Chapter at A Glance

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Anatomy and Physiology

Key Terms

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.

Specialties/Specialists

The study of the skin, hair, and nails is called dermatology. A dermatologist is one who specializes in this area.

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).

Accessory Structures

Glands

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.

Hair

Hair has its roots in the dermis; these roots, together with their coverings, are called hair follicles (FALL ih kuls). The visible part is called the hair shaft. Underneath the follicle is a nipple-shaped structure that encloses the capillaries called the papilla (pah PILL ah) (pl. papillae). Epithelial cells on top of the papilla are responsible for the formation of the hair shaft. When these cells die, hair can no longer regenerate, and hair loss occurs. The main function of hair is to assist in thermoregulation by holding heat near the body. When cold, hair stands on end, holding a layer of air as insulation near the body (piloerection).

Nails

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.

eponychium

 epi- = above

 onych/o = nail

 -ium = structure

paronychium

 par- = near

 onchy/o = nail

 -ium = structure

 Be Careful!

Don’t confuse papill/o, meaning papilla or “nipple” and papul/o, which means pimple.

 You can review the anatomy of the integumentary system by clicking on Body Spectrum Electronic Anatomy Coloring Book → Integumentary.

 Exercise 1: Anatomy and Physiology

Match the integumentary term to its combining form.

Decode the terms:

 Exercise 2: The Skin

Label the structures of the skin with their anatomic terms and combining forms where appropriate.

Todd Feldman is a 38-year-old carpenter. One day, he is working on a house when he accidentally hits the middle finger of his right hand with his hammer. It swells immediately and is very painful. He goes to the ED to have it checked out. The ED doctor orders an x-ray, which shows that the top of the finger is crushed. The nail is also damaged. A hand surgeon examines Todd and tells him that he needs surgery on his finger to remove the nail and the tip of the bone.

Surgery is scheduled for the next day and proceeds without incident. He is sent home with instructions for wound care and dressings. Six months later, Todd’s nail has grown back partially and he has regained full dexterity of the finger.

 Exercise 3: Operative Report

Using the above operative report, answer the following questions:

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).
sist
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.
plack
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  cm, such as an insect bite. If larger than  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.
wheel

 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.

 Exercise 5: Dermatitis and Bacterial Infections

Fill in the blank.

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