The Digestive Glands

The Digestive System

Exocrine gland---with duct Constituents of multicellular gland: secretory portion: tubular,acinar or tubuloacinar gland duct: passage of secretions

Exocrine gland---without duct

Exocrine gland

Salivary gland Acinus: mucous acinus, serous acinus ,mixed acinus Duct:

intercalated duct,striated duct,interlobular duct and common duct Serous acinus

Mucous acinus

Cell type

Serous cell

Mucous cell

Cytoplasm

Deep stained

Light-blue stained

Nucleus

Spherical,near the base

spindle,near the base

Secretions

Protein

Mucoprotein (mucus)

Salivary gland

Serous acini

Mucous acini

Mixed acini and semilune Semilune: several serous cells arranged like half-moon in the mixed acinus

Salivary glands 1. components: parotid gland,submandibular gland and sublingual gland,etc. 2. function: secreting saliva.

The characteristics of 3 pairs of salivary glands Parotid gland

Submandibular gland

Acini

Pure serous gland

Mixed gland, More serous acini

Ducts

Long I.D.

Short I.D., Long S.D.

Secretion

25% saliva More salivary amylase, less mucus

70% saliva Less salivary amylase, more mucus

Sublingual gland Mixed gland,more mixed and mucous acini Without I.D.

5% saliva Most mucus

Parotid gland---pure serous gland

Submandibular gland---mixed gland

Sublingual gland---mixed gland

Pancreas Parenchyma: exocrine portion: pancreatic secretions involved in food-digestion. endocrine portion(pancreas islet): secreting hormones

1. Exocrine portion

acini

ducts

Consists of serous cells surrounded by basal lamina ， Without myoepithelial cells, With several centro-acinar cells in acinus cavity. Long I.D. ,no S.D.

Exocrine portion of pancreas

Exocrine portion of pancreas

Rate(%)

2. Endocrine portion (pancreas islet) A cell

B cell

D cell

PP cell

20%

70%

5%

5%

Somatostatin—

Pancreas polypeptide

Distribution Periphery Secretion

Center

Glucagon-- Insulin-Increase blood glucose levels blood glucose levels

Decrease Inhibit the secretion blood glucose of other cells levels

Diabetes: absence or inadequate amounts of insulin.

The largest digestive gland. The C.T.sends the septa into the parenchyma, separating the hepatic lobules. The portal area is present at the corner of the lobules.

Classic hepatic lobule It is a structural unit of liver. Components Hepatic plates: a single layer of hepatocytes arranged in radial. Sinusoids: between hepatic plates and anastomose with each other.

Central vein: occupies the centre of the liver lobule.

hepatocyte 3 functional surfaces:sinusoidal.., canalicular.., intercellular.. LM: Profile:large,polyhedral in shape. Cytoplasm:rich in Mitochondria, Golgi complex, SER,RER, lipid droplets, glycogen,etc. Nucleus: large,central,lightly stained, with obvious nuceulus. EM: numerous microvilli protruding into sinusoids and bile canaliculi.

Function of hepatocyte 1.Bile secretion 2.Synthesis and storage 3.Detoxification and inactivation 4.Defence :related to Kuffer cell 5.Hemopoiesis

Bile canaliculus It is a small canal formed by opposed grooves In the surface of adjacent hepatocytes.

Bile canaliculi

Sinusoid

Kuffer cell : macrophage in sinusoid

Space of Disse

ace between hepatocytes d endothelium. rovilli of hepatocytes trude into it, which hance the exchages materials. ring fat cells :in space Disse.responsible for storage of Vit.A and duction of fibers.

Portal area （ portal canals ） portal triad: Interlobular arteries

Hepatic artery

Interlobular veins

Portal vein

Interlobular bile ducts

Common bile duct

Hepatic circulation Common bile duct

Interlobular bile ducts

Portal vein

Interlobular vein

Bile canaliculi

sinusoids Hepatic artery

Interlobular artery

Hepatic vein

vein

Hepatic hilum

Portal area

Central vein

Hepatic lobule

Key points 1. The structure and function of pancreas. (exocrine portion and endocrine portion),the cellular components of pancreas islet and their function. 2.The definition of hepatic lobule and portal area.sinusoid ,space of Disse,Kuffer cell; 3.The formation of bile canaliculi.