Study Guide: Axial and Appendicular Skeleton, Long Bone Structure, and Muscles of the Head and Neck

Axial Skeleton

Skull Sutures and Fontanelles

The skull is composed of several bones joined by immovable joints called sutures. These sutures are important landmarks for anatomical study and clinical assessment. In infants, the skull contains soft spots called fontanelles that allow for growth and flexibility during birth.

• Sutures: Coronal, lambdoid, sagittal, frontonasal, squamous, occipitomastoid

• Fontanelles: Anterior, posterior, mastoid, sphenoid

• Clinical relevance: Fontanelles close as the child grows, and their persistence or abnormal closure can indicate developmental issues.

Vertebral Column

The vertebral column is divided into regions, each with distinct vertebrae. Understanding the features of each vertebra is essential for identifying their location and function.

• General vertebrae terms: Body (centrum), vertebral arch, vertebral foramen, vertebral canal, lamina, pedicle, intervertebral foramen, superior/inferior articular process, transverse process, spinous process, superior/inferior articular facet

• Cervical vertebrae: Atlas (C1), axis (C2), dens (odontoid process), transverse foramina, bifid spinous process

• Thoracic vertebrae: Transverse costal facet, superior/inferior costal facet

• Lumbar vertebrae: Large body, robust structure

• Sacral vertebrae: Superior articular process, ala, median sacral crest, auricular surface, sacral canal, posterior/anterior sacral foramina, sacral promontory, transverse lines of fusion

• Coccyx: Terminal portion of the vertebral column

Thoracic Cage

Sternum and Ribs

The thoracic cage protects vital organs and supports respiration. It consists of the sternum and ribs, each with specific features.

• Sternum: Manubrium, jugular notch, clavicular notch, body, xiphoid process

• Ribs:

  • Vertebrosternal (true ribs, 1-7)

  • Vertebrochondral (false ribs, 8-10)

  • Vertebral (false and floating ribs, 11-12)

• General rib features: Costal cartilage, head, neck, tubercle, articular facet, costal groove, shaft, angle

Structure of a Typical Long Bone

Long Bone Anatomy

Long bones are characterized by a central shaft and two ends. They contain both compact and spongy bone, and are covered by specialized membranes.

• Proximal and distal epiphysis: Ends of the bone, often involved in joint formation

• Diaphysis: Shaft of the bone

• Medullary cavity: Central cavity containing bone marrow

• Epiphyseal line: Remnant of the growth plate

• Compact bone: Dense outer layer

• Spongy bone: Porous inner structure

• Periosteum: Outer fibrous covering

• Endosteum: Inner lining of the medullary cavity

Appendicular Skeleton

Pectoral and Pelvic Girdles

The appendicular skeleton includes the limbs and girdles that attach them to the axial skeleton. The pectoral girdle consists of the scapula and clavicle, while the pelvic girdle is formed by the os coxae.

• Pectoral girdle:

  • Scapula: Glenoid cavity, spine, acromion process, coracoid process, borders, angles, fossae, tubercles

  • Clavicle: Sternal end, acromial end

• Pelvic girdle:

  • Os coxae: Acetabulum, obturator foramen

  • Ilium: Crest, ala, arcuate line, body, sciatic notch, fossa, spines

  • Ischium: Tuberosity, spine, sciatic notch

  • Pubis: Ramus, symphysis, arch

Upper and Lower Appendages

The limbs are composed of multiple bones, each with distinct features for muscle attachment and articulation.

• Upper appendage: Humerus, radius, ulna, carpals, metacarpals, phalanges

• Lower appendage: Femur, patella, tibia, fibula, tarsals, metatarsals, phalanges

Articulations (Joints)

Knee and Shoulder Joints

Joints are sites where bones meet and allow movement. The knee and shoulder are complex synovial joints with multiple supporting structures.

• Knee: Quadriceps tendon, patellar ligament, collateral ligaments, cruciate ligaments, menisci

• Shoulder: Labrum, coracoacromial ligament, subacromial bursa, fibrous capsule, tendon sheath, articular cartilage, biceps brachii tendon, synovial cavity

Muscle Actions

Types of Movements

Muscles produce a variety of movements at joints, classified by their direction and effect.

• Flexion/extension (hyperextension)

• Abduction/adduction

• Supination/pronation

• Protraction/retraction

• Dorsiflexion/plantarflexion

• Inversion/eversion

• Gliding

• Rotation (medial/lateral/right/left)

• Circumduction

• Opposition

• Elevation/depression

Muscles of the Head and Neck

Identification, Origin, Insertion, and Action

Muscles of the head and neck are responsible for facial expressions, mastication, and movement of the head. Each muscle has a specific origin (less movable attachment), insertion (more movable attachment), and action.

• Muscles of the scalp: Epicranius (occipitofrontalis)

• Muscles of the mouth: Buccinator, levator labii superioris, depressor labii inferioris, depressor anguli oris*, mentalis, orbicularis oris, zygomaticus*

• Muscles of the eye: Orbicularis oculi

• Muscles of the neck: Platysma

• Muscles of mastication: Temporalis*, masseter*, medial pterygoid*, lateral pterygoid

• Muscles of mandibular depression: Digastric*

• Muscles that move the head & neck: Sternocleidomastoid*, scalene*, splenius*

Muscle	Origin	Insertion	Action
Epicranius (occipitofrontalis)	NR	NR	Raises eyebrows, wrinkles forehead
Buccinator	NR	NR	Compresses cheek
Orbicularis oris	NR	NR	Closes and puckers lips
Zygomaticus*	NR	NR	Smiling
Orbicularis oculi	NR	NR	Blinks, closes eye
Platysma	NR	NR	Tenses skin of neck
Temporalis*	NR	NR	Elevates mandible
Masseter*	NR	NR	Elevates mandible
Digastric*	NR	NR	Depresses mandible
Sternocleidomastoid*	NR	NR	Rotates and flexes neck

Additional info:

• NR = Not Recorded in provided materials; refer to textbook for detailed origin and insertion.

• Muscles marked with * have antagonists listed.

• Muscle actions are essential for understanding movement and clinical assessment of injuries.