Anatomical Position, Terms, Planes of Section, and Body Cavities

What is the anatomical position?

The common frame of reference from which all body parts and regions are described:

• Body is standing upright, feet are shoulder width apart, with upper limbs at side of trunk and head and palms facing forward.

Positional Terms

• Supine = facing upwards

• Prone = facing downwards

• Supra = above

• Epi = above/upper • Infra = below

• Sub = below/lower

• Endo = inside

• Intra = inside

• Extra = outside

• Inter = in between

• Peri = around/surrounding

• Para = around/surrounding

Directional Terms

Another means of ensuring accurate communication, describes relative location of body parts and markings

Anterior (Ventral)

Toward the front

Examples:

• the palms are on the anterior side of the body

• the oesophagus is anterior to the spinal cord

Posterior (Dorsal)

Towards the back

Examples:

• the occipital bone is on the posterior cranium (skull)

• the spinal cord is posterior to the oesophagus

Superior (Cranial)

Towards the head

Examples:

• the nose is superior to the mouth

• the neck is superior to the chest

Inferior (Caudal)

Toward the tail

Examples:

• the nose is inferior to the forehead

• the umbilicus is inferior to the chest

Proximal

Closer to the point of origin (generally the trunk)

Examples:

• the knee is proximal to the ankle

• the shoulder is proximal to the elbow

Distal

Farther away from the point of origin (generally the trunk)

Examples:

• the foot is distal to the hip

• the wrist is distal to the elbow

Medial

Closer to the midline of the body or a body part; on the inner side

Examples:

• the ear is medial to the shoulder

• the index finger is medial to the thumb

Lateral

Farther away from the midline of the body or a body part; on the inner side

Examples:

• the shoulder is lateral to the chest

• the thumb is lateral to the index finger

Superficial

Closer to the surface

Examples:

• the skin is superficial to the muscle

• muscle is superficial to bone

Deep

Farther below the surface

Examples:

• bone is deep to the skin

• bone is deep to muscle

Regional Terms

The body can be divided into two regions:

• axial region, which includes head, neck and trunk

• appendicular region, which includes upper and lower limbs

Each broad region can be divided into several smaller regions

Cephalon

Head

• cephalic region

Cervicis

Neck

• cervical region

Thoracis

Thorax or chest

• thoracic region

Brachium

Arm

• brachial region

Ante brachium

Forearm

• ante brachial region

Carpus

Wrist

• carpal region

Manus

Hand

• manual region

Crus

Anterior Leg

• crural region

Sura

Calf

• sural region

Tarsus

Ankle

• tarsal region

Pes

Foot

• pedal regionPl

Planta

Sole

• plantar region

Abdomen

Abdominal region

Lumbus

Loin

• lumbar region

Gluteus

Buttock

• gluteal region

Pelvis

Pelvic region

Pubis

Anterior pelvis

• pubic region

Inguen

Groin

• Inguinal region

Femur

Thigh

• femoral region

Coxa

Hip

• coxal region

Planes of Section

Three primary planes of section provide a means of studying form and function of a body region by dividing body or a body part up for examination:

• sagittal

• frontal

• transverse

  • (oblique) – not pictured

Sagittal

Sagittal plane divides body or body part into right and left sections:

• Midsagittal plane (median plane) divides body or body part into equal left and right sections

• Parasagittal plane divides body or body part into unequal right and left sections

Frontal (Coronal) Plane

Divides body or body part into anterior and posterior sections

Transverse (Horizontal) Plane

Divides body or body part into superior and inferior sections or proximal and distal sections when describing structures of appendicular region

Oblique Plane

A less standardised plane, is taken at an angle; useful for examining structures that are difficult to examine using only three primary planes of section

Body Cavities

A cavity is any fluid-filled space within body; axial region of body is divided into several cavities

• Cavities protect internal organs and allow them to move and expand as necessary to perform their functions

• Major cavities include dorsal and ventral cavities and their subdivisions

Dorsal Body Cavity

Largely located on posterior side of body; subdivided into two cavities:

• Cranial cavity – within skull; protects brain

• Vertebral (spinal) cavity – within vertebral column; protects spinal cord

  • Lined with protective layers called meninges –

  • Subdivisions are continuous and filled with cerebrospinal fluid (CSF); bathes and protects both brain and spinal cord

Ventral Body Cavity

Separated into two divisions by diaphragm:

• Thoracic cavity and its subdivisions are superior to diaphragm

• Abdominopelvic cavity and its subdivisions are inferior to diaphragm

  • Lined with serous membranes termed parietal and visceral …. (dependant on location)

Ventral Body Cavity - Thoracic Cavity

Thoracic cavity – divided into three smaller cavities:

• Pleural cavities – each surround either left or right lung

• Mediastinum – between pleural cavities; houses heart, great vessels, trachea (windpipe), and oesophagus; not within serous membrane

• Pericardial cavity – within mediastinum; within serous membrane that surrounds heart Body Cavities

Ventral Body Cavity - Abdominopelvic Cavity

Abdominopelvic cavity – subdivided into superior abdominal cavity (spans from diaphragm to bony pelvis) and pelvic cavity (area within bony pelvis)

• Contains organs from several systems (digestive, lymphatic, reproductive, and urinary)

  • Peritoneal cavity – abdominal sub cavity found within serous membrane

Abdominopelvic Cavity

Abdominopelvic cavity can be divided up into segments or quadrants

Abdominopelvic Cavity

Abdominopelvic cavity can also be divided into nine segments using two parasagittal and two transverse imaginary lines: