This document describes the histology of structures in the digestive system, including the tongue, salivary glands, and taste buds. The tongue contains four types of papillae - filiform, fungiform, circumvallate, and foliate - which vary in shape and presence of taste buds. There are three major salivary glands - parotid, submandibular, and sublingual. Each gland contains serous or mucous acini and a duct system to release secretions. Taste buds contain gustatory and supporting cells and detect different tastes.

1. Histology Digestive system- 1
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2. Tongue
• tongue is a muscular organ
– lined by a protective mucosa, that consists of an outer
epithelial layer and an underlying connective tissue layer
called the lamina propria
– core of the tongue consists of connective tissue and
interlacing bundles of skeletal muscle fibers.
– dorsal surface of the tongue is rough and characterized by
numerous mucosal projections called papillae
– In contrast, the mucosa of the ventral surface of the
tongue is smooth

4. Tongue
• Papillae
– The epithelium on the dorsal surface of the tongue is
irregular or rough owing to numerous elevations or
projections called papillae.
– All papillae on the tongue are covered by stratified
squamous epithelium that shows partial or
incomplete keratinization.
– four types of papillae on the tongue:
• filiform,
• fungiform,
• circumvallate,
• foliate.

5. Filiform Papillae
• The most numerous and smallest papillae on the surface of
the tongue are the narrow, conical-shaped filiform papillae.
• Covered by St. Sq. keratinized epithelium.
• Do not contain taste buds. They cover most of the front two
thirds of the tongue's surface.

7. Fungiform Papillae
• Less numerous but larger, broader, and taller than the filiform
papillae are the fungiform papillae.
• These papillae exhibit a mushroom-like shape and are more
prevalent in the anterior region of the tongue.
• Fungiform papillae are interspersed among the filiform
papillae.
• They have taste buds on their upper surface

10. Circumvallate papillae
• Circumvallate papillae are much larger than the
fungiform or filiform papillae.
• Contain taste buds on lateral surface.

11. Foliate Papillae
• Two parallel ridges and furrows on the
dorsolateral surface of tongue.
• Contain many taste buds on lateral side.

13. Taste Buds
• Onion shaped structures containing 50 – 100
cells.
• Rests in Basal Lamina
• Apical portion project microvilli that poke
through an opening called taste pore.
• 2types of cells are distinguished in relation to
taste buds
– Supporting or sustentacular cells
– gustatory cells

16. Salivary Glands
• There are three major salivary glands: the
parotid, submandibular, and sublingual.
– located outside of the oral cavity and convey their
secretions into the mouth via large excretory
ducts.
• Cells of the Salivary Gland Acini
– Serous cells
– Mucous cells

17. Parotid Salivary Gland
• The parotid gland is surrounded by a capsule from which arise
numerous interlobular connective tissue septa that subdivide
the gland into lobes and lobules.
– Each salivary gland lobule contains secretory cells that form the serous
acini.
– serous acini are surrounded by thin, contractile myoepithelial cells
that are located between the basement membrane and the serous
cells.
– intercalated ducts: small lumina, are lined by a simple squamous or
low cuboidal epithelium, and are often surrounded by myoepithelial
cells.
– striated ducts: larger lumina and are lined by simple columnar cells
that exhibit basal striations.
– Intralobular excretory duct: located within the lobules of the gland.
– Interlobular excretory ducts: in the connective tissue septa that
surround the salivary gland lobules.

21. Sub-mandibular gland
• Sub-mandibular gland is a mixed gland,
containing both serous and mucous acini, with
serous acini predominating.
• Duct system of the submandibular gland is
similar to that of the parotid gland.

22. Submandibular Gland(Hematoxylin-Eosin)

24. Sublingual Salivary Gland
• contains both serous and mucous acini but most of the
acini, however, are mucous.
• Ducts:
– In comparison with other salivary glands, the duct system of the
sublingual gland is some-what different.
– The intercalated ducts are short or absent, and not readily
observed in a given section.
– the non-striated intralobular excretory ducts are more prevalent
in the sublingual glands.
– The interlobular connective tissue septa are also more abundant
in the sublingual than in the parotid and submandibular glands.