The Skeletal System

The Human Skeleton Made up of 206 bones Bones come in many different forms Many parts of the body are made up of several bones joined together i.e. Each hand is made up of 27 bones Skeletal is hard and durable Bones are composed primarily of calcium Bones are able to repair themselves (with the help of casts, splints, pins, etc.)

Role of the Skeleton Provides structural support for the body Protects vital organs i.e. Rib cage protects the lungs and heart Red blood cells and platelets are produced in the marrow of bones Bones serve as a reservoir to regulate calcium and other minerals Works in conjunction with the muscular system to cause movement *Table 2.1 – page 10

The Structure of the Skeleton Divided into two main parts Axial skeleton Appendicular skeleton Appendicular--> Axial-->

The Axial Skeleton 80 bones Made up of the vertebral column (spine), the skull, and the rib cage Vertebrae protect the spinal cord The skull/cranium protects the brain Ribs protect the lungs and heart 7 “true” pairs 3 “false” pairs 2 “floating” pairs

The Appendicular Skeleton 126 bones Includes movable limbs and supporting structures Upper limbs are attached to the shoulder girdle Two scapulae and two clavicles The humerus attaches to move the arms Lower limbs are attached to the pelvic girdle Two hip bones and the sacrum The femur attaches to move the legs

Types of Bones 1. Long bones – found in the arms and legs 2. Short bones – most common in the wrists and ankles 3. Flat bones – are flat and thin, often protect vital organs from injury 4. Irregular bones – odd-looking bones such the vertebrae 5. Sesamoid bones – small, flat bones wrapped within tendons that move over bony surfaces i.e. The patella

Types of Bones Flat Short Sesamoid Irregular Long

Anatomy of a Long Bone Articulating cartilage: located on both ends of the bone. Allows for smooth movement within joints Periosteum: outer connective tissue, covers entire length of bone. Does not unite with articulating cartilage. Medullary cavity: found inside the shaft of the bone. Filled with red (blood-cell formation) and yellow (adipose tissue) bone marrow.

Continued... Compact bone: more dense part of the bone. Responsible for the bone's structural integrity Diaphysis: shaft of the bone Cancellous/spongy bone: filled with marrow Epiphysis: the very ends of a long bone.