Reading: RR & K, Chapter 18
SLIDE 68a olfactory epithelium (H&E)
(RR&K p549, Fig. 1,2; p534, Fig. 18.4)
This is a frontal section through the nasal cavity. Orient yourself on this slide, identify nasal conchae and nasal septum. Observe the lining of the nasal cavity which is represented by a typical pseudostratified columnar ciliated epithelium (respiratory mucosa) with few scattered goblet cells. In the upper portion of the nasal cavity find an area of thicker epithelium which has many layers of nuclei. This is the olfactory epithelium. The majority of the nuclei in the olfactory epithelium belong to olfactory cells, which are receptor bipolar neurons. The outer layer of the cells represents supporting cells. The basal cells can be found adjacent to the basement membrane. This thick pseudostratified epithelium has tubulo-alveolar (Bowman's) glands located in the lamina propria beneath the epithelium. In addition, there is an abundance of blood vessels and occasional nerves beneath the olfactory epithelium.
Check list for SLIDE 68a:
SLIDE 69b larynx, human (H&E)
(RR&K p551, Fig. 1,2,3,4)
This slide represents the frontal section of the lateral wall of the human larynx. Larynx has a framework of hyaline cartilages (thyroid, cricoid) in which the process of endochondral bone formation may begin at an early age. Localize the hyaline cartilage of the cricoid ring and observe whether bone formation is evident. Next observe the epithelium lining the larynx. The respiratory epithelium covers the entire larynx, except for the vocal folds, which are covered by the stratified squamous non-keratinized epithelium. Find the vocal folds on your slide. A lighter stained area deep to the vocal folds represents a cross- section of the vocal ligament, which is associated with the vocalis muscle. What muscle type is this muscle? Follow the epithelium into the laryngeal ventricle and around the vestibular fold. Observe the epithelial changes from stratified squamous epithelium into respiratory epithelium. Also observe mixed serous and mucous glands in the submucosa, especially near the vestibular fold. Note the presence of lymphatic nodules located in the submucosa.
Check list for SLIDE 69b:
SLIDE 70a trachea (H&E)
(RR&K p539, Fig. 18.9; p552, Fig. 1,2,3,4)
The trachea is a hollow cylinder with a flat posterior wall, consisting of four layers:
The mucosa consists of an epithelium and a lamina propria (loose connective tissue). The pseudostratified columnar epithelium is comprised of three types of epithelial cells: basal cells, ciliated columnar cells, and goblet cells. Migrating lymphocytes (which monitor potential antigens that may penetrate the epithelium) may also be present. The epithelium is anchored to the basement membrane, a thick, pink-stained region adjacent to the epithelium. The lamina propria will contain many immune cells such as lymphocytes and plasma cells.
The submucosa is dense connective tissue with various glands embedded in it. These glands contain mucous and serous-secreting cells. Secretions are released into the air passage of the trachea via ducts which are lined by simple or stratified cuboid epithelium.
The muscularis and cartilage layer contains smooth muscle and hyaline cartilage. In specimens from young individuals, tracheal rings are made of the hyaline cartilage. Your preparation probably came from an older subject since the cartilage has a somewhat calcified appearance. Smooth muscle can be found in the posterior wall of the trachea.
The adventitia contains large nerves, lymphatics and blood vessels, fat, and occasional lymph nodes. However, in this preparation, the adventitia is not well preserved.
Check list for SLIDE 70a:
SLIDE 71a lung, monkey (H&E)
(RR&K p553, Fig.4; p555, Fig.1,2,3; p557, Fig. 1,2,3,4)
Based on their functional roles in the lung, the air passages can be classified as conducting or respiratory portions of the lungs. You will first examine the elements of the conducting portion (e.g., bronchi, bronchiole, and terminal bronchiole).
The bronchi are typically lined by the respiratory epithelium. The supporting cartilage is seen as irregularly-shaped plates. Bundles of smooth muscle located between the epithelium and cartilage completely encircle each bronchus. The height of the respiratory epithelium decreases as the diameter of the bronchus gets smaller. The number of glands and goblet cells also decreases as the bronchus becomes smaller. The bronchioles are lined by a simple columnar epithelium which contains ciliated and nonciliated (goblet and Clara) cells. Note the presence of smooth muscle and the absence of cartilage and glands around the bronchioles. Terminal bronchioles are lined by a simple columnar or cuboidal epithelium which consists of predominately nonciliated Clara cells (bronchiolar cells).
Identify the respiratory portion of the bronchial tree (formed by respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli). The respiratory bronchiole is basically a bronchiole with alveoli situated in its walls. It is lined by either a simple cuboidal epithelium containing Clara cells or by the simple squamous epithelium of the alveoli. The simple cuboidal epithelium situated between the alveolar pockets is supported by smooth muscle as seen in the conducting bronchiole. Within alveolar epithelium, you should examine type I pneumocytes, type II pneumocytes (great alveolar cells), as well as macrophages (dust cells).
The connective tissue surrounding the bronchi and larger bronchioles contains the vessels of the bronchial and pulmonary circulation. The bronchial vessels (arteries and veins) supply the nutrients to the supporting tissue and epithelium of the conducting airways. The large vessel that runs adjacent to each airway is a branch of the pulmonary artery. Note that the large branches of the pulmonary artery are that of elastic artery. The pulmonary veins are not located near the airways, but at the periphery of bronchopulmonary segments. The large branches of the pulmonary veins have a thick coat of cardiac muscle (try to identify striations, intercalated discs, etc.). In the connective tissue surrounding the large blood vessels and bronchi, identify fat tissue, small bronchial arteries and veins, nerves and ganglion cells.
In some areas around the bronchi identify regions with diffuse lymphatic tissue called (here in the lungs) the bronchus associated lymphatic tissues (BALT).
Check list for SLIDE 71a:
SLIDE 71b lung, monkey (Masson)
(RR&K p553, Fig.4; p555, Fig.1,2,3; p557, Fig. 1,2,3,4)
On this slide examine the distribution of the connective tissue in the lung. Review the general organization of the lung as seen in SLIDE 71a above. Identify the bronchus and bronchiole based on the presence of cartilage. Observe the wall of different sections throughout the bronchi and bronchioles to compare these differences. In addition, examine the thick layer of cardiac muscle around the large branch of pulmonary vein. On higher magnification you will be able to identify distinct striations and intercalated discs. Identify the bronchial vessels providing blood supply to the bronchial tree. This is a good slide for observing the distribution of collagen near the visceral pleura, alveolar wall, and branches of the bronchial tree.
Check list for SLIDE 71b:
SLIDE 71p lungs emphysema (H&E)
(RR&K p553, Fig.4; p555, Fig.1,2,3; p557, Fig. 1,2,3,4)
Emphysema is an abnormal and permanent increase in the size of those air spaces distal to the terminal bronchiole. This is often accompanied by destructive changes in the terminal bronchioles. With the low power objective, scan this slide and identify the irregular, large air spaces formed by destruction of interalveolar septa of neighboring alveoli. Compare this slide with normal lung tissue organization as seen on SLIDE 71a. Identify respiratory bronchioles, and the small arteries associated with them. Can you find here any difference between this section and the normal lung organization? Also in the air spaces identify the numerous alveolar macrophages loaded with hemosiderin. Those cells are indicative of chronic pulmonary congestion which follows chronic congestive heart failure. They have been referred to as heart failure cells. In the septa between the air spaces identify macrophages loaded with anthracoid pigment and needlelike, birefringent material (silica). These macrophages can be found in any urban adult lungs and may be quite prevalent in individuals who have had significant exposure to smoke or other occupational hazards. On the same slide find the area with bronchial associated lymphatic tissue (BALT). This is a good slide for review of other cell types found in alveoli.
Check list for SLIDE 71p:
This unit focuses on the structures of the respiratory system which serve the functions of air conduction, air filtration, and respiration.