Kaplan
MeSH
- Animal Scales [A17.100]
- Hair [A17.360]
- Nails [A17.600]
- Skin [A17.815]
BIOL235
- Integumentary system consists of the skin, hair, oil, and sweat glands, nails, and sensory receptors
- 5.1 Structure of the Skin, p. 150
- describe the layers of the epidermis and the cells that compose them.
- Epidermis
- Epidermal layer, from deep to superficial, are
- stratum basale,
- stratum spinosum,
- stratum granulosum,
- stratum lucidum (in thick skins only), and
- stratum corneum
- stem cells in the stratum basale undergo continuous cell division, producing keratinocytes for the other layers
- there are cells of types
- keratinocytes, melanocytes, intraepidermal macrophages,
- and tactile epithelial cells @@
- compare the composition of the papillary and reticular regions of the dermis.
- Dermis
- Dermis, composed of dense irregular connective tissue containing collagen and elastic fibers; divided into papillary and reticular regions; where the pigment is deposited with a needle in tattooing
- papillary region contains thin collagen and fine elastic fibers, dermal papillae, and corpuscles of touch
- reticular region contains bundles of thick collagen and some coarse elastic fibers, fibroblasts and macrophages, adipose tissue, hair follicles, nerves, sebaceous (oil) glands, and sudoriferous (sweat) glands
- Epidermal ridges provide the basis for fingerprints and footprints
- explain the basis for different skin colors.
- The structural basis of skin color
- Color of skin is due to melanin, carotene, and hemoglobin
- Subcutaneous layer, (hypodermis), deep to the dermis, not part of the skin, anchors the dermis to underlying tissues and organs, contains lamellated corpuscles
- the largest organ of the body in weight, of which the principal part are the epidermis (superficial) and dermis (deep)
- Keratinization and growth of the epidermis
- keratinization
- epidermal growth factor (EGF)
- 5.2 Accessory structures of the skin, p. 157
- contrast the structure, distribution, and functions of hair, skin glands, and nails.
- Hair
- Hair consists of
- a hair shaft (mostly superficial to the surface),
- a hair root (penetrates the dermis and sometimes the subcutaneous layer),
- and a hair follicle
- each hair follicle is associated with a sebaceous gland, an arrector pili muscle, and a hair root plexus
- New hairs develop from division of hair matrix cells in the hair bulb; its replacement and growth occur in a cyclical pattern consisting of growth, regression, and resting stages (3 stages)
- Hair offer a limited amount of protection from the sun, heat loss, and entry of foreign particles into the eyes, nose, and ears; function in sensing light touch
- Lanugo of the fetus is shed before birth
- Most body hair on males is terminal (coarse, pigmented) while most body hair on female is vellus (fine)
- Skin glands
- Sebaceous glands usually connected to hair follicles, absent from the palms and soles, produce sebum moistening hairs and waterproofs the skin; if clogged => produce acne
- Sudoriferous glands have 2 types
- eccrine sweat glands have an extensive distribution, whose ducts terminate at pores at the surface of the epidermis, involved in thermoregulation and waste removal, stimulated during emotional stress
- apocrine sweat glands, limited to the skin of the axillae, groin, areolae, whose ducts open into hair follicles, stimulated during emotional stress and sexual excitement
- Ceruminous glands, modified sudoriferous glands, secreting cerumen (soft yellow wax), found in external auditory canal (ear canal)
- Nails
- hard & dead keratinized epidermal cells over the dorsal surfaces of the distal portions of the digits, whose principal parts are
- the nail body, free edge, nail root, lunula,
- hyponychium, nail bed, eponychium, and nail matrix
- cell division of the nail matrix cells produces new nails
- Accessory structures of the skin including hair, skin glands, and nails, develop from the embryonic epidermis
- 5.3 Types of skin p. 163
- compare structural and functional differences in thin and thick skin. @@
- Thin skin covers all parts of the body except for the parts palms, palmar surfaces of the digits, and the soles covered by thick skins
- 5.4 Functions of the skin, p. 163
- describe how the skin contributes to the regulation of body temperature, storage of blood, protection, sensation, excretion and absorption, and the synthesis of vitamin D.
- Functions include body temperature regulation, blood storage, protection (as physical, chemical, and biological barriers), sensation, excretion and absorption, synthesis for vitamin D
- Thermoregulation
- The skin participates in the thermoregulation by liberating sweat at its surface, adjusting the flow of blood in the dermis
- Blood reservoir
- Cutaneous sensations
- Cutaneous sensations include tactile sensation, thermal sensations, and pain
- Excretion and Absorption
- Synthesis of Vitamin D
- Synthesis of vitamin D requires activation of a precursor molecule in the skin by ultraviolet rays in the sunlight.
5.5 Maintaining homeostasis: skin wound healing, p. 165