Bone Structure and Function

Study Notes

Osteon, or Haversian System, is the structural unit of compact bone.
Lamellae are concentric rings of bone matrix.
Haversian canals contain networks of blood vessels and nerves, allowing communication within compact bone.
Volkmann canals connect Haversian canals, facilitating nutrient exchange between osteons.
Osteoclasts reabsorb old bone tissue, playing a crucial role in bone remodeling.
Osteoblasts are responsible for the formation and mineralization of bone.
Osteogenic cells are actively dividing stem cells in bone that differentiate into osteoblasts.
Osteoid is the unmineralized bone matrix composed primarily of proteoglycans, glycoproteins, and collagen.
Lacunae are small cavities in bone that house osteocytes, which become inactive when trapped in these spaces.
Canaliculi are hairlike canals that link lacunae and connect them to the central Haversian canal.

Chondrocytes are the cells that comprise cartilage.
Hyaline cartilage is the most prevalent type, reducing friction in joints and allowing bone growth at epiphyseal plates.
Elastic cartilage offers high flexibility and is found in structures like the external ear.
Fibrous cartilage limits movement and resists compressive forces, notably in the vertebral discs of the spine.
Cartilage is a connective tissue made of chondrocytes that secrete an extracellular matrix (EM) called chondrin, containing collagen and proteoglycans.
Lacks nerves and blood supply, receiving nutrients via diffusion, important for maintaining cartilage health.

Endochondral ossification converts hyaline cartilage into bone during fetal development, initially forming the skeleton.
Ligaments connect bone to bone, providing stability to joints.
Tendons attach muscles to bones, facilitating movement.
Connective tissue develops from the mesoderm and supports or protects various body structures.
Muscle tissue originates from the mesoderm and is responsible for both voluntary and involuntary movements.
Nervous tissue arises from the ectoderm and is essential for transmitting electrical signals in response to stimuli.
Epithelial tissue, derived from all three germ layers, lines surfaces and is critical for protection, absorption, and secretion.

A resting sarcomere at optimal length maximizes overlap between myosin and actin filaments.
This arrangement enhances the potential for contractile force, allowing myosin heads to bind effectively to actin filaments during muscle contraction.