BONE Bone is a specialized connective tissue composed of calcified extracellular
material, the bone matrix ; and three major cell types, osteocyte, osteoblast, and osteoclast Bone is lined by layer of
connective tissue containing osteogenic cell: endosteum (internal) and periosteum (external)
A. Bone Function - Provides solid support for the body - Protects vital organs - Harbors
cavities containing bone marrow - Forms a system of levers to maximize forces generated during
skeletal muscle contraction
B. Cells of the Bone 1. Osteoblasts
“osteos”, bone “blaston”, germ
• Mesenchymally-derived
• Polarized cells Function: ➢ Synthesis of organic components of bone matrix
- Type I collagen, proteoglycans, osteonectin, osteocalcin * Osteocalcin: Vitamin K+-dependent polypeptide ➢
Deposition of inorganic components
- Production of enzymes that extract phosphates from
other ions Morphology
• Uninucleated
• When active in matrix synthesis, has a cuboidal to columnar shape with basophilic cytoplasm Located exclusively at
the surfaces of bone matrix, to which are bounded by integrin and cells joined by gap and adherent junction
• When inactive in matrix synthesis, has a flat shape with reduced basophilia
• Derived from: Osteoprogenitor cells
• Resemble epithelial tissue - Very close to each other - Formation of layers - Known to be cuboidal in nature with lots
of ER and Golgi
✓ Stimulated by the PTH (parathyroid hormone) responsible for
signalling osteoblast production ✓ Bone appositional growth
- Matrix components are secreted at the cell surface in
contact with existing bone matrix, producing a layer of unique collagen-rich material, Osteoid, between the osteoblast
and pre-existing bone surface ✓ Mineralization
- Due to osteocalcin – bind to Ca2+ and concentrate it
locally
Ablen, De Jesus, Karunungan, Manoy
Lecture Outline:
I. Cells of Bones
A. Bone Function B. Bone Classification:
- According to shape - According to microscopic observation - According to bone tissue II. Bone Elongation III. Bone
Growth and Repair IV. Joints
V. Cartilage
1.04
HISTOLOGY Bone and Cartilage
,- Due to Matrix Vesicle – released by osteoblast, rich in
Alk Phos and other enzyme that raises local concentration of PO43- - Matrix Vesicles also serve as foci for formation
of
hydroxyapatite (First visible step in calcification)
Figure 1. Mineralization
2. Osteocytes
“osteo”, bone “cytos”, cell
• Osteoblasts enclosed in lacunae between bone matrix layers that is already mineralized
• With long dendritic processes found in canaliculi
Canaliculi has a spider-like appearance and exhibit gap junctions Morphology:
• Almond-shaped/ flat cells
• Uninucleated
• Pale cytoplasm (reduced ER and Golgi apparatus )
• Long cell processes
Function: ➢ Deposits bone matrix ➢ Initiate mineralization ➢ Sensitive detector of stress or fatigue-induced
microdamage in bone and to trigger remedial activity in osteoblast and osteoclast ✓ Death results to the resorption of
matrix ✓ Communicates via gap junction at the end of their processes
3. Osteoclasts
“osteo”, bone “clastos”, broken Morphology
• Large
• motile
• Multinuclear
• Acidophilic cytoplasm
|| 08/28/2017
1
of
1.04
10
, • Ruffled border
• Location: Bone surface
• Derived from: Hemopoietic cells (bone marrow derived) Function: ➢ Bone resorption and remodelling
Ruffled bays In an active osteoclast the membrane domain that contacts the bone forms a circular sealing zone
which binds the cell tightly to the bone matrix and surrounds an area with many surface projections, called the ruffled
border. This circumferential sealing zone allows the formation of a specialized microenvironment between the
osteoclast and the matrix in which bone resorption occur
- Induce acidic nature and secretes a lot of enzymes for
breakdown of collagen and other substances
Figure 2. Cells of the bone
Periosteum and Endosteum
• External and internal connective tissue surface covering of all bones
• Periosteum – outer fibrous layer of dense connective tissue (mostly type I collagen)
• Perforating or Sharpey Fibers – bundle of periosteal collagen that penetrate the bone matrix and bind to periosteum
to the bone
HISTOLOGY
Bone and Cartilage
1.04
Resorption bays - Howships lacunae
Ablen, De Jesus, Karunungan, Manoy
• Endosteum –covers small trabeculae of bony matrix, with sparse delicate matrix of collagen matrix Bone Matrix
• About 50% of the dry weight of bone matrix is inorganic materials.
• Calcium hydroxyapatite is most abundant, but bicarbonate,citrate, magnesium, potassium, and sodium ions are also
found. The surface of hydroxyapatite crystals are hydrated, facilitating the exchange of ions between the mineral and
body fluids.
• organic matter embedded in the calcified matrix is 90% type I collagen, but also includes mostly small proteoglycans
and multiadhesive glycoproteins such as osteonectin.
Bone Classifiction
A. According to Shape 1. Long bones
- slender shaft (diaphysis), 2 heads w/ epiphysis 2. Short bones
- similar length and width 3. Flat bones
- 2 flat plates with plates ( compact bone) and diploe
(cancellous bone) 4. Irregular bones
- no definitive morphology 5. Sesamoid bones
- within substance of tendons
B. According to microscopic examination At the microscopic level both the compact and cancellous bone
typically show to types of organization: 1. Lamellar Bone
material, the bone matrix ; and three major cell types, osteocyte, osteoblast, and osteoclast Bone is lined by layer of
connective tissue containing osteogenic cell: endosteum (internal) and periosteum (external)
A. Bone Function - Provides solid support for the body - Protects vital organs - Harbors
cavities containing bone marrow - Forms a system of levers to maximize forces generated during
skeletal muscle contraction
B. Cells of the Bone 1. Osteoblasts
“osteos”, bone “blaston”, germ
• Mesenchymally-derived
• Polarized cells Function: ➢ Synthesis of organic components of bone matrix
- Type I collagen, proteoglycans, osteonectin, osteocalcin * Osteocalcin: Vitamin K+-dependent polypeptide ➢
Deposition of inorganic components
- Production of enzymes that extract phosphates from
other ions Morphology
• Uninucleated
• When active in matrix synthesis, has a cuboidal to columnar shape with basophilic cytoplasm Located exclusively at
the surfaces of bone matrix, to which are bounded by integrin and cells joined by gap and adherent junction
• When inactive in matrix synthesis, has a flat shape with reduced basophilia
• Derived from: Osteoprogenitor cells
• Resemble epithelial tissue - Very close to each other - Formation of layers - Known to be cuboidal in nature with lots
of ER and Golgi
✓ Stimulated by the PTH (parathyroid hormone) responsible for
signalling osteoblast production ✓ Bone appositional growth
- Matrix components are secreted at the cell surface in
contact with existing bone matrix, producing a layer of unique collagen-rich material, Osteoid, between the osteoblast
and pre-existing bone surface ✓ Mineralization
- Due to osteocalcin – bind to Ca2+ and concentrate it
locally
Ablen, De Jesus, Karunungan, Manoy
Lecture Outline:
I. Cells of Bones
A. Bone Function B. Bone Classification:
- According to shape - According to microscopic observation - According to bone tissue II. Bone Elongation III. Bone
Growth and Repair IV. Joints
V. Cartilage
1.04
HISTOLOGY Bone and Cartilage
,- Due to Matrix Vesicle – released by osteoblast, rich in
Alk Phos and other enzyme that raises local concentration of PO43- - Matrix Vesicles also serve as foci for formation
of
hydroxyapatite (First visible step in calcification)
Figure 1. Mineralization
2. Osteocytes
“osteo”, bone “cytos”, cell
• Osteoblasts enclosed in lacunae between bone matrix layers that is already mineralized
• With long dendritic processes found in canaliculi
Canaliculi has a spider-like appearance and exhibit gap junctions Morphology:
• Almond-shaped/ flat cells
• Uninucleated
• Pale cytoplasm (reduced ER and Golgi apparatus )
• Long cell processes
Function: ➢ Deposits bone matrix ➢ Initiate mineralization ➢ Sensitive detector of stress or fatigue-induced
microdamage in bone and to trigger remedial activity in osteoblast and osteoclast ✓ Death results to the resorption of
matrix ✓ Communicates via gap junction at the end of their processes
3. Osteoclasts
“osteo”, bone “clastos”, broken Morphology
• Large
• motile
• Multinuclear
• Acidophilic cytoplasm
|| 08/28/2017
1
of
1.04
10
, • Ruffled border
• Location: Bone surface
• Derived from: Hemopoietic cells (bone marrow derived) Function: ➢ Bone resorption and remodelling
Ruffled bays In an active osteoclast the membrane domain that contacts the bone forms a circular sealing zone
which binds the cell tightly to the bone matrix and surrounds an area with many surface projections, called the ruffled
border. This circumferential sealing zone allows the formation of a specialized microenvironment between the
osteoclast and the matrix in which bone resorption occur
- Induce acidic nature and secretes a lot of enzymes for
breakdown of collagen and other substances
Figure 2. Cells of the bone
Periosteum and Endosteum
• External and internal connective tissue surface covering of all bones
• Periosteum – outer fibrous layer of dense connective tissue (mostly type I collagen)
• Perforating or Sharpey Fibers – bundle of periosteal collagen that penetrate the bone matrix and bind to periosteum
to the bone
HISTOLOGY
Bone and Cartilage
1.04
Resorption bays - Howships lacunae
Ablen, De Jesus, Karunungan, Manoy
• Endosteum –covers small trabeculae of bony matrix, with sparse delicate matrix of collagen matrix Bone Matrix
• About 50% of the dry weight of bone matrix is inorganic materials.
• Calcium hydroxyapatite is most abundant, but bicarbonate,citrate, magnesium, potassium, and sodium ions are also
found. The surface of hydroxyapatite crystals are hydrated, facilitating the exchange of ions between the mineral and
body fluids.
• organic matter embedded in the calcified matrix is 90% type I collagen, but also includes mostly small proteoglycans
and multiadhesive glycoproteins such as osteonectin.
Bone Classifiction
A. According to Shape 1. Long bones
- slender shaft (diaphysis), 2 heads w/ epiphysis 2. Short bones
- similar length and width 3. Flat bones
- 2 flat plates with plates ( compact bone) and diploe
(cancellous bone) 4. Irregular bones
- no definitive morphology 5. Sesamoid bones
- within substance of tendons
B. According to microscopic examination At the microscopic level both the compact and cancellous bone
typically show to types of organization: 1. Lamellar Bone
