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Anatomical Terminology∗

OpenStax College

This work is produced by OpenStax-CNX and licensed under the

Creative Commons Attribution License 3.0†

Abstract

By the end of this section, you will be able to:

• Demonstrate the anatomical position• Describe the human body using directional and regional terms• Identify three planes most commonly used in the study of anatomy• Distinguish between the posterior (dorsal) and the anterior (ventral) body cavities, identifying their

subdivisions and representative organs found in each• Describe serous membrane and explain its function

Anatomists and health care providers use terminology that can be bewildering to the uninitiated. How-ever, the purpose of this language is not to confuse, but rather to increase precision and reduce medicalerrors. For example, is a scar �above the wrist� located on the forearm two or three inches away from thehand? Or is it at the base of the hand? Is it on the palm-side or back-side? By using precise anatomicalterminology, we eliminate ambiguity. Anatomical terms derive from ancient Greek and Latin words. Becausethese languages are no longer used in everyday conversation, the meaning of their words does not change.

Anatomical terms are made up of roots, pre�xes, and su�xes. The root of a term often refers to anorgan, tissue, or condition, whereas the pre�x or su�x often describes the root. For example, in the disorderhypertension, the pre�x �hyper-� means �high� or �over,� and the root word �tension� refers to pressure, sothe word �hypertension� refers to abnormally high blood pressure.

1 Anatomical Position

To further increase precision, anatomists standardize the way in which they view the body. Just as maps arenormally oriented with north at the top, the standard body �map,� or anatomical position, is that of thebody standing upright, with the feet at shoulder width and parallel, toes forward. The upper limbs are heldout to each side, and the palms of the hands face forward as illustrated in Figure 1 (Regions of the HumanBody). Using this standard position reduces confusion. It does not matter how the body being described isoriented, 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 usedeven if the hand were palm down on a table.

∗Version 1.3: Jun 3, 2013 2:46 pm -0500†http://creativecommons.org/licenses/by/3.0/

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Regions of the Human Body

Figure 1: The human body is shown in anatomical position in an (a) anterior view and a (b) posteriorview. The regions of the body are labeled in boldface.

A body that is lying down is described as either prone or supine. Prone describes a face-down orientation,and supine describes a face up orientation. These terms are sometimes used in describing the position ofthe body during speci�c physical examinations or surgical procedures.

2 Regional Terms

The human body's numerous regions have speci�c terms to help increase precision (see Figure 1 (Regionsof the Human Body)). Notice that the term �brachium� or �arm� is reserved for the �upper arm� and�antebrachium� or �forearm� is used rather than �lower arm.� Similarly, �femur� or �thigh� is correct, and

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�leg� or �crus� is reserved for the portion of the lower limb between the knee and the ankle. You will be ableto describe the body's regions using the terms from the �gure.

3 Directional Terms

Certain directional anatomical terms appear throughout this and any other anatomy textbook (Figure 2(Directional Terms Applied to the Human Body)). These terms are essential for describing the relativelocations of di�erent body structures. For instance, an anatomist might describe one band of tissue as�inferior to� another or a physician might describe a tumor as �super�cial to� a deeper body structure.Commit these terms to memory to avoid confusion when you are studying or describing the locations ofparticular body parts.

• Anterior (or ventral) Describes the front or direction toward the front of the body. The toes areanterior to the foot.

• Posterior (or dorsal) Describes the back or direction toward the back of the body. The popliteus isposterior to the patella.

• Superior (or cranial) describes a position above or higher than another part of the body proper. Theorbits are superior to the oris.

• Inferior (or caudal) describes a position below or lower than another part of the body proper; nearor toward the tail (in humans, the coccyx, or lowest part of the spinal column). The pelvis is inferiorto the abdomen.

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

• 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 crus is distal to the femur.• Super�cial describes a position closer to the surface of the body. The skin is super�cial to the bones.• Deep describes a position farther from the surface of the body. The brain is deep to the skull.

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Directional Terms Applied to the Human Body

Figure 2: Paired directional terms are shown as applied to the human body.

4 Body Planes

A section is a two-dimensional surface of a three-dimensional structure that has been cut. Modern medicalimaging devices enable clinicians to obtain �virtual sections� of living bodies. We call these scans. Bodysections and scans can be correctly interpreted, however, only if the viewer understands the plane along

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which the section was made. A plane is an imaginary two-dimensional surface that passes through thebody. There are three planes commonly referred to in anatomy and medicine, as illustrated in Figure 3(Planes of the Body).

• The sagittal 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 medianplane. If it divides the body into unequal right and left sides, it is called a parasagittal plane or lesscommonly a longitudinal section.

• The frontal plane is the plane that divides the body or an organ into an anterior (front) portion anda posterior (rear) portion. The frontal plane is often referred to as a coronal plane. (�Corona� is Latinfor �crown.�)

• The transverse plane is the plane that divides the body or organ horizontally into upper and lowerportions. Transverse planes produce images referred to as cross sections.

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Planes of the Body

Figure 3: The three planes most commonly used in anatomical and medical imaging are the sagittal,frontal (or coronal), and transverse plane.

5 Body Cavities and Serous Membranes

The body maintains its internal organization by means of membranes, sheaths, and other structures thatseparate compartments. The dorsal (posterior) cavity and the ventral (anterior) cavity are thelargest body compartments (Figure 4 (Dorsal and Ventral Body Cavities)). These cavities contain andprotect delicate internal organs, and the ventral cavity allows for signi�cant changes in the size and shapeof the organs as they perform their functions. The lungs, heart, stomach, and intestines, for example, canexpand and contract without distorting other tissues or disrupting the activity of nearby organs.

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Dorsal and Ventral Body Cavities

Figure 4: The ventral cavity includes the thoracic and abdominopelvic cavities and their subdivisions.The dorsal cavity includes the cranial and spinal cavities.

5.1 Subdivisions of the Posterior (Dorsal) and Anterior (Ventral) Cavities

The posterior (dorsal) and anterior (ventral) cavities are each subdivided into smaller cavities. In theposterior (dorsal) cavity, the cranial cavity houses the brain, and the spinal cavity (or vertebral cavity)encloses the spinal cord. Just as the brain and spinal cord make up a continuous, uninterrupted structure,the cranial and spinal cavities that house them are also continuous. The brain and spinal cord are protectedby the bones of the skull and vertebral column and by cerebrospinal �uid, a colorless �uid produced by thebrain, which cushions the brain and spinal cord within the posterior (dorsal) cavity.

The anterior (ventral) cavity has two main subdivisions: the thoracic cavity and the abdominopelviccavity (see Figure 4 (Dorsal and Ventral Body Cavities)). The thoracic cavity is the more superiorsubdivision of the anterior cavity, and it is enclosed by the rib cage. The thoracic cavity contains the lungsand the heart, which is located in the mediastinum. The diaphragm forms the �oor of the thoracic cavityand separates it from the more inferior abdominopelvic cavity. The abdominopelvic cavity is the largestcavity in the body. Although no membrane physically divides the abdominopelvic cavity, it can be usefulto distinguish between the abdominal cavity, the division that houses the digestive organs, and the pelviccavity, the division that houses the organs of reproduction.

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5.2 Abdominal Regions and Quadrants

To promote clear communication, for instance about the location of a patient's abdominal pain or a suspiciousmass, health care providers typically divide up the cavity into either nine regions or four quadrants (Figure 5(Regions and Quadrants of the Peritoneal Cavity)).

Regions and Quadrants of the Peritoneal Cavity

Figure 5: There are (a) nine abdominal regions and (b) four abdominal quadrants in the peritonealcavity.

The more detailed regional approach subdivides the cavity with one horizontal line immediately inferiorto the ribs and one immediately superior to the pelvis, and two vertical lines drawn as if dropped from themidpoint of each clavicle (collarbone). There are nine resulting regions. The simpler quadrants approach,which is more commonly used in medicine, subdivides the cavity with one horizontal and one vertical linethat intersect at the patient's umbilicus (navel).

5.3 Membranes of the Anterior (Ventral) Body Cavity

A serous membrane (also referred to a serosa) is one of the thin membranes that cover the walls andorgans in the thoracic and abdominopelvic cavities. The parietal layers of the membranes line the walls ofthe body cavity (pariet- refers to a cavity wall). The visceral layer of the membrane covers the organs (theviscera). Between the parietal and visceral layers is a very thin, �uid-�lled serous space, or cavity (Figure 6(Serous Membrane)).

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Serous Membrane

Figure 6: Serous membrane lines the pericardial cavity and re�ects back to cover the heart�much thesame way that an underin�ated balloon would form two layers surrounding a �st.

There are three serous cavities and their associated membranes. The pleura is the serous membranethat surrounds the lungs in the pleural cavity; the pericardium is the serous membrane that surrounds theheart in the pericardial cavity; and the peritoneum is the serous membrane that surrounds several organsin the abdominopelvic cavity. The serous �uid produced by the serous membranes reduces friction betweenthe walls of the cavities and the internal organs when they move, such as when the lungs in�ate or the heartbeats. Both the parietal and visceral serosa secrete the thin, slippery serous �uid that prevents friction whenan organ slides past the walls of a cavity. In the pleural cavities, pleural �uid prevents friction between thelungs and the walls of the cavity. In the pericardial sac, pericardial �uid prevents friction between the heartand the walls of the pericardial sac. And in the peritoneal cavity, peritoneal �uid prevents friction betweenabdominal and pelvic organs and the wall of the cavity. The serous membranes therefore provide additionalprotection to the viscera they enclose by reducing friction that could lead to in�ammation of the organs.

6 Chapter Review

Ancient Greek and Latin words are used to build anatomical terms. A standard reference position formapping the body's structures is the normal anatomical position. Regions of the body are identi�ed usingterms such as �occipital� that are more precise than common words and phrases such as �the back of thehead.� Directional terms such as anterior and posterior are essential for accurately describing the relativelocations of body structures. Images of the body's interior commonly align along one of three planes: thesagittal, frontal, or transverse. The body's organs are organized in one of two main cavities�dorsal (alsoreferred to posterior) and ventral (also referred to anterior)�which are further sub-divided according to thestructures present in each area. The serous membranes have two layers�parietal and visceral�surroundinga �uid �lled space. Serous membranes cover the lungs (pleural serosa), heart (pericardial serosa), and someabdominopelvic organs (peritoneal serosa).

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7 Review Chapter

Exercise 1 (Solution on p. 11.)

What is the position of the body when it is in the �normal anatomical position?�

a. The person is prone with upper limbs, including palms, touching sides and lower limbs touch-ing at sides.

b. The person is standing facing the observer, with upper limbs extended out at a ninety-degreeangle from the torso and lower limbs in a wide stance with feet pointing laterally

c. The person is supine with upper limbs, including palms, touching sides and lower limbstouching at sides.

d. None of the above

Exercise 2 (Solution on p. 11.)

To make a banana split, you halve a banana into two long, thin, right and left sides along the________.

a. coronal planeb. longitudinal planec. midsagittal planed. transverse plane

Exercise 3 (Solution on p. 11.)

The lumbar region is ________.

a. inferior to the gluteal regionb. inferior to the umbilical regionc. superior to the cervical regiond. superior to the popliteal region

Exercise 4 (Solution on p. 11.)

The heart is within the ________.

a. cranial cavityb. mediastinumc. posterior (dorsal) cavityd. All of the above

8 Critical Thinking Question

Exercise 5 (Solution on p. 11.)

In which direction would an MRI scanner move to produce sequential images of the body in thefrontal plane, and in which direction would an MRI scanner move to produce sequential images ofthe body in the sagittal plane?

Exercise 6 (Solution on p. 11.)

If a bullet were to penetrate a lung, which three anterior thoracic body cavities would it enter, andwhich layer of the serous membrane would it encounter �rst?

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Solutions to Exercises in this Module

to Exercise (p. 10)Dto Exercise (p. 10)Cto Exercise (p. 10)Dto Exercise (p. 10)Bto Exercise (p. 10)If the body were supine or prone, the MRI scanner would move from top to bottom to produce frontalsections, which would divide the body into anterior and posterior portions, as in �cutting� a deck of cards.Again, if the body were supine or prone, to produce sagittal sections, the scanner would move from left toright or from right to left to divide the body lengthwise into left and right portions.to Exercise (p. 10)The bullet would enter the ventral, thoracic, and pleural cavities, and it would encounter the parietal layerof serous membrane �rst.

Glossary

De�nition 1: abdominopelvic cavitydivision of the anterior (ventral) cavity that houses the abdominal and pelvic viscera

De�nition 2: anatomical positionstandard reference position used for describing locations and directions on the human body

De�nition 3: anteriordescribes the front or direction toward the front of the body; also referred to as ventral

De�nition 4: anterior cavitylarger body cavity located anterior to the posterior (dorsal) body cavity; includes the serousmembrane-lined pleural cavities for the lungs, pericardial cavity for the heart, and peritoneal cavityfor the abdominal and pelvic organs; also referred to as ventral cavity

De�nition 5: caudaldescribes 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); also referred to as inferior

De�nition 6: cranialdescribes a position above or higher than another part of the body proper; also referred to assuperior

De�nition 7: cranial cavitydivision of the posterior (dorsal) cavity that houses the brain

De�nition 8: deepdescribes a position farther from the surface of the body

De�nition 9: distaldescribes a position farther from the point of attachment or the trunk of the body

De�nition 10: dorsaldescribes the back or direction toward the back of the body; also referred to as posterior

De�nition 11: dorsal cavityposterior body cavity that houses the brain and spinal cord; also referred to the posterior bodycavity

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De�nition 12: frontal planetwo-dimensional, vertical plane that divides the body or organ into anterior and posterior portions

De�nition 13: inferiordescribes 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); also referred to as caudal

De�nition 14: lateraldescribes the side or direction toward the side of the body

De�nition 15: medialdescribes the middle or direction toward the middle of the body

De�nition 16: pericardiumsac that encloses the heart

De�nition 17: peritoneumserous membrane that lines the abdominopelvic cavity and covers the organs found there

De�nition 18: planeimaginary two-dimensional surface that passes through the body

De�nition 19: pleuraserous membrane that lines the pleural cavity and covers the lungs

De�nition 20: posteriordescribes the back or direction toward the back of the body; also referred to as dorsal

De�nition 21: posterior cavityposterior body cavity that houses the brain and spinal cord; also referred to as dorsal cavity

De�nition 22: proneface down

De�nition 23: proximaldescribes a position nearer to the point of attachment or the trunk of the body

De�nition 24: sagittal planetwo-dimensional, vertical plane that divides the body or organ into right and left sides

De�nition 25: sectionin anatomy, a single �at surface of a three-dimensional structure that has been cut through

De�nition 26: serous membranemembrane that covers organs and reduces friction; also referred to as serosa

De�nition 27: serosamembrane that covers organs and reduces friction; also referred to as serous membrane

De�nition 28: spinal cavitydivision of the dorsal cavity that houses the spinal cord; also referred to as vertebral cavity

De�nition 29: super�cialdescribes a position nearer to the surface of the body

De�nition 30: superiordescribes a position above or higher than another part of the body proper; also referred to as cranial

De�nition 31: supineface up

De�nition 32: thoracic cavitydivision of the anterior (ventral) cavity that houses the heart, lungs, esophagus, and trachea

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De�nition 33: transverse planetwo-dimensional, horizontal plane that divides the body or organ into superior and inferior portions

De�nition 34: ventraldescribes the front or direction toward the front of the body; also referred to as anterior

De�nition 35: ventral cavitylarger body cavity located anterior to the posterior (dorsal) body cavity; includes the serousmembrane-lined pleural cavities for the lungs, pericardial cavity for the heart, and peritoneal cavityfor the abdominal and pelvic organs; also referred to as anterior body cavity

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