Skeletal System: Bones and Joints

HUMAN ANATOMY AND PHYSIOLOGY LECTURE • CHAPTER 6 - SKELETAL SYSTEM: BONES AND JOINTS SKELETAL SYSTEM • • • Functions o Support o Protect o Movement o Storage o Blood cell production Components o Bone o Cartilage - reduce friction and model for bone formation o Tendons - attach bone to muscle o Ligaments - attach bone to bone Background Information o Bones, cartilage, tendons, and ligaments are connective tissues. o Proteoglycans ▪ large polysaccharides attached to proteins ▪ part of ground substance ▪ store water o Bone’s extracellular matrix is collagen and minerals (flexible and able to bear weight) o Cartilage’s extracellular matrix is collagen and proteoglycans (good shock absorber) o Tendons and ligaments’ extracellular matrix is collagen (very tough) • • BONE TISSUES • • BONES CLASSIFICATION OF BONES • • Short o Carpals, tarsals, phalanges Flat o Ribs, sternum, skull Irregular o Vertebrae and facial Compact Bone Tissue o Location - outer part of diaphysis (long bones) and thinner surfaces of other bones o Osteon ▪ structural unit of compact bone ▪ includes lamella, lacunae, canaliculus, central canal, osteocytes o Lamella - rings of bone matrix o Lacunae - spaces between lamella o Canaliculus - tiny canals; transport nutrients and remove waste o Central canal center of osteon; contains blood vessels Spongy Bone Tissue o Cancellous bone o Location - epiphyses of long bones and center of other bones o Trabeculae -interconnecting rods, spaces contain marrow o No osteons Based on shape: o long, short, flat, irregular Type of bone tissue: o compact and spongy (cancellous) BONE SHAPES • Long o Femur, tibia, fibula o Diaphysis ▪ shaft ▪ compact bone tissue (on outside) o Epiphysis ▪ ends ▪ spongy bone tissue o Articular cartilage ▪ covers epiphyses ▪ reduces friction o Epiphyseal plate ▪ site of growth ▪ between diaphysis and epiphysis o Medullary cavity ▪ center of diaphysis ▪ red or yellow marrow BONE CELLS • • • Osteocytes - maintain bone matrix Osteoblasts - build bone Osteoclasts - carve bone BONE FORMATION • • Ossification - process of bone formation (occurs in utero) Osteoblast’s role o build bone o after an osteoblast becomes surrounded by bone matrix it becomes an osteocyte • • • • • Ossification center - where bone formation begins Primary ossification center - where bone 1st begins to appear; forms diaphyses Secondary ossification center - forms epiphyses Intramembranous Ossification o Bone formation within connective tissue membranes o Osteoblasts build bone o Ex. Skull bones Endochondral Ossification o Bone formation inside cartilage o Cartilage models are replaced by bone o Ex. All bones (except skull) o Steps: 1. Chondroblasts build a cartilage model, the chrondroblasts become chondrocytes. 2. Cartilage model calcifies (hardens). 3. Osteoblasts invade calcified cartilage and a primary ossification center forms diaphysis. 4. Secondary ossification centers form epiphysis. 5. Original cartilage model is almost completely ossified and remaining cartilage is articular cartilage. BONE REMODELING • • • removal of existing bone by osteoclasts and deposition of new bone by osteoblasts occurs in all bones responsible for changes in bone shape, bone repair, adjustment of bone to stress, and calcium ion regulation BONE REPAIR 1. 2. 3. 4. Broken bone causes bleeding and a blood clot forms. Callus forms which is a fibrous network between 2 fragments. Cartilage model forms first then, osteoblasts enter the callus and form cancellous bone this continues for 4-6 weeks after injury. Cancellous bone is slowly remodeled to form compact and cancellous bone. BONE AND CALICUM HOMEOSTASIS • • • • • Bone is a major storage site for calcium Movement of calcium in and out of bone helps determine blood levels of calcium Calcium moves into bone as osteoblasts build new bone Calcium move out of bone as osteoclasts break down bone Calcium homeostasis is maintained by parathyroid hormone (PTH) and calcitonin HEMATOPOIETIC TISSUE BONE GROWTH • • Infancy and youth o long bones lengthen at epiphyseal plate o long bones widen by adding more lamella End of bone growth (in length): o epiphyseal plate is replaced by an epiphyseal line • • • • • tissue that makes blood cells Red marrow - location of blood forming cells Yellow marrow - mostly fat Location of hematopoietic tissue in newborns: o most bones (red marrow) Location of hematopoietic tissue in adults: o red is replaced with yellow marrow o red marrow is mainly in epiphyses of femur and humerus BONE ANATOMY • • • • • • Foramen - hole; Ex. Foramen magnum Fossa - depression; Glenoid fossa Process - projection; Mastoid process Condyle - smooth, rounded end; Ex. Occipital condyle Meatus - canal-like passageway; Ex. External auditory meatus Tubercle: lump of bone; Ex. Greater tubercle o AXIAL SKELETON • • • Skull o Mastoid process - attached to neck muscles o External auditory meatus - ear canal o Nasolacrimal canal - canal between nasal cavity and eye; conducts tears o Styloid process - attachment site for tongue o Mandibular fossa - depression where lower jaw and skull meet o Glenoid fossa - where humerus meets scapula o Hard palate - roof of mouth o Foramen magnum - hole where spinal cord joins brainstem o Zygomatic - cheek bone o Mandible - lower jaw o Maxilla - upper jaw Vertebral Column o 7 cervical vertebra o 12 thoracic vertebra o 5 lumbar vertebra o 1 sacrum o 1 coccyx o Atlas ▪ 1st vertebra ▪ holds head o Axis ▪ 2nd vertebra ▪ rotates head o Functions ▪ Support ▪ Protect spinal cord ▪ Movement Thoracic Cage o Protects vital organs o 12 pair of ribs o Sternum - breastbone o True ribs - attach directly to sternum by cartilage o False ribs - attach indirectly to sternum by cartilage o Floating ribs - not attached to sternum APPENDICULAR SKELETON • • • • Pectoral Girdle o Scapula - shoulder blade o Clavicle - collar bone Upper Limb Bones o Humerus - upper limb o Ulna - forearm o Radius - forearm o Carpals - wrist o Metacarpals - hand Pelvic Girdle o Where lower limbs attach to body o Pelvis - includes pelvic girdle and coccyx o Ischium - inferior and posterior region o Ilium - most superior region o Acetabulum - hip socket (joint) Lower Limb Bones o Femur - thigh o Patella - knee cap o Tibia - large lower leg o Fibula - small lower leg o Tarsals - ankle o Metatarsals - foot Phalanges - toes and fingers ARTICULATIONS • • • • where 2 bones come together (joint) Synarthrosis - nonmovable joint; Ex. skull Amphiarthrosis - slightly movable joint; Ex. Between vertebrae Diarthrosis - freely movable joint; Ex. knee, elbow, wrist TYPES OF MOVEMENT • • • • • • • Flexion - bending Extension - straightening Abduction - movement away from midline Adduction - movement toward the midline Pronation - rotation of the forearm with palms down Supination - rotation of the forearm with palms up Rotation - movement of a structure about the long axis