Page 510 - Atlas of Histology with Functional Correlations

axons. Also present in the taste buds are elongated, supporting sustentacular

cells that are less numerous and not sensory. At the base of each taste bud are the
basal cells that are undifferentiated and serve as stem cells for the other two cell
types.

Lymphoid Aggregations: Tonsils (Palatine,

Pharyngeal, and Lingual)

The tonsils are aggregates of diffuse lymphoid tissue and lymphoid nodules that
are located in the oral pharynx. The palatine tonsils are located on the lateral

walls of the oral part of the pharynx. These tonsils are lined with stratified
squamous nonkeratinized epithelium and exhibit numerous crypts. A connective
tissue capsule separates the tonsils from the adjacent tissue. The pharyngeal
tonsil is a single structure situated in the superior and posterior portions of the

pharynx. It is covered by pseudostratified ciliated epithelium. The lingual tonsils
are located on the dorsal surface of the posterior third of the tongue and are
visible as numerous small bulges composed of massed lymphoid aggregations.
The lingual tonsils are lined with a stratified squamous nonkeratinized

epithelium. Each tonsil is invaginated by the covering epithelium to form crypts,
around which are found lymphatic nodules with germinal centers.

Supplemental micrographic images are available at
www.thePoint.com/Eroschenko13e under Digestive System Part I: Oral
Cavity.

FIGURE 13.5 | Lip (Longitudinal Section)

Thin skin lines the external surface of the lip. The epidermis (11) exhibits

stratified squamous keratinized epithelium with desquamating surface cells
(10). Beneath the epidermis (11) is the dermis (14) with sebaceous glands (2,
12) associated with hair follicles (4, 15) and the simple tubular sweat glands
(16) deeper in the dermis (14). The arrector pili muscles (3, 13) attach to the

hair follicles (4, 15). Also visible in the periphery are blood vessels, an artery
(6a), and a venule (6b). The core of the lip contains striated muscles, the
orbicularis oris (5, 17).

The transition zone (1) between the skin epidermis (11) and the oral

epithelium is a mucocutaneous junction. The internal or oral surface of the lip is

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