Download Salivary glands

Salivary glands
It is special tissue of epithelium originated from oral ectoderm and produce saliva which is a mixture
of serous and mucous fluids produced by salivary glands.
Functions of saliva:
1-lubrication and moisting the alimentary canal to help in:
A-swallowing of food.
B-cleaning the mouth.
C-keeping the mouth moist .
D-it is
important for taste.
2-secreting enzymes like: amylase, lipase and in pig secret the ptyalin which is concern primarily in
hydrolysis of starch.
3-production of hormones like protein, epidermal growth hormone and nerve growth hormone.
4-it has special function in fur-bearing animals like cat and rat by hitting it with saliva, in response to
heat, because it is lead some cool as sweating.
5-perform defense mechanism as in snake (venom glands), modified buccal glands.
6-in birds help in holding the nest.
Classifications of salivary glands:
1-According to size:
A-major salivary glands: large masses of
glandular
tissue
include:
parotid,
mandibular and sublingual glands.
B-minor
salivary
glands:
small
seromucous units, presents in the sub
mucosa of the oral cavity, they named
according to location (labial, buccal,
lingual and palatine).
2-According to the number of excretory
ducts:
A-monostomatic: This has only one excretory duct (parotid, mandibular)
B-polystomatic: which has large number of excretory ducts e.g.: sublingual, all the minor salivary
glands.
♣The buccal glands divided into three types in ox and horse:
1-dorsal buccal glands: found dorsal to the massetric parts of buccal muscle extend to the angle of
mouth.
2-ventral buccal glands: found under labial muscle and buccal part of buccinators muscle.
3-middle buccal gland found under buccinators muscle.
Parotid salivary glands: is lobulated and easy visible to the eye, the color of it depend on parotid
function and amount of blood found in it. The location: this gland fills the retromandibular fossa
(which depression caudal to the ramus of mandible and ventral to the wing of the atlas), the gland is
contact dorsally with the base of the ear, ventrally it is extend into the neck into the intermandibular
space, the lateral surface of it is covered by parotid fascia and parotid auriculars muscle, medially it
contact with the branches of common carotid artery, jugular vein, hyoid bone, muscle of hyoid bone,
branches of facial nerve and trigeminal nerve, in horse only, the middle surface of parotid gland
contact with guttural pouch and occiptomandibular part of digastrics muscle.
Comparative
In horse: it is the largest salivary gland, located below the ear and between the ramus of mandible
and the wing of atlas, the shape is quadrilateral, it has two surface, two borders, base and apex. The
dorsal end directly towards the base of ear and the ventral end is wider then dorsal end, occupied the
angle between the lingofacial trunk and jugular vein, it has one excretory duct which is passes at the
medial surface of the ramus of the mandibular and at the vasicular grooves, it is accompanied with
the facial vein and artery and opens into the buccal vestibular at the 3rd upper cheek tooth by
papillae.
In ox: It is smaller then mandibular, located in the masseter muscle along the ramus of the mandible.
The shape is long, narrow triangular. The thicker end of the gland directed toward ear while the
ventral end extends to the angle of mandible and partly covered the mandibular salivary gland. The
duct passes on the medial of the ventral border of mandible like in the horse and open at the 2nd
molar or 5th cheek teeth.
In sheep: It is larger then mandibular salivary gland, it is quadrilateral shape, the duct runs across
the lateral surface of the masseter muscle and open at the 4th upper cheek tooth or 1st molar tooth.
In dog: It is smaller then mandibular, located in the parotid region, the shape is small irregular
triangle. The dorsal border have deep notch surround the external ear. The duct passes across the
masseter muscle and open at the third upper cheek tooth.
2-Mandibular salivary gland: is also lobulated gland, extend from the atlantal fossa to the hyoid
bone so that is covered partly by the parotid salivary gland and lower jaw, mandibular salivary gland
duct is formed by the union of small radicles which passes along the concave border and passes
rostrally between mylohyoidus and hyoglosseus muscle and passse medially to the sublingual
salivary gland. It opens in the sublingual caruncle on the floor of the oral cavity.
sublingual caruncle: the mucosal elevation on the floor of the oral cavity , under the tongue just
caudal to the incisors.
Comparative:
In horse: It is smaller then parotid salivary gland, it is located below the parotid salivary gland in the
atlantal fosse, the shape is long and narrow and curved, has two surfaces, two borders and two
extremities. It reach to the base of hyoid bone rostrally, the duct is formed by union of small radicals
and pass cranially along the medial surface of the body of the mandible and open at the level of the
canine by flattened papillae called sublingual caruncle.
In sheep and ox: It is larger then parotid salivary gland in ox and smaller then parotid salivary gland
in sheep. Located under the curved angle of the mandible and extend from the wing of the atlas into
the intermandibular space. The shape is curved shape. The duct passes along the medial surface of
the mandible like in horse.
In dog: It is larger then parotid salivary gland. Located under the parotid salivary gland at the
atlantic fosse. The shape is rounded in shape or oval, the duct pass on the medial surface of mandible
open at the sublingual caruncle near the frenulum lingual.
In camels: Small gland located in the retromandibular fossa. It have oval in shape , constriction in
the middle. The duct has mandibular duct open in front of frenulum lingual.
3-Sublingual salivary gland: is located under the mucosa of the lateral sublingual fold and to the
lateral surface of the tongue; it is divided into two types of glands:
1-gland which has only one excretory duct called monostomatic.
2-gland which has numerous grooves of excretory duct called polystomatic.
Comparative:
In horse: Consist of loose of small lobules. It has only one gland in each side of the tongue. It has
polystomatic sublingual salivary gland only. Locate under the mucous membrane of the lateral
surface of the tongue. The shape is thin flattened tape extend from the 4 th lower cheek tooth to the
incisive symphysis. The duct is polystomatic type have about 30 minor sublingual orifice.
In ruminant: They are two types:
1-polystomatic: locate under the mucous membrane of the lateral surface of tongue extend from the
incisive bone to the palatoglossal arch. The shape, thin layer lobulated yellowish gland. The duct
opens in row of microscopic orifices in the side of sublingual fold.
2-Monostomatic: locate ventral to the cranial part of the polystomatic salivary glands, the shape is
thin short gland, the duct has one duct accompanied with the mandibular salivary gland duct to the
sublingual caruncle at the level of canines.
In dog: Have two types of glands:
1-polystomatic or cranial part: locate on the lateral surfaces of the tongue under the mucous
membrane; the shape is thin layer of glandular tissue. The duct has about 8-12 orifices open at the
side of tongue.
2-Monostomatic or caudal part: locate under the mucous membrane caudal to the polystomatic part.
The shape, thin layer and the duct one duct accompanied with mandibular duct to the sublingual
caruncles.
In camel: has only polystomatic sublingual salivary gland like in horse, locate under the mucous
membrane of the lateral surface of the tongue. The shape is thin tape of gland the duct has 24 orifice.