2THE SKELETAL SYSTEM: OVERVIEW I. INTRODUCTIONThe organs of the skeletal system include the bones and the structures that connect bones to other structures, including ligaments, tendons, and cartilages.The adult skeleton is composed of 206 separate bones.
3Division of skeleton Axial skeleton Includes the bones of: skull, vertebral column, and rib cage.These bones are involved in protection, support, and carrying other body parts.Appendicular skeletonBones of upper & lower limbs and the girdles (shoulder bones and hip bones) that attach them to the axial skeleton.Involved in locomotion and manipulation of the environment.Ahmad ata
5AXIAL SKELETON 1) Skull: 28 irregular shaped bones from the skull. The skull consists of two major division:Cranium is formed by eight bones.Face is formed by fourteen bones.
6AXIAL SKELETON 2) VERTEBRAL COLUMN Divided into 5 main regions Cervical spine (7)Thoracic spine (12)Lumbar spine (5)Sacrum (5)Coccyx (4)The 5 sacrum vertebrae and 4 coccyx vertebrae are fused to form one solid bone.
8AXIAL SKELETON THORAX 12 pairs of ribs Joined to thoracic vertebrae Top 10 ribs joined to sternumRemaining two have “free” ends – ‘floating’
9APPENDICULAR SKELETON Forms mainly the extremities of the body and their connections to the axial skeletonConsists of- limbs (arms & legs)- shoulder and pelvic girdles
10Bone Classification 4 types of bones: Femur Long Bones Short Bones Much longer than they are wide.All bones of the limbs except for the patella (kneecap), and the bones of the wrist and ankle.Consists of a shaft plus 2 expanded ends.Short BonesRoughly cube shaped.Bones of the wrist and the ankle.Carpal BonesAhmad ata
11Bone Classification Types of bones: Flat Bones Irregular Bones Thin, flattened, and usually a bit curved.Scapulae, sternum, (shoulder blades), ribs and most bones of the skull.Irregular BonesHave weird shapes that fit none of the 3 previous classes.Vertebrae, hip bones, 2 skull bones ( sphenoid and the ethmoid bones).SternumSphenoid Bone
12Parts of long bone1) diaphysis: main shaft like structure, its hollow cylindrical shape, its functions of providing strong support bone.2) epiphysis: both end of long bone, epiphysis have a bulbous shape that provide generous space near joint.For muscle attachment and give stability of joint.
13Parts of long bone3) articular cartilage thin layer of hyaline cartilage that covers joint surface.4) Periosteum: dense white fibrous membrane that cover bone except at joint surface and anchoring bone to muscles.5) Marrow cavity: a tubelike hollow space in the diaphysis of long bone.6) endosteum: a thin epithelial membrane that line the medullry cavity.
15Composition of bone matrix Inorganic salts: the hardness of bone result from the deposition of high specialized chemical crystal of calcium and phosphorous called hydroxyapatite, the process called calcification in addition to mg, Na, sulphate and fluoride.Organic substance: collagenous fiber and mixture protein and poly saccarids called ground substance, provide support and adhesion between cellular and fiberous.Chondroitin and glucosamine are required for repair and maintenance of bone and cartilage.
17Types of bone cells 1. Osteoblasts Bone-forming cells found in all bone surfaces Bone-building cells.Synthesize and secrete collagen fibers and other organic components of bone matrix.serve as a framework for the deposition of calcium and phosphate calcificationThe blue arrows indicate the osteoblasts. The yellow arrows indicate the bone matrix they’ve just secreted.
18Types of bone cells 2. Osteoclasts Giant multinucleate cells Responsible for the active erosion of bone mineralsContain large numbers of mitochondria and lysosomes
19Types of bone cells3. Osteocytes—mature, nondividing osteoblast surrounded by matrix, lying within lacunaeAhmad ata
21Bone MarrowSpecialized type of soft, diffuse connective tissue; called myeloid tissueSite for the production of blood cellsFound in medullary cavities of long bones and in the spaces of spongy bone
22Microscopic Structure of Compact Bone Contains many cylinder-shaped structural units called osteons, or Haversian systemsFour types of structures make up each osteon:Lamella—concentric, cylinder-shaped layers of calcified matrixLacunae—small spaces containing tissue fluid in which bone cells are located between hard layers of the lamella
23Microscopic Structure of Compact Bone Canaliculi—ultrasmall canals radiating in all directions from the lacunae and connecting them to each other and to the Haversian canalHaversian canal—extends lengthwise through the center of each osteon and contains blood vessels and lymphatic vessels
25Bone MarrowTwo types of marrow are present during a person’s lifetime:Red marrowFound in virtually all bones in an infant’s or child’s bodyFunctions to produce red blood cellsYellow marrowAs an individual ages, red marrow is replaced by yellow marrowMarrow cells become saturated with fat and are no longer active in blood cell production
26Bone MarrowThe main bones in an adult that still contain red marrow include the ribs, bodies of the vertebrae, the humerus, the pelvis, and the femurYellow marrow can alter to red marrow during times of decreased blood supply, such as with anemia, exposure to radiation, and certain diseases
27Functions of BoneSupport—bones form the framework of the body and contribute to the shape, alignment, and positioning of the body partsProtection—bony “boxes” protect the delicate structures they encloseMovement—bones with their joints constitute levers that move as muscles contractMineral storage—bones are the major reservoir for calcium, phosphorus, and other mineralsHematopoiesis—blood cell formation is carried out by myeloid tissue
28Regulation of Blood Calcium Levels Skeletal system (cont.)Homeostasis of calcium ion concentration essential for the following:Bone formation, remodeling, and repairBlood clottingTransmission of nerve impulsesMaintenance of skeletal and cardiac muscle contraction
29Regulation of Blood Calcium Levels Mechanisms of calcium homeostasisParathyroid hormonePrimary regulator of calcium homeostasisStimulates osteoclasts to initiate breakdown of bone matrix and increase blood calcium levelsIncreases renal absorption of calcium from urineStimulates vitamin D synthesis
30Mechanisms of calcium homeostasis (cont.) CalcitoninProtein hormone produced in the thyroid glandProduced in response to high blood calcium levelsStimulates bone deposition by osteoblastsInhibits osteoclast activityFar less important in homeostasis of blood calcium levels than parathyroid hormone
31Fracture Types Open (compound) bone ends penetrate the skin. Closed (simple) bone ends don’t penetrate the skin.Spiral ragged break caused by excessive twisting forces. Sports injury/Injury of abuseGreenstick bone breaks incompletely. One side bent, one side broken. Common in children whose bone contains more collagen and are less mineralized
33Clinical Conditions Osteomalacia Literally “soft bones.”Includes many disorders in which osteoid is produced but inadequately mineralized.Causes can include insufficient dietary calciumInsufficient vitamin D fortification or insufficient exposure to sun light.RicketsChildren's form of osteomalaciaMore detrimental due to the fact that their bones are still growing.Signs include bowed legs, and deformities of the pelvis, ribs, and skull.What about the above x-ray is indicative of rickets?
34Clinical Conditions Osteomyelitis Inflammation of bone and bone marrow caused by pus-forming bacteria that enter the body via a wound (e.g., compound fracture) or migrate from a nearby infection.Fatal before the advent of antibiotics.
35Clinical Conditions Osteoporosis Osteoporosis is a disease that thins and weakens the bones to the point that they become fragile and break easily. Women and men with osteoporosis most often break bones in the hip, spine, and wrist, but any bone can be affected. You can't "catch" osteoporosis or give it to someone else.