Integumentary System Notes Unit 3 Tissues, Membranes and Integumentary System

Anatomy Epidermis (outside) Skin Dermis (inside) Subcutaneous layer or hypodermis

Epidermis Stratum basale (stratum germinativum) Innermost layer Reproduce themselves & allow the skin to repair itself Stem cells that produce keratin Tough waterproof material, provides cells in outer layer with a protective quality Melanocytes - # the same for all races, concentration is different Melanin produced in a melanosome

Stratum spinosum (thorn- like, prickly) 8-10 layers attached by desmosomes See spines when cell is stained for microscopy Keratinocytes take in melanin by cytocrine secretion

Stratum granulosum 3-5 layers Keratinization begins here Keratohyalin found in granules Cells beginning to die

Stratum lucidum (lucid = clear) More apparent in thick skin 3-5 layers of clear cells Eleidin Stratum corneum (corneum means horny) Dead, flat cells full of keratin Keratin is waterproof Cells are shed Basal cell to surface – about 2-4 weeks

Skin color Same number of melanocytes Albinism Uv light or x-rays Genetic factors Same number of melanocytes Albinism Environmental factors Uv light or x-rays

Physiological factors Amount of blood Amount of oxygen Cyanosis Carotene accumulation Jaundice – liver disorder

Dermis Deeper & thicker than the Epidermis Connective tissue layer, cells scattered far apart Collagen and elastic fibers Papillary layer 1/5 of dermis – loose areolar connective tissue Highly vascular Dermal papillae - fingerprints Wrinkles develop as the skin loses elasticity and sags

Reticular (net) layer Dense irregular connective tissue Sebaceous (oil) glands Hair follicles Ducts of sudoriferous (sweat) glands Striae or stretch marks Nerves and nerve endings to sense pain, pressure, touch, and temperature

Hypodermis Attaches the reticular layer to the underlying organs Loose connective tissue and adipose tissue Major blood vessels – rete cutaneum

Appendages of the Skin Hairs Epidermal growths that function in protection Shaft, root, and follicle Soft newborn hair is called lanugo Arrector pili muscle – “erectors of the hair” Sebaceous glands – secrete oil

Receptors Meissner’s corpuscle – located close to the skin surface, detects light touch Pacinian corpuscle – deep in the dermis, detects pressure on the skin surface

Nails Plates of highly packed, keratinized cells Protection, scratching, & manipulation Formed by cells in nail bed called the matrix ( in area of lunula) 1 mm / week

Skin Glands Sebaceous (oil) glands Sweat (sudoriferous) glands Usually connected to hair follicles Moistens hair and waterproofs skin Sweat (sudoriferous) glands Eccrine sweat glands – most numerous Secrete Water, salt, wastes Function is to cool the body (also nervous) -Apocrine sweat glands Associated with hair follicles More viscous – fatty acids and proteins Odor occurs when broken down by bacteria

Ceruminous glands Modified sudoriferous glands Secrete cerumen (ear wax) Mammary glands Secrete milk