Lab activity manual Histology of the digestive system Jeanne Adiwinata Pawitan Prerequisite: Histology of the 4 basic tissues In this module we learn about the histology of the digestive system, from the oral cavity to anus, including the major glands (liver, pancreas, and gall bladder). The lab activity is divided into 3 parts: oral cavity esophagus, stomach anus, and liver pancreas gall bladder. In laboratory activity, you have to look at the microscopic appearance of the cells, structures and organs in the digestive system, using a microscope. First look at the whole specimen using low magnification (10x4 or 5X10), then look for the structure/cell that you want to see using higher magnification (10x10, 10x20, 10x40, or 10x45). Lab Activity 1: oral cavity - esophagus The oral cavity Specimen: Labium oris (lip) Epithelium Skin: keratinizing stratified squamous epithelium Vermilion border Mucous membrane: non keratinizing stratified squamous epithelium Dermis: sebaceous gland, sweat gland, hair follicle Lamina propria - submucosa: connective tissue papilla, blood vessels, labial glands M. orbikularis oris (striated/skeletal muscle) Specimen: Tongue Epithelium (stratified squamous epithelium) Filiform papilla Fungiform papilla Circumvallate (vallate) papilla Secondary papilla Taste buds Ebner glands Foliate papilla Striated/skeletal muscle interlacing bundles Specimen: Salivary glands (parotid, submandibular, sublingual gland) Serous acinus Myoepithelial cells Mucous acinus Seromucous acinus (mixed) Serous demilune of Giannuzzi Ducts Intercalated duct Intralobular duct Interlobular duct
Specimen: Root of the tooth, cross section Pulp cavity Dentin Dentinal tubules Tomes granular layer Cementum Spaces formerly occupied by Sharpey s fiber Specimen: Embryo Tooth germ (enamel organ) Bud stage, cap stage Bell stage (early, late) Dental lamina Dental sac (tooth follicle) Outer enamel epithelium Inner enamel epithelium Stellate reticulum Stratum intermedium Forming of root Sheath of Hertwig Alveolar bone Dental papilla Odontoblast Ameloblast Predentin Dentin Enamel Oesophagus Specimen: Oesophagus cross section Non keratinizing stratified squamous epithelium : (upper part mucous secreting oesophageal cardiac glands) Muscularis mucosae smooth muscle - longitudinal (towards the stomach very thick) Oesophageal glands (small mucous glands) Submucosal plexus of Meissner - myenteric plexus of Auerbach (Upper part skeletal muscle) Lower part smooth muscle Circular Longitudinal Adventitia/serosa - mesothelium Lab activity 2: stomach -anus Stomach Specimen: oesophagus cardia junction Epithelium: abrupt transition - non keratinizing stratified squamous epithelium simple columnar epithelium (no goblet cell) Cardia: gastric pit (foveola gastrica) moderate (1/4 1/3) Oesophagus: no glands Cardia: cardiac glands tubular, straight/branched, coiled at the base - mucous cells (pale) predominant Muscularis mucosae: continuous across the junction
Oesophagus: small mucous glands Cardia: no glands smooth muscle Oblique (cardia) Circular (oesophagus, cardia) Longitudinal (oesophagus, cardia) Specimen: Fundus/corpus Epithelium: simple columnar epithelium, no goblet cell Gastric pit (foveola gastrica) surface epithelium, shallow (< 1/4) : gastric/fundic glands branched/straight tubular Mucous neck cell Parietal/oxyntic/HCl cell Chief/zymogen/principal cell Muscularis mucosae Circular Longitudinal (oblique/circular) - from the inner to the outer side: (oblique) - circular (longitudinal) Specimen: Pylorus Epithelium: simple columnar epithelium, no goblet cell gastric pit very deep and wide (>1/2) : pyloric glands tubular, coiled - mucous cells (pale) predominant Muscularis mucosae: cir long (cir) (from the inner to the outer side: oblique - circular longitudinal) Small intestine Specimen: Gastro-duodenal junction Epithelium Pylorus Duodenum o No goblet cell o With goblet cells o Lined gastric pit o Lined intestinal villi plicae (semi)circulares/ valves of Kerckring Pylorus: pyloric glands Duodenum: intestinal glands (crypt of Lieberkühn) Muscularis mucosae Pylorus: no gland
Duodenum: Brünner glands (mucous glands) Oblique: pylorus Circular: pylorus, duodenum, thickened at the gastro-duodenal junction forms pyloric sphincter Longitudinal: (pylorus), duodenum Specimen: Duodenum, jejunum, ileum Epithelium Simple columnar epithelium, goblet cells Lined intestinal villi - plicae (semi)circulares/ valves of Kerckring Intestinal glands (crypt of Lieberkühn) Paneth cells at the base Muscularis mucosae: cir long (outer) Duodenum: Brünner glands (characteristics) Jejunum: no characteristics Ileum: Peyer s patches (characteristics) Circular Longitudinal Large intestine Specimen: Appendix small lumen usually full with debris Epithelium: simple columnar epithelium, many goblet cells, no villus Intestinal glands various length, small number Full with diffuse lymphoid tissue and lymph nodules can reach the submucosa Muscularis mucosae poorly developed: cir long (outer) : occasionally contains lobules of adipose tissue thinner than in colon Circular Longitudinal - continuous Specimen: Colon/caecum Epithelium: simple columnar epithelium, many goblet cells, no villus Intestinal glands deeper than in the small intestines Scattered lymph nodules can reach the submucosa Muscularis mucosae: cir long (outer) Circular Longitudinal forms 3 longitudinal bands (taenia coli)
Specimen: Recto-anal junction at the junction: longitudinal folds = columna rectalis Morgagni (anal/rectal column) Epithelium Rectum: simple columnar epithelium, many goblet cells, lined plicae transversales recti Anal canal anus (the external anal orifice): simple columnar/cuboidal, stratified squamous non keratinized keratinized /dermis Rectum: intestinal glands longer, but fewer than in colon Anal canal anus (the external anal orifice): intestinal glands become shorter and disappear, rectal column, circumanal glands (apocrine), internal hemorrhoidal plexus (veins) - hair follicles, sebaceous glands, external hemorrhoidal plexus Muscularis mucosae: cir long (outer), become incomplete and disappear at the anal canal merge with lamina propria/dermis at the anal canal Circular smooth muscle thickened at near the end of anal canal internal anal sphincter Longitudinal Rectum smooth muscle - shorter transversal folds (plicae transversales recti) Near the end of anal canal smooth muscle becomes fibroelastic sheet Distal to the internal anal sphincter: external anal sphincter (skeletal muscle) Adventitia Note: Anatomy: the rectal columns meet one another anal valves at the level of pectinate line (abrupt transition from simple cuboidal/columnar to stratified squamous epithelium) Lab activity 3: Liver, pancreas and gall bladder Liver Specimen: liver (sus) Classical lobules Central vein Cell sheets, hepatocytes, limiting plate Sinusoids Endothelial cells Kupffer cells Ductules (canal) of Herring Prominent interlobular connective tissue (fibrous connective tissue) Portal area (portal tract, portal canal, portal triad, portal radicle, triangle of Kiernan, Kiernan s space) Branch of portal vein Branch of hepatic artery Bile duct Sublobular vein
Specimen: Liver (homo) (the same as in liver-sus) Classical liver lobules (no clear border, more difficult to find, so imagine it using the portal area as its edges) Portal area º Branch of portal vein º Branch of hepatic artery º Bile duct Sublobular vein Specimen: Liver (silver staining) Reticular fibers in Interlobular connective tissue Sinusoid s wall Pancreas Specimen: Pancreas Exocrine portion º Acinus/alveolus Centroacinar cell º Ducts Intercalated ducts Intralobular ducts Interlobular ducts º Connective tissue Intralobular Interlobular Endocrine portion (Langerhans islet) º Difficult to differentiate the various cells º Capillaries Gall bladder Specimen: Gall bladder º Simple columnar epithelium, no goblet cell lines mucosal folds º Lamina propria Rokitansky-Aschoff sinuses smooth muscle irregularly arranged (long-, transverse, oblique) Adventitia/serosa º Loose/faily dense connective tissue º Mesothelium (serosa) º Aberrant bile ducts (Luschka ducts)