Histology Prelims

• Digestive system


  • Consists of the alimentary canal and its principal associated organs, including the tongue, teeth, salivary glands, pancreas, liver, and gallbladder
  • Major functions include transport of ingested water and food, secretion of fluids and digestive enzymes, digestion and absorption of digested products, and excretion of indigestible remains
• Alimentary canal


  The lumen is physically and functionally external to the body
• Digestion


  1. Food is broken down physically and chemically so that the degraded products can be absorbed into the body

  2. The various segments of the alimentary canal are morphologically specialized for specific aspects of digestion and absorption
• Approximately 2 L of water and food are ingested into the body each day
• Ingestion and preliminary processing


  1. Food is macerated, moistened, and formed into a bolus by the oral cavity and salivary glands

  2. Food passes rapidly through the pharynx to the esophagus
• Digestion and absorption


  1. Food passes more slowly through the gastrointestinal tract, aided by digestive juices

  2. Most fluids and nutrients are absorbed chiefly through the wall of the small intestine, with a small portion absorbed in the large intestine
• Excretion


  Undigested food and other substances within the alimentary canal, such as mucus, bacteria, desquamated cells, and bile pigments are excreted as solids (feces)
• Alimentary mucosa


  • Performs functions including secretion, absorption, barrier, and immunologic protection
• Oral cavity

  Consists of the mouth and its structures, including the tongue, teeth and supporting structures, major and minor salivary glands, and tonsils
• Vestibule


  The space between the lips, cheeks, and teeth
• Oral cavity proper


  The space behind the teeth, bounded by the hard and soft palates, tongue, floor of the mouth, and entrance to the oropharynx
• Major salivary glands


  • Parotid
  • Submandibular
  • Sublingual
• Parotid gland

  • Largest of the three major salivary glands, located in the infratemporal region
  • Excretory duct (Stensen's duct) opens at the parotid papilla on the cheek
• Submandibular gland


  • Located in the submandibular triangle of the neck
  • Excretory duct (Wharton's duct) opens at the sublingual caruncle on the floor of the oral cavity
• Sublingual gland


  • Located inferior to the tongue within the sublingual folds
  • Has multiple small excretory ducts that enter the submandibular duct or the oral cavity directly
• Digestive system


  • Consists of the alimentary canal and its principal associated organs, including the tongue, teeth, salivary glands, pancreas, liver, and gallbladder
  • Major functions include transport of ingested water and food, secretion of fluids and digestive enzymes, digestion and absorption of digested products, and excretion of indigestible remains
• Alimentary canal


  The lumen is physically and functionally external to the body
• Digestion


  1. Food is broken down physically and chemically so that the degraded products can be absorbed into the body

  2. The various segments of the alimentary canal are morphologically specialized for specific aspects of digestion and absorption
• Approximately 2 L of water and food are ingested into the body each day
• Ingestion and preliminary processing


  1. Food is macerated, moistened, and formed into a bolus by the oral cavity and salivary glands

  2. Food passes rapidly through the pharynx to the esophagus
• Digestion and absorption


  1. Food passes more slowly through the gastrointestinal tract, aided by digestive juices

  2. Most fluids and nutrients are absorbed chiefly through the wall of the small intestine, with a small portion absorbed in the large intestine
• Excretion


  Undigested food and other substances within the alimentary canal, such as mucus, bacteria, desquamated cells, and bile pigments are excreted as solids (feces)
• Alimentary mucosa


  • Performs functions including secretion, absorption, barrier, and immunologic protection
• Oral cavity


  Consists of the mouth and its structures, including the tongue, teeth and supporting structures, major and minor salivary glands, and tonsils
• Vestibule


  The space between the lips, cheeks, and teeth
• Oral cavity proper


  The space behind the teeth, bounded by the hard and soft palates, tongue, floor of the mouth, and entrance to the oropharynx
• Major salivary glands


  • Parotid
  • Submandibular
  • Sublingual
• Parotid gland


  • Largest of the three major salivary glands, located in the infratemporal region
  • Excretory duct (Stensen's duct) opens at the parotid papilla on the cheek
• Submandibular gland


  • Located in the submandibular triangle of the neck
  • Excretory duct (Wharton's duct) opens at the sublingual caruncle on the floor of the oral cavity
• Sublingual gland


  • Located inferior to the tongue within the sublingual folds
  • Has multiple small excretory ducts that enter the submandibular duct or the oral cavity directly
• Minor salivary glands


  • Buccal
  • Labial
  • Lingual
  • Palatine
• Tonsils


  Aggregations of lymphatic nodules clustered around the posterior opening of the oral and nasal cavities
• Tonsillar (Waldeyer's) ring


  • Palatine tonsils
  • Tubal tonsils
  • Pharyngeal tonsil (adenoid)
  • Lingual tonsil
• Oral mucosa


  Consists of masticatory mucosa, lining mucosa, and specialized mucosa
• Masticatory mucosa


  • Found on the gingiva and hard palate
  • Has a keratinized or parakeratinized stratified squamous epithelium
  • Lamina propria is thick with papillae and blends with the periosteum, lacking a submucosa
• Lining mucosa


  • Found on the lips, cheeks, alveolar surface, floor of mouth, inferior tongue, and soft palate
  • Epithelium is generally non-keratinized, with fewer and shorter papillae to allow for movement
  • Distinct submucosa underlies the lining mucosa, containing blood vessels, nerves, and minor salivary glands
• Fordyce spots are sebaceous glands found in the submucosa just lateral to the corner of the mouth and opposite the molar teeth
• Filiform papillae


  • Mechanical papillae distributed over the entire anterior dorsal surface of the tongue, with tips pointing backward
• Fungiform papillae


  • Mushroom-shaped projections scattered among the filiform papillae, more numerous near the tongue tip
  • Contain taste buds
• Circumvallate papillae


  • Large, dome-shaped structures located just anterior to the sulcus terminalis, surrounded by a moat-like invagination containing numerous taste buds
  • Ducts of lingual salivary (von Ebner's) glands empty into the moat