Human Anatomy

Anatomical position

The standard body position with the person standing upright, facing forward, arms at the sides, and palms facing forward.

Dorsal

Refers to the back side of the body.

Ventral

Refers to the front side of the body.

Palmar

Refers to the palm side of the hand.

Plantar

Refers to the sole/bottom side of the foot.

Anterior

Toward the front of the body.

Posterior

Toward the back of the body.

Superior

Toward the head or upper part of the body.

Inferior

Toward the feet or lower part of the body.

Proximal

Closer to the point where a limb attaches to the body.

Distal

Farther from the point where a limb attaches to the body.

Superficial

Closer to the surface of the body.

Deep

Farther beneath the surface of the body.

Medial

Toward the midline of the body.

Lateral

Away from the midline of the body.

Median

Located directly on the body's midline.

Paramedian

Located near but not directly on the body's midline.

Sagittal plane

Divides the body into left and right portions.

Coronal (frontal) plane

Divides the body into anterior and posterior portions.

Transverse (horizontal) plane

Divides the body into superior and inferior portions.

Internal

Located inside or toward the interior of a structure.

External

Located outside or toward the exterior of a structure.

Parietal

Refers to a membrane layer lining the wall of a body cavity.

Visceral

Refers to a membrane layer covering an organ.

Ipsilateral

Located on the same side of the body.

Contralateral

Located on opposite sides of the body.

Supine

Lying flat on the back with the face upward.

Prone

Lying flat on the abdomen with the face downward.

Extension

Movement that increases the angle between two bones or straightens a joint.

Flexion

Movement that decreases the angle between two bones or bends a joint.

Abduction

Movement of a body part away from the body's midline.

Adduction

Movement of a body part toward the body's midline.

Opposition

Movement of the thumb across the palm toward the fingers.

Medial rotation

Rotation of a limb toward the body's midline.

Lateral rotation

Rotation of a limb away from the body's midline.

Supination

Rotation of the forearm so the palm faces upward/anteriorly.

Pronation

Rotation of the forearm so the palm faces downward/posteriorly.

Circumduction

Circular movement that combines flexion, extension, abduction, and adduction.

Inversion

Turning the sole of the foot inward toward the body's midline.

Eversion

Turning the sole of the foot outward away from the body's midline.

Protraction

Forward movement of a body part, such as the jaw or shoulders.

Retraction

Backward movement of a body part, such as the jaw or shoulders.

Body cavities

Internal spaces that contain and protect organs.

Axial

Refers to the head, neck, and trunk of the body.

Appendicular

Refers to the limbs and the structures connecting them to the axial skeleton.

Membranes

Thin sheets of tissue that cover surfaces, line cavities, or separate structures.

Dermatomes

Areas of skin supplied by sensory nerves from a specific spinal nerve.

Cell

The smallest structural and functional unit of life.

Tissue

A group of similar cells that work together to perform a specific function.

Organ

A structure made of multiple tissues that performs specific functions.

Organ system

A group of organs that work together to perform major body functions.

Fascia

Connective tissue that surrounds, separates, and supports muscles, organs, nerves, and blood vessels.

Serous membrane

A thin membrane that lines closed body cavities and covers organs within them.

Mucous membrane

A membrane lining passages that open to the outside of the body and produces mucus.

Synovial membrane

A membrane lining synovial joints that produces synovial fluid.

Cutaneous membrane

The skin, which covers and protects the external surface of the body.

Nervous system

The body system that detects stimuli and rapidly controls and coordinates body functions.

Central nervous system (CNS)

Consists of the brain and spinal cord.

Peripheral nervous system (PNS)

Consists of nerves and ganglia outside the brain and spinal cord.

Somatic nervous system

Controls voluntary movements and carries sensory information from the skin, muscles, and joints.

Autonomic nervous system

Controls involuntary functions of organs, glands, and smooth and cardiac muscle.

Sympathetic nervous system

The autonomic division that prepares the body for stressful or emergency situations.

Parasympathetic nervous system

The autonomic division that promotes rest, digestion, and energy conservation.

Endocrine system

A system of glands that releases hormones directly into the bloodstream to regulate body functions.

Exocrine

A gland that releases its secretions through ducts onto a surface or into a body cavity.

Skeletal system

The body's framework of bones and connective tissues that supports, protects, and enables movement.

Bone

A hard connective tissue that provides support, protection, mineral storage, and blood-cell production.

Cartilage

A flexible connective tissue that provides support and cushioning at joints and other structures.

Muscle

Specialized tissue that contracts to produce movement and force.

Skeletal muscle

Voluntary muscle attached to bones that produces body movement.

Cardiac muscle

Involuntary muscle found only in the heart that produces its contractions.

Smooth muscle

Involuntary muscle found in the walls of organs and blood vessels.

Joint

A connection between two or more bones that allows varying degrees of movement.

Fibrous joint

A joint connected by dense connective tissue with little or no movement.

Cartilaginous joint

A joint connected by cartilage that allows limited movement.

Synovial joint

A freely movable joint containing a fluid-filled joint cavity.

Ligament

A band of connective tissue that connects bone to bone.

Tendon

A band of connective tissue that connects muscle to bone.

Bursa

A small fluid-filled sac that reduces friction between moving tissues.

Circulatory/cardiovascular system

The system that circulates blood throughout the body to transport oxygen, nutrients, hormones, and wastes.

Blood vessels

Tubes that carry blood throughout the body.

Heart

A muscular organ that pumps blood through the circulatory system.

Lymphatics

A network of vessels and organs that returns excess tissue fluid to the bloodstream and supports immune function.

Respiratory system

The system responsible for exchanging oxygen and carbon dioxide between the body and environment.

Digestive system

The system that breaks down food, absorbs nutrients, and eliminates solid waste.

Alimentary canal

The continuous tube from the mouth to the anus through which food travels.

Gastrointestinal (GI) tract

Another name for the alimentary canal, including the mouth, esophagus, stomach, intestines, rectum, and anus.

Urogenital systems

The urinary and reproductive systems, which are anatomically and developmentally related.

Urinary tract

The kidneys, ureters, bladder, and urethra that produce, transport, store, and eliminate urine.

Reproductive system

The organs responsible for producing gametes and enabling reproduction.

Gonad

A reproductive organ that produces gametes and sex hormones.

Gamete

A reproductive sex cell containing one set of chromosomes, such as sperm or an egg.

Plasma membrane (plasmalemma)

The thin, selectively permeable membrane surrounding a cell that separates its internal environment from the outside.

Phospholipid bilayer

A double layer of phospholipids forming the basic structure of the cell membrane.

Cholesterol

A lipid within the membrane that helps maintain membrane stability and fluidity.

Integral membrane proteins

Proteins embedded within or extending across the cell membrane.

Peripheral proteins

Proteins attached to the inner or outer surface of the cell membrane.

Fluid mosaic model

The model describing the membrane as a flexible phospholipid bilayer containing proteins that can move within it.

Receptor protein

A membrane protein that receives chemical signals from outside the cell.

Signal protein

A membrane protein involved in transmitting information into or between cells.