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消化管消化管

Digestive tractDigestive tract

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Digestive Tract

I. General structures of digestive tract: 4 layers in its wall.A. Mucosa: Most important and complicated. Embodies the various functions of different tract segments.1. Epithelium: Simple columnar or stratified squamous. May have microvilli.2. Lamina propria: LCT, may contain glands and lymphatic tissue. May protrude together with epithelium into the tract lumen to form villi.

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消化管一般结构

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3. Muscularis mucosa: Inner circular and outer longitudinal layer of smooth muscles.B. Submucosa: LCT containing larger nerve fibers, blood and lymph vessels. May contain submucosal glands. May protrude together with mucosa into the tract lumen to form plicae.C. Muscularis(--externa): Skeletal muscles and/or smooth muscles are arranged into 2~3 layers.D. Adventitia: Serous or fibrous membrane.

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II. Esophagus:A. Mucosa: Non-keratinized stratified squamous epithelium.B. Submucosa: Contains esophageal mucus glands. Mucosa and submucosa protrude together into the lumen, forming 7~10 longitudinal plicae, which disappear and reappear depending upon the passage of food.

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C. Muscularis: Skeletal in upper 1/3, mixed in middle part and smooth muscle fibers in lower 1/3 part. Arranged in inner circular and outer longitudinal layer. D. Adventitia: Fibrous membrane.

食管食管（（ EsophagusEsophagus ））

粘膜肌层粘膜肌层

This is a very advanced carcinoma of the lower one-third of the esophagus. This is a fungating medullary type of tumor which caused obstruction and presented as dysphagia.

"Barrett's esophagus" in which there is gastric -type mucosa above the gastroesophageal junction

贲门腺 ： 粘液性细胞为主，少量壁细胞

分泌粘液和少量溶菌酶 Cardiac gland

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III. Stomach: Organ for digestion. A. Mucosa: Has longitudinal plicae when empty, gastric pits and few lymphatic tissue. 1. Epithelial cells: Mainly composed of surface mucous cells, which are simple columnar with tight junctions among them. Have mucus-containing secretory granules in upper part of cytoplasm. Secrete insoluble mucus containing high content of HCO3

-.

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Mucous-HCO3- barrier: Mucus +

tight junctions, which protects mucosa from being eroded by acid (pH = 0.9~1.5) and enzymes in the lumen of stomach. 2. Lamina propria: CT containing a few smooth muscle fibers, lymphoid tissue and lots of single or branched gastric glands, each of which is divided into a neck and a base portion and opens at gastric pit, and contains 5 types of cells:

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a. chief (zymogenic) cells: predominate in the gland bases. Have basophilic base cytoplasm due to abundant RER, RS, and acidophilic apical cytoplasm containing G and secretory granules. Secrete lipase and inactive pepsinogen.

胃底腺 - 图 (2)

胃底腺 -LM

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b. parietal (oxyntic) cells: present mainly at the upper part of the glands. Larger, each of them contains 1~2 nuclei. Strong acidophilic cytoplasm with abundant MT. The cell membrane invaginations and their surrounding SER constitute the tubulovesicular system (Resting state) ←→ Intracellular canaliculi lined by microvilli (Active state). Contain carbonic anhydrase, which are necessary to produce H+. Secrete hydrochloric acid to turn inactive pepsinogen into active pepsin, and intrinsic factor to protect VitB12.

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c. mucous neck cells: PAS (+). Locate at the neck of the gland. Secrete soluble mucus that lines and protects the epithelium. d. endocrine cells: argyrophilic. Mainly locate at the base of the gland. Belong to DNES. Secrete polypeptide containing hormones that can regulate the function of digestive tract.

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The endocrine cells contain basal secretory granules and can be divided into 2 types: * open type: cells are adjacent to the lumen of the glands. * close type: cells are separated with the lumen of the glands.e. stem cells: mainly locate near the neck of the gland.3. Muscularis mucosa: Inner circular and outer longitudinal layer of smooth muscles.

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B. Submucosa: LCT containing large blood, lymph vessels and nerves.C. Muscularis: Inner oblique layer + middle circular layer + external longitudinal layer of smooth muscles. Between the layers of smooth muscles exist the nerve plexus (intramural ganglia).D. Adventitia: Serous membrane.

幽门腺：

胃小凹深，腺短而弯曲

粘液性细胞为主 , 少量壁细胞 , 内分泌细胞

分泌粘液、溶菌酶及少量蛋白分解酶

Pyloric gland

Chronic atrophic gastritis

Intestinal metaplasia

肠上皮化生：

　胃粘膜上皮由肠型腺上皮取代，出现吸收细胞，杯状细胞和潘氏细胞。

Helicobacter.pylori

幽门螺杆菌 3.5×0.5um 大小

微弯曲棒状

革兰氏阴性杆菌

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IV. Small intestine: Organ for digestion and absorption. The inner surface of small intestine can be greatly enlarged by:* plicae circulares: made up of mucosa and submucosa. X 3.* villi: made up of epithelium and lamina propria. X 10.* microvilli: associated only with the epithelium. X 20.

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A. Jejunum:1. Mucosa: a. epithelium: composed of

5 types of cells.* absorptive cells: simple

columnar and most abundant. Cells have obscure cell boundaries and distinct basal nuclei containing clear nucleoli. Numerous microvilli (striated border) are covered by cell coats (glycocalyx) containing enzymes. Rich in SER, MT and cell junctions.

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In upper part of jejunum, the absorptive cells can secrete enterokinase, which will activate the enzymes secreted by pancreas.Function of absorptive cells: Absorption.

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* goblet cells: secrete mucus.* endocrine cells and stem cells: structures and functions are similar to that in stomach.* Paneth’s cells: exist in the bottoms of intestinal glands.b. lamina propria: CT containing isolated lymphatic nodules.* protrudes into the lumen together with epithelium to form finger-like villi.

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Villi are covered by epithelium and contain fenestrated Cap network (the primary Cap of portal circulation) to transport glucose and amino acids, a few single smooth cells and immune cells. The lymph vessels in villi are known as central lacteals, which will transport lipid.

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* accommodates the small intestinal glands, which are derived from the epithelium invaginations and have similar cell compositions to that of epithelium.* Paneth’s cells: situate at the bottom of glands, with acidophilic secretory granules in their apex of cytoplasm and rich RER in basal cytoplasm. Secrete Zn2+ and lysozymes for digesting bacteria, and play an important role in controlling the intestinal flora.

十二指肠十二指肠 回肠回肠空肠空肠

小肠 小肠 small intestinesmall intestine

十二指肠腺十二指肠腺（（ duodenal glandduodenal gland ））

空肠空肠（（ jejunumjejunum ））

回肠回肠（（ ileumileum ））

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c. muscularis mucosa: inner circular and outer longitudinal layer of smooth muscles.2. Submucosa: LCT containing large blood, lymph vessels and nerves. Contains isolated lymphoid nodules.3. Muscularis: Inner circular and outer longitudinal layer of smooth muscles. The nerve plexus (intramural ganglia) exist between the 2 layers, responsible for intestine wring.4. Adventitia: Serous membrane.

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B. Duodenum: Has similar structures to that of jejunum except that:1. Absorptive cells in epithelium secrete enterokinase.2. In its submucosa exist the duodenal glands that secrete basic mucus containing epidermal growth factor (EGF).3. Villi are leaf-shaped. Fibrous membrane exists behind the duodenum.

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C. Ileum: Has similar structures to that of jejunum except that:1. In mucosa and submucosa exist the aggregated lymphoid nodules known as Peyer’s patches. 2. Microfold cells (M cells) exist in the epithelium projection that covers the Peyer’s patches, where no villus and gland can be found.

大肠大肠

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大肠• 盲肠 结肠 直肠

• 阑尾

• 肛管

无 绒毛 潘氏细胞 环形皱襞

有 大肠腺 结肠带 脂肪垂

腔小不规则，腺短少淋巴组织极丰富粘膜肌很不完整上皮骤变丰富的静脉丛

括约肌

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大肠图

结肠结肠 （（ ileumileum ））

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部分结肠粘膜

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阑尾阑尾•无绒毛无绒毛 ,, 肠腺少肠腺少 ..•固有层固有层 :: 大量大量 LTLT..•浆膜浆膜 ..

直肠－肛门交界直肠－肛门交界（（ rectum-annus juncturerectum-annus juncture ））

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八、消化管粘膜免疫功能

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分泌性免疫系统：消化管识别抗原、产生抗体并排泄到管腔内的结构和功能构成机体的第一道防线 。

B 细胞→浆细胞→ IgA→ 分泌片→ S IgA → 局部抑制细菌和病毒。

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胃肠道内分泌细胞 概念：散布在胃肠道上皮和腺体内的分泌肽

类激素的细胞（属 APUD 系统） 结构特征：细胞基部有分泌颗粒

颗粒具嗜铬性或嗜银性 分类：开放型和闭合型 作用方式： ①内分泌作用

② 神经递质作用

③ 旁分泌作用

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需银染才能分清，又称嗜银细胞或基底颗粒细胞。分•开放型：呈锥体型，有微绒毛伸入肠腔， 感受刺激分泌 激素。• 闭合型：呈椭圆形，顶部被相邻细胞覆盖，感受局部环

境变化而分泌激素。

胃肠内分泌细胞

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肠上皮内的微皱褶细胞（ M 细胞），游离面有短小的微绒毛和微皱褶，基底面的细胞膜内陷形成凹腔，腔内有 2-10 个淋巴细胞

消化管的分泌免疫系统

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M cells are specialized antigen presenting cells that are derived from epithelial cells. M cell has incomplete basal lamina and large basal invagination containing macrophages and lymphocytes, which mainly secrete IgA after activation.IgA will combine with secretory protein produced by epithelium to form SIgA, an antibody released to inner surface of intestine to against antigens.

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M 细胞（微皱褶细胞） 分布： 集合淋巴小结表面上皮细胞间

结构：

表面有微皱褶和微绒毛

钟罩状，腔内含 LC 和 Mφ

胞质少，薄膜状，大量吞饮小泡、线粒体

与吸收细胞间有细胞连接

功能：摄取肠腔内的抗原，并传递给小室内的

淋巴细胞，以引起消化道粘膜的免疫反应

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细胞

M

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M 细胞

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名称名称 食管食管 胃胃 小肠小肠 大肠大肠粘膜粘膜表面表面

胃小凹胃小凹 绒毛绒毛

上皮上皮 复层扁平复层扁平 单层柱单层柱状状

单层柱单层柱状状

纹状缘纹状缘杯状杯状 CC

单层柱单层柱状状

杯状杯状 CC多多

消化管粘膜层比较 （消化管粘膜层比较 （ 11 ））

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食管食管 胃胃 小肠小肠 大肠大肠固固有有层层

无腺体无腺体 胃腺胃腺 小肠腺小肠腺 大肠腺大肠腺

无无 LL 小结小结 无无 LL 小结小结 LL 小结小结 LL 小结小结多多

乳糜管乳糜管

消化管粘膜层比较 （消化管粘膜层比较 （ 22 ））

胃底腺胃底腺 :: 主主 ,, 壁壁 ,, 颈粘液颈粘液 ,, 内分泌内分泌 ,, 干干C.C.小肠腺小肠腺 :: 吸收吸收 ,, 杯状杯状 ,, 潘氏潘氏 ,, 内分泌内分泌 ,, 干干C.C.大肠腺大肠腺 :: 吸收吸收 ,, 杯状杯状 ,, 内分泌内分泌 ,, 干干 C.C.

复习思考题简答：皱襞，绒毛，纹状缘，中央乳糜

管，小肠腺，微皱褶细胞

问答： 1 、胃底腺壁细胞的结构与功能

2 、胃底腺主细胞的结构与功能

3 、试述与小肠吸收和分泌有关的

结构基础