6. 6
Functions of Bone, cont.
Mineral storage
& homeostasis
Produces blood
cells in red
bone marrow
(hemopoiesis
aka
hematopoiesis)
Energy storage
in yellow bone
marrow
42. Flat bone
of skull
Mandible
Blood capillary
Ossification
center
Mesenchyme
Osteoblast
Collagen fiber
Development of ossification
center: osteoblasts secrete
organic extracellular matrix
1
Osteocyte in
lacuna
Calcification: calcium and
other mineral salts are
deposited and extracellular
matrix calcifies (hardens)
2
Canaliculus
Osteoblast
Newly calcified
bone extracellular
matrix
Mesenchyme
condenses
Formation of trabeculae:
extracellular matrix develops
into trabeculae that fuse to
form spongy bone
3
Blood vessel
Spongy bone
trabeculae
Osteoblast
Periosteum
Compact bone
tissue
Spongy bone
tissue
Compact bone
tissue
Development of the
periosteum: mesenchyme
at the periphery of the
bone develops into the
periosteum
4
50. 50
6. Formation of
Articular Cartilage
& Epiphyseal Plate
Epiphyseal cartilage does
not ossify
Remains as articular
cartilage
Epiphyseal (Growth) plate
also remains as cartilage
Source of interstitial
growth
51. Development of
cartilage model:
mesenchymal
cells develop into
chondroblasts,
which form the
cartilage model.
1
Proximal
epiphysis
Diaphysis
Distal
epiphysis
Hyaline
cartilage
Perichondrium
Endochondral Ossification - Overview
Growth of cartilage
model: growth
occurs by cell
division of
chondrocytes.
2
Uncalcified
extracellular
matrix
Calcified
extracellular
matrix
Nutrient
artery
Periosteum
Primary
ossification
center
Spongy bone
Development of
primary ossification
center: in this region of
the diaphysis, bone
tissue replaces most of
the cartilage.
3
52. Uncalcified
extracellular
matrix
Development of the
medullary (marrow)
cavity: bone
breakdown by
osteoclasts forms
the medullary
cavity.
4
Calcified
extracellular
matrix
Periosteum
Medullary
cavity
Nutrient
artery and
vein
Development of
secondary ossification
centers: these occur
in the epiphyses of
the bone.
5
Secondary
ossification
center
Uncalcified
extracellular
matrix
Epiphyseal
artery and
vein
Articular
cartilage
Spongy bone
Epiphyseal
plate
Formation of articular
cartilage and epiphyseal
plate: both structures
consist of hyaline
cartilage.
6
Endochondral Ossification – Overview, cont.
53. (b) Twelve-week fetus. The red areas represent
bones that are forming (calcified). Clear areas
represent cartilage (uncalcified).
55. 55
4 Zones of
Epiphyseal Plate
Zone of Resting
Cartilage
Zone of Proliferating
Cartilage
Zone of Hypertrophic
Cartilage
Zone of Calcified
Cartilage
56. Epiphysis
(c) Lengthwise growth of bone at epiphyseal plate
EPIPHYSEAL (GROWTH)
PLATE:
Zone of resting cartilage
Zone of proliferating cartilage
Zone of hypertrophic cartilage
Zone of calcified
cartilage
Diaphysis
Articular cartilage
New chondrocytes are
formed
Old chondrocytes are
replaced by bone
New
diaphysi
s
62. Ridges in periosteum
create groove for
periosteal blood vessel.
1
Periosteal ridges
Periosteum
Periosteal blood
vessel
Perforating canal
Groove
Periosteal ridges fuse, forming an
endosteum-lined tunnel.
2
Endosteum
Tunnel
Osteoblasts in endosteum
build new concentric
lamellae inward toward
center of tunnel, forming
a new osteon.
3
Endosteum
Bone grows outward as osteoblasts in
periosteum build new circumferential
lamellae. Osteon formation repeats as new
periosteal ridges fold over blood vessels.
4
Circumferential
lamellae
Periosteum
New osteon
Central
(haversian)
canal
63. Ridges in periosteum create groove for
periosteal blood vessel.
1
Periosteal ridges
Periosteum
Periosteal blood
vessel
Perforating canal
Groove
65. Osteoblasts in endosteum build new
concentric lamellae inward toward center of
tunnel, forming a new osteon.
3
Endosteum
66. Bone grows outward as osteoblasts in
periosteum build new circumferential
lamellae. Osteon formation repeats as
new periosteal ridges fold over blood
vessels.
4
Circumferential
lamellae
Periosteum
New osteon
Central
(haversian)
canal
88. STIMULUS
CONTROLLED CONDITION
Blood calcium (Ca2+) level
RECEPTORS
CONTROL CENTER
Parathyroid hormone gene
EFFECTORS
RESPONSE
Increase in blood
Ca2+ level
Osteoclasts
increase
bone
resorption
Kidneys retain Ca2+ in
blood, excrete
phosphate in urine,
and produce calcitriol
Parathyroid
gland cells
Return to
homeostasis
when response
brings blood Ca2+
level back to
normal
Disrupts homeostasis
by decreasing
Detect lowered Ca2+
concentration which increases
production of cyclic AMP
Input
Output Gene “turned on” which
increases release of PTH
Osteoclasts Kidneys
