Anatomy Physiology The Skeletal System Skeletal System Functions

Anatomy & Physiology The Skeletal System

Skeletal System Functions § Support § Protection § Movement § Mineral Storage & Homeostasis § Site of Blood Cell Production § Storage of Energy

Types Of Bones § Bones can be classified on basis of shape. § Long Bones are longer than wide. (femur) § Short Bones are somewhat cubed shaped and nearly equal in length and width. (carpals) § Flat Bones are thin and comprised of two plates surrounding spongy bone. (cranial) § Irregular Bones have complex shapes. (vertebrae)

Types of Bones

Parts of Long Bones § Diaphysis – shaft or long cylinder of the bone. § Epiphysis – the ends of the bone. § Metaphysis – where diaphysis and epiphysis meet. § Articular cartilage – hyaline cartilage on the ends of the bone forming the joint.

Parts of Long Bone § Periosteum – tough outer covering on bone made of dense fibrous connective tissue. § Medullary Cavity – hollow cavity in the diaphysis which contains yellow bone marrow. § Endosteum – the lining of the medullary cavity contain osteoprogenic and osteoblasts.

Parts of a long bone

Histology of Bone § Several connective tissues make up bone. They include cartilage, dense connective, and osseous. § Bone contains large amounts of matrix, made of calcium salts and collagen fibers. The salts crystallize within a network of fibers. § Cells found within bone include osteogenic, osteoblasts, osteocytes, and osteoclasts.

Histology of Bone § Bone is not totally solid. It contains a solid region (compact bone) and a porous region (spongy bone). § The structural unit of compact bone is the Osteon or Haversian System. It contains concentric rings or layers called lamellae, a central canal, and collections of osteocytes called lacunae. § Spongy bone has network called trabeculla.

Ossification of Bone § Bone formation or Ossification begins with osteogenic cells. These cells are formed from mesenchymal connective tissue. § The osteogenic cells give rise to chondroblasts which produce cartilage and osteoblasts to form bone. § Bone formation takes place in the embryo either on a membrane or within a cartilage model.

Ossification of Bone § Intramembranous – the cranial bones and clavicles are formed by this type of bone formation. § Endochondral – all other bones are formed this way.

Endochondral Ossification

Bone Growth and Maintenance § Cartilage between the epiphysis and diaphysis the epiphyseal plate permits growth in length through adulthood. § Bone growth is under the control of Human Growth Hormone released from the pituitary gland. § Vitamin D is needed for absorption of Calcium into bone, from the GI Tract. § Ossification is complete by age 25.

Bone and Mineral Homeostasis § Bones store and release calcium and phosphate. § This process is controlled by the hormones: Calcitonin (CT), Parathyroid hormone (PTH), and Vitamin D. § PTH activates osteoclasts and decreases bone density. (reabsorption). § CT increases osteoblasts and increases bone density.

Exercise and Bone § When placed under mechanical stress bone becomes stronger. § The mechanical stresses come from muscles pulling on the bone and the force of gravity.

Aging and Bone § Aging of bone results from calcium loss from the body. § It begins after age 30 in females and accelerates at ages 4045 as estrogen levels decrease. § In males calcium loss does not occur until age 60.

Male vs. Female § Male bones are heavier and stronger than female bones. Joint surfaces are also larger. § Muscles attachments areas are larger in males. Due to larger muscle size. § The pelvic opening in females is larger to accommodate child birth. Hips are also angles wider in females.