Biology Chapter on Calcium Phosphate Deposition

Cartilage Calcification and Transformation

• Calcium phosphate and calcium carbonate granules deposit in intercellular substances, initially near cells and later in the matrix.
• Calcification of intercellular matrix leads to cell death due to lack of nutrient diffusion.
• Transformation of cartilage can result in an asbestos-like consistency with densely packed, non-collagenous fibers, causing matrix softening or cavity formation.

Regeneration and Autografts

• Cartilage regeneration is slow, primarily involving the activity of perichondrium, essential for healing after injury.
• Autografts containing living cells can survive if adequately nourished; homografts involve similar principles of survival.

Articular Hyaline Cartilage

• Present between articulating surfaces, lacking a perichondrium where bones make contact.
• Chondrocytes, larger and centrally located, form cell families within an avascular matrix that is nourished by synovial fluid and nearby blood vessels.

Fetal Hyaline Cartilage

• Found throughout the fetal skeletal system, except in flat bones of the skull and face.
• Initially forms the skeleton from hyaline cartilage, supported by a fetal perichondrium containing numerous blood vessels and active cell division.

Fibrocartilage Structure

• Chondrocytes are dispersed singularly, in pairs, or in rows among type I collagen fibers.
• Matrix is scanty, thin, and basophilic around lacunae; blood supply comes from surrounding tissues.

Intervertebral Discs Composition

• Comprised mainly of fibrocartilage connecting the vertebrae, featuring a central gelatinous nucleus pulposus, a remnant of the embryonic notochord.
• The annulus fibrosus surrounds the nucleus, composed of concentric collagen lamellae.
• Herniation of the nucleus pulposus can cause severe pain and neurological symptoms.

Appositional Growth of Cartilage

• New cartilage layers form at the periphery from the inner chondrogenetic layer of the perichondrium, leading to increased width and cell hypertrophy.

Bone and Ossification Overview

• Bone is a rigid form of connective tissue made of cells, fibers, and a calcified extracellular matrix rich in hydroxyapatite (Ca10[PO4]6[OH]2).
• Provides internal support, protects vital organs, serves as a muscle lever system, stores minerals like calcium and phosphorus, and is involved in blood formation (hematopoiesis).

Macroscopic Structure of Bones

• Two forms of bone: cancellous (or spongy) bone, which has a lattice structure with marrow spaces, and compact bone, which appears solid until viewed microscopically.
• Long bones, like the humerus and femur, feature a thick-walled diaphysis housing a medullary cavity filled with bone marrow.

Ossification Processes

• Periosteal ossification adds layers of calcified matrix, initially forming spongy bone, which matures into compact bone.
• Intracartilaginous (endochondral) ossification involves replacing cartilage models with bone, critical for long bone development, primarily in the skeletal system.

Stages of Endochondral Ossification

• Fetal Hyaline Cartilage Formation: Begins with a mesenchymal template shaped like future bone; active cell division in perichondrium.
• Ossification Centers Appearance: In long bones, three centers typically form, including one in the shaft (diaphysis) and one in each epiphysis.
• Periosteal Band Formation: Activation of osteogenic cells in perichondrium leads to bone collar formation around the shaft.

Primary Bone Destruction and Medullary Cavity Formation

• Osteoclasts, which arise from periosteal or osteogenic buds, begin to absorb primary bone, forming a central medullary cavity lined with endosteum, containing hemopoietic elements.

Periosteal Ossification and Haversian System Formation

• Osteoblasts deposit concentric bony tissue beneath the periosteum, leading to increased bone width while osteoclasts remodel structure.
• Formation of Haversian canals and systems within compact bone, and interstitial lamellae between these structures contribute to the mature architecture of bones, facilitating blood vessel passage.

Explore the process of calcium phosphate and calcium carbonate deposition in intercellular substances within biological systems. This quiz covers transformations such as asbestos-like consistency in cartilage, implications for nutrient diffusion, and cellular viability. Test your understanding of these important biochemical processes.