Chapter 6

Integumentary System

OrganAn organ consists of two or more types of tissues grouped together that perform a specialized task.

Integumentary System Includes the skin plus accessory structuresSkin is the largest organ in our body

Functions of skin include1. Forms protective coating

2. Retards water loss

3. Vitamin D synthesis

4. Temperature control

5. Houses sensory receptors

The skin is composed of 2 layers 1. Epidermis

2. Dermis

The subcutaneous layer (hypodermis) lies beneath the skin, but is not considered part of the skin.

EpidermisOutermost layer of skin

Stratified squamous epithelium

Outermost layers are keratinized

No direct blood supply – Receives nutrients by diffusion

There are five (5) layers of the epidermis: Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale

Stratum corneumIs the outermost layer of epidermisComposed of tightly packed dead cellsCells are keratinized

Keratin = water insoluble protein

Stratum basaleDeepest layer of epidermisCells are nourished by dermal blood vesselsSite of cell growth and divisionStratum Basal contains Melanocytes

Layers of the epidermis

MelanocytesSecrete melanin – pigment

Number of melanocytes is similar in all people

Darker skin from darker and larger melanin granules

Albinism – mutation resulting in no melanin production

Figure 6.4a A melanocyte with melanin granules

Figure 6.5 The red eyes and pale skin reflect the lack of melanin in albinism.

DermisDeeper layer of skinComposed of dense irregular connective tissueContains dermal papillaeBlood vessels and nervesHair folliclesSweat glands and Sebaceous glands

Figure 6.2 Section of skin

Sweat Glands - secrete sweat onto surface of the skinEccrine glands – respond to elevated temperaturesApocrine glands - anxiety, sexual arousal, and pain

Sebacous glandsAssociated with hair folliclesSecretes Sebum – oilKeeps hair and skin soft and waterproof

Subcutaneous layer (often called hypodermis)Subcutaneous layer – not part of skin

Comoposed of adipose tissue, areolar tissue, and blood vessels

The subcutaneous layer binds skin to underlying organs

Adipose insulates the body

End of Chapter 6