U01.01.032 Collagen

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Learning Objectives

  • Identify the most common types of Collagen and their tissue distributions.
  • Master the SCAB mnemonic for Types I–IV.
  • Correlate collagen defects with clinical conditions like Osteogenesis Imperfecta and Ehlers-Danlos.
  • Understand the role of collagen in wound healing and basement membrane pathology.

1. Overview of Collagen

Collagen is the most abundant protein in the human body. It undergoes extensive post-translational modification to organize and strengthen the extracellular matrix.

2. The Four Major Types: SCAB Mnemonic

Use the SCAB mnemonic to remember the primary location for Types I through IV:

Type Mnemonic (SCAB) Key Locations & Details
Type I Skeleton Bone (osteoblasts), Skin, Tendon, Dentin, Cornea, Late wound repair.
Type II Cartilage Hyaline cartilage, Vitreous body, Nucleus pulposus.
Type III Arteries Reticulin—Blood vessels, Uterus, Fetal tissue, Early wound repair.
Type IV Basement Membrane Basal lamina, Glomerulus, Cochlea, Lens.

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3. Clinical High-Yields: Types I, II, & III

  • Type I: Production is decreased in Osteogenesis Imperfecta Type I. (Remember: Type I = Bone).
  • Type II: Found in “car-two-lage.”
  • Type III: Deficient in the Vascular type of Ehlers-Danlos syndrome (ThreE D).
    • Wound Healing: Myofibroblasts secrete collagen during the proliferative stage and are responsible for wound contraction.

4. Type IV: The Basement Membrane

Type IV collagen is “under the floor” (the basement). It is critical for filtration and structural support.

  • Alport Syndrome: An inherited defect in Type IV collagen; affects the kidneys (glomerulus), ears (cochlea), and eyes (lens).
  • Goodpasture Syndrome: Autoantibodies target Type IV collagen, leading to pulmonary hemorrhage and glomerulonephritis.

 

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