By: Helena Abidin and Taylor Walker

1. Skeletal System By: Helena Abidin and Taylor Walker

2. Invertebrate Skeletons • Framework of bones that supports and gives form to the body, protects internal organs, and provides anchorage points for muscles. • Each bone is composed of a mineral, calcium phosphate and protein. • Bones are joined by ligaments at places called joints. • The skeleton itself is composed of bone and cartilage.

3. Invertebrate Skeletons • Skeletons may be internal, endoskeletons, or external, exoskeletons. • Skeletons can also be hyrostatic. This is when organisms contract one part of their body which results in an extension of another part

4. Bone Structure • There are two classifications of bones cortical (compact) and trabecular (spongy) • Bones are organs composed of hard living tissue. • Bones are made of calcium deposits, protein. • These minerals (calcium) make bones rigid, while proteins (collagen) make bones strong and elastic.

5. Bone Structure Continued • There are 5 main parts of a bone: marrow, calcified bone, periosteum, spongy bone, and cartilage. • Bone Marrow: soft and crumbly part of the bone, which is in the center. There are two types of marrow, redand yellow. • Thered marrow produces red blood cells. When you get older, your marrow turns more yellow due to fat cell accumulation. The yellow marrow acts like an emergency reserve in case you get sick then it will produce blood cells • Calcified bone: hard but not really solid bone. • Spongy bone: is hard with tiny holes in it. • Periosteum: is thin but very strong. -it is the outer membrane, it helps to rebuild bone cells. • Cartilage: a strong material that holds two bones together and allows them to move over one another.

6. Changes in Bone Structure • The 1st skeleton to form in all vertebrate embryos is made of cartilage. • Then Osteblasts infiltrate the cartilage model and transform it into bone, the cartilage in the bone shaft breaks down and a marrow cavity is formed. • In healthy young adults a process called bone remodeling occurs. • Bone remodeling: the removal and deposits that help maintain required blood levels of calcium and phosphorus while keeping bones strong • Osteblasts help form new blood tissue. • Until about 24 years old bones are growing denser and stronger, later in life this activity declines and bones gradually weaken. • Osteoporosis: significant loss in bone density. • Deficient calcium or vitamin D intake, parathyroid problems, and physical inactivity add to risks. Declining sex hormone levels in menopause, smoking, excessive alcohol intake, and prolonged use of steroids.

7. Role of Cartilage keeps most bones in place and what gives shape to soft or fragile spots in our body Strengthens the bones in the body Found where flexibility is required Functions as a cushion in synovial joints, where it cushions any impact between the bones Does not contain blood vessels Derived from the mesoderm germ layer Osteoarthritis: cartilage covering bone thins

8. Interactions with Muscles Works together to form “muscuskeletal system” The skeleton is the frame, muscles help move the frame Muscles located on a bone Bones and muscles work together through a series of impulses and signals communicated between the brain and skeletal muscles.  When muscles contract, bones have to follow The movement of a muscle forces the bone to move with ithave both insertion and origin points

9. Works cited Farabee, M.J(2010 May 18). Muscular and Skeletal Systems. Retrieved from http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookmusskel.html Bridwell, Keith(2010 February 10). Basic Bone Structure. Retrieved from http://www.spineuniverse.com/anatomy/basic-bone-structure Falkner, Sue(2010 February 11). Cartilage and its Role in My Life. Retrieved from http://www.everydayhealth.com/blog/life-with-chronic-pain/cartilage-and-its-role-in-my-life/ Bone Structure (2010 August 5). Retrieved from http://library.thinkquest.org/05aug/01257/parts.html.