CHAPTER 5
Cartilage and Bone
97
Types of Bone
Gross Appearance
(Shape)
Characteristics
Main Locations
Main Functions
Classif cation Based on Gross Appearance
Compact bone
Uniform; no trabeculae and
spicules
Higher density; lamellae
arranged in circular pattern
Outer portion of
the bone (cortical
bone)
Protection and support
Cancellous
(spongy) bone
Irregular shape;
trabeculae
and spicules present;
surrounded by the bone
marrow cavities
Lower density; lamellae
arranged in parallel pattern
Inner core of the
bone (medullary
bone)
Support; blood cell
production
Classif cation Based on Shape
Long bone
Longer than it is wide
Consists of diaphysis (long
shaft) and two epiphyses at
the ends
Limbs and F ngers
Support and movement
Short bone
Short, cube shaped
A thin layer of compact
bone outside and thick
cancellous bone inside
Wrist and ankle
bones
Movement
±lat bone
±lat, thin
Two parallel layers of
compact bone separated by
a layer of cancellous bone
Many bones of the
skull, ribs, scapulae
Support; protection
of brain and other
soft tissues; blood cell
production
Irregular bone
Irregular shape
Consists of thin layer of
compact bone outside and
cancellous bone inside
Vertebrae and
bones of the pelvis
Support; protection
of the spinal cord and
pelvic viscera; blood
cell production
Classif cation Based on Microscopic Observation
Primary bone
(immature
bone)
Irregular arrangement
Lamellae without
organized
pattern; not heavily
mineralized
Developing fetus
Bone development
Secondary bone
(mature bone)
Regular arrangement
Well-organized lamellar
pattern; heavily mineralized
Adults
Protection and support
TABLE 5-2
Bone
SYNOPSIS 5-4
Pathological and Clinical Terms for Cartilage and Bone
Eburnation
: In osteoarthritis, the loss of the articular cartilage results in the exposure of the subchondral bone, which
becomes worn and polished (±ig. 5-4B).
Fibrillation
: Early degenerative change in the process of osteoarthritis by which the articular cartilage becomes worn and
produces a papillary appearance; fragments of degenerated cartilage may be released into the joint space (±ig. 5-4B).
Neoplasm
: Abnormal tissue arising from a single aberrant cell; neoplasms may be benign or malignant. Malignant
neoplasms are capable of destructive growth and metastasis (±ig. 5-13B).
Achondroplasia
: An autosomal-dominant genetic disorder that causes dwarF
sm. The F
broblast growth factor receptor
gene 3 (±G±R3) is affected, resulting in abnormal cartilage formation and short stature.
Osteoporosis
: A bone disease characterized by reduced bone mineral density, thinned bone cortex, and trabeculae. It causes
an increased risk of fracture, especially in postmenopausal women.
Osteomalacia
: A bone condition caused by impaired mineralization. It causes rickets in children and bone softening in
adults. Vitamin D deF ciency and insufF cient Ca
++
ions are the most common causes of the condition.
Paget disease
: A chronic disorder characterized by excessive breakdown and formation of bone tissue that typically results
in enlarged and deformed bones. The blood alkaline phosphatase level in patients is usually above normal.
Parosteal osteosarcoma
: A malignant bone tumor, usually occurring on the surface of the metaphysis of a long bone
(±ig. 5-8).
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