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