Skeletal System PDF

Skeletal System By Dr. Radwa Ismail Ilos To define bone and cartilage To know types of bones To differentiate between compact and cancellous bone To differentiate between membranous and cartilaginous ossification To know different shapes of bone with examples To identify blood s...

Skeletal System By Dr. Radwa Ismail Ilos To define bone and cartilage To know types of bones To differentiate between compact and cancellous bone To differentiate between membranous and cartilaginous ossification To know different shapes of bone with examples To identify blood supply of bone  Skeletal System The Skeletal System (skeleton) is composed of: Cartilage Cartilage Bone Bone  Skeletal System -It is softer than bone, less rigid and elastic Costal Cartilage -It forms the temporary skeleton of developing Articular Cartilage fetus -It is retained throughout life in certain sites: 1- Articular cartilages 2- Costal cartilages 3- Air passages as nasal, laryngeal, tracheal and bronchial 4- External ear  Note on: Structure of a long bone The central tubular region of the bone, called the diaphysis. The lumen of the diaphysis is called medullary cavity. flares outward near the end to form the metaphysis, which contains a largely cancellous, or spongy, interior. At the end of the bone is the epiphysis, which in young people is separated from the metaphysis by the epiphyseal plate, or growth plate. The metaphysis is the neck portion of a long bone between the epiphysis and the diaphysis. It contains the growth plate. The periosteum is a connective sheath covering the outer surface of the bone.  Classification of bones 1- According to form (Structure): compact and cancellous 2- According to development: membranous and cartilaginous ossification 3- According to shape.  Forms of Bones 1- Compact (hard or ivory) bone: -It is hard and dense -Forms the surface layer of all bones and tubular shaft of long bones. - Consists of number of cylindrical units called Haversian system 2-Spongy, trabecular (cancellous) bone: - Looks like a sponge - Filled with red bone marrow - Formed of trabeculae - Found inside the hard bone and forms the ends of long bones  Development of bones By two main processes: 1- Membranous ossification -occurs in bones for protection of essential organs as vault of skull 2- Cartilaginous ossification:  Cartilaginous ossification Cartilaginous ossification: At first a model of the future bone is formed from cartilage and then ossified in two steps : Primary center of ossification: forming diaphysis, appears during the fetal life Secondary center of ossification: forming epiphysis, appear after birth. which ossifies leaving : - A plate of epiphyseal cartilage between the epiphysis and diaphysis. - Articular cartilage covering the ends of the bone. Shapes of Bones 1- Long Bones: - Have long tubular shaft with central medullary cavity - e.g. humerus femur - Small example of long bones are metacarpals and phalanges 2- Short bones: -They are subjected to pressure -have thin cortex of compact bone with interior of cancellous bone -e.g. carpal and tarsal bones Flat Bones: -It is formed of inner and outer layers of compact bone -internal layer of spongy bone (diploe) is found between the above layers -e.g. skull, ribs, sternum and scapula Irregular Bones: -Any bone not easily assigned to previous groups - e.g. vertebrae Pneumatic Bones: -They are containing air spaces - e.g. maxillary, sphenoidal, frontal and ethmoidal sinuses and mastoid bone Sesamoid Bones: - Small bones deposited in the tendons of muscles to reduce friction -e.g. patella in quadriceps tendon  Types of bones Long Short Flat bone Irregular Pneumatic Sesamoid bone bone Humerus Carpal Ribs Vertebrae Maxillary Patella Femur bones Sternum Frontal Tarsal bones  Blood supply of bone The arterial supply of bone comes from: 1- Periosteal arteries: -the main source of blood supply -supply the outer compact bone Epiphyseal artery 2- Articular arteries: -Supply joints and ends of bones Metaphyseal artery -each artery divides into epiphyseal and metaphyseal branches -form vascular circle 3- Nutrient arteries: -Artery enters the bone through a nutrient canal -it divides into proximal and distal branches - Supply bone marrow and inner compact bone of the shaft Nutrient artery MCQ Which of the following is a considered long bone? A. Carpal bones B. Maxillary bone C. Humerus D. Patella Which of the following describes compact bone? A. Contain spaces filled with red marrow B. Consist of network of trabeculae C. Found at the end of the long bones D. Found at the outer surface of all long bones MCQ The nutrient artery supplies which of the followings? A. Supply the bone marrow of the shaft B. Supply the compact bone of the shaft C. Supply the epiphysis D. Supply the metaphysis Which of the following describes primary ossification center? A. It is responsible for formation of epiphysis B. It appear in the ends of bones after birth C. It is responsible for formation of epiphysis D. It appear during the fetal life in the middle of shaft of bone