The Skeletal System

1. The Skeletal System

2. The 5 functions of the skeleton • 1. Supports the body • 2.Protects internal organs • 3. Provides for movement • 4. Stores mineral reserves • 5. Provides a site for blood cell formation

3. The skeleton • Is divided into two parts • Appendicular skeleton • Consists of the bones of the legs and arms as well as the pelvis and shoulder areas • Axial skeleton • Supports the central axis of the body and consists of the skull, vertebral column and rib cage • There are 206 bones in a adult human

4. Structure of Bones • Bones are a solid network of LIVING cells and proteins fibers that are surrounded by deposits of calcium salts • The outside of bones is made of periosteum and compacts bone • Compact bone has tunnels of blood vessels that run throughout the bone to provides nutrients to the cells • The inside middle regioncontains soft tissue called bone marrow • The inner ends of bones is made of spongy bones • Strong but light weight

5. Bone Marrow • Two Types, Yellow and Red • Red marrow produces red blood cells, some white blood cells and also platelets • Yellow marrow is made up primarily of fat cells

6. Bone Development • All bone is initially cartilage • Cartilage is a network of protein fibers • Cartilage is replaced by bone during the process of bone formation called OSSIFICATION

7. 3 Types of bone cells` • Osteocytes • Are mature bone cells embedded in the bone matrix • Osteoblasts • Produce bone • Osteoclasts • Break down bone • WHY both osteoblasts and osteoclasts?

8. Growth plates • Most long bones (arms and legs) have growth plates on either end • Growth plates are a line of cartilage between the middle and end of bones that allows a bone to continue to grow lengthwise • During late adolescence the cartilage plate is replaced by bone and the person stops growing

9. Joints • Joints are places where a bone attaches to another bone • Permit bones to move without damaging each other • There are 3 types of joints • Immovable • Slightly Moveable • Freely Moveable

10. Immovable Joints • Allow for no movement • Bones are locked together by connective tissue and are usually fused together • Example is the different bones in the skull that have fused together at the joints

11. Slightly Moveable • Permit a small amount of restricted movement • The are slightly separated from each other • Examples are the joints between vertebrae and the joints between the two bones of the lower leg (fibia and tibia)

12. Freely moveable joints • Joints the permit movement in 1 or more directions • 4 distinct types • Ball-and-Socket joint • Shoulder and hip are examples • Hinge joint • Knee • Pivot joint • Elbow • Saddle joint • Knuckle joints

13. Structure of freely moveable joints • Cartilage covers the surface where the 2 bones come together • Joints are surrounded by a joint capsule that helps hold the bones together • Consists of Ligaments-which is a layer of tough connective tissue that holds the bones together • Cells in the outer layer of the capsule produce synovial fluid, which helps joints slide over each other smoothly

14. Prevention of Skeletal System Disorders • Doctors recommend three things • 1. Eat calcium in your diet, especially as you get older • 2.Do weight bearing exercise • 3. Remain active

15. Muscular System • The skeleton can not move without muscles, and muscles would not be able to provide locomotion without the skeleton, they must work together

16. Types of muscle tissue • Muscles is found everywhere in the body—not just beneath the skin • There are 3 different types of muscle tissue • 1. skeletal • 2. cardiac • 3. smooth

17. Skeletal muscles • Are attached to bones usually • Are responsible for voluntary movement and are consciously controlled by the CNS • Often called striated muscles

18. Cardiac muscles • Found only in the heart • Striated like skeletal muscles, but cells are smaller • Is not under direct control of the CNS • The heart will still self stimulate and beat even if the brain isn’t sending impulses • Is connected via gap junctions between each cardiac muscle cell • Allow for electrical impulses to travel from one cell to another

19. Smooth Muscles • Are not under voluntary control • Is spindle shaped • Found in walls of stomach and intestines and also blood vessels • Can function without nervous stimulation • Connected by gap junctions • These junctions allow for electrical impulses to travel directly from one cell to its neighbor

20. Muscle Contraction • A muscle contracts when the thin filaments (actin) in a muscle fiber slide over the thick filaments (myosin). • This essentially shortens muscle fibers • Requires large amounts of energy in the form of ATP

21. Control of muscle contraction • Impulses form motor neurons stimulate contraction • Neuromuscular junctions: are the points where motor neurons meet muscle cells • Axons of motor neurons release the neurotransmitter acetylcholine • This stimulates muscle contraction

22. Strong vs. Weak contractions • What is the difference in muscle contraction when you lift a paper or when you lift something heavy • Your brain only stimulates a few muscle cells to contract when lifting something light, but when maximum effort must be exerted, all cells are stimulated to contract

23. Muscle/Bone interactions • Skeletal muscles generate force and produce movement by pulling on body parts, usually bones • Tendons are tough connective tissue that joins bones and muscles together • Tendons attach to bones to make them act as levers and joints as fulcrums • Several muscles surround each joint and usually work in opposite pairs • Allows for movement both ways in the joint

24. Keeping muscles healthy • What role does exercise play? • Prevents fatigue • Prevents muscle atrophy • Increases physical endurance • Prevents injury • Decreases fat content in muscles