Inegument

Keratinocytes

The most common epidermis cell, composing 90-95% of all epidermal cells. They originate in the deepest layer and synthesize keratin and lipids to form a water resistant barrier. They gradually move closer to the surface of the skin, flattening out before dying

Melanocytes

Located in the deepest layer. They produce melanin, a pigment that shields the nuclei from UV radiation

Dermal dendritic (langerhans cells)

Epidermal cells which originate in the bone marrow and migrate to the stratum spinosum of the epidermis. Act as phagocytes

Tactile (merkel) cells

Found in the deepest layer, they act as receptors for superficial touch

Stratum Basale

A single row of cuboidal OR columnar cells sitting directly on the basement membrane, attached to the dermis by hemidesmosomes. Where epidermal stem cells reside and contain melanocytes and merkel cells

Stratum spinosum

Considered a keratinized stratified squamous bound my desmosomes

Hemidesmosomes

Small protein structures which anchor basal epithelial cells to the basement membrane.

Desmosomes

Specialized proteins for cell-cell connection. They are in epithelial cells exposed to strong mechanical stressors. It binds cells toether, which is why skin comes off in sheets rather as individual cells

Stratum granulosum

a thin layer of flattened keratinocytes containing dark staining keratohyalin granules

keratohyalin granules

Membrane-free basophilic protein granules that aid in flattening out the keratinocytes as they rise. They dry out the cells

Stratum lucidum

A thin, translucent, clear band of dead, flattened keratinocytes located only in thick sin (palms and soles of feet). They contain eleidin

eleidin

An intermediate protein for keratin that adds an extra barrier against friction and water. Used in the stratum lucidum

Stratum corneum

The most superficial layer of the epidermis. Acts as the primary and chemical barrier against the external environment

corneocytes

specialized, dead, flattened keratinocytes that make up the outermost layer of the epidermis

Desquamates

Dermis

The thick, middle layer of skin that provides strength, houses sweat glands, hair follicles, and nerves. Made up of dense and loose connective tissue, elastic fibers, and collagen.

hypodermis (subcutaneous layer)

the bottom-most layer of the skin, which connects it to underlying muscle and facia. Made of loose areolar and adipose conective tissue. Insulates against cold, absorbs shock, and stores energy in the form of fat.

epidermis

The thinnest and outermost layer of skin. It is avascular and acts as a protective armor. It is slightly acidic and is water resistant

Lines of cleavage

topological lines mapped across the human body. They show the natural orientation of collagen fiber bundles in the reticular layer of the dermis. They generally run longitudinally on limbs, transversely across the neck, trunk, and hands, and circularly around the head and scapula. Incisions made parallel to cleavage lines tend to heal better

Papillary dermis

The upper layer of the dermis directly beneath the epidermis. Contains loose, areolar connective tissue and contains fine projections called dermal papillae which intertwine with the epidermis to form fingerprints and supply nutrients. Includes sensory nerve endings

Reticular dermis

The deep layer composing about 80% of the dermis. It is made of dense irregular connective tissue and is composed of thick, parallel bundles of type I collagen and interwoven with elastic fibers. Houses hair follicles, sebaceous glands, and sweat glands

Sebaceous glands

Holocrine exocrine glands located in the reticular dermis across the whole body EXCEPT on the palms and soles. They secret sebum, with higher concentrations on the face, scalp, upperback, and chest

Sebum

a oily lipid made of a mixture of triglycerides, wax esters, free fatty acids, and debris. It waterproofs and lubricates the skin and hair and has a mild antibacterial and antifungal effect

Endocrine glands

ductless glands that secrete hormones directly into the interstitial fluid and blood stream. Examples include the pituitary gland, thyroid gland, adrenal gland, and ovaries/testes.

exocrine glands

ducted glands that release their substances into ducts onto an epithelial surface. Examples include sweat glands, salivary glands, and mammary glands

merocrine (eccrine) glands

Glands which release products through exocytosis without losing cellular material. An example is salivary glands

Apocrine glands

Glands which pinch off a portion of the cell along with the product. An example is the mammary glands

holocrine glands

the entire cell disintegrates to release its products. An example are the sebaceous glands

Serous glands

Glands which secrete watery, enzyme rich fluids

Mucous glands

Glands which secrete thick, viscous mucin for protection and lubrication

seromucous glands

glands which produce both serous and mucous secretions

simple glands

A specific type of exocrine glands characterized by having an unbranched , single duct. There are four classifications

Simple tubular glands

a gland with a straight, uniform tube with no branching. Can be found in the intestinal crypts of the colon

simple coiled tubular

the secretory portion consists of a long tube coiled tightly onto itself. An example are eccrine sweat glands

simple branched tubular

the main duct is unbranched, but it splits at the base into multiple tubular secratory units. Examples include the gastric glands in the stomach and uterine glands

Simple acinar/ aveolar glands

A simple gland that forms a flask/bulbous pocket. Can be found in the sebaceous oil glands

Vitamin D

When UVB radiation penetrates the skin, it interacts with keratinocytes in the stratum Basale and stratum spinosum