Digestive glands

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

Large salivary glands

Include parotid, submandibular and

sublingual glands

are compound tubuloacinar glands

are composed of acini and ducts

Acinus :

acinar epithelium: simple

cuboidal or pyramidal cells myoepithelial cell basal membrane

Structure:

Be divided into

Serous acini

Mucous acini

Mixed acini

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

Serous acini and striated duct

Mucous acini

cytoplasma are light-blue stained

nucleus are flattened ovoid shaped and

close to the base

secretion is thick; contains mucoprotein

Mucous acini

Mixed acini

consist of above two kinds of cells

demilunes: several serous cells are

attached eccentrically to the mucous acini

Mixed acini

Ducts:

Intercalated ducts

diameter: thinnest

wall: simple low cuboidal epithelium

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

Intercalated ducts and striated ducts

Interlobular duct

Wall: pseudostratified epithelium

Main duct

Near its orifice become stratified

squamous epithelium

Parotid gland

pure serous gland

longer intercalated duct

secrete 25% of saliva, more salivary

amylase, less mucus

Parotid gland

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

Submandibular gland

Sublingual gland

mixed gland, mucous and mixed acini

predominant, more demilune

without intercalated duct, obscure striated

duct

secrete 5% of saliva, most mucus

Sublingual gland

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

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

The functions of exocrine portion

Secret abundant trypsinogen,

chymotrypsinogen, amylase, lipase,

sodium bicarbonate and trypsin inhibitor

Pancreas

Pancreas ( show centro-acinar cells and intercalated ducts)

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

Pancreas (show pancreatic islet)

Size number Distribution Function

A cells large 20% Peripheral glucagon

B cells small 75% center insulin

D cells 5%Among A

and B cellssomatostatin

Endocrine portion

Other cellsPP cells: pancreatic polypeptide

G cells: gastrin

A cells B cells

D cells

Liver

Liver lobule

Portal area

Hepatic plates

Sinusoid

Central vein

Interlobular arteries

Interlobular veins

Interlobular bile ducts

Functions of liver:

bile secretion

synthesize: protein, glycogen, cholesterin

detoxification and inactivation

defence

hemopoiesis

Human liver

Pork liver

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

Liver lobule

Hepatic plates

Hepatic cords and liver sinusoids

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

Mitochondria

provide the energy for the hepatocytes

Rough endoplasmic reticulum

synthesize some plasma proteins

Golgi apparatus

participate in the formation of bile and lipoprotein

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

Lysosomes

actively participate the metabolism of

hepatocyte and renewal of organelles

play a role in metabolism and transport of

cholerythrin

storage of iron

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

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

Bile canaliculi

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

Kuffer cells in liver sinusoid

Liver sinusoid and space of D

isse

Space of Disse

separates the endothelium from the

hepatocytes

contains some reticular fibers and fat-storing

cells

Portal space:

the connective tissue separating the lobules

including

Interlobular arteries

Interlobular veins

Interlobular bile ducts

Portal spaces

Blood circulation:

portal V. interlobular V.

sinusoids

hepatic A. interlobular A.

central V.

sublobular V.

hepatic V.

（ functional vessel)

(nutrient vessel)

Blood vessels of liver

(prepared Chinese ink injection through portal vein)

Discharge way of bile:

Bile canaliculi

Hering’s canals

Interlobular bile ducts

Hepatic duct

Common bile duct

Gallbladder

Cystic duct

duodenum

Gallbladder

mucosaSimple columnar Epi. , no Goblet cells

Laminar propria: C.T.

muscle layer: composed of an inner circular,

an outer longitudinal layers of smooth muscle

adventitia: most are fibrosa, some are serosa

Gallbladder