Epithelia Epithelia will be discussed according to the following scheme: Type Number of layers Shape Line drawing Simple Squamous Cuboidal Columnar Covering and Lining epithelium Pseudostratified Stratified Squamous Cuboidal Columnar Urothelium (transitional) Type Function Cells Arrangement Shape Example Unicellular Glandular epithelium Exocrine Multicellular Simple Compound tubular alveolar tubular tubuloalveolar alveolar Unicellular Endocrine Multicellular Cords Islets Acini Follicles You should be able to: 1. Describe the basement membrane and its components. 2. Classify epithelial tissue, using cell shape, stratification and surface specialisations. 3. Recognise covering, lining and glandular epithelial. 4. Distinguish between and classify exocrine and endocrine glands and unicellular and multicellular glands. 5. Give examples of and explain the structure, function and location of epithelial tissue.
Each specimen must be studied as follows: 1. General structure a. The number of cell layers, i.e. squamous or stratified. b. The differences in size and shape of these cells i.e. squamous, cuboidal, columnar etc. c. Cell borders visible or not. d. Position of the cells in relation to each other and the underlying basal lamina. e. Nature of the free or luminal surface e.g. ciliated, brush border etc. f. Presence of glands and hair. g. Types of glands present e.g. single cell, simple, tubular etc. 2. Cell structure a. Nucleus Staining reaction and degree of granularity of chromatin. Position in the cell. Shape and size. Shape and size in comparison to the shape and size of the cell. b. Cytoplasm General appearance and texture. Staining reaction. Presence of inclusions such as prominent granules, vacuoles, pigments etc. Question: Decide how you will systematically approach identification of the type of epithelium on a slide.
Glandular epithelium Objectives You should be able to: Recognise exocrine and endocrine glandular epithelium. Describe, discuss and identify mucous and serous secretory cells. Classify and identify different types of exocrine glands. Classify and identify different types of endocrine glands. Compare and contrast exocrine and endocrine glands. Explain the different ways of secretion from cells, and the role of myoepithelial cells in epithelial glands. Describe and discuss the functions of each of the components. Tasks Complete the drawings for each slide in the practical workbook. Slides Exocrine Slide name Slide number Stain Goblet cells & simple tubular glands Compound tubulo-alveolar glands 42 50 Secretory units 39 Secretory units 7 Endocrine Islands (pancreas) 50 Groups (pituitary gland) 52 Cords (adrenal gland) 56 Follicles (thyroid gland) 55
Slide 7: Tongue A coronal section through the distal part of the tongue. The tip of the tongue or pharyngeal tube (slide 39) is used as examples to study serous, mucinous and mixed secretory units. 1. View the slide at low magnification. The free surface and attached area should be visible. Below the free surface, layers of muscle tissue interspersed with glandular tissue is visible. Blood vessels and scattered fat cells are also present. The glandular tissue of the tongue can be found between the bundles of muscle fibers. 2. View the slide at high magnification. Cellular detail should now be discernible. 1. What is secreted by the glands in the tongue? 2. What type of epithelium is present on the dorsal surface of the tongue? 3. What type of epithelium is present on the undersurface of the tongue? 4. Muscles normally have an origin (fixed) and insertion (moving). Muscle fibres run longitudinally between the origin and insertion. In what direction does muscle fibres of the tongue run? 3. Identify the following tissues and structures in the tongue: 1. Papillae 2. Epithelia 3. Muscle fibres 4. Fat cells 5. Glandular tissue. 1. Serous units 2. Mucinous units 3. Mixed units serous demilunes 4. Make an annotated diagram of the tongue, indicating the different layers, tissues and structures. 5. Make a detail drawing of a section of the tongue, illustrating the three types of secretory units. Clearly indicate the differences in morphology. 1. Twist and fold your tongue. Why is the tongue able to perform such complex movements? 2. How is the anterior and posterior parts of the tongue divided? 3. How does the anterior and posterior parts of the tongue differ? 4. Where do the secretions of the serous demilunes go? 5. Complete the following table to illustrate the differences between mucinous and serous units: Mucinous Serous Shape of unit Staining of cells in unit Shape of nucleus Lumen
Slide 42: Large intestine This specimen is a longitudinal section through the large intestine. This specimen is used to study the colon (organ), different types of connective tissue cells (cells) and simple tubular glands (structure). 1. View the slide on low magnification. You should see the lumen and several layers of colon tissue. 1. List the cells found in the colon. 2. List the tissues found in the colon. 3. List the structures found in the colon. 4. List the glands found in the colon. 2. Identify the following: 1. The longitudinally sectioned colon. 2. The luminal surface. 3. A dark pink zone, the mucosa. 4. The epithelium of the colon. 5. Lamina propria of the mucosa. 6. A central lighter coloured area, with fine pink coloured structures, the submucosa. 7. And outer irregular area, the outer muscular layer or muscularis mucosa. 8. The serosa 1. What is a single cell gland? 2. Describe a simple tubular gland. 3. What cells line a simple tubular gland? 4. What are the subdivisions of the mucosa? 3. View the slide at appropriate magnification, and identify the following: 1. A single cell gland, the goblet cell. 2. A simple tubular gland in longitudinal and cross section. 1. Describe the shape of a simple tubular gland in your own words. 2. What cells line the simple tubular gland? The simple tubular gland is a test tube shaped structure and is lined with goblet cells and columnar epithelial cells. 4. View the slide at higher magnification. 5. The mucosa comprises an epithelial layer and a loose connective tissue layer, the lamina propria. In the lamina propria, locate as many of the following cells as possible: 1. Fibroblasts 2. Plasma cells 3. Macrophages 4. Mast cells 5. Eosinophils 6. Lymphocytes 7. Smooth muscle fibers 1. What are the functions of each of the cells listed? 2. What is a distinguishing feature of each of the cells listed? 3. What is characteristic of a goblet cell?
6. Make an annotated drawing of each of the cell types. List their distinguishing characteristics, the function of each cell and other tissues, organs and structures where they can be expected to occur. 7. Make an annotated drawing of a goblet cell as well as a simple tubular gland (with goblet cells and columnar epithelial cells), as seen in longitudinal section. 1. What are the distinguishing characteristics of the crypts as far as their structure and arrangement are concerned? 2. What is typical of the outer layer of m. externa? 3. What are the similarities and differences between the colon, appendix, vermiformis, ileum and duodenum? 8. Make an annotated line diagram of the colon.
Slide 50: Pancreas This specimen is a section through the pancreas. The pancreas is a compiund tubulo-alveolar gland with exocrine and endocrine tissue. It is used to demonstrate the histology of the pancreas, the organisation of exocrine and endocrine glands and the endocrine section of the pancreas. 1. View the slide at low magnification. The mass of pancreatic tissue should be visible. Lobules, ducts, connective tissue septae and blood vessels could also be visible. 1. Endocrine glands secrete into. 2. Exocrine glands secrete into. 3. What are the main components of the pancreas? 4. Classify the pancreas, using the classification of epithelium. 5. What cells, tissues and structures do you expect to find in the pancreas? List the functions of each of these as it pertains to the pancreas. 6. How is the tissue of the endocrine pancreas arranged? 7. Name the three types of connective tissue fibres. Give an example of the distribution of each. Give the function of each type of connective tissue fiber. 2. Identify the following: 1. The mass of pancreatic tissue. 2. Lobules. 3. Septae. 4. Ducts. 5. Islands of endocrine tissue. 1. What are expected around the ducts? 3. View the slide at higher magnification. Fine structure and cellular detail should become visible. 1. What shape are the exocrine secretory units of the pancreas? Groups of cells arranged as round or elongated secretory units around a central lumen. 2. How is the endocrine tissue of the pancreas arranged? 3. What are centro-acinar cells? 4. Identify the following: 1. Exocrine tissue. 2. Lobules, ducts and blood vessels and connective tissue septae. 3. Round or elongated secretory units. 4. Acini. 5. Centro-acinar cells. 6. An islands of endocrine tissue surrounded by exocrine tissue. 7. Inside the islands, cords of island cells. 8. Capillaries. 1. As what type of gland is the exocrine pancreas classified? 2. What are the characteristics of the exocrine glandular cells? 3. Why do the secretory units have different shapes in a section? 4. What zones are found in the cells of an acinus? 5. Of which structures of the pancreas are the centro-acinar cells part of?
6. What types of secretory ducts are found in the pancreas? 7. What is typical of the epithelium of ducts? 8. How are the cells of the endocrine pancreas organized 9. What structures are found in between the endocrine cells? 10. What types of cells form an islet? 5. Make annotated drawings and diagrams (select as appropriate) of the following: 1. A line diagram showing the low magnification composition of the pancreas. 2. A line diagram of the secretory units in longitudinal, cross, as well as oblique sections. In the line drawing of the cross section also draw the cells forming the unit. 3. A few cells of an island. Demonstrate the cellular arrangement in the island clearly. Additionally, draw a few (generic) cells to demonstrate the shape of groups, cords and follicles. Refer to slides 52, 55 and 56 (hypophysis, thyroid and adrenal glands) for review. 4. For each of the above drawings and diagrams, add additional detail to clarify cellular arrangements and structural relations. 5. Make an annotated drawing of a section of exocrine acini and the endocrine areas. Make a line diagram to illustrate the hierarchy of ducts and blood vessels supplying and draining the pancreas. Clearly indicate endocrine and exocrine structures Slide 52: Pituitary gland This is a longitudinal section through the pituitary gland. 1. Make an annotated line drawing showing the different component parts of the pituitary gland at very low magnification. Indicate the embryological origin of each part. Indicate blood flow into and out of the pituitary gland. 1. What is colloid? 2. Name three types of capillaries and give an example where each occur. 3. What is a portal system? 4. What cells make up the pars distalis of the pituitary gland? 5. What cells occur in the pars nervosa of the pituitary gland? 6. What are pituicytes? 7. What are Herring bodies? 8. What is the function of Herring bodies? 9. Describe an axon on cross, oblique and longitudinal section. Make a line drawing to assist. 10. Provide the function for each of the cells, tissues, structures and organs above. 2. View the pituitary gland at very low magnification. At this magnification, you should be able to see the whole gland. One portion of the gland is stained darker than the other, with an attachment at the border of the two areas. 3. Identify the following: 1. Pars distalis, pars intermedia and pars nervosa.
4. Cells in the pituitary gland are arranged in groups. Groups of cells are separated by connective tissue and sinusoidal capillaries. On a slide at high and very high magnification, find groups of cells, connective tissue and blood vessels. 5. The pars distalis of the pituitary gland contains five cell types. Complete the following table with regards to the five cell types: Cell Type % of cells Size of cells Shape Staining Nucleus Somatotrope 50% Medium Oval Acidophil Round & central Lactotrope 15-20% Large Polygonal Acidophil/Chromophil Oval and central Corticotrope 15-20% Medium Polygonal Basophil Round & eccentric Gonadotrope 10% Small Oval Basophil Round & eccentric Thyrotrope 5% Large Polygonal Basophil Round & eccentric 6. Find colloid on a slide. 7. Find an example of each of the cells making up the posterior part of the pituitary gland. 8. What constitutes the bulk of the pars nervosa? Find the pars nervosa at low magnification and the corresponding high magnification view. 1. Where does the structures constituting the bulk of the pars nervosa originate? 2. What are unique about the structures in the pars nervosa? 3. Why are they different from similar structures elsewhere in the body? 9. Find an example of Herring bodies on a slide. 1. In which part of the pituitary gland does Herring bodies occur? Slide 55: Thyroid gland This slide is a section through the thyroid gland. 1. Make a list of the component parts of the thyroid gland. Include cells, tissues and structures. Give the function of each of the component parts. 1. What are the two divisions of epithelial tissues? 2. How are epithelium classified? 3. What are the two divisions of secretory epithelium? 4. What is colloid? 5. What is the functional unit of the thyroid gland called? 6. What type of capillary is present in the thyroid? 7. How are cells in the thyroid arranged? 8. Follicular epithelium is simple cuboidal. 9. Name the two types of cells contained in follicular epithelium.
2. View a low magnification slide of the thyroid gland. On this view, you should be able to see the structures composing the thyroid gland. Cellular detail must be reviewed at higher magnification, keeping the macroscopic positions in mind. 3. View the thyroid at high magnification. Cells and tissues should be visible. Identify the following: 1. Follicles 2. Clear cells 3. Connective tissue 4. Make an annotated drawing of the thyroid gland, indicating the structures identified above. Give the function of each. Clearly indicate the capsule, lobes and lobules. 1. What are the structures that form the follicles? 2. What are parafollicular cells? 3. What are clear cells? 4. Where are clear cells found? 5. How is the connective tissue organised? 6. What other structures inside the pancreas could be mistaken for endocrine tissue? Slide 56: Adrenal glands This slide is a section through an adrenal gland. 1. View the slide on low magnification. The gland and it capsule should be visible. 1. Epithelium are divided into two main groups. What are the two main groups? 2. Glandular epithelia are often described based on the cellular organisation in the gland. What are the organisation seen in exocrine glands? What are the organisation seen in endocrine glands? 3. How are the cells in the adrenal gland arranged? 4. Compare the thyroid gland, parathyroid glands and adrenal glands with regard to capsule and connective tissue arrangement. 2. At low magnification, identify the following: 1. Capsule 2. Cortex and medulla 1. What is typical of the capsule of the adrenal glands? 2. What zones can be identified in the cortex? 3. At high magnification, find the capsule of the gland. 1. Are there components of the outer capsule penetrating the gland? 2. What structures are present in the capsule? 4. At high magnification, identify the zones of the cortex. 1. How is the cortex supplied with blood? 2. Describe the dual blood supply system of the medulla.
3. What are the main products of each of the three zones of the cortex? 4. Describe the cells typical of each of the three zones of the cortex. 5. Chromaffin cells in the medulla are considered the equivalent of postganglionic neurons. Why? 6. In addition to chromaffin cells, what other cells with connections to the abdominal organs are present in the adrenal medulla? 5. At high magnification, find the medulla of the adrenal gland. Identify as many of the components of the medulla listed above. 1. What are the distinguishing features of the medulla? 6. Make an annotated drawing of the adrenal gland. Show detail of the different components. Questions 1. How does the pituitary gland and the hypothalamus communicate? 2. What four elements make up the thyroid gland? 3. Name the divisions and zones of the adrenal glands and the hormones secreted by each. 4. Name the five distinct types of endocrine cells of the anterior pituitary. 5. What changes take place in the thyroid follicular cells during an active secretory phase? 6. Name the three main cell types seen in the parathyroid. 7. What do the cells of the adrenal medulla contain? 8. Name the four main cell types of the endocrine pancreas. 9. Make a table listing nine endocrine glands/organs and the hormonal secretions of each. 10. Explain the differences between endocrine and exocrine glands. 11. List the hormones released by the heart, kidneys, and other organs with secondary endocrine functions. 12. Describe the types of intercellular communication, their importance, mechanisms, and effects. 13. What role does thyroid hormones play in the regulation of basal metabolism? 14. Name the five distinct types of endocrine cells of the anterior pituitary. 15. What changes take place in the thyroid follicular cells during an active secretory phase? 16. Name the three main cell types seen in the parathyroid. 17. What do the cells of the adrenal medulla contain? 18. Name the four main cell types of the endocrine pancreas. 19. What are the general characteristics of the endocrine system? 20. Oxyphil cells are located in which organ? 21. What is unique about the structure of the thyroid gland. 22. Compare the structure of the thyroid with that of the parathyroid. 23. What is the cell source of calcitonin, melatonin, cortisol and epinephrine?