anat 4.3 git histo_zulueta

7/25/2019 Anat 4.3 GIT Histo_Zulueta

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Anatomy 4.3 November 8, 2011

The GIT Histology Dr. Ma. Cristina Elma-Zulueta

OUTLINEDigestive SystemI. ORAL CAVITYII. TONGUEIII. TEETHIV. PHARYNXV. ESOPHAGUSVI. STOMACH

A. CARDIAB. FUNDUSC. BODYD. PYLORUS

VII. SMALL INTESTINEVIII. LARGE INTESTINEIX. APPENDIXX. ANUS

*Text in Times New Roman are lifted from the book

Objectives:At the end of the study, the student should be able to understand the histologyof the GIT:

Describe the different lingual papillae. Describe the structure of the tooth. Review histologic structure of tonsils. Name and describe the layers of the walls of the tract. Differentiate histologically the different segments of the tract. Differentiate the glands in the different areas of the stomach. Describe the modifications.

DIGESTIVE SYSTEM

Consists of the tract from the mouth (oral cavity) to the anus, aswell as the digestive glands emptying into this tract, primarily thesalivary glands, liver, and pancreas

Has the same layers throughout the whole tract

4 Principal Layers

1. MUCOSA OR MUCOUS MEMBRANE (LINING) EPITHELIUM LAMINA PROPRIA loose connective tissue rich in blood vessels,lymphatics, lymphocytes and smooth muscle cells; sometimes alsocontaining glandso MUSCULARIS MUCOSAE/INTERNA - separates mucosa from

submucosa

2. SUBMUCOSA contains denser connective tissue with many bloodand lymph vessels and the submucosal plexus of autonomic nerves

3. MUSCULARIS PROPRIA/EXTERNA the autonomic myenteric nerve plexus is contained in the connective tissue between these twomuscle layers

INNER CIRCULAR OUTER LONGITUDINAL

4. SEROSA/ADVENTITIA SEROSA a thin layer of connective tissue, rich in blood vessels,lymphatics, and adipose tissue, with a simple squamous covering(mesothelium )

ADVENTITIA consisting of connective tissue containingvessels and nerves, lacking mesothelium

Main Function of Digestive tract epithelial lining provide selectively permeable barrier between contents of tract and

tissue of the body Facilitate transport and digestion of food Promote absorption of products of this digestion Produces hormones for the activity of the digestive system Produces mucus for lubrication and protection

nice to know: the lamina propria and the submucosa contain abundant lymphoid

nodules as protection from bacterial invasion in the lamina propria, IgA is also secreted as a form of protection

also against viral and bacterial invasion

I. ORAL CAVITY

Lined by stratified squamous epithelium keratinized ornonkeratinized depending on the region

Keratinized: gingiva & hard palate

Non-keratinized: soft palate, lips, cheeks & floor of mouth

HARD PALATE Stratified squamous keratinized Forms deep invaginations called epithelial ridges Has thick collagen fiber bundles that firmly bind with palatal mucosa

Figure 1: Hard Palate Figure 2: Soft Palate

SOFT PALATE Lined by stratified squamous, non-keratinized Interdigitates with lamina propria forming rete apparatus Movable structure attested by presence of skeletal muscle Core has numerous salivary mucous glands

LIP Two sides: covered by skin mucosa and oral mucosa Contains striated muscles and minor salivary glands Vermillion/Vermillion zone:

o Transition zone between normal skin and lip mucosao Where epidermis is very thin, lightly keratinizedo Lacks gland for oil and sweat


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Group # 5| Batutista V, Bello, Binas, Bobadilla, Bollos, Bongga, Bonifacio, Borlaza Page 2 of

Figure 3: Lip

Lip. oral mucosa (OM), skin (S), hair follicles (F) and associated glands.(V)vermilion zone , is prone to excessive dryness and chapping in cold,dry weather. Internally, the lips contain much striated muscle (M)and many minor salivary glands (G).

II. TONGUE

Stratified squamous non-keratinized epithelium Mass of striated muscle Muscle fibers cross one another in 3 planes Mucous membrane strongly adherent to muscle Dorsal surface: covered anteriorly by papillae

Figure 4: Tongue and Lingual Papillae

CLINICAL CORRELATON

The opposing forces of the Genioglossus muscle on each side of thetongue keep it in the middle. The LEFT genioglossus pushes thetongue to the right while the RIGHT genioglossus pushes thetongue to the left. If tongue is deviated to a side, you can pinpointwhich nerve was damaged.

Terminal Sulcus V-shaped groove th at separates the posterior third of the tongues

dorsal surface from the anterior two thirds.

Anterior two-thirds Body of the tongue With lingual papillae of four types, all containing cores of connective

tissue covered by stratified squamous epithelium

FILIFORM PAPILLAE Very numerous Elongated conical shape or pointed Heavily keratinized Epithelium lacks taste buds Provides rough surface that facilitates food movement duringchewing

FUNGIFORM PAPILLAE Less numerous Lightly keratinized Mushroom in shape With connective tissue cores Have scattered taste buds on their upper surfaces Irregularly interspersed with filiform papillae

FOLIATE PAPILLAE Poorly developed in adults Consist of parallel ridges and furrows on the side of the tongue Taste buds are present

CIRCUMVALLATE PAPILLAE Least numerous Largest Over half the taste buds on the human tongue Form a V-shaped line before the terminal sulcus Von Ebner glands (serous salivary glands) empty into deep groovesthat surround this papilla

Posterior third Root of tongue The mucosa of the root is filled with masses of lymphoid nodules

separated by crypts, all of which comprise the lingual tonsils Stratified squamous non-keratinized epithelium Without lingual papillae

5 qualities in human taste perception: Saltiness (metal ions) Sourness (hydrogen ions from acids) Sweetness (sugars and related organic compounds) Bitterness (alkaloids and certain toxins) Umami or savory (amino acids)*tastants

TASTE BUDS Ovoid structure containing 50-75 cells Half are elongated gustatory/taste cells Other cells: basal stem cells & supportive cells Taste pore: opening where gustatory cells microvilli project Cells are constantly replenished every 7-10days present on fungiform and foliate papillae but are much moreabundant on vallate papillae.


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Figure 5: Taste Buds

III. TEETH

Consists of:o Crown exposed above the gingivao Neck constricted part of the tooth at the gumo Roots below the gingiva that hold the teeth in bony sockets

called alveoli

Figure 6: Teeth

DENTIN Comprise the bulk of the tooth Calcified tissue containing 70% Ca hydroxyapatite Matrix consists of type 1 collagen fibers & glycosaminoglycans Matrix produced by odontoblasts

ENAMEL Hardest component of human body 98% hydroxyapatite 2 unique proteins: amelogenin & enamelin Has no collagen Consists of enamel rods Matrix produced by ameloblasts Produced by cells of ectodermal origin, whereas most of the otherstructures of teeth derive from mesodermal and neural crest cells .

PERIODONTIUM Comprises structures responsible for maintaining the teeth in themaxillary & mandibular bones

Consists of:o Cementum covers the dentin of the root; similar in composition

to bone o Periodontal ligament connective tissue with collagen fiber

bundles connecting the cementum and the alveolar bone of thetooth socket

o Alveolar bone in immediate contact with the periodontalligament, which serves as its periosteum

o Gingiva mucous membrane firmly bound to the periosteum of themaxillary and mandibular bones composed of stratified squamousepithelium and lamina propria with numerous connective tissue

papillae

IV. PHARYNX Transitional space between oral cavity & respiratory & digestivesystems

Forms an area of communication between nasal region & larynx Lined by stratified squamous epithelium near esophagus &respiratory epithelium near nasal cavity

Contains tonsils

V. ESOPHAGUS

MUCOSA: Non-keratinized stratified squamous epithelium Has same major layers as the rest of GIT SUBMUCOSA: contains esophageal glands(mucus-secreting) LAMINA PROPRIA (LP): esophageal cardiac glands (mucus- secreting;

found in the LP near the stomach) MUSCULARIS EXTERNA

o Proximal third: skeletalo Middle third: skeletal & smootho Distal third: smooth

Most distal portion is covered by serosa

The rest is enclosed by adventitia

ESOPHAGOGASTRIC JUNCTION Junction of the esophagus and the cardiac region of the stomach An abrupt change in the mucosa from stratified squamous epitheliumto simple columnar epithelium invaginating as gastric pits

Mucosa contains esophageal cardiac glands that opens into thesuperficial gastric pits


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Figure 7: Esophagogastric Junction

VI. STOMACH Mixed exocrine-endocrine organ that digests food and secreteshormones

Main functions are to continue the digestion of carbohydratesinitiated in the mouth, add an acidic fluid to the ingested food,transform it by muscular activity into chyme

Regions:o Cardiao Funduso Bodyo Pylorus short coiled secretory portion

Rugae longitudinal directed folds in the mucosa and submucosa ofthe empty stomach which usually flattens when it is filled with food

Gastric Pits- invaginations found in the lamina propria Pyloric sphincter- thickening of middle circular layer of muscularisexterna

HISTOLOGIC REGIONAL DIFFERENCES Cardia

o Narrow circular region at the transition between the esophagus andthe stomach

o Mucosa: contains tubular glands, usually branched, with coiledsecretory portions called cardial glands o Short gastric pit

Figure 8: Stomach (Cardia)

Fundus/Bodyo Lamina propria: filled with branched, tubular gastric glands

Figure 9: Stomach (Fundus/Body) Pylorus

o Funnel-shaped region opening into the small intestineo Gastric pits become deeper and the length of the glands will be

shorter or of the same sizeo Middle layer of muscularis is greatly thickened to form the pylor

sphincter

Figure 10: Stomach (Pylorus)

Figure 11: Pyloric Sphincter

HISTOLOGIC REGIONAL SIMILARITIES Lining of epithelium: simple columnar epithelium with mucus-

secreting cells Submucosa has NO GLANDS; found in LAMINA PROPRIA instead No lymphoid aggregates; no villi; with rugae


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Muscularis has 3 muscle layerso Inner Obliqueo Middle Circularo Outer Longitudinal

Most of cells of the gastric glands are mucus- secreting to protectthe wall from HCL

Covered by thin serosa

Figure 12: Stomach

GASTRIC GLAND Has an isthmus, a neck, and a base

Distribution of epithelial cells in the glands is not uniform

Figure 13: Gastric Gland

PARIETAL CELL Present mainly in the upper half of gastric glands w/ fewer in thebase

Large, rounded or pyramidal Central spherical nucleus Intensely eosinophilic cytoplasm because it contains a lot ofmitochondria for production of HCl & intrinsic factor.

Secretory activity is stimulated through cholinergic nerve endingsand by histamine and a polypeptide called gastrin

MUCOUS (NECK) CELLS Irregular in shape, with the nucleus at the base of the cell Columnar cells with mucous in their apex

CHIEF/ZYMOGENIC/PEPTIC CELLS Predominate in the lower region of the tubular glands Cytoplasmic granules contain pepsinogen Produce lipase and hormone leptin Basophilic Columnar

ENTEROENDOCRINE CELLS Epithelial cell type in the mucosa throughout the digestive tract Secretes short polypeptides Enterochromaffin Cells (EC cells) found on the basal lamina ofgastric glands of the fundus and secret serotonin

G Cells in contact with the glandular lumens in the pylorus andlower body of the stomach that produce gastrin

STEM CELLS Found in the neck region of the glands Low columnar cells with basal nuclei and divide asymmetrically

VII. SMALL INTESTINE

Site of terminal food digestion, nutrient absorption, and endocrinesecretion

Lining epithelium: simple columnar with striated border Plicae circulares

o series of permanent circular or semilunar folds o consists of mucosa and submucosao best developed in the jejunum

Villi: epithelium & lamina propria Intestinal crypts/ Crypts of Leiberkuhn: short tubular glands

between villi

Cells lining the intestinal epithelium Enterocytes

o absorptive cellso tall columnar cells with an oval nucleuso striated(brush) border on apical surface

Goblet cellso Less abundant in duodenum, more abundant in ileumo Produce mucins that are hydrated and cross-linked to form mucuso Protect and lubricate the lining of the intestine

Paneths Cello Broad base with narrow apex, at the base of intestinal gland;o exocrine cells with large eosinophilic secretory granules in their

apical cytoplasm that contains lysozymeo functions in innate immunityo regulate the microenvironment of intestinal crypts

Enteroendocrine cellso secrete peptides - have both endocrine and paracrine effectso part of diffuse neuroendocrine system

Microfold (M) cellso Specialized epithelial cells overlying the lymphoid follicles of

Peyers patcheso endocytose antigens and transport them to the underlying

macrophages and lymphoid cells

For Figure 14: Small IntestineAbsorptive surface of the small intestine. (a): The mucosa &submucosa are the inner two of the guts 4 concentric layers. (b): Plicae circulars, the absorptive area. (c, d): They are lined byfinger like projections called villi . Each villus contains lamina propriaconnective tissue with microvasculature & lymphatics called lacteals(e): At the apical cell membrane of each enterocyte are densemicrovilli, which serve to greatly the absorptive surface of the cell.


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Figure 14: Small Intestine

MICROCIRCULATION blood vessels penetrate the muscularis externa forming plexuses in

the submucosa branches extend through the muscularis mucosae and lamina propria

into each villus, forming a capillary network venules from capillary network will drain into the veins of the

submucosal plexus

LYMPHATIC VESSEL Close-ended tube in the villus Lacteals : run to the region of lamina propria above the muscularis

mucosae for lipid absorption

ENTERIC NERVOUS SYSTEM responsible for intestinal contraction /peristalsis

SUBMUCOSAL/ MEISSNERS PLEXUS in the submucosa MYENTERIC/AUERBACHSPLEXUS- between outer longitudinal and

inner circular layers of muscularis externa

DUODENUM Simple columnar epithelium with striated border Duodenal (Brunners) glands

o found in submucosao large clusters of branched tubular mucous glandso secrete alkaline mucus neutralizes chyme, bring intestinal

contents to optimum pH for pancreatic enzyme action

o protect mucous membrane against acidity of gastric juice

JEJUNUM Villi leaf-like prominence of Plicae circulares No glands in submucosa Paneth cells at the bottom of glands, intensely stained

ILEUM Simple columnar epithelium with brush border Peyers patches : aggregates of lymphoid nodules

FOLDS1. PLICAE CIRCULARES/KERCHRINGS VALVE series of permanentfolds consisting of the mucosa & submucosa having semilunar,circular/spiral form

most developed in jejunum increases surface area by 3-fold

Figure 15: Plicae Circulares2. VILLUS

epith. & lamina propria long outgrowths of the mucosa projection into the lumen 10-fold increase in surface area

3. MICROVILLUS 3000/cell

cylindrical protrusion of the cytoplasm consisting of the cellmembrane enclosing a core of actin microfilaments

20-fold increase in surface area

Table 1. Comparison of the three regions of the small intestineDUODENUM JEJUNUM ILEUM

VILLI Tall & slender Leaf-shaped -LAMINAPROPRIA

- -PayersPatches

SUBMUCOSASubmucosal/

BrunnersGlands

- -

ILEOCECAL VALVE Marks the end of small intestine Shows an abrupt change in villous pattern which is found in small

intestine mucosa, to the glandular pattern found in colonic mucosa There is also thickening of muscularis mucosa which is smooth

muscle tissue found beneath the mucosal layer of digestive tract.


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Figure 18: Ileocecal Valve

VIII. LARGE INTESTINE/ COLON/ BOWEL

Main functionso absorption of watero formation of fecal mass from undigestible materialo production of mucus - lubricates intestinal surface

INTESTINAL GLANDo Simple columnar INFESTED with goblet cells!o Colonocytes or absorptive cells : columnar, with short, irregular

microvillio with a small number of enteroendocrine cells

MUCOSAo no folds except in distal (rectal) portiono penetrated by tubular intestinal glandso no villi o Lamina Propria

Rich in lymphoid tissue related to the large bacterial populationof the large intestine

MUSCULARIS EXTERNAo Inner circular layer continuous throughouto Outer longitudinal layer gathered in three longitudinal bands

called taenia coli o Haustra: series of sacs caused by the bands of taenia coli

RECTUM Histologically same with colon. Only difference is the outer

longitudinal muscle is continuous

Figure 19: Intestinal Gland

IX. APPENDIX Simple columnar epithelium with goblet cells With continuous outer longitudinal layer, no taenia coli With abundant lymphocytes and lymphoid follicles in the lamina propria and submucosa

evagination of the cecum small, narrow, irregular lumen fewer & shorter glands

X. ANUS

Anal columns (Columns of Morgagni): series of longitudinal foldsformed in mucosa

Recto-anal junction: mucosal lining changes from simple columnarepithelium with goblet cells to non-keratinized stratified squamousepithelium (keratinized- outside)

Anal Transition Zone

Rectum/Anal CanalA. Colorectal Zone upper 3 rd of anal canal; simple columnar epith.B. ATZ middle anal canal; stratified columnar epith. Interposed bet.

simple columnar epith.C. Squamous Zone lower 3 rd of anal canal; stratified squamous epith.

Anal Glands extend into submucosa & even into muscularis externa;branched, straight tubular; secrete mucus

Circumanal Glands skin surrounding anal orificeSubmucosa at Anal Column submucosal venous plexus

SUMMARYLayers Cell - Stomach Cell - IntestinesMucosaSubmucosaMuscularis propriaSerosa/Adventitia

StemMucousParietalZymogenEnteroendocrine

GD

AbsorptivePanethMicrofold cellsGoblet


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anat 4.3 git histo_zulueta

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