Identifying Joints of the Trunk, Core, and Head

Fibrous joints are responsible for connecting the bones of the skull. The lambdoid suture is the fibrous joint found on the posterior portion of the skull, and is used to connect the occipital bone to the parietal bones.

The coronal suture connects the frontal bones and parietal bones. The sagittal suture joins the parietal bones to one another. The squamous suture joins the parietal and temporal bones. The metopic suture joins the two frontal bones to one another.

The rib bones do not directly interface with the sternum, but are linked to the sternum by regions of hyaline cartilage. The interface between the rib and the cartilage is a costochonral joint. The interface between the cartilage and the sternum is a sternocostal joint. Sternocostal joints are slightly articular synovial joints.

The sternoclavicular joint is the interface between the sternal end of the clavicle and the manubrium of the sternum.

The sutures of the skull are not fused at childbirth possibly to ease passage of the skull through the birth canal. Later in life the sutures fuse to form synarthroses called synostoses and offer much stronger protection of the brain. Fontanelles are the soft spots between the skull bones and will close about 18 months after birth.

Lambda: where the lambdoidal and sagittal sutures meet

Inion: the internal occipital protuberance

Pterion: meeting of the great wing of the sphenoid and parietal bone

Asterion: meeting of the lambdoidal, occipitomastoid, and parietomastoid sutures

The three bones that make up the shoulder joint are the humerus, scapula, and clavicle. The head of the humerus articulates with the glenoid cavity of the scapula and the clavicle articulates with the scapula at the acromioclavicular joint. Collectively these make up the shoulder joint.

The thorax has three major articulations: sternoclavicular, sternocostal, and costochondral joints. The sternoclavicular provides a connection between the upper limbs and the axial skeleton, joining the manubrium of the sternum to the medial end of the clavicle. The sternocostal joints are the attachments between the sternum and the cartilage of ribs 1 to 7. Costochondral joints are the attachments of the ribs to their costal cartilages.

The acromioclavicular joint is formed between the acromion process of the scapula and the distal end of the clavicle. It is local to the shoulder, and is not found in the thoracic cavity.

The atlanto-axial joint is a joint in the upper part of the neck between the first and second cervical vertebrae (the atlas and axis). This joint is a pivot joint; it allows for rotation, flexion, extension, and other movements that our necks can perform.

The atlanto-occipital joint is located between the atlas and the occipital bone and allows the head to nod up and down on the vertical column. The dens acts as a pivot that allows the head to pivot right and left. The alar ligaments check excessive rotation of the head and atlas relative to the axis and the atlanto-axial joint allows the axis and atlas to articulate with one another.

The atlantoaxial joint, a trochoid (pivot) joint where most cervical rotation occurs, sits at the junction of the atlas (C1) and axis (C2). It is the most mobile joint to occur between any two vertebrae in the human body.