Flashcards in 4. Lungs Deck (28):
The volume of carbon dioxide which must be taken in and then removed from the body is large because:
They are relatively large organisms with a large volume of living cells
They maintain a high body temperature and therefore have high metabolic and respiratory rates
List the parts of the human gas exchange system
Lungs are located inside the body because...
Air is not dense enough to support and protect these delicate structures
They would loose a great deal of water and dry out
The lungs are supported and protected by a bony box called the...
What is the structure and function of lungs?
They are a pair of lobed structures made up of a series of highly branched tubules called bronchioles which end in tiny air sacs called alveoli
What is the structure and function of the trachea?
-flexible airway that is supported by rings of cartilage.
-The cartilage prevents the trachea collapsing as the air pressure inside falls when breathing in.
-The tracheal walls are made up of muscle, lined with ciliated epithelium and goblet cells (produces music which traps dirt which goes down the Oesophagus into the stomach).
What is the structure and function of the bronchi?
Two divisions of the trachea. They have the same structure as the trachea but the amount of cartilage is reduced as the bronchi get smaller.
What is the structure and function of the bronchioles?
They are a series of branching subdivisions of the bronchi. Their walls are made of muscle lined with epithelial cells. This muscle allows them to constrict so that they can control the flow of air in and out of the alveoli.
What is the structure and function of the alveoli?
They are minute air sacs at the end of the bronchioles. They contain some collagen and elastic fibres and they are lined with epithelium. The elastic fibres allow the alveoli to stretch as they fill with air when breathing in. They spring back during breathing out to expel carbon dioxide rich air. The alveolar membrane is the gas-exchange surface.
To maintain diffusion of gases across the alveolar epithelium...
Air must constantly be moved in and out of the lungs.
What is breathing also know as?
What is it called when atmospheric pressure is GREATER than the pressure inside the lungs?
Inspiration (inhalation) (air is forced into the alveoli)
What is it called when pressure inside the lungs is GREATER than the atmospheric pressure?
The pressure changes in the lungs are bought about by two different sets of muscles.
The diaphragm and the intercostal muscles
What is the diaphragm?
A sheet of muscle which separates the thorax from the abdomen.
What are the two different types of intercostal muscles?
The internal intercostal muscles - whose contraction leads to expiration
The external intercostal muscles - whose contraction leads to inspiration
What are the 5 steps in inspiration?
-external muscles contract, internal muscles relax
-the ribs are pulled upwards and outwards increasing thorax volume
-the diaphragm muscles contract causing it to flatten out - increasing volume
- increased volume of thorax = reduced pressure in lungs
-atmospheric pressure is now greater than pulmonary pressure and air is forced into the lungs
What are the 5 steps in inspiration?
-Internal muscles contract, external muscles relax
-the ribs move downwards and inwards decreasing thorax volume
-the diaphragm muscles relax causing it to return to its domed position - decreasing volume
- decreased volume of thorax = increased pressure in lungs
-pulmonary pressure is now greater than atmospheric pressure and air is forced out
Is inspiration an active process or a passive process?
Is expiration an active process or a passive process?
The various muscles for ventilation do not play a part unless...
A person experiences more strenuous conditions e.g excersize. In normal quiet breathing the recoil of the elastic lungs is the main cause of air being forced out.
What is pulmonary ventilation?
The total volume of air that is moved into the lungs during one minute.
To calculate pulmonary ventilation multiply...
Tidal volume (volume of air taken in at each breath when the body is at rest) (normally about 0.5 dm cubed) by ventilation (number of breaths taken in one minute) (12-20 breaths in healthy adult)
Pulmonary ventilation is measured in...
Exchange surfaces have the following characteristics to enable efficient transfer of materials:
- A large surface to volume ratio - speed up rate of exchange
- Very thin - to keep diffusion pathway short
- Partially permeable - allowing selected materials to diffuse easily
- movement of environmental medium e.g air to maintain a diffusion gradient
- movement of the internal medium e.g blood to maintain a diffusion gradient
The pulmonary capillaries around each alveolus have walls that are only...
One cell thick
Diffusion of gases between the alveoli and the blood will be very rapid because...
- red blood cells are slowed as they pass through pulmonary capillaries allowing more time for diffusion
- the distance between the alveolar air and red blood cells is reduced a the red blood cell is flattened against the capillary wall
- the walls of the alveoli and capillaries are very thin so there is a short diffusion pathway
- alveoli and pulmonary arteries have a large surface area
- ventilation is taking place constantly - maintains a concentration gradient
- blood flow maintains a concentration gradient