Dermis and Hypodermis. Dermis zLies deep (beneath the epidermis) zProvides strength and elasticity...

Dermis and Hypodermis

Dermis

Lies deep (beneath the epidermis)Provides strength and elasticity to the

skinCreates framework to support the

accessory structuresMade of 2 layers

Papillary Layer

Made of areolar tissueContains capillaries and sensory neurons

that serve the epidermis aboveThe top of this layer has dermal papillae

that connect to the dermal ridges of the stratum germinativum

Reticular Layer

Made of a mesh of dense irregular connective tissue w/ lots of collagen and elastin protein fibers

Contains hair follicles, sweat glands, oil glands, blood vessels and nerves

The collagen and elastic fibers allow the skin to stretch and change shape

Skin Damage

Aging, hormones, and UV radiation can all damage and reduce the amount of elasticity of the skin causing wrinkles and sagging

Hypodermis/Subcutaneous

Fibers of the reticular layer extend into the subcutaneous layer so there isn’t a distinct line between the two

Made of areolar and adipose tissueStabilizes skin while allowing movementAreas of subcutaneous fat change during

a person’s lifeLocation of injections

Accessory Structures/ Hair follicles and hair

Human body has appox. 5 million hairs and 98% of them are on the general body not on the head

Hair bulb- bottom of hair surrounded by epithelial cells

Hair shaft- the part of hair we seeHair color- determined by the amount of

pigment

Function of Hair

Protect scalp from UV radiation, insulate the skull

Prevent entry of foreign particlesSensitivity (nerves at base of each hair)Insulation (erector pili muscles in the skin

cause hair to stand on end)

Glands in the Skin

Sebaceous Glands- secrete sebum, which prevents bacterial growth, lubricates and protects hair and skin, ex. of a Holocrine gland Blocked sebaceous glands cause acne

Sweat glands- 2-5 million sweat glands, cools body temperature Merocrine- palms, soles, secrete onto surface of skin Apocrine- in armpits, groin, secrete their products

into a hair follicle

Injury and Repair

Step 1- bleeding triggers inflammationStep 2- Scab forms, phagocytic cells

remove debris, cells from the stratum germanativum migrate to the area

Step 3- Fibroblasts create a meshwork to connect tissue

Step 4- Fibroblast continue creating scar tissue