects
oxygen needs to directly be transported to respiring tissues
insect v mammals respiratory system (2)
- insects have a direct connection to environment
- mammals are more complex
spiracles
- opening to the tracheal system on the surface of an insect’s body
- where the gases flow in and out
- open (when active to bring in O2) and close (when resting to minimise H2O loss) to regulate flow of air
insects exoskeleton
- protects them from environment
- prevents water loss
- TOO THICK TO ALLOW DIFFUSION FOR GAS EXCHANGE
mechanical ventilation in insects
pumping the abdomen
need for exchanging substances
- remove waste so they dont build up and become toxic
- supply of oxygen and nutrients to survive
features of an efficient exchange surface
- Increased SA:V (projections/folded membranes)
- Short diffusion distance (eg alveoli one cell thick)
- Steep concnetration gradient (good blood supply/ventilation)
factors affecting the need for a specialised exhcnage system
- metabolic activity
- sa:v
- single/multicelled
ventilation defintion (human)
refreshing of air in the lungs, so theres a higher O2 conc and lower CO2 conc than in the blood
where does gas exchange actually take place in humans
alveoli
passage of oxygen (alveoli)
diffuses from alveoli to blood in capillaries
pasage of CO2 (alveoli)
diffuses from blood in capillaries to alveoli, to lungs to be exhaled
alveoli: large SA
- very small
- but there are loads of them
surfactant
lines the internal surface of the alveoli to prevent the cohesion between water, so stops them from collapsing. maintains large SA
alveoli: short diffusion pathway
- wall is one cell thick, so is that of capillary: TOTAL PATHWAY ONLY 2 CELLS THICK
- both made of squamous epithelial cell (flattened)
- capillaries very close to alveoli
- capillaries v narrow, RBCs squeeze through. closer to alveoli and reduces rate of flow
alveoli: concentration gradient
- surrounded by network of capillaries
- capillaries transport O2 away from the lungs to body cells to be respired. therefore conc O2 in lungs always higher than blood so it will diffuse
- blood transports co2 from tissues to lungs. conc co2 always higher in blood than lungs so co2 diffuses to alveoli to be exhaled
when do internal ICM contract
forced expiration eg exercise, sneezing, coughing. gets air out more forcedully
alveolus wall
- squamous epithelial cell
- contains elastic fibres that STRETCH during inspiration (increaseSA)v
- and recoil to help push air out during expiration
why is cartilage c shaped not full in trachea
allows flexibility and space for food to pass down oesophagus
walls of bronchioles
big ones have cartilage
- smooth muscle and elastic fibres
glandular tissue
- in loose tissue
- prdocues mucus
smooth muscle and elastic fibres together airways
- smooth muscle contracts to contstrict airway, narrowing the lumen
- important if there are harmful substances in the air. (involuntary eg allergic reaction)
- smooth muscle cannot reverse this solo, elastic fibres stretch and recoil to redilate the airway
site of gas exchange in fish
- gills
how are the gills good exchange surfaces
- MANY LAMELLA = large SA
- secondary lamellae on main lamellae = large SA
- SHORT DISTANCE between blood and water: lamellae and filmanets contain a capillary network
- CG: countercurrent flow
countercurrent flow reason?
- water has a loewr conc of o2 compared to air
- fish need to maintain a steep cg across all lamellae
how does ccf work
- water flows over gill lamella in the OPPOSITE Direction to the flow of blood in the capllaries
- never reach o2 equilibrium, steep diffusion cg maintained across all lamellae. max o2 moves from water into blood
insect tracheal system
- air enters through spiracles
- travels along tracheae. lined with CHITIN for support, and impermeable so prevents gas exchange
- branches off into tracheoles (elongated cells without chitin so have permeable walls) which contain tracheal fluid
- O2 moves down CG from air to cells
- CO2 moves against CG from cells to spiracles
insect very active what happens?
- tracheal fluid limits how much O2 can be diffused
- when very active, insufficient O2, so muscle cells anaerobically respire -> lactic acid, builds up in cells, lowering their water potential
- tracheal fluid moves out of tracheols down concentration gradient
- more SA of tracheole wall exposed to air
- more o2 absorbed
4 MARKS SMOOTH MUSCLE
- contracts, reduces diameter of lumen of bronchi and bronchioles
- harder to inhale and exhale as more resistance to air flow
- more air remains in the lungs
- so increased breathing rate
purpose of squamous
provide a short diffusion distance, as are flat
6 MARKS ALVEOLI ADAPTATION
- wall is one cell thick = short diffusion pathway
- squamous walls = short diffusion pathway
- ELASTIC= can recoil and expel air
- large number = increased surface area
- small size = large SA:V
- Surfactant prevents collapse to maintain surface area
3 ways airway diameter can be reduced
- smooth muscle contracts
- inflamation
- extra mucus secreted
how does nasal cavity increase efficinecy of gas exhcange (2)
- large SA and good blood supply. warms air
- mucus secreting cells trap dust and microbes
how does trachea increase efficinecy of gas exhcange (2)
- c chaped rings of cartilage prevent collapse, allowing gases in and out
- ciliated epithelial cells and goblect cells secrete mucus, trap dust and microbes and WAFT TOWARDS stomach
how do bronchi/bronchioles increase efficinecy of gas exhcange (2)
- smooth muscle. allows air to move in and out to maintain high concentration gradient
why might something need a less developed exchange system? (3)
- smaller, larger SA:V
- shorter diffusion pathway
- less metabolically active, lower need for O2
- no hard exoskeleton so oxygen can dfifuse throug outer membrane
insects thoraic and abdominal movement
-moving wings alters volume of thorax. vol decreases, pressure increases, air pushed out and vice versa
- some (eg locusts) : abdomen expands, spiracles at the front open and air enters. abdomen reduces in volume, spiraceles at the rear end open and air leaves
purpose tracheal fluid
prevent dehydration
how can you increase ventilation in tracheal system
- MECHANICAL VENTILATION: muscular pumping of thorax, changing volume and pressure
- collapsible enlarged tracheae (Air sacs). can collapse to release air containing oxygem
do bronchioles have goblet cells?
no
describe forced expiration
- active
- required energy
- internal ICSM contract
- ribcage pulled down hard
- abdmonial muscles contract forcing diaphragm up
passage of air in insects
- enters spiracles
- travels down trachaea
- OXYGEN dissolves in liquid at tracheoles
