Chapter 7 Skeletal Tissue

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Chapter 7 Skeletal Tissue
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Types of Bone
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Bones

• Long Bone
• Short Bone
• Flat Bone
• Irregular Bone

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Long Bone

• Identified by extended longitudinal axes and
  uniquely shaped articular end
• Femur and humorous are examples

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Parts of Long Bone

• Diaphysis Main shaft or portion. Hollow.
  Composed of compact bone
• Epiphysis End of long bone. Gives stability to
  joints. Composed of spongy bone
• Articular cartilage Hyaline cartilage that
  covers epiphysis

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Parts of Long Bone

• Periosteum White fibrous membrane that covers
  bone except at joint surfaces
• Medullary (marrow) cavity Tube like hollow space
  in the diaphysis of long bones. Filled with fat
  rich connective tissue called yellow marrow
• Endosteum Thin epithelial membrane that line
  medullary cavity

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Short Bone

• Usually described as cube or box shape
• Includes carpals (wrist) and tarsals (ankles)

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Flat Bones

• Generally broad and thin
• Flattened and often curved surface
• Include some skull bones, scapula (shoulder
  blade), ribs and sternum (breast bone)

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Irregular Bones

• Clustered in groups
• Have variety of sizes and shape
• Include vertical bone that forms spine and some
  facial bones
• Bones that appear singly instead of in groups are
  called sesamoid
• Kneecap or patella

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Bone Tissue
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Composition of Bone

• Osseous tissue, connective tissue
• Extracellular components are hard and calcified
• Matrix is subdivided into two chemical
  components Inorganic salts (2/3) and organic
  matrix (1/3)

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Inorganic Salts

• Hardness of bone result from deposits of chemical
  crystals of calcium and phosphate called
  hydroxyapatite (85 of inorganic matrix)
• 10 of calcium carbonate and other minerals.
  (magnesium, sodium, sulfate and fluoride)
• Harmful elements also mix with bone matrix.
  (radioactive elements such as radium,
  stronium-90, uranium and plutonium)

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Organic matrix

• Composite of collagenous and mixture of protein
  and polysaccharides called ground substance
• Ground substance provide support and adhesion
  between cellular and fibrous elements
• Chondroitin Sulfate helps cartilage remain
  compressible and elastic
• Glucosamine is an amino sugar important in
  cartilage formation, maintenance and repair

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Chondroitin Sulfate and Glucosamine

• dietary supplements that facilitate healing and
  reduce pain of osteoarthritis
• Naturally found in body and are important
  constitutes of ground substance
• Commercially, Chondroitin Sulfate is harvested
  from sharks and cattle tracheas
• Glucosamine harvested from shells of shrimp,
  lobster and crab

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Bone Marrow

• Specialized type of soft, diffuse connective
  tissue called myeloid tissue
• Site for production of blood cells
• Found in medullary cavity of long bones
• Two types Red and Yellow

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Red Bone Marrow

• Production of blood cells
• In an infant or child nearly all bones contain
  red marrow
• In adult in ribs, bodies of vertebrae, ends of
  humerus, pelvis, and femur.

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Yellow Bone Marrow

• As aging continues red bone marrow is replaced by
  yellow bone marrow
• Marrow cells have become saturated with fat
• Inactive in blood cell production
• Advancing age become almost rust-colored, less
  fatty and gelatinous
• During times of decreased blood supply yellow
  marrow may convert back to red

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A small amount of bone marrow is removed during a
bone marrow aspiration. The procedure is
uncomfortable, but can be tolerated by both
children and adults. The marrow can be studied to
determine the cause of anemia, the presence of
leukemia or other malignancy, or the presence of
some "storage diseases" in which abnormal
metabolic products are stored in certain bone
marrow cells.
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Bone Marrow Transplant

• While you are awake and pain-free (using local
  anesthesia), bone marrow is removed from the top
  of the hip bone (iliac crest). The bone marrow is
  filtered, treated, and transplanted immediately.
  Other times it's frozen and stored for later use.

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Bone Marrow Transport

• The bone marrow is then transfused through a vein
  (IV line). It naturally transports itself back
  into the intended bone cavities, where it grows
  quickly to replace the old bone marrow.

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Regulation of Blood Calcium Levels
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Blood Calcium Levels

• Skeletal system serves as storehouse for about
  98 of body calcium reserves
• Calcium moves into and out of blood during
  continuous remodeling of bone
• Osteoblast deposit bone and remove calcium from
  blood
• osteoclast breakdown and reabsorb bone, releasing
  calcium back into the blood

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Blood Calcium Levels

• Needed for normal blood clotting
• Transmission of nerve impulses
• Maintenance of skeletal and cardiac muscle
  contraction
• Involve secretion of two hormones parathyroid
  hormone and calcitonin

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Parathyroid Hormone

• Most critical factor in blood calcium homeostasis
• When blood calcium levels are lower than set
  point in parathyroid gland, osteoclasts are
  initiated to start break down of bone matrix
• If levels are high osteoclasts activity is
  surpressed
• Also increases renal absorption of calcium from
  urine
• Stimulates vitamin D synthesis

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Calcitonin

• Produced in response to high calcium levels
• Stimulates bone deposition by osteoblasts
• Inhibits osteoclast activity
• Nasal spray containing calcitonin (Miacalcin) can
  be used to treat post menopausal osteoporosis

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Development of Bone
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Development of Bone

• Before birth bones consist of cartilage and
  fibrous structures
• Replaced with calcified bone matrix
• Bone formation is on going process known as
  osteogenesis

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Intramembranous Ossification

• Formation of bone on, or in, fibrous connective
  tissue
• Process used to make flat bones such as the
  mandible and flat bones of the skull.
• Clusters of osteoblasts are called centers of
  ossification
• They secrete matrix material and collagenous
  fibrils

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Intramembranous Ossification

• Calcification of bone continues
• Trabeculae appear to form spongy bone
• Uses appositional growth

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Endochondral Ossification

• Bones are formed from cartilage models
• Cartilage model develops periosteum that enlarges
  and produces a ring or collar

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Endochondral Ossification

• Bone is deposited by osteoblast and cartilage
  begins to calcify

• Primary ossification center
• Blood vessels enter

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Endochondral Ossification

• Secondary ossifiaction center
• Bone growth proceeds toward diaphysis

• Epiphyseal plate allow bone to increase in length
• Ossification near diaphysis follows

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Repair of Bone Fracture
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http//www.youtube.com/watch?vqVougiCEgH8 Bone
repair
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Bone Repair of Fracture
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Fracture takes place, damaging bone and blood
vessels
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• Pooling of blood result in blood clot (fracture
  hematoma)
• Develops fibrin mesh and transforms into mass of
  granulation tissue
• Contains inflammatory cells, fibroblast, bone and
  cartilage forming cells, and new capillaries

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Bone Repair of Fracture
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• Islands of cartilaginous tissue (procallus) form
• Helps anchor ends of fractured bone more firmly
• Osteoblasts form bony callus collars broken ends

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• Repaired bone

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Mechanism of Disease
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Osteosarcoma

• Most common malignant bone tumor
• Often fatal
• Males 10-25 yrs
• Common site tibia humerus and femur
• 10 metastasize to lung
• Surgery, followed by chemo

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Chondrosarcoma

• Malignant tumor of hyaline cartilage
• Arises from chondroblasts
• Occurs more frequently in middle age
• Common sites Humerus, femur, scapula, spine,
  pelvis and ribs
• Large excission or amputation
• Chemo has not proven effective

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Osteoporosis
http//www.youtube.com/watch?vvcsPjThU-5Qfeature
fvw
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Rickets and Osteomalacia

• caused by insufficient levels of vitamin D in the
  body
• rickets is the name used when it occurs in
  children whereas osteomalacia is the term used
  for adults.
• Symptoms Bone pain, muscle weakness and possible
  joint inflammation and pain
• Treatment daily supplements of vitamin D and
  calcium or single injection vitamin D, in the
  form of calciferol (vitamin D2).

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Osteomyelitis

• Bacterial bone infection
• Most common is from staph
• bacteria can settle on a small section of bone,
  and multiply to cause infection.
• Treatment include antibiotics and or surgery