Chapter 44 Disorders of the Skeletal System: Metabolic and Rheumatic Disorders

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Chapter 44

Disorders of the Skeletal System: Metabolic and

Rheumatic Disorders

Chapter 44

Disorders of the Skeletal System: Metabolic and

Rheumatic Disorders


Normal Bone RemodelingNormal Bone Remodeling

• Osteoblasts are “bone building” cells

• They control bone remodeling by:

– Laying down new bone

– Secreting a compound (RANK ligand) that controls the osteoclasts, the “bone breaking” cells

• Normally, bone formation and breakdown are balanced to:

– Replace damaged bone

– Maintain the amount and density of bone


Bone GrowthBone Growth

• Bone cells and bone marrow cells produce OPG

– It blocks the action of RANK ligand

– The osteoclasts are not told to function

– Bone breakdown decreases

– Bones grow


Question Question

Tell whether the following statement is true or false.

When osteoblasts work harder than osteoclasts, bones grow.


Answer Answer

True

Osteoblasts build bone tissue; when they are more active than osteoclasts, bone grows. When osteoclasts work harder than osteoblasts, more bone is broken down.


DiscussionDiscussion

How is bone remodeling affected by the following?

• Vitamin D?

• Mechanical stress?

• Calcitonin?

• Vitamin C?


• Osteopenia

– Decreased bone

• Osteoporosis

– Decreased bone mass

– Decreased cancellous (spongy) bone strength

Osteopenia and OsteoporosisOsteopenia and Osteoporosis


DiscussionDiscussion

Why are each of these people prone to osteoporosis?

• A postmenopausal woman

• A 70-year-old man

• A hyperthyroid alcoholic

• An Olympic figure skater who takes steroids to reduce joint inflammation

• A man with a lung tumor that secretes PTH


Discussion (cont.)Discussion (cont.)

• Who would be most helped by the following?

• Exercise

• Increased Ca2+ and vitamin D in the diet

• Estrogen receptor stimulators

• Inhibitors of bone resorption


OsteomalaciaOsteomalacia

• Bone is not mineralized properly; it is not rigid

• It is caused by:

– Insufficient calcium absorption

– Insufficient phosphate

• It results in:

– Bone pain and tenderness

– Fractures

– Deformities


RicketsRickets

• Vitamin D deficiency

• Inadequate calcium absorption from diet


Paget DiseasePaget Disease

• Regions of excessive bone turnover

• New bone is disorganized

• Deformation and fracture common


Question Question

Which bone disorder is characterized by “soft” bones?

a. Osteopenia

b. Osteomyelitis

c. Rickets

d. Paget disease


Answer Answer

c. Rickets

Calcium need vitamin D in order to be absorbed. In the case of vitamin D deficiency (rickets), calcium cannot be absorbed, and bones become soft.


Rheumatoid ArthritisRheumatoid Arthritis

• Autoimmune disorder

• Antibodies against IgG fragments

• Cause inflammation in the joint

• Abnormal healing responses lay down granulation tissue (pannus)


Treatment of Rheumatoid ArthritisTreatment of Rheumatoid Arthritis

• NSAIDs

• Corticosteroids

• Leflunomide

• Influximab


Systemic Lupus Erythematosus (SLE)Systemic Lupus Erythematosus (SLE)

• Autoantibodies include:

– Antinuclear antibodies (ANA)

– Antibodies against RBCs

– Antibodies against platelets

– Antibodies against coagulation factors


SLE Can Damage Any TissueSLE Can Damage Any Tissue

• Arthralgia

• Skin lesions (butterfly rash)

• Glomerulonephritis

• Pleuritis

• Pericarditis

• Atherosclerosis

• CNS inflammations


Question Question

SLE produces antibodies against all but which of the following?

a. RBCs

b. WBCs

c. Platelets

d. Coagulation factors


Answer Answer

b. WBCs

SLE is an autoimmune disease that results in the production of the following antibodies: antinuclear antibodies, and antibodies against RBCs, platelets, and coagulation factors. WBCs are not affected.


• Collagen deposits in skin and internal organs

Systemic Sclerosis (Scleroderma)Systemic Sclerosis (Scleroderma)

SpondyloarthropathiesSpondyloarthropathies

• Inflammation at the insertions of tendons and ligaments


Reactive ArthropathiesReactive Arthropathies

• Sterile joint inflammations caused by previous infection

• The joints are not infected at the time of inflammation

• Can follow infection with many agents including:

– Chlamydia

– Pseudomonas

– Streptococcus

– HIV


Osteoarthritis SyndromeOsteoarthritis Syndrome

• Degenerative joint disease

• Inflammation of the joints often secondary to physical damage

• Damaged joint cartilage tries to heal itself

– Creating osteophytes or spurs

• Cartilage contains more water, less collagen

– Cartilage becomes weak, rough, eroded

– No longer protects the surface of the bone


Gout SyndromeGout Syndrome

• Increased serum uric acid

• Crystals precipitate in the joint

• Inflammation results

• Tophi are deposits containing monosodium urate crystals

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Chapter 44 Disorders of the Skeletal System: Metabolic and Rheumatic Disorders

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