gaseous exchange systems Flashcards
levels of organisation
cells-tissue-organs-organ system-organism
Why do organisms need exchange surfaces ?
Take in essential substances and get rid of waste substances
What has a large surface area in the body ?
alveoli in the respiratory system
villi in small intestine
A short distance required for diffusion
membranes of cells
walls of blood capillaries are one cell thick
the epithelia of alveoli in respiratory and villi in small intestine is one cell thick
What does constant blood flow and ventilated surfaces do ?
Maintains a strong concentration gradient which increases effective gaseous exchange
Structure of respiratory system
lungs enclosed by thorax
protected by 12 pairs of intercostal muscles
muscular diagphram below lungs
Lungs sealed by moitst airtight pleural membranes
How is the trachea adapted for ventilation
Rings of cartilage in walls of trachea help keep it open as air is drawn in. prevents it from collapsing during inhalation
Where does gas exchange occur in the body ?
between alveoli and blood in the capilleries
Capillaries provide a large surface area for gaseous diffusion
Where does gas exchange occur in the body ?
between alveoli and blood in the capilleries
Capillaries provide a large surface area for gaseous diffusion
gas exchange - how it works ?
oxygen diffuses into the bloodstream and carbon dioxide diffuses out of the bloodstream
- Co2 in deoxygenated blood from the pulmonary artery diffuses out
- As you breath in, o2 is diffused into the bloodstream, making it oxygenated carrying it to the pulmonary vein
How are the alveoli adapted for gas exchange ?
- small size which gives it a larger surface area to volume ratio
- number - 700 million alveoli
SHORT DIFFUSION PATH - walls of blood capillaries and alveoli are just one cell thick
What is ventilation ?
the movement of air through the conducting passages between the atmosphere and the lungs.
What is the most important muscle when we inhale ?
The diagphram and then the external intercostal muscles. Breathing is a passive process resulting from pressure changes in the lungs
When we inhale…
Diaphragm contracts, pulling downwards
intercostal muscles contract - moves upwards and outwards
volume of thorax increases - pressure decreases in lungs so air is drawn in
When we exhale…
Diagram relaxes and moves upwards
Intercostal muscles relax - ribs move downwards and outwards
Volume of thorax decreases so pressure in lungs increases and air leaves lungs
