SKELETAL SYSTEM

• The Musculoskeletal System is composed of bones, cartilages, ligaments and other tissues that perform essential functions in the human body
• Bone tissue, or osseous tissue, is a hard, dense connective tissue that forms most of the adult skeleton

  
• The adult human skeleton is made up of 206 bones

  
• Functions of the skeletal system

  • Protects internal organs
  • Stores and releases fat
  • Produces blood cells
  • Stores and releases minerals
  • Facilitates movement
  • Supports the body
• Classifications of bones by location

  • Axial
  • Appendicular

  
• Classifications of bones by characteristics

  • Long bones
  • Short bones
  • Flat bones
  • Irregular bones
  • Sesamoid bones

  
• Long bones


  Cylinder-like shape, longer than it is wide, for movement and support

  
• Short bones


  Cube-like shape, approximately equal in length, width, and thickness, provide stability and support while allowing for some motion
• Flat bones


  Thin and curved, serve as points of attachment for muscles and protect internal organs

  
• Irregular bones


  Complex shape, protect internal organs, for movement and support

  
• Sesamoid bones


  Small and round, embedded in tendons, protect tendons from excessive forces

  
• Classifications of bones by type of ossification

  • Cartilaginous/Endochondral Ossification
  • Membranous Ossification

  
• Classifications of bones by structure

  • Compact Bone
  • Spongy or Cancellous Bone

  
• Compact Bone


  The denser, stronger of the two types of osseous tissue, makes up the outer cortex of all bones

  
• Osteon (Haversian system)


  • Lamella
  • Central canal (Haversian canal)
  • Perforating canal (Volkmann's canal)
  • Osteocytes
  • Canaliculi
• Spongy (Cancellous) Bone


  Contains osteocytes housed in lacunae, but are not arranged in concentric circles, forms a lattice-like network of matrix spikes called trabeculae

  
• Regions of a long bone

  • Diaphysis
  • Medullary cavity
  • Cortex (cortical bone)
  • Epiphysis
  • Metaphysis
  • Articular cartilage
  • Endosteum
  • Periosteum

  
• Bone Matrix


  Consists of 1/3rd collagen fibers and 2/3rds calcium phosphate salt (hydroxyapatite), hydroxyapatite gives bones their hardness and strength, collagen fibers give a framework for calcification and flexibility

  
• Bone Cells


  • Osteogenic cell
  • Osteoblasts
  • Osteocytes
  • Osteoclasts

  
• Osteoblasts


  Bone formation cells, found in the endosteum and the periosteum, synthesize and secrete the collagen matrix and other proteins

  
• Osteocytes


  Maintain bone tissue, located trapped in lacunae, maintain the mineral concentration of the matrix via the secretion of enzymes

  
• Hormones that influence osteoclasts

  • Growth Hormone
  • Thyroxine
  • Sex hormones
  • Calcitriol
  • Parathyroid hormone
  • Calcitonin
• Pathways in calcium homeostasis

  • 4 pathways

  
• Bone markings


  • Articulation
  • Projection
  • Hole

  
• The axial skeleton forms the central axis of the body and consists of 80 bones, including the skull, vertebral column, and thoracic cage

  
• Bones of the cranium

  • Parietal bones
  • Temporal bones
  • Frontal bone
  • Occipital bone
  • Sphenoid bone
  • Ethmoid bone

  
• Foramen magnum


  • External auditory meatus
• Axial skeleton


  Forms the central axis of the body
• Bones of the axial skeleton

  • Skull
  • Vertebral column
  • Thoracic cage

  
• Skull


  • Bones of the head that supports the face and protects the brain
  • Subdivided into the facial bones and the cranium
  • In the adult, the skull consists of 22 bones

  
• Bones of the cranium

  • Paired parietal and temporal bones
  • Unpaired frontal, occipital, sphenoid, and ethmoid bones

  
• Cranial cavity


  • Almost completely occupied by the brain
  • Base of the skull is a complex area that varies in depth and has numerous openings

  
• Facial bones


  • Maxilla
  • Palatine
  • Zygomatic
  • Nasal
  • Lacrimal
  • Inferior nasal conchae
  • Vomer
  • Mandible

  
• Mandible


  • Forms the lower jaw
  • Each side consists of a horizontal body, ramus with coronoid process and mandibular condyle, angle, and mandibular notch
• Orbit


  • Cone-shaped bony socket that houses the eyeball
  • Contributions from seven skull bones
  • Optic canal, superior orbital fissure
• Bones forming the orbit

  • Frontal
  • Zygomatic
  • Maxilla
  • Palatine
  • Ethmoid
  • Lacrimal
  • Sphenoid

  
• Hyoid bone


  Floating bone not part of the skull, located in the upper neck near the inferior mandible, serves as the base for the tongue, larynx, and pharynx

  
• Vertebral column


  Consists of a sequence of vertebrae, supports the head, neck, and body, protects the spinal cord
• Regions of the vertebral column

  • 7 cervical vertebrae
  • 12 thoracic vertebrae
  • 5 lumbar vertebrae
  • Sacrum
  • Coccyx
• C1 (atlas) and C2 (axis) vertebrae


  C1 articulates superiorly with the occipital condyles and inferiorly with C2