http://images5.fanpop.com/image/photos/26500000/-skeleton-dance-skeletons-26529088-725-544.png
Skeletal Cartilages
• Contain no blood vessels or nerves
• Perichondrium (dense irregular connective
tissue girdle) contains blood vessels for
nutrient delivery to cartilage
• Types
– Hyaline
– Elastic
– Fibrocartilage
Cartilage in
external ear
Cartilage in
Intervertebral
disc
Cartilages in
nose
Articular
Cartilage
of a joint
Epiglottis
Thyroid
cartilage
Cricoid
cartilage
Larynx
Trachea
Lung
Costal
cartilage
Respiratory tube cartilages
in neck and thorax
Pubic
symphysis
Meniscus
(padlike
cartilage in
knee
joint)
Articular
cartilage
of a joint
Bones of skeleton
Axial skeleton
Appendicular skeleton
Cartilages
Hyaline cartilages
Elastic cartilages
Fibrocartilages
Figure 6.1
Growth of Cartilage
• Appositional
– Cells secrete matrix against the
external face of existing cartilage
• Interstitial
– Chondrocytes divide and secrete
new matrix, expanding cartilage
from within
http://www.vetmed.vt.edu/education/curriculum
/vm8054/labs/Lab7/IMAGES/elastic%20cartilage%
20WITH%20LABEL%20copy.jpg
Cartilage in
external ear
Cartilage in
Intervertebral
disc
Cartilages in
nose
Articular
Cartilage
of a joint
Bones of the
Skeleton
Costal
cartilage
Pubic
symphysis
Meniscus
(padlike
cartilage in
knee
joint)
Articular
cartilage
of a joint
Figure 6.1
Classification of Bones by Shape
• Long bones
• Short bones
• Flat bones
• Irregular bones
Functions of Bones
•
•
•
•
Support
Protection
Movement
Mineral & Growth Factor
Storage
• Blood cell formation
• Triglyceride storage
• Hormone Production
Bone Structure
• Bones are organs!
– Multiple tissue types
• Bone (osseous) tissue, nervous tissue, cartilage,
fibrous connective tissue, muscle and epithelial
cells (in its blood vessels)
Bone Texture
• Compact
– Dense outer layer; smooth
and solid
• Spongy (trabecular)
– Honeycomb of flat pieces of
bone (trabeculae) deep to
compact
– Space b/w trabeculae filled
with red or yellow bone
marrow
Structure of Short, Irregular, and Flat
Bones
• Periosteum covered
compact bone on the
outside
• Endosteum covered
spongy bone within
– diploë
• Bone marrow b/w the
trabeculae
• Hyaline cartilage on
articular surfaces
Structure of Typical Long Bone
• Diaphysis
– Tubular shaft forms long axis
– Compact bone surrounds medullary cavity
• Epiphyses (bone ends)
– Compact bone outside; spongy bone inside
– Articular cartilage covers articular surfaces
• Epiphyseal line
– b/w diaphysis and epiphysis
– Remnant of epiphyseal plate
Membranes of Bone
• Periosteum
– Outer fibrous layer
– Inner osteogenic layer
– Contains nerve fibers, nutrient blood
vessels, and lymphatic vessels that enter
the bone via nutrient foramina
– Secured to underlying bone by Sharpey’s
fibers
Membranes of Bone
• Endosteum
– Delicate membrane on
internal surfaces of
bone
– Contains osteogenic
cells
Hematopoietic Tissue (Red Marrow)
• Infants (long bones)
– Medullary cavities and
spongy bone
• Adults (long bones)
– Little red marrow
• Red marrow in flat and
some irregular bones is
most active
http://www.gla.ac.uk/ibls/US/fab/images/generic/bocompac.jpg
Bone Markings
• Projections, depressions, and holes
– Sites of attachment for muscles, ligaments, and
tendons
– Joint surfaces
– Passageways for blood vessels and nerves
Bone Markings: Projections
• Sites of muscle and
ligament attachment
– Tuberosity
– Crest
– Trochanter
– Line
– Tubercle
– Epicondyle
– Spine
– Process
• Projections that help to
form joints
– Head
– Facet
– Condyle
– Ramus
Bone Markings: Depressions and
Openings
• Passages for blood vessels and nerves
– Meatus
– Sinus
– Fossa
– Groove
– Fissure
– Foramen
Microscopic Anatomy of Bone
Microscopic Anatomy of Bone:
Compact Bone
• Haversian system
(or osteon)
– Lamellae
– Central
(Haversian) canal
Microscopic Anatomy of Bone:
Compact Bone
• Perforating (Volkmann’s) canals
• Lacunae
• Canaliculi
Microscopic Anatomy of Bone: Spongy Bone
• Trabeculae
– Align along lines of stress
– No osteons
– Irregularly arranged lamellae, osteocytes, and
canaliculi
– Capillaries in endosteum supply nutrients
Chemical Composition of Bone
• Organic
– Bone cells
– Osteoid—organic bone matrix secreted by
osteoblasts
• Ground substance, collagen fibers
• Inorganic
– Hydroxyapatites (mineral salts)
• 65% of bone by mass
• Mainly calcium phosphate crystals
Bone Development
• Ossification (osteogenesis): process of bone
tissue formation
– Formation of bony skeleton
• Begins in 2nd month of development
– Postnatal bone growth
• Until early adulthood
– Bone remodeling and repair
• Lifelong
Types of Ossification
• Endochondral ossification
– Bone forms by replacing hyaline cartilage
– Majority of skeleton
• Intramembranous ossification
– Bone develops from fibrous membrane
– Bones called membrane bones
– Forms flat bones, e.g. clavicles and cranial bones
Endochondral Ossification
• Forms most all bones inferior to base of skull
(except clavicles)
• Begins late in 2nd month of development
• Uses hyaline cartilage models
• Hyaline cartilage must be broken down before
ossification
Month 3
Week 9
Birth
Childhood to
adolescence
Articular
cartilage
Secondary
ossification
center
Epiphyseal
blood vessel
Area of
deteriorating
cartilage matrix
Hyaline
cartilage
1
2
Epiphyseal
plate
cartilage
Medullary
cavity
Spongy
bone
formation
Bone
collar
Primary
ossification
center
Spongy
bone
Blood
vessel of
periosteal
bud
3
4
5
Figure 6.9
Intramembranous Ossification
• Forms cranial bones of the skull and clavicles
• Begins within fibrous connective tissue membranes
formed by mesenchymal cells
• Ossification centers appear
• Osteoid is secreted
• Woven bone and periosteum form
• Lamellar bone replaces woven bone & red marrow
appears
Osteoblast
Mesenchymal
cell
Osteoid
Collagen fibril
Ossification
center
Osteocyte
Newly
calcified
bone matrix
Osteoid
Osteoblast
1 Ossification centers appear in the fibrous
connective tissue membrane.
2 Osteoid is secreted within the fibrous membrane and
calcifies.
Fibrous
periosteum
Mesenchyme
condensing
to form the
periosteum
Osteoblast
Plate of
compact bone
Trabeculae of
woven bone
Blood vessel
3 Woven bone and periosteum form.
Diploë
(spongy bone)
cavities
contain red
marrow
4 Lamellar bone replaces woven bone, just deep to the
periosteum. Red marrow appears.
Figure 6.9 Intramembranous ossification.
Postnatal Bone Growth
• Interstitial growth:
–  length of long bones
• Appositional growth:
–  thickness and remodeling of all bones by
osteoblasts and osteoclasts on bone surfaces
Interstitial (Longitudinal) Growth
• Epiphyseal plate cartilage organizes into 5
important functional zones:
– Resting (quiescent) zone
– Proliferation (growth)
– Hypertrophic
– Calcification
– Ossification (osteogenic)
Resting zone
Proliferation zone
Cartilage cells undergo
mitosis.
1
Hypertrophic zone
Older cartilage cells
enlarge.
2
Calcified cartilage
spicule
Osteoblast depositing
bone matrix
Osseous tissue
(bone) covering
cartilage spicules
Calcification zone
Matrix becomes calcified;
cartilage cells die; matrix
begins deteriorating.
3
4 Ossification zone
New bone formation is
occurring.
Figure 6.10
Appositional Growth
• Growth in Width
– Osteoblasts active in periosteum
– Osteoclasts active in the endosteum
– Building > Breaking down = thicker stronger bone
Bone growth
Cartilage
grows here.
Bone remodeling
Articular cartilage
Epiphyseal plate
Cartilage
is replaced
by bone here.
Cartilage
grows here.
Cartilage
is replaced
by bone here.
Bone is
resorbed here.
Bone is added
by appositional
growth here.
Bone is
resorbed here.
Figure 6.11
Hormonal Regulation of Bone Growth
• Growth hormone
• Thyroid hormone
• Testosterone and
Estrogen
http://2.bp.blogspot.com/-FrC7iCwLqDk/Tb8hrWvYXnI/AAAAAAAAOOg/il4zBWZI5Q/s1600/2008_01_17_pb%252520kids%252520growth.jpg
Bone Remodeling
• Bone is constantly being “recycled”
• Occurs @ surface of periosteum and
endosteum
• Deposit
– Injury or needed strength, requires good diet
– Osteoid seam and Calcification front
• Resorption
– Osteoclasts secrete: lysosomal enzymes, acids
– Dissolved matrix is transcytosed
Control of Remodeling
• What controls continual
remodeling of bone?
– Hormonal mechanisms
that maintain calcium
homeostasis in the blood
– Mechanical and
gravitational forces
http://tutor4physics.com/workliftbox.gif
Hormonal Control of Blood Ca2+
• Most calcium in the body is in the bones
• Less that 1.5g in blood – tightly regulated
narrow range
• Calcium is necessary for
– Transmission of nerve impulses
– Muscle contraction
– Blood coagulation
– Secretion by glands and nerve cells
– Cell division
Calcium homeostasis of blood: 9–11 mg/100 ml
BALANCE
BALANCE
Stimulus
Falling blood
Ca2+ levels
Thyroid
gland
Osteoclasts
degrade bone
matrix and
release Ca2+
into blood.
Parathyroid
glands
PTH
Parathyroid
glands release
parathyroid
hormone (PTH).
Figure 6.12
Hormonal Control of Blood Ca2+
• May be affected to a lesser extent by calcitonin
 Blood Ca2+ levels

Parafollicular cells of thyroid release calcitonin

Osteoblasts deposit calcium salts

 Blood Ca2+ levels
Response to Mechanical Stress
• Wolff’s law: A bone
grows or remodels in
response to forces or
demands placed upon
it
Hormones and Mechanical Stress
• Hormones –
– when remodeling occurs
– As a response to what???
• Mechanical Stress
– Where the remodeling occurs
Classification of Bone Fractures
•
Bone fractures may be classified by four
“either/or” classifications
1. Position of bone ends after fracture:
•
Nondisplaced or Displaced
2. Completeness of the break
•
Complete or Incomplete
3. Orientation of the break to the long axis of the bone:
•
Linear or transverse
4. Whether or not the bone ends penetrate the skin
•
Compound (open) or Simple (closed)
Common Types of Fractures
• In addition to the previous
classification, all fractures
can be described in terms
of
– Location
– External appearance
– Nature of the break
http://www.schultzlegalgroup.com/images/Bone-FractureInjury-Lawyer.jpg
Table 6.2
Table 6.2
Table 6.2
Fracture Healing
1. Hematoma forms
2. Fibrocartilaginous
callus forms
Fracture Healing
3. Bony callus formation
4. Bone remodeling
Homeostatic Imbalances
• Osteomalacia and Rickets
– Calcium salts not deposited
– Rickets (childhood disease)
causes bowed legs and other
bone deformities
– Cause: vitamin D deficiency
or insufficient dietary
calcium
http://upload.wikimedia.org/wikipedia/commons/thumb/a/a9/Xray
RicketsLegssmall.jpg/230px-XrayRicketsLegssmall.jpg
Homeostatic Imbalances
• Osteoporosis
– Loss of bone mass
– Spongy bone of spine
and neck of femur
become most
susceptible to fracture
– Risk factors
• Lack of estrogen, calcium
or vitamin D; petite body
form; immobility; low
levels of TSH; diabetes
mellitus; smoking
Developmental Aspects of Bones
• Embryonic skeleton
ossifies predictably so
fetal age easily
determined from X rays
or sonograms
• At birth, most long
bones are well ossified
(except epiphyses)
Developmental Aspects of Bones
• Nearly all bones completely ossified by age 25
• Bone mass decreases with age beginning in
4th decade
• Rate of loss determined by genetics and
environmental factors
• In old age, bone resorption predominates