SKELETAL SYSTEM

• The adult skeleton consists of 206 bones and numerous joints. Many bone disorders involve breaks in bones or abnormal bone formation.
• In the fetus, bones are composed of a soft, flexible tissue called cartilage.
• As the fetus develops, cartilage is replaced with bone tissue in a process called ossification, also known as bone formation.
• Ossification begins on the osteogenic cells. They are bone stem cells. These cells will divide and they will become Osteoblasts.
• Osteoblasts produce an enzyme that causes calcium and phosphorus in the area to combine into a hard substance called calcium phosphate.
• In the forming bone, osteoblasts develop into mature bone cells called osteocyte.
• As maturing osteoblasts are added to the bone, cells called osteoclasts digest older osteocytes
• Bones are classified into five (5) groups: Long Bones, Short Bones, Flat Bones, Sesamoid Bones , and Irregular Bones
• Long Bones - the strong bones of the arms and legs
• Short Bones - the irregularly shaped structures in the wrist, ankles, and toes
• Flat Bones - the broad bones found in the shoulder, skull, and ribs
• Sesamoid Bones - the very small bones found near joints
• Irregular Bones - those that do not fall nearly into the first four categories
• In children, the epiphysis contains cartilage, allowing the bone to grow longer
• In adults, this cartilage is ossified, forming the epiphyseal line.
• Each Epiphysis consists of three (3) layers of tissue: Articular Cartilage, Compact Bone , Spongy (Cancellous) Bone
• Articular Cartilage - thin layer of cartilage
• Compact Bone - thick layer of tissue
• Spongy (Cancellous) Bone - inner area of porous tissue
• Each Diaphysis consists of three (3) layers of tissue: Periosteum, Compact Bone , Medullary
• Periosteum - a sturdy outer membrane
• Compact Bone - main tissue in the diaphysis
• Medullary - inner area
• The Cranuim is the structure that sorrounds the brain, protecting it from injury.
• The vertebral column is consist of 26 bones called vertebrae seperated and cushioned by flat, round, shock - absorbing structure called vertebral disks.
• The cervical vertebrae, C1 - C7 are located in the neck area.
• The 12 thoracic vertebrae, T1 - T12 are located in the chest region.
• lumb/o = wrist - The 5 lumbar vertebrae, L1-L5 are located in the lower back region.
• sacr/o = lower back The sacrum is a single bone consisting of five fused vertebrae, is located in the "sacral" region just above the tail bone.
• Coccyx = tailbone The tailbone coccyx is a single bone consisting of four fused vertebrae, is located in the tail region
• Sternum = Breast bone The ribs are 12 pairs of bones connected to the vertebral column in the back and the sternum in the front, forming a protective cage around the heart and lungs.
• The Appendicular skelleton is consists of 126 bones that make up the upper and lower extremities
• The upper extremitties consist of 64 bones (32 pairs) the Clavicle or collarbone, the Scapula or shoulder blade the Humerus or upper-arm bone ,the Radius and Ulna or forearm bones , the Carpals or wrist bones ,the Metacarpals or hand bones, the Phalanges or finger bones
• The three bones of the pelvic girdle or hip bone are : ilium, ischium, pubis
• Surfaces of bones : Articular Cartilage ,Joint Cavity with synovial fluid ,Synovial
• ligament/o = iigament - bands of connective tissue called ligaments sorround the joint capsule, connecting the bones,and strengthening the joint.
• burs/o = bursa Act as cushions and help prevent injury
• ten/o,tend/o and tendin/o = tendon - Bands of connective tissue called tendons bind muscle to the bones on either side of the joint.
• amphi. = both sides; double - somewhat immovable joints,or amphiarthroses such as the joint between the vertebrae.
• diarthrosis = "movable joint" - freely movable joints or diarthroses such as those in the shoulders,fingers and knees. The surfaces of the bones are covered with articular cartilage which is very smooth and slippery.