Glossary of Human Anatomy Terms
Human anatomy is the branch of science concerned with the structure and
function of the body.
The human body is the dancer's instrument of expression. Understanding how the body works can help a dancer stay in
shape, improve performance, increase confidence and add longevity to his or her
performing career. It can also help a dancer avoid injury. If an injury does
occur, knowledge of human anatomy can contribute to a safe process of healing
and recovery.
I. General Anatomical Terms
Anatomical position: Descriptions in human anatomy are expressed in
relation to anatomical position. These positions describe where different body
parts are found or what the direction of a movement is relative to the midline
of the body or to another body part. Anatomical positions are referred to
according to their orientation:
1 Superior - toward the head
2 Inferior - toward the feet
3 Anterior - toward the front
of the body
4 Posterior - toward the back
of the body
5 Medial - toward the midline
of the body
6 Lateral - away from the
midline of the body
Body cavity: Houses the internal organs. There are three main body
cavities:
1 The thoracic cavity is the space above the diaphragm.
It encloses the heart and lungs within the ribcage, sternum (breastbone) and
twelve thoracic vertebrae.
2 The abdominal cavity, which houses the abdominal viscera,
begins below the diaphragm
and ends at the top of the pelvis, at about waist level.
3 The pelvic cavity extends from the end of the abdominal cavity to the pelvic floor.
Organ: A group of tissues that perform a particular function. For example,
the heart, lungs, liver and kidney are all organs.
Pelvic floor: A group of muscles that reach from the pubic bone back to
the sacrum.
One function of the pelvic floor is to support the internal organs.
Tissue: A group or collection of similar cells and their
intercellular substance that act together to perform a particular function. The
primary tissues are epithelial, connective, skeletal, muscular, glandular and
nervous.
Viscera: Any internal organ.
II. The Systems of the Body
System: Organs that work together to perform major body functions
like breathing, digesting, moving and reacting to external stimuli. Some
examples of systems include:
1 Cardiovascular: composed of the heart, blood and
blood vessels (arteries, veins and capillaries)
2 Digestive: composed of the oral cavity,
pharynx, stomach and intestines
3 Endocrine: involving glands that secrete
hormones
4 Integumentary: composed of skin, hair and nails
5 Muscular: composed of skeletal, smooth and
cardiac muscles
6 Nervous: composed of the brain, spinal
cord, peripheral nerves and sensory organs
7 Respiratory: composed of airways and lungs
8 Skeletal: composed of bones and cartilage
All systems are important for normal body functioning but,
for a dancer, sound knowledge of the following systems is particularly helpful:
1 The muscular and skeletal
systems are often grouped together and called the musculoskeletal system. This system's primary function is
movement.
2 The nervous system is comprised of three main parts:
a The central nervous
system involves the brain and the spinal cord.
It is the control centre of the nervous system.
b The peripheral nervous
system consists of
any nervous tissue that is not encased in the skull or vertebral column. It
includes the peripheral nerves and the sensory organs they stimulate in
different parts of the body. The peripheral nervous system is important in
balance.
c The autonomic nervous
system is chiefly
concerned with the regulation of visceral activity. It is involuntary.
III.
Bones
Bone (osseus tissue): A specialized form of dense connective tissue
consisting of bone cells (osteocytes) embedded in a matrix of calcified
intercellular substance. The main functions of bone are to:
1 Protect vital structures
2 Support the body
3 Provide a basis for movement
through muscle and tendon attachments
4 Provide attachment points
for ligaments
5 Store important mineral
salts such as calcium
6 Produce red blood cells
which transport oxygen and carbon dioxide to and from tissues
Bones give shape and structure to the body. They provide
points of attachment for muscles and become the levers making movement
possible. Bones are classified as follows:
1 Flat, e.g. scapula (shoulder blade) and
sternum (breast bone)
2 Irregular, e.g. talus (ankle bone) and
vertebrae (spinal bones)
3 Long, e.g. femur (thighbone) and ulna (one
of the forearm bones)
4 Short, e.g. navicular (a small bone in the
arch of the foot)
5 Sesamoid, e.g. patella (knee cap, where the
bone is free but a tendon runs through it)
Trochanter: A bony protuberance by which muscles
are attached between the pelvis and the upper part of the thighbone (femur).
IV. Muscles and Related Terms
Core: The dancer's centre, or core, involves a balance of stability and
strength between the abdominal muscles (transversus abdominis, rectus abdominis, and internal and
external obliques), the back muscles and the pelvic
floor muscles. The diaphragm
is also an important part of the dancer's core. A strong core is very important
in maintaining good posture
and control of limb movement.
Diaphragm: The diaphragm is the most important breathing muscle. It
spans from front to back and side to side at the level of the lower ribs. After
exhaling, the diaphragm is shaped like a dome. The lungs sit on top of the dome
and when they fill with air the dome flattens. This flattening pushes the ribs
up and out, and also pushes down on the abdominal contents, which is why the
belly gets pushed out when a deep, diaphragmatic breath is taken.
Hip joint muscles:
1 The adductors (e.g. adductor longus, adductor brevis and adductor magnus)
are the muscles running along the inside of the leg from the groin area.
Flexibility in the adductors makes it possible to do side splits.
2 The lateral rotators (e.g. piriformis and posterior fibres of gluteus medius) are
found deep in the buttock region. They are often very well developed in the
ballet dancer who performs many movements in the "turned-out"
position.
3 The medial rotators (e.g. gluteus minimus and anterior fibres of gluteus medius)
have the dual function of internal rotation (opposite to the turned-out
position) and abduction (moving the leg away from midline). They are the
antagonistic, or opposite, muscle group to the lateral rotators.
4 The extensors (e.g. gluteus maximus and the hamstrings) are used in moving
the leg backwards, in jumping and in straightening from a crouched position.
5 The flexors (e.g. iliopsoas and rectus femoris) bring the leg forward or
the knee toward the chest.
Iliotibial band: A fibrous muscle structure running from the outside of the
hip joint to the lower leg just below the knee joint. It is a continuation of
the gluteus maximus muscle, which is the largest muscle in the buttock.
Hamstring: A group of muscles found along the back of the leg running
from the pelvis to just below the knee that effect hip and knee movements.
The semitendinosus and the semimembranosus are found on the medial side
and the biceps femoris is found on the lateral side.
Muscle: Composed of contractile tissue with elastic properties.
The special characteristics of muscle include shortening and contracting, and
also stretching. In general, an overstretched or lengthened muscle is weak.
There are three kinds of muscle:
1 Smooth muscle acts involuntarily and is found principally in the internal
organs.
2 Cardiac muscle also acts involuntarily and is found around the heart.
3 Skeletal muscle is striated because of different
groups of fibres bundled together. It is usually found in the limbs. Skeletal
muscles, which produce voluntary movement, are the ones a dancer uses to gain
and maintain a certain posture,
to start and stop limb movement, and to stretch or strengthen.
Posture: Involves maintaining a certain alignment of the body. A
dancer's ability to achieve certain postures requires muscle strength and
flexibility of the musculoskeletal
system, as well as balance and body awareness involving the nervous
system.
Respiration (breathing): A means of revitalizing tissues. When a dancer
takes in air, he or she is taking in oxygen, or fuel, bringing energy to the
muscles and vital organs. Without oxygen it would be impossible to move and
control the body. Breathing also helps the dancer gain awareness of physical
states like muscle tension and relaxation.
Rotator cuff: A group of four muscles extending from the scapula
(shoulder blade) to the head of the humerus (shoulder). These muscles are very
important for stability and mobility of the shoulder throughout all movements.
The four individual muscles of the rotator cuff are the supraspinatus,
infraspinatus, teres minor and subscapularis.
Tendon: The longer fibrous end of a muscle that serves to attach
it to the periosteum (outer layer of bone). Tendons are strong, but inelastic.
They are slow to heal if injured.
A well-known tendon is the Achilles tendon, which attaches the calf
group of muscles (the medial and lateral gastrocnemius and soleus muscles) to
the heel bone (the calcaneum).
V.
Joints and Related Structures
Bursa: A padlike sac usually found near a joint. It is lined with a synovial
membrane and contains synovial
fluid that reduces friction between tendon and bone, tendon and
ligament, or other structures where friction is likely to occur. [See: Bursitis
]
Cartilage: Dense, bluish-white or grey connective tissue, like what
is seen at the end of a chicken bone. There are different types of cartilage,
including:
1 Articular, a thin layer of smooth, elastic
cartilage located on the joint surfaces of bone.
It protects the end of the joint.
2 Semilunar, found in-between the joint like the
middle of a sandwich. Two good examples are the intervertebral discs, and the
medial and lateral menisci in the knee joint.
3 Cricoid, the lowermost cartilage of the
larynx (throat).
4 Costal, connects the ends of the first ten
ribs (true ribs) with the sternum (breast bone).
Joint (articulation): The area where two or more bones
are joined together along with their associated structures, such as ligaments.
Joints are classified into three types according to the material uniting the
articulating bones:
1 Fibrous joints: united by fibrous tissue
(e.g. sutures of the skull bones).
2 Cartilaginous joints: united by cartilage
(e.g. vertebrae and their intervertebral discs) or a combination of cartilage
and fibrous tissue (e.g. sacroiliac joint).
3 Synovial joints: united by cartilage
with a synovial membrane enclosed in the joint cavity. These are the most
common joints and are the ones that provide free movement between the bones
they join. They are typical of nearly all the joints of the limbs. Synovial
joints are named after the synovial fluid they
contain. This lubricating substance allows the dancer's joints to move freely
and smoothly.
Joint axes: Joints may move in one (uniaxial) or several directions. A hinge-type
joint such as the elbow or the knee is a
bi-axial joint and permits movement in two directions: flexion or extension
only. A ball-and-socket-type joint such as the hip or shoulder is a multi-axial joint as it
allows movement in several directions.
Joint capsule: A sleeve that is over the joint. Made of fibrous tissue,
it helps keep everything in the joint together, such as the cartilage,
synovial
fluid and some ligaments.
Ligament: A band of strong, fibrous connective tissue that connects
one bone to another. Ligaments either allow or prevent a specific movement
between two bones. They are passive structures so we do not have voluntary
control over them. Examples of ligaments are the ACL (anterior cruciate
ligament) and PCL (posterior cruciate ligament). These two ligaments are found
in the knee and are called "cruciate ligaments" because they cross.
VI. Common Dance-Related Injuries
Bursitis: An acute, painful inflammation of the bursa
usually caused by repetitive friction from a tight muscle
or a poorly executed movement. Hip bursitis occurs when the tendon of the iliotibial
band rubs the greater trochanter
of the femur (thighbone).
Joint sprain: A tear of the ligament
classified from a Grade 1 (minor) to a Grade 3 (total tear). Joint sprain
occurs when a ligament is overstretched or when a joint is bent in the wrong
direction. A classic example is rolling over on the ankle. It is not uncommon
for more than one ligament to be injured at a time.
Muscle strain: A muscle
tear that can range from a Grade 1 (minor) to a Grade 3 (total tear). Muscle
strain often occurs from quick movements requiring a sudden, hard muscle
contraction, especially when a dancer is not completely warmed up.
Shin splints: Pain in the front of the lower leg. Their cause is
unclear, but they tend to develop after prolonged and/or repetitive use of the
legs in weight-bearing activities like running and jumping.
Stress fractures: An incomplete break in the bone.
In dance they are often caused by repetitive landings from jumps. On an X-ray
they appear as a thin line through the bone. In order to heal a stress fracture
it is necessary to rest and reduce impact on the fractured bone, which usually
means taking a break from dancing for a period of time. Shin splints
are one result of stress fractures.
The arch of
the foot is formed by: the structure of the bones,
the navicular being the high point of the arch; the plantar fascia, a fibrous
band extending from the heel to the ball of the foot; ligaments,
the main one being the spring ligament acting as a supporting sling to the
navicular bone; and muscles
both starting and ending in the foot, as well as muscles originating from the
lower leg area. The primary role of the long arch of the foot is to absorb
shock.
The arm is divided into two parts: the upper arm and the forearm. The
long bone of the upper arm is called the humerus and extends from the ball-and-socket
multi-axial-type shoulder joint to the hinge-type elbow joint. The forearm
consists of two bones, the ulna and the radius,
which extend from
the elbow to the wrist. The main muscles in the upper arm are the deltoids,
triceps and biceps. The muscles of the forearm mostly start at the elbow and
continue into the hand controlling movement of the wrist and hand.
Arteries are blood
vessels containing oxygenated blood that is pumped from the heart to other organs
of the body. After the organs have taken the oxygen out of the blood for fuel,
another set of blood vessels called veins carry
the de-oxygenated blood back to the heart, thereby completing the circuit.
Normal body
temperature for a healthy adult at rest is 37
degrees Celsius.
The scapula or shoulder blade acts like a
pulley and has muscle attachments to the head, neck, spinal column, sacrum
and upper arm.
The spine is made up of seven cervical, twelve thoracic and five lumbar
vertebrae; the sacrum (five fused vertebrae); and the coccyx (four fused vertebrae), which is
the remnant of the human tail. The spinal cord running down the centre of the vertebrae is a continuation of
the brain and ends at L1-L2 (the 1st and 2nd lumbar vertebrae). The rest of the
spinal column after L2 is filled with a bunch of nerves that look like a
horse's tail and is called the cauda equina.
The human body has different structural levels of organization. These levels start with atoms,
molecules and compounds, increasing in size and complexity to cells, tissues,
organs and, finally, systems.
VIII.
References
Calais-Germain, Blandine. Anatomy of Movement. Seattle:
Eastland Press, 1993
Calais-Germain, Blandine and Anderson, Stephen. Anatomy of
Movement:
Exercises,
Seattle: Eastland Press, 1996
Carola, R., Harley, J.P., and Noback, C. Human Anatomy. New
York: McGraw
Hill, 1992
Kapit, Wynn and Elson, Lawrence M. The Anatomy Coloring
Book, 3rd edition.
Benjamin Cummings, 2001.