OVERALL PURPOSE
OBJECTIVES
PRE-CLASS PREPARATION
In the last classes you have learned about the macroscopic anatomy of the lung, have noted how the interaction of these anatomical structures moves both air and blood in and out of the lung, and have gained some appreciation of the types of measurements made at the gross level, and the informatics needs they give rise to.
The next question is, how do the lungs actually perform their function? That is, how do they transfer oxygen from air to blood? The first step in answering this question is to understand lung anatomy at the microscopic (or cellular level).
Understanding of lung anatomy at
this level will come about as you answer the following question: what separates air from blood within the lung?
Exercise 1
Try to answer the following questions based on your current knowledge of
lung anatomy, and your best guess about how air comes in contact with blood:
Are there air-filled spaces in the lung?
What are the spaces that contain the oxygen and carbon dioxide that diffuses in and out of the blood? How big are they?
Is their wall moist or dry?
How do they stay open or patent? Why do their walls not stick together?
What is the blood contained in within the lung?
What are the spaces that contain the blood, which absorbs the oxygen and gives off the carbon dioxide? How big are these blood-filled spaces?
Does air directly come in contact with blood or is there a barrier between them?
What does the barrier consist of? How thick is it? How many layers does it consist of?
How big is the aggregate surface area within the one lung across which oxygen and carbon dioxide exchange takes place? Guess!
As big as a
a. table top
b. boxing rink
c. soccer field
d. surface of Lake Washington
How is this surface area packed into the lung?
If you generated answers (guesses) to these questions based on your common sense knowledge, you will have formulated useful expectations (hypotheses) about the microscopic anatomy of the lung.
Refine these hypotheses and give them a concrete basis by exploring the resources.
Resources:
Annotated histological and electron microscope images of the lung
including some embryonic/fetal lung digitized from the slide collection of CR,
images of Boyden’s wax 3D reconstructions of pulmonary acinus and alveoli, and
from Nameroff’s web histology module relating to the lung; all correlated with
FM segments. Segments of histology text chapter on lung (Bloom and Fawcett or
other text specified by Nameroff).
Exercise 2. Consolidation of knowledge
Based on your initial answers to the questions in exercise 1 and your exploration of the resources, consolidate your knowledge by answering the following questions as well as you can. We will discuss these more in class.
What is a pulmonary alveolus?
What kind of tissue forms its walls?
What type of cell predominates in the wall of the alveolus? What is their shape?
Are there less numerous cells of a different type also present in the in the alveolar wall?
What is the name of at least two types of cells in the alveolar wall and what is the main function of each?
What unit is formed by the aggregation of neighboring alveoli?
What is the airway that is connected to an alveolar sac?
What is a pulmonary acinus?
What is the airway that is connected to a pulmonary acinus?
What is a bronchus?
What is a bronchiole?
What is the difference between a bronchus and a bronchiole?
What kinds of bronchioles are there?
What is the pulmonary capillary bed?
What is its spatial relationship to alveoli?
Is it connected to pulmonary arteries and veins?
Resource:
These questions can be answered by interacting with a composite diagram
of the pulmonary acinus in correlation with the FM, which provides access to
definitions, adjacency and connectivity relationships. For ABI and AMD students
restriction of labeling of the diagram will constrain the node level of FM to
be displayed (e.g., for ABI students only alveolus and bronchiole will be
labeled, whereas for AMD students all the structures).