Lung Physiology and
Image from http://www.britannica.com/EBchecked/topic-art/351473/107200/The-alveoli-and-capillaries-in-the-lungs-exchange-oxygen-for
Breathing and Lung Physiology
- The lung is the
location of a fast exchange of carbon dioxide for oxygen. Carbon dioxide
is a waste product of cellular respiration and is brought to the lungs
by heoglobin and escapes the body. The empty hemoglobin can then bind
oxygen carry it in the blood to all of the cells in the body.
contracts to pull on pleural membrane, allowing lungs to open
rushes through the buccal cavity, down the trachea, bronchi, and
bronchioles until it reaches the alveoli
alveoli are the site of gas exchange
is only a 2µM distance between the lumen of the alveoli and the red
blood cells in the capillaries
pressure differences allow oxygen (in the alveoli) and carbon dioxide
(in the red blood cells) to exchange places via passive diffusion
(Sadava et al. 2008).
= comprised of 2 cells: type one pneumocytes and type 2 pneumocytes
(Kathuria et al. 2007; Wang et al. 2006).
95% of alveolar cells
of gas exchange
the structural support of the alveoli
manage lung fluid homeostasis
5% of alveolar cells
and alter surfactant
in both the immune and inflammatory responses
2 cells proliferate and transform into Type 1 cells to repair alveolar
walls; they are vital to lung function (Wang et al. 2006)
Image from http://legacy.owensboro.kctcs.edu/gcaplan/anat2/histology/histo%20F%
Defense & Pathology
Because lung cells come in contact with the air they are vulnerable to
air born pathogens (like bacteria) and antigens (like pollen). SInce they are
the first line of defense, lung cells must protect not only themselves but
also the rest of the body from airborn pathogens.
Mechanisms for protection rely on excluding the antigen or providing a barrier:
of the Innate Immune System
lung cells secrete mucous to trap bacteria and potential pathogens
cells with specialized cilia sweep the mucous up towards the mouth
pathogens then exit the body when the mucous is coughed up (Sadava et
immune system “recognizes” an antigen through structural barriers or
microbial pattern recognition sequences, then it will induce an inflammatory
response (Hollingsworth et al. 2007).
response is marked by the “respiratory burst” of activated leukocytes,
causing surrounding cells to uptake oxygen and release reactive oxidative
species (ROS) into the interstitial fluid (Chen et al. 2007; Balmes 1993).
of oxygen allows neighboring cells to increase mitochondrial activity
(vital for mitosis)
of ROS is an attempt to harm antigens more than the organ itself (Felty
et al. 2003).
in decreased lung function due to pulmonary edema and epithelial cell
injury (Chen et al. 2007; Balmes 1993).
Despite these defense mechanisms, certain antigens are still able to damage
the lung tissue and cause the diseases such as asthma, acute respiratory
distress syndrome (ARDS), chronic obstructive pulmonary disease (COPD) and
Image from http://www.jci.org/articles/view/6277/figure/1