Ch. 5 The Integumentary System

Parts of the integumentary system

skin, hair, nails, sweat/oil glands

Skin

- largest organ

- accounts for 7% of body weight

- varies in thickness from 1.5-4.4 mm

2 layers of skin

epidermis and dermis

hypodermis

the layer of skin beneath the dermis, which serves as a storage repository for fat

skin structure

function of skin and hypodermis

- cushions and insulates deeper organs

- protects body from bumps, scrapes, and cuts

- protects body from chemicals, heat, and cold

- acts as a mini-excretory system

- produciton of vitamin D (calcium absorption for strong bones)

- contains sensory receptors associated with nerve endings

what are the 4 main cell types in the epidermis

- Keratinocytes

- Melanocytes

- Tactile (Merkel) cells

- Dendritic (Langerhans) cells

melanocytes

produce melanin

tacticle epithelial cells (Merkel cells)

sense of touch

dendritic cells (langerhans cells)

immune system

keratinocytes

most abundant cell type in epidermis

function of keratinocytes

- arise from deepest layer of epidermis

- produce keratin: a tough fibrous protein

- produce antibodies and enzymes

- dead at skin's surface

layers of epidermis from deepest to shallowest

stratum basale (stratum germinativum), stratum spinosum, stratum granulosum, stratum lucidum (only in thick skin), stratum corneum

stratum basale

- deepest layer of epidermis

- attached to underlying dermis

- cells actively divide

- contains keratinocytes merkel cells (sensory nerve ending), melanocytes (secrete melanin)

melanin in stratum basale

leaves melanocytes and goes into keratinocytes to get between the nucleus and UV rays to protect nucleus

stratum spinosum (spiny layer)

- "spiny" appearance caused by artifacts of histological preparation

- contains keratinocytes

- contains star-shaped dendritic cells which are are type of macrophage

- uses endocytosis to engulf and dispose

stratum granulosum

- keratinocytes

- keratohyaline granules: contain a waterproofing glycolipid which prevents water loss

- skin gets tougher as layer gets more superficial

Stratum lucidum (clear layer)

- occurs only in thick skin

- composed of a few rows of flat, dead keratinocytes

Stratum corneum (horny layer)

- thick layer of dead keratinocytes and thickened plasma membranes

- protects skin against abrasion and penetration

- callus: stratum corneum getting thicker

dermis

- second major layer of the skin

- strong, flexible connective tissue

- richly supplied with blood vessels and nerves

what are the 2 layers of the dermis

Papillary layer- includes dermal papillae

Reticular layer- deeper layer (80% of thickness of dermis)

lines and ridges of the hand

- friction ridges

- openings of sweat gland ducts

- finger prints

dermal papillae

increase surface area between dermis and epidermis, diffusion, reduce risk of blisters

hypodermis

- deep to the skin also called (superficial fascia)

- contains areolar and adipose connective tissues

- anchors skin to underlying structures

- helps insulate the body

what are the 3 pigments that contribute to skin color

melanin (most important), Carotene, hemoglobin

carotene

yellowish pigment from carrots and tomatoes

hemoglobin

caucausin skin contains little melanin, allows crimson color of blood to show through