Integumentary System

Integumentary System

Functions of the Integumentary System

The most important function of the skin (integument) is that it acts as the first line of defense in protecting the body from disease by providing an external barrier. It also helps regulate the temperature of the body, provides information about the environment through the sense of touch, assists in the synthesis of vitamin D (essential for the normal formation of bones and teeth), and helps eliminate waste products from the body. It is the largest organ of the body and accomplishes its diverse functions with assistance from its accessory structures, which include the hair, nails, and two types of glands: sebaceous (oil) and sudoriferous (sweat). Any impairment of the skin has the potential to lessen its ability to carry out these functions, which can lead to disease.

Anatomy and Physiology


The skin is composed of two layers: the epidermis (eh pih DUR mis), which forms the outermost layer, and the dermis or corium (KORE ee um), the inner layer (Fig. 4-1). The dermis is attached to a layer of connective tissue called the hypodermis or the subcutaneous (sub kyoo TAY nee us) layer, which is mainly composed of fat (adipose tissue).


The top layer, the epidermis, is composed of several different layers, or strata, (sing. stratum) of epithelial (eh pih THEE lee ul) tissue. Epithelial tissue covers many of the external and internal surfaces of the body. Because the type of epithelial tissue that covers the body has a microscopic scaly appearance, it is referred to as stratified squamous epithelium (SKWAY muss eh pih THEE lee um) (squamous means scaly).

Although there is a limited blood supply to the epidermis (it is avascular [a VAS kyoo lur]—that is, it contains no blood vessels), constant activity is taking place. New skin cells are formed in the basal (BAY sul) (bottom) layer of the epidermis, the stratum germinativum (STRAY tum jur mih nuh TIH vum). This layer is also the site where melanin (pigment) is produced by cells called melanocytes. When the skin is exposed to ultraviolet light, the melanocytes secrete more melanin. Birthmarks, age spots, and freckles result from the clumping of melanin. Individuals have different skin colors because of varying numbers of melanocytes in the basal layer of the skin. The new cells move outward toward the stratum corneum (top layer). During the transition from the lowest layer to the outer layer, these cells are then called keratinocytes because they are filled with keratin (KAIR ah tin), which is a hard protein material. The nature of the keratin adds to the protective nature of the skin, giving it a waterproof property that helps retain moisture within the body.

Accessory Structures


The sudoriferous (soo dur IF uh rus), or sweat, glands are located in the dermis and provide one means of thermoregulation for the body. They secrete sweat through tiny openings in the surface of the skin called pores. The secretion of sweat is called perspiration. These glands are present throughout the body but are especially abundant in the following areas: the soles of the feet, the palms of the hands, the armpits or axillae (sing. axilla), the upper lip, and the forehead.

The sebaceous (seh BAY shus) glands secrete an oily, acidic substance called sebum (SEE bum), which helps to lubricate hair and the surface of the skin. The acidic nature of sebum is key in inhibiting the growth of bacteria.


Nails cover and thus protect the dorsal surfaces of the distal bones of the fingers and toes (Fig. 4-2). The part that is visible is the nail body (also called the nail plate), whereas the nail root is in a groove under a small fold of skin at the base of the nail. The nail bed is the highly vascular tissue under the nail that appears pink when the blood is oxygenated or blue/purple when it is oxygen deficient. The moonlike white area at the base of the nail is called the lunula (LOON yoo lah), beyond which new growth occurs. The small fold of skin above the lower part of the nail is called the cuticle (KYOO tih kul) or eponychium (eh puh NICK ee um). The paronychium (pair ih NICK ee um) is the fold of skin that is near the sides of the nail.

Fig. 4-2 The nail.

image Exercise 3: Operative Report

Using the above operative report, answer the following questions:


Skin Lesions

A skin lesion (LEE zhun) is any visible, localized abnormality of skin tissue. It can be described as either primary or secondary. Primary lesions (Fig. 4-3) are early skin changes that have not yet undergone natural evolution or change caused by manipulation. Secondary lesions (Fig. 4-4) are the result of natural evolution or manipulation of a primary lesion.

Terms Related to Primary Skin Lesions

Term Word Origin Definition
cyst cyst/o sac, bladder Nodule filled with a semisolid material, such as a keratinous or sebaceous cyst (see Fig. 4-3, A).
ecchymosis (pl. ecchymoses) ec- out
chym/o juice
-osis abnormal condition
Hemorrhage or extravasation (leaking) of blood into the subcutaneous tissue. The resultant darkening is commonly described as a bruise (see Fig. 4-3, B).
eck ih MOH sis
hematoma hemat/o blood
-oma mass
Collection of extravasated blood trapped in the tissues and palpable to the examiner, such as on the ear. (see Fig. 4-3, C).
hee mah TOH mah
macule macul/o spot Flat blemish or discoloration less than 1 cm, such as a freckle, port-wine stain, or tattoo (see Fig. 4-3, D).
MACK yool
nodule nod/o knot
-ule small
Palpable, solid lesion less than 2 cm, such as a very small lipoma (see Fig. 4-3, E).
NOD yool
papule papul/o pimple Raised solid skin lesion raised less than 1 cm, such as a pimple (see Fig. 4-3, F).
PAP yool
patch   Large, flat, nonpalpable macule, larger than 1 cm.
petechia (pl. petechiae)   Tiny ecchymosis within the dermal layer.
peh TEEK ee ah
plaque   Raised plateaulike papule greater than 1 cm, such as a psoriatic lesion or seborrheic keratosis.
purpura purpur/o purple
-a noun ending
Massive hemorrhage into the tissues under the skin.
PUR pur ah
pustule pustul/o pustule Superficial, elevated lesion containing pus that may be the result of an infection, such as acne (see Fig. 4-3, G).
PUS tyool
telangiectasia tel/e far
angi/o vessel
-ectasia dilation
Permanent dilation of groups of superficial capillaries and venules.
tell an jee eck TAY zsa
tumor   Nodule more than 2 cm; any mass or swelling, including neoplasms.
TOO mur
vesicle vesicul/o blister or small sac Circumscribed, elevated lesion containing fluid and smaller than image cm, such as an insect bite. If larger than image cm, it is termed a bulla. Commonly called a blister. (see Fig. 4-3, H).
VESS ih kul
wheal   Circumscribed, elevated papule caused by localized edema, which can result from a bug bite. Urticaria, or hives, results from an allergic reaction.


image Exercise 4: Skin Lesions

Match the primary lesions with their definitions.

Match the smaller version of a primary skin lesion with the larger version.

Match the secondary lesions with their definitions.

Terms Related to Dermatitis and Bacterial Infections

Term Word Origin Definition
atopic dermatitis a- no, not, without
top/o place, location
-ic pertaining to
dermat/o skin
-itis inflammation
Chronic, pruritic superficial inflammation of the skin usually associated with a family history of allergic disorders.
a TOP ick
dur mah TYE tis
cellulitis cellul/o cell
-itis inflammation
Diffuse, spreading, acute inflammation within solid tissues. The most common cause is a Streptococcus pyogenes infection (Fig. 4-6).
sell yoo LYE tis
contact dermatitis dermat/o skin
-itis inflammation
Irritated or allergic response of the skin that can lead to an acute or chronic inflammation (Fig. 4-7).
eczema   Superficial inflammation of the skin, characterized by vesicles, weeping, and pruritus. Also called dermatitis.
ECK suh muh
folliculitis follicul/o follicle
-itis inflammation
Inflammation of the hair follicles, which may be superficial or deep, acute or chronic.
foh lick yoo LYE tis
furuncle   Localized, suppurative staphylococcal skin infection originating in a gland or hair follicle and characterized by pain, redness, and swelling. If two or more furuncles are connected by subcutaneous pockets, it is termed a carbuncle (Fig. 4-8).
FYOOR ung kul
impetigo   Superficial vesiculopustular skin infection, normally seen in children, but possible in adults (Fig. 4-9).
im peh TYE goh
pilonidal cyst pil/o hair
nid/o nest
-al pertaining to
Growth of hair in a cyst in the sacral region.
pye loh NYE duhl
pruritus   Itching.
proo RYE tuss
seborrheic dermatitis seb/o sebum
-rrheic pertaining to discharge
dermat/o skin
-itis inflammation
Inflammatory scaling disease of the scalp and face. In newborns, this is known as cradle cap.
seh boh REE ick


image Exercise 5: Dermatitis and Bacterial Infections

Fill in the blank.

Oct 6, 2017 | Posted by in GENERAL SURGERY | Comments Off on Integumentary System
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