HOME > 4.2 - Structures of the Integumentary System

4.2 - Structures of the Integumentary System

The integumentary system includes the cutaneous membrane (skin) and its accessory organs and structures. It is the protective, waterproof, self-repairing, insulating, cushioned, elastic covering for the outside of the body of humans and other mammals.

The integumentary system consists of three major layers: the superficial epidermis, the dermis and the hypodermis, which is the deepest of the three layers.

Major layers:

Epidermis

• Stratified squamous epithelium
• Keratinocytes in the upper layers produce the tough, fibrous protein keratin
• Cells in the basal layer reproduce quickly to replace damaged upper layers

Dermis

• Dense connective tissue.
• Areas containing a large number of blood vessels appear reddish due to the presence of hemoglobin in the blood.

Hypodermis

• Subcutaneous tissue; mostly adipose (fatty) tissue, may contain carotene deposits
• Anchors the skin to underlying tissues

Layers

Epidermis (outside in):

Stratum corneum

• Flattened, dead cells filled with keratin; can also contain carotene deposits

Stratum lucidum

• Flattened, dead cells filled with keratin; only present in hairless areas of skin

Stratum granulosum

• Flattened, keratinized cells

Stratum spinosum

• Flattened, keratinized cells; form a wavy layer that is shaped by the projections from the dermis

Stratum basale

• Rapidly producing cells that replenish the upper epidermal layers
• Contains melanocytes that produce melanin pigments that are stored in melanosome granules

Dermis

Papillary layer

• Wavy layer of dermal papillae that project into the epidermis
• Contains capillaries that nourish the epidermis, pain receptors and touch receptors.
• Patterns of papillae form the ridges for fingerprints and toe prints

Reticular layer

• Larger capillaries and cutaneous blood vessels
• Sebaceous glands (oil glands) produce sebum, a mixture of oil and cell debris to lubricate skin and hair and to kill bacteria
• Sudoriferous glands (sweat glands) produce sweat, a watery solution of salts, vitamin C and metabolic wastes. Sweat glands can be eccrine or apocrine.
• Epocrine sweat glands are important in temperature regulation, secreting fluid when body temperature is high
• Apocrine sweat glands empty their secretions, which contain fatty acids and proteins, into hair follicles. Bacteria grow using the secretions of apocrine sweat glands, giving apocrine secretions their distinctive odor.
• Hairs are produced in by hair follicle cells, and grow from the root to the shaft. The arrector pili smooth muscles connect the sides of the hair follicle to the dermal tissue, and can contract to make hairs stand upright.
• Meissner’s corpuscle – touch receptor
• Free nerve endings – pain receptors
• Pacinian corpuscles – deep pressure receptors

Activity 4.2 - Structures of the Integumentary System

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