858
UNIT 4
Maintenance of the Body
23
Homeostatic Imbalance
23.3
Mumps
, a common children’s disease, is an inflammation of the
parotid glands caused by the mumps virus (
myxovirus
), which
spreads from person to person in saliva. If you check the loca-
tion of the parotid glands in Figure 23.9a, you can understand
why people with mumps complain that it hurts to open their
mouth or chew. Other signs and symptoms include moderate
fever and pain when swallowing acid foods (pickles, grapefruit
juice, etc.). Mumps in adult males carries a 25% risk of infecting
the testes too, leading to sterility.
About the size of a walnut, the
submandibular gland
lies
along the medial aspect of the mandibular body. Its duct runs
beneath the mucosa of the oral cavity floor and opens at the
base of the lingual frenulum (see Figure 23.7b). Te small,
almond-shaped
sublingual gland
lies anterior to the sub-
mandibular gland under the tongue and opens via 10–20 ducts
into the floor of the mouth (Figure 23.9a).
Te salivary glands are composed of two types of secretory
cells: serous and mucous (Figure 23.9b).
Serous cells
produce
a watery secretion containing enzymes, ions, and a tiny bit of
mucin, whereas
mucous cells
produce
mucus
, a stringy, viscous
solution. Te parotid and submandibular glands contain mostly
serous cells. Buccal glands have approximately equal numbers
of serous and mucous cells. Te sublingual glands contain
mostly mucous cells.
The Salivary Glands
A number of glands associated with the oral cavity secrete
sa-
liva
. Saliva:
Cleanses the mouth
Dissolves food chemicals so they can be tasted
Moistens food and helps compact it into a bolus
Contains enzymes that begin the chemical breakdown of
starchy foods
Most saliva is produced by the
major
or
extrinsic salivary
glands
that lie outside the oral cavity and empty their secretions
into it.
Minor
or
intrinsic salivary glands
(buccal glands and
others) scattered throughout the oral cavity mucosa augment
the output slightly.
Te major salivary glands are paired compound tubuloal-
veolar glands that develop from the oral mucosa and remain
connected to it by ducts
(Figure 23.9a)
. Te large, roughly tri-
angular
parotid gland
(pah-rot
9
id;
par
5
near,
otid
5
the ear)
lies anterior to the ear between the masseter muscle and the
skin. Its prominent duct parallels the zygomatic arch, pierces
the buccinator muscle, and opens into the vestibule next to the
second upper molar.
Branches of the facial nerve run through the parotid gland
on their way to the muscles of facial expression. For this reason,
surgery on this gland can result in facial paralysis.
Teeth
Ducts of
sublingual
gland
Sublingual
gland
Submandibular
duct
Posterior belly of
digastric muscle
Parotid duct
Masseter muscle
Body of mandible
(cut)
Parotid
gland
Tongue
Submandibular
gland
(a)
Frenulum
of tongue
Mylohyoid
muscle (cut)
Anterior belly of
digastric muscle
Mucous cells
(b)
Serous cells
forming demilunes
Figure 23.9
The salivary glands.
(a)
The parotid, submandibular, and sublingual glands
associated with the left aspect of the oral cavity.
(b)
Photomicrograph of the sublingual gland
(150
3
), which is a mixed salivary gland. Mucus-producing cells stain light blue and serous-
secreting units stain purple. The serous cells sometimes form demilunes around the bases of the
mucous cells.
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