Page 191 - Fundamentals of anatomy physiology

178 Unit 2 Support and Movement

5 2. The accessory structures include hair, exocrine glands, and Excretion of salts, water, and organic wastes by integumen-
nails. They are located primarily in the dermis and pro-
trude through the epidermis to the skin surface. tary glands.

The integument does not function in isolation. An exten- Maintenance of normal body temperature through either
sive network of blood vessels branches through the dermis.
Sensory receptors monitor touch, pressure, temperature, and insulation or evaporative cooling, as needed.
pain, providing valuable information to the central nervous
system about the state of the body. Production of melanin, which protects underlying tissue

Deep to the dermis is the loose connective tissue of the from ultraviolet radiation.
hypodermis, also known as the superficial fascia or subcutane-
ous layer. The hypodermis separates the integument from the Production of keratin, which protects against abrasion
deep fascia around other organs, such as muscles and bones.
and serves as a water repellent.
p. 165 Although the hypodermis is often considered sepa-
rate from the integument, we will consider it in this chapter be- Synthesis of vitamin D3, a steroid that is converted to calcitriol,
cause its connective tissue fibers are interwoven with those of
the dermis. a hormone important to normal calcium metabolism.

The general functions of the integumentary system are Storage of lipids in adipocytes in the dermis and in adipose
summarized in Figure 5–2 and include:
tissue in the hypodermis (subcutaneous layer).
Protection of underlying tissues and organs against impact,
Detection of touch, pressure, pain, vibration, and tem-
abrasion, fluid loss, and chemical attack.
perature stimuli and the relaying of that information to
the nervous system. (We will consider these general senses,
which provide information about the external environ-
ment, in Chapter 15.)

Coordination of immune response to pathogens and can-

cers in the skin.

Figure 5–2 The Cutaneous Membrane and Accessory Structures.

Integumentary System

FUNCTIONS • Physical protection from • Coordination of immune • Sensory information • Excretion
environmental hazards response to pathogens • Synthesis of vitamin D3 • Thermoregulation
and cancers in skin
• Storage of lipids

Cutaneous Membrane Accessory Structures

Epidermis Dermis Hair Follicles Exocrine Glands Nails

Protects the dermis, Papillary Layer Reticular Layer Hairs protect skull Assist in Protect and
prevents water loss and and provide temperature support tips
the entry of pathogens, Nourishes and Has sensory receptors delicate touch regulation and of fingers
and synthesizes vitamin supports that detect touch, sensations on waste excretion and toes
D3. Sensory receptors epidermis pressure, pain, vibration, general body
detect touch, pressure, and temperature. Blood surface
pain, and temperature vessels assist in
thermoregulation