The integumentary system consists of the skin, hair, and nails. The skin is the largest organ of the body and has three layers - the epidermis, dermis, and hypodermis. The epidermis is the outermost layer and acts as a barrier, the dermis contains hair follicles, glands, and sensory receptors, and the hypodermis contains fat and connective tissue. The skin has several important functions including protection, temperature regulation, sensation, vitamin D synthesis, and acting as a reservoir for blood. It protects through chemical secretions, physical barriers, and immune cells. Common skin disorders include eczema, psoriasis, and melanoma.
15. 1. Epidermis
• Most superficial layer of skin
• First barrier of protection
• Principle (main) cell type in epidermis
= keratinocytes
• 4-5 layers
• 4 types of epidermal cells
28. Epidermal Cells
• Keratinocytes: compose most of
epidermis; make protein keratin
• Keratin: waterproofs and protects skin
• Melanocytes:synthesize melanin
• Melanin protects against UV damage
• Merkel cells: associated with sensory
receptors (touch)
• Langerhan’s cells: macrophages used
in defense against microorganisms