Chapter 5: The Integumentary System

integument layers

cutaneous layer (skin) & subcutaneous layer (under skin)

integumentary system

includes skin, hair, nails, skin glands, sensory receptors, etc.

integumentary system functions

- protection (against pathogens, water-loss, & UV rays)

- vitamin D production (calcitriol)

- temperature regulation (sweat glands & cutaneous blood flow)

- excretion & absorption of substances

- sensory information (sensory receptors give information about environment)

two components of cutaneous layer

epidermis & dermis

tissue in epidermis

keratinized stratified squamous epithelial tissue

tissue in dermis

dense (fibrous) irregular connective tissue

tissue in subcutaneous layer

areolar & adipose connective tissue

epidermis cells

keratinocytes, melanocytes, Langerhans cells (intrepidermal macrophages or dendritic cells), & Merkel cells (tactile epithelial cells)

keratinocytes

produces keratin, which protects skin and underlying tissue

melanocytes

produces melanin, which contributes to skin color & absorbs UV rays

Langerhans cells (intraepidermal macrophages or dendritic cells)

participate in immune response

Merkel cells (tactile epithelial cells)

detects touch sensations

# of layers in the epidermis

skin is composed of 4 or 5 layer (depends on if there is hair)

layers of the epidermis (superficial to deep)

stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, & stratum basale

layer of the epidermis only present in thick skin and never skin with hair

stratum lucidum

stratum basale

- deepest layer, composed of a single row of cuboidal or columnar keratinocytes that contain scattered keratin intermediate filaments

- stem cells undergo cell division to produce new keratinocytes

- melanocytes & tactile epithelial cells associated with tactile discs are scattered among the keratinocytes

stratum spinosum

- eight to ten rows of many-sided karetinocytes with bundles of keratin intermediate filaments

- contains armlike projections of melanocytes & Langerhans cells

stratum granulosum

- three to five rows of flattened keratinocytes, in which organelles are beginning to degenerate

- cells contain the protein keratohyalin, which converts keratin filaments into keratin, and lamellar granules, which release a lipid-rich, water-repellent secretion

stratum lucidum

- present only in skin of fingertips, palms, & soles

- consists of four to six rows of clear, flat dead keratinocytes with large amounts of orderly arranged keratin

stratum corneum

twenty-five to thirty rows of dead, flat keratinocytes that contain mostly keratin

dermis

- thicker than the epidermis

- supplied with blood vessels & nerves

two layers of dermis

papillary dermis & reticular dermis

papillary dermis

- superficial portion

- loose connective tissue with thin collagen & elastic fibers

- dermal papillae with blood capillaries, tactile corpuscles, & free nerve endings

reticular dermis

- deeper portion

- dense irregular connective tissue with thicker collagen & elastic fibers

- spaces contain adipose cells, hair follicles, nerves, sebaceous glands, and sudoriferous glands

subcutaneous layer

- storage of fat

- supplied with blood vessels and nerves

- contains lamellated corpuscles (sensory receptors)

accessory structures of the skin

hair, skin glands, & nails

hair shaft

superficial portion of hair

hair root

deep portion of hair

hair follicle

portion surrounding hair root; associated with sebaceous gland & arrector pili muscle

arrector pili muscle

small, involuntary muscle in base of hair follicle that causes hair to stand and goosebumps to appear

skin glands

sebaceous glands, sudoriferous glands, & modified sweat glands

sebaceous glands (oil gland)

- open into hair follicle

- secrete oil (sebum)

sudoriferous glands (sweat or eccrine glands)

- open into skin surface

- secrete sweat (water, NaCl, & urea)

- regulate body temperature

- remove waste

modified sweat glands (scent or apocrine glands)

- open into hair follicle

- secrete sweat as well as lipids & proteins

- stimulation during stress & sexual excitement

- axilla, genital, & groin regions

skin sensory nerve receptors

merkel cells, Meissner's corpuscle, Pacini's corpuscle, & free nerve endings

mechanoreceptors

sensory receptors that detects mechanical changes

mechanoreceptors in the skin

Merkel cells, Meissner's corpuscle, & Pacini's corpuscle

Merkel cells

sense touch

Meissner's (tactile) corpuscle

sense light touch

Pacini's (lamellated) corpuscle

sense vibration & pressure

free nerve endings of the skin

nociceptors & thermoreceptors

nociceptors

senses pain

thermoreceptors

detect heat or cold