Human Body Systems Skeletal System Chapter 17 1

Human Body Systems Skeletal System

Chapter 17 -1: The Skeletal System 1. The skeletal system is all of the bones in the human body. n At birth the skeleton contains about 350 bones. The adult skeleton has only 206 bones. n Of these 29 are in the skull, 26 in the backbone, 25 in the sternum & ribs, 64 in the shoulders, arms and hands and 62 in the pelvis, legs and feet. n

Types of bones n Bones are classified by shape and size. Shape/Size Example Long Femur Short Carpals Flat Sternum Irregular Pelvis

Bone structure 2. Bone is made of layers of living tissue. n The membrane that covers the bone is called the periosteum. n Large bones are hollow and are filled with bone marrow. Bone marrow produces red and white blood cells. n A smooth thick layer of tissue called cartilage separates the bones from each other and reduces friction. n

A ligament is a band of tissue that holds bones together at the joints. n 3. Two types of bone n A. Compact bone is the hard strong layer of bone. n B. Spongy bone is found at the ends of long bones and has open spaces in it to make it lightweight. n 4. Two types of joints n Immovable joints allow little or no movement. Ex – Skull bones. n Movable joints allow the body a wide range of movement. n

Types of movable joints n n n 5. Four types of movable joints A. Pivot: one joint rotates in a ring of another joint. Ex – Head/neck joint B. Ball and Socket: One bone has a rounded end that fits into a cup-like cavity in another. Ex – Shoulder and hip joints C. Hinge: Back and forth movement like the hinge of a door. Ex – knees and elbows D. Gliding: One part of a bone slides over another bone. This is the most common joint in the body. Ex – wrists and ankles

Functions of the skeletal system 6. The five main functions of the skeletal system. n A. Shape and support the body. n B. Protects the internal organs. n C. Gives muscles a place to attach. n D. Produces blood cells (marrow) n E. Stores minerals (calcium and phosphorus) n

Bone cells 7. Two types of bone cells. n A. Osteoclasts – cells that break (cut) down bone. n B. Osteoblasts – cells that build bone up. n