Histology of Digestive Tube (Esophagus to Colon) PDF

1 Of digestive system Ammar MA Mohammed M.Sc. Human anatomy. AAU 2 The objectives of this lecture are to: Identify the histological structures of the digestive tube. Differentiate between the parts of small intestine. Differentiate between small and large i...

1 Of digestive system Ammar MA Mohammed M.Sc. Human anatomy. AAU 2 The objectives of this lecture are to: Identify the histological structures of the digestive tube. Differentiate between the parts of small intestine. Differentiate between small and large intestine. 4 Digestive tube Begins with esophagus and ends with anus! Common structural plan – tubular & saccular organs 4 concentric tunics Tunics: may be reduced or absent Minor structural modifications (local requirements) Structural Plan 1.Tunica Mucosa Epithelium Membrana Propria Lamina Propria Mucosae Lamina Muscularis Mucosae 2.Tunica Submucosa 3.Tunica Muscularis 4.Tunica Adventitia (Serosa)  Histology of GIT Ammar MA mohammed 7 1 Connects. pharynx & stomach Represents a transition 2 Muscularis. mucosae replaces elastic layer of pharynx 3 Muscularis –. more regular Esophagu s Esophagus – upper portion Stratified Squamous Epithelium Lamina propria Muscularis mucosae (Smooth muscle) Submucosa Tunica musclularis (circular) Skeletal Tunica muscularis (longitudinal) Tunica adventitia Esophagus - high Epithelium – stratified squamous (25 Submucosa – lax, elastic; 7 – 10 cell layers – tall papillae indent lower longitudinal folds; deep surface esophageal glands Muscularis – 2 layers: inner = circular, outer = longitudinal; upper ¼ = skeletal, not regular; middle = mix skeletal/smoot h; lower third = smooth (extent variable) Adventitia – loose, fibrous; blood vessels & nerves Lamina propria - – areolar C.T. – poor elasticity; superficial glands Muscularis mucosae - (extreme upper & lower ends - smooth muscle mucous – compound tubular) Esophagus – high - mucosa Simple columnar epithelium Stratified squamous epithelium Stomach Esophagus Gastro-esophageal junction Gastro-esophageal junction Stomach: Dilated, distorted, capacious sac Descriptive divisions: 1.Cardia 2.Fundus 3.Corpus (body) 4.Pylorus Mucosal lining Thickness: 0.3 mm. (cardia) to 1.5 mm. (pylorus) Mucosa + Submucosa – form longitudinal folds (rugae) rugae Distention alters: number, height of rugae Finer system of furrows  mound shaped areas Form gastric areas 1 to 5 mm. across Foveolae = gastric pits open on mounds foveolae vary by region: 17 / sq. mm. (fundus) 9 / sq. mm. (pylorus) Total in stomach = 3,400,000 Surface epithelium = simple columnar; all are mucous secreting; mucous above nucleus; mucigen peculiar type Surface epithelium into Gastric glands (general): Branched tubular type. Vertical depth: full thickness of mucosa; foveolae serve as “ducts” for several glands 15,000,000 gastric glands (human stomach) Very few at birth Differentiate after birth ½ differentiate after age 10 Total secreting surface: 30 sq. feet Cardiac Glands: Narrow band (cardio-esophageal junction) Zone: 5 mm. to 40 mm. Resemble superficial glands of lower esophagus Continuous series: small, sometimes compound, tubular glands Foveolae = ½ gland length, several glands to 1 foveola Secretory portion: tortuous Cells: resemble mucous cells of fundic & pyloric glands Gland lumen – obvious (clear)  Fundic Glands (Gastric 1 Glands) Fundus & corpus 2 Straight, tubular, minor branching (sides) Regions of gland: 3 1. Foveola (=short duct) 2. Neck (constricted) 3. Body (long) 4 4. Fundus (minor dilation & bend) Duct length/Main gland = Four cell types: 1. Mucous Neck Cells: Numbers increase pyloric end Nuclei flattened, basal Mucous watery 2. Chief Cells Numbers increase cardiac end Comprise much of gland below neck Spherical nucleus, granular elements Basally: striate chromidial substance Period of rest: presecretion granules Activity: reduction in granules 3. Parietal Cells: More abundant – pyloric end Most common between mucous neck cells appear “wedged in”. Also between chief cells Peripheral position Cell shape: wedge-like  conical Lack distinct secretory granules Intercellular secretory channels open to main lumen 4. Argentaffin Cells Enterochromaffin elements Location: between chief cells & basement membrane Slender cell extension may reach lumen Granules in cell base (stain with chrome salts) Precursors of serotonin (vasoconstrictive hormone) Parietal cells Chief cells Stomach - fundus Gastric glands – neck cells Stomach pyloric region Pyloric Glands 1/5th or more – gastric area Intermediate zone: combines features of fundus & pylorus Simple, branched, convoluted-tubular More branching than fundic glands & deeper Only one cell type in body of gland (like mucous neck cells) Few argentaffin cells Lamina Propria of Stomach Mucosa L.P. tissue sparse (consequence of large of glands) Most abundant between foveolae Basic tissue: delicate network collagenous & reticular fibers Diffuse lymphocyte infiltration Solitary (single) nodules can occur – esp. cardiac & pyloric regions Muscularis mucosae – thin with layers inner – circular outer – longitudinal 3rd layer (outermost) some areas - circular Submucosa loose, fibrous & vascular rugae Muscularis 3 thick layers (smooth muscle) inner: oblique middle: circular outer: longitudinal (most robust – inner & outer curvatures of stomach Serosa usual C.T. with mesothelium; continuous with gastric mesenteries  A long tube: longer than peritoneal cavity that results in coiling of the tube Two parts: 1.long, slender part (small intestine) 2.shorter, thicker part (large intestine or colon) both parts are typical tubular organs Common features and distinctive features Features Common to Small & Large Intestines Mucosa: Mucosa Epithelium = simple columnar Draped over villi Dips into glands Cells types through entire intestine Exception: Duodenal Glands of Brunner 4 cell types present at all levels Simple Columnar Cells Distribution of cell types not Goblet Cells uniform at Paneth Cells various levels! Argentaffin Cellws Cell Types 1. Simple Columnar Cells: Cells Tall, plastic, elastic Cytoplasm finely granular Free surface: striate border (best seen near main lumen) Cytoplasm near surface: felt-like ectoplasm (= terminal web) web Cells: primarily absorptive (near main lumen) 2. Goblet Cells: Cells Typical unicellular mucous glands All secretory stages seen Lack striate border Numbers increase from duodenum to rectum 3. Paneth Cells: Cells Large cells Most numerous: small intestine Zymogenic cells Cell base dark-staining, striated Above nucleus: large, round, refractile, acidophilic granules Paneth 4. Argentaffin Cells: Cells Largely restricted to intestinal glands Rare on villi Most numerous: duodenum & appendix Flask-shaped, small granules under nucleus Yellow when fresh; acidophilic Serotonin production Surface covering: covering limited – intervals between glands Components: Columnar cells & Goblet cells Intestinal Glands: Glands Pit-like (= intestinal crypts of Lieberkuhn) Lieberkuhn 180,000,000 glands Extend through lamina propria (0.1 to 0.7 mm.) Gland base close to muscularis mucosae Epithelium: Columnar cells, Goblet cells, Paneth cells, and Argentaffin cells Upper ½ gland – cells with striate border Goblet cells upper ½; Paneth near base Lamina Propria: Propria fills in between glands Reticular tissue framework Infiltrated with free cells Also: delicate collagenous fibers; many elastic fibers Reticular network: condenses into basement membrane Solitary lymph nodules (30,000) – often encroach into submucosa Aggregate nodules (Peyer’s Patches) – commonest in Ileum Muscularis mucosae: inner = circular; outer = longitudinal Submucosa: Submucosa Loose areolar C.T. Vascular & Nerve plexuses Ring-like folds (Plicae circulares) – small intestine Brunner’s glands (duodenum) Muscularis: Muscularis Inner layer: circular Outer layer: longitudinal Small intestine = solid coat Large intestine = 3 equally spaced bands (Taenia coli) coli Serosa: Serosa  Lamina propria Submucos Crypt of a Lieberkuhn Musculari Muscularis Duodenum – s mucosae Brunner’s Glands Ileum – lymphatic nodules Ileum - nodule Duodenum Ileum Jejunum Small Intestine Mesenteries: Serosa leaves abdominal wall & reflects around gut Parietal peritoneum unites (double sheet) Visceral peritoneum – double sheet splits around gut as serosal coat Mesothelium (surface) C.T. layer under mesothelium blood vessels, lymphatics, nerve considerable fat some lymph nodes  Large intestine ~5 feet long; width double that of small intestine Caecum, appendix, colon, rectum Lining: no plicae circularies; no villi Intestinal glands of colon = longer than those of small intestine; closer together Differ only quantitatively Epithelial cell types identical to small intestine Ileo-cecal Valve: Valve Apposed folds of mucosa & submucosa Support: central plate smooth muscle Circular layer provides smooth muscle Parallel free edges  slit-like orifice Caecum: Caecum = blind sac (structurally like rest of colon) Change from Ileum to Caecum  abrupt Vermiform Appendix: Appendix * Blind, finger-like process (blind end of caecum) * Wall – very thick, lumen small (relatively) * Deep pockets between mucosal folds * Irregular, angular appearance * More rounded in adults * Lumen – detritus filled * Mucosa: * Glands decrease (middle/old age) * Many goblet cells, occassionally Paneth cells * Argentaffin cells most (?) numerous – compared to other parts of gut Lymphoid tissue (lamina propria – conspicuous); Result: very thick wall Closely spaced – solitary nodules Germinal centers – very large; complete ring Nodules push into submucosa Muscularis mucosae – poor; broken (nodules) Submucosa – ordinary, thick; may fibrose Muscularis – thin Serosa – like rest of gut Colon: Colon Mucosa – does not form folds Surface: simple columnar cells Thin striate border Scattered goblet cells Glands – longer (0.4 mm. to 0.6 mm.) Regular verticl rows, close Largely goblet cells Argentaffin cells (occasional); Paneth cells (rare) Lamina Propria: like small intestine Eosinophils (numerous) Lymph nodules - (larger) into submucosa Muscularis mucosae – 2 typical layers (smooth muscle) Submucosa – no peculiarities Musclaris – internal (circular) typical; external 3 longitudinal ribbon- like strips (= taeniae) taeniae Taeniae shorter than colon length – puckers colon into haustra Colon-Taenia coli Between haustra – wall forms crescentic Plicae semilunares Serosa – Peritoneal reflection incomplete Colon pressed against body wall Attached to serosa: appendices epiploicae = redundant serosa Colon Revision  Histology of GIT 62 Regions of the stomach and their histological structure Ammar MA mohammed  Histology of GIT Ammar MA mohammed 63 Any questions Thanks ???????