40 Introduction to Medical Terminology
Copyright Goodheart-Willcox Co., Inc.
the delicate spinal cord. Between most vertebrae
lie intervertebral (IN-ter-VER-tuh-bruhl) disks,
which are composed of cartilage and act as shock
absorbers, allowing for movement of the spinal
column. Bones that comprise the spinal column
include the following:
• Seven cervical vertebrae, also known as the
C-spine (C1–C7), make up the neck region of the
spine.
• Twelve small bones form the thoracic vertebrae,
also known as the T-spine (T1–T12). The thoracic
vertebrae connect to the ribs.
• Continuing down the spinal column, the next
fi ve vertebrae make up the lumbar vertebrae,
known as the L-spine (L1–L5). The lumbar ver-
tebrae, which curve in the lower back, are the
strongest and largest vertebrae.
• The sacrum (SAY-krum), or S-spine, is a slightly
curved, triangular-shaped bone composed of
fi ve segments that gradually fuse together to
become one. This fusion process takes place
during childhood.
• The coccyx (KAHK-siks) is made up of four
small bones that fuse to become the tailbone.
This fusion of coccygeal (kahk-SIJ-ee-uhl) ver-
tebrae typically occurs in early adulthood.
Appendicular Skeleton
The appendicular skeleton is made up of
126  bones that attach to the axial skeleton as
appendages. The appendicular skeleton comprises
the shoulder girdles, arms, wrists, and hands in the
upper part of the body and the pelvic girdle, legs,
ankles, and feet in the lower part of the body.
Shoulder Girdle
The shoulder girdle is composed of bones that
support attachment of the upper extremities to the
axial skeleton. The bones that make up the shoul-
der girdle include the clavicle, commonly known
as the collarbone; the sternum (breastbone); and
the scapula, or shoulder blade. (See Figure 2.1.)
The clavicle connects the sternum to the scapula.
Upper Extremities
The bones of the upper extremities, shown in
Figure 2.1, are as follows:
• The humerus is the upper arm bone.
• The radius is the smaller bone found on the
thumb side of the forearm.
• The ulna is the larger forearm bone. The proxi-
mal end of the ulna forms the elbow.
• Eight carpal bones make up the wrist.
• Five metacarpals (MET-uh-KAR-puhlz) form
the bones of the hand.
• Fourteen phalanges (fuh-LAN-jeez) make up
the fi nger bones; each fi nger (except the thumb)
has three phalanges: proximal, medial, and dis-
tal. The thumb has only two phalanges: the
proximal and distal phalanges.
Humans and giraffes have the same number of
bones in their necks, but the vertebrae in a giraffe’s
neck are much, much larger.
Fascinating Fact
Of the 206 bones in the adult body, 54 of them are
in your hands—27 in each hand.
Fascinating Fact
Cervical region
C5
C6
C7
T1
T2
T3
T5
T4
L1
L2
L3
L5
L4
T6
T7
T8
T9
T10
T11
T12
C1
C2
C3
C4
Thoracic region
Lumbar region
Sacrum
Cervical curve
Thoracic curve
Lumbar curve
Sacral curve
Coccyx
Figure 2.9 The vertebral (spinal) column, lateral view.