Introduction To GI Histology PDF

Introduction to Gastrointestinal Histology Dr. Hatcher [email protected] 859-323-4907  Learning Objective Describe the normal histological organization of the gastrointestinal tract  Characteristics of epithel...

Introduction to Gastrointestinal Histology Dr. Hatcher [email protected] 859-323-4907  Learning Objective Describe the normal histological organization of the gastrointestinal tract  Characteristics of epithelial tissue 1. Avascular mucus coat 2. Tightly packed 3. Anchored to a basement membrane at its basal surface 4. Anchored to each other by tight junctions 5. Apical surface of epithelial tissue next to a free surface. Basement membrane The tubular G.I.T. is a long tube where the external environment is internalized, therefore Lamina propria protection is essential.  What does the red line represent in each image? A Which of these tissue types would be found in the intestines? B  General histological organization of the GI tract Lumen Mucosa Epithelium Lamina propria Muscularis mucosa Submucosa Meissner’s (submucosal) plexus Circular muscle Auerbach’s (myenteric) plexus Muscularis Externa Longitudinal muscle (Propria) Serosa or Adventitia The histology of the GI tract includes four layers from deep to superficial: Diaphragm 1. Mucosa 1. Epithelium* 2. Lamina propria* 3. Muscularis mucosa *Invaginates as glands, evaginates as villi 2. Submucosa -loose areolar CT -provides mobility for overlying epithelium -vascular area for the mucosa -Meissner’s (submucosal) plexus epithelium All lamina propria components of #1 muscularis mucosa submucosa The histology of the GI tract includes four layers from deep to superficial: 3. Muscularis externa -inner circular layer constricts the lumen Diaphragm -outer longitudinal layer shortens the tube -Auerbach’s (myenteric) plexus between the two layers 4. Adventitia/serosa -adventitia loose areolar CT that connects gut tube to adjacent structures or -serosa is a smooth mesothelial layer that supports the gut tube in a mesentery Muscularis externa Serosa or adventitia  Esophagus APR, McGraw-Hill  Layers of the Esophagus The basement membrane is illustrated by the red line. The lamina propria is located deep to this layer, and the muscularis mucosa is outlined by the brown line. Junqueira’s Basic Histology, 2018  Practice label What did you use as a landmark? B A What was most difficult? C D E  General Concept These four general layers adapt according to the function needed throughout the GI tract Examples of modifications of these layers: – Esophagus – Stomach – Colon – Rectum – Anus The esophagus is a fibromuscular tube that is continuous with the end of the pharynx. Epithelium: -nonkeratinizing stratified squamous Submucosa: -folds to allow for dilation of the wall -exhibits mucous submucosal glands throughout Muscularis externa: -upper 1/3 is skeletal -middle 1/3 is mixed skeletal/smooth -lower 1/3 is smooth Adventitia: -travels in the posterior mediastinum -held in place by a connective tissue to the =sites of obstruction adjacent viscera  Gastroesophageal junction: It’s ABRUPT! The gastroesophageal junction (GEJ) is the region where the distal esophagus meets the proximal region of the stomach, or cardiac area. Esophagus Stomach Stratified squamous Simple columnar epithelium Submucosal glands Mucosal glands invaginate into (mucus-secreting) underlying lamina propria  Gastroesophageal junction Stratified Gastric glands squamous Stomach Esophagus Lymphoid nodule Circle represents cardiac glands in the lamina propria Muscularis mucosa  Stomach esophagus cardia fundus body pyloris duodenum Figure 24.12 (a) Layers of the Stomach Opening of gastric glands/pit Lumen of stomach secretions into lumen Epithelium Gastric Mucosa pit Gastric gland Lamina Submucosa propria Lymphatic nodule Muscularis externa Muscularis (propria) mucosae Serosa Oblique layer of muscle Circular layer of muscle Longitudinal layer of muscle (a) Stomach wall  Comparison of GI glands Gastric gland Intestinal gland (small) Colonic gland (large) Gastric pit Gastric gland Figure 24.12 (a) Layers of the Stomach Opening of gastric glands/pit Lumen of stomach secretions into lumen Epithelium Gastric Mucosa pit Gastric gland Lamina Submucosa propria Lymphatic nodule Muscularis externa Muscularis (propria) mucosae Serosa Oblique layer of muscle Circular layer of muscle Longitudinal layer of muscle (a) Stomach wall  Stomach Muscularis Propria The stomach muscularis propria (pink bracket) consists of smooth muscle fibers oriented in three main directions. The external layer is longitudinal (green bracket), the middle layer is circular (yellow bracket) and the internal layer (blue bracket) is oblique. Adapted from Dr. Rueckert’s slide in MD810 Histology/Neoplasia II Large intestine: The large intestine consists of four regions: cecum, colon (ascending, transverse, descending, and sigmoid), rectum, and anal canal. The muscularis externa of the large intestine is unique in that it is arranged in pouches called haustra, created by taenia coli bands that gather the inner circular layers into pouches. Lumen ? Taenia coli ? ? Anorectal junction Junqueira’s Basic Histology, 2018)