Lab 14 Digestive Tract Upper Digestive Tract Introduction

UpperDigestiveTractLab14– UpperDigestiveTractA560– Fall2015

I. IntroductionII. LearningObjectivesIII. SlidesandMicrographs

A. OralCavity1. Lip2. Tooth3. Tongue

B. Esophagus1. Generalstructure2. Mucosa3. Submucosa4. Muscularis5. Adventitia

C. Esophagogastric JunctionIV. Summary

Fig15‐1,Junqueira,13th ed.

Lab14– UpperDigestiveTractA560– Fall2015

Layers of the Gastrointestinal Tract

General Layer Specific Layer Characteristics

Mucosa Epithelium stratified squamous epithelium (for protection) is found in the oral cavity, pharynx, esophagus, and anal canal

simple columnar epithelium (for absorption/secretion) is found in the stomach, small and large intestine

Lamina propria thin layer of loose CT underneath epithelium; supports epithelium and contains a diffuse population of cells (e.g., fibroblasts and leukocytes)

Muscularis mucosae Lt. “muscle of the mucosa”; thin smooth muscle layer of mucosa; allows localized movement/agitation of the mucosa

Submucosa

(w/ Meissner’s plexus)

dense CT with larger blood and lymph vessels; Meissner’s (submucosal) plexus of autonomic (parasympathetic) nerves controls the mucosal glands and the muscularis mucosae; glands and lymphoid tissue may also be present

Muscularis

(w/ Auerbach’s plexus)

Innermost oblique thick layer of smooth muscle with generally two specific layers based upon orientation of muscle fibers [exceptions: (1) the upper 1/3 of the esophagus contains skeletal muscle instead of smooth muscle; (2) the stomach has three layers of smooth muscle, with the addition of an innermost oblique layer]; contraction of the muscles mixes and propels luminal contents forward; Auerbach’s (myenteric) plexus of autonomic (parasympathetic) nerves is found in the thin layer of CT between the muscle layers (along with blood and lymph vessels): it controls contraction of the muscularis (peristalsis)

Inner circular

Outer longitudinal

Serosa/Adventitia adventitia is a layer of thick CT that merges into the surrounding tissue and lacks mesothelium – it covers structures outside of the abdominal cavity: most of esophagus, rectum, and anal canal; serosa is a thin layer of loose CT with vessels and adipose and covered by simple squamous epithelium (mesothelium) – it covers the gastrointestinal tract within the abdominal cavity

Learning Objectives

1. Recognize and understand the general structural characteristics of thegastrointestinal tract: mucosa, submucosa, muscularis, and serosa.

2. Understand the regions and parts of a tooth and how these structures areformed.

3. Understand the functional significance of structures associated with thetongue.

4. Recognize and understand the function of the different glands associated withthe gastrointestinal tract.

5. Recognize the various regions of the gastrointestinal tract (esophagus, stomach,small and large bowels), the major specific cell types specific to each region andhow they contribute to digestive function.

Lip,H&E

oralmucosanonkeratinized stratifiedsquamousepithelium

skinkeratinizedstratifiedsquamousepithelium(w/hairfollicles)

skeletalmuscle

salivaryglands

Lip,H&E

salivaryglands(labialglands)

sebaceousgland

aroundhairfollicle

skeletalmuscle(orbicularisoris m.)

mucosa

Tooth,H&E

root:portionoftoothbelowthegingivaandcoveredincementum

crown:portionoftoothabovethegingivaenamel coversthedentinofthetoothcrown,buthasbeendissolvedawayinthisslide

dentalpulp:looseCT,fibroblasts,

mesenchymalstemcells,andodontoblastson

periphery

gingiva (orgums):mucosathatliesovermandibleandmaxilla

Tooth,H&E

dentindentalpulp

cementumperiodontal

ligament

(exterior) (interior)

Dentin is hard, calcified tissue (70% hydroxyapatite) with Type I collagen that surrounds the dental pulp; itis formed by odontoblasts (neural crest‐derived cells) that line the pulp cavity (periphery of dental pulp);the roots are covered by cementum (bone‐like tissue; the crown is covered by enamel instead); theperiodontal ligament/membrane is fibrous CT with bundles of collagen anchoring the cementum of thetooth into the alveolar bone (Lt. “basin or bowl” – tooth sockets)

Tooth,H&E

odontoblasts

dentalpulp

dentin

predentin:organicfibrillar

matrixofthedentinbeforeitiscalcified

(exterior) (interior)

FetalHead

lookherefordevelopingteeth

FetalHead

odontoblasts

dentin

dentalpulp

ameloblaststallcellspartofthe

specializedepitheliumofthetoothbud;formtheenamel

ofthecrown

enamel

predentin

Tongue,H&E

circumvallatepapilla

filiformpapillaefungiformpapilla

vonEbner’s glands

Filiform papillae (Lt. “thread‐shaped”) are the most numerous papillae of the tongue; they are elongatedand heavily keratinized; they provide friction to move food along; they do not contain taste buds;fungiform papillae (Lt. “mushroom‐shaped”) are less numerous, larger, less‐keratinized, and containtaste buds; circumvallate papillae (Lt. “surrounded with walls”) are 8‐12 very large papillae located onposterior of tongue (near terminal sulcus) surrounded by moat‐like grooves into which serous vonEbner’s glands empty, providing fluid movement over numerous taste buds (~250) on each side of papilla

lookherefortaste

vonEbner’sglands

Tongue,H&E

tastebud

tastepore

General Layer Specific Layer Esophagus

Mucosa Epithelium nonkeratinized stratified squamous epithelium

Lamina propria

Muscularis mucosae prominent (depending on location)

Submucosa

esophageal (submucosal) glands

Muscularis

Inner circular thick; skeletal in upper 1/3 of esophagus, smooth in lower 2/3

Outer longitudinal thick; skeletal in upper 1/3 of esophagus, smooth in lower 2/3

Serosa/Adventitia Adventitia (serosa at lower end)

Esophagus,H&E

mucosa

submucosa

muscularis

veryprominentmuscularismucosae

Esophagus,H&E

mucosa

Esophagus,H&E

submucosa

muscularis(innercirclelayer)

muscularismucosae

Esophagus,H&E

muscularis

esophageal(submucosal)

glands(lubrication)

epithelium

muscularismucosae(verythick)

Esophagus,H&E

muscularis

innercircularlayer

outerlongitudinal

Auerbach’s(myenteric)plexus

Adventitia

Esophagus,H&E

muscularis

Adventitia

someskeletalmusclecanbeseeninthemuscularis layeroftheupperesophagusasittransitionsintoonlysmoothmuscle

GastroesophagealJunction,H&E

muscularis

Esophagus Stomach

lymphnodule

nonkeratinized stratifiedsquamousepithelium

simplecolumnarepithelium

cardiacglands gastric

glands

General Layer Specific Layer Esophagus

Mucosa Epithelium nonkeratinized stratified squamous epithelium

Lamina propria

Muscularis mucosae prominent (depending on location)

Submucosa

esophageal (submucosal) glands

Muscularis

Inner circular thick; skeletal in upper 1/3 of esophagus, smooth in lower 2/3

Outer longitudinal thick; skeletal in upper 1/3 of esophagus, smooth in lower 2/3

Serosa/Adventitia Adventitia (serosa at lower end)

Characteristics of Segments of the Gastrointestinal Tract

Small Intestine

General Layer Specific Layer

Esophagus Stomach Duodenum Jejunum Ileum Large Intestine

Mucosa Epithelium

Lamina propria

Muscularis mucosae

Submucosa

Muscularis

Innermost oblique

Inner circular

Outer longitudinal

Serosa/Adventitia

Lab 14 Digestive Tract Upper Digestive Tract Introduction

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