Notes on Gastrointestinal System

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• Nonkeratinized stratified squamous epithelium.

• Upper 1/3: skeletal muscle.

• Middle 1/3: smooth + skeletal muscle.

• Lower 1/3: smooth muscle.


• Mucous cells: secrete mucus.

• Chief: pepsinogen; lipase precursor.

• Parietal cells: HCl; intrinsic factor.

• Enteroendocrine cells: peptide hormones; gastrin (only in pylorus).

Small Intestine:

• Columnar absorptive cells: contain microvilli.


• Goblet: acid glycoproteins.

• Paneth: lysozyme.

• Enteroendocrine cells: cholecystokinin and secretin.


• Same as duodenum.


• Peyer patches.

Large Intestine:

• Mucus-secreting cells, Na/H2O transport.

Image of Salivary Glands:

salivary glands and their locations

Types of Salivary Glands:

• Parotid: serous (amylase); CN IX.

• Submandibular: serous; mucous; CN VII.

• Sublingual: mucous; serous; CN VII.

Liver cells:


• abundant in mitochondria and glycogen; produce protein for export.


• phagocytize RBCs, and iron- and pigment-containing bodies.


Additional Notes:

• Plicae circulares: circumferentially arranged submucosal folds increase absorptive power of alimentary tract (also known as digestive tract).

• Missing parietal cell: anemia due to lack of intrinsic factor (B12 deficieicy). (NOTE: parietal cells also secrete HCl).

• Smooth muscle of gastric and small intestine muscularis mucosa innervated by: parasympathetic nerve fibers from the submucosal plexus.

• Chief cells: fundus ONLY.

• Mucous neck cells: neck of gastric glands and all parts of stomach.

• Paneth cells: crypts of Lieberkuhn; also provide immunological function in alimentary canal.

• Goblet cells: all parts of small intestine.

• Basal cells: fundus ONLY.

• Lacteal: absorbs dietary fats.

• Microvilli: microscopic cytoplasmic projections of mucosal epithelial cells present throughout small intestine to increase absorptive power.

• Villi: mucosal projections covering entire small intestine surface.

• GALT: most developed in colon.

• Gastric cells with the fastest turnover: surface mucous cells.

Additional Reading:

Histology and Cytology

1. Cell Components
2. Nervous Tissue
3. Muscle Tissue
4. Lymphoid Tissue
5. Integument
6. Respiratory System
7. Gastrointestinal System
8. Renal/Urinary System
9. Male Reproductive System
10. Female Reproductive System

Gross Anatomy

1. Back and Nervous System
2. Thorax
3. Abdomen, Pelvis, and Perineum
4. Upper Limb
5. Lower Limb
6. Head and Neck
7. Chest Wall
8. Shoulder

Anatomy Videos

1. Video of Musculoskeletal Examination in a Clinical Setting
1. Video of HEENT Examination in a Clinical Setting

Related Topics

1. Jugular Venous Distention Workup

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Useful Medical Images & Diagrams (link opens in a new window)

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