Chapter 7 Skeletal System

HW-None 1. Take out notes. 2. Do not get your models yet!

Skeletal system functions: -muscle attachment -protection -support -blood cell production –Hematopoiesis-red bone marrow producing blood cells -storage of minerals Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Types of bones Flat-cranium, ribs, scapula, sternum Short-cube shape, wrist and ankle Long-thigh, forearms, toes Irregular-vertebrae Sutural bones-Wormian bones –Location classification –Between joints of certain cranial bones Sesamoid bones-small bones in tendons (patella, 2 hand, 1 foot)

Parts of a Long Bone 1.epiphysis-wide end of a bone 2.Hyaline cartilage-covers the epiphysis. 3.Diaphysis-shaft of bone (long part) 4. Metaphysis-epiphyseal plate area 5.periosteum-covers bone -attach to ligaments and tendons -nutrition and growth -made of vascular connective tissue (help with repair & formation) y.

Medullary or Marrow cavity Space with fatty yellow bone marrow in adults Endosteum-inner lining of the medullary canal MORE TO COME!!

Go to page 127 in the book to help label the picture.

Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Two types of bone tissue Spongy bone –Cancellus bone –Does not contain osteons (segments of bone) –Contains thin plates called trabeculae –Spaces between bones are filled with red marrow –Plates have osteocytes –Found in short, flat, and irregular bones -ends of long bones -can handle compression Compact Bone-dense bone –Shaft of bone; bear weight

Microscopic Structure of Long Bones -BONE HAS TONS OF MATRIX (lamallae) *matrix made of collagen (strength) and inorganic salts (calcium phosphate) make it hard and resist crushing -OSTEONS-segment of bone -put tons of osteons together=bone connected by Volkman’s canals.

1 osteon has several parts * central canal (Haversian canal) filled with nerves *perforating canals (Volkmann’s canals)-connect central canals of blood vessels to periosteum; run perpendicular to haversian canal) * osteocytes-bone cells -lacunae-residence of osteocytes or chamber -canaliculi-canals that connect lacunae or osteocytes; passageway for substance and key to communication yI

Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Bone Ossification A. Bones form by replacing connective tissue (hyaline cartilage) in the fetus. B.2 types: -intramembranous bones-form sheetlike layers of connective tissue -example: flat bones of skull -osteoblasts are active forming osteocytes (these are mature bone cells) -endochondral bones-cartilage masses form -eventually hyaline cartilage is replaced by bone -most common Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Video 1 development-endochondral-ossification You tube video Na0&feature=related Endochondral Bones 1.They first develop as hyaline cartilage models and are then replaced with bone. -replace from the outside first

2. Cartilage is broken down in the diaphysis (middle of the bone) and progressively replaced with bone while the periosteum (outside of bone) develops on the outside. 3. Cartilage tissue is invaded by blood vessels and osteoblasts (from periosteum) -form spongy bone from middle to outside -primary ossification center

4.Osteoblasts beneath the periosteum lay down compact bone outside the spongy bone. 5. Secondary ossification centers appear later in the epiphyses. 6. A band of hyaline cartilage, the epiphyseal plate(growth plate), forms between the two ossification centers. -shaft and ends are the ossification centers Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

7. Osteoclasts break down the matrix and are replaced with bone-building osteoblasts that deposit bone in place of calcified cartilage. 8. Epiphyseal plates are responsible for lengthening bones while increases in thickness are due to intramembranous ossification underneath the periosteum. KE Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Homeostasis of Bone Tissue 1.Osteoclasts tear down and osteoblasts build bone throughout the lifespan, with an average of 3% to 5% of bone calcium exchanged annually. *Bone cancers have overactive osteoclasts. *Prostate cancer that has moved to the bone marrow can have the opposite effect (osteoblasts are creating) Copyright  The McGraw-Hill Companies, Inc. Permission required for reproduction or display.