Bone-I (Histology) Slideshow - SCLEROUS TISSUE - Anatomy Lectures - MBBS LecturesBone-I (Histology) Slideshow - SCLEROUS TISSUE - Anatomy Lectures - MBBS Lectures

SCLEROUS TISSUE

Cartilage

Bone

CELLS OF BONE TISSUE

Solidified Matrix / Special / Skeletal Tissue

1- Cartilage

•Chondrous /cartilaginous/non-mineralized tissue

2– Bone

•Osseous/bony/mineralilzed tissue

“Bone is a specialized type of C.T. composed of calcified intercellular material,  bone matrix &  3 cell types”.

Organic component

INORGANIC (MINERAL) COMPONENT (65%)

The association of minerals with collagen fibers is responsible for hardness & resistance of bone

•Main components…….Ca & phosphorus {crystalline most abundant (hydroxyapatite); rod like crystals, non crystalline Ca PO4}

•Substantial quantities of Na, K, Mg, HCO3 & Citrate

•If we remove organic component of bone……

•If we remove inorganic component of bone…….

CELLS OF BONE TISSUE

CELLS OF BONE TISSUE

1.OSTEOPROGENITOR CELLS

•Developed from

•Present in

•Shape

•Nuclei

•Cytoplasm

•Under E/M

Become active during growth and healing of bone.

Can differentiate into Osteoblasts

2. OSTEOBLASTS

ÒDerived from

ÒSpecialized, non-dividing bone-forming cells

ÒSynthesize & secrete organic comp (OSTEOID) & AlkPO4

ÒUnder L/M

ÒUnder E/M

ÒTransforms into

ÒCytoplasmic-

    processes

ÒGap junctions

ÒReceptors for PTH

ÒSecrete a cytokine

ÒOsteoclast stimulating factor

3. OSTEOCYTES

ÒMature bone cells

ÒDerived from

ÒNot capable of mitosis but are long living cells

ÒUnder L/M

ÒUnder E/M

ÒLacunae

ÒCanaliculi

ÒPeriosteocytic space

ÒCytoplasmic processes

ÒGap junctions

ÒMajor functions…..maintenance of bone matrix, & maintenance of adequate Ca level

4. OSTEOCLASTS

ÒDerived from

ÒSpecially meant for resorption of bone matrix

ÒImp for remodelling & renewal of bone

ÒFound where

ÒResorption bays (Howship’s lacunae)

ÒLarge, multinucleated, motile cells

ÒStrongly Acidophilic cytoplasm

ÒRuffled border & Clear zone

ÒSubosteoclastic compartment

ÒSecrete H+ ions, collagenase

  & hydrolytic enzymes

ÒReceptors for calcitonin

Bone resorption by osteoclast

COMPARISON AMONG BONE CELLS

* Osteoblasts secrete the matrix which then hardens by calcification, trapping the differentiating cells now called osteocytes in individual lacunae.

* Osteocytes maintain the calcified matrix and receive nutrients from blood vessels via very small channels through the matrix called canaliculi.

* Osteoclasts are monocyte—derived cells in bone which are important in bone remodeling.

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