System 3 Skeletal System 3 Skeletal

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Skeletal System

By: Abby and Tessa

Terms

 Amp arthrosis- a slight movable joint

 Diaphysis- the long straight shaft of a long bone

 Diarthrosis- freely movable joint characterized by a joint cavity; also called a a synovial joint

 Endochondral ossification- method of bone formation in which cartilage is replaced by bone

 Epiphyseal plate- the cartilaginous plate between the epiphysis and diaphysis of a bone, responsible for the lengthwise growth of a long bone

 Epiphysia- the end of a long bone

Five functions of the skeletal system

 Bones support the soft organs of the body and support the body against the pull of gravity

 Bones protect soft body parts such as the brain, spinal cord and heart

 Bones work with muscles to produce movement

 Bones store minerals, especially calcium

 Most blood cell formation, hematopoiesis, occurs in red bone marrow

Compact and spongy bone on the basis of structural features

 The microscopic unit of compact bone is the osteon or Haversian system

 It consists of an osteonic canal, lamellae of matrix, osteocytes in lacunae, and canaliculi

 In compact bone the osteons are packed closely together

 Spongy bone is less dense

 Consists of bone trabeculae around irregular cavities that contain red bone marrow

 The trabeculae are organized to provide maximum strength to a bone

Different classifications of bones

 Longer than they are wide; an example is the femur in the thigh

 Short bones are roughly cube shaped; examples include bones in the wrist

 flat bones have inner and outer tables of compact bone with a diploi of spongy bone in the middle; examples include the bones of the cranium

 Irregular bones are primarily spongy bone with a thin layer of compact bone; examples include the vertebrae

 Long bones have a diaphysis around a medullary cavity, with an epiphysis at each end. The epiphysis is covered by periosteum and lined with endosteum. All bones have surface markings that make each one unique

Bone development (osteogenesis) and growth

 Osteoblasts, osteocytes, and osteoclasts are three types of cells involved in bone formation and remodeling.

 Intramembranous ossification involved the replacement of connective tissue membranes by bone tissue. Flat bones of the skill develop this way.

 Most bones develop by endochondral ossification. In this process, the bones first form as hyaline cartilage models, which are later replaced by bone.

 Long bones increase in length at the cartilaginous epiphyseal plate.

When the epiphyseal plate completely ossifies, increase in length is no longer possible.

 Increase in diameter of long bones occurs by appositional growth.

Osteoclasts break down old bone next to the medullary cavity at the same time osteoblasts form new bone on the surface.

Axial and appendicular skeletons

 The axial skeleton together with the appendicular skeleton form the complete skeleton.

Another definition of axial skeleton is the bones including the vertebrae, sacrum, ribs, and sternum.

Articulations

 Synarthroses are immovable joints where the bones are held together by short fibers; structures are synarthrosis joints

 Slightly movable joints are amphiarthroses. In this type of joint the bones are connected by hyaline cartilage or fibrocartilage. The symphysis pubis and intervertebral discs are examples of apmphiarthrotic joints.

 Joints the are freely movable are diarthroses. The bones are held together by fibrous joint capsule that is lined with synovial membrane. these joints are sometimes called synovial joints. There are six types: gliding, condyloid, hinge, saddle pivot, and ball-and-socket.

Quiz Chapter recall Answers

1.

G

2.

D

3.

F

4.

I

5.

H

6.

B

7.

A

8.

B

9.

E

10.

J

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