histology bones and blood 

Hyaline Cartilage

• Most common type of cartilage in the body.

• Found in several locations:

  • Trachea: Forms the rings that provide structural support.

  • Ends of Long Bones: Known as articular cartilage, provides a smooth surface for articulation.

  • Costal Cartilage: Located between ribs and sternum.

  • Nasal Septum: Contributes to the structure of the nose.

  • Fetal Skeleton: Forms the initial skeleton during fetal development.

• Lacunae: Small spaces within the cartilage that contain chondrocytes (cartilage cells).

  • Example: Lacunae containing chondrocytes can be seen throughout the hyaline cartilage.

Elastic Cartilage

• Contains elastic fibers, distinct from hyaline cartilage.

• Recognized in specific anatomical locations:

  • External Ear: Provides flexibility and structure, flanked by skin on both sides.

  • Larynx: Part of the voice box, contributing to phonation.

  • Auditory Canal: Assists in sound transmission.

  • Epiglottis: Flap that prevents food from entering the trachea during swallowing.

• High Magnification View:

  • Elastic fibers appear as black lines under magnification.

  • Lacunae with chondrocytes visible in the matrix, similar to hyaline cartilage but with more elasticity.

Fibrocartilage

• Contains a denser population of collagen fibers compared to hyaline and elastic cartilage.

• Characterized by being tougher and more resistant to compressive forces.

• Found in specific structures:

  • Menisci of the Knee: Provides shock absorption and joint stability.

  • Intervertebral Discs: Acts as cushions between vertebrae.

  • Symphysis Pubis: Cartilaginous joint in the pelvis.

• High Magnification:

  • Blue-stained collagen fibers interspersed with chondrocytes seen in lacunae.

Compact Bone

• Forms the outer structure of bones.

• Characterized by Haversian Systems (osteons):

  • These structures resemble a tree trunk when cut across.

  • Haversian Canal: Center of each osteon containing blood vessels.

• Microscopic Anatomy:

  • Dark spots represent lacunae housing osteocytes (bone cells).

  • Lamellae: Concentric rings of calcium deposited by osteocytes, analogous to tree rings.

  • Canaliculi: Microscopic channels (like spokes of a bicycle wheel) through which nutrients travel from blood vessels to osteocytes.

Blood

• Classified as a connective tissue, specifically under special connective tissues.

• Comprised of:

  • Red Blood Cells (Erythrocytes): Majority of the composition, responsible for oxygen transport; appear anucleated.

  • White Blood Cells (Leukocytes): Important for immune response, present in less quantity (approximately 1,000 red blood cells per white blood cell).

  • Platelets (Thrombocytes): Assist in blood clotting, not easily visible at this magnification.

• Composition:

  • Approximately 45% of blood is cellular; of which 94% are red blood cells.

  • Plasma makes up about 55% of blood volume, over 90% of which is water.

  • As red blood cells mature, they lose their nuclei, contributing to their distinctive biconcave shape.

Study Tips

• Revisit the video for clarification and detail.

• Spend time in the lab with microscopes to familiarize with tissue slides and differences.

• Note that every tissue slide may vary, practice is crucial for recognition and identification.