Anatomy of the Human Skeleton: Bones and Functions
The Human Skeleton
The human skeleton, along with muscles, joints, ligaments, tendons, and cartilage, forms the locomotor system, enabling movement.
- The skull, trunk, spine, pelvis, upper and lower extremities, hands, and feet constitute the complete human skeleton.
- The skeletal system is divided into the axial skeleton and the appendicular skeleton. The axial skeleton comprises 80 bones located in the skull, face, spine, chest, ribs, sternum, and hyoid bone. The appendicular skeleton includes the bones of the upper and lower limbs, clavicle, scapula, and pelvis.
Functions of the Skeletal System
The skeletal system performs several crucial functions, including:
- Mechanical support: Provides a scaffold that maintains body shape and posture.
- Support: Enables standing and other support positions.
- Dynamic movement: Facilitates walking, locomotion, and body movements, acting as levers and attachment points for muscles.
- Containment and protection: Shields viscera from external pressure or impact; for example, the ribs protect the lungs.
- Metabolic warehouse: Regulates calcium and phosphate salt concentration and exchange.
- Vibration absorption.
Additionally, the spongy bone marrow in some bones carries out hematopoiesis (blood cell formation and differentiation).
Classification of Bones
Long Bones
Long bones are characterized by their length exceeding their other dimensions. They feature two ends (epiphyses), which often connect with other bones at joints, and a shaft (diaphysis) composed of compact bone tissue with a spinal canal filled with yellow bone marrow. The metaphysis, a cartilage disc between the epiphysis and diaphysis, allows for bone lengthening. Long bones are found in the upper and lower limbs, providing strength, structure, and mobility, such as the femur (thigh bone).
Short Bones
Short bones are cube-shaped, with length, width, and height approximately equal.
Examples include the carpal bones (wrist) and tarsal bones (ankle).
Sesamoid bones are a type of short bone found in relation to a tendon, improving joint mechanics. The patella is a prime example.
Supernumerary bones are a type of short bone not present in all individuals.
Flat Bones
Flat bones are characterized by length and width exceeding thickness. They consist of compact laminar tissue (aploe) and spongy center tissue (diploe). These bones form body cavities, such as the skull and rib cage.
Irregular Bones
Irregular bones are those that cannot be classified otherwise, such as the vertebrae. Pneumatic bones, which contain air-filled cavities, also fall into this category. The bones of the face exhibit this feature.
Carpal and Tarsal Bones
Carpal bones – the skeleton of the wrist (there are 8)
- Proximal row: scaphoid, lunate, triquetrum, and pisiform
- Distal row: trapezium, trapezoid, capitate, and hamate
Tarsal bones – the skeleton of the ankle
- Back: talus and calcaneus
- Middle part: navicular, cuboid, and 3 cuneiforms