Skeletal System

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Skeletal System - Brief Notes

Bone_functions_ Fractures Injuries
Gross_Anatomy Concept Map of the Skeleton Inflammatory_disorders
Microscopic_Anatomy Axial_Skeleton Developmental_Aspects
Bone_formation_&_growth Appendicular_skeleton Forensic_Anthropology
  Joints_(articulations)  

 

 

 

Bone functions

 

 

         Support

.         Protection

         Storage

         Red blood cell production

         Levers for movement

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Gross Anatomy

 

 

Bone Shapes

 

 

 

 

Structure of a long bone

 

   

 

 

 

Bone markings - Naming Projections and Depressions in Bones

 

 

 

Projections That Help To Form Joints (articulation)
 

Marking Description Example

Head

Bony expansion carried on a narrow neck

 

Femur

Condyle

Rounded articular projection

Condyle of mandible

Facet

Smooth, nearly flat articular surface

 

Facet of ribs

Ramus

Armlike bar of bone

Ramus of mandible

Projections for Muscle & Ligament Attachment

Process

Any bony prominence

 

Trochanter

Very large, blunt, irregularly shaped process

 

Femur

Tuberosity

Large, rounded projection; may be roughened

 

Tibia , ischia

Tubercle

Small, rounded projection or process

Adductor tubercle of femur (distal end)

Crest

Narrow ridge of bone; usually prominent

 

Anterior crest of tibia

Line

Narrow ridge of bone, less prominent than a crest

 

Intertrochanteric line

Spine

Sharp, slender, often pointed projection

Spinous process of vertebra

Epicondyle

Raised area on or above a condyle

 

Medial epicondyle of femur


Depressions And Openings Allowing Blood Vessels And Nerves To Pass

 

Foramen

Round or oval opening through a bone

Foramen magnum

Small foramena maxilla

Meatus

Canal-like passageway

Ext. aud. meatus

Fissure

Narrow, slitlike opening

Inferior orbital fissure

Groove

Furrow

Ramus of Mandible

Sinus

Cavity within a bone, filled with air and lined with mucous membrane

 

Sphenoid sinuses

 


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Microscopic Anatomy

Structure of Compact Bone

 

 

Osteon = Haversian system:  basic unit
    Arranged in lamellae (layers)
     Central blood vessel (Haversian canal)
     Canaliculi - channels for blood vessels
     Osteocytes in lacuna
     Matrix - Calcium and collagen fibers

Types of bone cells
     Osteocyte - mature bone cell; maintenance & repair
     Osteoblast - precursor to osteoblast; convert organic matrix --> bone
     Osteoprogenitor cells (stem cells --> osteoblast --> osteocyte
     Osteoclasts (clast = break) - remove & recycle bone; large cells (30+ nuclei)


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Bone formation & growth

Formation of bony skeleton

 

 

 

 

Intramembranous ossification

 

 

Fibrous membranes bone

 

 

Flat bones (cranium, clavicles)

 

 

 

 

Endochondral ossification

 

 

Hyaline cartilage bone

 

 

All bones below skull (except clavicle)

 

 

 

 

 

Postnatal Bone Growth

 

Growth in Length

 

 

Occurs at epiphyses; continual remodeling

 

 

Complete when epiphysis & diaphysis fuse (~ 18-25 years of age)

 

Width modified throughout life

 

Facial bones (nose, jaw) throughout life

 

 

 

 

 

 

Epiphyseal Growth Plates in a child

1.  Distal femur

2.  Proximal tibia

 

 


Hormonal regulation of skeleton formation

 

 

Infancy/childhood

 

 

 

Growth hormone (anterior pituitary)

 

 

 

Adolescence

 

 

 

 

Sex hormones influence (growth spurt)

 

 

 

Induce epiphyseal closure

 

 

 

 

 

 

Hormonal control of bone remodeling

 

 

Calcitonin stores Ca++ in bone (thyroid)

Parathyroid hormone (PTH) release Ca++ from bone (parathyroid)

 

 

 

 

 

 

 

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Fractures

 

 

Greenstick
One side of shaft breaks, other side bends (common in children)
 
Spiral
Ragged break due to excessive twisting (common sports fracture)
 
Comminuted
Broken into 3 or more pieces
More common in elderly
 
Transverse Break through entire cortex of bone
Compound
Bone pierces skin
 
Compression
Bone is crushed (common in vertebrae with osteoporosis)
 
Depression Bone is pressed inward (skull fracture)
   

 

 

Steps in Normal Fracture Repair

1.  Hematoma forms at site (blood from broken vessels pools; may clot)

2.  Formation of fibrocartilage callus to splint bone pieces (cartilage matrix, bone matrix & collagen fibers)

3.  Callus of bone forms (osteoblasts replace fibrocartilage with spongy bone)

4.  Bone is remodeled (mechanical stress on bone reshapes to permanently mend the break)

 

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Note:  The concept map is missing the 3 bones of the inner ear:  Hammer (malleus); Anvil (incus); Stirrup (stapes)
Sorry about that!

 

 

Axial Skeleton

 

WebAnatomy Skeletons and Skulls Games

Skeletal system tutorials and practice

Cranium

Occipital
Parietal (2)
Temporal (2)
Ethmoid
Sphenoid
Frontal
 

 

Facial bones

Zygomatic (2)
Nasal(2)
Lacrimal (2)
Inferior nasal chonchae (2)
Vomer
Maxilla
Mandible
 

 

 

Hyoid bone

 

 

Vertebral column

 

 

Bony thorax

 

 

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Appendicular Skeleton

WebAnatomy Skeletons and Skulls Games

Skeletal system tutorials and practice

 

 

Shoulder girdle

 

 

Upper limbs

 

 

Pelvic girdle

Lower limbs

 

 

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Joints (articulations)

 

 

Functional classification:  Classified by degree of movement
 

Joint

Movement

Example

Synarthroses

without movement Sutures in skull

Amphiarthroses

slight movement Vertebrae

Diarthroses

freely moveable Limbs
     
Structural classification:  Based on tissue & joint structures present

Joint

Anatomy

Example

Fibrous

bones united by fibrous tissue Sutures of the skull

Cartilaginous

bone ends connected by cartilage Pubic symphysis; intervertebral joints

Synovial

fluid-filled cavity separates bone ends Joints of knee, hip, hand
   

 

General Structure of Synovial Joint
  1. Articular cartilage - hyaline cartilage covers bone ends
  2. Fibrous articular cartilage - joint surfaces enclosed by fibrous capsule lined with synovial membrane
  3. Joint cavity - contains synovial fluid for lubrication
  4. Reinforcing ligaments - capsule reinforce with ligaments

 

 

 

 


 
 

 

Directions of Movement at Synovial Joints    

 

 
 
 

 

 

 

 

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Injuries

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Inflammatory disorders:  Osteoarthritis and Rheumatoid Arthritis
 

 

 

 

Osteoarthritis, commonly related to aging, is a degeneration of the cartilage which cushions the joints.  Loss of cartilage allows friction between the bones, resulting in pain and reduced joint mobility.  Inflammation may also result in stimulation of bone outgrowths (spurs) around the joints. 

   

 

   

 

 

 

Rheumatoid arthritis is an autoimmune disease in which the immune system mistakenly attacks its own tissues.   This chronic disease is characterized by painful inflammation, swelling, and deformation of joints.   

 

 

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Developmental Aspects of Skeleton

 

Osteoporosis - Loss of bone mass with aging may lead to fractures. 

 

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Roll mouse over X-ray to see outline of artificial hip

 

 

 

 

 

 

 

Forensic Anthropology

 

Forensic anthropology - Why study bones?

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