Anatomical Reference Systems and Body Organization in Human Anatomy

Anatomy

The study of the structures of the body.

Physiology

The study of the functions of the structures of the body.

Anatomical position

Describes the body standing in the standard position: standing up straight, facing forward, with arms at the sides and palms toward the front.

Body Planes

Imaginary vertical and horizontal lines used to divide the body into sections for descriptive purposes.

Body directions

Terms used to describe the location of body parts in relation to each other.

Body cavities

Spaces within the body that contain organs.

Structural units

Groups of body parts that work together to perform a related function.

Sagittal plane

Divides the body into unequal left and right portions.

Midsagittal plane

Divides the body into equal left and right halves.

Frontal (coronal) plane

Divides the body into anterior (front) and posterior (back) portions.

Transverse plane

Divides the body into superior (upper) and inferior (lower) portions.

Ventral

Refers to the front side of the body.

Dorsal

Refers to the back side of the body.

Cephalic

Means toward the head.

Caudal

Means toward the lower part of the body.

Anterior

Situated in the front.

Posterior

Situated in the back.

Superior

Uppermost, above, or toward the head.

Inferior

Lowermost, below, or toward the feet.

Proximal

Situated nearest the midline or beginning of a body structure.

Distal

Situated farthest from the midline or beginning of a body structure.

Medial

Refers to the direction toward or nearer the midline.

Lateral

Refers to the direction toward or nearer the side of the body, away from the midline.

Dorsal cavity

Located along the back of the body and head, containing organs of the nervous system.

Ventral cavity

Located along the front of the body and contains the organs that sustain life.

Cranial cavity

Located within the skull and surrounds and protects the brain.

Spinal cavity

Located within the back and surrounds and protects the spinal cord.

Thoracic cavity

Also known as the chest cavity or thorax.

Diaphragm

A muscle that separates the thoracic and abdominal cavities.

Abdominal cavity

Contains the major organs of digestion.

Pelvic cavity

The space formed by the hip bones and contains the organs of the reproductive and excretory systems.

Abdominopelvic cavity

Refers to the abdominal and pelvic cavities as a single unit.

Inguinal

Refers to the entire lower area of the abdomen, including the groin.

Regions of the thorax and abdomen

Divide the abdomen and lower portion of the thorax into 9 parts.

Right and left hypochondriac regions

Covered by the lower ribs.

Epigastric region

Located above the stomach.

Right and left lumbar regions

Located near the inward curve of the spine.

Umbilical region

Surrounds the umbilicus, commonly known as the belly button or naval.

Right and left iliac regions

Located near the hip bones.

Hypogastric region

Located below the stomach.

Right Upper Quadrant (RUQ)

One of the four quadrants of the abdomen used to describe the location of abdominal organs or pain.

Left Upper Quadrant (LUQ)

One of the four quadrants of the abdomen used to describe the location of abdominal organs or pain.

Right Lower Quadrant (RLQ)

One of the four quadrants of the abdomen used to describe the location of abdominal organs or pain.

Left Lower Quadrant (LLQ)

One of the four quadrants of the abdomen used to describe the location of abdominal organs or pain.

Peritoneum

A multilayered membrane that protects and holds the organs in place within the abdominal cavity.

Parietal peritoneum

The outer layer of the peritoneum that lines the interior of the abdominal wall.

Mesentery

A fused double layer of the parietal peritoneum that attaches parts of the intestine to the interior abdominal wall.

Visceral peritoneum

The inner layer of the peritoneum that surrounds the organs of the abdominal cavity.

Retroperitoneal

Located behind the peritoneum.

Peritonitis

The inflammation of the peritoneum.

Cells

The basic structural and functional units of the body, specialized and grouped together to form tissues and organs.

Tissue

Groups of cells that work together to perform a specific function.

Organs

Structures composed of different types of tissues that work together to perform specific functions.

Body systems

Groups of organs that work together to perform complex functions necessary for life.

Cytology

The study of the anatomy, physiology, pathology, and chemistry of cells.

Cell membrane

The tissue that surrounds and protects the contents of a cell from the external environment.

Cytoplasm

The material within the cell membrane that is not part of the nucleus.

Nucleus

The structure within the cell that is surrounded by the nuclear membrane and controls the activities of the cell.

Stem cells

Unspecialized cells that can renew themselves for long periods and can be transformed into cells with special functions.

Adult stem cells

Undifferentiated cells found among differentiated cells in a tissue or organ.

Embryonic stem cells

Undifferentiated cells that can form any adult cell.

Stem cell therapy

Also known as regenerative medicine, it has many potential uses to heal injuries and treat diseases.

Genes

The fundamental physical and functional units of heredity.

Dominant gene

A gene inherited from either parent that results in the offspring inheriting that genetic condition or characteristics.

Recessive gene

A gene inherited from both parents, meaning the offspring will have that condition.

Genome

The complete set of genetic information of an organism.

Chromosomes

Genetic structures located within the nucleus of each cell, made up of DNA molecules containing the body's genes.

Somatic cells

Any cells in the body except the gametes and contain 46 chromosomes arranged into 23 pairs.

Gametes

The only type of cells that do not contain 46 chromosomes, instead having 23 single chromosomes.

DNA

Deoxyribonucleic acid, the main component of chromosomes.

Genetic mutation

A change in the sequence of a DNA molecule.

Somatic cell mutation

A mutation that affects the individual but cannot be transmitted to the next generation.

Gametic cell mutation

A mutation that affects the genes in a gamete and can be transmitted by a parent to their children.

gene

A hereditary unit that can be absent or defective, causing genetic disorders.

hereditary

A disease that is passed down through generations.

Down syndrome

A genetic disorder caused by the presence of an extra chromosome 21.

cystic fibrosis

A genetic disorder that affects the respiratory and digestive systems.

hemophilia

A genetic disorder that impairs the body's ability to make blood clots.

muscular dystrophy

A group of genetic disorders that cause progressive weakness and loss of muscle mass.

tissues

The microscopic study of the structure, composition, and function of biological tissues.

epithelial tissue

Tissue that forms a protective covering for all internal and external surfaces of the body.

connective tissue

Tissue that supports and connects organs and other body tissues.

muscle tissue

Tissue that contains cells with the specialized ability to contract and relax.

nerve tissue

Tissue that contains cells with the specialized ability to react to stimuli and conduct electrical impulses.

internal surfaces

Surfaces located within the body.

external surfaces

Surfaces located on the outside of the body.

glands

Groups of specialized epithelial cells capable of producing secretions.

epidermis

The outer layer of skin formed by specialized epithelial tissue.

mucous membranes

Membranes that line various cavities and cover the surface of internal organs.

vessels

Structures that carry blood and lymph throughout the body.

dense connective tissues

A type of connective tissue characterized by a high density of collagen fibers.

adipose tissue

Also known as fat, it stores energy and provides insulation.

loose connective tissues

A type of connective tissue that holds organs in place and attaches epithelial tissue to other underlying tissues.

fluid connective tissues

Blood and lymph, which transport nutrients and waste.

contract

The ability of muscle tissue to shorten and generate force.

relax

The ability of muscle tissue to lengthen and decrease tension.

simuli

Stimuli that nerve tissue reacts to.

electrical impulses

Signals conducted by nerve tissue.

Aplasia

Defective development or congenital absence of an organ or tissue.

Hypoplasia

Incomplete development of an organ or tissue due to a deficiency in the number of cells.