Download Anatomical Location Description

9/13/2013
Anatomical Location Description
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Dorsal = Posterior
Ventral = Anterior
Cranial = Superior
Caudal = Inferior
Medial moves toward the
midline
• Lateral moves away from
the midline
• On the appendicular
skeleton proximal moves
toward the trunk and distal
away from the trunk
Overview of the Skeletal System
• Bones: the majority of the skeleton (begin as
fibrous membranes and cartilage in embryo)
• Skeletal Cartilages: certain areas (nose, parts
of ribs, joints)
• Ligaments: connect bone to bone, reinforce
joint, allow for and restrict movement
• Joints: articulations between bones
– Sites where 2 or more bones meet
– Give mobility and hold skeleton together
Basics of Skeletal Cartilage
• In adults, cartilage remains where flexible
skeletal tissue is needed
• 80% water allows for resilience – springs back
to shape after being compressed
• Avascular and Aneural
• Covered in Perichondrium (dense irregular
connective tissue) that resists expansion when
cartilage is compressed
– Blood vessels deliver nutrients through matrix
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Cartilage Basics Continued
• 3 Types of Skeletal Cartilage
– Hyaline Cartilage
– Elastic Cartilage
– Firbrocartlage
• Chondrocytes are encased in small cavities
called Lacunae within an extracellular matrix
containing jellylike ground substance and
fibers
Hyaline Cartilage
• Most abundant skeletal cartilage
• Support, flexibility, resilience
• Only fiber type is fine collagen (undetectable
microscopically)
• Looks like frosted glass
• Include:
– Articular Cartilages: covers ends of long bones at
moveable joints
– Costal Cartilages: connects ribs to sternum
– Respiratory Cartilages: skeleton of the larynx and
reinforces respiratory passages
– Nasal Cartilages: supports external nose
Elastic Cartilage
• Similar to Hyaline Cartilage, but also contains
elastic fibers
• Stands up to repeated bending
• Found in 2 places:
– External ear
– Epiglottis: flap that covers larynx when we
swallow
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Fibrocartilage
• Highly compressible, have great tensile
strength – thick and dense
• Roughly parallel rows of chondrocytes
alternating with thick collagen fibers
• Places with heavy pressure and stretch
– Menisci: pad like cartilages of the knee
– Intervertebral discs
Growth of Cartilage
• Cartilage has a flexible matrix that can
accommodate mitosis
– Ideal environment to lay down embryonic
skeleton and provide new skeletal growth
• Grows in 2 ways:
– Appositional: growth from outside
– Interstitial: growth from inside
• Typically cartilage growth stops during
adolescence when skeleton stops growing
Appositional Growth of Cartilage
• Growth from outside
• Cells in the perichondrium secrete matrix
against the external surface of the existing
cartilage
– Adds layers externally
– Ends of long bones
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Interstitial Growth of Cartilage
• Growth from the inside
• Lacunae bound chondrocytes within the
cartilage divide and secrete new matrix,
expanding the cartilage from within
– Adds layers internally
– Epiphyseal growth plates, ears, nose
Classifications of Bones: Location
• By Location
– Axial Skeleton: forms the long axis of the body
• Bones of Skull, Vertebral Column, Rib Cage
– Appendicular Skeleton: bones that form the
upper and lower limbs, shoulder and hip
Classifications of Bones: Shape
• By Shape
– Long: longer than wide
• All limb bones except patella, carpals, and tarsals
– Short: cube shaped
• Carpals and tarsals
• Sesamoid: special short bones that form within a
tendon sheath - patella
– Flat: thin, flattened, usually somewhat curved
• Sternum, scapulae, ribs, most skull bones
– Irregular: complicated shapes that don’t fit other
classes
• Vertabrae, hip bones
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Functions of Bone
• Support
– framework for body and cradles soft organs
• Protection
– Bones of skull protect the brain, vertebrae protect
the spinal cord, rib cage protects organs of the
thorax
• Movement
– Provide levers for muscles
Functions of Bone Continued
• Storage
– Mineral and Growth factor Storage
• Reservoir for mineral, esp. calcium and phosphorous
– Rleased into blood as needed
• Mineralized bone matrix stores growth factors
– Triglyceride (fat) storage
• Stored in bone cavities and is a source of stored energy
• Blood Cell Formation
– Hematopoiesis occurs within the marrow cavities
of bones
Bone Vocabulary
• Osteoblasts: bone forming cells
– Secrete bone matrix
• Osteocytes: mature bone cells
– Mineralize bone matrix
• Osteoclasts: large cells that break down
(resorb) bone matrix; “bone chewers”
• Osteoid: unmineralized bone matrix
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Anatomy of Bones: Compact Bone
• Compact Bone: dense outer layer
• Haversian System or Osteon – structural unit
– Lamella: weight-bearing, column-like tubes, mainly
collagen; fibers of each ring run in adjacent directions
to resist twisting forces
• Osteocytes occupy lacunae at junctions of lamellae
• Canaliculi: hairlike canals; connect lacunae to each other
and central canal
– Haversian(Central) Canal: through the core of each
osteon containing small blood vessels and nerve fibers
– Volkmann’s(Perforating) Canals: right angles to the
long axis; connect periosteal nerve and blood supply
to central canal and medullary cavity
Anatomy of Bones: Spongy Bone
• Internal to compact bone
• honeycomb of trableculae (small needle-like flat
pieces) filled with marrow
• Trabeculae contain irregularly arranged lamellae
and osteocytes interconnected by caniculi
• No osteons
Coverings and Linings: Periosteum
• Double layered membrane that covers the
entire bone except the joint surface
• Outer fibrous layer – dense irregular connective tissue
• Inner osteogenic layer – against bone surface
– Osteoblasts, osteoclasts and osteogenic cells (stem
cells)
• Provides anchoring points for ligaments and
tendons
• Richly supplied with nerve fibers, lymphatic
vessels and blood vessels which enter diaphysis
via nutrient foramina
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Coverings and Linings: Endosteum
• Delicate membrane covering the internal
surfaces of bone
• Covers the tribeculae of spongy bone and the
canals that pass through compact bone
• Contains osteoblasts, osteoclasts and
osteogenic cells
Anatomy of a Long Bone
• Diaphysis: tubular shaft forming the long axis of
the bone
– Thick collar of compact bone surrounding a central
medullary (marrow) cavity (yellow marrow)
• Epiphyses: bone ends
– Compact bone exterior, spongy bone interior
– Joint surface of epiphyses covered with hyaline
cartilage
– Epiphyseal line separates epiphyses and diaphysis
• Remnant of epiphyseal plate – hyaline growth plate
Short,Irregular and flat bones
• On outside, thin plates of periosteum covered
compact bone
• On inside, endosteum covered spongy bone
– Contain marrow in the spaces of the tribeculae
– In flat bones spongy bone is called diploë
• Bones are not cylindrical, no shaft or
epiphyses
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Bone Development
• Ossification and ostoegenesis – synonyms
meaning bone formation
• Before week 8, the skeleton of the human
embryo is constructed entirely of fibrous
membranes and hyaline cartilage
• Intramembranous Ossification: bone developing
from fibrous membrane
– Fibrous connective tissue formed by mesenchymal
cells
• Endochondral Ossification: Ossification of the
hyaline cartilage
Intramembranous Ossification
• Results in formation of cranial bones (frontal,
parietal, occipital, temporal) and clavicles
• Stages
1)Ossification centers appear in the fibrous membrane
2)Bone matrix secreted and calcified within membrane
3)Woven bone and periosteum form
- precursor to spongy bone
4)Lamellar bone replaces woven bone, just deep to the
periosteum. Red marrow appears.
Endochondral Ossification
• Uses hyaline cartilage “bones” as patterns for
bone construction
• Most bones develop this way
• Ossification “chases” cartilage formation as
cartilage calcifies, erodes and is replaced by
bone
– Requires breakdown of hyaline cartilage prior to
ossification
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Endochondral Ossification
• Formation of Bone Collar
• Cavitation of Hyaline Cartialge
– Form a hole inside
• Invasion of internal cavity by periosteal bud and
spongy bone formation
• Formation of medullary cavity; appearance of
secondary ossification centers in epiphyses
• Ossification of the epiphyses, with hyaline
cartilage remaining only in the epiphyseal plates
and as articular cartilage
– Growth plates
Postnatal Bone Growth
• During Infancy and youth
• All bones grow in thickness by appositional
growth
• Long bones grow by interstitial growth of the
epiphyseal plate cartilage and its replacement
by bone
– Longitudinal growth ends when the bones of the
epiphysis and diaphysis fuse (epiphyseal closure)
– Around 18 in females, 21 in males
Bone Remodeling
• Every week we recycle 5-7% of our bone mass, yet in
healthy young adults total mass remains constant
• Depostion and Resorption of bone
– Deposits occur where bone is injured or more strength is
required
• Requires protein, vit C, vit D, vit A, minerals (calcium,
phosphorous, magnesium, manganese)
– Resorption occurs in response to systemic Calcium
demands
• Romodeling units
– Adjacent osteoblasts and ostoeclasts deposit and resorb
bone from ondosteal and periosteal surfaces
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Regulation of Remoldeling
• Hormonal mechanism maintains calcium
homeostasis in the blood
– Calcitonin stimulates calcium salt deposit in bone
– PTH (parathyroid hormone) signals osteoclasts to
degrade bone matrix and release calcium
• Mechanical and gravitational forces acting on the
skeleton
– Wolff’s Law: a bone grows or remodels in response to
forces or demands placed upon it
– Trabeculae form along lines of stress
– Large bony projections occur where heavy active
muscles attach
Bone Fracture Classification
• Position of the bone ends after fracture
– Nondisplaced
– Displaced
• Completeness of the break
– Complete
– Incomplete (stess fracture)
• Orientation of the bone along the axis
– Linear – parallel to axis
– Transverse – perpendicular to axis
• Penetration of the skin
– Compound
– simple
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An orientation on the orientation of
the body… Anatomical Position
Planes of Movement
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9/13/2013
Anatomical Location Description
•
•
•
•
•
Dorsal = Posterior
Ventral = Anterior
Cranial = Superior
Caudal = Inferior
Medial moves toward the
midline
• Lateral moves away from
the midline
• On the appendicular
skeleton proximal moves
toward the trunk and distal
away from the trunk
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Body Cavities
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HyalineCartilage
Elastic Cartilage
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Fibrocartilage
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Classifications of Bone
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Anatomy of Bone
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Spongy (Cancellous) Bone
Anatomy of a Long Bone
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Microscopic View of a Long Bone
Ossification of the Cartilage Skeleton
begins at 8 wks Gestation
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Repair of a Fracture
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