• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

The Structure of Alveoli and their role in Gas Exchange including the role and function of Surfactants.

Extracts from this document...

Introduction

The Structure of Alveoli and their role in Gas Exchange including the role and function of Surfactants Introduction Alveoli are found within the lungs. The trachea splits into 2 bronchi, which in turn split into multiple bronchioles. These in turn branch into finer and finer tubes, ending with the alveolar ducts, which terminate in alveolar sacs which are surrounded by clusters of alveoli. The alveolar wall is composed of two types of cell. Type I is involved in the diffusion of respiratory gases. Type II is involved in the production of surfactant. Into each alveolar sac opens a group of alveoli. Alveoli are shaped as tiny 'balloon-like' cells, to allow for efficient gas exchange and relatively easy inflation/deflation. The alveoli act as a specialised gaseous exchange surface in mammals, and therefore require constant access to the blood stream and air. This gas exchange occurs by the diffusion across type I cells and is aided by a large surface area, an extensive capillary network, a small diffusion path, and a fluid layer lining the alveoli. ...read more.

Middle

negative with respect to atmospheric pressure. The amount of net pressure required for inflation is dictated by the surface tension and radii of the alveoli. During inhalation the radii of the alveoli increase from about 0.05 mm to 0.1 mm. As surface tension exerts a slight inward pull, a slight negative pressure is set up around the adjacent capillaries, which may draw tissue fluid from them (Tissue fluid contains water, glucose, amino acids, fatty acids, glycerol, mineral salts, dissolved gases and vitamins). This impedes the exchange of gases between the alveoli and capillaries. The surface tension that would occur is due to the attraction between water molecules and tends to reduce the surface to its minimum, therefore minimising the efficiency of gas exchange. To increase the radii of the alveoli from .05 mm to 0.1 mm would require a large amount of outward pressure. One role of the surfactant in alveoli is to dramatically reduce the net amount of outward pressure required to inflate the alveoli. Type II cells (specialised epithelial cells) ...read more.

Conclusion

This keeps diffusion efficient in gas exchange. However, diffusion is not 100% efficient, i.e. not only oxygen diffuses into the blood and carbon dioxide only diffuses out. There is always some oxygen diffused out and carbon dioxide diffused in as the movement of gas particles is still random. When blood leaves the alveolus it contains the same partial pressure of oxygen and carbon dioxide as the alveolar air. Blood reaching the alveoli has a lower partial pressure of oxygen, and a higher partial pressure of carbon dioxide than the alveolar air. During this equalisation of pressures, the percentage saturation of the blood rises from about 70% to 90%. The composition of alveolar air, however, remains relatively constant throughout. However, alveolar air is very different from atmospheric air, containing over 100 times as much carbon dioxide and about 2/3 as much oxygen. The process of respiration is still inefficient because some alveoli are inevitably under-ventilated. In addition, a proportion of blood which goes to the lungs does not go through any alveolar capillaries and therefore never gets oxygenated, this leads to the result that the blood leaving the lungs is carrying its maximum capacity of oxygen. 1 ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Exchange, Transport & Reproduction section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Exchange, Transport & Reproduction essays

  1. Marked by a teacher

    What is Type 1 diabetes

    3 star(s)

    Diabetic acidosis is often triggered by an infectious disease. It can develop in anything from a matter of hours to a few days. Ways to help yourself In order to prevent diabetic acidosis from developing in the first place, tight control of blood glucose levels should be kept.

  2. Peer reviewed

    The comparison of antibacterial properties of herbal products and standard antibiotics

    5 star(s)

    In the final method the order of when the discs are soaked in the herbal oils will be altered, this is because waiting a while to ensure the filter discs had fully absorbed the products just wastes time. Therefore this will be made one of the first things to do in the investigation and not leave it till the middle.

  1. Peer reviewed

    "An investigation into the Respiration of Carbohydrate Substrates by Yeast."

    5 star(s)

    it was caused by the manipulation of the independent variable and not just by chance. Therefore, in this instance sucrose should not be counted significantly unequal to glucose, but the difference can, however, still be explained. It was expected that glucose would produce the most CO2 because glucose is a

  2. Rate of Respiration

    = 2832 342 1000 A control experiment will be conducted parallel to the actual experiment. The experimental control that I will be using will be a boiling tube containing yeast and will be placed in the same water bath as the experimental boiling tube (yeast and substrate together).

  1. the role of the microbiology department

    Many laboratories use the request form as a work sheet at the bench, so that the worker can be guided by its information in his choice of tests, interpretation of results and wording of reports. Reception of specimens For safety, the reception of specimens should be undertaken in a room separate from the reporting office and the working laboratories.

  2. How Structure and Function of Squamous Epithelium, Erythrocytes and Blood Vessels is Related

    Red blood cells are relatively small so that the haemoglobin molecules are in close proximity to the surface which allows oxygen to be picked up and released quickly. The red blood cells do not contain any organelles which means there is a lot more space for haemoglobin and as a result, more oxygen can be transported.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work