INTEGUMENTARY
SYSTEM
A. THE SKIN-STRUCTURE
1. The skin is an organ which consists of several types of tissues and performs specific activities.
2. The tissues comprising the skin are the epithelium of the EPIDERMIS and the connective tissues of the
DERMIS.
3. The two principal layers of the skin are the epidermis and the dermis.
B. THE EPIDERMIS
1. The epidermis is composed of keratinized stratified squamous epithelium and contains several cell
types.
2. The CELL TYPES found in the epidermis are KERATINOCYTES, MELANOCYTES, LANGERHANS’ CELLS, and
MERKEL CELLS.
3. The epidermis is organized into five DISTINCT LAYERS. These are the STRATUM BASALE, STRATUM
SPINOSUM, STRATUM GRANULOSUM, STRATUM LUCIDUM, and STRATUM CORNEUM.
4. The skin is capable of regeneration.
C. THE DERMIS
1. The DERMIS consists of two distinct regions. The superficial part is composed of areolar, connective
tissue and fine elastic fibers; and the deeper part is composed of dense irregular connective tissue
plus collagenous and elastic fibers.
2. The outer layer contains nerve endings for touch, thermal sensations, pain, tickling, and itching.
3. SKIN COLOR is due to MELANIN in the epidermis, CAROTENE in the dermis, and blood (HEMOGLOBIN) in
the capillaries of the dermis.
4. MALIGNANT MELANOMA, (cancer of the melanocytes), is a particularly serious skin cancer. Liver, or age
spots, are non-cancerous clusters of melanin.
D. ACCESSORY ORGANS OF THE SKIN
1. The accessory organs of the skin include HAIR, GLANDS, and NAILS.
2. HAIR is distributed variously over the body where it functions in protection. Each hair is composed of a
SHAFT and a ROOT. Surrounding the root is the HAIR FOLLICLE, which is composed of two layers of
epidermal tissue.
3. The base of each follicle is enlarged into an onion-shaped structure, the BULB.
E. GLANDS
1. Accessory glands of the skin include SEBACEOUS (OIL), SUDORIFEROUS (SWEAT), AND CERUMINOUS
(WAX) GLANDS.
2. SEBACEOUS GLANDS, with few exceptions, are associated with the hair follicle and secrete an oily
substance called SEBUM which prevents skin dryness, water evaporation, keeps the skin soft, and
inhibits the growth of certain bacteria.
3. Blackhead or pimples represent enlargement of the sebaceous glands due to unreleased quantities of
sebum.
4. SUDORIFEROUS GLANDS, or SWEAT GLANDS, can be divided into APOCRINE GLANDS and ECCRINE GLANDS.
5. APOCRINE GLANDS are found in the armpit, groin, the pigmented area of the breasts, and bearded area
of the face.
6. ECCRINE GLANDS are found throughout the skin except the lips, nail beds, eardrums, glans penis,
glans clitoris, and labia minora.
7. CERUMINOUS glands are modified sudoriferous glands present in the external ear. They produce a
sticky substance called CERUMEN (earwax) which provides a barrier against foreign bodies.
F. NAILS
1. NAILS are plates of hard-keratinized epidermal cells over the dorsal surfaces of the terminal portions of
the fingers and toes.
2. Functionally, nails help us grasp and manipulate small objects, and protect the ends of the fingers and
toes.
G. THE FUNCTIONS OF THE SKIN
1. The skin exhibits numerous functions. These include:
 Regulation of body temperature
 Protection
 Cutaneous Sensation
 Excretion and Absorption
 Synthesis of Vitamin D
H. AGING AND THE INTEGUMENTARY SYST
1. Most age related changes occur in the dermis.
2. Collagen fibers in the dermis decrease in number, stiffen and break apart.
3. Elastic fibers lose some elasticity, thicken into clumps leading to the formation of wrinkles.