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❧ ❧
The Skeletal SystemChapter 4
FUNCTIONS OF THE SKELETAL SYSTEM
❧ Support o Provides shape
❧ Protection o Internal organs
❧ Movemento Provides structure for
muscle to act upon❧ Storage
o Minerals & fat❧ Blood cell formation
o hematopoiesis
ORGANIZATION OF BONE
❧ 2 different types of tissueo Cortical - denseo Trabecular – spongy
❧ Outer layer always composed of cortical
CLASSIFICATION OF SHAPE
CLASSIFICATION OF BONES
❧ Long bones o Long round shaft made of
cortical boneo Bulbous knobs of
trabecular bone at endso Major bones of arm and
leg
GROSS ANATOMY OF LONG BONE
CLASSIFICATION OF BONES
❧ Short boneso Shaped like a cubeo Mainly trabecular boneo Bones of wrists and
ankles
CLASSIFICATION OF BONES
❧ Flat Boneso Thino Large surface areao Curved to some extent
❧ Structurally:o 2 thing layers of cortical
bone with a layer of trabecular in between
CLASSIFICATION OF BONES
❧ Irregular boneso Do not fit in other
categories o Individualized shapes
MICROSCOPIC ANATOMY OF BONE
❧ Osteon (Haversian System)o Unit of bone
❧ Central (Haversian) Canalo Opening in center of osteono Carries blood vessels &
nerves
❧ Perforating (Volkmann’s) Canalo Canals that run
perpendicular to the central canal
MICROSCOPIC ANATOMY OF BONE
❧ Lacunaeo Cavities containing
bone cells (osteocytes)o Arranged in concentric
rings❧ Lamellae
o Rings around the central canal
o Sites of lucunae ❧ Canaliculi
o Tiny sideways canals
TYPES OF BONE CELLS
❧ Osteocyteso Mature bone cells
❧ Osteoblastso Bone building cells
❧ Osteoclastso Bone destroying cells o Break down bone for remodeling and calcium release
❧ Bone remodeling is a process by both osteoblasts & osteoclasts
BONE FORMATION
❧ In embryos the skeleton is primarily hyaline cartilage
❧ During development cartilage is replaced by bone
❧ Cartilage remains in:o Bridge of noseo Parts of ribso Joints
BONE GROWTH
❧ Ossificationo Process of bone formation
❧ Two phaseso Bone matrix cell covers the hyaline cartilage through
osteoblast activityo Osteoclasts resorb the hyaline cartilage creating a
medullary cavity
BONE GROWTH
❧ Longitudinal growtho At epiphyseal plateso Through adolescence
❧ Circumference growtho Throughout most of life
ADULT BONE
❧ When we ageo Loss of collagen (elasticity)o Increase in bone brittleness
❧ Bone mineral peakso Women: 25-28o Men: 30-35
❧ Women have smaller bones, therefore more problematic
BONE GROWTH
❧ Hypertrophyo Subject to larger (stronger forces)o Increase in density and growth at the site of force o Physically active: denser and stronger o Bone accounts for ≈ 15% of body weight
❧ Atrophy o Subject to reduced forceso Loss of bone mineral and densityo Bedridden peopleo Swimmers o Astronauts
THE AXIAL SKELETON
❧ Designed to provide stability to the core of the bodyo Skullo Vertebral (spinal) columno Thoracic cage
THE SKULL
❧ 22 bones divided into 2 groups:o Cranial
• 8 bones
o Facial• 14 bones
THE CRANIUM
Parietal bone
FACIAL BONES
❧ 2 nasal❧ 2 maxillary❧ 2 zygomatic❧ 2 lacrimal❧ 2 palantines❧ 2 inferior nasal conchae❧ Mandible❧ Vomer
THE SPINE
❧ 33 stacked individual vertebrae
❧ Differ in size and shape ❧ 5 different regions
REGIONS OF THE SPINE
VERTEBRAE
THE THORACIC CAGE (BONY THORACIC)
❧ Ribs❧ Sternum❧ Thoracic vertebrae❧ Work together to form a
protective bony cage❧ Surround the heart and
lungs in thoracic cavity
THE THORACIC CAGE (BONY THORACIC)
THE APPENDICULAR SKELETON
❧ Body’s appendages❧ Upper extremity❧ Lower extremity❧ 126 bones❧ Built for motion
THE SHOULDER COMPLEX
❧ Shoulder girdle ❧ Left & right clavicles❧ Left and right scapula
o Coracoid processo Acromiolclavicular
jointo Sternoclavicular jointo Glenohumeral joint
THE ARM - HUMERUS
THE FOREARM – RADIUS & ULNA
WRIST & HAND
❧ 54 bones (R & L)❧ Carpal (8)❧ Metacarpal (5)❧ Phalanges (14)
o Proximalo Medialo Distal
WRIST & HAND
THE PELVIC GIRDLE
❧ Shelters the reproductive organs, bladder, and large intestines
THE PELVIC GIRDLE
UPPER LEG - FEMUR
❧ Longest and strongest❧ Fits snugly into
acetabulum❧ Neck of femur
o Most vulnerableo Hip fractures
LOWER LEG – TIBIA & FIBULA
❧ Tibiao Shinbone o Bears most weight
❧ Fibula o Serves as site for muscle
attachments
THE ANKLE & FOOT
❧ Foot – acts like a spring that stores and releases energy
❧ Two largest – talus (ankle) and calcaneuso Bear most the weight
JOINTS
❧ Determine the direction of movement of the bones❧ Classified in different ways
o Complexityo Number of axeso Joint structureo Joint function
❧ Three main categories (with regard to function)o Immovableo Slightly moveableo Freely moveable
IMMOVEABLE JOINTS
❧ Synarthroseso “syn” means togethero “arthron” means joint
❧ Absorb shock but permit little to no movement
❧ Two typeso Sutures
• Sutures of the skull
o Syndesmoses • “held by bands”• Tibiofibular joint
SLIGHTLY MOVEABLE JOINTS
❧ Amphiarthroses❧ “amphi”- on both sides❧ Cartilaginous joints – allow more motion❧ Two types
o Synchondroses • Sternocoastal joints, epiphyseal plates
o Symphyses • Pubic symphysis, vertebral joints
FREELY MOVEABLE JOINTS
❧ Diarthroses❧ Also referred to as synovial joints❧ Six different types
o Glidingo Hingeo Pivoto Condyloido Saddleo Ball & socket
SYNOVIAL JOINTS
SYNOVIAL JOINTS
BONE INJURIES
❧ Common fractures
❧ Simple – bone ends remain in the surrounding tissue❧ Compound – one or both ends protrude from the skin❧ Greenstick – incomplete break (more common in children
since their bones are more flexible – due to higher collagen)❧ Comminuted – when the bone is splintered ❧ Impacted – broken ends are forced into each other
(breaking a fall with arms
BONE INJURIES
OSTEOPOROSIS
SPRAINS
ARTHRITIS
LONG BONE IMMOBILIZATION
❧ Long Bone Immobilization Video
❧ https://www.youtube.com/watch?v=Z5K-6q36Hlk
Male vs. Female Skull
Male vs. Female Pelvis