Download Chapter 2 Skeletal system

Chapter 2
Skeletal system
Anatomy and physiology
• Skeletal system composed of 206 separate bones.
• Bone is a type of connective tissue its matrix consists of
calcium phosphate.
Periosteum: fibrous membrane that encloses all
of the bone except the joint surface and is crucial
in supplying blood to the underlying bone
Tissue types
• Epithelial tissue: covers the body surface and forms the lining
for most internal cavities. The major function of epithelial
tissue includes protection, secretion, absorption, and
filtration. The skin is an organ made up of epithelial tissue
which protects the body from dirt, dust, bacteria and other
microbes that may be harmful.
• Connective tissue is the most abundant and the most widely
distributed of the tissues. Connective tissues perform a variety
of functions including support and protection. The following
tissues are found in the human body, ordinary loose connective
tissue, fat tissue, dense fibrous tissue, cartilage, bone, blood,
and lymph, which are all considered connective tissue.
Tissue types cont.
• There are three types of muscle tissue: skeletal,
smooth, and cardiac. Skeletal muscle is a voluntary type of
muscle tissue that is used in the contraction of skeletal
parts. Smooth muscle is found in the walls of internal organs
and blood vessels. It is an involuntary type. The cardiac
muscle is found only in the walls of the heart and is
involuntary in nature.
• Nerve tissue is composed of specialized cells which not only
receive stimuli but also conduct impulses to and from all parts
of the body.
Skeletal system
Axial skeleton
80 bones
Appendicular skeleton
126 bones
Anatomy of Bone
periosteum
cancellous
Osteoblasts
Are bone forming cells that line the medullary canal and are
Interspersed throughout the periosteum.
They are responsible for bone growth and thicknening.
Osteoclasts
Is a type of bone cells that removes (old) bone tissue by breaking down bone and
releasing minerals resulting in transferring calcium from bone fluid to the blood
(bone resorption) its function is maintenance and repair.
Osteoclasts and osteoblasts are instrumental in controlling the amount of bone
tissue.
Osteoblasts form bone, osteoclasts resorb bone.
The bones of the skeletal system may also classified according to their shape
Epiphysis
Metaphysis
Growth zone bet.
Epi.&Dia.
Diaphysis
Bone Radiography
Plain Films:
• Good for fracture, dislocation, tumors.
Bone Scan:
• Allows screening entire skeleton.
• Good for metastatic disease.
• Helps answer whether osteomyelitis.
CT:
• Allows cortical disruption, soft tissue extension to be assessed.
MR:
• Good for assessing marrow involvement.
• Good for soft tissues around joint (collateral ligaments, menisci in
knee)
Normal Bone Appearance
• The radiographic image of the bone is due to its calcium
content.
• Pathological lesions will be visible when there are:
• Change in structure continuity (as in fractures).
• Change in position (as in dislocations).
• Change in shape (as in congenital development defects).
• Lessening of density (reduced radio-opacity).
• Localized demineralization with disappearance of the trabeculae
(bone erosion).
• Increased density from a high calcium content (bone sclerosis).
• New bone formation.
Metabolic bone disease
Generalized reduction of bone
density
The main causes of generalized reduction in bone
density are:
• Osteoporosis.
• Osteomalacia and rickets.
• Hyperparathyroidism.
• Gout
• Paget disease
Osteoporosis-disease characterized
by low bone mass & structural
deterioration of bone tissue
normal bone
osteoporotic bone
Bone is a living, constantly changing tissue, and normally a
balance exists between the amount of old bone being removed
(an osteoclastic process) and the amount of new bone
replacement (an osteoblastic process).
• Osteoporosis is usually caused by accelerated resorption of
bone.
Causes:
• Endocrine disorders.
• Drug induced osteoporosis (prolonged steroid administration).
• Dietary deficiencies (especially in proteins).
• Post menopausal osteoporosis.
Radiographic appearance
• Loss of mineral salts causes
osteoporotic bone to become
more lucent than normal.
• This may be difficult to detect,
because about 50% to 70% of
the bone density must be lost
before.
• So it is essential to use lowest
practical kVp.
Osteomalacia ‫ لين العظام‬and rickets ‫الكساح‬
•
In histology, osteoid is the unmineralized, organic portion of
the bone matrix that forms prior to the maturation of bone
tissue. Osteoblasts begin the process of forming bone tissue
by secreting the osteoid as several specific proteins. When the
osteoid becomes mineralized, it and the adjacent bone
cells have developed into new bone tissue.
• When there is insufficient nutrient minerals or osteoblast
dysfunction, the osteoid does not mineralize properly, and it
accumulates. The resultant disorder is termed rickets in
children and osteomalacia in adults.
Normal
Abnormal
Causes:
• Dietary deficiencies of vitamin D, or lack of exposure to sunlight.
• Malabsorption causing impaired absorption of vitamin D and
calcium from the gut.
Hyperparathyroidism
• Excess parathyroid hormone
secretion mobilizes calcium
from the bones resulting in
decrease in bone density.
• Causes:
Hyperparathyroidism may be:
• Primary, from hyperplasia or
tumor of the parathyroid
glands.
• Secondary to chronic renal
failure.
• The signs of
hyperparathyroidism
• A generalized loss of bone
density, with loss of different
ion between cortex and
medulla.
• Bone resorption (Fig.3a)
• Brown tumors (Fig.3b)
• Vascular calcification(Fig.4)
• Soft tissue calcification(Fig.5)
(Fig 3 a)
(Fig 4)
(Fig 3 b)
(Fig 5)