Chapter 7- Exchange surfaces and breathing Flashcards
What are the reasons for specialised exchange services
High metabolic demand
Low surface area to volume ratio
Large diffusion distance
What are the characteristic features of effective exchange surfaces
Increased surface area
Thin layers
Good blood supply
Ventilation to maintain diffusion gradient
What is the benefit of increased surface area
Provides a larger area for exchange and overcomes the problem of larger organisms SA:V ratio
What is the benefit of thin layers
The diffusion distances for substances are short making the process fast and efficient
What is the benefit of good blood supply
Helps maintain a steep concentration gradient by constantly delivering substances to and removing them from the exchange surfaces. Results in faster diffusion
What is the benefit of ventilation to maintain the diffusion gradient
Makes the process more efficient
Give an example of where there is increased surface area
Villi in small intestine or root hair cells
Give an example of thin layers to decreases diffusion distance
Alveoli or villi
Give an example of where there is a good blood supply to create a steeper concentration gradient
Alveoli, gills or villi
Give an example of where there is ventilation to help maintain diffusion gradient
Alveoli or gills
What are the key stages of the human gaseous exchange system
Nasal cavity, trachea, bronchus, bronchioles and alveoli
What are the important features of the nasal cavity
Large surface area with good blood supply to warm air to body temp
Hairy lining which secretes mucus to trap dust and bacteria
Moist surfaces which increase the humidity of the incoming air
After air passes through the nasal cavity where does it next go through
The trachea
What surrounds / supports the trachea
Incomplete rings of strong, flexible cartilage
What is the purpose of the cartilage that supports the trachea
To prevent it from collapsing
Why are the rings incomplete
So that food can move easily down the oesophagus behind the trachea
What is the trachea lined with
Ciliated epithelium
What type of cell is found between and below the epithelium cells
Goblet cells
What is the function of goblet cells
Secrete mucus onto the lining of the trachea
Why is mucus secreted onto the lining of the trachea
To trap dust and microorganisms that escape the nose lining
What is the effect of cigarette smoke on the cilia
Stops cilia beating
How do cilia move the mucus
They beat moving any trapped dirt and microorganisms as well as the mucus to the throat
What does the trachea divide into
The left and right bronchus
Where does the left and right bronchus lead to
The left and right lung
What do the bronchi divide into
Bronchioles
What is the function of the bronchioles
To constrict or dilate, altering the amount of air that is reaching the lungs
What is the main gaseous exchange surface of the body
Alveoli
Describe the structure of an alveolus
Tiny air sac consisting of:
A layer of thin flattened epithelial cells, collagen and elastin fibres
What is the elastic recoil of the lungs
When elastic tissue in the alveoli stretch as air is drawn in and return to original size as it moves out
