The Skeletal System
Bone is Connective Tissue
• The skeletal system
– The framework of bones and cartilage that
provides support, protects our organs and allows
us to move
– The skeletal system consists of several types
of connective tissue:
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cartilage,
bone,
red and yellow bone marrow,
periosteum, and the endosteum.
Functions of Skeletal System
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Support- for muscles, organs, body, teeth
Protection- for soft organs
Movement- locomotion, breathing
Blood formation- red marrow
Electrolyte balance- mineral reservoir, Ca+,
PO4
• Acid-base balance- buffers blood with alkaline
salts
• Detoxification- removes heavy metals from
blood
Bone parts
• Collagen– protein material (fibers) secreted by
osteoblasts
– Becomes bone when calcium phosphate
harden within the collagen fibers
• Osteocytes- bone cells
– Osteoblasts- build new bone (if fractures)
– Osteoclasts- clean up damaged bone
Haversion Canals
• Osteoblasts lay down collagen
• Calcium phosphate hardens in the collagen
fibers
• Osteoblasts become osteocytes
• Osteocytes are arranged in concentric circles
• Central canal is called Haversion Canal
• Haversion Canal contains blood vessels and
nerves. Oxygen and wastes are carried by the
blood to the osteocytes.
Osteocytes
More bone
periosteum
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Tough outer covering of the bone
Not on the ends of bones
Makes new bone for growth and repair
Point of attachment for muscles
Bone Tissue- Two Types
• Spongy (cancellous)
• Compact (dense)
• consists of an irregular
latticework of thin blades
of bone called
trabeculae. The spaces
between the trabeculae
contain blood vessels and
red marrow which
produces blood cells. The
spaces between the
trabeculae can be seen
with naked eye and give
spongy bone tissue its
"spongy" look.
• consists of precise
arrangements of
microscopic cylindrical
structures called
osteons. The matrix and
osteocytes of osteon are
laid down in concentric
rings around a central
(Haversian) canal that
contains blood vessels
and nerve.
Spongy Bone
Compact Bone
Marrow
• Red Marrow
– Found in the spaces within spongy bone
– Makes red blood cells, platelets, and WBC
– Found in vertebrae, ribs, breastbone, cranium
and long bones
• Yellow Marrow
– Made of fat cells
– Found in long bones
Cartilage
• Type of connective tissue
• Bends easily
• When first born the skeleton is mostly
cartilage. Slowly changes into bone by
process of ossification
• gives support with a bit of cushion
The Skeleton
• Axial Skeleton
– Skull
– Vertebrae
– Ribs
– Breastbone
(sternum)
• Appendicular
skeleton
– Arms
– Legs
– Pectoral girdle
• Scapula
• clavicle
– Pelvic girdle
• Ilium
• Ischium
• pubis
Joints
•Where bone meets
bone in an organism
Types of Joints
1. Immovable joint
2. Ball-and-socket joint
3. Hinge joint
4. Gliding joint
5. Pivot joints
Immovable Joint
• Bones that
are tightly
fitted
together
Ball and Socket joints
• Can move in all directions
Hinge Joint
• Permits
back and
forth
motion
Gliding Joint
• Provides limited flexibility
in all directions
Types of joints
Tendons and Ligaments
• Ligaments
– Connect bone to bone
– Example: cruciate ligaments connect tibia to
femur
• Tendons
– connect bone to muscle
– Example: Achilles tendon connects the calf
muscle to the heel
Muscles
Muscles
Three types of muscle:
Skeletal muscle
Smooth muscle
Cardiac muscle
Skeletal Muscle
• Voluntary (can be
controlled)
• Involved in
locomotion
• Attached to bone
• Striated in
appearance
(striped)
• Function as
Striated muscle
• Muscle fibers are
made up of myofibrils
• Myofibrils are made
up of protein filaments
– Thick myosin
– Thin actin
..\Desktop\49-31MuscleContraction.mov
Antagonistic Pairs
• Muscles work as
opposites
Ex:
1. Bicep
contracts then
triceps relaxes
2. Triceps
contracts then
the bicep relaxes
http://www.innerbody.com/anim/arm.html
Summary
• When the bicep contracts,
the arm bends upward
(flexes) and therefore the
bicep is known as a flexor
• When the triceps contracts,
the arm extends outward and
therefore the triceps is
known as an extensor
Disorders of Locomotion
1. Arthritis- inflammation of
the joints
2. Tendonitis- inflammation of
a tendon, usually where it
is attached to the bone
Smooth Muscle
• Smooth are not striated in
appearance
• Involuntary (cannot control
movement)
• Found in:
-walls of digestive organs
-walls of arteries and veins
-walls of internal organs
Cardiac Muscle
• Found only in
the heart
• Striated in
appearance
• Involuntary
• Intercalated
discs
http://www.mco.edu/cci/movies/cardiacEM.mov