Skeletal Anatomy Test Notes: Functions, Composition, and Development of Bones

1. Review Skeletal Anatomy Test Notes Skeletal Physiology "We are an intelligent species and the use of our intelligence quite properly gives us pleasure. In this respect the brain is like a muscle. When it is in use we feel very good. Understanding is joyous.” Carl Sagan, 1979 To learn about bone physiology. Title: Anat & Phys 10/31/06 Class Topics Objectives: Friday, December 20, 20195:46 AM

2. Class Assignments What By When • Due this class period • Due next class period • Due in the future

3. Functions of the Skeletal System • Protection • Support • Movement • Storage of Calcium • Blood Cell formation

4. Parts of a long bone • Diaphysis • shaft of the bone • Epiphysis • ends of bones • Periosteum • Dense irregular connective tissue lining the bones • Articular cartilage • Hyaline – lining the joint

5. Diaphysis • Made of compact bone • Very strong and limited open space within • Easily broken w/stress against long axis • Yellow marrow • Used to store fat (make blood cells in extreme conditions) • found in medullary cavity • hollow region of compact bone • Lined with endosteum (thin dict membrane)

6. Epiphysis • Spongy bone (cancellous) • thin layer of compact bone covering it • more open spaces - like lattice • Resists stress from many directions • Red Marrow - Myeloid tissue • Hematopoiesis - formation of blood cells • erythropoiesis • lymphopoiesis

7. Walden Henry David Thoreau (1817 – 1862) • I went to the woods because I wished to live deliberately, to front only the essential facts of life, and see if I could not learn what it had to teach, and not, when I came to die, to discover that I had not lived. I did not wish to live what was not life, living is so dear; nor did I wish to practice resignation, unless it was quite necessary. I wanted to live deep and suck out all the marrow of life, to live so sturdily and Spartan-like as to put to rout all that was not life, to cut a broad swath and shave close, to drive life into a corner, and reduce it to its lowest terms, and, if it proved to be mean, why then to get the whole and genuine meanness of it, and publish its meanness to the world; or if it were sublime, to know it by experience, and to be able to give a true account of it in my next excursion. • “Dead Poets Society”

8. Bone Composition • Bones are composed of bone tissue, cartilage, dense connective tissue, blood-forming tissue, blood vessels, and nerves • Bone tissue (matrix) • organic • collagen • inorganic • hydroxyapatite

9. Hydroxyapatite • Mineral crystals made from • calcium carbonate • calcium phosphate • 2/3 of total weight of bone • very hard and not very flexible

10. Bone Cells • Osteoblasts • found within periosteum • Actively produce matrix • Osteocytes • Osteoblasts that are trapped within the matrix • trapped in lacunae • Osteoclasts • wander the tissue • dissolve the mineral salts of matrix

11. Microscopic Structure of Bone • Lacunae • spaces where the osteocytes reside • Lamellae • thin sheets of matrix in which the lacunae are found • form circles around haversian canals or osteonic canals • Haversian canals • parallel to long axis of compact bone • contain blood vessels

12. Microscopic Structure of Bone (cont.) • How does the blood get from the vessel to the osteocytes? • Canaliculi • Each system around a haversian canal is called an osteon or haversian system • osteocytes, lacuna, canaliculi, lamellae

13. Microscopic Structure of Bone (cont.) • Volkmann’s canals • blood vessels that run perpendicular to the long axis of the bone • connect osteons • Spongy bone • trabeculae - thin plates (beams) of bone • leaving space for red marrow

16. From: http://www.octc.kctcs.edu/gcaplan/anat/Notes/API%20Notes%20H%20Skeletal%20System.htm From: http://www.mhhe.com/biosci/ap/histology_mh/canalicl.jpg

17. Bone Development and Growth • Intramembranous Bones • start formation 5th week after conception • in between two embryonic membranes • precursor (stem) cells turn to osteoblasts • Spongy bone on the inside and compact on the outside

18. Bone Development and Growth • Examples • flat bones of skull • mandibles • clavicles • Endochondral bones • all other bones except those that are intramembranous • Starts 6th week after conception

19. Endochondral Bones • Precursor cells change into chondroblasts • forms hyaline cartilage • template of skeletal system in cartilage • Blood vessels penetrate cartilage • stimulate chondroblasts to osteoblasts

22. From: http://www.accessexcellence.org/RC/VL/xrays/1wrist/hanpelu.html

23. Endochondral Bones • Primary ossification center • center of diaphysis • 1st place osteoblasts begin to work • Work out toward each epiphysis • 2ndary ossification center • epiphysis • forms spongy bone down to epiphyseal plate

24. Intersititial Growth (length) • Occurs at epiphyseal plate • chondrocytes divide and move material toward epiphysis • Closer to the diaphysis older cartilage converts to bone - increase length of diaphysis • Chondrocytes stop growing when acted upon by hormones from the pituitary gland

25. Interstitial Growth • Epiphyseal line • old epiphyseal plate in those that have ceased growth

26. Appositional Growth (width) • Osteoblasts lay down bone on surface • Osteoclasts dissolve bone • Osteoblasts work harder than osteoclasts • weight bearing exercise

27. Bone Remodeling • Continually broken down and built back up • every 30 years each bone is completely renewed