Histo & Embryo

What are the layers of the alimentary canal?

• Mucosa

  • Epithelium

  • Lamina propria

  • Muscularis mucosae

• Submucosa

  • Meissner’s plexus

• Muscularis externa

  • Inner circular layer

  • Outer longitudinal layer

  • Auerbach’s plexus

• Serosa/Adventitia

What are the unique histological features of the oral cavity?

• No muscularis externa

• No serosa/adventitia

• Mucosa

  • Non-keratinized stratified squamous epithelium

  • Lamina propria

  • No muscularis mucosae

• Submucosa

  • Minor salivary glands

    • Intrinsic glands

    • Mucus-secreting

______ are muscular folds of the oral vestibule, surrounding the anterior boundary of mouth interspersed with fibro-elastic connective tissue

Lips are muscular folds of the oral vestibule, surrounding the anterior boundary of mouth interspersed with fibro-elastic connective tissue

What is the function of lips?

•Push food into oral cavity:

–Lips and cheeks help keep food over occlusal surface of teeth

What are the layers of the lips?

• Vermillion zone is the external region:

  • Thin epidermis and high dermal papillae cause it to appear red/pinkish

  • No sweat glands, hair follicles, or sebaceous glands—prone to excessive dryness and chapping

• Internally:

  • Nonkeratinized with many minor salivary glands

Cold Sores

•Cold sores are painful contagious blisters that generally appear outside the mouth on the lips:

–Caused by herpes simplex virus (HSV) type 1

–In the dormant state, this virus resides in the trigeminal ganglion

–Factors triggering the HSV virus include sunlight, sunburn, stress, fatigue, other infections, fever, menstruation, and intestinal upset

Canker Sores

•Canker sores (Recurrent Aphthous Stomatitis (RAS)) are painful sores inside the mouth:

–Cause is unknown but may be due to a virus, allergic reaction, or an auto-immune condition

–Factors triggering these sores are injury or irritation (e.g., from dentures or sharp teeth), smoking, stress, a diet lacking in vitamin B12, folic acid or iron, and the onset of menstruation

_________ is the largest structure in oral cavity that lies on floor

Tongue is the largest structure in oral cavity that lies on floor

What is the role of the tongue?

•Roles:

–Chewing (mastication)

–Taste (gustation)

–Swallowing (deglutition)

–Speech (articulation)

–Oral cleansing

What is the purpose of the tongue’s extrinsic and intrinsic muscles?

•Extreme mobility due to mass of intrinsic (4) and extrinsic (4) skeletal muscles:

–Intrinsic muscles alter shape of tongue

–Extrinsic muscles move tongue in/out and side to side

–Covered by a mucous membrane

What divides the tongue?

•V-shaped terminal groove (or sulcus) divides tongue into:

–Posterior part (lingual tonsil)

–Anterior part (numerous mucosal projections)

–Foramen cecum is site of origin of thyroid primordium

Intrinsic muscles of the tongue

What are histological features of the tongue?

•Epithelium: keratinized SSE

•Musculature: extrinsic & intrinsic

•Papillae

–Filiform

–Fungiform

–Circumvallate

–Foliate

Filiform papillae

–Most abundant type

–Keratinized

–No taste buds

–Mechanical role

Fungiform Papillae

–Anterior tongue

–Mushroom-shaped

–Taste buds

•Apical surface

Circumvallate Papillae

–Large, dome-shaped

–8-12

–Moat-like groove

•Taste buds

–Von Ebner’s glands

•Serous lingual salivary glands

Foliate Papillae

–Parallel ridges

–Taste buds

•Lateral surfaces

Taste Buds

•Oval-shaped

•Taste pore

–Opening into the surface

•Sensory cells

•Support cells

•Location

–Lingual papillae

–Oral cavity

•Glossopharyngeal arch

•Soft palate

•Epiglottis

Major Salivary Glands

•Functions: produce the saliva

–Lubrication

–Moistens the food

–Digestion of carbohydrates

–Antimicrobial

–Contains IgA

–Source of Ca and phosphate

•Structure

–Secretory part

–Ductal system

–Capsule and septa

–Stroma

Salivary Glands: Serous Acini

•Protein-secreting

•Cell structure

–Euchromatic nucleus

–Abundant RER

–Apical secretory granules

•Rounded

Salivary Glands: Mucous Acini

•Mucus-secreting

•Cell structure

–Heterochromatic nucleus

–“Frothy” appearance

•Tubular

Types of salivary gland ducts

•Intralobular ducts

–Within lobules

•Interlobular ducts

–Between lobules

•Main ducts

–From glands to oral cavity

Intralobular Ducts

–Intercalated ducts

•Cuboidal epithelium

•Basally-placed nucleus

Intralobular Ducts

–Striated ducts

•Columnar epithelium

•Basal membrane infoldings

•Mitochondria

•Ion transport

•Hypotonic saliva

•Centrally-placed nucleus

Parotid Gland

–Largest

–Serous gland

–Long duct

Submandibular Gland

–Floor of the mouth

–Mixed gland

•Mostly serous

Sublingual Gland

–Floor of the mouth

–Mixed gland

•Mostly mucous

Pleomorphic Adenoma

•Benign tumor

•Rather common

•Composed of

–Ductal cells

–Myoepithelial cells

__________ is a calcification that is formed usually in the submandibular gland

Salivary calculus (sialolithiasis) is a calcification that is formed usually in the submandibular gland

Salivary calculus (sialolithiasis)

•Salivary gland stones can form in any of the salivary glands

•Etiology is unknown, but factors associated with a higher risk include:

–Blood pressure drugs and antihistamines reduce the amount of saliva produced

–Being dehydrated makes saliva more concentrated

–Not eating enough food causes a decrease in saliva production

•Sialoliths are the most common disease of the salivary glands in patients between 30 to 60 years of age:

–Men are more likely to get salivary stones than women

•Main symptom is pain in your face, mouth, or neck that becomes worse just before or during meals

Histological layers of the esophagus

What are the three layers of esophageal mucosa?

• Epithelium

  • Non-keratinized stratified squamous epithelium

• Lamina propria

  • Connective tissue

  • More fibrous

• Muscularis mucosae

  • Different from the rest of GI

  • Longitudinally oriented bundles

  • Smooth muscle

What region of the esophagus is this?

Terminal/Distal esophagus

What and where are the esophageal mucosal glands?

–Esophageal glands proper

•Small

•Compound tubuloalveolar glands

•Most of esophagus

Esophageal submucosa

–Dense irregular connective tissue

–Blood vessels

–Nerve fibers and ganglion cells: Meissner’s plexus

Describe the muscularis externa layers in the different sections of the esophagus

• Upper esophagus

  • Skeletal muscle

• Middle 1/3

  • Skeletal muscle

  • Smooth muscle

• Lower esophagus

  • Smooth muscle

Esophagus Middle 1/3 Slide [ 2 images ]

Barret’s Esophagus

• Metaplasia of esophageal epithelium

  • Stratified squamous to simple columnar

  • Caucasian males > 50 years

  • Results from Gastroesophageal reflux

  • Common precursor of esophageal adenocarcinoma

Layers of the stomach

• Mucosa

• Submucosa

• Muscularis externa

• Serosa

What comprises the surface epithelium of the gastric mucosa?

Simple Columnar

What is contained within the lamina propria?

• fundic glands

• cardiac glands

• pyloric glands

• lymphoid tissue

Gastric Mucosa Histological Slide

Fundic Gland Anatomy

What cells are within fundic glands?

• Parietal

• gastric chief

• mucous neck

• progenitor

• enteroendocrine

Parietal Cell (Location, Properties)

• Location: neck and base of fundic gland

• Large, pyramidal shape

• Numerous mitochondria

  • Stain with eosin

• Secrete

  • HCl

  • Intrinsic factor (B12)

• Apical part of the cell

  • Actively secreting cell

    • Intracellular canaliculi with microvilli

• Resting cell

  • Tubulovesicular system: membrane storage

Gastric Ulcer

• Epithelial protective barrier

  • Impaired

• HCl destroys cells

• Penetrates deep if untreated

  • Peritonitis

What can happen in patients with chronic gastritis?

• Deficiency of parietal cells

• No intrinsic factor produced

• Hemoglobin formation inhibited

• Pernicious anemia

Gastric Chief Cell (Location, Properties)

• Location

  • Base of the gland

• Secrete

  • Pepsinogen

    • Pepsinogen -> pepsin

• Cell structure

  • Abundant RER

    • Protein synthesis

    • Basophilia

• Apical secretory granules

Mucous Neck Cell (Location, Properties, Structure)

• Location

  • Neck of the gland

• Secrete

  • Soluble mucus

• Cell structure

  • Small cell

  • Heterochromatic nucleus

  • Mucinogen granules

  • “Frothy” cytoplasm

Enteroendocrine Cell (Location, Properties, Structure)

• Small cell

• Location

  • Mostly at the base

• Secrete

  • GI hormones

    • Gastrin, ghrelin

  • Into lamina propria

• Cell structure

  • Microvilli

    • On the luminal surface

• Numerous secretory granules

  • At the base of the cell

Progenitor Cell

• Undifferentiated cell

• Location

  • Isthmus

• Precursors for

  • Surface mucous cells

    • Short lifespan: 3-5 days

  • Gland cells

    • Long lifespan: 6-8 months

Cardiac Glands (Distribution, Function, Structure)

• Distribution

  • Narrow ring

    • Around the esophageal orifice

• Function

  • Production of mucus

  • Protection against acid reflux

• Structure

  • Branched tubular glands

  • Mucous glands

  • Basal nucleus

  • Mucinogen granules

  • No parietal/chief cells

Pyloric Glands (Distribution, Function, Structure)

• Distribution

  • Pyloric antrum

• Function

  • Production of mucus

• Structure

  • Branched coiled tubular

  • Mucous glands

  • Basal nucleus

  • Mucinogen granules

  • No parietal/chief cells

• Lamina propria

• Muscularis mucosae

Layers of the Stomach

Malignant Tumors of the Stomach

• Carcinoma

  • From surface epithelial cells

  • Associated with

    • Intestinal metaplasia

• Adenocarcinoma

  • From glandular epithelium

• Stages

  • Early

    • Penetrate into submucosa

    • Good prognosis

  • Late: poor prognosis

    • Penetrate into muscularis externa