Small Intestine Lecture Notes - L4-Small intestine Team 443 PDF

Small intestine Color index: -Main text -important -female slides -male slides -Dr.note -Extra Editing File [ Gastrointestinal & Nutrition Block | Histology ] Objectives At the end of this lecture, you should be able to answer the following (objectives): describe the microscopic structure of the...

Small intestine Color index: -Main text -important -female slides -male slides -Dr.note -Extra Editing File [ Gastrointestinal & Nutrition Block | Histology ] Objectives At the end of this lecture, you should be able to answer the following (objectives): describe the microscopic structure of the three regions of the small intestine: ● Duodenum. ● Jejunum. ● Ileum. Table of contents: Characteristic of the small intestine mucosa Regional differences of Small intestine EE (DNES) Cells Duodenum Layers This lecture was presented by: Dr. Aly Mohamed Prof. Raeesa Abdultawab Small intestine To increase surface area, the mucosa has: ● Plicae circulares (circular folds): Permanent folds of the mucosa and submucosa. ● Villi (Stomach has rugae to increase the capacity for storage while small intestine has folds to increase the surface area for absorption,it is a fixed structure ). like roots, Villi is ONLY found in small extra intestines (NOT stomach or colon) ● Intestinal crypts (gland) (crypts of Lieberkühn). absorptive cells ● Microvilli (Brush border) mini villi present only in the small intestine and the proximal tubules of the kidney Regional differences of Small intestine Duodenum Jejunum - Its submucosa has Brunner’s glands. - Has neither Brunner’s glands nor Peyer’s patches. - It is invested by serosa in 1st and 3rd parts or adventitia in 2nd part. -It is invested by serosa. Brunner’s glands. Ileum Its lamina propria, opposite the attachment of the mesentery Has lymphoid nodules (Peyer's patches with Mucosal origin) that extend to the submucosa - -Ileum is invested by serosa. Peyer’s patches Inner Duodenum Layers Mucosa Outer Submucosa Shows villi and crypts A- Epithelium: simple columnar epithelium absorptive cell with brush border with goblet cells. B- Lamina propria: Loose areolar C.T. C- Muscularis mucosae: 2 layers of smooth muscle cells. ● Connective tissue containing blood vessels & nerves. ● Contains Brunner’s glands (secrete mucus) I will not bring it as ( brunner’s glands are found in duodenum only, you have to know which layer EXACTLY Muscularis Externa 2 smooth muscle layers: ● Inner circular layer. ● Outer longitudinal layer. Serosa / Adventitia Duodenum is invested by a serosa or adventitia Mucosa of Duodenum Intestinal villi Cells Covering the Villi MCQ What are the cells that cover the villi? • Each Villus is a finger-like projection of small intestinal mucosa and it is formed of: 1- Central core of loose areolar C.T. containing: • Lymphocytes • Plasma cells. • Fibroblasts. • Smooth muscle cells. Comes from Muscularis mucosae• Capillary loops. • Lacteal (blindly ending lymphatic channels) the majority of fat goes through it 2- Villus-covering epithelium. • Surface columnar absorptive cells: - They have brush border (microvilli). - They are covered with thick glycocalx that has digestive enzymes. - They have Junction complex ’more than one’(tight, adhering and desmosome junctions) • Goblet cells: Increase toward the ileum. start to appear in duodenum and continue to increase in number till the end of git • Enteroendocrine (EE) cells (DNES cells). • Simple tubular glands that open between villi. Intestinal glands (crypts) • Composed of 5 cell types: 1. Simple Columnar absorptive cells. 2. Goblet cells: secrete mucus. 3. Enteroendocrine (EE) (DNES) cells: secrete hormones. 4. Paneth cells: secrete Lysozyme (antibacterial) are found in the base of the crypts. present only in small intestine making it sterile 5. Stem cells: are regenerative cells. are found in the base of the crypts. Intestinal villi Cells covering the villi M cell microvilli Intestinal glands (crypts) EE (DNES) Cells EC cells: • secrete endorphin and serotonin. S cells: • secrete secretin. D (delta) cells: • secrete somatostatin A (alpha) cells: • Mo cells: secrete glucagon. (found in liver ) • secrete motilin M Cells (Microfold cells) They are mainly found within the intestinal epithelium overlying lymphatic nodules of lamina propria. • Each is a dome-shaped cell (or specialized squamous cell) with a basal concavity that contains intraepithelial lymphocytes and macrophages. • They (macrophage) phagocytose and transport antigens present in the intestinal lumen to the underlying lymphoid tissue cells to initiate the immune response to these antigens leading to the secretion of IgA. (Surface antibodies) Small intestine lamina propria contain lymphatic nodules “appear most in ileum because it near to the large intestine which is full of bacteria” which a collection of lymphocytes and macrophages. The M cells was ‫ ﺧﻠﯾﺔ ﻋﺎدﯾﺔ‬but due to the cells in the lymphatic nodules ‫ ﺣﻔرت‬in the basal part of the cell near the lumen , has non microvilli and modified to present the Auto immune Cells mainly the macrophages. “Sometimes because of its small thickness ‫ ﻣﻣﻛن ﺗدﺧل ال‬antigen by pinocytosis” CCK-PZ cells: • secrete cholecystokinin (pancreozymin) MCQs 01 Which one of the following is present ONLY in ileum: A-serosa 02 A- IgE 03 A- stomach 04 A- simple columnar epithelium 05 A- Serosa B- Peyer’s patches C-Brunner’s glands D- lamina propria M cells can lead to the secretion of: B- IgG C- IgA D-IgM Crypts of Lieberkühn are present at: B- small intestine C- large intestine D- esophagus Which one of the following cells covers the villi: B- stratified columnar epithelium C-simple cuboidal epithelium D-simple squamous epithelium Paneth cells are present at: B- villi C- Crypts Answer key: 1. B 2. C 3. B 4. A 5. C D- Submucosa This Lecture is done by: Members ● ● ● ● ● ● ● ● ● Hamad Alyahya Khalid AlRasheed Faisal Alzuhairy Abdullah Aldhuwaihy Fahad Almughaiseeb Abdulrahman Alosleb Abdulrahman Alomar Omar Banjar Yousof Badoghaish ● ● ● ● ● ● Waad Alanazi Raghad Almuslih Reema Alzughaibi Retal Alshohail Raghad Alothman Shaden Alhazzani Leaders ● Khalid Alanezi ● Waad alqahtani Reviewed by ● Academic leaders