ANAT20006
PRINCIPLES OF HUMAN STRUCTURE
SKELETAL SYSTEM AND BONES
Dr. Varsha Pilbrow
Department of Anatomy & Neuroscience
Room E526
5th Floor, East Wing, Medical Building
Email: vpilbrow@unimelb.edu.au
Phone: 83445775
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References
• Eizenberg, Briggs, et al. 2008, ‘General
Anatomy: Principles and Applications’. Ch
4, pp 25-35
• Anatomedia CD ROM: General Anatomy:
Systems Frames 1-9
• Drake et al. 2010: Gray’s Anatomy for
Students: Ch 1, pp 14-20
Skeletal framework of body
• Subdivided into:
- Axial skeleton (skull,
vertebral column, ribs
& sternum)
- Appendicular skeleton
(limbs and limb girdles)
- Skeletal system
includes:
- Bones
- Cartilage
Eizenberg, Briggs, Barker & Grkovic, An@tomediaTM General Anatomy Imaging
Frame 30. Melbourne, Anatomedia Publishing, 2003, ISBN: 0-734-2691-9
Function of skeletal system
• Supports the body and muscles
• Protects and encloses visceral organs
• Helps in movement
• Blood formation in bone marrow
• Stores minerals and salts like calcium,
phosphorus
• Removes foreign and toxic heavy metals
Types of bones
• Long
– Arm and leg bones
• Short
– Carpal, tarsal bones
• Flat
– Cranial bones, sternum
• Irregular
– Vertebrae, bones of face
• Other
– Pneumatic, sesamoid,
accessory
• 206 bones in adult body
Eizenberg, Briggs, Barker & Grkovic, An@tomediaTM General Anatomy Systems
Frame 3. Melbourne, Anatomedia Publishing, 2003, ISBN: 0-734-2691-9
Bone composition
• Cells
– Osteoblasts
• Bone producing cells
– Osteoclasts
• Bone dissolving cells
• Extracellular matrix
– 2/3rd inorganic
• Mineralised ground substance
– 85% hydroxyapatite (crystallized calcium phosphate)
– 10% calcium carbonate
– other minerals
– 1/3rd organic
• Collagen fibres, protein, carbohydrate molecules
– Combination provides for strength & resilience
• minerals resist compression; collagen resists tension
Structure of a Long Bone
• Periosteum
– Outer fibrous covering
– Articular cartilage at joint
• Compact bone
– 3/4th of weight
• Spongy bone
– 1/4th of weight
– Made up of trabeculae
•
•
•
•
•
•
Diaphysis
Epiphysis
Epiphyseal plate
Nutrient foramen
Endosteum
Medullary cavity
– Red bone marrow
– Yellow bone marrow
Saladin, K 2001, Fig 8.2 Anatomy and Physiology, McGraw Hill, ISBN 0-070290786-X
Structure of a Flat Bone
• External and internal
layer of compact bone
• Middle layer is spongy
bone. No marrow cavity
• Spongy bone called
diploe
• Air-filled bubbles called
trabeculae
• Flat bones life-long
repository of red bone
marrow
Saladin, K 2001, Fig 8.2 Anatomy and Physiology, McGraw Hill, ISBN 0-070290786-X
Properties of bone
•Trabecular bone - good at
resisting static (eg. weight
bearing) forces
•Cortical bone - good at
resisting dynamic (eg.
bending) forces
Tensile
stress lines
Eizenberg, Briggs, Barker & Grkovic, An@tomediaTM
General Anatomy Systems Frame 1. Melbourne,
Anatomedia Publishing, 2003, ISBN: 0-734-2691-9
Compressive
stress lines
Basmajian J, Slonecker C. Grant’s Method of
Anatomy. Williams & Wilkins 1986 ISNN 0-68300374-7, Ch 24 Fig 24.8
Types of cartilage
• Cartilage is precursor for most
bones
• 3 Types of cartilage:
Netter, F.H. Interactive Atlas of Human
Anatomy. 3rd ed. New Jersey, Icon Learning
Systems, 2003, ISBN: 1-929007-15-9, Fig. 8B
– Hyaline
• On articular surfaces
• Parallel collagen fibres
• Glossy appearance
• Model for foetal skeleton
– Fibro
• Forms discs, meniscus, labrum
• Dense, irregular collagen fibres
– Elastic
• Elastic collagen fibres
• External ear, auditory tube, parts of
larynx
Eizenberg, Briggs, Barker & Grkovic, An@tomediaTM General Anatomy Systems
Frame 4. Melbourne, Anatomedia Publishing, 2003, ISBN: 0-734-2691-9
Bone formation: Ossification
• Intramembranous
– Flat bones of skull, clavicle,
mandible
– Fibrous tissue precursor
• Endochondral
– Long bones and most other
bones
– Hyaline cartilage precursor
• Bone first appears between
weeks 6-8 of intrauterine life
12 week foetus
Eizenberg, Briggs, Barker & Grkovic, An@tomediaTM General Anatomy Systems
Frame 5. Melbourne, Anatomedia Publishing, 2003, ISBN: 0-734-2691-9
Intramembranous Ossification
• Produces flat bones of skull &
clavicle
• Steps of the process
– mesenchyme condenses into a
sheet of soft tissue
• transforms into a network of soft
trabeculae
– osteoblasts gather on the
trabeculae to form osteoid tissue
(uncalcified bone)
– osteoclasts remodel the center to
contain marrow spaces &
osteoblasts remodel the surface to
form compact bone
– mesenchyme at the surface gives
rise to periosteum
Saladin, K 2001, Fig 8.2 Anatomy and Physiology, McGraw Hill, ISBN 0-070290786-X
Endochondral ossification - 1°
centres
• Hyaline cartilage model
• Bone first appears in middle of
shaft
• Cartilage progressively replaced
by bone, extending towards the
ends (epiphyses)
• Bone simultaneously formed in
periosteal and endosteal layers,
to remodel the medullary cavity
• Most other bones (eg.
vertebrae) also have primary
centres of ossification and bone
is laid down in a similar manner
Eizenberg, Briggs, Barker & Grkovic, An@tomediaTM General Anatomy Systems
Frame 5. Melbourne, Anatomedia Publishing, 2003, ISBN: 0-734-2691-9
Role of Nutrient artery
- Major artery supplying long bone
- Enters nutrient foramen
- Invades the primary centre
- Brings osteogenic cells
- bone forming cells are
osteoblasts
- bone remodelling cells are
osteoclasts
- Canal of nutrient foramen
directed away from growing end
Eizenberg, Briggs, Barker & Grkovic, An@tomediaTM General Anatomy Systems
Frame 6. Melbourne, Anatomedia Publishing, 2003, ISBN: 0-734-2691-9
Parts of a developing long bone
• Diaphysis (‘between growth’)
forms the shaft
• Epiphysis (‘upon growth’)
forms the ends
• Metaphysis (‘beyond growth’)
forms part of diaphysis
adjacent to epiphysis at each
end
– Site of remodeling and high
metabolic activity.
• Ephiphyseal growth plate b/w
metaphysis and epiphysis
Eizenberg, Briggs, Barker & Grkovic, An@tomediaTM General Anatomy Systems
Frame 6. Melbourne, Anatomedia Publishing, 2003, ISBN: 0-734-2691-9
Ossification – secondary centres
• Secondary centres of ossification
generally appear at epiphyses
• Epiphyseal arteries and
osteogenic cells invade epiphysis
• Deposit osteoblasts, erode
cartilage
• Both ends of long bones, but one
end of digits, ribs
- ‘Pressure’ epiphyses associated
with joints
- ‘Traction’ epiphyses associated
with attachments of tendons or
ligaments
- Distal femur & proximal tibia have
medico-legal significance
Eizenberg, Briggs, Barker & Grkovic, An@tomediaTM General Anatomy Systems
Frame 7. Melbourne, Anatomedia Publishing, 2003, ISBN: 0-734-2691-9
Epiphyseal growth plate (disk)
• Continued longitudinal growth
occurs at epiphyseal growth
plate
• Cartilage cells on the epiphyseal
surface progressively mature
and die to be replaced by bone
at the metaphyseal surface
• When fully developed the only
remaining cartilage is articular
cartilage at the ends of the bone
Ham A. Histology Lippincott 7th ed. 1969 ISBN 0-39752062-X CH 15, Fig 15-27
Epiphyses
•Epiphyses have great
clinical significance:
- indicate a bone is still
growing
- if damaged may
interrupt growth at site
- may be confused
with a fracture
-provide good
indication of skeletal
age in a forensic
situation
•Epiphysial line remnant in
adult long bone
Author own
Author own
Achondroplastic Dwarfism
• Long bones of the limbs
stop growing but other
bones unaffected
• Spontaneous mutation in
DNA
– mutant allele is
dominant
• Chondrocytes in
metaphysis fail to
multiply and enlarge
Saladin, K 2001, Anatomy and Physiology, p. 244 McGraw Hill, ISBN 0-070290786-X
Neurovascular supply of bone
• 4 types of arteries supply a long bone:
– Nutrient (providing osteoblasts to initiate
ossification at the primary centre)
– Periosteal
– Metaphyseal
– Epiphyseal
• Concept of ‘end arteries’ & ‘anastomoses’.
• End arteries are of clinical significance.
Obstruction may lead to death (necrosis)
of the tissue they supply
• Bone receives abundant sensory and
pain nerve fibres
• Lymph vessels accompany blood
Basmajian J, Slonecker C. Grant’s Method of
vessels
Anatomy. Williams & Wilkins 1986 ISNN 0-68300374-7, Ch 1 Fig 1.5
Fractures
Bone is susceptible to fracture:
- may be associated with tearing
& stripping of periosteum,
especially with displacement of
broken ends
- common in children
(greenstick) and in adults (due
to osteoporosis)
Eizenberg, Briggs, Barker & Grkovic, An@tomediaTM General Anatomy Systems
Clinical Ciba: Injuries to the wrist, 1970 Ciba Corporation, Plate VI Frame 9. Melbourne, Anatomedia Publishing, 2003, ISBN: 0-734-2691-9
Aufderheide & Rodriguez-Martin Human Paleopathology, 2006. Cambridge
University Press ISBN 0-521-55203-6
Age & disuse – effects on bone
Bony
outgrowths osteophytes
Compression fractures
common in vertebrae
Author own
Ectopic sites of bone formation &
bone pathology
• Bone may form in other
tissues, eg. viscera,
muscle
Bone may undergo
major reorganisation
Images courtesy of Harry Brookes Allen Museum
University of Melbourne