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10.46 Muscular stomach (chicken). Goldner’s Masson 10.47 Cuticle of the muscular stomach (chicken).
trichrome stain (x20). Goldner’s Masson trichrome stain (x40).

Table 10.4 Comparative structure of the avian glandular and muscular stomach.

Compartment Epithelium Glands Muscle Special features
Glandular Simple Superficial and deep Lamina muscularis mucosae Cuboidal epithelium,
stomach columnar tubular glands, deep protrudes between clusters secretes pepsinogen
proprial glands of deep glands, dividing and
extensively lobulated these into distinct lobules; HCl (oxynticopeptic
in the chicken and inner circular layer of muscle cells)
goose, mucous in tunica muscularis is well
secretion; endocrine developed
cells
Muscular Simple Clusters of tubular Wall subdivided into two Together with
stomach columnar glands; secretion forms major and two minor ingested stones (grit),
a rigid grinding plate muscles composed of the cuticle contributes
(cuticle) composed of smooth muscle fibres; to mechanical
a keratin-like complex the inner muscle layer is breakdown of stomach
(koilin); endocrine cells particularly well developed; contents
tendinous centres present
laterally

horizontalis (softer secretions of the simple columnar be divided macroscopically into four separate muscles.
gastric mucosal epithelium) to form a continuous layer of The inner circular layer is usually more developed than
varying thickness. the outer longitudinal layer. The individual muscles are
Biochemically, the cuticle is composed of a keratin-like referred to as the:
carbohydrate-protein complex (koilin). Small stones (grit)
ingested with the food further assist with mechanical grinding. · m. crassus caudodorsalis,
Tela submucosa: The tela submucosa forms an immo- · m. crassus cranioventralis,
bile connection with the connective tissue components of · m. tenuis craniodorsalis and
the lamina propria mucosae (a lamina muscularis mucosae · m. tenuis caudoventralis.
is absent). As a result, the gastric mucosa is tightly anchored
to the overlying layer, the tunica muscularis. The strong m. crassus caudodorsalis and m. crassus
Tunica muscularis: The wall of the muscular layer cranioventralis extend from one tendinous centre (cen-
consists predominantly of smooth muscle tissue that can trum tendineum) to the other, forming the dorsal and

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