Untitled Flashcard Set

What are the Functions of the Skeletal System?

🌸Support

  • Bearing the weight of the body

🌸Protection

  • Encasing essential organs

  • Ex: ribcage protects the heart and lungs from injury

🌸Movement

  • Joints provide movement for bones

🌸Storage

  • Storage of minerals to be released into the bloodstream

  • Storage of fat in yellow bone marrow

🌸Manufacturing

  • Production of red & white blood cells from red bone marrow

  • Called hemapotoiesis


Types of Bones

  • Bones are a sold matric of living cells and fibers surrounded by calcium deposits

  • Bones are classfied by their shape:


  1. Flat Bones

  2. Irregular Bones

  3. Long Bones

  4. Short Bones

  5. Sesamoid Bones


Long Bones

  • Long bones have 2 bacis regions:

    • Diaphysis: Shaft, long part of bond

    • Epiphyses: End of bone

  • Between these layers is a thin layer of internal cartilage called the epiphyseal plate (growth plate)

  • The ends of the epiphyses are covered with an external layer of cartilage called articular cartilage which provides smooth movement of joints and cushion from shock

  • In the diaphysis of the long bone, a hollow medullary cavity is found

  • Red bone marrow fills this cavity in young people. Age causes the red marrow to be replaced with fatty yellow bone marrow.

  • It is within the bone marrow that new blood cells are produced (called hematopoiesis)


Spongy & Compact Bone

  • The outer layer of the bone is made of tough connective tissue called periosteum. It is the location of muscle attatchment and bone repair.

  • Beneath the periosteum is a thick layer of compact bone.

  • At the ends of long bones, the spongy bone layer is beneath the compact bone.


How do Spingy and Compact Bone Differ?

Spongy Bone

  • Spongy bone is a lattice of trabeculae (“little beams“) that are found along lines of stress for perfect resistance from compression

  • Between the trabeculae are spaces filled with marrow or blood vessels

Compact Bone

  • Compact bone is arranged in cylinders called osteons

  • Osteons are arranged in concentric cricles called lamellae

  • These lamellae surround a central (or Harversian) canal that contains blood vessels and nerves

  • The central canals are connected by perforating (Volkmann’s) canals running perpendiculary




What are the Types and Functions of Speacialized Bone Cells?

  • Osteocytes = mature bone cells make up the majority of the bone structure

  • Osteocytes are connected with tentacle-like canaliculi

    • Canaliculu connect all bone cells, allowing them to receive nutrients and remove wastes

  • Osteoclasts & osteoblasts line the Haversian canals canals and the surface of the compact & spongy bone

Osteoclasts break down bone

Osteoblasts produce new bone





How is Bone Formed?

  • An embryo’s skeleton is made of cartilage

  • Near the third month of embryo development, osteoblasts begin to secrete mineral deposits that replace the cartilage. The osteoblasts then mature into osteocytes.

  • This process of incorporating calcium & minerals into cartilage to become bone is known as ossification.

  • As a child grows, tall columns of chondrocytes (cartilage cells) at the epiphyseal plate divide and then deteriorate as the matrix around them calcifies. These cells are then known as osteoblasts, which form spongy bone.

  • Osteoclasts secrete acid to enlarge the medullary cavity, as the bone grows so that marrow is available for all cells.




What is the Composition of Bone?

Organic

  • 35% Osteoid (made of ground substance & collagen)

  • Provides the flexibility & tensile strength requiered to keep bones from constantly breaking

  • Lack of collagen causes “Brittle Bone Disease“

Inorganic

  • 65% Mineral Salts

  • Crystaline salts made of hydroxyapatites

    • Ca10(PO4)(OH)2

  • Provides bone strength & hardness

  • Lack of hydroxyapatite causes “Rickets“