Skin Integument  Body’s outer covering Body’s largest organ (over 9 pounds)

Skin Functions Prevents dehydration; infectionPrevents dehydration; infection Produces Vitamin DProduces Vitamin D Regulates Body TemperatureRegulates Body Temperature Dermis has 10% of body’s blood vesselsDermis has 10% of body’s blood vessels Blood vessels in dermis

Layers of Skin Epidermis Made of keratinocytes; produce the protein keratinMade of keratinocytes; produce the protein keratin Outer skin cells are dead & flattenedOuter skin cells are dead & flattened Deeper layer of epidermis contains melanocytes, contain pigmentsDeeper layer of epidermis contains melanocytes, contain pigments

Layers of the Skin Dermis Protects internal structures in the bodyProtects internal structures in the body Made of Dense Irregular Connective TissueMade of Dense Irregular Connective Tissue Some epithelial cells (hair follicles)Some epithelial cells (hair follicles) Nervous Tissue (receptors)Nervous Tissue (receptors) Blood vesselsBlood vessels Nutrients diffuse throughNutrients diffuse through bloodstream through dermis Glands, fingernails & hair folliclesGlands, fingernails & hair follicles originate in dermal tissue

Accessory Organs of the Skin Hair follicles: rooted in the dermis, extend through epidermis Arrector Pili muscles give us goose bumps Pigment: melanin gives our skin its color

Accessory Organs of the Skin Merocrine Glands (Sweat Glands) Found in armpits, palms of hands, and forehead Originate in dermis Used to regulate body temperature

Accessory Organs of the Skin Sebaceous Glands (Oil Glands) Found everywhere on the body (except on palms and feet) Oil softens hair follicles & kills bacteria In acne, oil glands become infected with bacteria, skin becomes inflamed

Accessory Organs of the Skin Apocrine Glands (A Type of Sweat Gland) Glands that connect into the ducts of hair follicles Secreted in response to stress and emotion Odorous secretions Found in armpits and groin

Regulation of Body Temperature When body temperature is low Hypothalamus signals glands on skin to decrease sweat productionHypothalamus signals glands on skin to decrease sweat production If body temperature is still lowIf body temperature is still low Hypothalamus signals muscles of the skin to shiverHypothalamus signals muscles of the skin to shiver This brings blood to surfaceThis brings blood to surface of skin, warming the body

Regulation of Body Temperature If body temperature is high Hypothalamus signals glands on skin to increase sweat productionHypothalamus signals glands on skin to increase sweat production That water must be replaced!That water must be replaced! If not, heat exhaustion/heat strokeIf not, heat exhaustion/heat stroke