Chapter 7 Exchange surfaces Flashcards
Why can single celled cells survive with solely diffusion?
The metabolic activity of the cell is low, oxygen and carbon dioxide demands are low
The SA:V is very large, small diffusion distances
Therefore the rate of diffusion is large enough to cope with the cells demands
Why do larger organisms need specialised exchange surfaces?
Larger organisms are made from tissues, organs, organ systems
Higher metabolic demand, more O2 CO2
Large diffusion distances between uppermost cells and those towards the centre
Low surface area to volume ratio
Therefore sole rate of diffusion too low to meet metabolic demands
What is the calculation of surface area to volume ratio?
SA / Volume
What are features of effective exchange surfaces, with examples?
Large Surface Area: Overcome limitation of low SA:V, greater points of diffusion e.g root hair cells
Thin Layers: Decreases diffusion distances e.g alveoli
Good Blood Supply: Steeper concentration gradient, greater rate of diffusion e.g fish
Ventilation: Maintain steep concentration gradients, as above e.g alveoli
What is the order of air entering the body?
Nasal Cavity, Trachea, Bronchus, Bronchioles, Alveoli
How is the nasal cavity adapted to its function?
Large Surface Area, with a good blood supply: warms the air to body temperature
Hairy Lining: Secretes mucus to trap dirt and bacteria, protect lung tissue
Moist: Increases humidity of incoming air, reducing evaporation from exchange surfaces
Describe the structure of the trachea and explain how it relates to its function
Main airway carrying clean air from nose into the
chest
Wide tube supported by incomplete rings of strong, flexible cartilage
Incomplete rings so food can move down the oesophagus behind the trachea
Lined with ciliated epithelium and goblet cells to secrete mucus and move mucus away from lungs eng to throat
Describe the structure of the bronchus
Similar to trachea with same rings of cartilage but smaller
Divides into left and right for each lung
Describe the structure of the bronchioles
Formed by bronchi
No cartilage rings, contain smooth muscle
When muscles contract, constriction of bronchioles, changing amount of air to lungs
Lined with thin layers of flattened epithelium for some gas exchange
Describe the structure of the alveoli
Tiny air sacs, consisting of thin, flattened epithelium cells, with some collagen and elastic fibres
Elastic tissues allow alveoli to stretch, and return to original size helping to squeeze air out= elastic recoil
What are the main adaptations of the alveoli?
Large Surface Area
Thin Layers, one epithelial cell thick
Good blood supply and ventilation
Moist as covered in water, salts and lung surfactant
(also trying to reduce water loss)
Lots of them, to increase SA
Made of squamous epithelium, to reduce diffusion distances
What is lung surfactant?
A complex of proteins and phospholipids which allows alveoli to remain inflated
Define ventilation
The movement of air
How does the ribcage help ventilation?
Provides a semi-rigid case within which pressure can be lowered with respect to the air around it
What are the types of intercostal muscle and where can they be found?
Internal intercostal- towards the inside
External intercostal- towards the outside
