The Skeletal System. The skeleton. There are ~206 bones in your body. The longest bone in your body is your femur. (Can you find your femur?) Almost all animals have bones. Bones contain calcium. What foods do you eat that contain calcium? The human skeleton has two divisions:
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The Skeletal System
The skeleton There are ~206 bones in your body. The longest bone in your body is your femur. (Can you find your femur?) Almost all animals have bones. Bones contain calcium. What foods do you eat that contain calcium? The human skeleton has two divisions: 1. The Axial Skeleton – skull, vertebral column, & rib cage. 2. The Appendicular Skeleton – arms, legs, shoulder and pelvic girdle.
AXIAL SKELETON BONES The Skull: 8 CRANIAL BONES 13 FACIAL BONES. 22 TOTAL The Ears: 6 BONES HYOID (floats freely in the throat) 7 TOTAL The Vertebral Column: 7 CERVICAL (NECK) VERTEBRAE 12 THORACIC 5 LUMBAR 1 SACRUM (5 fused vertebrae) 1 COCCYX (4 fused into tailbone) 26 TOTAL The Rib Cage (Thoracic cage): 12 PAIRS OF RIBS (24 bones total) 1 STERNUM (breastbone). 25 TOTAL
APPENDICULAR SKELETON BONES THE PECTORAL GIRDLE: 4 BONES 54 HANDS AND WRIST 60 TOTAL THE PELVIC GIRDLE: 2 BONES 58 THE LOWER LIMB 60 TOTAL THE FEET AND ANKLES: 54 TOTAL
STRUCTURE OF BONES Bones are a solid network of moist, living cells (OSTEOCYTES) and fibers (COLLAGEN) that are supported by a matrix (DEPOSITS) of CALCIUM salts. Each bone is surrounded by a Tough Membrane called the PERIOSTEUM, a fibrous connective tissue membrane whose collagen fibers merge with the tendons and ligaments that are attached to the bone. The periosteum contains a network of blood vessels, which supply Oxygen, Nerves and Nutrients to the bone.
STRUCTURE OF BONES CONT. The Jointed Surfaces of Bones are covered with ARTICULAR CARTILAGE, which provides a smooth surface for movement. Beneath the Periosteum is a thick layer of COMPACT BONE. One of two types of Bone tissues. Compact Bone is dense. A thick layer of compact bone enables the shaft of long bones (called the Diaphysis) to endure the large amount of stress it receives upon impact with a solid object. The second type of Bone Tissue, SPONGY BONE, it is the inside layer of compact bone. Spongy Bone IS NOT Soft and Spongy, but actually quite strong. Near the Ends of Bones (EPIPHYSIS) where force is applied, Spongy Bone is organized into structures that resemble the supporting girders of a bridge.
OSTEOCYTES Embedded in COMPACT and SPONGY Bone are Cells known as OSTEOCYTES, that can either deposit the calcium salts in bone or absorb them again. OSTEOCYTES are responsible for bone growth and changes in the shape of bones.
BONE MARROW The Cavities of Bones contain a Soft Tissue called BONE MARROW. THERE ARE TWO TYPES OF BONE MARROW FOUND IN MOST BONES: A. YELLOW BONE MARROW - primarily fills the shafts of long bones and is made up of some blood vessels and nerve cells, but consists mostly of FAT cells (adipose tissue). It serves as an energy reserve. It can also be converted to red bone marrow and produce blood cells when severe blood loss occurs. B. RED BONE MARROW - found in spongy bone, the ends of long bones, ribs, vertebrae, the sternum, and the pelvis - produces red blood cells and special white blood cells called lymphocytes, as well as platelets.
JOINTS: WHERE TWO BONES MEET… … OR PLACES WHERE TWO BONES COME TOGETHER, PERMIT THE BONES TO MOVE WITHOUT DAMAGING EACH OTHER. Joints are responsible for keeping bones far enough apart so they do not rub against each other as they move. At the same time, joints hold the bones in place. THE CLASSIFICATION OF JOINTS IS BASED ON THE AMOUNT OF MOVEMENT POSSIBLE:
IMMOVABLE JOINT or FIXED JOINTS: allow no movement between bones. FREELY MOVABLE JOINT: MOST OF THE JOINTS OF THE BODY: the ends of the bones are covered with a layer of Cartilage that provides a smooth surface at the joint. SLIGHTLY MOVABLE JOINT or SEMI MOVABLE JOINTS: permit a small amount of movement. The joints are also surrounded by a Fibrous Joint Capsule that helps hold the bones together and at the same time allows for movement. The places where the bones of the SKULL meet (SUTURE) meet are examples of immovable joints. The joints between the two bones of the lower leg (TIBIA and FIBULA) and the joints of the vertebrae are examples of slightly movable joints. Four main types…see next 2 slides.
TYPES OF FREELY MOVABLE JOINTS: BALL AND SOCKET JOINT - Permits circular movement - the widest range of movement. The shoulder joint, which enables you to move your arm up, down, forward and backward, as well as to rotate it in a complete circle. HINGED JOINT - Permits a back-and-forth motion. The knee enables your leg to flex and extend. The elbow, which allows you to move your forearm forward and backward.
TYPES OF FREELY MOVABLE JOINTS cont.: PIVOT JOINT - Permits rotation of one bone around another. The elbow enables your hand to turn over. It also allows you to turn your head from side to side. SADDLE JOINT - Permits movement in two planes. This type of joint is found at the base of the thumb. The elipsoid and plane joints are also types of freely movable joints but are less commonly referred to in most texts.