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)

SizenumberDistributionFunction A cellslarge20%Peripheralglucagon B cellssmall75%centerinsulin D cells5% Among A and B cells somatostatin Endocrine portion Other cells PP cells: pancreatic polypeptide G cells: gastrin

A cellsB 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 H 2 O  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 Disse

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  mucosa Simple 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