STRUCTURES OF THE SKIN HCT I

Layers of The Skin Two primary layers Epidemis Dermis Subcutaneous Tissue- A layer of loose connective tissue and fat that supports the epidermis and dermis. Insulates the body Stored source of energy Shock absorbing pad

Epidermis The outermost and thinnest primary layer of skin. Cells are arranged in distinct layers Thickness varies on the body. Thinnest on the eyelids Thickest on the palms and soles of the feet. Stratum Germinativum- innermost layer where cells divide and push already formed cells to the surface. WHY IS CELL REGENERATION IMPORTANT? Maintaining the skin barrier helps to defend against infection even with injuries.

Epidermis Keratin- a tough waterproof protein that replaces a cells cytoplasm as they approach the surface Provides the outmost layer of skin with abrasion-resistance and protective qualities. Stratum Corneum- Outmost layer of keratin filled cells, made up of dead flat skin cells that shed every couple of weeks. DO YOU KNOW WHAT MOST DUST IS MADE OF?

EPIDERMIS PIGMENT CONTAINING LAYER- epidermal layer that contains pigments called: MELANOCYTES ,(a specialized epidermal cell) which produces a brown pigment called melanin Amount of melanin depends on genetics Increased melanin= increased skin color Sunlight can increase the amount of melanin produced.

EPIDERMIS Dermal Epidermal Junction-the area between the epidermis and dermis. Break down of this junction can lead to blisters. Burns Friction Exposure to irritants (poison ivy)

Dermis Deeper and thicker layer of primary skin layers Composed largely of connective tissue Dermal papillae-(upper layer) Important part of the dermal epidermal junction helping to keep the skin layers together Form groves and ridges unique to each individual. Do you know what the ridges and groves are called? FINGERPRINTS

Dermis Deeper areas contain a network of collagen and elastic fibers These elastic fibers decrease with age contributing to wrinkles Dermis also contains Nerve endings Sweat and sebaceous glands Blood vessels Muscle fibers Hair follicles

Appendages of the skin HAIR Born with hair all over our bodies. Newborn hair is called lanugo Hair follicle- an epidermal tube- like structure required for hair growth Shaft- visible part of the hair Root= lies hidden in the follicle Hair papilla- where hair growth begins Hair bulb- at the base of the follicle (hair papilla is located here) Arrector pili- specialized muscle that produces goose pimples

Receptors Specialized nerve endings – makes it possible for skin to act as a sense organ Meissner’s corpuscle- detects light tough Pacinian corpuscle- capable of detecting pressure

SKIN GLANDS TWO TYPES Sweat (sudoriferous) Sebaceous Sweat or Sudoriferous Glands Eccrine sweat glands-most numerous, important and wide spread. Produce perspiration, which flows out through pores on the surface of the skin Assist with body temperature regulation

Sweat or sudoriferous glands Apocrine sweat glands Found primarily in the axilla and genitalia Secrete a thicker milky secretion Breakdown of secretion by skin bacteria produces odor WHEN DO APOCRINE SWEAT GLANDS ENLARGE AND START FUNCTION? PUBERTY

Sebaceous glands Secrete oil or sebum for hair and skin Level of secretion increases during adolescence Amount of secretion regulated by sex hormones Sebum in sebaceous gland ducts may darken to form a blackhead Acne vulgaris- inflammation of sebaceous gland ducts

Structure of the skin