Long Bone Formation PDF

The Skeletal System - Introduction NSCI5720 Vertebrate Anatomy & Physiology Learning Objectives Know the main functions of the skeletal system Be able to name the different bone cells and briefly explain each of their functions Describe the two types of bone Be able to describe the st...

The Skeletal System - Introduction NSCI5720 Vertebrate Anatomy & Physiology Learning Objectives Know the main functions of the skeletal system Be able to name the different bone cells and briefly explain each of their functions Describe the two types of bone Be able to describe the structure of a typical long bone, and the functions of each of the parts of a long bone What is the Skeletal System? The skeleton is a framework of bones These bones support and protect the soft tissues of the body. Bones The bones that make up the skeletal system also serve a variety of functions Functions of the Skeletal System Support Protection Movement (leverage) Blood cell formation Storage of minerals Functions of the Skeletal System Support ⚬ For soft tissue (like scaffolding). ⚬ A strong frame that supports the body and gives it it’s shape Functions of the Skeletal System Protection ⚬ Strong bones protect delicate vital organs & tissues by surrounding them partially or completely ⚬ e.g. skull protects brain, ribs protect heart etc. Functions of the Skeletal System Movement (leverage) ⚬ Bones act as levers for muscles ⚬ Bones are attachment sites for skeletal muscles (via tendons) ￭ These allow muscles to move joints Functions of the Skeletal System Blood cell formation ⚬ In the bone marrow of some bones Storage of minerals ⚬ e.g. Calcium, phosphorous ⚬ Acts like a mineral bank Bone Cells Bone is made up of 3 types of cells: Osteoblasts Osteocytes Osteoclasts Bone Cells Osteoblasts: ⚬ Cells that form the matrix of bone ⚬ The matrix hardens through a process called ossification ⚬ (“blast” = to produce,”B” for “building”) Osteocytes ⚬ These are osteoblasts that are trapped in the bony matrix called lacunae (like jail) ⚬ Contact with other osteocytes and their blood supply is through cellular channels called canaliculi (like slots in a jail cell) ⚬ Can revert back to osteoblasts if needed e.g. to form new bone after an injury Osteoclasts: ⚬ Cells that eat away at bone ⚬ Used to re-model bone that is not needed ⚬ Enable the body to extract Calcium from bones for use in blood ⚬ (“C” for “chewing” or “cleaning”) Bone Cells Bone Cells Bone Structure Two main types of Bone: Cancellous Bone ⚬ Light, spongey Cortical or Compact Bone ⚬ Heavy, dense Cancellous Bone Also known as “spongy bone” Light but very strong Consists of a network of bony spicules called trabeculae ⚬ Bony spicules appear random but are organised into a mesh- like network along regions of biomechanical stress ￭ Can handle the forces from muscles, gravity and other bones Spaces in between the trabeculae contain bone marrow ⚬ used for blood cell production (haematopoiesis) and fat storage Found in the end of long bones and surrounding the medullary cavity. Is surrounded by an outer layer of compact bone. Overall function: strong but light-weight bone that allows for bone marrow storage and aligns to specific forces that the bone is under (trabeculae) Cancellous Bone Compact Bone Aka Cortical Bone Heavy, dense, very strong Makes up the shaft of long bones and the outside layer of all bones Function: Strength and protection, allows weight bearing without forces bending/damaging the bone Compact Bone Made up of tiny, tightly compacted cylinders of bone called Haversian systems (or osteon). ⚬ Run lengthwise to the bone Consists of a multilayered cylinder composed of circular layers of ossified bone matrix arranged around a central Haversian canal. ⚬ The Haversian canal contains blood vessels, lymph vessels, and nerves that supply the osteocytes.  Compact Bone The osteocytes are located at the junctions between the layers of bone that make up each Haversian system. In cross section, these layers of bone look like the growth rings of a tree. Tiny channels through the bone, called canaliculi, allow osteocytes to contact each other and exchange nutrients and wastes. Compact Bone Cancellous/Spongy vs Compact/Cortical Cancellous/Spongy vs Compact/Cortical  For interest only - Bone Shapes you only need to know about long bones Long Bones for the exam :) Most bones of the limbs Short Bones Like cubes/marshmallows eg. carpal & tarsal bones Flat Bones Thin & flat eg. skull, scapulae, pelvic bones Irregular Bones Miscellaneous eg. vertebrae, some skull bones, sesamoid bones (many are in tendons) - patella  Bone Membranes Periosteum = A membrane covering the outer surfaces of bones (except the articular/joint surfaces) Function: contains blood vessels and nerves that supply bones Also contains cells involved in growing and repairing bone  Bone Membranes Endosteum = A membrane lining the hollow interior surface of bones (lines the medullary cavity and trabeculae) Function: contains cells involved in bone growth, remodelling and repair Long Bones Longer than they are wide Most bones of the limbs Epiphysis ⚬ Line of growth of bone ⚬ Proximal and distal ⚬ Light, cancellous bone covered by a thin layer of compact bone. Contains bone marrow. Diaphysis ⚬ Main section of long bone ⚬ Made of strong compact bone - weight-bearing Long Bones Epiphyseal Plates ⚬ Plates of cartilage aka growth plates ⚬ Sites of bone growth ⚬ Weak - fractures common in young animals ⚬ Ossify in adults to become solid bone Medullary cavities containing red and yellow marrow Red Marrow - Blood cell production ⚬ Larger proportion in younger animals Yellow Marrow - storage of fat ⚬ Majority of bone marrow in adults Blood vessels, nervous tissue Long Bones Cancellous vs Compact- Which is which? Cancellous/Spongy vs Compact/Cortical Can you name the parts & functions of the parts of the Long Bone? Epiphysis Diaphysis Epiphyseal Plates Medullary cavities Red Marrow Yellow Marrow Periosteum Endosteum  Long Bones Epiphysis - Contains red marrow and epiphyseal plates, Line of growth of bone Diaphysis - Main section of long bone, weight bearing Epiphyseal Plates - Sites of bone growth Medullary cavities - Contain red and yellow marrow Red Marrow - Blood cell production Yellow Marrow - Storage of fat Periosteum - Membrane covering the outer surfaces of bones (except the articular/joint surfaces). Blood vessels, nerves, and cells for bone growth, remodeling & repair. Endosteum - Membrane lining the hollow interior surface of bones. Bone growth, remodeling & repair.