[bio 50] skin and body membranes

Stratum corneum

Cells are dead, flat membranous sacs filled with keratin. Glycolipids in extracellular space make skin water-resistant.

Stratum granulosum

Cells are flattened, organelles are deteriorating, and cytoplasm is full of granules.

Stratum lucidum

Cells begin to die.

Stratum spinosum

Cells contain thick bundles of intermediate filaments made of pre-keratin.

Stratum basale

Stem cells are actively dividing, and some newly formed cells become part of the more superficial layers.

Papillary layer

The superficial dermal region with peglike projections called dermal papillae, which contain capillary loops (nutrients to the epidermis), pain receptors, and touch receptors. On palms and soles, they form ridges that increase friction and gripping ability.

Papillary patterns

These are genetically determined and form unique fingerprints on the fingertips, made visible by sweat pores.

Reticular layer

The deepest skin layer, composed of dense irregular connective tissue. It contains blood vessels, sweat and oil glands, and deep pressure receptors (lamellar corpuscles).

Cutaneous sensory receptors

These receptors (touch, pressure, temperature, pain) provide sensory information and alert to changes in the environment, such as heat or cold.

Phagocytes

Found in the dermis, these cells help prevent microbial penetration by destroying invading pathogens.

Collagen fibers

Responsible for the toughness of the dermis, help bind water to keep skin hydrated, and provide strength.

Elastic fibers

Allow skin elasticity, which diminishes with age, causing skin to sag and wrinkle.

Blood vessels

The dermis is richly supplied with blood vessels, helping to regulate body temperature. They engorge with blood when it's hot to release heat, and bypass the skin when it's cold to conserve heat.

Subcutaneous tissue (hypodermis)

Located beneath the dermis, made up mostly of adipose (fat) tissue. It anchors the skin to underlying organs, stores nutrients, absorbs shock, and insulates the body.

Blister formation

Occurs when the epidermis and dermis separate, allowing interstitial fluid to accumulate between the layers due to friction or burns.

Keratinocytes

The main cells of the epidermis that produce keratin, a fibrous protein that makes the epidermis tough and protective through a process called keratinization.

Desmosomes

Connections between keratinocytes that hold them together throughout the epidermis.

Avascularity of the epidermis

The lack of blood vessels in the epidermis explains why shaving doesn't cause bleeding even though many cell layers are cut.

Epithelial membranes

Membranes composed of an epithelial layer combined with an underlying layer of connective tissue.

Cutaneous membrane

The skin, composed of the epidermis and dermis, exposed to air and considered a dry membrane.

Mucous membranes (mucosa)

Membranes that line body cavities opening to the exterior, such as respiratory, digestive, urinary, and reproductive tracts; composed of epithelium and a connective tissue layer called lamina propria.

Serous membranes (serosa)

Membranes that line body compartments closed to the exterior, composed of simple squamous epithelium and a thin layer of areolar connective tissue.

Peritoneum

Serous membrane that lines the abdominal cavity.

Pleurae

Serous membrane that surrounds the lungs.

Pericardia

Serous membrane that surrounds the heart.

Synovial membranes

Connective tissue membranes that line joint cavities, composed of loose areolar connective tissue and no epithelial cells.

Skin

The cutaneous membrane that maintains the body's boundary, keeping water and molecules in, while keeping excess water and other substances out.

Integumentary system

The system composed of skin and its appendages that perform protective functions.

Epidermis

The outer layer of skin, composed mostly of keratinocytes that produce keratin.

Dermis

The deeper layer of skin, made of dense irregular connective tissue, containing blood vessels, nerves, and other structures like sweat and oil glands.

Hypodermis (subcutaneous tissue)

Adipose tissue that anchors the skin to underlying organs and stores nutrients.

Keratinocytes

Cells in the epidermis that produce keratin, giving the skin its tough protective qualities.

Melanin

A pigment that provides skin color, ranging from yellow to brown to black, produced by melanocytes.

Melanocytes

Spider-shaped cells in the epidermis that produce melanin.

Epidermal dendritic cells

Cells in the epidermis that alert and activate the immune system to threats like bacterial or viral invasion.

Merkel cells

Cells in the epidermis that act as touch receptors.

Papillary layer

The superficial region of the dermis, containing dermal papillae that form fingerprints.

Reticular layer

The deeper region of the dermis, made of dense irregular connective tissue, and containing blood vessels, sweat glands, and pressure receptors.

Collagen fibers

Fibers in the dermis responsible for skin toughness and hydration.

Elastic fibers

Fibers in the dermis that provide skin elasticity.

Homeostasis of skin temperature

Blood vessels in the dermis help maintain body temperature.

Cyanosis

A blueish tint to the skin due to poorly oxygenated hemoglobin, visible in the skin of light-skinned people and in mucous membranes.

Erythema (redness)

Skin redness caused by embarrassment, fever, inflammation, or allergy.

Pallor (blanching)

Skin paleness caused by emotional stress, anemia, or low blood pressure.

Jaundice

A yellow tint to the skin caused by a liver disorder and the accumulation of bile pigments.

Bruises

Skin marks where blood has clotted in tissue spaces, often caused by injury or vitamin C deficiency.

Sebaceous glands

Oil glands that secrete sebum to keep skin moist and soft; active during adolescence due to androgen production.

Sweat glands (sudoriferous glands)

Glands that produce sweat for thermoregulation; include eccrine and apocrine glands.

Eccrine glands

Sweat glands found all over the body that produce a watery sweat for heat regulation.

Apocrine glands

Sweat glands located in the axillary and genital areas, producing a milky sweat that may develop a musky odor when broken down by bacteria.

Hair follicles

Structures that house hair roots and produce hair.

Hair root

The part of the hair that is enclosed within the hair follicle.

Hair shaft

The part of the hair that projects from the surface of the skin.

Hair matrix

The growth zone at the base of the hair follicle where cells divide to form hair.

Medulla

The central core of a hair, consisting of large cells and air spaces.

Cortex

The layer of hair composed of flattened cells.

Cuticle

A single layer of cells that overlap to protect the hair shaft.

Arrector pili

Small muscles that contract to raise hairs, causing goosebumps.

Nail matrix

The thickened region at the base of the nail responsible for nail growth.

Athlete's foot

A fungal infection causing itchy, red, peeling skin between the toes.

Boils (furuncles)

Infections of hair follicles, often caused by Staphylococcus aureus.

Cold sores

Fluid-filled blisters caused by herpesvirus 1 infection.

Contact dermatitis

Skin inflammation caused by exposure to irritants or allergens.

Impetigo

Skin infection characterized by pink, fluid-filled lesions that rupture and weep fluid.

Psoriasis

A chronic autoimmune condition causing scaly, red patches on the skin.

Burns

Tissue damage caused by heat, chemicals, or radiation, leading to fluid loss and potential infection.

First-degree burns

Superficial burns that only damage the epidermis, usually healing quickly.

Second-degree burns

Burns affecting the epidermis and part of the dermis, which can regenerate.

Third-degree burns

Burns that destroy the epidermis and dermis, requiring skin grafts for regeneration.

Fourth-degree burns

Severe burns extending into deeper tissues like muscle or bone.

Basal cell carcinoma

The least malignant and most common type of skin cancer, often occurring on sun-exposed areas.

Squamous cell carcinoma

A skin cancer arising from the stratum spinosum, often found on the scalp, ears, or hands.

Malignant melanoma

A deadly form of skin cancer that develops from melanocytes and spreads rapidly.

ABCDE rule for melanoma

A guide for identifying melanoma based on Asymmetry, Border irregularity, Color variation, Diameter larger than 6mm, and Evolution of the mole.

Skin aging

As people age, skin loses elasticity, becomes thinner, and becomes more prone to wrinkling and cancer.

Male-pattern baldness

A form of hair loss influenced by genetics and hormonal changes.