Medical Terminology

Chapter 2: Body Structure

CHAPTER OBJECTIVES

This chapter introduces the medical terms that describe the elements of the human body structure including the planes of the human body, the body cavities and the organs contained therein. Upon completion of this chapter, you will be able to:

• Describe the elements of the human body structure and the anatomical positions

• Describe the body planes

• Identify regions of the body

• Define directional and positional terms

• Recognize combining forms that relate to elements and systems of the body

Before you begin to study the

different structures and functions of

the human body, it is helpful to

consider its basic architecture; that

is, how its smallest parts are

assembled into larger structures. It

is convenient to consider the

structures of the body in terms of

fundamental levels of organization

that increase in complexity:

subatomic particles, atoms,

molecules, organelles, cells, tissues,

organs, organ systems, organisms

and biosphere.

The organization of the

body often is discussed in

terms of six distinct levels of

increasing complexity, from

the smallest chemical

building blocks to a unique

human organism.

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Click image to enlarge.

INTRODUCTION

Cells are the basic building blocks of all living things. The human body is composed of trillions of cells. They provide structure for the body, take in nutrients from food, convert those nutrients into energy, and carry out specialized functions. Cells also contain the body’s hereditary material and can make copies of themselves.

A human cell typically consists of a flexible membrane, cytoplasm, and a nucleus. In humans, as in all organisms, cells perform all functions of life and all cells require food, water and oxygen to function properly.

• Cell Membrane: The outer lining of the cell. It separates the cell from its environment and allows materials to enter and leave the cell.

• Cell Nucleus: The nucleus serves as the cell’s command center, sending directions to the cell to grow, mature, divide, or die. It also houses DNA (deoxyribonucleic acid), the cell’s hereditary material. The nucleus is surrounded by a membrane called the nuclear envelope, which protects the DNA and separates the nucleus from the rest of the cell.

• Cytoplasm: Within cells, the cytoplasm is made up of a jelly-like fluid (called the cytosol) and other structures that surround the nucleus.

CELLS

A primary responsibility of each cell is to contribute to homeostasis. Homeostasis is a term used in biology that refers to a dynamic state of balance within parameters that are compatible with life. Maintaining homeostasis requires that the body continuously monitor its internal conditions. From body temperature to blood pressure to levels of certain nutrients, each physiological condition has a normal range.

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

Link to Learning: Please watch: Nucleus Medical Media: Biology: Cell

Structure, for an overview of basic cell structures and functions.

TISSUES

The body has four types of tissues:

• Epithelial tissue also referred to as epithelium, are widespread throughout the body. They form the covering of all body surfaces, line body cavities and hollow organs, and are the major tissue in glands. They perform a variety of functions that include protection, secretion, absorption, excretion, filtration, diffusion, and sensory reception.

• Connective tissue, as its name implies, binds structures together, forms a framework and support for organs and the body as a whole, stores fat, transports substances, protects against disease, and helps repair tissue damage.

• Muscle tissue is composed of cells that have the special ability to shorten or contract in order to produce movement of the body parts. Muscle tissue can be categorized into skeletal muscle tissue, smooth muscle tissue, and cardiac muscle tissue.

• Nervous tissue, composed of neurons, is found in the brain, spinal cord, and nerves. It is responsible for coordinating and controlling many body activities. It stimulates muscle contraction, creates an awareness of the environment, and plays a major role in emotions, memory, and reasoning. To do all these things, cells in nervous tissue need to be able to communicate with each other by way of electrical nerve impulses.

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Click image to enlarge.

Organs are more complex units than tissues. An organ is an

organization of several different kinds of tissues arranged so that

together they can perform a special function. For example, the

stomach is an organization of muscle, connective, epithelial, and

nervous tissues. Muscle and connective tissues form its wall,

epithelial and connective tissues form its lining, and nervous tissue

extends throughout both its wall and its lining.

Organs that work together are grouped into organ systems.

Systems are the most complex of the component units of the human body. A system is an organization of varying numbers and kinds of organs arranged so that together they can perform complex functions for the body.

The major systems are:

• Integumentary System• Skeletal System• Muscular System• Nervous System• Endocrine System• Cardiovascular system• Blood and Lymphatic System• Respiratory System• Digestive System• Urinary System• Reproductive System

ORGANS

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Click on each image to enlarge.

In making diagnoses or prescribing treatments, health care providers use standard terms to refer to

different areas of the body in order to increase precision and reduce medical errors. To further increase

precision, the way in which they view the body is also standardized.

Just as maps are normally oriented with north at the top, the standard body “map,” or anatomical position,

is that of the body standing upright, with the feet at shoulder width and parallel, toes forward. The upper

limbs are held out to each side, and the palms of the hands face forward.

Using this standard position reduces confusion. It does not matter how the body being described is

oriented, the terms are used as if it is in anatomical position. For example, a scar in the “anterior (front)

carpal (wrist) region” would be present on the palm side of the wrist. The term “anterior” would be used

even if the hand were palm down on a table.

A body that is lying down is described as either prone or

supine. These terms are sometimes used in describing the

position of the body during specific physical examinations

or surgical procedures.

• Prone describes a face-down orientation

• Supine describes a face up orientation

ANATOMICAL POSITIONS

Directional Terms are essential for describing the relative locations of different body structures. For instance, an anatomist might describe one band of tissue as “inferior to” another or a physician might describe a tumor as “superficial to” a deeper body structure. Commit these terms to memory to avoid confusion when you are studying or describing the locations of particular body parts.

• Anterior (or ventral) describes the front or direction toward the front of the body. The toes are

anterior to the foot.

• Posterior (or dorsal) describes the back or direction toward the back of the body. The popliteus

is posterior to the patella.

• Superior (or cranial) describes a position above or higher than another part of the body proper.

The orbits are superior to the oris.

• Inferior (or caudal) describes a position below or lower than another part of the body proper;

near or toward the tail (in humans, the coccyx, or lowest part of the spinal column). The pelvis

is inferior to the abdomen.

• Lateral describes the side or direction toward the side of the body. The thumb (pollex) is lateral

to the digits.

DIRECTIONAL TERMS

• Medial describes the middle or direction toward the

middle of the body. The hallux is the medial toe.

• Proximal describes a position in a limb that is nearer

to the point of attachment or the trunk of the body.

The brachium is proximal to the antebrachium.

• Distal describes a position in a limb that is farther

from the point of attachment or the trunk of the

body. The hand is distal to the elbow.

• Superficial describes a position closer to the surface

of the body. The skin is superficial to the bones.

• Deep describes a position father from the surface of

the body. The brain is deep into the skull.

• Cephalic: Pertaining to the head, superior in position

Image Source: OpenStax College, Anatomy & Physiology. OpenStax College. http://cnx.org/content/col11496/latest/

Click Image to enlarge.

The human body is shown in anatomical position in an (a) anterior view and a (b) posterior view. The regions of the body are labeled in boldface.

Click image to enlarge.

Image Source: OpenStax College, Anatomy & Physiology. OpenStax College. http://cnx.org/content/col11496/latest/

A section is a two-dimensional surface of a three-dimensional structure that has been cut. Modern medical imaging devices enable clinicians to obtain “virtual sections” of living bodies. We call these scans. Body sections and scans can be correctly interpreted, however, only if the viewer understands the plane along which the section was made. A plane is an imaginary two-dimensional surface that passes through the body. There are three planes commonly referred to in anatomy and medicine.

• The sagittal (lateral) plane is the plane that divides the body or an organ

vertically into right and left sides. If this vertical plane runs directly down

the middle of the body, it is called the midsagittal or median plane.

• The frontal (coronal) plane is the plane that divides the body or an organ

into an anterior (front) portion and a posterior (rear) portion. The frontal

plane is often referred to as a coronal plane. (“Corona” is Latin for

“crown”).

• The transverse (cross-sectional) plane is the plane that divides the body

or organ horizontally into upper and lower portions. Transverse planes

produce images referred to as cross sections.

Image Source: OpenStax College, Anatomy & Physiology. OpenStax College. http://cnx.org/content/col11496/latest/

BODY PLANES

Link to Learning: Test what you have learned so far with this interactive activity, Anatomical Terminology: Relative Position

Please watch: Human Biology Explained: Anatomical Terms – Drawn & Defined.

The body maintains its internal organization by means of membranes, sheaths, and other structures that separate compartments. The dorsal(posterior) cavity and the ventral (anterior) cavity are the largest body compartments. These cavities contain and protect delicate internal organs, and the ventral cavity allows for significant changes in the size and shape of the organs as they perform their functions. The lungs, heart, stomach, and intestines, for example, can expand and contract without distorting other tissues or disrupting the activity of nearby organs.

Image Source: OpenStax College, Anatomy & Physiology. OpenStax College. http://cnx.org/content/col11496/latest/

The ventral cavity includes the thoracic and abdominopelvic

cavities and their subdivisions. The dorsal cavity includes the

cranial and spinal cavities.

BODY CAVITIESClick image to enlarge.

THORACIC CAVITY: The upper ventral, thoracic, or chest

cavity contains the heart, lungs, trachea, esophagus and

major blood vessels.

ABDOMINAL AND PELVIC CAVITY: The lower part of the

ventral (abdominopelvic) cavity can be further divided into

two portions: abdominal portion and pelvic portion. The

abdominal cavity contains most of the gastrointestinal tract

as well as the kidneys and adrenal glands. The pelvic cavity

contains most of the urogenital system as well as the

rectum.

DORSAL CAVITY: The smaller of the two main cavities is

called the dorsal cavity. As its name implies, it contains

organs lying more posterior in the body. The dorsal cavity,

again, can be divided into two portions. The upper portion,

or the cranial cavity, houses the brain, and the lower

portion, or vertebral canal houses the spinal cord.

Image Source: Body Cavity. Wikipedia. https://en.wikipedia.org/wiki/Body_cavity. Public Domain.

Please watch: Human Biology Explained: Body Cavities– Drawn & Defined.

To promote clear communication, for instance about the location of a patient’s abdominal pain or a suspicious mass, health care providers typically divide up the cavity into either nine regions or four quadrants.

Right upper quadrant (RUQ): contains the right lobe of the liver, gallbladder, part of the pancreas, and part of the small and large intestines.

Left upper quadrant (LUQ): Contains the left lobe of the liver, stomach, spleen, part of the pancreas, and part of the small and large intestines.

Right lower quadrant (RLQ): Contains part of the small and large intestines, appendix, right ovary, right fallopian tube, right ureter.

Left lower quadrant (LLQ): Contains part of the small and large intestines, left ovary, left fallopian tube, left ureter.

ABDOMINAL REGIONS AND QUADRANTS

Image Source: OpenStax College, Anatomy & Physiology. OpenStax College. http://cnx.org/content/col11496/latest/

Common Body Area Combining Forms

Body Area Combining Form Body Area Combining Form Body Area Combining Form

abdomen abdomen/o gums gingiv/o nose rhin/o; nas/o

ankle tars/o hand manus; chir/o ribs cost/o

arm brach/i head cephal/o side later/o

back poster/o heart cardi/o skin derm/a

bones oste/o hip coxa skull crani/o

breast mast/o; mamm/o leg crur/o stomach gastr/o

cheek bucc/o lip cheil/o; chil/o teeth dent/i

chest thorac/o liver hepat/o temples tempor/o

ear ot/o; aur/i lungs pulm/o; pneum/o thigh bone femor/o

elbow cubital mouth or/o throat pharyng/o

eye opt/o muscles muscul/o; my/o tongue lingu/o; gloss/o

eyelid blephar/o navel umbilic/o wrist carp/o

finger dactyl/o neck cervic/o

foot pod/o nerves neur/o

PRONUNCIATIONPractice pronouncing each term, then click the audio icon to hear it.

Adenitis (a-de-NI-tis)

Inflammation of a gland.

Arthralgia(ar-THRAL-je-a)

Pain in one or more joints.

Blepharitis(blef-a-RYE-tis)

Inflammation of the eyelids and especially of their margins.

Bursitis(bur-SI-tis)

Inflammation of a bursa (as of the shoulder or elbow).

Cerebelitis(ser-e-bell-EYE-tis)

Inflammation of the cerebellum.

Chondromalacia(KON-dro-ma-LA-she-a)

Abnormal softness of cartilage.

Cholelith(KO-le-lith)

Gallstone.

Audio and Definition Source: MedlinePlus Medical Dictionary, https://www.nlm.nih.gov/medlineplus/mplusdictionary.html, public domain.

Episiotomy(E-piz-e-OT-o-me)

Surgical enlargement of the vulva at the time of birth in order to avoid tearing the perineum.

Hematoma(he-ma-TOE-ma)

A mass of usually clotted blood that forms in a tissue, organ, or body space as a result of a broken blood vessel.

Histolysis(his-TOL-i-sis)

The breakdown of bodily tissues.

Ischialgia(Is-ke-AL-je-a)

Pain in the hip.

Mucolytic(Mew-ko-LIT-ik)

Agent that is capable of dissolving mucus.

Myocarditis(My-o-car-DI-tis)

Inflammation of the muscle tissue of the heart.

Oocyte(OH-o-site)

An egg before maturation.

Orofacial(or-o-FAY-shall)

Of or relating to the mouth and face.

Pelviscope(PEL-vi-scope)

An endoscope for visually examining the interior of the pelvis.

Audio and Definition Source: MedlinePlus Medical Dictionary, https://www.nlm.nih.gov/medlineplus/mplusdictionary.html, public domain.

Podiatrist(po-DI-a-trist)

Someone who specializes in diseases of the foot.

Reniform(REN-i-form)

Kidney shaped.

Splenectomy(sple-NECK-toe-me)

Surgical excision of the spleen.

Venipuncture(VEN-i-punk-sure)

Surgical puncture of a vein especially for the withdrawal of blood or for administration of intravenous fluids or drugs.

Audio and Definition Source: MedlinePlus Medical Dictionary, https://www.nlm.nih.gov/medlineplus/mplusdictionary.html, public domain.

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