Types of Human Bones

Overview

This lecture reviews the different types of bones in the human skeleton, their characteristics, locations, and significance.

Major Categories of Bones

• There are four main bone types: long, short, flat, and irregular bones.
• Long bones are longer than they are wide, have a shaft and two ends, and are made mostly of compact bone; examples include the femur and humerus.
• There are 90 long bones in the adult skeleton, mainly found in the limbs and clavicle.
• Short bones have similar length and width, are cube-shaped, and consist mainly of spongy bone; found in the tarsals and carpals (28 in total).
• Flat bones are thin, usually curved, and protect vital organs; made of spongy bone surrounded by compact bone; include skull bones, sternum, and ribs (36 total).
• Irregular bones have complex shapes, don't fit other categories, and include the vertebrae, hip bones, hyoid, and some skull bones (48 in total).

Minor Categories of Bones

• Sesamoid bones are small, seed-shaped bones embedded within tendons, such as the patella and pisiform (typically 4 in adults).
• Sutural (wormian) bones are tiny bones that form in the skull sutures; their number and presence vary between individuals.

Characteristics & Classification Notes

• Bone categories are based on shape, structure, and function.
• Some bones may appear to fit multiple categories, so review your textbook for specific course requirements.
• Numbers and specific examples of bones can vary between sources and individuals.

Key Terms & Definitions

• Long bone — longer than wide, mostly in limbs, with a shaft and two ends.
• Short bone — roughly cube-shaped bones found in wrists and ankles.
• Flat bone — thin, curved bones that protect organs.
• Irregular bone — bones with complex, irregular shapes.
• Sesamoid bone — small bones within tendons, such as the patella.
• Sutural (wormian) bone — small bones within skull sutures.

Action Items / Next Steps

• Double-check your textbook for category assignments and bone counts required by your course.
• Take the practice quiz linked in the lecture description to check your understanding.
• Review the anatomy video playlist for more details on skeletal structures.