BIO 251 Chapter Notes - Chapter 5: Stratum Corneum, Stratum Granulosum, Stratum Lucidum
Document Summary
Protection from external agents - bacteria, abrasion, water loss, heat loss. Epidermis outermost protective layer, nutrients diffuse upwards from dermis. Originate in deepest epidermal layer, stratum basale. Divide into new cells beneath them, pushed up through strata. On the way, they produce more and more keratin until they are filled with it. By the time they reach the most superficial layer, stratum corneum, they are dead keratin-filled sacs. Particularly thick in areas of persistent friction (hands, feet, calluses) Protective pigment that shields the nuclei of keratinocytes. Key players in immune system - eat alien substances. Kielb tip: know figure 5. 2 the main structural features of the skin epidermis illustration. Highly mitotic stem cells (young keratinocytes), melanocytes and dendritic cells. 4-6 layers of gradually flattening cells with deteriorating organelles as keratohyaline granules (keratin forming) and lamellar granules (help with water barrier) accumulate. Unique to thick skin - skin most subject to abrasion. 20-30 layers of dead cells, protect from abrasion, waterproofed.
