29-3 The Skeletal System

-The Skeletal System is an internal framewwork of calcium hardened bones that shape and support the human body, while also giving protection to vital organs.

-The Human Skeleton is made up of 206 bonees.

-80 bones make up the axial (central) skelleton

-126 bones make up the appendicular skeletton.

-Bone tissue occurs in 2 forms:

1. Compact Bone Tissue is dense and provides support.
2. Spongy Bone Tissue consists of hardened fibers with many spaces.

-The spaces of the bone are filled with marrow.

1. Red Bone Marrow produces red blood cells and is found in spongy bone.
2. Yellow Bone Marrow stores fat and is found in the hollows of the arm and leg bones.

-The outside of the bone is covered by a mmembrane called periosteum.

-There are two main types of bone cells:

1. Bone cells which produce new bone are called osteoblasts.
2. Bone cells that become trapped within their calcium rich matrix are called osteocytes.

-Haversian canals are hollow channels thatt run the length of the bone and provide blood to the bone.

-Joints are cartilaginous junctions between bones.

1. Immovable Joints permit little or no movement.
   • sutures of the skull
2. Slightly Moveable Joints permit limited movement
   • joints of the vertebrae
3. Freely Moveable Joints permit full range motion.
   • Hinge Joints (Knees and Elbows)
   • Ball-n-Socket Joints (Shoulders and Hips)
   • Pivot Joints (Radius Bone in the Elbow)
   • Plane Joints (Carpals and Tarsals)
   • Saddle Joints (Thumbs)