Skeleton: constructed of two types of connective tissues: bone and cartilage

• support• protection• system of levers• storage of lipids and many minerals (calcium)• site for hematopoesis (red bone marrow -• blood cell production)

Cartilage (chondro-)

Also called soft Tissue.Present around the bone.Cells:• Chondroblast - actively mitotic cartilage cell• Chondrocyte - mature cartilage cell, in lacunae

Three types of cartilage:• Hyaline• Elastic• Fibrocartilage

Hyaline Cartilage

• most common type of cartilage (gristle)

• matrix = bluish-white if unstained

• very fine fibers (not visible with light microscope)

• contains lacunae (chambers) with chondrocytes (mature cartilage cells)

• locations: articular surface of bones (ends of bones at movable joints), end of nose, fetal skeleton, trachea, costal cartilage

• functions: support and lubrication

Elastic Cartilage

• matrix contains numerous, visible elastic fibers (resilience and flexibility)

• densely clustered lacunae with chondrocytes

• locations: ear pinna, epiglottis, Eustachian tube (auditory tube)

• functions: support and give shape

• Colour : yellowish in color

Fibrocartilage

• collagenous fibers are dominant feature of matrix

• thick compact parallel bundles with wavy appearance

• locations: intervertebral disks, pubic symphasis, knee menisci

• functions: strong compression and tension forces.

• Type of protein present in matrix is chondryomucoprotein.

Bone (osteo-)

• support• protection• movement• mineral storage• hematopoesis (blood cell formation)• contains vesicles, collagen fibers, protein matrix,

organic and inorganic materials• Cells:

– osteoblast, osteocyte, osteoclast

Histology of Bone Tissue

Cells:Osteoblast –it is site for production of mature bone cell

(osteocyte) Osteocyte - mature bone cell, present in lacunaeOsteoclast – related to macrophages, secrete HCl to break

down calcium and phosphorous

• Compact Bone - dense, outer layer, found in diaphysis• Spongy Bone (cancellous bone) - internal, spongy layer,

found in epiphysis

Microscopic Examination of Compact Bone

• functional unit of compact bone = osteon (Haversian system)

• core of osteon = central canal (Haversian canal)• central canal contains blood vessels to supply bone cells• within osteon = osteocytes (mature bone cells) within

lacunae (chambers)• thin tubes called canaliculi run between lacunae and

nearby capillaries• rings called lamellae

Compact Bone - 400x magnification.

Microscopic Examination of Spongy Bone

• honeycomb of small needle-like pieces called trabeculae

• open spaces between trabeculae are filled with red and yellow bone marrow

• each trabecula contains several layers of lamellae and osteocytes in lacunae, but is too small to contain osteons or vessels of its own

Spongy (Cancellous) Bone

The osteocytes are located within chambers (lacunae) inside the trabeculae. Red bone marrow fills the spaces between trabeculae. 100x magnification.