Excgange Surfaces - Module 3 Flashcards
Why is diffusion alone sufficient in supplying oxygen for single cell organisms
- Low metabolic activity meaning low oxygen demands and low carbon dioxide production.
- The SA:V ratio is large
Why isn’t diffusion sufficient in supplying oxygen to larger organisms? [3]
- Low SA:V ratio
- Higher metabolic activity requiring lots of oxygen and producing lots of carbon dioxide
- The distance between the cells that require oxygen and the oxygen supply is too far for diffusion to be effective
Equation for volume of a sphere
4/3 x pi x r3
What are the 4 characteristics of an effective exchange system?
- Increased surface area
Provides area needed to overcome limitation of SA:V ratio - Thin layers
This shortens diffusion distance making the process faster - Good blood supply
This maintains a steep concentration gradient allowing faster diffusion to occur - Ventilation to maintain diffusion gradient (for gasses)
How have mammals developed an exchange system allowing them to maximise oxygen intake but minimise water loss?
As gaseous exchange surfaces are moist, oxygen will dissolve in water before diffusing into bodily tissues
Why do mammals have a high metabolic rate?
- Active
- Need to maintain body temperature
Do mammals have a large or small SA:V ratio?
SMALL - because mammals are big organisms
What are the key features of the Nasal Cavity in mammalian exchange system? [4]
- Large surface area
- Good blood supply - which warms are to body temperature
- Hairy lining that secretes mucus to trap dust and bacteria protecting from infection
- Moist surfaces increasing humidity of incoming air reducing evaporation from exchange surfaces
What is the trachea & its structure and what are some key features?
The trachea is the main airway carrying air from the nose into the chest
It is made of INCOMPLETE rings of strong flexible cartilage preventing collapse, the rings are incomplete to allow food to easily pass through the oesophagus behind
- Lined with ciliated epithelium beat and move mucus away away from lungs
- Goblet cells that secrete mucus to trap dust and microorganisms
What impact does cigarette smoke have on cilia?
It stops cilia from beating and therefore stops mucus being moved away from the lungs
What is the structure and function of the bronchus?
It is two tubes leading from the trachea to the left and right lung
Have the same structure as trachea but are smaller (incomplete rings of strong cartilage)
What is the structure and function of the bronchioles? [4]
The bronchioles divide from the bronchi in each lung
They have smooth muscle in the walls
- will constrict when muscle contracts and dilate when muscle relaxes
Lined with a thin layer of flattened epithelium allowing for some gas exchange
What is the structure and function of the alveoli? [3]
The alveoli are tiny air sacs which are the main exchange surface in the body
Consist of:
1. Thin layer of flattened epithelial cells
2. Collagen and elastic fibres
The elastin fibres allow allow the alveoli to STRETCH as air enters and return to their original size to squeeze air out of the alveoli - this is known as ELASTIC RECOIL of the lungs
What are the main adaptations of the alveoli for effective gaseous exchange? [4]
- Large surface area
- Thin layers
Only a single epithelial cell thick so that diffusion distance is short - Good blood supply - surrounded by capillaries
A steep concentration gradient is maintained for both carbon dioxide and oxygen between blood and alveoli - Good ventilation
Breathing moves air in and out of the alveoli helping maintain steep diffusion gradient between blood and air in lungs
What is the inner surface of the alveoli covered in?
WATER, SALTS AND LUNG SURFACTANT
The surfactant allows the alveoli to remain inflated
What is ventilation?
Movement of air in and our of the lungs as a result of pressure changes in the thorax brought about by breathing movements
What is the structure and lay out of the thorax?
The ribcage surrounds the lungs
The diaphragm is a boned sheet of muscle forming the floor or the thorax
Internal and external intercostal muscles are found in between the ribs
Detail the steps of inspiration
- Diaphragm contracts, flattens and lowers
- External intercostal muscles contract
- Ribs move up and out
- Volume of thorax increases reducing pressure
As pressure is lower than that of the atmosphere air is drawn in to equalise pressure
Detail the steps of expiration
- Diaphragm relaxes
- External intercostal muscles relax
- Ribs move down and in
- Volume in thorax decreases, increasing the pressure
Increased pressure in the thorax is greater than that of the atmospheric pressure so air moves out of the lungs until pressure is equalised
Although exhalation is usually passive, how can it be active?
By exhaling forcibly using energy
The internal intercostal muscles will contract pulling the ribs down hard and fast this forces the diaphragm up and therefore increases pressure in lungs
What does amount of gaseous exchange depend on? [2]
- Size
- Level of activity
What are the 3 ways we measure lung capacity?
- Peak flow meter
This measure the rate at which air can be expelled from the lungs - Spirometers
- Vitalographs
What is tidal volume?
Volume of air that moves in and out the lungs with each resting breath
What is vital capacity?
The volume of air breathed out on the strongest exhalation followed by the deepest breathe in
What is Residual volume
Volume of air in lungs followed hardest exhale
What is inspiration and expiratory reserve volume
The maximum air that can be breathed in or the extra air that can be forced out on a breathe out
What is total lung capacity?
Total lung capacity = vital capacity + residual volume
What is breathing rate?
Number of breathes taken per minute
What is ventilation rate?
Total volume of air inhaled in one minute
What is the calculation for ventilation rate?
Ventilation rate = tidal volume x breathing rate
