An Open Invitation to Biological Anthropology: Appendix A - Osteology

Jason M. Organ, Ph.D.

• Indiana University School of Medicine

Key Objectives

• Identify anatomical positions, planes, and directional terms for bones and teeth.
• Describe regions of the human skeleton and identify each bone.
• Distinguish major bony features like muscle attachment sites.
• Identify age and sex features in forensic contexts.

Introduction to Osteology

• Study of bones is crucial in biological anthropology.
• Skeletons tell stories of past lives: diet, activity levels, causes of death.
• Sex is a spectrum, influencing bone size/shape for classification.

Bone Structure and Function

• Bone is a mix of collagen and mineral (hydroxyapatite) for strength.
• Comprises cortical (compact) bone and cancellous (trabecular) bone.
• Performs metabolic functions (mineral homeostasis, blood cell production).
• Mechanical functions: protection, support, movement facilitation.

Bone Shape

• Bone shapes relate to function: long, short, flat, sesamoid, irregular.
  • Long Bones: e.g., humerus, femur. Have diaphysis, epiphysis, metaphysis.
  • Short Bones: e.g., carpals. Equal length/width, often form joints.
  • Flat Bones: e.g., skull bones. Consist of two cortical layers with cancellous.
  • Sesamoid Bones: e.g., patella. Form in tendons to reduce friction.
  • Irregular Bones: e.g., vertebrae. Complex shapes.

Bone Functional Adaptation

• Bone remodels in response to stress; osteocytes detect microcracks.
• Osteoclasts remove damaged areas, osteoblasts build new tissue.

Bone Development

• Intramembranous Formation: Direct from connective tissue stem cells.
• Endochondral Formation: From cartilage model, most bones develop this way.

Anatomical Terminology

Anatomical Planes

• Anatomical Position: Standing upright, palms forward.
• Coronal Plane: Divides body into anterior/posterior.
• Transverse Plane: Divides body into superior/inferior.
• Sagittal Planes: Divide body into left/right. Midsagittal is equal halves.

Directional Terms

• Anterior (Ventral): Toward the front.
• Posterior (Dorsal): Toward the back.
• Medial: Closer to midline.
• Lateral: Further from midline.
• Proximal: Closer to trunk.
• Distal: Further from trunk.
• Superior (Cranial): Closer to head.
• Inferior (Caudal): Closer to feet.

Human Skeletal System

Axial Skeleton

• Skull: Cranium and mandible. Contains cranial sutures for age estimation.
• Vertebral Column: Includes cervical, thoracic, lumbar, sacral, coccygeal regions.
• Thoracic Cage: Formed by ribs and sternum.

Appendicular Skeleton

• Pectoral Girdle: Clavicle and scapula.
• Upper Limb: Humerus, radius, ulna, carpals, metacarpals, phalanges.
• Pelvic Girdle: Os coxae (ilium, ischium, pubis).
• Lower Limb: Femur, patella, tibia, fibula, tarsals, metatarsals, phalanges.

Key Terms

• Acetabulum: Hip socket.
• Coronal Suture: Joint connecting frontal and parietal bones.
• Osteocytes: Bone cells involved in repair and maintenance.

Review Questions

• Differences in pelvic girdle features for sex/age estimation.
• Mechanisms of bone formation.
• Articulations of calcaneus and humerus.
• Components of axial vs. appendicular skeleton.

About the Authors

• Jason M. Organ, Ph.D.: Anatomy professor at Indiana University School of Medicine.
• Jessica N. Byram, Ph.D.: Assistant professor focused on anatomy education.

References

• Comprehensive reference list including works by Bass, Boldsen et al., and others.