Ossecous Tissue and Skeletal Structure
The Skeletal system consists of bones and their associated connective tissues, including cartilage, tendon and ligaments.
I. Function of the Skeletal System
1) Bone- The most rigid component of skeletal system
a) Support- serves as a framework; Maintains body’s shape
b) Protection- of critical internal organs, brain, heart and lungs
c) Lever System- for muscles to produce body movements
d) Mineral storage- e.g. Calcium and Phosphorous
e) Blood Cell formation- in bone marrow of many bones, mainly flat ones 2) Cartilage- Some what rigid but more flexible
a) Model for bone growth- in embryo and fetus
b) Smooth joint surfaces- Provides a smooth cushion between adjacent bones
c) Support- firm yet flexible, e.g. nose, ears, rib cage, trachea 3) Tendons and ligaments form attachments- Strong bands of fibrous connective tissue. Tendons attaches muscles to bones, ligaments attaches bone to bone.
II. Connective Tissue
-Bone, Cartilage, Tendons, and Ligaments are connective tissues 1) Extracellular Matrix for Cartilage
a) Collagen- Tough Ropelike Protein
b) Proteoglycans- Polysaccharides (pine needle) attached to core protein (tree); Attracts and retains large amounts of water between the polysaccharide needles. Acts as shock absorber.
2) Extracellular Matrix for Bone
b) Hydroxyapatite- Calcium phosphate.
3) Extracellular Matrix- Tendons and Ligaments
Large amounts of collagen fibers, make them tough like ropes and cable
III. General Features of Bone
a)Long bones- e.g. limbs
b)Short bones- e.g. bones of wrist and ankle
c)Flat bones- e.g. ribs, scapula, pelvis
d)Irregular bones- e.g. vertebrae and facial bones e) Sesamoid- develop inside tendons, located near joints of knees, hands and feet; shaped some what like sesame seed e.g. patella bone f) Sutural- e.g. in skull
2)Long bone anatomy
-Epiphysis- the ends- covered by Articular Cartilage - Metaphysis
-Epiphyseal plate-Growth plate. Cartilage plate between each Diaphysis and epiphysis. When bone growth stops turns to bone, and then is called Epiphyseal line. -Modullary Cavity- Contains Yellow Marrow (Fat) or Red Marrow (blood-forming cells) - Articular Cartilage-
3)Two types of bones
1)Compact Bone- Diaphysis of long bones and the thinner surface of all the other bones 2)Cancellous Bone- or Spongy bone is located in the epiphyses of long bones and it forms the center of all other bones. It consists of trabeculae (beams) which add strength to the bones with out adding extra weight. Osseous tissue
Supporting tissue with a solid matrix
2. Crystals of hydroxyapatite
Minerals deposited in lamellae
Periosteum (covers the bone)- membrane with a fibrous outer and cellular inner layer Endosteum –incomplete cellular layer that lines the marrow cavity Cells in bone:
Osteocytes = mature bone cells.
7. In lacunae
8. Connected by canaliculi
9. Two major functions of osteocytes:
1) they maintain and monitor the protein and mineral content of matrix 2) They can participate in the repair of the damaged bone Osteoblasts- immature bone cell that secretes organic components of matrix
This process is called Osteogenesis
Osteoclasts are giant cells with 50 nuclei that secretes acids and enzymes to dissolve bone matrix 12. Osteolysis
Osteoprogenitor cells- stem cells that differentiate into osteoblasts
Compact bone and spongy bone
Basic unit of compact bone is an osteon or Haversian system
15. Osteocytes arranged around a central canal or Harversian canal 16. Perforating canals extend between adjacent osteons
17. Compact bone located where stresses are limited in...