Page 219 - Veterinary Histology of Domestic Mammals and Birds, 5th Edition

Digestive system (apparatus digestorius) 201

In carnivores a subglandular layer (stratum subglandu- ticulum ventriculi and half of the body of the stomach
VetBooks.ir lare) may be observed. This layer has two components: an (Figure 10.29).
The cardiac glands are typically branched and heavily
inner stratum granulosum, located at the base of tubular
glands containing mainly lymphocytes and plasma cells, coiled tubular glands that empty via a short ‘neck’ into
and an outer stratum compactum, a dense layer rich in the base of the gastric pits. The terminal portion of the
collagen fibres located adjacent to the lamina muscularis glands is expanded. The glandular epithelium is cuboidal
mucosae (Figure 10.31). to columnar and produces an alkaline mucous secre-
The lamina muscularis mucosae is relatively promi- tion that also contains the enzyme lysozyme. Parietal
nent in domestic mammals. Individual muscle fibre bundles cells (dogs) and chief cells (pigs) are sometimes present
follow a criss-crossing spiral path, forming a contractile within the epithelium. In addition to these exocrine glan-
system that manifests as two to three distinguishable lay- dular cells, the cardiac gland region of the stomach of
ers. This muscle layer contributes to the folding of the domestic mammals contains endocrine glandular cells
mucosa and supports gastric emptying. that can be identified using silver staining and immuno-
The stomach has a typical tela submucosa containing histocytochemical techniques. These cells form part of
vessels, nerves, adipose tissue and localised accumulations the gastrointestinal endocrine system. Their secretory
of lymphatic tissue. The tela submucosa permits move- product, including serotonin, somatostatin and endor-
ment of the layers of the stomach wall with respect to one phins, passes into the capillary network of the stomach
another. It conforms to the shape of the gastric wall, as wall.
determined by its degree of contraction, thus contributing
to the topography of the mucosal surface. PROPER GASTRIC (FUNDIC) GLANDS
The tunica muscularis consists of an inner circular and Proper gastric (fundic) glands occur over approximately
an outer longitudinal layer of smooth muscle. The passage two thirds of the gastric mucosa in carnivores, in a small
of muscle fibres within these layers varies with region and region near the greater curvature in pigs and across most
species, due to the presence of obliquely oriented fibre of the body of the stomach in horses. While this portion
bundles (fibrae obliquae). Towards the pylorus, the inner of the glandular mucosa is referred to as the proper gastric
circular muscle layer thickens to form the m. sphincter gland (fundic) region, it only includes the fundus in carni-
pylori. In the pig and ox, the thickened muscle protrudes vores (Figure 10.29).
into the lumen as the torus pyloricus. The oblique muscle The proper gastric glands are tightly packed and are
fibres form a loop (ansa cardiaca) at the cardia of the stom- longer and less branched than cardiac glands (Figures 10.31
ach, contributing to the m. sphincter cardiae (particularly and 10.32). They extend through the lamina propria to the
well developed in the horse). The oblique fibres also form lamina muscularis, surrounded by connective tissue, ves-
the muscular foundation of the lips of the gastric groove sels, nerves, smooth muscle cells and cellular infiltrates.
(prominent in pigs and, particularly so, in ruminants; refer Several glands empty via a common isthmus into the
to Veterinary Anatomy of Domestic Mammals: Textbook and gastric pits.
Colour Atlas). The outermost layer of the stomach com- The proper gastric glands are composed of three
prises a tunica serosa. regions characterised by structurally and functionally dis-
The tubular gastric glands in the tunica mucosa vary tinct cell types:
in structure and exhibit species-related differences in their
regional distribution. Three types of glands are recognised: · isthmus: isthmus cells (epitheliocytus nondifferen-
tiatus),
· cardiac glands (glandulae cardiacae), · neck (cervix): neck cells (mucocytus cervicalis),
· proper gastric (fundic) glands (glandulae gastricae · body and fundus (pars principalis):
propriae) and − chief cells (exocrinocytus principalis),
· pyloric glands (glandulae pyloricae). − parietal cells (exocrinocytus parietalis) and
− endocrine cells (endocrinocytus gastrointestinalis).
CARDIAC GLANDS
The zone containing the cardiac glands is referred to as isthmus
the cardiac gland region (pars cardiaca) of the stom- The isthmus is the portion of the gland located in the gas-
ach (Figure 10.29). In carnivores and ruminants, the tric pits from which the gland itself develops. Its typically
cardiac glands are restricted to an annular zone at the low cuboidal epithelium is continuous with the epithe-

entrance to the stomach (abomasum in ruminants). In lial lining of the gastric pits. The cells increase in height
the horse, strips of mucosa containing cardiac glands adjoin throughout this transition. The cells of the isthmus are
the saccus caecus. Cardiac glands extend over a larger daughter cells of the mucous neck cells and are usually not
region of the mucosa in pigs, incorporating the diver- fully differentiated (epitheliocyti nondifferentiati).

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