W10. ch.19.BONES&JOINTS Flashcards
How many bones?
- more than 200, short and long
- made of osteocytes and extracellular matrix that is impregnate with calcium phosphate salts
Most NB functions of the bones
- mechanical support for the muscles
- protection of the internal organs (ribs)
- support of hemapoesis
- storage of calcium and phosphe salts
Normal structure and shape of bones: influences
- interaction with the muscles
- hormonal regulation of phosphate and calcium
- also bone formation and bone resorption
Osteoblasts and Osteoclasts
- osteoblasts form new bone
- osteoclasts remove and remodel old bone under the influence of hormones (parathyroid, vit c &D), and various other substances such as interleukins and prostaglandins
- calcium and phosphate released from the bone enter circualtion and are in balance with ionized calcium and phosphate in the serum. Balance is tightly regulated by PTH and vit D.
What is a joint?
- junction between 2 or more bones. Support, structural firmness, and movement.
- 2 types: synovial and joints that allow for limited or no movement (synathroses)
synovial joint is enclosed in a connective tissue capsuke composed of ligaments. inside lined with synovial cells which secrete fluid
Developmental Disorders of the Bone
- Achondroplasia:AD, causes dwarfism
- Osteogenesis imperfecta: several diseases characterized by deffective bone formation
Osteomyelitis
- infection of the bone. May present as acute infection that progresses to osteomyelitis
- most common causes are pyogenic cocci, most staphylococcus aureus
- poorly cleansed wounds infected by trauma or GSW
- sickle cell predisposed to infections caused by salmonella
Asceptic Bone Necrosis
- sudden onset of ischemia caused by desruption of blood flow, causes bone infarct
- infarcts in growing bones occur mostly in children and adolescents
Pathogenesis of Staphylococcal Osteomyelitis:
Where does it occur most often?
In adults, what does it occur as?
How is it treated?
-occurs in metaphysis of bone, typically occurs in growing children. Affects boys more than girls - trauma? Metaphysis is the most vascular portion of the bonehese vessels, known as nutrient arteries, penetrate the cortical bone and deliver blood to the zone of the epiphysial growth platethis “direct access” facilitates entry of bacteria into the bone during bacteremia
In adults, osteomyelitis occuts as a complication of bone fracture or bone surgery, or spread of infection to soft tissues
-suppurative must be tx. with large dose abx. Surgury may be required depending on draninge of pus and destruction of bone.
Osteomyelitis image
Circulatory Disturbances in bone: Aseptic Bone Necrosis
what is it
most often in which age group
which bones are more at risk
in elderly, which site?
causes?
- sudden onset of ischemia cause by interruption of blood flow - causes bone infarcts
- Asceptic infarcts of growing bones are diseases that most often occur in children - occur in ossification centers of various growing bones. Can also occur in the elderly at a high rate.
- Certain growing bones are more at risk: carpal bones due to limited blood supply
- In elderly: head of the femur is most nb site - fumur fractures and osteoporosis are often incapacitating
- cause of most infarcts in unknown, but some may be related to trauma, emboli, radiation, or drugs. Well documented causes include air emboli in decompression disease, and microthrombi and sludges in sickle cell.
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Metabolic disorders of bones: Osteoporosis
- multifactorial disease characterized by absolute reduction of total bone mass
- most prevalent bone disease worldwide
- 1/3 of women older than 65 have some minor fracture related to osteoporosis
- in those older than 85, 1/3 of all north american women and 1 in 6 men are temp or perm confined to bed b/c of hip fractures
- hip fractures are the most incapacitating complication of osteoporosis
Primary and Secondary Osteoporosis
Primary: No definitive clues of etiology. Accounts for most cases. Is disease of elderly persons, accounts for more women than men
Secondary: occurs at any age, related to identifiable causes, including
- hormonal disturbances: excess (hyperadrenocorticism), or deficiency (hypogonad, diabetes) of hormones
- Dietary insufficiency of intake (calcium, vit C), or malabsorption of nutrients (intestinal or liver disease)
- Immobilization
- Drugs: anticonvulsants or heparin
- Tumors: hormones of endocrine glands, or direct damage from tumors such as breast cancer
- osteoporosis often has multiple causes: age, smoking, alcohol. Cirrhosis of liver affects vitamin D metabolism. Post menopausal - lack of estrogen, nutritional deficiencies r/t alcohol
Causes of Osteoporosis: Image
Pathogenesis of Osteoporosis:
Characterized by
- characterized by simultaneous loss of bone mass and minerals
- pathogenesis of primary osteoporosis remains unknown, but several factors bone loss have been id’d
- initial bone mass
- diet and lifestyle
- hormones
- age related changes in metabolism
- certain prescribed medications
Osteoporosis- age
- normal bones undergo remodeling throughout the entire lifespan
- up to the age of 30, bone formation by osteoblasts exceeds bone resorption by osteoclasts
- after 30, resportion exceeds formation, resulting in a net bone loss of 0.5% each year. After menopause, this is accelerated for a loss of betweem 1-3% each year. May be related to estrogen. Estrogen therapy can prevent or slow bone loss
Osteoporosis: develops more often in
- gracile white woman of small frame, who have smaller initial bone mass than larger frames
- denser bones in men, blacks, and athletes
Osteoporosis and nutrition:
Which nutrients are most NB?
Under which conditions may this be impaired?
Calcium and vitamin D are important, and are added to meet requirements of north american diet.
-If absorption of calcium and vit D are impaired (intestinal or liver disease), then deficiencies develop
Pathology of Osteoporosis: type 1
Describe osteoporotic bones
What part of the bone is lost?
Which bones predominate?
What is the major complication?
- Osteoporotic bones are thin and brittle, prone to fracture
- loss involves both cortical and spongy bone
- In type 1, which occurs in post-menopausal women, trabecular bone loss predominates, occuring most prominently in the vertebrae and distal radius.
Major complication is crush fracture of vertebral bodies and of the distal end of the radius.
Pathology of osteoporosis: Type 2
Characterized by:
Most serious complication:
- In type 2, osteoporosis of old age, characterized by proportunate loss of cortical and trabecular bone of the long bones.
- Most serious fractures of type 2 are the head of the femur
- none of the bone is spared, nor is trauma required. A persons body weight alone can cause the fracture.
- vertebrae are common sites of microfractures, which produce wedge shaped deformity. Multiple make elderly look smaller and bent forward
- these anatomical changes compromise function of internal organs
Clinical Features of osteoporosis
which bone fractures are most incapacitating?
Are there biochemical markers?
- symptoms are extremely variable and non-specific
- vertebral fractures cause back pain and kyphosis
- extensive osteoporosis may reduce a persons height up to 15cm or 10%
- fractures of long bones may be incapacitating
- over 1 million hip fractures per year, 25% never heal
- despite loss of bone, people show no biochemical markers. Serum calcium, phophate, and alkaline phosphatase are normal
Dianosis of osteoporosis
- best diagnosed by radiographic studies
- xray not very sensitive, and detect signs only after 30-50% reduction. Therefore prevention is essential.
- Bone mineral density measured by dexa scan, can provide more precise estimate of bone loss
Osteomalacia:
What is it?
What causes it?
What is it called in growing bones?
- softening of bones with deformities related to inadequare mineralization of organic bone matrix
- Changes are caused by disturbances vitamin D or phosphate metabolism
- Osteomalacia of growing bones in children is called rickets
Etiology of Osteomalacia
- r/t which nutrients?
- Why might they be deficient?
- vitamin D and phosphate are essential nutrients
- Vit D derived from the diet but also synthesized in skin under uv light
Deficiency of vid D: inadequate intake (many north american foods have fortified with vit D), inadequate exposure to sunlight, abnormal intestinal absorption (diseases of small intesting when vit D not absorbed, or billiary /pancreatic diseases with fat malabsorption
-osteomalacia may also be caused by hypophosphatemia r/t abnormal absorption or excessive loss of phosphates. Malabsorption from intestinal diseases or resection. PTH also prevents tubular resorption of phosphates, thus phosphate wasting in urine during hyperparathyroid
Pathogenesis of Osteomalacia:
Where is vitamin D activated?
What is the 3 functions of the main form?
- Activation of vitamin D occurs in the liver and the kidneys
- several active metabolites are formed, the most important is hydroxylated 1,25 vitamin D. This form has 3 main functions
- stimulation of intestinal absorption of calcium and phosphorus
- Action on the bone, includes deposition of calcium into the osteoid and mobilization of calcium from calcified bone. Vitamin D is essential for mineralization of the osteoid
- stimulation of the PTH dependent resorption of calcium in the kidney
Pathology of Osteomalacia
Deficiency in ___ results in ____
Typical complication
osteomalacia is characterized by
- Vitamin D deficiency results in osteopenia, which is visible as increased bone lucency on xray. CLinically, bones are soft and pliable.
- fractures and deformity are typical complications
- rickets (osteomalacia in children) affects bone development
Osteomalacia is characterized by an excess of osteoid around the calcified core of the trabeculae of spongy bone and on the endocavitary side of compact bones. Fractures are common and heal by exuberant osteoid formation. Softening of the bones may also produce deformities.
These are common in children affected by rickets but are rare in adults.
Pathology of Rickets
- endochondral ossification in the growth plate is most severely disturbed
- this results in growth retardation, bone deformities, and fracture of long bones
- bow legs result from the inibility of the soft leg bones to carry the weight of the body
- widened junction between rib bone and cartilage- the costochondral junction- appears nodulat and can be palpated as beads on the thorax (rachitic rosary)
- softenin of cranial bones is called craniotabs
- dentition is delayed and the teeth may be speckled by as a result of incomplete miniralization
Clinical Features of Osteomalacia in Adults
- often asymptomatic, or cause non-specific bone pain
- muscle weakness is common
- skeletal deformities develop slowly and are not prominent
Pagets Disease: image
Types of fractures: image
Malignant Bone Tumors:
occus most often
image of most important features
- occur most often in males
- bone tumors are classified by the peak age incidence and anatomical location
Most Common sites of bone tumors: image
Pathologic Changes in Osteoarthritis:image
Symptoms and Pathology in Osteoarthritis: Table
