Pancreas+salivary Glands

SALIVARY GLANDS AND PANCREAS
Learning Objectives:
 Understand the histology and function of the salivary glands.
 Identify and know the differences between mucous and serous acini and where they are located.
 Know the types of ducts of the major salivary glands and where they are found.
 Identify the basic histology of the pancreas and differentiate endocrine and exocrine both
histologically and functionally.
o Key Words: Acinar cell, acini, mucous cell, serous cell, islet cell, intercalated duct, striated duct,
parotid, submandibular and sublingual glands
I. INTRODUCTION
The salivary glands are involved in the secretion of enzymes that aid in digestion as well as the
moistening of food. The pancreas secretes numerous enzymes that aid in digestion. It also plays
the major role in glucose regulation.
II. SALIVARY GLANDS

Salivary glands are classified according to their function and location, as well as the
predominance of either serous or mucous acini. The major salivary glands are the parotid,
submandibular (submaxillary), and the sublingual. The minor salivary glands are the buccal,
palatine, labial, and lingual.
Parotid gland. Serous acini only; Sublingual gland. Mixed, mostly mucous acini with
serous demilunes.
Left Panel - Submandibular gland. Mixed, serous and mucous acini with serous demilunes capping
many mucous acini; Right Panel - Palatine gland. Mucous glands only.
A. Three types of salivary secretory units are present in these glands. The serous ones contain
amylase. The mucous ones secrete sialomucins, and mixed units contain both serous and mucous
components.
1. Serous acini consist of pear-shaped groups of epithelial cells
surrounded by a distinct basement membrane. The epithelial cells have a dense cytoplasm and a
basal nucleus. The acini have a central lumen into which secretions flow from the epithelial cells.
2. Mucous acini are larger than serous acini. The secretory cells have
an abundant cytoplasm filled with clear mucus. The cells are pyramidal with flattened basal
nuclei.
3. Mixed acini can be characterized by a crescent-shaped formation
of serous cells capping a mucous acinus (serous demilune) or by a mixed pattern of serous and
mucous acini. Serous demilunes are seen typically in the submandibular gland.
Sublingual gland. Mucous acini with serous demilunes.
B. The gland structure consists of a connective tissue stroma with blood vessels, nerves,
lymphatics and ducts. The connective tissue septae divide the glands into lobules. The acini
make up the parenchymal component.
 The duct system transports the saliva from the gland to the oral cavity and modifies its
concentrations of electrolytes. It is composed of different segments.
The first two segments, the intercalated and the striated ducts, are intralobular. They are secretory
ducts. The intercalated duct is the first segment and is lined with squamous or low cuboidal
epithelium. It has an irregular layer of myoepithelial cells. The striated duct has a simple
columnar epithelial lining. It has characteristic striations on the basal side caused by membrane
invaginations and numerous mitochondria. This structure is involved in the transport of water and
electrolytes.
The interlobular ducts are located in the connective tissue of the septae. They are lined initially
by pseudostratified columnar epithelium along with sparse goblet cells. As the diameter enlarges,
the epithelium becomes stratified columnar, and as the duct enters the oral cavity it is lined
distally with nonkeratinized stratified squamous epithelium.
C. The major salivary glands are paired structures. The parotid gland is of the serous type. The
submandibular and sublingual glands are of the mixed type. The submandibular gland has a
predominance of the serous acini and the sublingual gland has a predominance of the mucous
acini. The minor salivary glands are found scattered throughout the oral cavity and are mucous
glands contributing 70% of the total mucus in saliva.
D. Myoepithelial cells (basket cells) are flat and have long cytoplasmic processes that aid in
contraction. They lie between the epithelial cells and the basal lamina of the acini.
E. Secretion of the salivary glands is stimulated by the autonomic nervous system.

 Parasympathetic secretion in response to the taste or smell of food, promotes vasodilatation and
copious watery secretion (“mouth waters”).
 Sympathetic stimulation produces small amount of viscous saliva.
Gland Acini Excretory duct
Parotid serous Stenson’s duct
Submandibular mixed (serous predominate) Wharton’s duct
Sublingual mixed (mucous) empty into floor of
Mouth
III. PANCREAS
In the adult the average pancreas is about 12-15 cm in length and weighs 60 to 140 g.
Histologically, the pancreas has two separate components, exocrine and endocrine glands. The
exocrine portion makes up approximately 80% of the organ, and consists of numerous acini
aggregated into lobules that can be seen grossly. The endocrine portion cannot be discerned
grossly.
The Exocrine Pancreas

 The pancreas has a poorly defined capsule. It is covered by a thin areolar connective
tissue capsule. This capsule gives rise to the connective tissue septae that divide the pancreas into
lobules. Blood vessels, nerves, lymphatics and ducts traverse through the septae. A principal
small artery supplies each lobule.
 Acinar cells constitute the majority of the organ. The cells form rounded or elongated
acini usually at the ends of the intercalated ducts.
 Normal acinar cells are large, pyramidal shaped cells with a single nucleus. The nucleus
lies close to the base of the cells that rests on the basal laminae. The nucleus is round with
clumped chromatin.
 The apical portion of the cell is filled with eosinophilic zymogen granules. The basal
portion is strongly basophilic because the cytoplasm is filled with RER. The cells secrete directly
into acinar lumen though the apical surface. No myoepithelial cells are present.
1. The ducts of the exocrine pancreas

 Centroacinar cells, located in the center of the acinus, with a pale nucleus, form the smallest ducts
of the gland.
 The intercalated ducts are lined by low cuboidal epithelium. The nucleus is ovoid with
inconspicuous nucleoli.
 The intralobular ducts vary in diameter and are lined by simple cuboidal epithelium. A single
rounded nucleus appears to fill each cell.
 Interlobular ducts are larger and are lined by simple columnar epithelium. They are located in the
septae and are invested by a layer of collagenous tissue.
 Two major ducts are the ducts of Santorini and Wirsung. They have tall columnar epithelium with
basal nuclei.
B.
A. Pancreas. Human. x 132. H&E. (H&G Plate 15-2-1). Serous acini only. Note islet of Langerhans below
arrow. B. Pancreas. Monkey. x 540. H&E. (H&G Plate 15-2-3). Higher power showing zymogen granules
in the acinar cells.
2. Pancreatic exocrine secretion

 Merocrine secretion of proenzymes by the acinar cells is regulated by secretin and
cholecystokinin from the enteroendocrine cells of the duodendum and jejunum and nerve
stimulation from the vagus.
 Gastric acid in the intestinal lumen stimulates secretin release. Secretin causes acina and ductal
cells to add water and bicarbonate to fluid, making it alkaline, rich in electrolytes and poor in
enzyme activity. This fluid neutralizes the chyme so that the pancreatic enzymes can function at
an optimal neutral pH range.
 Long-chain fatty acids, gastric acid and some essential amino acids in the gut stimulate the
release of cholecystokinin. This hormone promotes secretion of an enzyme-rich (but less
abundant) fluid.
B. The Endocrine Pancreas

 The endocrine pancreas constitutes 1-2% of the adult pancreas.
 The endocrine cells form scattered aggregates that form the Islets of Langerhans. Each islet is a
lightly stained, rounded group which is a multihormonal micro-organ. A small amount of
connective tissue accompanies the large capillaries that run though each islet.
A. B.
A. Islet of Langerhans. Rounded group of endocrine cells surrounded by serous cells. B. Islet of
Langerhans. Note rich vascularity with red cells in capillaries.

Pancreas+salivary Glands

Uploaded by

Copyright:

Available Formats

Pancreas+salivary Glands

Uploaded by

Document Information

Original Title

Copyright

Available Formats

Share this document

Share or Embed Document

Sharing Options

Did you find this document useful?

Is this content inappropriate?

Copyright:

Available Formats

Pancreas+salivary Glands

Uploaded by

Copyright:

Available Formats

SALIVARY GLANDS AND PANCREAS

II. SALIVARY GLANDS

Sublingual gland. Mucous acini with serous demilunes.

E. Secretion of the salivary glands is stimulated by the autonomic nervous system.

The Exocrine Pancreas

1. The ducts of the exocrine pancreas

2. Pancreatic exocrine secretion

B. The Endocrine Pancreas

You might also like