Skeletal System - Part I Bone Structure Skeletal System - Part I

Introduction Skeletal System - the entire framework of bones (206) and their cartilage, tendons & ligaments They study of bone disorders is called osteology. Orthopedics - the branch of medicine that deals with the preservation and restoration of the skeletal system and its associated structures Bones are active living tissue and therefore the organs of the skeletal system

Skeletal Functions Support Protection Assisting in movement Mineral homeostasis Production of blood cells Triglyceride storage

Bone Composition Composed of the mineral salts calcium carbonate & calcium phosphate which make up 67% of bone materials Collagen (33%) is the major protein (90%) that provides a soft framework Calcium phosphate is a mineral that adds strength and hardens the framework Small amounts of fluoride, magnesium hydroxide and sulfate Together these minerals compose crystal mineral salts called Hydroxyapatite

Types of Bones

Long Bones Greater length than width Have a distinct diaphysis and a variable number of epiphysis Slightly curved for strength Femur, humerus, ulna, radius, tibia, fibula, metacarpals, metatarsals, phalanges

Short Bones some what cubed shaped bones nearly equal in length and width spongy texture on inside of the bone Carpal (wrist) and tarsal (ankle) bones

Flat Bones generally thin and flat compact bone on anterior and posterior surfaces with spongy bone in the middle provides protection to organs great surface area for muscle attachment cranial bones, sternum, scapula, ribs

Irregular Bones complex shaped bones can’t be classified into other categories vary in the amount of spongy and compact bone vertebrae, facial bones

Sesamoid (Round) Bones small bones situated in tendons where considerable pressure develops vary in number between individuals kneecaps

Figure 7.1 - Bone Classification

Long Bone Structure Diaphysis Epiphyses (2) Metaphyses (2)` Articular Cartilage Periosteum Medullary cavity Endosteum Epiphyseal Disk

Long Bone Structure

Epiphysis The Epiphysis is the expanding portion found at the ends of a long bone. Distal/proximal ends of bone Articulating surfaces covered with hyaline cartilage articulates = forms joint w/ another bone composed mostly of spongy bone

Epiphysis d Epiphysis

Epiphyseal Plates Epiphyseal Plates are cartilaginous layers within the long bone epiphysis that grow. If an epiphyseal plate is damaged before it ossifies, elongation of the long bone may cease prematurely, pr growth may be uneven.

Epiphyseal Plate Epiphysis Epiphyseal Plate d Epiphysis

Articulating Cartilage Articulating Cartilage is a form of hyaline cartilage. It is found on the articulating portion of the epiphysis.

Articulating Cartilage Epiphyseal Plate Epiphysis Epiphyseal Plate d Epiphysis Articulating Cartilage

Diaphysis The Diaphysis is the longest portion of the bone. It is the shaft that is located in between the epiphysis found on either end of the long bone.

Articulating Cartilage Epiphyseal Plate Epiphysis Diaphysis Epiphyseal Plate d Epiphysis Articulating Cartilage

Periosteum A Periosteum is a tough, vascular covering of fibrous tissue that completely encloses the bone. It is firmly attached to the bone, and periosteal fibers are continuous with ligaments and tendons that connect to the membrane. Also helps form and repair bone tissue.

Articulating Cartilage Epiphyseal Plate Epiphysis Diaphysis Periosteum Epiphyseal Plate d Epiphysis Articulating Cartilage

Compact Bone (Cortical) The wall of the diaphysis is mainly composed of tightly packed tissue called Compact Bone. This tissue has a continuous matrix with no gaps. Outer layer of bone

Articulating Cartilage Epiphyseal Plate Epiphysis Compact Bone Diaphysis Periosteum Epiphyseal Plate d Epiphysis Articulating Cartilage

Spongy Bone (trabecular) The epiphyses are composed largely of Spongy Bone with thin layers of compact bone on their surfaces. Inner layer of bone Consists of numerous branching bony plates called trabeculae. Irregular connecting spaces between these plates helps reduce the bone’s weight and are filled with red marrow. Both compact and spongy bone are strong and resist bending.

Articulating Cartilage Epiphyseal Plate Epiphysis Spongy Bone Compact Bone Diaphysis Periosteum Epiphyseal Plate d Epiphysis Articulating Cartilage

More Structures… Compact bone in the diaphysis forms a semi-rigid tube with a hollow chamber called the Medullary Cavity. A thin layer of cells called Endosteum lines these areas. A specialized type of soft connective tissue called Marrow fills these regions.

Articulating Cartilage Epiphyseal Plate Epiphysis Spongy Bone Space Containing Red Marrow Medullary Cavity Endosteum Compact Bone Yellow Marrow Diaphysis Periosteum Medullary Cavity Epiphyseal Plate d Epiphysis Articulating Cartilage

Types of Bone Cells Osteoblasts - Bone building cells; synthesize and serete collagen fibers to build matrix of bone Osteocytes - Mature bone cells; maintain bone tissue and metabolism Osteoclasts - Large cells formed from white blood cells; break down bone tissue

Microscopic Structure Recall that bone cells called Osteocytes are in tiny, bone chambers called Lacunae. Lacunae, which form concentric circles around Central Canals or Haversian canals. Osteocytes communicate with nearby cells by means of cellular processes passing through Caniliculi. Caniliculi are cytoplasmic processes that extend outward and pass though very small tubes in the boney matrix.

More on Compact Bone Sheets of bone create Lamellae Lamellae are concentrically clustered around a central canal and form cylinder-shaped units called Osteons or Haversian Systems. It is many of these units fused together that form the substance of compact bone.

Vascularity Each central canal contains blood vessels and nerve fibers. These structures are surrounded by loose connective tissue. Blood in these vessels nourishes osteocytes associated with the central canal.

Central Canals Continued Central canals extend longitudinally through bone tissue. Transverse canals called Perforating Canals connect the central canals to one another. Perforating canals contain larger blood vessels and verves that allow the communication to take place between the central canals both near the surface and in the medullary cavity.

One Last Thing About Spongy Bone Spongy bone is also composed of osteocytes and intracellular material. This type of bone tissue does not aggregate around central canals and relies of diffusion to move nutrients into the cells. Substances diffusing into the canaliculi that lead to the surface of these thin, boney plates and nourish the cells.

Sickle Cell Anemia Recessive genetic disorder Causes sickle-shaped red blood cells. These sickle cells obstruct circulation Severe bone pain is one symptom of the disease Radiographs can reveal blocked arterial blood flow in bones of these patients

Sicle Cell and Stem Cells