Structural Organization of the Human Body

Vocabulary flashcards detailing the six levels of structural organization of the human body and the eleven organ systems, along with their key organs and major physiological functions.

Chemical level

The simplest level of structural organization, where atoms bond to form molecules with three-dimensional structures.

Cellular level

The level of organization where a variety of molecules combine to form the fluid and organelles of a body cell.

Tissue level

A level of organization consisting of a community of similar cells (or sometimes a few related types) that work together to perform a specific function.

Organ level

A level of organization where two or more different tissue types combine to form an anatomically distinct structure that performs one or more specific physiological functions.

Organ system level

A level of organization where two or more organs work closely together to perform the major functions or meet the physiological needs of the body.

Organismal level

The highest level of structural organization, where many organ systems work harmoniously together to perform the functions of an independent living organism.

Element

A unique pure substance that composes all matter in the universe, examples of which include hydrogen, oxygen, carbon, nitrogen, calcium, and iron.

Atom

The smallest unit of any pure substance (element), composed of subatomic particles such as protons, electrons, and neutrons.

Molecule

A chemical combination of two or more atoms that acts as a chemical building block for all body structures, such as water, proteins, and sugars.

Cell

The smallest independently functioning unit of a living organism, consisting typically of flexible membranes enclosing cytoplasm and tiny functioning units called organelles.

Cytoplasm

The water-based cellular fluid enclosed by the flexible membranes of a human cell.

Organelle

A tiny functioning unit located within the cytoplasm of a cell.

Organism

A living being that possesses a cellular structure and can independently perform all physiologic functions necessary for life.

Biological sex

A classification determined by chromosomes, hormones, organs, and other physical characteristics, distinct from gender identity.

Integumentary System

An organ system comprising hair, skin, and nails that encloses internal body structures and serves as the site of many sensory receptors.

Skeletal System

An organ system comprising cartilage, bones, and joints that supports the body and enables movement alongside the muscular system.

Muscular System

An organ system comprising skeletal muscles and tendons that enables movement alongside the skeletal system and helps maintain body temperature.

Nervous System

An organ system comprising the brain, spinal cord, and peripheral nerves that detects and processes sensory information and activates bodily responses.

Endocrine System

An organ system comprising glands such as the pituitary gland, thyroid gland, pancreas, adrenal glands, testes, and ovaries that secretes hormones and regulates bodily processes.

Cardiovascular System

An organ system comprising the heart and blood vessels that delivers oxygen and nutrients to tissues and equalizes temperature in the body.

Lymphatic System

An organ system comprising the thymus, lymph nodes, spleen, and lymphatic vessels that returns fluid to blood and defends against pathogens.

Respiratory System

An organ system comprising the nasal passage, trachea, and lungs that delivers oxygen to the blood and removes carbon dioxide from the body.

Digestive System

An organ system comprising the stomach, liver, gall bladder, large intestine, and small intestine that processes food for use by the body and removes wastes from undigested food.

Urinary System

An organ system comprising the kidneys and urinary bladder that controls water balance in the body, removes wastes from blood, and excretes them.

Male Reproductive System

An organ system comprising the epididymis and testes that produces sex hormones and gametes and delivers gametes to the female.

Female Reproductive System

An organ system comprising the mammary glands, ovaries, and uterus that produces sex hormones and gametes, supports an embryo or fetus until birth, and produces milk for an infant.