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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