Lecture 1 Histology GIT 1 (Lip-Stomach) Lecture Notes PDF

Faculty of Medicine Medical Education- Damietta University Level 2 Semester 3  Learning Outcomes ❑ By the end of the lecture, the students will be able to: Describe Structure of Lip, Tongue, Esophagus and Stomach  Lecture Outline Stru...

Faculty of Medicine Medical Education- Damietta University Level 2 Semester 3  Learning Outcomes ❑ By the end of the lecture, the students will be able to: Describe Structure of Lip, Tongue, Esophagus and Stomach  Lecture Outline Structure of: LIP TONGUE ESOPHAGUS STOMACH  Case scenario A 65 years old female suffering from osteoarthritis and have received NSAIDs for loge time. She developed epigastric pain, heartburn, nocturnal pain, nausea, postprandial pain. Later on she complained from weight loss and easy fatigability. Q1: What is the possible diagnosis?  Overview The digestive system consists of: The digestive tract — oral cavity, esophagus, stomach, small and large intestines, and anus Associated glands— Salivary glands, liver, pancreas  1. LIP The lip is formed of 1. Outer surface. 2. Inner surface. 3. Middle layer. 4. Red margin.  1. LIP The lip is formed of 1. Outer surface. 2. Inner surface. 3. Middle layer. 4. Red margin.  Inner surface Outer surface Covered with mucous membrane (oral mucosa) Thin skin formed of: Epidermis (stratified Epithelium (stratified squamous keratinized squamous non-keratinized epithelium) epithelium) Dermis (sweat glands, hair no hair follicles, no sebaceous glands follicles & sebaceous glands). no sweat glands). Lamina propria contains blood vessels, nerves, Labial glands. 3. Middle layer: contains striated muscle fibers in various directions (orbicularis oris) and connective tissue. 4. The free red margin or vermilion border of the lip: Covered with modified thin skin (non keratinized, no hair follicles, no sebaceous glands and no sweat glands). The epidermis is transparent and its redness is caused by blood capillaries in the underlying connective tissue. 2. TONGUE.  2. TONGUE. Tongue is a mass of skeletal muscle covered by mucosa, which manipulates ingested material during mastication and swallowing. Skeletal muscle oriented in three directions: longitudinal, transverse, and oblique.  2. TONGUE Ventral surface of the tongue is covered with smooth loosely attached mucous membrane (stratified squamous non- keratinized epithelium). Dorsal surface of the tongue is covered with rough, firmly adherent mucous membrane (stratified squamous partially- keratinized epithelium). Dorsal surface of the tongue Dorsal surface It is divided by a V-shaped sulcus terminalis into: The anterior 2/3 contains small projections of the mucous membrane called lingual papillae. The posterior one third shows aggregations of lymphatic tissue , the lingual tonsils.  LINGUAL PAPILLAE :are elevations of the mucous membrane on the dorsal surface anterior two-thirds of the tongue. Types: 1. Filiform papillae 2. Fungiform papillae 3. Circumvallate papillae 4. Foliate papillae  Taste Buds Neuroepithelial cells. Site : present in fungiform, circumvallate, and foliate papillae.  Taste Buds Structure: a. Supporting (sustentacular) cells , b. Neuroepithelial cells (gustatory cells); both types of cells have large microvilli called taste hairs that project into the taste pore. c. The Stem cells lie beneath the other two cell types and differentiate into one or the other; regenerating gustatory cells every 7-10 days.  Lingual salivary glands: Lingual salivary glands: They are mucous and serous that located in the lamina propria of the tongue. GENERAL STRUCTURAL FEATURES: The wall of the digestive tract is formed of 4 main layers: 1. The mucosa. 2. The submucosa. 3. The musculosa. 4. The adventitia, or serosa. 1. Mucosa (mucous membrane): a. Epithelial lining: The digestive tract is lined with stratified squamous non keratinized epitheliums except in stomach and intestine it is simple columnar. Epithelium. b. Lamina propria (ct corium): This is the loose connective tissue layer, rich in blood vessels, lymphatics and mucous glands. c. Muscularis mucosa: It is a thin layer of inner circular and outer longitudinal smooth muscle fibers. 2. Submucosa: It is the layer of loose connective tissue.Contains Meissner's autonomic Plexus 3. Musculosa: It is formed of inner circular and outer longitudinal layers of smooth muscle coat. Contains ( Auerbach 's Plexus). 4. Adventitia or serosa  ESOPHAGUS 1. Mucosa a. Epithelium: formed of non- keratinized stratified squamous epithelium b. Lamina propria: Loose connective tissue that contains "cardiac glands" at the upper and lower ends of the esophagus. c. Muscularis mucosa: Inner circular and outer longitudinal thin layers of smooth muscle fibers. 2. Submucosa It consists of loose connective tissue & esophageal glands. 3.Musculosa: It is formed of inner circular and outer longitudinal layers. The muscle fibers of theupper1/3 of the esophagus is striated and that of the lower1/3 is smooth. In the middle 1/3 both kinds are found. 4. Adventitia: thin adventitia of connective tissue.  STOMACH. The STOMACH is formed of 1.The cardiac region 2. The fundic region & body 3. The pyloric region  THE FUNDIC REGION AND THE BODY 1. Mucosa a. Epithelial lining: simple columnar epithelial cells b. Lamina propria : Formed of loose connective tissue and the fundic gland c. Muscularis mucosa: Two thin layers of smooth muscles arranged into inner circular and outer longitudinal layers. 2. Submucosa: It is the loose connective tissue layer & Meissner's plexus of nerves. 3. Musculosa: The smooth muscle fibers are arranged in three directions; inner oblique, middle circular and outer longitudinal. Auerbach's plexus is found in between the muscle fibers. 4. Serosa A thin layer of loose connective tissue covered with mesothelium  Epithelial cells in the fundus of stomach The fundus is lined with 1. Surface mucous cells 2. Mucous neck cells 3. Parietal cells 4. Chief cells 5. Enteroendocrine (Argentaffin) cells (APUD) cells. 6. Stem cells  Surface mucous Mucous Parietal or Oxyntic cells cells neck cells Site Surface & isthmus neck between mucous neck cells pale tall columnar As Surface large rounded and acidophilic LM cell with basal oval mucous cytoplasm nuclei. cells central rounded nuclei. mucous secretory As Surface Deep intracellular canaliculi with granules are found EM mucous numerous long microvilli. in the apical part cells Mitochondria are very numerous. of the cytoplasm.  Surface Mucous neck Parietal or Oxyntic cells mucous cells cells secrete 1. HCl formation and secretion. secrete a cidic Function neutral 2. Secretion of the intrinsic factor (IF) mucus. mucus. essential for the absorption of vitamin B12.  Enteroendocrine Chief cells (Argentaffin) cells Undifferentiated Stem cells (Zymogenic or Peptic cells) (APUD) cells Site lower part of the glands. base of the glands. neck of the gland pyramidal cell apical stained with silver Low columnar cells acidophilic zymogen stain. Few in number. granules. Give rise to all the other basal basophilic cell types cytoplasm. LM basal and rounded nucleus  Chief cells (Zymogenic or Enteroendocrine (Argentaffin) cells Peptic cells) (APUD) cells Euchromatic nucleus with A pical nucleus and a prominent prominent nucleolus. nucleolus. Basal electron dense secretory Basal RER and free EM granules. ribosomes. Free ribosomes, infra nuclear GA, Prominent mitochondria & RER , Mitochondria. supranuclear GA secretion of Gastrin, Enteroglucagon, secretion of pepsinogen. Somatostatin, Serotonin & Endorphine Function hormones  NB: ✓Enteroendocrine cell have apical microvilli to monitor the gastric lumen content. ✓Enteroendocrine cell is one of the diffuse neuroendocrine system (DNES) ✓Amine precursor uptake and decarboxylation (APUD) cells  Pylorus 1. Mucosa a. The lining epithelium is similar to that of the fundic region. b. Lamina propria contains pyloric glands. c.Muscularis mucosa : two thin layers (inner circular and outer longitudinal layers). 2. Submucosa: As fundus. 3. Muscularis mucosa: Smooth muscle fibers are arranged in two layers, an inner circular and an outer longitudinal. The circular layer is very prominent and constitutes the pyloric sphincter 4. Serosa: As fundus. Fundus Pylorus  Fundus Pylorus Mucosa -Thick & highly folded Thin & less folded -Contain fundic glands Contain pyloric glands Submucosa Wider - Narrower Thinner Thicker Smooth muscle fibers inner : 3 Smooth muscle fibers : 2 layers Musculosa layers oblique, inner circular middle circular outer longitudinal outer longitudinal.  Fundic gland Pyloric gland 1. Long simple branched tubular gland. 1. Short simple branched tubular gland. 1. Narrow and short gastric pits. 2. Wide and deep gastric pits. 2. crowded to each other. 3. not crowded to each other. 3. They occupy most of the thickness 4. They occupy about ½ of the of the mucosa. mucosa. 4. six types of cells are present 5. No peptic cells ocassionaly oxyntic Fundic gland Pyloric gland  Case Discussion This is a case of gastric ulcer NSAIDs can cause erosions of the stomach’s mucosa producing an ulcer. May be complicated with perforation and bleeding. The surface of the stomach is protected from the acidity of its secretion by the neutral mucus from: A. surface mucous cells. B. mucous neck cells. C. goblet cells. D. cardiac glands. Argentaffin cells are so called because they are stained with: A. osmic acid. B. H&E. C. silver. D. gold. E. Sudan III. Enteroendocrine cells in the stomach secrete: A. vitamin Bl2 intrinsic factor. B. digestive enzymes. C. mucous. D. serotonin. E. HCL.