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Radius; The radius is one of the two forearm bones, located on the lateral (thumb) side of the forearm. It primarily articulates with the humerus at the elbow and with the carpal bones at the wrist, enabling pronation and supination. Unlike the humerus, it does not form the upper arm structure but instead functions in forearm rotation. This makes it anatomically distal to the marked upper arm bone.

Ulna: The ulna is the medial forearm bone, positioned on the side of the little finger. It forms the primary hinge joint with the humerus at the elbow, providing stability during flexion and extension. However, it does not extend into the upper arm region and is not involved in shoulder articulation. Compared to the humerus, it is a forearm stabilizing bone rather than the main upper limb shaft.

Femur: The femur is the long bone of the thigh and the strongest bone in the body, extending from the hip joint to the knee joint. It supports weight-bearing and locomotion in the lower extremity. Although it is also a long bone like the humerus, it is located in the lower limb and has no anatomical relationship to the upper arm region.

Coccyx: The coccyx is the small terminal segment of the vertebral column, commonly called the tailbone. It is formed by fusion of 3–5 small vertebrae and lies inferior to the sacrum. It serves as an attachment site for ligaments and pelvic floor muscles. Compared to the sacrum, it is much smaller and more distal, making it unlikely to be the marked structure.

Ilium: The ilium is the largest and superior portion of the hip bone, forming the broad flared structure of the pelvis. It articulates with the sacrum at the sacroiliac joint and contributes to the acetabulum. Its main role is weight-bearing and muscle attachment for the abdominal and gluteal muscles. Unlike the midline sacrum, the ilium is lateral and paired on both sides.

Lumbar vertebrae: The lumbar vertebrae are five large vertebrae located in the lower back above the sacrum. They provide major support for body weight and allow flexion and extension of the trunk. While they articulate directly with the sacrum, they are separate segmented bones rather than a fused triangular structure.

Scapula: The scapula is a flat, triangular bone located on the posterior aspect of the thoracic cage, commonly referred to as the shoulder blade. It provides attachment for multiple muscles that control shoulder and arm movement, including the rotator cuff muscles. Unlike the clavicle, it is positioned on the back of the body and does not form a direct bony link to the sternum.

Sternum: The sternum is a flat midline bone located in the anterior thorax, consisting of the manubrium, body, and xiphoid process. It serves as an attachment site for the ribs and protects vital thoracic organs such as the heart and great vessels. Unlike the clavicle, it is centrally located and does not extend laterally toward the shoulder.

Humerus: The humerus is the long bone of the upper arm extending from the shoulder to the elbow. It forms the major structural component of the arm and articulates with the scapula at the shoulder joint. However, it does not form the shoulder girdle connection to the sternum, making it distinct from the clavicle.

Tibia: The tibia is the larger, medial weight-bearing bone of the lower leg. It forms the primary structural support for the body’s weight and articulates with the femur at the knee and the talus at the ankle. Compared to the fibula, it is thicker, stronger, and located medially, making it the main load-bearing bone rather than a stabilizing lateral bone.

Patella: The patella is a sesamoid bone located within the tendon of the quadriceps femoris muscle at the anterior knee. It functions to improve leverage during knee extension and protects the knee joint from trauma. Unlike the fibula, it is not a long bone of the leg shaft but a small triangular bone situated in front of the knee joint.

Femur: The femur is the longest and strongest bone in the body, located in the thigh region between the hip and knee joints. It is a major weight-bearing bone involved in locomotion and muscle attachment for powerful lower limb movements. Compared to the fibula, it is much larger and located proximally in the thigh rather than the lower leg.

Humerus: The humerus is the long bone of the upper arm extending from the shoulder to the elbow joint. It serves as the primary structural bone of the upper limb and articulates with both the radius and ulna at the elbow. Compared to the radius, it is more proximal and located in the arm rather than the forearm.

Carpals: The carpals are a group of eight small bones forming the wrist joint between the forearm and the hand. They allow flexibility and fine movements of the wrist but do not extend along the forearm shaft. Unlike the radius, they are distal structures located at the wrist rather than a long forearm bone.

Ulna: The ulna is the medial forearm bone located on the little finger side. It forms the main hinge joint with the humerus at the elbow, providing stability during flexion and extension. Compared to the radius, it is more medial and less involved in wrist articulation and rotational movement.

Metacarpals: The metacarpals are five long bones located in the palm of the hand, positioned between the carpals and the phalanges. They form the framework of the hand and support finger movements and grip strength. Compared to the carpals, they are longer and more tubular, forming the “palm bones” rather than the wrist structure.

Radius: The radius is the lateral forearm bone on the thumb side that extends from the elbow to the wrist. It articulates distally with the carpals to form part of the wrist joint but is not part of the wrist bones themselves. Unlike the carpals, it is a long bone of the forearm rather than a cluster of small bones.

Phalanges: The phalanges are the bones of the fingers and thumb, arranged in three segments per finger (except the thumb, which has two). They allow fine motor movements such as grasping and writing. Compared to the carpals, they are distal and elongated structures forming the digits rather than the wrist joint itself.

Tibia: The tibia is the larger, medial bone of the lower leg that carries most of the body’s weight. It articulates with the femur at the knee joint and with the talus at the ankle joint. Compared to the femur, it is located distal to the thigh and is part of the leg rather than the upper portion of the lower limb.

Patella: The patella is a small sesamoid bone embedded within the quadriceps tendon at the front of the knee. Its primary function is to improve leverage during knee extension and protect the knee joint. Unlike the femur, it is a small, anterior bone rather than a long weight-bearing shaft.

Fibula: The fibula is the slender lateral bone of the lower leg that runs parallel to the tibia. It contributes to ankle stability and muscle attachment but does not bear significant body weight. Compared to the femur, it is much thinner and located in the lower leg rather than the thigh.

Maxilla: The maxilla forms the upper jaw and is a fixed bone of the facial skeleton. It contributes to the hard palate, the floor of the orbit, and the upper dental arch. Unlike the mandible, it is immovable and does not form a joint for chewing motion.

Zygomatic bone: The zygomatic bone forms the prominence of the cheek and part of the lateral wall of the orbit. It contributes to facial contour and protection of the eye. Compared to the mandible, it is a non-movable facial bone and does not participate in jaw movement or mastication.

Temporal bone: The temporal bone forms part of the lateral skull and houses structures of the ear. It contributes to the cranial base and forms the socket for the mandibular articulation (TMJ). However, it is not the jawbone itself but rather the bone that articulates with the mandible.

Coronal suture: The coronal suture is located between the frontal bone and the paired parietal bones. It runs transversely across the skull from side to side, separating the anterior cranial vault from the superior region. It allows growth of the skull in the anterior-posterior direction during early development. Unlike the sagittal suture, it is not located along the midline but rather forms a horizontal junction.

Lambdoid suture: The lambdoid suture is found at the posterior aspect of the skull, where the parietal bones meet the occipital bone. It has a characteristic inverted “V” or lambda shape. It plays a role in posterior cranial expansion during development. Compared to the sagittal suture, it is posterior and not located along the midline of the skull.

Squamous suture: The squamous suture is located laterally between the temporal bone and the parietal bone. It is curved and relatively flat, forming part of the lateral skull wall. It allows articulation between these bones and contributes to cranial stability. It is not midline like the sagittal suture and is instead positioned on the sides of the skull.

Sphenoid bone: The sphenoid bone is a centrally located cranial bone forming part of the middle cranial fossa and posterior orbital wall. It has a complex butterfly shape with greater and lesser wings and contains the sella turcica for the pituitary gland. It contributes to multiple foramina including the optic canal and superior orbital fissure for neurovascular transmission. Unlike the temporal bone, it is midline and not associated with hearing structures or the TMJ.

Parietal bone: The parietal bone is a flat bone forming the superior and lateral aspects of the cranial vault. It articulates with adjacent bones via sutures including the coronal, sagittal, and lambdoid sutures. Its primary role is protection of the cerebral hemispheres beneath it. It lacks involvement in auditory structures, neurovascular canals, or mandibular articulation.

Occipital bone: The occipital bone forms the posterior skull and surrounds the foramen magnum, allowing passage of the spinal cord. It articulates with the atlas vertebra to enable nodding movements of the head. It also provides attachment for nuchal muscles that support head posture. Unlike the temporal bone, it is not involved in hearing or jaw articulation.