Integumentary System

Functions of the Skin

-protection of the body from environmental effects

-containment for the body’s structures and vital substances, preventing dehydration

-thermal regulation through evaporation of sweat and/or dilation or constriction of superficial blood vessels

-sensation by way of superficial nerves and sensory endings

-synthesis and storage of vitamin D

Epidermis

-keratinized epithelium that has a tough, horny superficial cellular layer

-protective outer layer on top of the regenerative and pigmented basal layer

-no blood vessels or lymphatics (avascular)

• epidermis is vascularized by the underlying dermis

Dermis

-deep connective tissue layer

-dense layer of interlacing collagen and elastic fibers

• tension lines

-supplied by arteries that enter this deep surface to form a cutaneous plexus of anastomosing arteries

• AKA: arteries form a network where they form a connected web and branch out in the dermis

-most afferent nerve endings are in the dermis, a few are penetrate the epidermis

-contains hair follicles with associated smooth erector muscles and sebaceous glands

Other Skin Structures

-nails

-mammary glands

-tooth enamel

Deep Fascia

-deep layer underlying the dermis

Subcutaneous Tissue

-AKA: superficial fascia

-composed of loose connective tissue and stored fat; provides most of the body’s fat storage

- between the dermis and deep fascia

-contains sweat glands, superficial blood vessels, lymphatic vessels, and cutaneous nerves

-cutaneous nerves and superficial vessels course in the subcutaneous layer, only their nerve endings reach up to the dermis and epidermis

-participates in thermoregulation (retains/insulates heat in the body’s core)

-provides padding that protects the skin from compression by bony prominences

Skin Ligaments

-numerous small fibrous bands extending through the subcutaneous layer to connect the deep layer of the dermis to the underlying deep fascia

-where ligaments are longer and sparse → more skin mobility (ex. back of hand)

-where ligaments are shorter and more abundant → less skin mobility, firm attachment to deep fascia (ex. palm)

Skin Color Signs in Physical Diagnosis

-skin injury may cause the superficial capillary beds to become engorged, making the skin look abnormally red (erythema)

• Ex. exposure to heat, infection, inflammation, allergic reaction

-jaundice: certain liver disorders cause bilirubin to build up in the blood, giving skin and eyes a yellow color

-examination of the underside of the tongue can help detect skin color change-causing diseases in darker-skinned people