Page 404 - Anatomy and Physiology of Farm Animals, 8th Edition

Anatomy of the Digestive System / 389

other structures. It is divided into a lesser along the lateral tongue near the floor of
the mouth. Numerous ducts pass directly
omentum, extending from the lesser
VetBooks.ir curvature of the stomach to the liver, and from the gland to open into the floor of the
mouth just ventrolateral to the tongue.
the greater omentum, which is attached to
the greater curvature of the stomach (and With the exception of the horse, the sublin­
the comparable portion of the ruminant gual salivary gland also has a monostomatic
stomach). The greater omentum spreads portion that empties at the sublingual
like an apron from the stomach to cover caruncle on the floor of the mouth by way
most of the ventral aspect of the mass of of a single sublingual duct that runs parallel
intestine. to the mandibular duct.
The salivary glands are classified as
Accessory Digestive Organs serous, mucous, or mixed. Serous glands
secrete a watery clear fluid, as compared
with mucous glands, which secrete mucus,
In addition to the numerous small glands a viscous material that acts as a protective
located in the walls of the stomach and covering for the surface of mucous mem­
intestine, accessory glands include the sali­ branes. A mixed gland produces both
vary glands, the pancreas, and the liver. mucous and serous fluids. The parotid sali­
vary gland secretes primarily serous saliva;
Salivary Glands mandibular and sublingual glands are clas­
sified as mixed glands in domestic farm
The salivary glands of domestic farm animals. Most of the minor salivary glands
animals comprise three pairs of well‐ have a mucous secretion.
defined glands as well as scattered lobules
of salivary tissue (the so‐called minor sali­
vary glands). The chief salivary glands are Pancreas
the parotid, mandibular, and sublingual
(Fig. 20‐18). The minor salivary glands The pancreas is a compound gland that
include labial, buccal, lingual, and palatine has both endocrine and exocrine portions.
glands. The exocrine portion of the pancreas pro­
The parotid salivary gland is located duces sodium bicarbonate and digestive
ventral to the ear in relation to the caudal enzymes, which pass through the pancre­
border of the mandible. In most animals, atic ducts to empty into the duodenum
the parotid salivary duct passes ventrad close to the opening of the bile duct.
and craniad on the medial side of the The endocrine portion of the pancreas
caudal mandible then crosses the cheek consists of isolated groups of pale‐staining
superficially just cranial to the masseter cells scattered throughout the gland. These
muscle. The duct then passes dorsad to areas are called the pancreatic islets (for­
penetrate the mucous membrane of the merly islets of Langerhans). They produce
oral vestibule near the third or fourth the hormones that pass directly into the
maxillary cheek tooth. bloodstream (see Chapter 13), most nota­
The mandibular salivary gland is usu­ bly glucagon and insulin, which are the
ally located ventral to the parotid gland, primary regulators of blood sugar levels.
just caudal to the mandible. The mandibu­ Grossly, the pancreas is an irregularly
lar salivary duct passes forward along the lobulated organ that lies adjacent to the
medial side of the mandible to open ventral proximal duodenum and frequently abuts
to the tongue on the sublingual caruncle, the stomach, the caudal vena cava, and
a small hillock of mucous membrane caudal part of the liver as well. The pan­
located on the floor of the mouth. creas has the appearance of aggregated
The sublingual salivary gland is nodules loosely united to form an elon­
located deep to the oral mucous membrane gated gland lying parallel to the duodenum.