Chapter 7
Skeletal System
Presentation by Panda Wilson
II. Introduction
Bone tissue is very active (constantly remodeling / breaking
down & rebuilding) itself.
Living tissue:
• cartilage
• dense connective tissue
• blood
• nervous tissue
Non-living (extracellular) matrix
• Collagen (for strength & resilience)
• Inorganic salts (for hardness &
resistance to crushing
Functions:
• provide points of attachment for
muscles (allowing for movement)
• protect & support softer tissues
• house blood-producing cells
• store inorganic salts (minerals)
• contain passageways for blood
vessels & nerves
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III. Bone Structure
A. Parts of a Long bone
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III. Bone Structure B, C, & E
B. Structure allows function
• Bony projections (called processes) provide points of attachment for
ligaments & tendons
• have grooves, or openings / holes (called foramen), that provide
passageways for nerves & blood vessels
• Depressions in one bone may articulate with a process of another
(forming a joint)
C. A tough, vascular covering of fibrous tissue called the periosteum
completely encloses the bone (except for the articular cartilage on
the bone’s ends).
E. Bone cells (osteocytes) are found in the lacunae (small bony
chambers forming concentric circles around central (Haversian)
canals.
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III. Bone Structure D: Compact vs Spongy Bone
Compact bone has a continuous matrix without
gaps. It typically forms the outer walls of long
bones.
Spongy bone has a lace-like appearance due
irregular connecting spaces between the branches
of thePresentation
bonybyplate.
Panda Wilson
IV. Bone Development & Growth
A. Intramembranous bones are broad, flat bones (like the bones in
the skull.
• Begin, during embryonic development, as membrane-like layers of
connective tissue
• Some of the cells enlarge & from osteoblast (“bone-forming” cells) which
deposit bony matrix around themselves forming spongy bone (spongy bone
forms in all directions within the layers of the primitive connective tissue)
• Eventually cells of the membranous tissue outside of the developing bone
give rise to the periosteum
• Osteoblasts inside the periosteum form a layer of compact bone over the
spongy bone surface
• When extracellular matrix completely surrounds osteoblast they are called
osteocytes
Presentation by Panda Wilson
IV. Bone Development & Growth
B. Most of the bones in the human skeleton are endochondral
bones. They develop from hyaline cartilage models
• The cartilage models grow rapidly for a time then the cartilage begins to
break down
• Simultaneously, a periosteum forms from the connective tissue surrounding
the developing shaft of a long bone
• Blood vessels & osteoblasts invade the disintegrating cartilage and spongy
bone; as the cartilage disintegrates, spongy bone forms in its place
• This first region of bone formation is called the primary ossification center
and bone development proceeds from this area to the ends of the bone
• The epiphysis of the bone remains cartilaginous & continues to grow
• Later, secondary ossification centers develop in the epiphysis and spongy
bone forms in all directions
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IV. Bone Development & Growth
B. continued
• A band of cartilage (called the epiphyseal plate) remains between the two
ossification centers
• This plate contains dividing cells that lengthen the bone.
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IV. Bone Development & Growth C. Ossification
1. A long bone continues to lengthen while the cartilaginous cells of
the epiphyseal plates are active. Once the ossification centers of
the diaphysis & epiphysis meet and the epiphyseal plates ossify,
lengthening stops – ossification is complete and, in healthy bone,
adult size has been reached,
2. Homeostasis in bone in a cycle of remodeling that continues
throughout life.
• Large cells called osteoclasts breakdown & resorb bone matrix and
osteoblasts replace the bone matrix
• Hormones that regulate blood calcium help control these opposing processes
• There is a 3% to 5% exchange of bone calcium per year.
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IV. Bone Development & Growth C. Ossification
• When a bone breaks, blood vessels
rupture allowing blood to escape
into the damaged area; a
hematoma (blood clot) soon forms.
• Blood vessels and osteoblasts from
the periosteum invade the
hematoma & begin forming spongy
bone.
• Meanwhile, phagocytes remove
the blood clot as well as any dead
or damaged cells in the area; and
osteocytes remove excess bony
tissue.
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V. Bone Function
A. The bones of the lower extremities, pelvis, & spine support the
weight of the body.
B. Bones that protect the viscera include:
• the skull protects the brain
• the ribs & pectoral girdle (shoulder) protect the heart & lungs, and the upper
abdominal organs
• the pelvic girdle protects the lower abdominal and internal reproductive
organs
C. Movement is produced when bones & muscles act together to form
levers; bone is moved when muscles contract and pull on the bone.
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Presentation by Panda Wilson
V. Bone Function
D. Blood Formation
1. Blood formation (hematopoiesis):
• soon after fertilization, and embryo forms and a yolk sac is formed
outside the embryo; in the embryo
initially blood is formed in the yolk sac
as the embryo develops, blood cells are formed in the liver &
spleen
still later, blood is formed in the bone marrow
• In the infant, blood is formed in the red bone marrow (found in most
bones)
• In the adult, blood is formed in the red bone marrow (found in
primarily in the spongy bone of the skull, ribs, sternum, clavicles, vertebrae, &
hipbones)
Presentation by Panda Wilson
V. Bone Function
D. Blood Formation
Red Bone Marrow functions in the Yellow Bone Marrow stores fat.
production of red blood cells
• As humans age, yellow marrow
(hematopoiesis of erythrocytes).
replaces much of the red
• In an infant red marrow occupies
marrow
the cavities of most bones
• However, if the body needs
• In an adult, found in primarily in
more blood, yellow marrow can
the spongy bone of the skull,
become red marrow (which will
ribs, sternum, clavicles,
then revert to yellow marrow
vertebrae, & hipbones
when there is enough or a
surplus of blood
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V. Bone Function
E. Inorganics in Blood
1. The major inorganic salt (mineral) stored in bone is calcium
phosphate (CaPO4)
• other salts are potassium, sodium, & carbonate ions
• heavy metals such as lead can also be found in bone
2. Calcium is released from bone by osteoclasts.
• when blood calcium levels are low, the parathyroid gland stimulates
osteoclast to breakdown bone tissue, releasing calcium into the blood stream
• as the blood calcium level rises, the thyroid gland releases calcitonin which
stimulates osteoblasts to store the excess calcium in bone tissue
3. Osteoporosis is the loss of bone volume and mineral content as
osteoclast activity increases.
• can be caused by low intake of dietary calcium, lack of physical exercise, and
in females, a decrease in blood estrogen levels
Presentation by Panda Wilson
VI. Skeletal Organization
Axial skeleton includes the head, neck,
& trunk
Appendicular skeleton includes the pelvic
& pectoral girdles and the arms & legs
• skull
• vertebral column (vertebrae)
• thoracic cage (ribs & sternum)
• pectoral girdle (shoulder) – clavicle &
scapula (2 of each)
• pelvic girdle – 2 coxae (hip bone),
sacrum & coccyx (tail bone)
• arms & hands – humerus, radius, ulna,
carpals, metacarpals, & phalanges
• legs & feet – femur, tibia, fibula,
tarsals, metatarsals, & phlalanges
Presentation by Panda Wilson
VII. Skull
A. The skull
1. There are 22 bones in the human
skull.
2. The cranium has 8 bones.
3. The face has 14 bones. Only one
of which is moveable (the
mandible)
C. The face
2. The only moveable bone in the
face is the mandible (the jaw)
3. Infants have fontanels (areas of
incomplete ossification of the
fibrous membrane) connecting
the bones (in other words, they
have soft spots) which allow
passage through the birth canal.
Also, in infants the bones are
thinner and somewhat
flexible so they are less likely
to fracture than adults.
Presentation by Panda Wilson
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• The sphenoid
bone is in the
temple region
between the
temporal &
zygomatic
bone of the
face
• The ethmoid
bone is in
front of the
sphenoid
(forms the
roof of the
nasal cavity
7 - 18
The ethmoid bone is in
the orbit of the eye .
The sphenoid bone is
in the temple region
behind
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Note the curvature of
the spine:
• convex curvature in
the cervical portion
• concave curvature in
the thoracic portion
• convex in the lumbar
• concave at coccyx
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VIII. Vertebral Column
A. The spinal column functions to support the head & trunk of the
body and to surround & protect the spinal cord.
B. Label (see textbook figure 7.17 on page 143)
C. Thoracic vertebrae (12 thoracic vertebrae)
•
•
•
•
larger than cervical vertebrae, smaller that lumbar vertebrae
body shape is triangular
the spinous process slopes inferiorly (downward)
facets on both transverse processes articulate with rib tubercules
D. Lumbar vertebrae (5 lumbar vertebrae)
• largest & strongest of the vertebrae; adapted to support more weight
• body is more oval, almost kidney-shaped
• the spinous process slopes posteriorly
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VIII. Vertebral Column
Cervical vertebrae
• These 7 vertebrae make up the bony structure of the neck
• Distinctive because they have transverse foramina which are
passageways for arteries leading to the brain
• The spinous processes of c2 thru c5 are bifid (forked)
• The C1 vertebra is called the atlas & supports the head; on its
superior surface are 2 facets that articulate with the occipital
condyles of the skull
• The C2 vertebra is called the axis. It bears a tooth-like dens (odontoid
process) that projects upward & lies in the ring of the atlas; as the
head is turned from side-to-side, the atlas pivots around the dens.
Presentation by Panda Wilson
Presentation by Panda Wilson
VIII. Vertebral Column
E. The sacrum & coccyx are at the distal end of the vertebral column:
• the sacrum
composed of 5 fused vertebrae; the spinous processes of these vertebrae
forms a ridge of tubercles
to the sides of the tubercles are rows of foramina which provide passageways
for nerves & blood vessels
• the coccyx
lowest part of the vertebral column usually composed of 4 fused vertebrae
Presentation by Panda Wilson
IX. Thoracic Cage
A. The thoracic cage consists of the thoracic vertebrae, the ribs, the
sternum, and the coastal cartilage that attach the ribs to the
sternum.
B. There are 12 pair of ribs. The first 7 pair are joined directly to the
sternum by their coastal cartilages and are referred to as true ribs.
The remaining 5 pair are called false ribs because have no direct
attachment to the sternum (their cartilages do not reach the
sternum directly).
• The upper three false ribs join the cartilages of the 7th true rib; the last
two (sometimes three) rib pairs are called floating ribs because they have
no cartilaginous attachments to the sternum.
Presentation by Panda Wilson
IX. Thoracic Cage
C. The sternum, or breast bone,
is located along the midline in
the anterior portion of the
thoracic cage. It consist of 3
parts:
• an upper manubrium (which
articulates with the clavicles)
• a middle body,
• and a lower xiphoid process.
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X. Pectoral Girdle
The pectoral girdle consist
of:
• 2 clavicles – aka collar
bones
• 2 scapulae (scapula is
singular) - aka shoulder
blade
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XI. Upper Limb
Each upper limb consists
of:
• humerus
• radius
• ulna
• wrist & hand (carpals,
metacarpals, phalanges)
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To label the diagram
You can also see
Figure 7.25 on page 150
of textbook
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XII. Pelvic Girdle
The pelvic girdle consist of 2 coxae (coxa
is singular)– aka hip bones which
articulate with each other anteriorly
and with the sacrum posteriorly.
The largest & uppermost portion of the
coxa is the ilium which flares outward
forming the prominence of the hip. The
margin of that prominence is called the
iliac crest
The lower portion of the coxa is the
ischium; the ischium is L-shaped with its
angle pointing posteriorly & downward.
The pubis is the anterior portion of the
coxa; the 2 pubic bones join at the
midline forming an arch called the pubic
arch.
Presentation by Panda Wilson
XII. Pelvic Girdle: Structure & Function
Structure
Bone
function
Acetabulum
Cup-shaped depression on the
lateral surface of the coxa
Receives the rounded head of the femur
Anterior superior
iliac spine
A projection of the ilium that
can be palpated (felt) lateral to
the groin
Provides muscle & ligament attachments that allow
movement of the femur
Ischial spine
A sharp projection on the
ischium, near the junction of
the ilium & ischium
Provides muscle & ligament attachments for the
lower limbs; also supports the weight of the body
while sitting
Obturator foramen
Located between the bodies of
the pubis & ischium
This is the largest foramen in the body! Blood vessels
& nerves supplying the leg pass through this opening.
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XIII. Lower Limb
A. The lower limb consists of:
• Femur (thigh) is the largest & strongest
bone in the body
• Patella (knee cap)
• Tibia (shin bone) on the medial side of
the lower leg
• Fibula on the lateral side of the lower leg;
the head of the fibula does not enter the
knee joint & does NOT bear any body
weight.
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XIII. Lower Limb
Presentation by Panda Wilson
XIII. Lower Limb: B. Structure & Function
Structure
Bone
function
Fovea capitis
Shallow pit on the head of the
femur
Place of attachment for the ligamentum capitis
Medial malleolus
A prominence on the distal end
of the tibia forming the inner
ankle
An attachment for the ligaments of the ankle
Lateral malleolus
Located at the distal end of the
fibula. Forms the lateral ankle
An attachment for the ligaments of the ankle
Sight of the most common ankle injury – an inversion
of the ankle
Greater & lesser
trochanters
Processes located just below the Place of attachment for the muscles of the lower
head & neck of the femur; the
limbs & buttocks
greater is superior & lateral, the
lesser is inferior & medial
Tibial tuberosity
On the tibia just below the
condyles (protuberances)
Place of attachments for patellar ligaments (knee)
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XIII. Lower
Limb: C.
Foot
Diagram (see
figure 7.32 on page
154)
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XIV. Joints: There are 3 “general” types of joints
Type of Joint
Description
Example
Possible Movement
Fibrous joint
Articulating bones that are
connected by a thin layer of
dense connective tissue.
1) Skull sutures
2) Distal ends of tibia &
fibula
1) No movement
2) Very limited
movement
Cartilaginous joint
Articulating bones that are
connected by hyaline cartilage
or fibrocartilage
1) Between vertebrae
(intervertebral disc),
2) the symphysis pubis,
joint of first rib with
the sternum
In general, limited
movements
1) For ex: bending
forward, die-to-side,
or twisting
Synovial joints
Articulating ends are covered
Most of the joints within
with hyaline cartilage (articular
the human skeletal
cartilage) and a surrounding
system are synovial joints.
tubular capsule of dense
There are 6 specific types
connective tissue called the joint of synovial joints (each
capsule. Between these two
will be described on
layers is a joint “cavity” filled
following slides.
with synovial cavity filled with
synovial fluid (~egg white
consistency)
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Allow free movement;
each type of synovial joint
allows a different type of
movement.
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Synovial Joints
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XIV. Joints: Specific Types of Synovial Joints
Type of Joint
Description
Example
Possible Movement
Synovial:
Ball-and-socket
The ball-shaped head of
one bone articulates with
the cup-like cavity of
another bone
Shoulder, hip
Movement in all planes &
rotation
Synovial:
Condyloid (aka
Ellipsoid)
An oval-shaped condyle
(protuberance or “knob”)
of one bone articulates
with an elliptical cavity of
another bone.
Between metacarpals &
phalanges (hand &
fingers)
NO ROTATION, but variety
of movements in different
planes
Synovial:
Gliding
Articulating surfaces are
nearly flat or slightly
curved
Between bones of wrists
(intercarpal) & ankles
(intertarsal); between
sacrum & ilium; between
sternum & ribs 2-7
Allow sliding & twisting
motions
Presentation by Panda Wilson
XIV. Joints: Specific Types of Synovial Joints
Type of Joint
Description
Example
Possible Movement
Synovial:
Hinge
Convex surface of one bone
articulates with concave surface
of another bone
Elbow, knee, and joints of
phalanges
Can you think of others??
Movement in one plane
only – flexion & extension
Synovial:
Pivot
Cylindrical surface of one bone
rotates within a ring formed of
bone & ligament
Between the first 2
cervical vertebrae (the
atlas & axis).
Between the proximal
ends of the radius & ulna
Allow rotation around a
central axis
Synovial:
Saddle
Both bone ends have both
convex & concave surfaces; the
surface of one bone fits the
complimentary surface of the
other.
Between the carpal
(trapezium) and
metacarpal of the thumb.
Allows a wide range of
motion.
Ever heard the term
“opposable” thumb?
Why would this be
important?
Presentation by Panda Wilson
XIV. Joints B. Structure & function
• Structure
The articulating ends of synovial joints are covered with hyaline
cartilage and a tubular capsule of dense connective tissue
surrounds them & holds them together.
The inner layer of this capsule / tube is called the synovial
membrane and it secretes synovial fluid that lubricates the
joint
Some synovial joints have fluid-filed sacs, called bursa, which
cushion shock (shoulder, knee); others have pads of
fibrocartilage, called menisci, that absorb shock (knee)
• Function
The structure described above enable synovial joints to
perform in a wide range of motions
Presentation by Panda Wilson