Epidermis and Dermis

Quiz 2

Epidermis

function: protective from UV radiation, abrasions, water loss

keratinized stratified squamous epithelial tissue that has five layers

Stratum basale or stratum germinativum

deepest epidermal layer, attached to the underlying dermis. consists of a single row of cells mostly stem cells

has nerve receptors for touch

10-25% of the cells are spider shaped melanocytes which make the dark skin pigment melanin

Stratum spinosum

several cell layers thick

mitosis occurs here, less often than in the basal layer

dendritic cells are present here, leave the skin to travel to lymph nodes and initiate immune responses to foreign cells that carry the antigen

Stratum granulosum

consists of one to five layers of flattened keratinocytes and keratohyalin granules (which help form keratin in the more superficial layers) and lamellar granules (which contain a waterproof glycolipid that is secreted into the extracellular space, which helps with water loss)

Stratum lucidum

occurs in thick skin, not present in thin skin

appears as a thin translucent band under the microscope

Stratum corneum

most superficial layer, much thicker in thick skin. Its dead keratinocytes are flat sacs completely filled with keratin because their nuclei and organelles disintegrated upon cell death.

cells of this layer shed regularly, average person sheds 40 pounds of these skin flakes in a lifetime.

Dermis

second major region of the skin, strong flexible connective tissue

divided into 20% papillary (areolar) and 80% reticular (dense irregular) layers

Dermal papillae

textured region, increases surface area for exchange of gases, nutrients and waste products

on palms of hands and soles of feet, dermal papillae lie atop larger mounds called dermal ridges and elevate the epidermal ridges which create fingertips

Reticular dermis

dense irregular connective tissue. extracellular matrix contains thick bundles of interlacing collagen and elastic fibers that run in many different planes, most run parallel to the skin surface

Nerve fibers

free nerve endings or encapsulated nerve endings. Free are for pain and temperature and encapsulated are medhanorecptors

Blood vessels

consist of two vascular plexuses (network of converging and diverging vessels)

nourishes the dermis and overlying epidermis, performs temperature regulation

Sebaceous gland

secretes sebum

this makes your hair greasy, surrounds the hair folicle

Sudoriferous glands

secrete sweat

two types: apocrine and eecrine/merocrine

Apocrine sudoriferous glands

produces body odor, activated after puberty

Eecrine/merocrine sudoriferous glands

smaller glands, all over the body and active since birth, helps with thermoregulation

Hair follicle & hair shaft

embedded within the dermis, derived from the epidermal layer and extend down into the dermis and subcutaneous tissue

Vellus

peach fuzz, women have more than men

Terminal

thicker hair

(on head, eyebrows, etc.)

Carotene

yellow orange pigment that the body obtains from vegetable sources like carrots and tomatoes, accumulates in the stratum corneum and the fat of the subcutaneous tissue

Melanin

made from an amino acid, tyrosine

ranges from yellow to reddish to brown to black

variations in skin color are results of the differences in both amount and type of melanin produced

Arrector pili muscle

responsible for goosebumps

large structure attached to hair follicle

Pacinian corpuscle

acorn like

detects deep stretch, pressure, and vibration

Ruffini corpuscle/Type II cutaneous mechanoreceptor

bean like

responds to deep pressure, twisting and torsion

Meissner corpuscle

in dermal papillae in the dermis

detects light pressure and fine touch

Merkel cells/Epidermal

in the stratum basale of the epidermis

yellow small fiber

detects light pressure and fine touch