Anatomy and Human Biology 2214
September 28, 2009
M. Hall
RESPIRATORY SYSTEM LAB
You should be able to recognize the following structures:
Nasal Cavity:
respiratory epithelium
mixed glands
cilia
goblet cells
olfactory mucosa
olfactory epithelium
basal cells
Bowman's glands
olfactory nerve fibers
nasal septum
nasal conchae
swell bodies
Trachea:
mucosa
U-shaped cartilage rings
mixed glands
trachealis muscle
Lung:
visceral pleura
bronchus
bronchiole
respiratory bronchiole
alveolar duct
smooth muscle in alveolar duct wall
pulmonary artery
pulmonary vein
capillary
alveolus
interalveolar septum
type I epithelial cell
type II epithelial cell
alveolar macrophage
Larynx:
epiglottis
elastic cartilage (H&E and elastic stains)
dorsal and ventral epithelium
true vocal cord
vocal ligament
vocalis muscle
false vocal cord
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Slide descriptions
D-83 Nose, monkey (H&E). Begin the study of this slide by gross observation with the aid
of the diagram of a coronal section in your printout. If you hold the slide as oriented you
can see the hard palate at the right consisting of the palate bone and the oral mucosa on its
surface. The nasal septum is in the midline towards the left. The large cavities are the air
passageways, and protruding into these spaces are two large masses on each side that
represent the middle and inferior nasal concha. Turbinate bones support the conchae.
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These bones have yellow bone marrow inside which makes them look hollow. In removing
this block of tissue, the maxillary sinuses were largely cut away, but their medial walls
remained intact on some of the slides. The sinuses communicate with the nasal cavity by a
small meatus. Just above and below the hard palate, parts of maxillary tooth roots may be
found embedded in their sockets. The mucosa of the entire nose is underlain by bone,
except for the mid anterior part of the nasal septum, which is cartilage. This cartilage abuts
directly with the bone of the bony septum. Farther down in the respiratory passageway the
supporting tissue shifts entirely to cartilage.
Note at low magnification that most of the lining of the nasal cavity, including that of the
sinus walls, is made up of respiratory epithelium (pseudostratified ciliated epithelium with
goblet cells). Numerous mixed (serous and mucous) glands extend into the lamina propria
from the epithelium. This respiratory mucosa covers most of the respiratory passageway
from the nose all of the way down through the bronchi. Study the various cell types at
higher magnification. Now compare the epithelium in various parts of the nose. The
lamina propria is extremely richly vascularized to provide an ample supply of blood to cool
or warm the inspired air as appropriate. On the conchae the blood vessels are exaggerated
into large venous plexuses called swell bodies. Their dilation and engorgement controls the
passage of air through each side of the nose. These are the vessels that "stop up" your nose
during allergic reactions, and this can be temporarily alleviated by vasoconstrictive drugs.
Olfactory mucosa covers a relatively small, specific region of the upper part of the septum
and the upper part of the lateral walls of the nasal cavity, including the superior concha. It
is concerned with the sense of smell and is fundamentally nervous tissue. Olfactory
epithelium is a pseudostratified columnar type which is taller than the adjacent respiratory
epithelium. In this slide, even under low power, the sudden transition from respiratory to
olfactory epithelium is readily apparent, since the goblet cells and mixed glands of the
former abruptly stop at the edge of olfactory epithelium. The lamina propria underlying
the olfactory epithelium does have numerous glands. These are the rather specialized
serous glands (Bowman's glands) that provide a fluid to wash away old odors. One of their
distinctive structural characteristics is that their ducts enlarge just under the surface
epithelium. Olfactory epithelium is made up of three cell types. Most numerous are
sustentacular cells ( = supporting cells). They extend from the basement membrane to the
surface. The olfactory neurons are the critical cells of the epithelium. They are round with
two processes. A dendrite goes to the surface where it sprouts several long non-motile
stereocilia which bear the receptors for odoriferous molecules. The neurons also send an
axon down through the basement membrane. It joins with others in the lamina propria to
form an axon bundle which travel to the olfactory lobes of the brain (a very short distance).
The nuclei in those axonal bundles, of course, belong to Schwann cells, characteristic of
peripheral nervous tissue. The third cell type is the basal cell. It is the stem cell, able to
divide and differentiate into both sustentacular cells and olfactory neurons. Olfactory
neurons are very unusual in that they can be replaced by new neurons that differentiate in
an adult. This is pretty important because the cell bodies of these neurons are very exposed.
D-99, Larynx and epiglottis (H&E) The epiglottis is shown attached to the wall of the
larynx. The epiglottis is a flap of tissue, which closes off the upper entrance to the larynx
during swallowing. The epithelium reflects the local pattern of abrasive stresses, so that the
upper anterior surface is covered with stratified squamous nonkeratinized epithelium. The
lower ventral surface is lined largely with pseudostratified columnar ciliated epithelium
except along the periphery where it slaps down on the rim of the larynx during swallowing.
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The submucosa has substantial amounts of elastic fibers, blood vessels and on the posterior
surface, nicely visible mixed mucous-serous glands.
D-100 Vocal Cord (H&E). Hold this slide vertically, with the label at the top. This is a
longitudinal section through the side wall of the larynx. It passes through the false vocal
cord above and the true vocal cord below. These two cords are separated by a cleft called
the ventricle. They can be seen easily with the naked eye, and you should appreciate where
they are in terms of gross anatomy.
The true vocal cord contains two main functional components, the vocalis muscle and the
vocal ligament. Both appear in cross-section on this slide. Skeletal muscle is easily
recognized, but the ligament is a bit trickier to identify. There has been some inevitable
tissue shrinkage which has separated the thick round collagen fibers from each other a bit.
Among them are fibroblast nuclei looking small and round because they are elongated in
the direction of the fibers. The vocal ligament is overlain with a stratified squamous
epithelium. (A patch of hyperplastic epithelium may be present on the true vocal cord. If
so, or if not, do not worry about it). The transition between the stratified squamous
epithelium and the surrounding typical respiratory epithelium is relatively sharp. The
muscles and muscular actions which control the tension in the vocal cords are very
complex.
The false vocal cord is not much to write home to Mom about. It is covered with typical
respiratory epithelium and has a large number of mixed glands in the submucosa.
Lymphocytes almost invariably infiltrate into the tissue around the ventricle between the
false and true vocal cords.
D-80 Trachea (H&E). The respiratory tree begins with the trachea. Exactly what is visible
on your slide depends on whether the plane of section passes mainly through one of the Ushaped supporting cartilages, or between the two neighboring cartilages. The cartilages are
U shaped instead of complete rings. A band of smooth muscle, the trachealis muscle,
stretches between the two ends of a cartilage to form the posterior wall of the trachea. The
muscle fibers insert into the dense elastic fiber bundles surrounding the tracheal cartilages
and are joined to the mucous membrane by a layer of loose connective tissue. The mucosa
is typical of the respiratory tract. Note its very tall pseudostratified ciliated epithelium.
D-75 Bronchial tree (H&E), This slide has sections through a branching bronchus and
associated structures. Note the typical respiratory epithelium with goblet cells, plates of
cartilage, smooth muscle and mucous glands in the lamina propria and submucosa of the
bronchi. The smooth muscle is a particularly important component. It has the form of
ribbons that spiral down the bronchus and continue along the air passage ways all the way
down to the alveolar sacs. These bronchi are intrapulmonary (i.e. within the lung) as
shown by the presence of lung tissue around them. Do not waste much time examining this
lung tissue because it has been allowed to collapse, is poorly preserved and has
pathological features.
Branches of the pulmonary artery and pulmonary vein accompany the bronchi, getting
smaller and smaller as the size of the bronchus decreases. You should be able to distinguish
artery from vein if you keep in mind that pulmonary arteries have relatively thin walls for
their size. The walls are thin because the pulmonary blood pressure is considerably lower
than the systemic.
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You cannot miss seeing the clusters of macrophages, black from the dust particles that
they have ingested. Examine several of the clusters and note that they are located in seams
of connective tissue. This is where macrophages permanently retire after they engorge
themselves with indigestible particles. Many of the macrophages have taken up so many
dust particles that the only detail you can see is their cell boundary.
D-77 Lung monkey (H&E). This slide is excellent for observing the smaller parts of the
respiratory tree. Using low magnification you are able to observe: bronchus, respiratory
bronchiole, alveolar duct, alveolar sac, alveolus and interalveolar septum. Because this
monkey was small you will find relatively few bronchioles. All or nearly all of the
candidates will have at least a bit of cartilage to one side. At higher magnification, look at
the epithelium, glands and smooth muscle of the bronchi.
Next, find a respiratory bronchiole. Note its relationship to the pulmonary artery.
Typically, the two run next to one another with the alveoli extending from the portion of
the wall of the bronchiole farthest from the artery.
Alveolar ducts are particularly difficult to comprehend, yet they are a most important
structural entity. Only they and alveolar sacs can significantly expand or contract during
inspiration or expiration of air. Thus, volume change is an accommodation of these ducts.
To pick out alveolar ducts it is necessary to realize that the alveoli themselves are not parts
of the walls of the ducts but outpocketings from the walls. If the structure of the alveolar
duct is not completely clear to you consult your lecture notes or textbook or talk with us.
Alveolar sacs are merely the somewhat expanded tip ends of alveolar ducts. They have the
same basic structure and function as the ducts - and are no big deal.
Use 40X to study the interalveolar septum. It is formed of two extremely attenuated sheets
of epithelium enclosing many capillaries and very little other connective tissue. The many
elongated nuclei belong largely to type I epithelial cells and endothelial cells. It is not
possible for you to distinguish between these two cell types. The two other cell types are
type II epithelial cells (septal cells) and macrophages. Type II cells are cuboidal and
usually occur in the corners where two interalveolar walls come together. They produce
surfactant. Alveolar macrophages can be found anywhere. Once laden with dust they like
to retire to a comfortable patch of connective tissue and just veg.
One thing to get straight is the blood vasculature. Pulmonary arteries run alongside the air
passageways as far down as respiratory bronchioles. Pulmonary veins, in contrast, go their
separate way when the bronchi become bronchioles. Be sure that you can tell pulmonary
arteries and veins apart . Obviously you will look at the smooth muscle in their walls to do
so. Be aware, however, that the walls of pulmonary arteries are thinner than those of
systemic arteries because the pulmonary blood pressure is lower.
D-79 lung human (H&E). Slide D-79 is human lung collected at autopsy in a routine
manner. It is not a pretty sight. The slide is included for comparison with the expanded
monkey lung. Because humans are big, D-76 allows you to see some large bronchioles.
Their longitudinal mucosal folds should be visible. Also, pulmonary arteries and
pulmonary veins are adequately preserved. Otherwise it is not worthwhile to look
extensively at this slide. If you just have to keep looking instead of going home, go back to
slide D-78.
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D-98 Epiglottis (elastic stain). The stain on this slide emphasizes the large amount of
elastica in the cartilage and throughout the epiglottis. Compare it with slide D-99 which is
stained with H & E.
D-83 Nose, Monkey (H & E)
D-99 Larynx & Epiglottis (H & E)
D-100 Vocal Cord (H & E)
D-80 Trachea (H & E)
D-75 Bronchial Tree (H & E)
D-77 Lung Monkey (H & E)
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D-79 Lung, Human (H & E)
D-98 Epiglottis (Elastic stain)
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