Learning Outcomes Lesson 7 5 1 Describe the main structural features of the epidermis and explain the functional significance of each The epidermis is composed of avascular stratified squamous epithelium that s dominated by keratinocytes The name structures of the epidermis are the layers it s composed of ordered from inferior to superior layer A mnemonic device Baby spits grandpa loses cool 1 Stratum basale This layer is attached to the basement membrane by hemidesmosomes It forms the epidermal ridges Think of fingertips Tiny mounds called dermal papillae increase the area of the basement membrane and strengthen attachment between the epidermis and dermis Consists of many basal germinative cells Contains specialized cells 1 Merkel 2 Melanocytes 2 Stratum spinosum This layer is known as the spiny layer and is produced due to division of the stratum basale It s 8 10 layers thick the layers are bound by desmosomes In this layer the cells shrink until the cytoskeletons stick out This is why it s described as spiny Contains Langerhans cells 3 Stratum granulosum This layer is known as the grainy layer Division stops in this layer and the production of keratin and keratohyalin begins Keratin A tough fibrous protein Makes up hair and nails Keratohyalin Dense granules Dehydrates the cell dies Cross link keratin fibers 4 Stratum lucidum THIS LAYER IS ONLY FOUND IN which covers the palms of the hands and soles of the feet SKIN THICK It s known as the clear layer The cells are flat and densely packed with keratin 5 Stratum corneum The horn layer This layer is 15 30 layers of keratinized cells thick and is the exposed surface of the skin It s a water resistant layer This layer is shed and replaced every 2 weeks Undergoes cornification keratinization Serves as protection 5 2 Explain what accounts for individual differences in skin color and discuss the response of melanocytes to sunlight exposure Skin color is influenced by carotene melanin and red blood cells Differences in skin color are due to the production of melanin Melanin protects the skin from UV radiation those with higher melanin production are better protected from sun exposure The way melanin protects the skin from UV radiation is due to the way it s stored which is in melanosomes Melanosomes are concentrated around the cell nucleus to protect the DNA 5 3 Describe the interaction between sunlight and vitamin D3 production Sunlight causes the production of cholecalciferol Vitamin D3 which is produced by epidermal cells and is eventually converted into calcitriol by the liver and kidneys 5 5 Describe the structure and functions of the dermis The dermis is located between epidermis and subcutaneous The function of the dermis is to anchor epidermal accessory layer structures The dermis consists of 2 layers papillary reticular 1 Papillary layer Consists of areolar tissue which allows diffusion of nutrients to the dermis Contains smaller capillaries lymphatics and sensory neurons Has dermal papillae projecting between epidermal ridges 2 Reticular layer Consists of dense irregular connective tissue that withstands stress in multiple directions Contains larger blood vessels lymphatic vessels and nerve fibers Contains collagen and elastic fibers Collagen fibers are strong they resist stretching but bend easily providing flexibility Elastic fibers permit stretching and then recoil they provide flexibility Together they form cleavage lines Contains connective tissue proper 5 6 Describe the structure and functions of the hypodermis The hypodermis subcutaneous layer acts as a cushion adipose tissue stabilizes the skin and allows separate movement It s made of elastic areolar and adipose tissues It s connected to the reticular layer by connective tissue fibers It contains few capillaries and no vital organs 5 7 Describe the mechanisms that produce hair and explain the structural basis for hair texture and color As hair is produced it s keratinized The medulla contain soft keratin and the cortex cuticle contain hard keratin Production begins at the base of a hair follicle deep in the dermis The hair papilla contains capillaries and nerves surrounded by hair bulb The hair bulb produces the hair matrix hair structures and pushes hair up and out of the skin Hair color is produced by melanocytes at the hair papilla amount of melanin production results in different hair colors and is determined by genes and influenced by environment hormones Vellus hairs are soft fine hairs that cover the body surface Terminal hairs are heavy and pigmented head eyebrows pubic regions 5 8 Discuss the various kinds of glands in the skin and list the secretions of those glands Exocrine Glands in Skin Sebaceous Glands oil glands Holocrine glands Secrete sebum a mixture of triglycerides cholesterol proteins and electrolytes Two Types of Sweat Glands Apocrine glands Found in armpits around nipples and groin Secrete products into hair follicles begins at puberty Produce sticky cloudy secretions not for thermoregulation Break down of secretion by bacteria causes odors Surrounded by myoepithelial cells Squeeze apocrine gland secretions onto skin surface In response to hormonal or nervous signal Note even though these are named apocrine sweat glands they actually release their contents by merocrine mode of secretion Merocrine eccrine glands Watery secretions Widely distributed on body surface especially on palms and soles Coiled tubular glands Discharge directly onto skin surface Participates in sensible perspiration Water salts and organic compounds released Functions to Excrete water and electrolytes Cool skin Flush microorganisms and harmful chemicals from skin Types of Sebaceous Oil Glands Simple branched alveolar glands Associated with hair follicles Sebaceous follicles Are not associated with hairs They re found on face chest nipples and external genitalia Discharge directly onto skin surface Sebum contains lipids and other ingredients functions to Lubricate and protect the epidermis Inhibit bacteria Other Integumentary Glands Mammary glands Produce milk Ceruminous glands Produce cerumen earwax Protect the eardrum Control of Glands Autonomic nervous system ANS Controls sebaceous and apocrine sweat glands Works simultaneously over entire body Merocrine sweat glands Controlled independently Sweating occurs locally ex Sweaty palms etc Thermoregulation The main function of sensible perspiration Works with cardiovascular system Regulates body temperature 5 9 Describe the
View Full Document
Unlocking...