Human Body Systems Organization and Skin Anatomy

A set of vocabulary flashcards covering the organization of the human body, primary tissue types, organ systems, homeostasis, and the detailed anatomy/physiology of the integumentary system.

Hierarchy of Organization

The four levels of organization in humans consisting of: 1. Cells; 2. Tissues; 3. Organs; 4. Organ Systems.

Cell Types (Humans)

The number of different cell types that compose the bodies of humans, which is $210$.

Tissue (Definition)

Groups of cells that are similar in structure and function.

Primary Tissues in Adult Vertebrates

The four main types of tissues: Epithelial, Connective, Muscle, and Nerve Tissue.

Epithelial Tissue

Tissue that separates, protects, and keeps organs in place; it covers the body surface and forms the lining of most organs.

Connective Tissue

The most abundant tissue in the human body that provides support and structure and fills spaces; examples include blood, bones, cartilage, and fat.

Muscle Tissue

Tissue that contracts and relaxes to support movement, categorized into three types: Skeletal, smooth, and cardiac.

Nerve Tissue

Tissue that responds to stimuli in the environment, controls movement and reflexes, and receives sensory information.

Organ (Definition)

Combinations of different tissues that form a structural and functional UNIT.

Vital Organ

Any organ that is essential to life, such as the heart, liver, lungs, and brain.

Organ Systems

Groups of organs that cooperate to perform the major activities of the body; the vertebrate body contains $11$ principal organ systems.

Homeostasis

The dynamic constancy of the internal environment which is essential for life.

Endothermic

The ability of humans to maintain a relatively constant body temperature of $37^\text{o}\text{C}$ ($98.6^\text{o}\text{F}$).

Hypothalamus

The control center in the brain that detects changes in body temperature and signals effector organs to respond.

Integumentary System

The body system consisting of the skin and its accessory structures, including nails, hair, and skin glands.

Skin Weight Percentage

The skin constitutes $16$ percent of the total body weight.

Epidermis

The outer, thinner layer of the skin composed entirely of stratified squamous epithelium; it is avascular and lacks nerve tissue.

Dermis

The inner, thicker layer of the skin containing blood vessels, nerve tissue, and accessory organs.

Subcutaneous Layer (Hypodermis)

A layer deep to the dermis composed of adipose (fat) tissue and larger blood vessels.

Keratinization

The process in which the outermost layer of cells in the epidermis harden and die.

Stratum Basale

The deepest layer of the epidermis, consisting of a single layer of cuboidal or columnar cells that are growing and dividing.

Stratum Corneum

The outermost epidermal layer composed of layers of dead, non-nucleated, keratinized cells.

Stratum Lucidum

An epidermal layer seen only in non-hairy or thick skin, such as the palms and soles.

Keratinocytes

The most common cells of the epidermis that provide protection and a waterproofing sealant.

Melanocytes

Specialized cells in the stratum basale that produce the dark pigment melanin, which provides skin color and absorbs UV-light.

Langerhans Cells

Non-pigmented granular dendrocytes in the stratum spinosum that participate in immune responses against bacteria and viruses.

Merkel Cells

Sensory cells found in the stratum basale, abundant in fingertips and hair follicles, that function as mechanoreceptors.

Melanin

A brown/black pigment produced by melanocytes in the epidermis; production is stimulated by ultraviolet radiation.

Carotene

A yellow-orange pigment that is a precursor of vitamin A, found in the stratum corneum and dermis.

Arrector Pilorum Muscle

Smooth muscle extending from the papillary layer of the dermis to the hair follicle; its contraction squeezes out sebum and causes "goose flesh."

Sebaceous Glands

Holocrine glands distributed all over the dermis (except palms and soles) that produce an oily secretion called sebum.

Eccrine Sweat Glands

Merocrine glands most numerous in the soles and palms that produce a thin watery secretion.

Apocrine Sweat Glands

Modified sweat glands confined to the axilla, eyelids, nipple, and external genitalia that produce a thick odorous secretion.

Langer’s (Cleavage) Lines

The natural lines along which the fiber bundles run in the skin; incisions in this direction gape much less than those at right angles.

Linea Gravidarum

Prominent white lines resulting from the rupture of fiber bundles in the dermis due to excessive stretching, commonly seen on the abdomen during pregnancy.

Rule of Nines

A method used to estimate the extent of damaged skin in burn injuries based on body surface area percentages.

Dermatome

A strip of skin supplied by a single spinal nerve.

Vitamin D Synthesis

The process where skin exposed to ultraviolet rays transforms pro-Vitamin D to Vitamin D3, which is later modified in the liver and kidney to Vitamin D.