Transcript dermis-hypodermis

Dermis and
Hypodermis
Dermis
Lies deep (beneath the epidermis)
Provides strength and elasticity to
the skin
Creates framework to support the
accessory structures
Made of 2 layers
Papillary Layer
Made of areolar tissue
Contains capillaries and sensory neurons
that serve the epidermis above
The 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 tissue
Stabilizes skin while allowing movement
Areas of subcutaneous fat change during
a person’s life
Location 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 see
Hair color- determined by the amount of
pigment
Function of Hair
Protect scalp from UV radiation, insulate
the skull
Prevent entry of foreign particles
Sensitivity (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 inflammation
Step 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