The SKELETAL SYSTEM
The skeletal system includes the bones of the
skeleton, joint capsules, and other tissues that
connect and stabilize the system such as
cartilages and ligaments. The functions of the
skeletal system include: (a) support of the body
and its parts; (b) protection of various body
structures; (c) leverage for the functioning of the
muscular system; (d) storage of minerals and
energy; and (e) blood cell production.
Bones can be classified based on their shape
and location. Long bones are, just as the name
implies, longer than they are wide. Short bones
are boxy in appearance. Flat bones are plate-like
and relatively thin. There are also bones that do
not fall into these categories; these are known as
irregular bones. Sesamoid bones are round and
flat and develop within tendons.
Each bone has markings that distinguish it
from other bones. These markings are used to
identify the individual bones of the skeletal
system. Below is a list of the various types of
bone markings.
Condyle: a large, rounded articular
prominence
Epicondyle: a prominence above a condyle
Facet: a smooth, flat surface
Foramen: an opening through which blood
vessels, nerves, or ligaments pass.
Fossa: a depression in or on a bone
Groove or Sulcus: a furrow or elongated
depression that accommodates a soft
structure such as a blood vessel, nerve, or
tendon.
Head: a rounded articular projection supported on a constricted portion, the neck,
of a bone
Meatus: a tube-like passageway running
within a bone
Sinus: an air filled cavity within a bone
Spine: a sharp, slender process
Trochanter: a large projection found only on
the femur
Tuberosity: a large, rounded, usually
roughened process
Tubercle: a small rounded process
The skeleton is divided into two major
divisions: the axial skeleton and the
appendicular skeleton. The axial skeleton
consists of bones that form the central axis of the
body. It consists of the skull, vertebral column,
hyoid bone and rib cage. The appendicular
skeleton contains the bones of the pectoral (or
shoulder) girdle, upper extremities; the pelvic
girdle and lower extremities.
From the following list, be able to identify
each bone and its parts, the articulations that the
bone forms and the possible actions at freely
movable and slightly movable joints. As you do
this consult your text as a reference.
THE APPENDICULAR SKELETON
I. The Pectoral Girdle
A. Clavicle: a long slender “S” shaped bone
B. Scapula: a large triangular flat bone on
the posterior part of thorax
1. spinous process: sharp ridge diagonal
across posterior surface
2. acromion process: flattened expanded
process projecting from lateral end of
spinous process
3. coracoid process: projection on anterior
surface at lateral end of superior border
4. glenoid fossa: inferior to acromion
process and articulates with humeral
head to form shoulder joint
II. Arm
A. Humerus: the single bone of the arm
1. head: rounded proximal end that
articulates with glenoid fossa
2. capitulum: rounded knob that
articulates with radius
3. trochlea: pulley-like surface that
articulates with ulna
4. medial and lateral epicondyles: bony
projections at distal
5. olecranon fossa: accommodates
olecranon when forearm is extended
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III. Forearm
A. Ulna: medial bone of forearm
1. olecranon process: prominence of
elbow at proximal end
2. trochlear notch: large curved area on
anterior aspect; articulates with humeral
trochlea
3. radial notch: curved lateral area
allowing articulation of radial head
4. ulnar head: expanded distal end
5. styloid process: medial point at distal
end
B. Radius: lateral bone of forearm
1. head: disc-shaped proximal end
2. ulnar notch: at distal end allowing
articulation of ulna
3. styloid process: lateral point at distal
end
IV. Wrist and Hand
A. Carpals: the eight bones of wrist
(know them as a group)
B. Metacarpals: five bones that constitute
palm of hand; identified as I, II, III, IV,
and V, from lateral to medial
C. Phalanges: bones of digits; each digit has
a proximal and distal phalanx and each
finger also has a middle phalanx
V. Pelvic Girdle
A. Coxal (or Innominate) Bone: hip bone
which is formed by fusion of three separate
bones during development
1. ilium: superior portion
a. iliac crest: superior border
b. greater sciatic notch: large indentation just inferior to the posterior
point of iliac crest
c. iliac fossa: smooth, slightly concave
anteromedial surface
2. ischium: inferior, posterior portion
a. ischial tuberosity: large roughened
area on inferior most part of coxal
bone; bares body weight during
sitting
b. obturator foramen: large round
opening formed posteriorly by
ischium and anteriorly by pubis
3. pubis: inferior, anterior portion
4. acetabulum: deep depression which
receives head of femur to form hip
joint
The two coxal bones, with the sacrum and
coccyx of the spine, form the pelvis, a bowllike structure. The broad flare of the pelvis is
the greater (or false) pelvis while to narrow
part is the lesser (or true) pelvis. These are
separated by the pelvic brim. The superior
opening of the pelvis, defined by the brim, is
the pelvic inlet; the inferior opening is the
pelvic outlet. Be able to distinguish a male
from a female pelvis.
VI. Thigh
A. Femur: single bone of thigh
1. head: rounded proximal end that
articulates with acetabulum of pelvis
2. neck: constricted “stem” just distal to
head
3. greater trochanter: large projection on
lateral aspect which points superiorly
4. lesser trochanter: large projection
inferior and medial to greater trochanter
5. medial and lateral condyles: large
rounded surfaces at distal end which
articulate with tibia
6. intercondylar fossa: posterior groove
between condyles
7. medial and lateral epicondyles: rough
projections on either side of distal end
just proximal to respective condyles
B. Patella: sesamoid bone on anterior side of
knee
VII. Leg
A. Tibia: larger, medial bone of leg
1. medial and lateral condyles: expanded
area at proximal end which articulates
with respective condyles of femur to
form knee joint
2. tibial tuberosity: roughened area on
anterior surface serving as a point of
attachment for patellar ligament
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3. medial malleolus: projection at distal
end which articulates with foot’s tarsals
to form part of ankle joint
B. Fibula: smaller, lateral bone of leg
1. lateral malleolus: distal enlargment
which articulates with foot’s tarsal to
form ankle joint
VIII. Ankle and Foot
A. Tarsals: seven bones of ankle area of
foot (know them as a group)
B. Metatarsals: five bones of mid-foot;
identified as I to V from medial aspect
C. Phalanges: bones of toes; each toe has a
proximal, middle and distal phalanx except
the hallux which does not have a middle
phalanx
AXIAL SKELETON
I. Cranium: portion of skull that encloses brain
A. Frontal Bone: single anterior bone of
cranium forming forehead and roof of
orbits
1. frontal sinuses: cavities within frontal
bone which are continuous with nasal
cavity
2. coronal suture: joint that separates
frontal bone from parietal bones
B. Parietal Bone: paired bones posterior to
frontal bone; constitute the greater portion
of sides and roof of skull
1. sagittal suture: joint that separates left
and right parietal bones
2. squamous suture: joint that separates
parietal bone from temporal bone
3. lambdoid suture: joint that separates
parietal bones from occipital bone
C. Temporal Bones: paired bones inferior to
parietal bones; constitute greater portion of
inferior sides and floor of cranium
1. zygomatic process: projects from inferior area of flat portion; articulates
anteriorly with zygomatic bone to form
zygomatic arch
2. mandibular fossa: oval depression just
inferior to base of zygomatic process;
articulates with mandible
3. external auditory meatus: canal-like
opening just posterior to mandibular
fossa; serves as a passageway for sound
waves to reach “eardrum”
4. internal auditory meatus: small opening
inside cranium superior to jugular foramen; allows for passage of auditory
nerve
5. mastoid process: rounded projection
posterior to exteranl auditory meatus
6. styloid process: sharp projection from
inferior surface
7. stylomastoid foramen: small opening
between styloid and mastoid foramena
8. carotid canal: round smooth opening
from inferior surface; allows passage of
internal carotid artery
9. jugular foramen: opening just posterior
to carotid canal with an irregular edge;
allows passage of the internal jugular
vein
D. Occipital Bone: single posterior bone of
cranium
1. foramen magnum: single large opening
in floor of skull which allows passage
of spinal cord
2. occipital condyles: oval processes on
either side of foramen magnum; articulates with vertebral column
3. hypoglossal canal: at anterolateral edge
of occipital condyles
E. Ethmoid Bone: single bone in anterior
part of cranial floor between orbits
1. cribiform plate: perforated horizontal
plate in anterior floor of cranium; forms
roof of nasal cavity; perforations allow
passage of olfactory nerves
2. perpendicular plate: projects inferiorly
in middle of bone, forming superior
portion of nasal septum
3. superior and middle nasal conchae:
thin scroll-like projections on either side
of nasal septum; aid in warming and
humidifying incoming air
F. Sphenoid Bone: single bone that lies in
middle portion of cranial floor
1. sella turcica: medial depression on
superior surface; houses pituitary gland
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2. greater and lesser wings: outstretched
processes of sphenoid forming part of
middle cranial and anterior cranial
fossae, respectively
3. optic foramen: small round opening
allowing passage of optic nerve
4. foramen rotundum: small round opening inferior to lesser wing
5. foramen ovalea: oval opening on floor
of greater wing
6. sphenoid sinus: found in central portion of bone, just deep to sella turcica
II. Facial Bones
A. Nasal Bones: paired bones that meet in
middle and superior portion of the nose
form bridge of nose
B. Lacrimal Bones: paired bones found
posterior and lateral to (but not in direct
contact with) nasal bones
1. lacrimal foramen: opening allowing
passage of lacrimal duct to nasal cavity
C. Zygomatic Bones: paired bones that form
prominences of cheeks
D. Maxillae: paired bones forming upper
jaw; forms part of floor of orbit, lateral
walls and floor of nasal cavity and most of
hard palate
1. alveoli: sockets for teeth
2. palatine process: horizontal projections
that form anterior two-thirds of hard
palate
3. maxillary sinuses: cavity in each
maxilla that opens into nasal cavity
E. Palatine Bones: paired “L” shaped bones
that form posterior one-third of hard palate
F. Vomer: single triangular bone that forms
inferior and posterior portions of nasal
septum
G. Inferior Nasal Conchae: paired scroll-like
bones forming part of lateral wall of nasal
cavity serving same functoin as superior
and middle nasal conchae
H. Mandible: the lower jaw
1. alveoli: sockets for teeth
2. body: curved horizontal portion
3. ramus: perpendicular portion on either
side of body
4. condylar process: posterior branch of
ramus ending in round mandibular
condyle, which articulates with mandibular fossa
5. coronoid process: pointed anterior
branch of ramus
III. Hyoid Bone: single “U” shaped bone
located between mandible and larynx; does
not articulate with any other bone
IV. Vertebral Column
composed of a number of different bones
known as vertebrae
vertebral column is divided into five sections,
each having a specific number of vertebrae
all vertebrae have common characteristics
vertebrae of each section have unique
characteristics
A. Common Characteristics
1. body (or centrum): thick disc-shaped
anterior portion
2. vertebral foramen: opening through
which the spinal cord passes
3. intervertebral foramen: opening formed
by two articulating vertebrae allowing
passage of single spinal nerve
4. transverse processes: paired processes
on either side of a vertebra
5. spinous process: single process projecting posteriorly from the vertebra
B. Cervial Vertebrae: there are seven
cervical vertebrae
1. each transverse process has an opening
called transverse foramen
2. spinous process is often branched
3. atlas: first vertebra; articulates with
occipital bone superiorly; lacks a body
and spinous process
4. axis: second vertebra; dens or odontoid
process projects superiorly to articulate
with anterior portion of vertebral
foramen of atlas forming a pivot joint
C. Thoracie Vertebrae: there are twelve
thoracic vertebrae
1. transverse process has articulating
surface for ribs called facets
2. body has superior and inferior articulating surfaces for ribs called demifacets
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D. Lumbar Vertebrae: there are five lumbar
vertebrae
E. Sacral Vertebrae: four or five sacral vertebrae; these fuse into a single unit, the
sacrum; articulates with posterior ilium of
coxal bone
F. Coccygeal Vertebrae: four or five coccygeal vertebrae fused into a single unit, the
coccyx; extends from sacrum
V. Thorax
A. Sternum: flat, narrow bone located in
median line of anterior thoracic wall
1. manubrium: superior portion with a
depression on superior border
2. body or gladiolus: middle, larger
portion
3. xiphoid process: inferior portion
(used as a landmark for CPR)
B. Ribs: twelve pairs of flat bones that
make up thoracic wall; first seven rib pairs
are vertebrosternal (or true) ribs because
they have a direct anterior attachment to
sternum through strips of hyaline cartilage;
last five rib pairs are false ribs; of these,
first three pairs attach to the cartilage of
the seventh pair, called vertebrochondral
ribs; last two pair are vertebral (or
floating) ribs because they do not have an
anterior attachment
ARTICULATIONS
and BODY MOVEMENTS
I. Synarthrosis: also called immovable joints;
most are fibrous joints.
A. Suture: occurs between flat bones;
united by sutural ligaments; no movement occurs.
B. Gomphosis: cone-shaped process of
teeth fastened in a bony socket by a
peridontal ligament; no movement
occurs.
C. Synchondrosis: bones united by bands
of hyaline cartilage; movement can
occur during growth but not after
occification occurs; found at growth
plates.
II. Amphiarthrosis: also called slightly moveable joints; a pad or disc of fibrocartilage is
often present.
A. Syndesmosis: bones bound by interossious ligament; flexible, may twist;
found between radius and ulna; fibula
and tibiaand
B. Symphysis: articular surfaces separated by fibrocartilage.
III. Diarthrosis: also called freely movable
joints (don’t take the term to literally); most
common type of joint in animals.
A. Ball and Socket Joint: ball-shaped
head of one bone articulates with the
cup-shaped socket of another; allows
flexion and extension; abduction and
adduction; rotation; circumduction;
found at the hip and shoulder.
B. Hinge Joint: convex surface of a bone
articulates with the concave surface of
another; allows flexion and extension;
found between phalanges of digits;
trochlea of humerus and trochlear notch
of ulna; between femoral and tibial
condyles and between distal tibia-fibula
and proximal tarsal.
C. Gliding Joint: articulating surfaces are
flat or slightly curved; allows a little
movement in all directions; found
between the carpals and between the
tarsals; articular processes of vertebrae.
The temporomandibular joint is a combination hinge and gliding joint.
D. Pivot Joint: cylindrical surface of a
bone articulates with ring bone and
fibrous tissue; allows rotation; found
between atlas and dens of axis; radial
head and radial notch of ulna; ulnar
notch of radius and ulnar head
E. Ellipsoid (or Condyloid) Joint: oval
shaped condyle of a bone or group of
bones articulates with elliptical cavity
of another; allows flexion and extension; abduction and adduction; circumduction; found between distal end
metacarpals and proximal phalanges;
between distal end of radius and the
carpals
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F. Saddle Joint: articulating surfases
have both concave and convex regions
which fit complimentary to one another; found between proximal end of
metacarpal I and carpals
The HUMAN KNEE
I. Bones
A. Femur: at proximal side.
B. Tibia: at mediodistal side.
C. Fibula: at laterodistal side.
D. Patella: within patellar ligament.
II. Ligaments
A. Quadriceps Tendon: insertion of quadriceps femoris muscle of thigh; ends at
patella.
B. Patellar Ligament: continuation of
quadriceps ligament; begins at patella;
attaches to tibial tuberosity.
C. Tibial and Fibular Collateral Ligaments:
proximal ends attached to respective femoral epicondyles; distal end attached to
respective bones.
D. Anterior and Posterior Cruciate Ligaments: proximal end of both attached to
posterior femur in intercondyler space;
posterior cruciate attached distally on
posterior tibia; distal side of anterior
cruciate anteriorly between tibial condyles.
III. Articular Pads: made of fibrocartilage
A. Medial Meniscus: C-shaped ring.
B. Lateral Meniscus: complete ring.
IV. Movement: The knee is considered a hinge
joint, allowing flexion and extension of the
leg. However, it is a unique hinge joint in
that there is slight rotation in one plane as one
pushes off during walking and rotation in a
different plain as one plants the foot to
complete the step.
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