Skeletal system Skeletal System Functions 206 bones in

Skeletal system

Skeletal System Functions • 206 bones in the body • • • FUNCTIONS Supports body and provides shape. Protects internal organs. Movement and anchorage of muscles. Mineral storage. (Calcium and phorus) Hemopoiesis (formation of blood cells)

How Bones Grow • Our bones are constantly renewing themselves. • Up to 10% of your bones is eaten away • and replaced each year. • There are 3 basic types of bone cells: osteoblasts, osteocytes, osteoclasts

Types of Bone Cells • Osteoblasts • Are the “bone-builders” and are responsible for building new bone • Osteocytes • These are mature bone cells • These cells live for about 20 years

Bone Formation • Embryo skeletal starts as osteoblasts (primitive embryonic cells) – then change to cartilage. • At 8 weeks, OSSIFICATION begins. (Mineral matter begins to replace cartilage) Infant bones soft because ossification not complete at birth.

Fontanel • Soft spot on baby’s head

Long Bones • The 206 bones are divided into 4 types based on their form: Long bones, short bones, flat bones, and • Long Bones constructed for weightbearing and movement. Examples are the femur and the humerus

Parts of a Long Bone • DIAPHYSIS – shaft • EPIPHYSES – ends • MEDULLARY CAVITY – center of shaft, filled with yellow bone marrow, which is mostly fat cells, also cells that form white blood cells. • ENDOSTEUM – lines marrow cavity • PERIOSTEUM – tough, outside covering of bone – contains blood vessels, lymph vessels and nerves. • Shaft is made of COMPACT BONE – ends are SPONGY BONE. Ends contain red marrow where red blood cells are made.

Long Bone Diagram

Short Bones • Short Bones make flexible movement possible. Examples are wrist bones (carpals) and foot bones (tarsals)

Flat Bones • Flat Bones - these bones help provide organ protection and are important sites for hemopoiesis (blood cell formation. ) Examples are skullbones, sternum, and ribs.

Irregular Bones • Irregular Bones - odd shapes that do not fit into the other three categories. They have unique shapes related to their function. • Examples are the vertebrae and the ear bones

Two Main Divisions of the Skeleton • AXIAL – skull, spinal column, ribs, sternum, hyoid

Skull Diagram

Spine-Vertebral Column • Encloses the spinal cord • Vertebrae – separated by pads of cartilage = intervertebral discs • Cervical vertebrae (7) • Thoracic vertebrae (12) • Lumbar vertebrae (5) • Sacrum • Coccyx

Ribs and Sternum • Sternum divided into 3 parts – bottom tip is XIPHOID PROCESS • 12 pairs of ribs – first 7 are true ribs – connected to sternum by cartilage • next 3 are false ribs – cartilage connects them to 7 th rib (not sternum) • next 2 are floating

Two Main Divisions of the Skeleton • APPENDICULAR – shoulder girdle, arms, pelvis, legs

Appendicular Skeleton clavicle – collar bone scapula – shoulder blade humerus – upper arm radius and ulna – lower arm • carpals – wrist bones – held together by ligaments • metalcarpals – hand bones • phalanges – fingers • • • pelvis – 3 bones (ilium, ischium, and pubis) • femur – upper leg, longest and strongest bone in body • tibia and fibula – lower leg • patella – kneecap • tarsal bones – ankle • calcaneus – heel bone • metatarsals – foot bones

Labeled Skeleton