Characteristics Bones The Introduction 206 bones hard, rigid bones cells (osteocyctes) are a mixture of a ground substance, collagen fibres, P, Ca highly resistant to compression and tension also somewhat elastic Functions of the Skeleton
Structure of the Skeleton Axial Skeleton -vertebral column -skull -bony thorax (ribs) Appendicular Skeleton -pelvic girdle -pectoral girdle -arms and hands -legs and feet Activity Short Group the box of bones into categories by shape Long Flat Irregular Shape
Classification of Bones Short Long tubular shell with cavity in middle - ex. humerus, femur Flat no marrow cavity, thin - ex. cranium, ribs, scapula no marrow cavity, small, square - ex. wrist, ankle Irregular Shape no marrow cavity odd shaped - ex. vertebra Minor Bone Types Sesamoid formed in tendons - ex patella (knee cap) functions: - 1) act as pulley to increase mechanical advantage - 2) they strengthen connective tissues to protect from oblique forces Tendons will tear most easily where they are bent (put under shear stresses) at a joint. Having a bone form within a tendon near the place it is often flexed makes it into a composite material that is better able to resist tearing. Tendons are largely made up lots of tiny strings of a protein known as collagen. These strings are linked together and are quite strong when pulled on (put under tension), but are much weaker when bent sideways (put under shear stress). Tendons are thus good at resisting tension, adding a bone to a tendon will help prevent it from tearing
Wormian small jig saw fragments found along sutures of the skull Read pg. 127 and Anatomy of Long Bone Handout : The Formation of Bone Anatomy of the Long Bone
Epiphysis Diaphysis Articulating Cartilage Epiphyseal Line Spongy Bone Compact Bone Medullary Cavity Periosteum Endosteum Arteries Epiphysis Two types of bone Compact Bone Spongy Bone
Two types of bone growth Bone Formation and Remodelling Intramembranous Ossification between membranes (ex. bone collar, flat bones) Endochondral Ossification within hyaline cartilage (ex. long bones) Bone (Re)modelling a balance between the function of osteoblasts and osteoclasts Function: new bones a constant process injury Bone Cells Osteoblasts build bone by laying osteoid within the cartilage Osteocyctes trapped osteoblasts; communication Osteoclasts release acid and enzyme to break bone down
Growth of a Long Bone Primary Centres of Ossification Primary Centers of Ossification Osteoblasts have invaded the spaces and using the available calcium, lay down bony plates in an irregular honey comb pattern Osteoclasts (bone destroying cells) become active by breaking down the newly formed spongy bone to clear space for the medullary cavity In utero Birth The process moves gradually outwards towards the periosteum and lengthwise towards the end of the bone
Child In utero Birth Child
Summary ossification is the process of bone formation Long Bones start as bars of hyaline cartilage inside the cartilage, bone grows and is then remodeled at three sites (epiphysis and diaphysis) osteoblasts build walls of bone out of the hylaine cartilage osteoclasts tear down these walls this process creates: -a medullary cavity in the diaphysis -lighter spongy bone at the two epiphysis compact bone forms underneath the periostium to create a hard outer layer or bone collar Red Marrow at the epiphyseal plate three process help grow the bone lengthwise hyaline cartilage grows towards the ends this is turned into bones by osteoblasts which is then broken down to create a cavity and/or spongy bone inside by osteoclasts the epiphyseal line is a bone remnant of the hyaline cartilage bone remodelling is a balance between the function of osteoblasts and osteoclasts new bones a constant process injury hematopoiesis - the formation of RBC and WBC found in infants found in: cavities of longs bones spongy bone of flat and irregular bones, hip and head of long bones during adolescence red marrow changes to yellow in long bones persists in spongy bone after adolescence Yellow Marrow found in cavities of long bones becomes area of fat storage can be converted back to Red if individual is anaemic Activity Using handout, text and skeleton. label the anatomical names count the number of bones
Cranium (8) Ears (6) Face (14) Hyoid (1) Clavicle (2) Bones Sternum (1) Ribs (12 x 2) Humerus (2) The Skeleton Hip/Coaxl (2)) (2) Sacrum (1) Ulna (2) Radius (2) Carpal (8 x 2) Vertebrae (24) Metacarpals (5 x 2) Scapula (2) Phalanges (14 x 2) Femur (2) coccyx (1) Patella (2) Tibia (2) Fibula (2) Tarsals (7 x 2) Metatarsals (5 x 2) Phalanges (14 x 2)