Anatomy and Physiology
Chapter 7: Skeletal System
Chapter Objectives:
1. Distinguish between the axial and appendicular skeletons, and name the major parts of
each.
2. Locate and identify the bones and the major features of the bones that comprise the
skull, vertebral column, thoracic cage, pectoral girdle, upper limb, pelvic girdle, and
lower limb.
Skeletal Organization
1. Number of bones
a. Number of bones in adult human skeleton is 206
i. However, this can vary from person to person. People may lack certain
bones or have extra bones due to genetics, medical procedures, etc.
1. Ex.// flat bones of the skull tightly join together in an area called a
suture. Occasionally extra bones called sutural bones develop in
these sutures
2. Divisions of the Skeleton
a. For the purpose of study, it is easiest to divide the skeleton into two different
parts:
i. Axial Skeleton
1. Consists of bony cartilaginous parts that support and protect the
organs of the head, neck, and trunk. These parts include:
a. Skull
i. Cranium (brain case)
ii. Facial bones
b. Hyoid bone
i. Located in the neck
between the lower jaw
and larynx
ii. Does not articulate with
any other bone, but is
fixed by tendons and
ligaments
iii. Supports the tongue
c. Vertebral column
i. Consists of many
vertebrae
1. Separated by
cartilaginous
intervertebral discs
2. Forms central axis of the skeleton
3. Near distal end
a. 5 vertebrae fuse together to form the
sacrum (part of the pelvis)
b. 4 vertebrae fuse together to form a
rudimentary tailbone called the coccyx
i. Coccyx is attached to the sacrum
d. Thoracic cage
i. Protects organs of the thoracic cavity and upper
abdominal cavity
ii. Composed of 12 ribs
1. These articulate posteriorly with the thoracic
vertebrae
iii. Also includes the sternum or breastbone
1. Where most ribs are attached anteriorly
ii. Appendicular Skeleton
1. Consists of the bones of the upper and lower limbs and the bones
that anchor the limbs to the axial skeleton. It includes the following:
a. Pectoral girdle
i. Formed by the
scapula (shoulder
blade) and clavicle
(collarbone)
b. Upper limbs
i. Consists of the
humerus, radius, and
ulna
1. These bones
articulate with
one another at
the elbow joint
ii. At the distal end of the
radius and ulna is the
hand. The hand
consists of:
1. 8 carpals (wrist
bones)
2. 5 metacarpals
(palm)
3. 14 phalanges
(finger bones)
c. Pelvic girdle
i. Formed by two coxae (hipbones)
1. Attached to each other anteriorly and to the
sacrum posteriorly.
2. Form the pelvis
d. Lower limbs
i. Consists of a femur (thigh bone), tibia (shinbone), and
fibula
1. The femur and tibia articulate with each other at
the knee joint where you can find the patella or
kneecap
ii. At the distal end of the tibia and fibula is the foot. The
foot consists of:
1. 7 tarsals (ankle bones)
2. 5 metatarsals (instep)
3. 14 phalanges (toes)
 Distinguish between the axial and appendicular skeleton.
 List the bones of the axial skeleton and appendicular skeleton (main bones).
Vertebral Column
1. The vertebral column extends from the skull to the pelvis and forms the vertical
axis of the skeleton
2. It is composed of many bony parts
called vertebrae
a. Vertebrae are separated by
masses of fibrocartilage called
intervertebral discs
3. Supports head but still allows for
flexibility and rotating on the central
axis
4. Protects the spinal cord, which passes
through a vertebral canal formed by
openings or foramen in the vertebrae
5. 26 bones in adult vertebral column
6. Vertebral column has four curvatures
a. Curvatures give strength
b. The names of the curves
correspond to the regions in
which they occur
i. Cervical curvature
ii. Thoracic curvature
iii. Lumbar curvature
iv. Sacral curvature
7. Infants:
a. An infant has 33 bones in the vertebral column
i. Five of these bones eventually fuse together to form the sacrum, and
four fuse to form the coccyx
b. Curvatures
i. The cervical curvature develops when a baby begins to hold up its head
ii. Lumbar curvature develops when the child begins to stand
8. A Typical Vertebrae
a. Although vertebrae have unique characteristics, they also have many features
in common
b. A typical vertebrae has 3 parts:
i. Body
1. Large, solid
part of the
vertebrae
ii. Foramen
1. Central opening
for the spinal
cord
iii. Processes (several)
1. Above the
foramen
protrude two
winglike bony
structures
called
transverse
processes
2. The roof of the foramen contains the spinous process and the
articular processes
9. The Vertebral Column is divided into five sections named according to the area of
the body where they are located.
a. Cervical Vertebrae (7)
i. Located in neck area
ii. Atlas
1. First cervical vertebrae
that articulates with the
occipital bone of the skull
a. Allows us to nod our
heads
iii. Axis
1. Second cervical vertebrae
b.
c.
d.
e.
2. Odontoid process (dens) forms a pivot and allows us to turn our
heads
Thoracic Vertebrae (12)
i. Located in chest area
ii. Articulate with the ribs
Lumbar Vertebrae (5)
i. Located in the lower back
ii. Have large bodies and bear most of the bodies weight
Sacrum
i. Wedge shaped formed by 5 fused bones
ii. Forms the posterior pelvic girdle
iii. Serves as an articulation point for the hips
Coccyx
i. Rudimentary tailbone
ii. Formed by 4 fused bones
Thoracic Cage
1. Includes the ribs, the thoracic vertebrae, the sternum, and the costal cartilages
that attach the ribs to the sternum
2. These bones support the shoulder girdle and upper limbs, protect the viscera in
the thoracic and upper abdominal cavities and play a role in breathing
3. Ribs
a. 24 ribs
b. One pair attached to each of the 12 thoracic vertebrae
i. Some may develop extra ribs associated with their cervical or
lumbar vertebrae
ii. First 7 ribs are called, “true ribs” (vertebrosternal), join the sternum
directly by their costal cartilage
iii. The remaining 5 pair are called false ribs (vertebrochondral) join
the cartilages of the 7th rib
1. Last two have no attachments to the sternum, they are called
floating ribs (vertebral)
4. Typical rib
a. a typical rib has a long, slender shaft, which curves around the chest and
slopes downward
b. On the posterior end is an enlarged head
i. Where it articulates with the body of two different vertebrae
c. The neck of the rib is flattened
i. Ligaments attach at the edge of the flattened part
d. A tubercle, close to the head of the rib, articulates with the transverse
process of the vertebrae
e. Costal cartilages are composed of hyaline cartilage
i. Attach to the anterior ends of the ribs
5. Sternum
a. The sternum, or breastbone, is located along the midline in the anterior
portion of the thoracic cage
b. Flat, elongated bone that develops into three parts
i. Manubrium
1. The sides of the Manubrium and body are notched where they
articulate with costal cartilages
2. Manubrium also articulates with the clavicles by facets on its
superior border
ii. Body
iii. Xiphoid process
1. Begins as a piece of cartilage, slowly ossifies, and by middle
age (early-mid 20’s) it fuses with the body
Skull
1. A human skull usually consists of 22 bones that, except for the lower jaw, are firmly
interlocked along sutures
a. 8 of these interlocking bones make up the cranium
b. 14 form the facial skeleton
c. The mandible (lower jaw) is a movable bone held to the cranium by ligaments
d. Some facial and cranial bones together form the orbit of the eye
2. Cranium
a. Encloses and protects the brain
b. Its surface provides attachments for muscles that make chewing and head
movements possible
c. Some cranial bones contain air-filled cavities called paranasal sinuses
i. Lined with mucus membranes and connect by passageways to the nasal
cavity
ii. Reduce weight of skull
iii. Increase intensity of voice by serving as resonant sound chambers
d. 8 bones of the cranium
i. Frontal bone (1)
1. Forms:
a. Anterior portion of the skull above the eyes
b. Forehead
c. Roof of the nasal cavity
d. Roof of the orbits (bony sockets) of the eyes
2. On the upper margin of each orbit, the
frontal bone is marked by a
supraorbital foramen (supraorbital
notch)
a. Allows blood vessels and nerves
to pass through the forehead
3. Within the frontal bone are two
frontal sinuses (one above each eye
near the midline)
ii. Parietal bone (2)
1. One parietal bone is located on each
side of the skull just behind the frontal
bone
2. Each is shaped like a curved plate and
has four sides
3. Forms the sides and roof of the cranium
4. They are fused at the midline along the sagittal suture and meet the
frontal bone along the coronal suture
iii. Occipital bone (1)
1. Joins the parietal bones along the lambdoid
suture
2. It forms the back of the skull and the base
of the cranium
3. At the base is the foramen magnum, where
the inferior part of the brainstem connects
with the spinal cord
4. Located on each side of the foramen
magnum are occipital condyles
a. These articulate with the first
cervical vertebrae (atlas)
iv. Temporal bone (2)
1. Joins the parietal bone along the squamous suture
2. Form parts of the sides and the base of the cranium
3. Near the inferior portion, there is an opening called external acoustic
(auditory) meatus
a. Leads inward to parts of ear
4. House internal ear structure
5. Have depressions called the mandibular (glenoid) fossae that articulate
with condyles of the mandible
6. Below each external acoustic meatus are two projections
a. Mastoid Process- rounded, site for attachment for muscles of the
neck
i. May become
infected. The
tissues in this
region of the
temporal bone
contain a number
of interconnected
cells lined with
mucous
membranes that
communicate
with the inner.
These spaces
sometimes become
inflamed when
microorganisms
spread into them
from an infected
middle ear (otitis
media). The resulting
infection is called
mastioditis. Can
become a concern due
to the membranes
that surround the
brain.
b. Styloid process- pointed, anchors muscles associated with the
tongue and pharynx
7. There is an opening near the mastoid process called the carotid canal
where the carotid artery travels through
8. Another opening between the temporal and occipital bones is called the
jugular foramen where the jugular vein travels through
9. A zygomatic process projects anteriorly from the temporal bone in the
region of the external auditory meatus
a. It joins the temporal process of the zygomatic bone and helps
form the prominence of the cheek, or the zygomatic arch
v. Sphenoid bone (1)
1. Wedged between several other bones in the anterior portion of the
cranium
2. Consists of a central part and two winglike structures that extend
laterally toward each side of the skull
3. Helps form the base of the cranium,
the sides of the skull, and the floors
and sides of the orbits
4. Along the midline within the cranial
cavity, a portion of the sphenoid bone
indents to form the saddle-shaped
sella turcica
a. Within the sella turcica lies the
pituitary gland, which hangs
from the base of the brain by a
stalk
5. Also contains two sphenoidal sinuses
a. These lie side by side and are
separated by a bony septum that
projects downward into the
nasal cavity
vi. Ethmoid bone
1. Located in front of the sphenoid bone
2. Consists of two masses, one on each side of the nasal cavity, which are
joined horizontally by thing cribriform plates
a. These plates are part of the roof of the nasal cavity, and nerves
associated with the sense of smell pass through tiny openings,
called olfactory foramina.
b. Form portions of the cranial floor, orbital walls, and nasal cavity
c. A Perpendicular plate projects downward in the midline from the
cribriform plates to form most of the nasal septum.
d. Delicate, scroll-shaped plates called the superior nasal concha
and the middle nasal concha project inward from the lateral
portions of the Ethmoid bone toward the perpendicular plate.
These bony plates support mucous membranes that line the nasal
cavity
e. The lateral portions of the Ethmoid bone contain many air spaces
called ethmoidal sinuses
f. Projecting upward off of what cribriform plate is the crista galli
i. Membranes that enclose the brain attach here
3. Facial Skeleton
a. Consists of 13 immovable bones & a movable lower jaw bone (mandible)
b. Provide attachments for muscles that move the jaw and control facial expressions
c. The bones of the facial skeleton are as follows:
i. Maxillary bones
1. Maxilla
2. Form upper jaw (primarily)
3. Also forms the anterior roof of the mouth (hard palate), the floors of
the orbit, and the sides and the floor of the nasal cavity
4. Also contains sockets for teeth
5. Contains the maxillary sinuses
a. Largest of all the sinuses
6. Palatine processes grow together to form the roof of the mouth
ii. Palatine bones
1. L-shaped bone located behind the
maxillae
2. Forms portions of the hard palate and
nasal cavity
iii. Zygomatic bones
1. Responsible for the prominence of the
cheeks below and to the sides of the eyes
2. Each bone has a temporal process, which
extends posteriorly to join the zygomatic
process of a temporal bone
iv. Lacrimal bones
1. Scale like structure located in the medial
wall of the orbit
2. A groove in its interior provides a pathway for a channel that carries
tears from the eye to the nasal cavity (Lacrimal duct)
v. Nasal bones
1. Long and thin
2. Form the bridge of the nose
3. Attachment sites for cartilaginous tissue that forms the nose
vi. Vomer bone
1. Located along the midline within the nasal cavity
2. Forms nasal septum
vii. Inferior nasal conchae
1. Fragile, scroll shaped bones that attach to the lateral walls of the nasal
cavity
2. Largest of the conchae
3. Support the mucous membranes within the nasal cavity
viii. Mandible
1. Lower jawbone
2. Horseshoe shaped body with a flat ramus projecting upward.
3. The rami are divided into a
posterior mandibular
condyle and an anterior
coronoid process
a. The mandibular
condyles articulate
with the mandibular
fossae of the
temporal bones
b. Other large chewing
muscles are inserted
on the lateral surface
of the rami
4. On the medial side of the
mandible is the
mandibular foramen
a. This allows blood
vessels and a nerve
to supply the roots of the lower teeth
b. Dentists inject anesthetic into the tissues near this foramen to
temporarily block nerve impulse conduction
5. On the anterior side there is also the mental foramen which supplies
the chin with blood vessels and nerves.
Appendicular Skeleton
1. The appendicular skeleton consists of the:
a. Pectoral girdle
i. Shoulder girdle
ii. Composed of
1. Two clavicles (collarbones)
a. Slender, rod-like bones with
elongated S-shapes
b. Run horizontally between the
sternum and the shoulders
c. Medial ends of clavicles articulate
with the manubrium
d. Acromial (lateral ends) join the
processes of the scapulae
e. Help hold shoulders in place and
serves as points for muscle
attachment, however due to their
shape they can easily fracture
2. Two scapulae (shoulder blades)
a. Triangular in shape located in
the upper back
b. Each scapula is divided into
unequal portions due to a
spine
i. Above the spine is a
supraspinous fossa and
below is the
infraspinous fossa
ii. This spine leads to an
acromion process that
forms the tip of the shoulder
1. The acromion process articulates with the clavicle
and provides muscle attachment for the upper limb
and chest
iii. A coracoid process curves anteriorly and inferiorly to the
acromion process
iv. On the lateral surface of the scapula between the processes
is a depression called the glenoid cavity
1. It articulates with the head of the humerus
b. Upper limbs
i. Composed of
1. Humerus
a. Long bone that extends from the scapula to the elbow
b. At its upper end is a smooth, rounded head that fits into the
glenoid cavity
c. Just below the head are two processes
i. A greater tubercle on the lateral side and a lesser tubercle
on the anterior side
1. These provide sites for muscle attachment
ii. Between the two tubercles is the intertubercular groove
1. Allows for tendons to pass through
iii. Just below the head of the humerus is the anatomical neck
and below the tubercles is the surgical neck
iv. Along the shaft is a v-shaped area called the deltoid
tuberosity
1. Provides an attachment for the deltoid muscle which
raises the upper limb horizontally and to the side
v. At the lower end of the humerus are two smooth condyles,
a knob-like capitulum, and a pulley-shaped trochlea
1. The capitulum articulates with the radius and the
trochlea articulates with the ulna
vi. At the distal end of the humerus you can find the lateral
epicondyle and the medial epicondyle
vii. Between the condyles you can find two depressions, the
coronoid fossa that receives the coronoid process and the
olecranon fossa that receives the olecranon process of the
elbow.
2. Radius
a. Located on the thumb side of the forearm
b. Extends from the elbow to the wrist
c. Thick disc-like head articulates with the capitulum of the
humerus
d. On the radial shaft below the head is the radial tuberosity
i. Attachment site for the biceps brachii
e. At the distal end you can find a Styloid process
i. Attachment site for ligaments of the wrist
3. Ulna
a. Longer than the radius
b. At its proximal end the ulna has a wrench-like opening called the
trochlear notch
i. Articulates with the trochlea of the humerus
c. The olecranon process (elbow) located above the trochlear notch
provides an attachment site for the triceps brachii
d. At the distal end there is a knob-like head that articulates with a
disc of fibrocartilage at the wrist joint
e. Located on the ulna is also a Styloid process
i. Attachment site for ligaments
4. Carpals
a. The hand consists of 8 small carpal bones that are firmly bound
in two rows of four bones each
i. Resulting compact mass is called the carpus
5. Metacarpals
a. There are 5 metacarpals, one in line
with each finger
i. Resulting framework of the
palm is called the metacarpus
6. Phalanges
a. Finger bones
i. Three in each finger
1. Proximal phalanx
2. Middle phalanx
3. Distal phalanx
b. Polydactylism
i. An inherited trait that results
in extra digits. In humans
most extra digits are removed
at birth. Typically these
extra digits have sensation
but don’t contain joints. In
relation to genetics, it is not
a polygenic trait (a single
trait produced by many
different genes). It is
actually a mutation in one
particular gene.
ii. Most common in domestic
cats. Can be found in many
cats along the East coast of
the US and Southwest
England. History suggests
that these cats came to the
US (Colonial Boston) from England.
1. However, in England in the early 1800’s many of
these cats were killed because people associated
them with witches
c. Pelvic girdle
i. Consists of two coxae (hipbones) which articulate with the sacrum
ii. The sacrum, coccyx, and pelvic girdle together form the bowl-shaped pelvis
1. Coxae
a. Develops from three parts
i. Ilium
1. Largest and most superior portion of the coxa
2. Flares outward forming the prominence of the hip
called the iliac crest
3. Below the iliac crest is the greater sciatic notch
through which a number of blood vessels pass
ii. Ischium
1. Forms the lowest part of the coxa
2. Ischial tuberosity is the most inferior part of the
ischium
a. Has a rough surface that provides attachments
for ligaments and lower limb muscles
b. Also supports the weight of the body during
sitting
iii. Pubis
1. Constitutes the anterior portion of the coxa
2. Two pubic bones come together at a midline to form
a joint called the pubis symphysis
3. The angle these bones form below the symphysis is
the pubic arch
a. In females the pubic arch is wider than in males
due to birthing.
4. Between the bodies of these bones is the obturator
foramen
a. Largest foramen in the body
b. These parts fuse in the region of a cup-shaped cavity called the
acetabulum
i. This depression receives the rounded head of the femur
d. Lower limbs
i. Bones include
1. Femur
a. Longest bone in the body
b. Extended head at the proximal end articulates with the
acetabulum of the coxa.
c. On the head, there is a pit called the fovea capitis, which marks
the attachment for a ligament
d. Below the head is the neck and two large processes called the
greater trochanter and lesser trochanter
e. On the posterior surface of the diaphysis is the linea aspera
i. This is a rough strip located near the center of the bone for
muscle attachment
2. Patella
a. Kneecap
b. Located in a tendon that passes anteriorly over the knee
3. Tibia
a. Shinbone
b. Has two condyles that articulate
with the femur
c. Below those two condyles is the
tibial tuberosity, which provides an
attachment for the patellar ligament
(a continuation of the ligament that
contains the patella)
d. The anterior crest extends
downward from the tuberosity and
attaches connective tissue to the leg
e. At the distal end, the tibia forms a
prominence called the medial
malleolus
i. Attachment site for ligaments
ii. Articulates with fibula
iii. Articulates with tarsus (large
ankle bone)
4. Fibula
a. Located on the lateral side of the tibia
b. Its ends are enlarged to form a head on the proximal end and a
lateral malleolus on the distal end
i. Head articulates with the tibia just below the lateral
condyle
1. Does not enter into the knee joint or bear any body
weight
ii. Lateral malleolus
articulates with
the ankle and
protrudes on the
lateral side
5. Tarsals
a. Ankle, or tarsus
b. Composed of seven
tarsal bones
i. The talus can move
freely where it joins
with the tibia and fibula
ii. The largest of the tarsal
bones is the calcaneus,
or heel bone, and it sits
just below the talus
6. Metatarsals
a. Instep, or metatarsus
b. Composed of five elongated
metatarsal bones, which
articulate with the tarsus
c. Numbered 1 to 5 beginning on
the medial side
d. The heads at the distal end of
these bones form the ball of
the foot
7. Phalanges
a. Toes
b. Align and articulate with the
metatarsals
i. Clubfoot, or congenital talipes
equinovarus, is a very common
birth defect in which the foot
twists out of its normal
position. The feet can get
turned in, out, up, down, or
some combination of these
directions
1. Results from arrested
development during
fetal existence,
or Edwards
syndrome
(genetic
disorder)
2. Can be
corrected with
special shoes,
surgery, or
several months
in casts