Human Anatomy Lecture 6 PDF

HUMAN ANATOMY LECTURE 6 AL TURATH UNIVERCITY 1ST STAGE DENTISTRY DR.NIBRAS RIYADH The Skeletal System Parts of the skeletal system Bones (skeleton) Joints Cartilages Ligaments( bone to bone) (tendon=bone to muscle)  The human skeleton consists of 206 named...

HUMAN ANATOMY LECTURE 6 AL TURATH UNIVERCITY 1ST STAGE DENTISTRY DR.NIBRAS RIYADH The Skeletal System Parts of the skeletal system Bones (skeleton) Joints Cartilages Ligaments( bone to bone) (tendon=bone to muscle)  The human skeleton consists of 206 named bones Bones of the skeleton are grouped into two principal divisions: Axial skeleton Skull bones, auditory ossicles (ear bones), hyoid bone, ribs, sternum (breastbone), and bones of the vertebral column - Appendicular skeleton Consists of the bones of the upper and lower limbs (extremities), plus the bones forming the girdles that connect the limbs to the axial skeleton The axial skeleton consists of the bones of the skull, ossicles of the middle ear, hyoid bone, vertebral column, and rib cage. Appendicular Skeleton FUNCTIONS OF SKELETAL SYSTEM SUPPORT: Hard framework that supports and anchors the soft organs of the body. PROTECTION: Surrounds organs such as the brain and spinal cord. MOVEMENT: Allows for muscle attachment therefore the bones are used as levers. STORAGE: Minerals and lipids are stored within bone material. BLOOD CELL FORMATION: The bone marrow is responsible for blood cell production. Structure of Bone Tissue There are two types of bone tissue: compact and spongy differ in density. there are three types of cells that contribute to bone homeostasis. 1- Osteoblasts are bone-forming cell, 2-osteoclasts resorb or break down bone, and 3-osteocytes are mature bone cells.  Bone tissue is a specialized form of connective tissue characterized by a mineralized extracellular matrix. Mineral = calcium phosphate in the form of hydroxyapatite crystals [Ca₁0 (PO4)(OH)2] Calcium Carbonate: CaCO3 Magnesium Hydroxide: Mg(OH)2 Fluoride and Sulfate Matrix = mainly collagen (type I, VI) along with other matrix proteins All collagen molecules ~ 90% of total weight of bone matrix Compact Bone composed of the two types of osseous tissue.It makes up the outer cortex of all bones and is in immediate contact with the periosteum. Compact bone Solid, strong bone located along the diaphysis of long bones Provides solid structure to the skeletal frame Forms a hollow tube called the medullary cavity  Microscopic structure of compact bone The structural unit of Compact bone is the osteon, or haversian system. Each osteon Is an elongated cylinder Oriented parallel to the Long axis of the bone spongy bone (cancellous bone) ⚫ sponge like meshwork consisting of trabeculae The spaces within the meshwork are continuous and occupied by marrow and blood vessels. Spongy (cancellous) bone does not contain osteons. It consists of trabeculae surrounding many red marrow filled spaces It forms most of the structure of short, flat, and irregular bones, and the epiphyses of long bones. Spongy bone tissue is light and supports and protects the red bone marrow. Reduces the weight of the bone Provides strength to bones especially against forces of compression Standing, running Classified according to shape ⚫ thelocation of spongy and compact bone varies with bone shape. Long bones - longer in one dimension These bones typically have an elongated shaft 1. Long Bones: and two expanded ends one on either side of the shaft. The shaft is known as diaphysis and the ends are called epiphyses. Examples: Humerus, femur etc  Short bones - nearly equal in length and diameter These bones are short in posture and can be of any shape. Examples: The carpal and tarsal bones Have compact, spongy bone and a marrow space on the inside Articular surfaces are covered with hyaline cartilage  Flat bones - thin and platelikee.g., parietal bone, scapula, sternum  Thick compact bone with an intervening layer of spongy bone.  Irregular bones  ⚫ e.g., vertebrae, hip bones, ethmoid bone Examples of Flat Bones in the Body Skull Bones Frontal bone Parietal bone Occipital bone Nasal bone Lacrimal bone Vomer Arm Bones Scapula Chest Bones Sternum sesamoid bone small bone commonly found embedded within a muscle or tendon near joint surfaces, existing as focal areas of ossification and functioning as a pulley to alleviate stress on that particular muscle or tendon. Blood supply to long bone comes from three sources  Nutrient artery system  Metaphyseal and epiphyseal system  Periosteal system