Digestive glands

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Digestive glands
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General outline

• small digestive glands

• distributed in the wall of digestive tract
• esophageal glands, gastric glands and
• intestine glands

• large digestive glands

• outside the wall of digestive tract
• salivary glands, liver and pancreas

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Large salivary glands

• Include parotid, submandibular and
• sublingual glands
• are compound tubuloacinar glands
• are composed of acini and ducts

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Acinus

• acinar epithelium simple
• cuboidal or pyramidal cells
• myoepithelial cell
• basal membrane

Structure
Serous acini Mucous acini Mixed acini
Be divided into
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Serous acini

• cytoplasma are deep stained
• nucleus are spherical in shape and near
• the base
• secretion is thin, contains salivary amylase
• and a little mucus

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Serous acini and striated duct
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Mucous acini

• cytoplasma are light-blue stained
• nucleus are flattened ovoid shaped and
• close to the base
• secretion is thick contains mucoprotein

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Mucous acini
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Mixed acini

• consist of above two kinds of cells
• demilunes several serous cells are
• attached eccentrically to the mucous acini

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Mixed acini
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Ducts

• Intercalated ducts

diameter thinnest wall simple low cuboidal
epithelium
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• Striated duct (secretory duct)

• wall simple columnar epithelium the nucleus
• is near the cell apex cytoplasm is
• acidpphilic has basal striations
• EM the basal striations created by
• membrane infolding and mitochondia
• reabsorbing sodium and excreting potassium
• transport water and ions

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Intercalated ducts and striated ducts
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• Interlobular duct

Wall pseudostratified epithelium

• Main duct

Near its orifice become stratified squamous
epithelium
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Parotid gland

• pure serous gland
• longer intercalated duct
• secrete 25 of saliva, more salivary
• amylase, less mucus

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Parotid gland
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Submandibular gland

• mixed gland. Serous acini are more than
• mixed or mucous acini
• short intercalated duct, longer striated duct
• secrete 70 of saliva, less salivary amylase,
• more mucus

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Submandibular gland
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Sublingual gland

• mixed gland, mucous and mixed acini
• predominant, more demilune
• without intercalated duct, obscure striated
• duct
• secrete 5 of saliva, most mucus

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Sublingual gland
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Pancreas
Exocrine portion

• the features of the acini

• a single layer of pyramidal serous cells
• surrounded by basal lamina, without
• myoepithelial cells
• centro-acinar cells the epithelial cells of
• intercalated duct penetrating into the
• lumen of the acinus

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• the feature of ducts

• the intercalated duct is long and has branches
• no striated duct
• main duct lined by simple columnar
• epithelium in which a few goblet cells
• and endocrine cells can be seen

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• The functions of exocrine portion

Secret abundant trypsinogen, chymotrypsinogen,
amylase, lipase, sodium bicarbonate and trypsin
inhibitor
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Pancreas
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Pancreas ( show centro-acinar cells and
intercalated ducts)
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Endocrine portion (pancreatic islet)

• rounded clusters of cells embedded within
• exocrine pancreatic tissue
• are divided into three kinds of cells A, B,
• and D cells
• fenestrated capillaries are among the
• cells

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Pancreas (show pancreatic islet)
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Endocrine portion
Size number Distribution Function
A cells large 20 Peripheral glucagon
B cells small 75 center insulin
D cells 5 Among A and B cells somatostatin
PP cells pancreatic polypeptide G cells gastrin
Other cells
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A cells
B cells
D cells
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Liver
Hepatic plates Sinusoid Central vein
Liver lobule
Interlobular arteries Interlobular
veins Interlobular bile ducts
Portal area
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Functions of liver

• bile secretion
• synthesize protein, glycogen, cholesterin
• detoxification and inactivation
• defence
• hemopoiesis

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Human liver
Pork liver
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Liver lobule

• hepatic plates are composed of a single
• layer of hepatocytes arranged in radial
• sinusoid situated between the hepatic
• plates, forming a complex network
• central vein occupies the centre of the
• liver lobule

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Liver lobule
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Hepatic plates
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Hepatic cords and liver sinusoids
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Hepatocytes

• polyhedral in shape, eosinophilic cytoplasm,
• one or two large rounded nuclei with one or 2
• typical nucleoli
• EM Mi, RER, SER, Golgi apparatus,
• lysosomes, microbodies, inclusions

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• Mitochondria

provide the energy for the hepatocytes

• Rough endoplasmic reticulum

synthesize some plasma proteins

• Golgi apparatus

participate in the formation of bile and
lipoprotein
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• Smooth endoplasmic reticulum

• synthesize bile, triglyceride and LDL
• metabolism of the lipid, hormones and
• cholerythrin
• inactivate steroid hormone
• biotransformation of some materials
• detoxification of noxious substances

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• Lysosomes

• actively participate the metabolism of
• hepatocyte and renewal of organelles
• play a role in metabolism and transport of
• cholerythrin
• storage of iron

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• Microbodies

detoxification catalase and peroxidase
reduce the hydrogen peroxide into H2O

• Inclusions

include glycogen, lipid droplets, pigment
etc These contents vary according to physiologic
state of human body
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Bile canaliculi

• between two adjacent hepatocytes
• the membrane of hepatocyte projects to
• the lumen, forming many microvilli
• the cell membranes near the bile canaliculi
• are firmly bound by junctional complexes

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Bile canaliculi
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Liver sinusoid

• spaces between the hepatic plates
• irregular in shape
• composed of only one discontinuous layer of
• fenestrated endothelial cells, no diaphragm,
• no basement membrane
• Kupffer cells are located within the sinusoid
• cavities

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Kuffer cells in liver sinusoid
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Liver sinusoid and space of Disse
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Space of Disse

• separates the endothelium from the
• hepatocytes
• contains some reticular fibers and fat-storing
• cells

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Portal space

• the connective tissue separating the lobules
• including

Interlobular arteries Interlobular
veins Interlobular bile ducts
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Portal spaces
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Blood circulation
portal V.
interlobular V.
(functional vessel)
sinusoids
central V.
hepatic A.
interlobular A.
sublobular V.
(nutrient vessel)
hepatic V.
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Blood vessels of liver
(prepared Chinese ink injection through portal
vein)
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Discharge way of bile
Bile canaliculi
Herings canals
Interlobular bile ducts
Gallbladder
Hepatic duct
Common bile duct
Cystic duct
duodenum
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Gallbladder
Simple columnar Epi. , no Goblet cells Laminar
propria C.T.

• mucosa

• muscle layer composed of an inner circular,
• an outer longitudinal layers of smooth muscle

• adventitia most are fibrosa, some are serosa

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Gallbladder