The Skeletal System
I. Introduction and Development
II. Articulations
III. Bone Repair and Diseases
Introduction
Skeletal Options:
1. Don't bother!
2. Exoskeleton
3. Endoskeleton
Functions of the
Skeletal System
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Support and protection
Body movement
Hematopoiesis (In red marrow)
Storage
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Yellow marrow stores fat
Ca++, CO3--, Mg++, Na+, K+ in matrix
Bone composition
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Osteocytes embedded in matrix, sitting in
lacunae
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Matrix = Organics (collagen) + inorganics (Ca+
+ and phosphate salts )
Histology
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Osteoblasts, Osteoclasts
Osteocytes
Cannaliculi connect osteocytes
Osteonic / Haversian / Central Canal = blood and
nerve supply for osteocytes
Parts of a long bone
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Epiphysis, Diaphysis
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Medullary cavity w/ yellow marrow
Articular cartilage = layer of hyaline cartilage
that coats the epiphyses
Periosteum = outer layer; contains osteoblasts
Endosteum = inner layer; contains osteoclasts
Intramembranous Bone
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Develops from layers of connective tissue
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Occurs in cranial roof and some facial bones
Osteoblasts within the membranes lay down
bone, become trapped and mature into
osteocytes
Endochondral Bone =
Hyaline cartilage that becomes bone
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Chondrocytes build a framework
Osteoblasts replace them
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Primary ossification center = diaphysis
Secondary ossification = epiphyses
Ephyseal disk remains
Long bones stop growing once the ephyseal
disks ossify
Skeletal System Rules
1. Most of our bones and skeletons are real. They
are from real people. They are also really
expensive. Treat them with respect and dignity.
Carry them with two hands. The skull caps come
off. Be gentle.
2. At no time will pencils, pens, probes or other
sharp objects be allowed near the bone collection.
3. Only fine paintbrushes and Q-tips shall be used
to point.
4. When you come to open lab hours, bring your
own paintbrush / Q-tip.
5. Anyone who violates these rules will give up
their right to access these specimens.
Skeletal System II:
Articulations and Movement
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Arthros = joint
Joints are classified in 2 ways:
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1. type of tissue that binds the bones
together
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2. the type of movement the joint allows
Fibrous Joints
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most are non-movable
joints
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bones joined together
by a layer of fibrous
connective tissue
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sutures in the skull,
periodontal membranes,
distal ends of tibia/fibula,
middle of radius / ulna
Cartilaginous Joints
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usually slightly movable
joints
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intervertebral disks, pubic
symphysis
Synovial Joints
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freely movable joints
have lots of accessories:
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1. articular cartilage
2. synovial capsule
3. articular disks
4. bursae
5. tendon sheaths
Types of Movement
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1. Linear Motion = Gliding
2. Angular Motion
3. Rotation
Gliding joints
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Linear motion
Bones in the
carpals, tarsals, end
of the clavicles,
between vertebrae
Hinge joints
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Angular motion
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knee, elbow
Pivot joints
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Rotation
Between the atlas
and axis
Saddle joint
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Between the
carpal and
metacarpal of
the thumb
Ball-and-socket joint
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Circumduction
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Shoulder and hip
Condyloid
(Ellipsoidal) Joint
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Angular motion
Between
metacarpals and
phalanges, and
occipital condyles
Types of Movement
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Flexion / Extension / Hyperextension
Dorsiflexion / Plantar flexion
Abduction / Adduction
Rotation
Pronation / Supination
Inversion / Eversion
Retraction / Protraction
Elevation / Depression
Skeletal System III: Bone Repair and Bone
Diseases
Bone Fractures
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Treatment is called
reduction
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a. closed = by
hand
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b. open = surgery
Cast
Humerus spiral fracture
Types of Fractures
Repair of bone fractures:
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1. Hematoma (blood-filled swelling)
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4. Remodeling (osteoblasts, osteoclasts)
2. Fibrocartilage callus splints the broken bone
3. Bony callus forms, replacing the
fibrocartilage
Rickets
Osteomalacia
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soft bones, bowllegs
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due to deficiency of
calcium or vitamin
D
Osteoporosis
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bone atrophy
estrogen loss, diets
low in calcium and
protein, smoking
and lack of exercise
Osteomyelitis
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inflammation of bone due to infection by
bacteria, virus
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treatment difficult
Bone cancers
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if originating in bone tissue, usu. in children,
teens
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many other cancers metastasize to bone
Arthritis
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Osteoarthritis
(OA)
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articular cartilage
gets soft, frayed and
breaks down
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bone spurs
Rheumatoid Arthritis
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Immune system attacks
the articular cartilage.
Scar tissue forms and
connects the bones
together, until
eventually they fuse.
Gouty Arthritis
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uric acid collects in the
blood and is deposited
as crystals in soft joint
tissues
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treated w/ drugs, diet
restrictions, weight
loss if needed