Human Anatomy: Sacrum and Sternum

Sacrum

• The sacrum is a large, triangular bone located at the base of the spine.
• It is formed by the fusion of five sacral vertebrae.
• The sacrum articulates with the coccyx (tailbone) and the two hip bones (ilium), forming the sacroiliac joints.
• These joints are critical for transmitting weight from the upper body to the lower limbs.
• The sacrum supports the weight of the upper body, transferring it to the pelvis.
• It is important in stabilizing the pelvis and providing support to the spine.

Sternum

• The sternum, or breastbone, is a flat bone located in the center of the chest.
• It consists of three parts: the manubrium, the body, and the xiphoid process.
• The sternum serves as an attachment point for the ribs and protects vital organs.
• It provides structural support to the anterior thoracic cage.
• The sternum plays a role in respiration, as ribs attach to the sternum, transmitting forces during breathing.

Ribs

• Ribs are a set of 12 paired, long, curved bones forming the rib cage.
• They connect to the thoracic vertebrae posteriorly and the sternum anteriorly.
• Ribs are categorized as true (1-7), false (8-10), and floating (11-12) based on their attachment to the sternum.
• True ribs attach directly to the sternum via costal cartilage.
• False ribs connect indirectly to the sternum via the costal cartilage of the seventh rib.
• Floating ribs have no anterior attachment to the sternum.
• The rib cage protects the heart, lungs, and other internal organs.
• Rib shape and structure protect underlying organs from external trauma.

Scapula

• The scapula, or shoulder blade, is a large, flat, triangular bone in the posterior thorax.
• It stabilizes the shoulder joint.
• The scapula articulates with the humerus, forming the glenohumeral joint (shoulder joint).
• It's an attachment site for muscles controlling shoulder movements.
• The acromion process of the scapula is part of the shoulder joint complex.
• It connects the upper limb to the upper torso.
• The scapula allows for a wide range of shoulder movements.

Clavicle

• The clavicle, or collarbone, is a long bone connecting the sternum to the scapula.
• It spans the upper chest region.
• It provides stability to the shoulder girdle.
• The clavicle is essential for shoulder movement.
• It transmits forces from the upper limb to the trunk.
• It acts as a brace, preventing shoulder dislocation.
• The clavicle protects underlying nerves and blood vessels.

Humerus

• The humerus is the long bone in the upper arm.
• It is the longest bone in the upper limb, extending from the shoulder to the elbow.
• The humerus articulates with the scapula at the shoulder joint and with the radius and ulna at the elbow joint.
• Its structure and attachments facilitate a wide range of arm movements.
• The humerus supports the arm and hand.