The main type of collagen in anchoring fibrils (component of dermo epidermal junction) is:
Ans. d. Type VIIType VII Collagen is the major component of anchoring fibrils of the dermoepidermal junction.Dermoepidermal junction or BMZ can be recognized histologically by staining with PAS stain.Ultrastructural examination of dermoepidermal junction by electron microscopy shows 2 different layers with different optical densities#Lamina Lucida - upper, less electron dense layer#Lamina Densa - lower, more electron dense layerDermoepidermal junction is composed of 3 components: 1. Hemidesmosome 2. Anchoring Filaments 3. Anchoring Fibrils.#HemidesmosomeHemidesmosomes are multiprotein complexes that facilitate the stable adhesion of basal epithelial cells to the underlying basement membrane.The intermediate keratin filaments K5/K14 present within the basal keratinocytes attach to the hemidesmosomes at the base of the cell.The major hemidesmosomal protein is Bullous Pemphigoid Antigen-1 (BPAg1 or BP230) and this attaches to the transmembrane component protein BPAg2 (BP 180) below.The other hemidesmosomal protein Plectin is attached to the transmembrane component protein called as a6b4 integrin below.#Anchoring filaments/Lamina Lucida and Lamina Densa.The anchoring filaments form the Lamina Lucida layer.Anchoring filaments consist of Laminin 5/332 proteins that connect BPAg2 and a6b4 integrin above to Lamina Densa below.Lamina Densa is an electron dense layer present in the dermoepidermal junction composed mainly of Type IV Collagen. It also contains various other proteins like Laminin 1/111, BM-40, SPARC, Nidogen and Perlecan.#Anchoring fibrilsThese are ultrastructurally U shaped structures that attach the Lamina Densa above to the underlying connective tissue below in dermis.Type VII Collagen is the major protein in anchoring fibrils.
Type IV
Type III
Type II
Type VII
Anatomy of Skin