3.1.1 EXCHANGE AND TRANSPORT Flashcards
Why do multicellular organisms require a specialised exchange surface?
Whilst both single celled eg amoeba and multicellular organisms eg Dolphin both need glucose and oxygen for cellular respiration and produce waste carbon dioxide unicellular organisms can rely on diffusion alone as there surface area to volume ratio is large meaning there is less disparity and meaning diffusion soon suffice as well as a lower metabolic rate meaning oxygen intake demand and co2 waste demands are low
Surface area and volume of a sphere
SA: 4pir2
V: 4/3pir3
Surface area
Length x width x number of sides
Volume
Length x width x height
What are 4 features which all effective exchange surface have in common inc examples
- increased surface area
Increases rate
Eg root hair cell / many alveoli in lungs - Thin layers
Decreases diffusion distance
Eg alveoli one cell thick - good blood supply to maintain a steep concentration gradient
- ventilation to maintain a steep diffusion gradient
Eg blood supply and water supply in gills and blood supply and ventilation in alveolus
The mammalian gaseous exchange system
What is the conflicting need for land animals and why
Gas exchange and water as gas exchange surfaces are moist so 02 dissolves in water before diffusing into the body tissues
How have mammals managed this challenge
Evolved complex systems allowing efficient GE minimising the ammount of water lost from the body
Components of human ge system
- nasal cavity
- trachea
- bronchus
- bronchioles
- alveoli
How is the nasal cavity adapted for Gas exchange
Increased surface area with good blood supply which warms the air to body temp
Hairy lining secretes mucus to trap dust and bacteria protecting delicate lung tissue from irritation and infection
Moist surfaces increase humidity of incoming air Rudy ing evaporation from the exchange surfaces
After passing bc air entering lungs is a similar temperature and humidity to air already there
How is the trachea adapted to Gad exchange
Main airway carrying clean, warm, moist air nose > chest
Wide tube supported by incomplete c shaped rings of strong, flexible cartilage which stop trachea from collapse and allow food to move easily down the oesophagus behind the Trachea
Lined with ciliated epithelium with goblet cells between and below Goblet cells secrete mucus onto lining of trachea to trap dust and microorganisms
Cilia waft mucus, trapped dust, microorganisms away from the lungs
Most that goes into throat is swallowed and dissolved
Cigarette smoke can stop cillia from beating
Elastic fibres
Smooth muscle
How is bronchus for ge
In chest cavity trachea divided L/R Bronchus (pl Bronchi) on his correlating L/R lung similar in structure to trachea with supporting rings of cartilage but smaller in pieces
Smooth muscle
Elastic fibres
Cilliated epithelium
How are bronchioles afapted for ge
Smaller branch of bronchus
D = >1mm
Walls contain smooth muscle which contracts to construct the airway by reducing the diameter restriction volume of harmful chemicals
Lined with thin layer of flattened squanamous epithelium making ge possible
With elastic fibres to alooow recoil to og shape, expulsion of air and preventing the lungs from bursting
How is an alveolus adapted for ge
- tiny air sac
- main ge surfaces
- unique to mamillan lungs
- d 200-300 micrometers
- squanamous epithelial cells
- collagen
- elastic fibres
- smooth muscle
- sa/ blood supply/ ventilation/ thin layers
- inner surface covered in thin layer of solution of h20 slats and lung surfactant making it possible for the alveoli to remain inflated, 02 dissolved in the water before diffusing into the blood h20 can also evaporate into air in alveoli sec adaptation of human ge is to reduce this loss of water
Pleural membrane / cavity
Between king and chest Prevents lungs rubbing against rib cage during inhilation includes 2 thin layers of tissue that protect and cushion the lungs
Inner layer Visceral pleura wraps around lungs and is stuck so tightly to the lungs that it cannot be peeled off
Outer layer Parietal pleura lines the inside of the chest wall the very think space between is pleural cavity a liquid called pleural fluid lubricates so that 2 layers of tissue can slide against each other and adheres the outer walls of the lungs to the thoracic cavity by cohesion so lungs can expand within the chest while breathing
