Skin=Integument Skin + accessory organs (hair, nails,

and cutaneous glands)= Integumentary system

Lgst. organ

Epidermis: Stratified squamous epithelium; outer layer is "keratinized" or "cornified"

Dermis:Dense irregular connective tissue

Hypodermis:Adipose connective tissue (technically not part of system

Three Layers of skin:

Stratum Corneum = Many layers of flat, dead, scale-like cells full of keratin

Stratum Lucidum = One or two layers of dying cells

Stratum Granulosum = Three or four layers of cells; Actively synthesizing protein keratinStratum Spinosum (malphigian layer) = Three or four layers of cells with Some cell division

Stratum Basale (st germinatum) = Single row of dividing cells (columnar cells )

(Epidermis)

Primary cell type in epidermis = keratinocytes which produce large amounts of protein keratin

Other cell types:

Melanocytes produce pigment melanin & transfer it to keratinocytes

Langerhans cells (immune cells) protect against pathogens and toxins

Merkel cells detect touch and pressure; transfer this information to sensory receptors in the dermis

Dermis:

Dense irregular connective tissue

Separated from epidermis (stratified squamous epithelium) by basement membrane

Highly vascular

Highly innervated

Two Layers:

Papillary layer just below epidermis

Reticular layer forms deep 80%

Dermis:

Contains many types of sensory receptors for touch, pressure, vibration, pain, temperature, etc.

Some = simple nerve endings

Others = complex structures with multiple cell types

Appendages of the skin

Hair follicles and hairSweat glandsSebaceous (oil) glandsNails on fingers and toes

All begin as epidermis of embryo; grow down into dermis

Hair

- Distribuled over all skin except: palms of hands soles of feet nipples glans of penis & clitoris minor labia

- Formed in follicles located deep in dermis

- Consists of layers of dead, highly keratinized keratinocytes

Trunk and limb hair considered vestigial Scalp only place where it is thick

enough to retain heat Eyebrows enhance facial features Vibrassae (guard hair) are used to filter

particulates from the ear and nose

Shaft

Bulb

Root

Each hair is associated with:

One or more sebacious (oil) glands

An arrector pili muscle

A plexus of nerves aroundthe root

Sweat Glands

- 2 to 3 million

- Two types: Merocrine: Distributed over all skin except nipples (Eccrine) Simple coiled glands in dermis Duct leads to sweat pore on surface Secreted watery sweat for cooling Apocrine: Located only in axillary, pubic, anal regions Larger than eccrine glands Duct opens into opening of hair follicle Secretes thicker sweat, high content of proteins and fats. Contains specific scent molecules: sexual, fear, etc.

Sweat is usually 99% water with a pH between 4 and 6

Sweat glands produce 500ml of insensible perspiration (no noticable wetness)daily

Diaphoresis—sweating with wetness (up to 1 l per hr when exercising or in heat)

Two specially modified sweat glands:

Ceruminous—found in the external ear canal. Secretion combines with sebum and dead epidermal cells to form earwax (keeps eardrum pliable, canal waterproof and has a bactericidal effect)

Mammary --milk producing glands found in the female breast (modified apocrine glands)

Sebaceous (oil) glands:

- Branched tubular glands

- Duct opens into opening of hair follicle

- Secretes sebum, consisting of lipids, proteins, ions, carbohydrates,

Functions of Integumentary System (skin & its products)

Barrier to keep water and solutes in

Barrier to keep bacterial, dirt, etc. out

Protection against abrasion

Contains sensory receptors for touch, temperature, pressure, pain, etc.

Temperature regulation via hair, sweat, & amount of blood flow

Blood reservoir

Synthesis of vitamin D

Excretion