Osseous Tissue &
Skeletal Structure
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Introduction
Classification of Bones
Bone Histology
Bone Development & Growth
The Dynamic Nature of Bone
Surface Features of Bone
Introduction
• Structures:
 Bones & supporting tissues
• Functions of the Skeletal
System:
 Anatomically-related functions
 Physiologically-related functions
Bones of the
Human Body
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Learning Objectives
• Skeletal Elements:
 List general elements of the
skeleton
• Skeletal Function:
 Describe the functions of the
skeletal system
General
Skeletal Elements
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Bones
Ligaments
Cartilage
Membranes &
specialized tissues
associated with joints
Functions of the
Skeletal System
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Skeletal System
Functions
• Support – bones provide the
structural framework for attachment
of soft tissues & organs
• Protection – bones encase many vital
organs
 brain, spinal cord, & special sense
organs
 cardio-pulmonary organs
 digestive organs & urinary organs
 female reproductive organs
Functions of Bone:
Support
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Functions of Bone:
Protection
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Skeletal System
Functions
• Hemopoiesis – stem cells in red
bone marrow produce RBCs,
platelets, & WBCs
• Leverage – bones change
magnitude & direction of forces
generated by skeletal muscles to
allow movement
Functions of Bone:
Blood Production
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Functions of Bone:
Movement
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Skeletal System
Functions
• Storage
 yellow bone marrow of long bone
cavities: lipid reserves
 minerals: Ca2+ & PO43- ions
Classification
Of Bones & Bone Tissue
• Classification:
 Bones may be classified on the
basis of shape
• Osseous Tissue:
 Compact bone (lamellar bone)
 Spongy bone (cancellous bone)
• Specific Bone Terminology
Learning Objectives
• Bone Classification:
 Classify bones according to their
shapes & provide an example of
each type
• Bone Tissues:
 Identify 2 types of bone tissue
• Long & Flat Bone Terminology:
 Identify the regions of a typical
long bone & flat bone
Bone Classification
• Long bones
 long & slender
 arms & legs; hands & feet;
fingers & toes (appendages)
Ex: femur
• Short bones
 boxlike
 wrists & ankles
Ex: talus
Bone Classification
• Flat bones
 thin w/ parallel surfaces
 superior & lateral cranium;
shoulder blades; rib cage; hip bones
Ex: sternum
• Irregular bones
 complex shape
 inferior cranium; vertebrae;
facial bones
Ex: mandible
Bone Classification
• Sesamoid bones
 small, flat; develop w/in tendons
 knee cap; bones at “big” toe joints
Ex: patella
• Sutural bones (a.k.a., WÖrmian
bones)
 small, flat, irregular
 develop w/in sutures of cranial bones
No Example
Bone Terminology
• Long bones:
 epiphyses (proximal & distal)
cortex – compact bone
medullary region – spongy bone
 contains red marrow
 metaphyses (proximal & distal)
 diaphysis – compact bone (cortex)
 marrow cavity – yellow marrow w/in
diaphysis (medullary)
Blood Supply
• Nutrient artery & vein
 supply diaphysis
• Metaphyseal vessels
 supply diaphyseal surface of
epiphyseal plate
• Periosteal vessels
 supply osteons of outer compact
bone w/ branches into spongy bone
of epiphyses
Bone Terminology
• Flat bones:
 external table – compact bone
 diploë – spongy bone
contains red marrow
 internal table – compact bone
Structure of Bone
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Bone Tissue Types
• Compact Bone
 Dense bone
• Spongy Bone
 Open network of struts & plates
Compact Bone:
Structure & Function
• Structure: Lamellar Bone
 Osteon
central (osteonic) canal w/ blood
vessels
osteocytes in lacunae form concentric
layers – concentric lamellae
canaliculi – interconnect lacunae
 Perforating canals – between
osteons
Compact Bone:
Structure & Function
 Interstitial lamellae – between
circular osteons
 Circumferential lamellae –
outer perimeter of bone
• Function: Lamellar Bone
 strength along longitudinal axis of
bone
 resist compression
Spongy Bone:
Structure & Function
• Structure: Cancellous Bone
 trabeculae – struts & plates w/
large spaces
 no blood vessels; diffusion through
canaliculi of surrounding compact
bone
Spongy Bone:
Structure & Function
• Function: Cancellous Bone
 strength from multiple directions
 lightens bone to ease movement
 supports & protects stem cells
forming red bone marrow
Bone Membranes
• Periosteum
 locus – surrounds bone
 functions:
provides route for blood vessels &
nerves
isolates bone from surrounding tissue
participates in bone growth & repair
Periosteum Structure
• Periosteum
(cont)
 2 layers:
outer fibrous layer
collagen fibers
continuous w/ ligaments & tendons
inner cellular layer
osteoblasts
produce perforating fibers
(Sharpey’s fibers) that penetrate
bone matrix
osteogenic potential – can
participate in bone remodeling
Bone Membranes
• Endosteum
 locus – lines marrow cavities of
bones
 function: osteogenic layer
osteoclasts  osteolysis
osteoblasts  osteogenesis
Bone Histology
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Bone Tissue Organization
Bone Matrix
Bone Cells
Compact & Spongy Bone
Periosteum & Endosteum
Learning Objectives
• Bone Tissue:
 Identify 4 features of a
representative sample of bone
tissue
• Bone Matrix:
 Identify the components of the
bone matrix
Learning Objectives
• Bone Cells:
 Identify 4 types of bone cells &
describe the locations & functions
of each
• Compact & Spongy Bone:
 Compare the structures &
functions of compact & spongy
bone
Bone Tissue:
Connective Tissue
canaliculi
• Matrix
central canal of
osteon
 protein fibers – collagen
 ground substance – calcium salts
• Lacunae – pockets in matrix
containing mature bone cells
• Canaliculi – narrow passageways
through matrix that connect lacunae
• Connective tissue membranes surround bones & line inner cavities
matrix
osteocyte in lacuna
Bone Matrix
• Protein component (osteoid)
 collagen fibers
–
1/3 wt.
• Mineral component:
 hydroxyapatite crystals:
Ca10(PO4)6(OH)2
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2/3 wt.
Ca3(PO4)2
form crystal lattice
Ca(OH)2
 imbedded w/in hydroxyapatite
crytals – CaCO3 , Na, K, Mg, F
Bone Cells
• Osteoprogenitor cells
 stem (mesenchymal) cells
 locus – external & internal membranes of
bones
 function – form osteoblasts to repair
bone
• Osteoblasts
 locus – external & internal membranes of
bones
 function – osteogenesis: produce new
bone matrix (osteoid)
Bone Cells
• Osteocytes
 locus – lacunae w/in mature bone matrix
 functions:
 recycle Ca2+ salts in surrounding matrix
 convert to osteoblasts to repair damaged
bone
• Osteoclasts
 locus – external & internal membranes of
bones
 giant cells w/ 50+ nuclei derived from
monocytes
 function – osteolysis: break down bone
matrix
Bone
Formation & Growth
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Calcification -v- Ossification
Intramembranous Ossification
Endochondral Ossification
Blood & Nerve Supply
Learning Objectives
• Ossification:
 Compare the mechanisms of
intramembranous & endochondral
ossification
• Development:
 Discuss the timing of bone
development & growth & account
for differences in the internal
structure of adult bones
Bone Development
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Ossification -vCalcification
• Ossification
 Process by which other tissues are
replaced by bone
• Calcification
 Process of calcium deposition
occurs during ossification (bone
formation)
may also occur in other, non-bony
tissues
Intramembranous
Ossification
• Dermal ossification
 osteoblasts differentiate w/in
mesenchymal or fibrous connective
tissue
 occurs in deep layers of the dermis
 resulting bones called “dermal
bones”
Dermal Bones
• Minority of bones of the body
 Roofing bones of the Cranium
parietals
frontal
occipital
 Mandible
 Clavicles
 Sesamoid bones
patella
Endochondral
Ossification
• Ossification of hyaline cartilage
model
 chondrocytes produce cartilage;
then die as nutrients are cut off by
matrix; spaces through the matrix
are created
 blood vessels grow into spaces in
the cartilage
 osteoblasts differentiate and lay
down bone matrix
Endochondral Bones
• Most of the bones in the body
 Basal bones of the Cranium
sphenoid & ethmoid
temporal
 Facial bones
maxillaries & nasals
zygomatics, palatines, etc
 Vertebrae
 Bones of the appendages
femur, tibia, fibula, tarsals, etc
humerus, radius, ulna, carpals, etc
Ossification
Epiphyseal
Plate
• Increase in bone length
 locus of active growth in
lengthening long bones
• Cartilage is converted to bone
via endochondral ossification
• Under control of hormones:
 growth hormone
 thyroid hormones
 sex hormones
Appositional Bone
Growth
Nervous Supply
• Sensory neurons penetrate
cortex w/ nutrient artery
• Innervate:
 endosteum
 marrow cavity
 epiphyses
• Sensory innervation of bone is
extensive
Bone Remodeling
& Homeostasis
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Effects of Exercise
Hormonal & Nutritional Effects
Bone as a Calcium Reserve
Fracture & Repair
Aging
Learning Objectives
• Remodeling & Homeostasis:
 Describe the remodeling & homeostatic
mechanisms of the skeletal system
• Factors Affecting Skeletal System
Development:
 Discuss the effects of nutrition,
hormones, exercise, & aging the
skeletal system
• Bone Repair:
 Describe the different types of fractures
& explain how they heal
Bone Remodeling
• Recycling:
 Bone organic components – proteins
 Bone mineral component –
hydroxyapatite
• Bone cells:
 osteocytes – continuous remodeling
 osteoclasts & osteoblasts – balanced
activity
• In young adult – 1/5 of skeleton is
demolished & rebuilt each year
Exercise
• Electrical fields are generated by
bone crystals when stressed
• Osteoblasts attracted to these areas
• Osteoblasts induced to produce more
bone matrix
• Effects:
 stronger, thicker bone
 larger tuberosities for larger muscles
Note effects of little exercise or paralysis
Nutrition & Hormones
• Factors affecting bone growth,
development, & maintenance
1) dietary Ca2+ & PO43-; Fe, Fl, Mg,
Mn also required in small amounts
2) calcitriol – hormone synthesized in
kidneys essential for absorption of Ca2+
& PO43-; derived from vitamin D3 (from
skin adipose tissue)
3) vitamin C – required by enzymes
making collagen
Nutrition & Hormones
4) other vitamins
 vitamin A – stimulates osteoblast
activity
 vitamins K & B12 – required by
enzymes making bone proteins
5) hormones
 growth hormone – pituitary
hormone; stimulates protein
synthesis throughout body
 thyroxine – thyroid gland hormone;
stimulates metabolism to produce
ATP energy for synthesis
Nutrition & Hormones
6) sex hormones
 androgens – male sex hormones of
the testes; stimulate higher rate of
osteoblast activity
 estrogens – female sex hormones of
the ovaries; stimulate higher rate of
osteoblast activity
• Parathyroid hormone &
calcitonin – maintain homeostatic
levels of Ca2+ & PO43- in body fluids
Calcium Reserves
Skeletal function – store Ca2+ &
PO43• parathyroid hormone (PTH)
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produced by parathyroid glands
activity:
1) stimulate osteoclast activity
2)  rate of absorption of Ca ions by
intestine
3)  rate of Ca ion excretion from kidney
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result:  [Ca2+] in blood & other body
fluids
Calcium Reserves
Skeletal function – store Ca2+ &
PO43• calcitonin
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produced by thyroid gland
activity:
1) inhibit osteoclast activity
2)  rate of Ca ion excretion from kidney
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result:  [Ca2+] in blood & other body
fluids
Control of Blood
Calcium & Phosphate
Thyroid
Gland
calcitonin
diet
BLOOD
Ca2+/PO43-
OSTEOBLAST Activity
INHIBIT OSTEOCLAST
STIMULATE OSTEOCLAST
fast
Parathyroid
Glands
parathormone
MINERAL
BONE
(HYDROXYAPATITE)
2+
[Ca ]
Increase &
Decrease in Body Fluids
Fracture Repair
• Step 1:
 fracture hematoma - extensive bleeding
followed by blood clot
• Step 2:
 internal callus – network of spongy bone
forms to unite inner surfaces
 external callus – network of cartilage &
bone stabilizes outer edges
Fracture Repair
• Step 3:
 spongy bone brace – unites internal &
external bone surfaces as external
callus cartilage is replaced by bone
 remodeling - bone fragments & dead
bone replaced
• Step 4:
 swelling – at site of fracture
 eventually replaced by remodeling
Injury to Bone & Muscle
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Aging & The Skeletal
System
• Osteopenia
 inadequate ossification during
normal remodeling
 begins age 30-40
 osteoblast activity declines while
osteoclast activity remains normal
 bone loss:
men – 3% / yr
women – 8% / yr
Aging & The Skeletal
System
• Osteoporosis
 caused by osteopenia
 impairment of normal function
 sex hormone influence
men – produce testosterone until late
in life; osteoporosis not a problem
until after 60
women – cease estrogen production in
late 40s early 50s
Surface Features
Of Bone
• Bone Markings
• Skeletal Terminology
Learning Objectives
• Objective Term:
 Identify the major types of bone
markings & explain their functional
significance
Elevations & Projections
• General:
 process – any projection or bump
 ramus – extension of bone forming an
angle
• Tendon & ligament attachments:
 trochanter – large, rough projection
(femur)
 tuberosity – smaller, rough projection
 tubercle – small, rounded projection
 crest – prominent ridge
 line – low ridge
Elevations & Projections
• Articular processes:
 head – expanded, articular end of an
epiphysis; separated from the shaft by a
“neck”
 neck – narrow connection betw/ the
epiphysis & diaphysis
 condyle – smooth, rounded articular
surface
Trochanter; Head; Neck;
Condyle
Tuberosity
Crest; Line
Elevations & Projections
• Articular processes: (cont)
 trochlea – smooth, grooved articular
process; pulley-shaped
 facet – small, flattened articular surface
 spine – pointed process
Trochlea
Facet; Spine
Depressions
 fossa – shallow depression
 sulcus – narrow groove
Fossa; Sulcus
Openings
 foramen (pl. foramina) – shallow, rounded
passageway for blood vessels &/or
nerves
 meatus (or canal) – tube-like passageway
for nerves or blood vessels
 fissure – elongate cleft
 sinus (or antrum) – chamber w/in a bone;
normally filled w/ air
Foramen; Fossa
Meatus
Meatus
Sinus; Fissure
Bone Features
Bones & Cartilage
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