Stratified squamous epithelium

simple columnar epithelium

Rich in small digestive glands for connective tissue, stomach and intestinal lamina propria

thin layer of smooth muscle

fiber membrane

Serosa

They are surface mucin cells (single-layer columnar epithelium), with an oval nucleus located at the base of the cell, and the top cytoplasm is filled with mucin granules (HE staining is light or even transparent)

Surface mucus cells secrete mucus to cover the epithelium and play an important protective role

fundic glands

Chief cells (pepsin cells)

Parietal cells (oxyntic cells)

It is divided into two layers: inner ring and outer longitudinal layer.

The mucus-bicarbonate barrier exists so that gastric acid does not corrode and digest the stomach wall tissue

(1) Absorption cells

(2) Goblet cells

(3) Paneth cells

(4) Undifferentiated cells

(5) Endocrine cells

It is a dense connective tissue. In addition to a large number of small intestinal glands, it is also rich in lymphocytes, plasma cells, macrophages, eosinophils and mast cells.

There are 1 to 2 thick longitudinal lymphatic capillaries in the connective tissue of the central axis of the villi, called the central chylous duct, which are related to fat absorption.

They are mostly solitary lymph nodes in the duodenum and jejunum, and they are mostly Peyer's lymph nodes in the ileum (especially the lower section).

It is composed of two layers of thin smooth muscle, the inner ring and the outer longitudinal layer.

Most of them are cone-shaped cells with microvilli on the free surface. They sense chemical information such as food and pH in the lumen, thereby releasing certain hormones or transmitters to cause changes in other endocrine activities.

The cells are round or oblate, with the top covered by adjacent cells. The base often extends lateral processes along the basement membrane to contact adjacent cells. This type of cell is mainly affected by mechanical stimulation or other hormones to change its endocrine state.

Each acini is surrounded by a single layer of 40 to 50 cone-shaped acinar cells, with a basement membrane outside, and can secrete a variety of digestive enzymes.

Several smaller flat or cuboidal cells can be seen on the luminal surface of the acinus, called alveolar heart cells.

Including intercalary ducts, intralobular ducts, interlobular ducts, and main ducts.

A watery liquid composed of a variety of digestive enzymes (protozoa) secreted by the acini and bicarbonate-containing electrolytes and water secreted by the ducts.

The sodium bicarbonate can neutralize gastric acid entering the duodenum

Accounting for about 20% of the total number of islet cells, they are mostly distributed around the islets.

A cells secrete glucagon, which can promote liver cells to decompose glycogen into glucose and inhibit glycogen synthesis, causing blood sugar to rise.

Accounting for approximately 75% of the total number of islet cells, most are located in the center of the islet

B cells secrete insulin, which mainly promotes the uptake and utilization of glucose by tissues and cells, and promotes the synthesis of glucose into glycogen or into fat for storage, thereby lowering blood sugar.

Accounting for about 5% of the total number of islet cells, scattered between A and B cells

D cells secrete somatostatin, which directly acts on neighboring cells A, B cells or PP cells in a paracrine manner, inhibiting the secretory activities of these cells.

Very few in number, distributed around cells

There are secretory granules in the cytoplasm, and PP cells secrete pancreatic polypeptide, which can inhibit gastrointestinal motility, pancreatic juice secretion, and gallbladder contraction.

Hepatocytes, accounting for about 90% of the total number of cells in the liver, are polyhedral, with sinusoidal surfaces, bile canaliculi surfaces and hepatocyte surfaces.

There are well-developed microvilli on the sinusoidal surface and bile canaliculi, which expands their surface area. There are structures such as tight junctions, desmosomes, and gap junctions on the liver cell surface.

Liver cell nuclei are large, round, centered, and about 25% are binucleated. The nuclei are rich in euchromatin, lightly stained, and have one to several clear nucleoli. They have the characteristics of a cell structure characterized by strong protein synthesis.

There are also many polyploid cells in liver cells. For example, tetraploid cells in the liver of normal adults account for more than 60%. This may be due to the fact that liver cells maintain active functional activities and vigorous material renewal for a long time, as well as the potential of the liver. Powerful regeneration function

(1) Rough endoplasmic reticulum: can synthesize a variety of important plasma proteins, such as albumin, fibrinogen, prothrombin, lipoproteins, complement, etc.

(2) Smooth endoplasmic reticulum: Involved in the synthesis of bile, lipid metabolism, sugar metabolism, hormone metabolism, as well as the biotransformation and detoxification of drugs, putrefactive products and other substances.

(3) Golgi complex: involved in bile secretion by liver cells

Located between the liver plates, the cavities are large and irregular, anastomosing each other to form a network; the sinusoidal walls are surrounded by endothelial cells, and there are liver macrophages and large granular lymphocytes in the sinusoidal cavities.

(1) Endothelial cells: The cells are flat and thin, with the nucleus containing the part slightly thicker and convex toward the sinus cavity. There is no basement membrane outside the endothelium.

(2) Liver macrophages (Kupffer cells): They are irregular in shape, with a large number of wrinkles and microvilli on the surface, and are attached to the endothelium with many plate-like and filopodia, or pass through endothelial windows and intercellular spaces. Extends into the perisinus space and has deformation and active deformability

(3) Large granular lymphocytes: NK cells unique to the liver

It is a narrow gap between the liver sinusoidal wall and the liver plate. The perisinusoidal space is filled with plasma. The microvilli on the sinusoidal surface of liver cells are soaked in plasma, allowing for full and efficient material exchange.

There are fat-storing cells (hepatic stellate cells) in the perisinusoidal space, with irregular nuclei and many lipid droplets in the cytoplasm.

It is a microscopic tube surrounded by local depressions in the plasma membrane of the bile canaliculi of adjacent hepatocytes.