Body Organization & Orientation

This is Unit Four of Medical Terminology: body organization and orientation — the shared spatial vocabulary every later unit borrows. Units One through Three built the decoding machine: word parts, joining rules, suffixes, prefixes. This unit supplies what those parts describe — the levels of the body, and the terms that say where in it something sits. One convention sits under the whole unit. The anatomical position — upright, facing forward, palms turned forward — is the reference every directional term is read against. Forget it and half this vocabulary inverts. The directional terms come in opposed pairs, and the book pairs them on purpose. Anterior and posterior, superior and inferior, medial and lateral, proximal and distal, superficial and deep. Each is defined by what it is not. One entry here is an error entry, and it names the mistake with the shortest path in this course to real harm: describing a side from where the observer stands rather than from the patient's own body. By the end you will be able to do five things. One: name the four levels of body organization and the combining forms for them. Two: state the anatomical position, and record a side as the patient's own. Three: name the three planes and the portions each one produces. Four: name the two cavities, their divisions, and the wall between them. Five: locate a finding by quadrant or region, and name a recorded position.

Five entries to begin. The first states the ladder the rest of the course climbs — cells, tissues, organs, systems — and the four that follow give the combining forms naming each rung, plus one for the body as a whole. These elements recur across every system unit, which is why they are numbered here rather than there.

The ladder itself.

MedTerm 0191 The Levels of Body Organization

The body is organized in ascending levels: cells form tissues, tissues form organs, and organs form systems. Muscle cells form muscle tissue, which forms the heart, part of the cardiovascular system. Each level is built from the one below it, and a term naming one level does not name another.

The smallest living unit.

MedTerm 0192 cyt/o: Cell

The combining form cyt slash o names a cell, the smallest living unit of the body. A leukocyte is a white blood cell. The same element appears as a root in the middle of a term and as the suffix cyte at its end.

One level up.

MedTerm 0193 hist/o: Tissue

The combining form hist slash o names tissue, a group of similar cells performing one function. Histology is the study of tissues. Tissue sits a level above the cell, so a histologic finding describes a group rather than a single cell.

The internal organs.

MedTerm 0194 viscer/o: Internal Organs

The combining form viscer slash o names the internal organs, particularly those within the ventral cavity. Visceral pain is pain arising from an internal organ. Visceral describes the organ itself, as distinct from the membrane covering it.

The body entire.

MedTerm 0195 somat/o: Body

The combining form somat slash o names the body as a whole. A somatic cell is any body cell other than a reproductive cell. Because somat slash o names the physical body, it stands in contrast to terms naming the mind.

Eleven entries, and the first governs the other ten. The anatomical position fixes what front and back, left and right mean, and the five directional pairs that follow are all read against it. The book pairs them deliberately: each term is defined by its opposite, so they are learned two at a time.

The reference position.

MedTerm 0196 The Anatomical Position

The anatomical position is the body standing upright, facing forward, arms at the sides, palms turned forward. Every directional term describes a body in this position, whatever position the patient is actually in. Without this reference, left and right, front and back have no fixed meaning in a record.

Toward the front.

MedTerm 0197 Anterior: Toward the Front

Anterior means toward the front of the body, and its combining form is anter slash o. The sternum is anterior to the heart. Ventral also means toward the front and appears in older writing; this course uses anterior.

Its opposite.

MedTerm 0198 Posterior: Toward the Back

Posterior means toward the back of the body, and its combining form is poster slash o. The spine is posterior to the heart. Dorsal also means toward the back, and anterior and posterior are the pair this course uses.

Toward the head.

MedTerm 0199 Superior: Toward the Head

Superior means toward the head or the upper part of a structure, and its combining form is super slash o. The lungs are superior to the diaphragm. Superior names a position and not a quality, and it carries no sense of better.

Its opposite.

MedTerm 0200 Inferior: Toward the Feet

Inferior means toward the feet or the lower part of a structure, and its combining form is infer slash o. The stomach is inferior to the diaphragm. Superior and inferior are relative: a structure is superior only to something named.

Toward the midline.

MedTerm 0201 Medial: Toward the Midline

Medial means toward the midline of the body, and its combining form is medi slash o. The nose is medial to the eyes. Medial describes position relative to the midline of the body, not the middle of an organ.

Its opposite.

MedTerm 0202 Lateral: Away From the Midline

Lateral means toward the side, away from the midline, and its combining form is later slash o. The ears are lateral to the eyes. Medial and lateral describe direction from the midline, and neither of them means left or right.

Nearer the attachment.

MedTerm 0203 Proximal: Nearer the Point of Attachment

Proximal means nearer to the trunk or to the point of attachment, and its combining form is proxim slash o. The elbow is proximal to the wrist. Proximal and distal describe limbs and tubular structures, not the trunk itself.

Its opposite.

MedTerm 0204 Distal: Farther From the Point of Attachment

Distal means farther from the trunk or from the point of attachment, and its combining form is dist slash o. The fingers are distal to the wrist. Proximal and distal are always relative to a named reference point.

Toward the surface.

MedTerm 0205 Superficial: Toward the Surface

Superficial means toward or on the surface of the body. A superficial laceration involves only the outer layers of skin. Superficial describes depth from the surface, and it says nothing about the size or the severity of what it describes.

Its opposite.

MedTerm 0206 Deep: Away From the Surface

Deep means away from the surface, farther into the body. The femur lies deep to the muscles of the thigh. Superficial and deep describe one axis only, so a structure can be deep and also lateral at the same time.

Four entries about sides. The first is an error entry, placed early because the mistake it names has the shortest path in this course to a wrong-limb procedure. The three that follow supply the vocabulary for one side, both sides, the same side and the opposite side.

The error itself.

MedTerm 0207 Error: Using Directional Terms From the Viewer's Position

Directional terms describe the patient's body, never the position of the person looking at it. A lesion on the patient's left appears on the viewer's right, and is recorded as left. This error reverses sides in a record, which is how procedures reach the wrong limb.

One side, or both.

MedTerm 0208 Unilateral and Bilateral

Unilateral means affecting one side; bilateral means affecting both sides. Bilateral hearing loss affects both ears, while unilateral hearing loss affects one. Bilateral does not mean equal — both sides are involved, not necessarily to the same degree.

The same side.

MedTerm 0209 Ipsilateral: Same Side

Ipsilateral means on the same side of the body as another named structure or finding. An ipsilateral weakness appears on the same side as the injury. Ipsilateral needs a stated reference, and same side as what must appear in the record.

Its opposite.

MedTerm 0210 Contralateral: Opposite Side

Contralateral means on the opposite side of the body from another named structure or finding. A contralateral weakness appears on the side opposite the injury. Ipsilateral and contralateral differ by a prefix and reverse the side entirely.

Four plane entries and then the unit's first worked problem. A plane is a cut, and each cut is named by the two portions it produces. The fifth entry puts planes and directional terms together and locates three structures along three axes each.

Right and left.

MedTerm 0211 The Sagittal Plane

The sagittal plane is a vertical plane dividing the body into right and left portions. A sagittal section of the head shows the profile from the side. A sagittal plane may divide the body unequally, and only one sagittal plane divides it evenly.

The even one.

MedTerm 0212 The Midsagittal Plane

The midsagittal plane is the sagittal plane passing through the midline, dividing the body into equal right and left halves. It passes through the nose and the navel. Every midsagittal plane is sagittal, and most sagittal planes are not midsagittal.

Front and back.

MedTerm 0213 The Frontal Plane

The frontal plane is a vertical plane dividing the body into anterior and posterior portions. A frontal section separates the chest from the back. The frontal plane is also called the coronal plane, and both names are current.

Top and bottom.

MedTerm 0214 The Transverse Plane

The transverse plane is a horizontal plane dividing the body into superior and inferior portions. A transverse section of the abdomen is the view a CT scan produces. Transverse, cross-section and axial plane all name the same cut.

Three structures, located in full.

MedTerm 0215 Locating a Structure With Planes and Directions

Locating a structure means naming its position along three axes: front to back, head to foot, and midline to side. The heart is posterior to the sternum, superior to the diaphragm, slightly left of the midsagittal plane. The right kidney is inferior to the liver and lateral to the midline on the right. The thumb is lateral to the other digits only in the anatomical position — and the term holds in any other hand position, because the reference never moves. A location naming one axis is incomplete.

Nine entries covering the spaces the organs sit in. Two main cavities, one along the back and one along the front, each with named divisions, and then the muscular wall separating the upper front cavity from the lower. Several of these divisions are boundaries of description as much as of anatomy.

The cavity along the back.

MedTerm 0216 The Dorsal Cavity

The dorsal cavity is the space along the back of the body containing the brain and the spinal cord, running from inside the skull down through the vertebral column. It is one continuous space, divided by name rather than by a wall.

Inside the skull.

MedTerm 0217 The Cranial Cavity

The cranial cavity is the division of the dorsal cavity within the skull, containing the brain and enclosed by the bones of the skull. Cranial names this cavity and also means toward the head as a direction, so the word does two jobs.

Inside the vertebral column.

MedTerm 0218 The Spinal Cavity

The spinal cavity is the division of the dorsal cavity within the vertebral column, containing the spinal cord. It is continuous with the cranial cavity at the base of the skull. The spinal cavity holds the cord, not the vertebrae that surround it.

The cavity along the front.

MedTerm 0219 The Ventral Cavity

The ventral cavity is the space along the front of the body containing most of the internal organs: the heart, lungs, stomach, intestines, and reproductive organs. A muscular wall divides the ventral cavity into an upper portion and a lower one.

Above the diaphragm.

MedTerm 0220 The Thoracic Cavity

The thoracic cavity is the division of the ventral cavity above the diaphragm, containing the lungs and heart and enclosed by the ribs and the sternum. Thoracic names the chest, and its combining form thorac slash o appears throughout respiratory terms.

Between the lungs.

MedTerm 0221 The Mediastinum

The mediastinum is the space in the thoracic cavity between the lungs, containing the heart, esophagus, and trachea. A mediastinal mass lies between the lungs rather than within one. The mediastinum is a region of the thoracic cavity, not a separate cavity.

Below the diaphragm.

MedTerm 0222 The Abdominal Cavity

The abdominal cavity is the division of the ventral cavity below the diaphragm, containing the stomach, intestines, liver, and kidneys. It has no bony wall at its front. The abdominal and pelvic cavities are continuous, and are often named together.

The lowest division.

MedTerm 0223 The Pelvic Cavity

The pelvic cavity is the lowest division of the ventral cavity, enclosed by the pelvic bones and containing the bladder and reproductive organs. It is continuous with the abdominal cavity above, and because no wall separates them, records often use the single term abdominopelvic.

The wall itself.

MedTerm 0224 The Diaphragm as Divider

The diaphragm is the muscular wall separating the thoracic cavity above from the abdominal cavity below, and it is the anatomical boundary between the chest and the abdomen. The diaphragm divides two cavities and also drives breathing, and both facts appear in terms.

Two entries, and they describe the same area twice over. Four quadrants is the coarser system and nine regions the finer one. A record chooses one and stays with it, and in either system right and left belong to the patient rather than to whoever is looking.

Four.

MedTerm 0225 The Four Abdominopelvic Quadrants

The abdominopelvic region is divided into four quadrants by a vertical and a horizontal line crossing at the navel. The quadrants are named right upper, left upper, right lower, and left lower. Right and left are the patient's, never the examiner's.

Nine.

MedTerm 0226 The Nine Abdominopelvic Regions

The abdominopelvic region is alternatively divided into nine regions by two vertical and two horizontal lines. The central three, from top to bottom, are the epigastric, umbilical, and hypogastric regions. Four quadrants and nine regions are two systems for one area, and a record uses one or the other.

Four entries naming a position rather than a direction. The first two are opposites, and the book records them as the pair most frequently reversed in dictation. The last two are eponyms, which means there is nothing inside them to decode, and both entries define the position and stop there.

Face up.

MedTerm 0227 Supine: Lying Face Up

Supine describes a body lying horizontally on its back, face upward. A patient positioned supine for an abdominal examination lies face up. Supine and prone are reversed constantly in dictation, and they describe opposite positions.

Its opposite.

MedTerm 0228 Prone: Lying Face Down

Prone describes a body lying horizontally on its front, face downward. A patient positioned prone for a back examination lies face down. One memory aid the book offers: prone and nose both take an o, and both point downward.

Head of the bed raised.

MedTerm 0229 Fowler Position

Fowler position describes a body lying on the back with the head of the bed raised between forty-five and sixty degrees. A record noting semi-Fowler describes a lower angle, roughly thirty degrees. Fowler is an eponym, named for a physician, so the term carries no decodable meaning.

The whole bed tilted.

MedTerm 0230 Trendelenburg Position

Trendelenburg position describes a body lying supine with the whole bed tilted so the head is lower than the feet. Reverse Trendelenburg describes the same tilt in the opposite direction, head higher than feet. It is an eponym, and it names a position only, stating nothing about why one is used.

Two entries to close, both longer than what came before. The first reads three recorded phrases back into plain terms, including one that cannot be resolved from the phrase alone. The second locates eight structures using nothing but this unit's directional terms, planes, cavities and quadrants.

Three chart phrases, resolved.

MedTerm 0231 Reading a Location From a Chart Note

Reading a recorded location means resolving each term against the anatomical position and the patient's own left and right. Tenderness in the RLQ is the right lower quadrant, the patient's right, below the horizontal line through the navel. Distal to the left lateral malleolus means farther from the trunk than the bony prominence on the outer side of the patient's left ankle. Patient supine, contralateral weakness noted, is incomplete on its own — contralateral to what must appear earlier in the note.

The capstone. Eight structures, located.

MedTerm 0232 Capstone: Locating Eight Structures

Eight structures, each stated on every axis it needs. The heart sits in the mediastinum of the thoracic cavity, posterior to the sternum and superior to the diaphragm. The liver occupies the right upper quadrant, the stomach the left upper, the appendix the right lower, all of them inferior to the diaphragm. The bladder lies in the pelvic cavity at the midline. The brain fills the cranial cavity, and the kidneys sit posterior in the abdominal cavity, lateral to the midline on both sides. Every quadrant here is the patient's, and on a scan image the right upper quadrant appears on the left of the screen.

Five things to carry out of Unit Four. The body is organized in ascending levels — cells form tissues, tissues form organs, organs form systems — and cyt slash o, hist slash o, viscer slash o and somat slash o name the cell, the tissue, the internal organs and the body as a whole. A term naming one level does not name another. The anatomical position is upright, facing forward, palms turned forward, and every directional term is read against it whatever position the patient is in. The five pairs run anterior and posterior, superior and inferior, medial and lateral, proximal and distal, superficial and deep. Left and right are the patient's, never the observer's. Three planes, each named by the two portions it makes: sagittal for right and left, frontal for anterior and posterior, transverse for superior and inferior. Only the midsagittal plane divides the body evenly, and frontal and coronal name one plane. The dorsal cavity holds the brain and the spinal cord in its cranial and spinal divisions. The ventral cavity holds most of the other organs, split by the diaphragm into the thoracic cavity above and the abdominal and pelvic cavities below. The abdominopelvic area is divided into four quadrants or into nine regions, and a record uses one system or the other. Supine is face up and prone is face down, and Fowler and Trendelenburg are eponyms naming a position and nothing further. Unit Five opens the body systems with the integumentary system, and every location term in it comes from here.