Skeletal System PDF

‫الجهاز الهيكلي‬ Skeletal System  Function of skeletons Skeletons have three major functions – Support – Movement – Protection of internal organs  There are three main types of skeletons –Hydrostatic skeleton –Exoskeleton –Endoskeleton  Hydrostatic skeleton – Consists of...

‫الجهاز الهيكلي‬ Skeletal System  Function of skeletons Skeletons have three major functions – Support – Movement – Protection of internal organs  There are three main types of skeletons –Hydrostatic skeleton –Exoskeleton –Endoskeleton  Hydrostatic skeleton – Consists of fluid held under pressure in a closed body compartment – Protects body parts by cushioning them from shock – Provides body shape, which can be changed by contracting muscles in the body wall – Provides support for muscle action – Earthworms, hydras, and jellies have hydrostatic skeletons  The hydrostatic skeleton of Earth worm Fluid fills the coelom to support the The hydrostatic skeleton of Hydra body shape and movement  Exoskeleton Exoskeleton is rigid external skeleton. It can be hard or leathery – The exoskeleton of arthropods Shell (exoskeleton) is made of chitin – The shells of mollusks are exoskeletons made of calcium carbonate  Endoskeleton – Invertebrate endoskeletons Consists of hard or leathery supporting elements situated among the soft tissues – Most echinoderms, including sea urchins and sea stars, have an endoskeleton of hard plates beneath their skin Figure 30.2D – Vertebrate endoskeletons consist of cartilage or a combination of cartilage and bone  Vertebrates Endoskeleton 1- Cartilage Chondrocytes are cartilage producing cells Abundant extracellular matrix – Fibers: collagen & elastin – Jellylike ground substance of complex sugar molecules – 60-80% water (responsible for (hyaline cartilage) the resilience ‫)المرونة‬ – No nerves or vessels  Types of cartilages 1. Hyaline cartilage: flexible and resilient – Chondrocytes appear spherical – Lacuna – cavity in matrix holding chondrocyte – Collagen the only fiber. – End of long bone, trachea , nose and larynx and knee joints 2. Elastic cartilage: highly bendable – Matrix with more elastic fibers than collagen fibers. – Epiglottis and outer ear 3. Fibrocartilage: resists compression and tension – Rows of thick collagen fibers alternating with rows of chondrocytes (in matrix) – Intervertebral disc  2- Bone Tissue components of bones: 25% water, 25% protein fibers; 50% mineral salts. Function of bones: – Growth – Support, protection – Allowing movement – Mineral bank: storage for calcium and phosphorus – Blood production; hemopoesis in red bone marrow – Energy storage; adipose tissue in yellow bone marrow  Bone Cells Bone cells live in a matrix of flexible protein fibers and hard calcium salts. Protein fibers resist cracking and calcium salts resist compression Osteoblasts: Young bone-forming cells that cause the extracellular matrix of bone to develop are responsible for new bone formation Osteocytes: Mature bone cells that maintain the structure of bone. Osteocytes are the most abundant cell type of bone, representing 95% of all bone cells in skeletally mature adult bone tissue Osteoclasts: Dissolve Bone (bone is resorbed By osteoclasts)  Long Bones Found in the limbs Each bone is made of shaft of bone called diaphysis End of the bone called epiphyses Wall consists of dense tissue (compact bones) Central canal is filled with marrow contains the yellow marrow that stores fat Spongy bone contains the red marrow that produces blood cells Joint: where two bones meet  Compact Bone Osteocytes need to be in contact with blood vessels in order to get the nutrients they need, and to get rid of waste The bone forms ring pattern around canals called Haversian canals which contain blood vessels and nerves. The system is called Harvesion system or Osteon  Spongy (cancellous) Bone Spongy or cancellous bone is found at the ends of the long bones (epiphysis). It is surrounded by the compact bone. Spongy bone forms branching bony plates containing spaces filled with the red marrow (site of hemopoiesis, blood cells formation) The human skeleton is a unique variation The human skeleton consists of 206 bones Human skeleton is divided into: 1- Axial skeleton – Supports the axis, or trunk, of the body – Consists of the skull, backbone, and, in most vertebrates, a rib cage 2- Appendicular skeleton – Supports the paired appendages – Consists of bones of the pectoral girdle (shoulder), upper limbs, pelvic girdle, and lower limbs in humans  Axial Skeleton Skull – Cranial bones – Facial bones Vertebrae – 7 cervical – 12 thoracic – 5 lumbar – Sacrum and coccyx Ribs : 12 pairs  The vertebrae - There are 26 vertebrae - The vertebral column forms a dorsal backbone protecting the spinal cord - Disks between the vertebrae act as padding and shock absorbers while allowing movement between vertebrae - The vertebral column serves directly or indirectly as the anchor for all other bones of the body.  Ribs and Sternum All the ribs connect directly to thoracic vertebrae in the back, and all but 2 pairs connect directly or indirectly by cartilage to the sternum in the front. The lower ribs are called floating ribs because they are not attached to the sternum. Numbered according to attachment to thoracic vertebrae 1-7 attached to sternum 8-10 attach to 7 (indirectly to sternum) 11, 12 “floating” Ribs and Sternum  Appendicular Skeleton The appendicular skeleton consists of bones in the pectoral and pelvic girdles and the appendages attached to them. (126 bones total) The pectoral (shoulder) girdle and its appendages (arms and hands) are specialized for flexibility. Pelvic (hip) girdle and its appendages (legs and feet) are specialized for strength.  Pectoral girdle and Appendages (Arm, and Hand) Individual parts of the pectoral girdle are loosely linked by ligaments. It divided to I-Clavicle: Connects to the sternum in front II- Scapula: scapula lies in the upper back Appendages: The Humerus fits into the socket of the scapula, which provides little stability , prevent shoulder dislocation. -The Humerus joins the Radius and Ulna at the Elbow -There are 8 bones of the wrist, the Carpals, and 5 bones of the hand, the Metacarpals, with 14 Phalanges forming the digits. Pectoral Girdle, Arm, and Hand  Pelvis and appendages Pelvic girdle consisted of 2 large, heavy hip bones: I- Innominate (ilium, ischium, pubis) II- Sacrum- Appendages Leg, and Foot The Femur is the largest bone of the body, in the thigh. The Tibia forms the shinbone and the inner lower leg bone ‫القصبة‬ The Fibula forms the outer lower leg bone. ‫الشظية‬ - There are 7 Tarsals (ankle), 5 Metatarsals (foot), and 14 Phalanges (toe bone) Pelvic Girdle, Leg, and Foot  Joints Joints of the skeleton link bones together and are often classified by how much movement they allow. 1- Fibrous joints: immovable joints which are sutured together e.g the bones of the cranium (skull) 2- Cartilaginous joints: slightly movable joints which are bones held by cartilage e.g Epiphyseal plate, rib / sternum joint and intervertebral joints. 3- Synovial joints: freely movable joints which are found in as example in Knee and elbow. Immovable joints Cartilaginous joints Synovial joints