Skeletal System - Unit IV PDF

Unit IV Functions of the skeletal system 1. Support A. Form the internal framework that supports the body and cradle its soft organs. B. Bones of the legs act as pillars to support the trunk when a person stands and the rib cage supports the thoracic wa...

Unit IV Functions of the skeletal system 1. Support A. Form the internal framework that supports the body and cradle its soft organs. B. Bones of the legs act as pillars to support the trunk when a person stands and the rib cage supports the thoracic wall. 2. Protection A. Bones protect soft body organs 3. Movement A. Skeletal muscles, attached to bones by tendons, use the bones as levers to move the body and its parts. 4. Blood cell formation https://www.youtube.com/watch?v=6h7WEaOeuZ8 5. Storage A. Fats are stored and can be found beneath the skin (subcutaneous fat), around internal organs (visceral fat), and in the central cavity of bones (bone marrow fat: 70% of adult bone marrow volume and 10% of total fat). Classification of bone tissue B. Ca with P maintain the bone mass necessary to support the skeleton. 90% of total phosphorus is stored in bone and the remaining phosphorus is distributed in soft tissues. Phosphorus helps filter waste in the kidneys and also helps reduce muscle pain after a workout. Four Shapes of bones: Human skeleton has 206 bones 1. Long bones Femur Epiphyseal line It has a plate of hyaline cartilage found in children and adolescents, located in the metaphysis at the ends of each long bone. In adults, who have stopped growing, the growth plate (epiphyseal plate) is replaced by an epiphyseal line. Structures of a long bone: A. Epiphysis / Diaphysis Long bone consist of a shaft called diaphysis and two expanded ends called epiphysis that attach with the other bones. B. Metaphysis It is the area between the growth plate and the shaft. It also contains the epiphyseal growth plate, the site of new longitudinal bone growth. Growth plates are located between the widened part of the shaft of the bone (metaphysis) and the end of the bone (epiphysis). The long bones of the body do not grow from the center outward. Instead, growth occurs at each end of the bone around the growth plate. This region (metaphysis) functions to transfer loads from weight-bearing joint surfaces to the diaphysis. C. Medullary Canal The central cavity of bone shafts where red bone marrow and/or yellow bone marrow (adipose tissue) is stored; hence, the medullary cavity is also known as the marrow cavity. D. Bone Marrow Bone marrow is a spongy substance found in the center of the bones. It manufactures bone marrow stem cells and other substances, which in turn produce blood cells. Bone marrow produces red blood cells that carry oxygen, white blood cells that prevent infection and platelets that control bleeding. E. Periosteum The thin layer of connective tissue that covers the outer surface of a bone in all places except at joints (which are protected by articular cartilage). It contributes to bone elongation and modeling in growth and development, and when the bone is injured, participates in its recovery. F. Endosteum Covers the surface of the medullary cavity, the trabeculae of the spongy bone tissue and covers the wall of the various canals that pass through the compact bone. G. Articular cartilage Articular cartilage is the highly specialized connective tissue of diarthrodial joints. To provide a smooth, lubricated surface for articulation and to facilitate the transmission of loads with a low frictional coefficient 2. Short bones Short bones are "short": cubelike. They do not have any cavity similar to the medullary cavity of the long bones. Short bones are made mostly of spongy bone tissue, but their outer parts are made of a thin crust of compact bone tissue 3. Flat bones Flat bones are "flat", platelike. They are thin and do not have any cavity similar to the medullary cavity of the long bones. The outer part of a flat bone is made of a layer of spongy bone tissue sandwiched between two layers of compact bone tissue. 4. Irregular bones Irregular bones are all the weird-shaped bones that do not belong in any other category. They do not have any cavity similar to the medullary cavity of the long bones. Irregular bones are made mostly of spongy bone tissue enclosed by a thin crust of compact bone tissue Divisions of the Skeletal System 1. Axial skeleton It consists of the bones of the skull, ossicles of the middle ear, hyoid bone, vertebral column, and rib cage. There are 29 bones of the head which include: 1.1 Eight (8) cranial/head bones Others skull structures Sutures of the Skull: These are articulations and joints where the bones come together. Articulations. A joining or connecting together loosely to allow motion between parts. Lambdoid. It connects the occipital bone with the two parietal bones. Coronal. The right and left coronal sutures run from each ear to the sagittal suture at the top of the head. The right and left coronal sutures run from each ear to the sagittal suture at the top of the head. When one of these sutures closes too early, the baby may have a flattened forehead on the side of the skull that closed early (anterior plagiocephaly). Suture may begin to fuse by the age of 24. Average Suture closes between the ages of 30 years old and 40 years old. Sagittal “arrow”. A dense, fibrous connective tissue joint between the two parietal bones of the skull. This glides over the other during the passage of the child. Squamous. Acts as an expansion joint between the parietal and temporal bones. As the brain grows during infancy, the sutures allow the skull to grow and expand. Occipitomastoid. The cranial suture between the occipital bone and the mastoid portion of the temporal bone. It is continuous with the lambdoidal suture. Metopit. Separate the two frontal bones at birth and is the first skull suture to close physiologically, starting as early as at 3 months and generally being completely fused at the age of 8 months. Metopit sutures play an important role in the growth of brain and also for normal growth of the skull 1.2 Fourteen (14) facial bones Others facial structures Orbital Complex: The area that surrounds each eye and the nasal complex, which surrounds the nasal cavity. This includes the frontal bone, maxilla and lacrimal bone. Nasal Complex: This encloses the nasal cavities and the paranasal sinuses connected to the nasal cavities. There are 12 cranial bones: 2 nasal, 2 maxilla, 2 palatine and 2 lacrimal bones, 1 ethmoid, 1 sphenoid, 1 frontal and 1 vomer bones. The 14 facial bones provide for muscle attachment; facial expressions; eating of food; help to separate nasal and oral cavities, house the sinuses and to protect the entrances to the digestive and respiratory systems. The 8 cranial bones and 14 facial bones (totaled 22 head bones) function to protect the brain and entrance to the digestive and respiratory systems. 1.3 One hyoid bone 1.4 Six (6) auditory (ear) bones The ear ossicles include (malleus, incus, and stapes). The 25 bones of the thorax (sternum & 24 ribs The 26 bones of the vertebral column (24 vertebrae, a sacrum and coccyx) 2. Appendicular skeleton It comprises the upper and lower limbs, the pectoral girdles and pelvic girdles To facilitate movement of the human body. Other functions are to provide shape to the arms and legs, as well as to maintain mineral homeostasis in the body. 2.1 Upper limbs / extremities 2.2 Lower limbs / extremities 2.3 Pectoral Girdle 2.4 Pectoral Girdle Bone Cells and Bone Formation  Osteoblasts Osteoblasts Form new bones Dissolve old and damaged bone Ossification (or osteogenesis) in bone remodeling is the process of laying down new bone material by cells called osteoblasts. It is synonymous with bone tissue formation. https://www.youtube.com/watch?v=LC80hvjpHWo Bone consists of a dense compact and a spongy cancellous structure. Though compact bone forms an organized outer shell, cancellous bone consists of thin interlocking plates called trabeculae. Osteoblasts and osteoclasts are the osteocytes or bone cells that make up bone tissue. Bone continually renews its structure and strength through remodeling. Osteoclasts break down existing bone and osteoblasts build up new bone. In normal bone, adequate physical stress and changing blood calcium levels, prompt osteocytes to initiate bone remodeling. Osteoblasts emit a cytokine that transforms immature osteoclasts into mature osteoclasts. In a process called bone resorption, mature osteoclasts use enzymes to remove existing to remove existing bone tissue, then osteoclasts release chemicals that stimulate immature osteoblasts to mature and release osteoprotegerin, a protein that deactivates osteoclasts, stopping bone resorption, in response bone formation occurs. Mature osteoblasts deposits called osteoid and a matrix that contains minerals such as calcium and phosphorus as well as a strong flexible protein called collagen. Calcium and phosphorus crystallize or mineralize the osteoid then transform into sturdy hydroxyapatite crystals completing the bone formation process. In both men and women, before midlife bone resorption and bone formation are balanced. Hormones and other factors influenced bone remodeling. For example, estrogen hormone suppresses osteoclasts inhibiting resorption to help maintain bone strength. After midlife, estrogen levels fall and osteoclasts activity exceeds bone formation so bones weaken resulting to osteoporosis (bone resorption exceeds bone formation). As a result the trabeculae in cancellous bone become fewer and farther apart so that the compact bone thins and overall the becomes weak, fragile and prone to fractures. Types of Ossification 1. Intramembranous Ossification https://www.youtube.com/watch?v=Vwethc4jt7U Forms the flat bones of the skull, face, jaw, and center of clavicle. bone is formed in sheet-like layers that resemble a membrane. 2. Endochondral Ossification https://www.youtube.com/watch?v=Z-vRCYuH4uI Forms most bones in the body, mostly long bones, and replace cartilage with bone. Articulations or Joints It is where two or more bones come together or meet. Most joints contain a single articulations. Each articulation contains the names of two bones (or sockets). Acetabulofemoral joint (Hip Joint): Is where the acetabulum of a coxal bone articulates with the head of the femur.  Glenohumeral joint (shoulder joint): Is where the glenoid cavity of the scapula articulates with the head of the humerus. Some joints have more than one articulation (where more than two bones articulate with each other). The knee includes articulation between the femur and tibia (tibiofemoral joint) and the femur and patella (patellofemoral joint). The knee includes articulation between the femur and tibia (tibiofemoral joint) and the femur and patella (patellofemoral joint). The elbow joint has three articulations: the humeroradial joint (articulation of the humerus and radius), the humeroulnar joint (articulation of the humerus and ulna), and the proximal radioulnar joint (the proximal articulation of the radius and the ulna). Articulations vary in the amounts of movement they allow as well as their structures. Joints are classified based on function, the amount of movement they allow. General Types (Movement) of Joints I. Functional joints 1. Synarthrosis (no mobility). Most synarthrosis points are fibrous joints (e.g. sutures of skull). 2. Amphiarthrosis (slight mobility). Most amphiarthrosis joints are cartilaginous (e.g. intervertebral disc). 3. Diarthrosis (freely movable) including all synovial joints. II. Structural joints (according to the type of tissue that connects the bones to each other) 1. Fibrous joint: bones are joined by dense regular connective tissue that is rich in collagen fibers. The subclasses of synarthroses include: 1.1 Sutures – periosteum of articulating bones interdigitate making a very stable joint, for example sutures of the skull 1.2 Gomphosis – joint between the teeth and the alveolar process of the mandible or maxilla, it is held in place by the periodontal ligaments 1.3 Syndesmosis – located between two parallel articulating bones, they are joined by a long fibrous membrane called the interosseous membrane. These joints are classified as amphiarthroses including articulation of the radius and the ulna 2. Cartilaginous joint: bones are joined by cartilage. Most of this type of joint allow for some movement, so they are amphiarthrosis. There are two types of cartilaginous joints: Symphysis – bones are joined by Symphysis – bones are joined by a pad made of fibrocartilage like a pad made of fibrocartilage like intervertebral discs. intervertebral discs. 3. Synovial joint: bones have a synovial cavity filled with synovial fluid and are united by the dense irregular connective tissue that forms the articular capsule that is normally associated with accessory ligaments. They are diarthrosis as they allow for free movement. Synovial joints can in turn be classified into six groups according to the type of movement they allow: https://www.youtube.com/watch?v=dJZz7hBoALs https://www.youtube.com/watch?v=Ei4seya3dOg Detailed Video on Bone Remodeling https://www.youtube.com/watch?v=Ei4seya3dOg Basic Video on Bone Remodeling