Organisation of the Cells into Tissues

GI tract

Salivary glands

  • Parotid, submandibular, sublingual
  • Striated ducts

Oesophagus to anal canal

4 major layers:
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Mucosa
  • Endothelium: sits on basal lamina
  • Lamina propria: loose connective tissue
  • Muscularis mucosae: thin layer of smooth muscle
Submucosa
  • Loose connective tissue
Muscularis externa
  • 2 thick layers of thick muscle (inner circular layer and outer longitudinal layer)
Serosa or adventitia
  • Outer layer of connective tissue; either suspends digestive tract (serosa) or attaches to other organs (adventitia)

Types of mucosa

Protective mucosa
  • Non-keratinized stratified squamous epithelium
  • Found in:
    • Oral cavity
    • Pharynx
    • Oesophagus
    • Anal canal
Absorptive mucosa
  • Simple columnar epithelium with villi and tubular glands
  • Small intestine
Secretory mucosa
  • Simple columnar epithelium with extensive tubular glands
  • Stomach
Protective and absorptive mucosa
  • Simple columnar epithelium with tubular glands
  • Large intestine

ENS

  • Nervous system of the GI tract

Respiratory system

  • Bronchi: large diameter airways with hyaline cartilage in their wall
  • Bronchioles: small diameter airways, no cartilage, mainly smooth muscle
  • Alveoli: site of gas exchange, lined by simple squamous epithelium

Liver

  • Hepatic lobules are small divisions of the liver defined at the histological scale
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Pancreas

  • Exocrine: pancreatic digestive enzymes
  • Endocrine: Islets of Langerhans → insulin and glucagon