exchange surfaces + breathing Flashcards
Need for exchange systems
- all living cells require a nutrient and oxygen supply
- they also need to be able to remove waste products
in unicellular organisms, this can take place over the surface of the body by diffusion
in multicellular organisms, an exchange system is needed because of…
- size
- surface area : volume ratio ( SA/V)
- metabolic activity
Multicellular organisms
- longer diffusion path
diffusion alone is too slow, innermost cells would not be reached - small SA : V
not all cells would be reached by diffusion alone - high metabolic activity
demand for oxygen for more aerobic respiration is very high, oxygen needs to be transported efficiently and quickly
Unicellular organisms
- short diffusion path
diffusion supplies sufficient oxygen and nutrients - large SA : V
surface area is large enough to supply al cells with sufficient oxygen - low metabolic activity
lower demand for oxygen
Features of GOOD exchange surface
- large surface area
provides space for molecules to pass through
e.g. root hair cells - thin barrier/layer
shorter diffusion path/ distance
e.g. alveoli have a cell membrane which is 1 cell thick and permeable - rich blood supply
maintains a concentration gradient so diffusion can occur quickly
e.g. gills of fish, alveoli
Mammalian gas exchange
Cartilage
- strong flexible cartilage rings support the trachea and bronchi, preventing the collapse of these structures
- rings are C shaped, increasing flexibility for food to pass down the oesophagus
Mammalian gas exchange
Ciliated epithelium
- line airways
- waft mucous and dust away from the lungs
Mammalian gas exchange
Goblet cells
- line airways
- produce and secrete mucous which traps pathogens and particles
Mammalian gas exchange
Smooth muscle
- makeup walls of bronchioles, bronchi, trachea
- control airflow to the alveoli by constricting/ relaxing passageways
- constricts the lumen also to prevent harmful substances from reaching the alveoli
Mammalian gas exchange
Elastic fibres
- makeup walls of bronchioles, bronchi, trachea
- elongate the smooth muscle
- elastic recoil (fibres) = squeeze air out in expiration
- elastic stretch = draw in air in inspiration
Mammalian gas exchange
Bronchi, bronchioles, trachea
- passageway for air
Mammalian gas exchange
Alveoli
- tiny folds of lung epithelium which increase SA
- tiny air sacs
- MAIN gas exchange surface in mammals
oxygen into blood out of alveoli, carbon dioxide out of blood into alveoli
Adaptations of alveoli
- large SA
large SA: V ratio, efficient diffusion - thin layers (1 cell thick)
short diffusion path - rich blood supply
maintains steep concentration gradient for efficient diffusion - good ventilation
maintains concentration gradient, keeps gases diffusing
Ventilation
ensures the concentration of oxygen is higher in the alveoli than in the blood
Rib cage
provides semi-rigid case
Diaphragm
a domed sheet of muscle that forms the floor of the thorax
Internal intercostal muscles
External intercostal muscles
found between ribs and facilitate - internal - exhalation, external - inhalation
Inspiration
- energy-using process
- diaphragm contracts, flattens and lowers
- external muscles contract
- ribs move up and out
- volume in thorax increases
- pressure in thorax decreases
= air drawn into the lungs
Expiration
- passive process
- diaphragm relaxes, move up and rests
- internal muscles relax
- ribs move down and in
- volume in thorax decreases
- pressure in thorax increases
= air pushed out of lungs
Spirometer; vital capacity
- max air volume that can be exchanged between max inspiration and max expiration
- affected by size, age and gender
Spirometer; tidal volume
- volume of air inhaled or exhaled at each breath at rest
- affected by activity, pregnancy and smoking
Spirometer; oxygen uptake
- volume of oxygen absorbed by lungs in 1 min
- affected by the depth of breath and breathing rate
Spirometer; breathing rate
- no. of breaths per min
Insect gas exchange
insects perform gas exchange with an air filled tracheal system
effective, the organism is small
- air enters via spiracles
- air is transported into the body through tracheae
- air passed to tracheoles, filled with tracheal fluid, gas exchange occurs between air and tracheal fluid
Chitin
- mechanical support
- impermeable layer
Increasing gas exchange in insects
- mechanical ventilation
air actively pumped into system - air sacs
increase volume of air moved through system
Fish gas exchange process
- mouth of fish opens (operculum is closed)
- buccal cavity floor is lowered
- increase in volume in the mouth, decrease in pressure
- water enters the mouth of the fish - down a concentration gradient
- opercular cavity expands
- buccal cavity floor is raised
- pressure increases, is higher than opercular cavity
- water moves into the buccal cavity
- mouth closed
- operculum opens
- sides of opercular cavity move inwards, increasing pressure
- water forced out over gills
Gills
gill filament - absorbs oxygen and rids of carbon dioxide
- lamellae - increase SA
- rich blood supply - maintains a concentration gradient
Countercurrent system
blood flows in opposite direction to the water
more oxygen is absorbed into the blood as it moves along
always a concentration gradient as the volume of oxygen in water is always higher than the volume of oxygen in the blood
