Anatomy: Bone Tissue

Anatomy: Bone Tissue

Cells of Bone tissue

Osteogenic Cell 🡪 Osteoblast 🡪 Osteocyte

Supportive Connective Tissue

Extracellular Matrix

  • 25% Water
  • 25% Protein or organic matrix
  1. 95% Collagen fibers
  2. 5% Chondroitin sulfate
  • 50% crystalized mineral salts
  1. Hydroxyapatite (calcium phosphate)
  2. Other substances (lead, gold, strontium, plutonium, etc.)

Types of Bone (2)

  • Compact Bone
  • Spongy Bone

Compact Bone

  • Arranged in units called osteons or haversian systems.
  • Osteons contain blood vessels, lymphatic vessels, nerves.
  • What surrounds the Osteon canal: concentric rings of osteocytes along with the calcified matrix.
  • Osterons are aligned in the same direction along lines of stress.
  1. These lines can slowly change as the stresses on the bone changes

Histology of Compact Bone

  • Osteon: concentric rings (lamellae) of calcified matrix surrounding a vertically oriented blood vessel.
  • Osteocytes are found in spaces called lacunae
  • Osteocytes communicate thru canaliculi fixed with extracellular fluid that connect one cell to the next cell.
  • Interstitial lamellae represent older osteons that have been partially removed during tissue remodeling.

The Trabeculae of spongy bone

  • Latticework of thin plates of bone called trabeculae oriented along lines of stress.
  • Spaces in between the trabeculae are filled with red marrow where blood cells develop.
  • Spongy bone is found in ends of long bones and inside flat bones such as the hipbones, sternum, sides of skull, and ribs.

Spongy Bone

  • Also known as “cancellous bone”.
  • Does not contain osteons but consists of trabeculae surrounding many red marrow filled spaces.
  • Forms most of the structure of short, flat, and irregular bones, and the epiphyses of long bones.
  • Spongy bone tissue are light and supports/protects the red bone marrow.

Bone Formation

  • All embryonic connective tissue begins as mesenchyme.
  • Also known as “Osteogenesis” or “ossification”.
  • Begins when mesenchymal cells provide the template for subsequent ossification.
  • Two types of Ossification:
  1. Intramembranous Ossification: formation of bone directly from or within fibrous connective tissue membranes.
  2. Endochondrial ossification: formation of bone from hyaline cartilage models.

Intramembranous Ossication (in depth)

  • Also called “dermal ossification” because it normally occurs in the deeper layers of connective tissue of the dermis of the skin.
  • Roofing bones of the skull:
  1. Frontal bones
  2. Parietal bones
  3. Occipital bone
  4. Temporal bones
  • Mandible
  • Clavicle

Endochondral ossification

  • Developing bones are deposited as a hyaline cartilage model and then this cartilage is replaced by bone tissue
  • All bones except roofing bones in the skull, mandible, and clavicle.

Growth at Epiphyseal plates

  • Zones of resting cartilage
  1. Anchors growth plate to bone
  • Zone of proliferating cartilage
  1. Rapid cell division (stacked coins)
  • Zone of hypertrophic cartilage
  1. Cells enlarged and remail in columns
  • Zone of calcified cartilage
  1. Thin zone, cells mostly dead since matrix calcified.

Bone Fractures

  • Closed/open
  • Partial/complete
  • Displaced/nondisplaced
  • Simple/compound

Subluxation: an incomplete or partial dislocation of a joint or organ.

Luxation: a complete dislocation of a joint or organ

Steps in Facture Repair

  1. Formation of a fracture hematoma
  2. Fibrocartilaginous callus formation
  3. Bony callus formation
  4. Bone remodeling

Fibrous Joints: Sutures

  • Allow for brain growth
  • Allow for passage through the birth canal

Symphyses

  • Fibrocartilage unites bone

Bone Disorders

Arthritis:

  • DJD: Degenerative joint disease

Inflammatory Joint Disease

  • Rheumatoid Arthritis
  1. May be caused by transient infection that results in autoimmune attacks against collagen in the bones at joints.
  2. Swain Neck deformity.

Infectious Arthitis

  • Lyme Disease
  1. Bull’s Eye rash
  • Gonorrhea
  1. Sometimes no symptoms

Scoliosis: Abnormal curve of the spine.

Acromegaly

  • Body produces too much Growth Hormone
  • Only in Adults
  • Tissues grow larger than normal
  • Excessive growth can cause serious disease and even premature death.

Gout

  • Results from overload of Uric Acid in the body
  • Leads to the formation of urate crystals that deposit in the joints
  • Causes recurring attacks of joint inflammation (arthritis)
  • May cause joint destruction, decreased kidney function, and kidney stones.

Spina Bifida

  • Birth defect
  • Incomplete development of the spinal cord or its coverings
  • Prevent with folic acid
  • Spina bifida means “split” or “open” spine
  • Is usually detected before a baby is born and treated right away.

Myeloma: Cancer in which abnormal cells collect in the bone marrow and form tumors.

  • Starts in the bone marrow where blood cells are
  • Bone marrow starts to overproduce abnormal white blood cells
  • Leukemia cells don’t do the work of normal WBC’s and they don’t stop growing when they should.