HISTOLOGY OF THE DIGESTIVE SYSTEM I ... - Faculty.rmc.edu

II.
Microanatomy of the Tubular Portion of the Digestive Tract
A. Typical Pattern of Layers in Digestive Tract Walls (Figure 17.1)
1. Mucosa (lining of lumen)
a. Epithelium = varies with location: stratified squamous in the mouth, esophagus,
and anus; simple columnar in the stomach and intestines
b. Lamina propria = loose FECT
c. +/- Muscularis mucosae (thin) - smooth muscle
2. Submucosa
Loose to moderately dense FECT
3. Muscularis externa
Smooth muscle along most of the gut
Skeletal muscle near both ends of the gut
Usually consists of inner circular and outer longitudinal layers
4. Adventitia or Serosa
Adventitia = loose FECT (on organ surfaces embedded in connective tissue)
Serosa = loose FECT + mesothelium (on organ surfaces exposed to body cavities)
B. Oral Cavity and Pharynx (excluding nasopharynx)
1. Mucosa (Plate 44)
a. Epithelium = stratified squamous epithelium (Figure 16.2, 16.4)
The epithelium is heavily keratinized on the upper (dorsal) surface of the tongue, is
moderately keratinized on the hard palate and on parts of the gums, and is nonkeratinized
elsewhere.
b. Lamina propria + Submucosa (Figure 16.4)
The lamina propria and submucosa are not clearly separated in most of the oral
cavity and pharynx. A very thin layer of loose FECT occurs at the base of the
epithelium in most areas. Most of the deeper connective tissue is moderately dense
FECT or dense irregular FECT in most locations. Minor salivary glands
(compound sero-mucous, tubulo-acinar glands) lie in the connective tissue on parts
of the tongue and lateral walls of the oral cavity, and the connective tissue around
those glands is loose FECT. Nodular dense lymphoid tissue lies below the
epithelium lining the crypts of the tonsils.
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