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

Large salivary glands

Acinus : acinar epithelium: simple cuboidal or pyramidal cells myoepithelial cell basal membrane Structure: Serous acini Mucous acini Mixed acini Be divided into

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

导管(duct) 闰管：单扁或矮立方；短而细 单柱，胞质嗜酸性，核靠近细胞顶部 基底纵纹（EM：质膜内褶） 转运水和电解质（保钠排钾） Intercalated duct 单柱，胞质嗜酸性，核靠近细胞顶部 基底纵纹（EM：质膜内褶） 转运水和电解质（保钠排钾） 纹状管 Striated duct 小叶间导管：假复柱 总导管：复扁

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)

Endocrine portion PP cells: pancreatic polypeptide G cells: gastrin 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

A cells B cells D cells

Liver Hepatic plates Sinusoid Central vein Liver lobule Interlobular arteries Interlobular veins Interlobular bile ducts Portal area

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

肝血窦 Hepatic sinusoid 分布：位于肝板之间 内皮不连续，有孔无隔膜，吞饮小 泡，无基膜 结构： 功能： 通透性大，有利于肝细胞与血液间 物质交换 枯否细胞 窦周隙： 贮脂细胞、网状纤维 （Disse 隙）

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

肝细胞超微结构

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 central V. （functional vessel) sinusoids central V. hepatic A. interlobular A. sublobular V. (nutrient vessel) hepatic V.

肝的血液循环： 门V 小叶间V 肝血窦 中央V 小叶下V 肝A 小叶间A 肝V 下腔V

Blood vessels of liver (prepared Chinese ink injection through portal vein)

Discharge way of bile: Bile canaliculi Hering’s canals Interlobular bile ducts Gallbladder Hepatic duct Common bile duct Cystic duct duodenum

胆汗排出途径： 肝细胞 胆小管 闰管 小叶间胆管 左、右肝管 胆总管 十二指肠 胆囊管 胆囊

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

Gallbladder

肝细胞超微结构及其相关功能： Mi：供能 RER：合成蛋白质（白蛋白、纤维蛋白原、酶） SER：合成、转运胆汁；糖、脂、类固醇激素 代谢；解毒 Golgi：加工运输蛋白质、分泌胆汁 lysosome ：自噬、异噬、胆红素转运、储存铁 微体：解毒

复习思考： 简答 胰岛外分泌部，胰岛，肝血窦，窦周隙 胆小管，肝细胞邻接面 问答 联系超微结构说明肝细胞的功能