Objectives:

 

I.          General considerations

            A.        Characterize epithelium as a basic tissue.

                        1.         Sheet of interconnected cells that covers surfaces or lines a cavity.

                        2.         Is avascular.

                        3.         Cells exhibit polarity.

                        4.         Form glands.

 

II.          Histology

            A.        Introduce morphologic basis for classification of epithelia.

            B.         Emphasize value of epithelial morphology in organ identification.

1.         Simple squamous epithelium - e.g., lines blood vessels, body cavities,

and thin segment of renal loop.

2.         Simple cuboidal epithelium -  e.g., lines ducts and forms secretory units of glands.

3.         Simple columnar epithelium - e.g., lines organs such as intestines and

uterus that perform secretory and absorptive functions.

4.         Pseudostratified columnar epithelium - e.g., found in respiratory (trachea, bronchi)

and reproductive (uterus, oviduct) organs.

5.         Stratified squamous epithelium - e.g., forms epidermis of skin and lines esophagus.

6.         Stratified cuboidal epithelium - e.g., rare but may be found lining ducts of glands.

7.         Stratified columnar epithelium - e.g., rare but may be found in large ducts.

8.         Transitional epithelium - e.g., capable of considerable distention and is found in

urinary bladder.

 

III.         Border modifications

            A.        Correlate border modifications to functional significance.

                        1.         Microvilli - increase surface area for transport mechanisms.

2.         Glycocalyx - protective layer;  site of function of various digestive enzymes.

                        3.         Cilia - protective; aid in movement of particles and mucus in lumen.

                        4.         Basal lamina - selective diffusion barrier.

5.         Junctional complexes - adherence of adjacent cells (at apical lateral borders).

                        6.         Desmosomes - "spot" adherence of adjacent cells.

7.         Gap junctions - channel for movement of ions and small molecules between cells

and for electrical contact.

 

IV.        Glands

A.        Develop an understanding of the morphological variation of glands and their mode of secretion.

                        1.         Endocrine - secretion is released into body vasculature (ductless).

a.         Consist of cords or clumps of cells - e.g., adrenal gland, adenohypophysis.

                                    b.         Consist of follicles - e.g., thyroid gland.

                        2.         Exocrine - secretion released into ducts that carry product to sites of utilization.

                                    a.         Simple tubular glands - e.g., sweat glands, gastric glands.

                                    b.         Simple acinar (alveolar) glands - e.g., sebaceous glands.

c.         Simple tubuloalveolar (tubuloacinar) glands - e.g., buccal glands.

                                    d.         Compound tubular glands - e.g., liver, kidney.

e.         Compound tubuloalveolar (tubuloacinar) glands - e.g., mammary gland, prostate

gland, pancreas, parotid gland.

 

Epithelium: Slide List

 

16                                       pig heart

1                                         canine ovary

82                                       bovine kidney

84                                       canine bladder

159                                     horse duodenum

96                                       canine trachea

164                                     canine anus & rectum

135L                                   cow teat

150                                     canine esophagus

118                                     cow uterus

140                                     canine parotid gland

88                                       thyroid follicles and parathyroid gland