Human Anatomy Chapter: Bone Classification

Classification of Bones

• Short bones are cube-shaped, mainly composed of spongy bone. Examples include carpals and tarsals.
• Flat bones are thin and flattened, usually curved, with compact bone layers surrounding spongy bone. Examples include the skull, ribs, and sternum.
• Irregular bones have irregular shapes and do not fit into other categories. Examples include vertebrae and hip bones.

Gross Anatomy of a Long Bone

• Diaphysis is the shaft of the bone made of compact bone.
• Epiphysis refers to the ends of the bone, composed mostly of spongy bone.
• Periosteum is the fibrous connective tissue membrane covering the diaphysis and housing Sharpey's fibers that secure it to the bone.
• Articular cartilage reduces friction at joint surfaces and covers the epiphysis.
• Medullary cavity contains yellow marrow in adults (mostly fat) and red marrow for blood cell formation.

Microscopic Anatomy of Bone

• Osteon (Haversian System) is a basic unit of bone structure.
• Central (Haversian) canal contains blood vessels and nerves, while perforating (Volkman's) canal connects to it.
• Lacunae are cavities housing osteocytes arranged in concentric rings within lamellae.
• Canaliculi are tiny canals facilitating nutrient transport between the central canal and lacunae.

Changes in the Human Skeleton

• The embryonic skeleton primarily consists of hyaline cartilage, which is largely replaced by bone during development.
• Cartilage persists in specific areas, such as the nose, parts of ribs, and joints.

Bone Growth

• Epiphyseal plates promote long bone growth during childhood, where new cartilage forms, is ossified, and replaced by bone.
• Bones remodel and thicken until growth ceases, influenced by gravity and muscle stress.

Types of Bone Cells

• Osteocytes: mature bone cells.
• Osteoblasts: bone-forming cells.
• Osteoclasts: bone-resorbing cells involved in remodeling and calcium release.

Factors Affecting Bone Growth and Maintenance

• Heredity influences skeletal development and can include genetic conditions like Osteogenesis Imperfecta.
• Nutrition provides essential minerals for bone health; deficiencies can impair growth.
• Hormones regulate aspects such as cell division and calcium metabolism.
• Exercise promotes bone density, while lack of weight-bearing activity can lead to calcium loss.

Types of Fractures

• Closed (simple) fractures involve intact skin; open (compound) fractures break the skin.
• Greenstick fractures are partial breaks common in children; comminuted fractures produce multiple fragments.
• Impacted fractures involve bones forced into one another.
• Pathologic fractures occur without trauma due to bone disorders.

Fracture Healing Process

• Typically takes 6-8 weeks for simple fractures; consists of hematoma formation, fibrocartilage callus, bony callus formation, and remodeling.

Division of the Skeleton

• The axial skeleton includes the skull, vertebral column, and thoracic cage.
• The appendicular skeleton features the pectoral and pelvic girdles and limbs.

Axial Skeleton Details

• Skull consists of 22 bones: 8 cranial (frontal, occipital, etc.) and 14 facial bones (maxillae, mandible, etc.).
• Sutures are immovable joints connecting cranial bones; fontanels ossify by age 2.

Vertebral Column

• Comprises 26 vertebrae: 24 individual, plus sacrum and coccyx; cervical, thoracic, and lumbar regions are distinct.
• Specific vertebrae, like atlas and axis, allow unique movements.

Thoracic Cage

• Protects thoracic organs; composed of vertebrae, ribs, sternum, and their cartilages.
• Ribs are categorized into true, false, and floating ribs based on their connection to the sternum.

Appendicular Skeleton Details

• Pectoral girdle connects arms to the body, consists of 2 clavicles and 2 scapulae.
• The upper limb includes the humerus, radius, ulna, carpals, metacarpals, and phalanges.

Pelvic Girdle

• Composed of 2 ossa coxae, the sacrum, and coccyx; designed for weight-bearing.
• Female pelvis is adapted for childbirth: broader and lighter with a wider pelvic outlet.

Lower Limb Structure

• Includes femur, patella, tibia, fibula, tarsals, metatarsals, and phalanges.
• Tarsals form the ankle, with specific bones like the talus and calcaneus.

Bone Arches and Articulations

• The foot has longitudinal and transverse arches that aid in weight distribution.
• Articulations (joints) allow movement and flexibility, connecting bones unless specified (e.g., hyoid bone).

This quiz explores the classification and anatomy of bones, covering short, flat, irregular bones, and the gross and microscopic anatomy of long bones. Test your knowledge on various bone structures, including the diaphysis, epiphysis, and osteons. Perfect for students studying human anatomy and physiology.