Axial Skeleton

Skull

The skull is a complex structure composed of several bones that protect the brain and form the structure of the face.

• Calvaria (skull cap)

• Frontal bone

  • Supraorbital foramen

  • Frontal sinus (side view of skull)

• Parietal bones

• Temporal bones

  • External acoustic meatus

  • Zygomatic process (arch portion of bone)

  • Styloid process (underside and side view of skull)

  • Mastoid process (underside and side view of skull)

  • Carotid canal (underside of skull)

  • Jugular foramen (underside of skull)

• Occipital bone

  • Foramen magnum

  • Occipital condyles (joint areas)

• Sphenoid bone

  • Body

  • Optic canal

  • Sella turcica

  • Lesser wings

  • Greater wings

  • Superior orbital fissure (cut)

• Ethmoid

  • Cribriform plate

  • Olfactory foramina (little holes)

  • Crista galli

  • Perpendicular plate

• Mandible

  • Body

  • Ramus

  • Alveolar margin

  • Mental foramen

  • Mandibular angle

  • Coronoid process

• Lacrimal bones

• Nasal bones

• Vomer

• Palatine bones

• Zygomatic bones

  • Zygomatic arch

• Orbit (bones of the eye)

• Nasal cavity

• Sutures of the skull

  • Sagittal

  • Coronal

  • Lambdoid

  • Squamous

• Fetal skull features

  • Frontal suture

  • Anterior fontanel

  • Posterior fontanel

Vertebrae

The vertebral column supports the body and protects the spinal cord. It is divided into regions and contains distinct vertebrae types.

• Curvatures

  • Cervical

  • Thoracic

  • Lumbar

  • Sacral

• Vertebrae

  • Spinous process

  • Transverse processes

  • Vertebral body

• Cervical vertebrae

  • Transverse foramina

  • Atlas (C1)

  • Axis (C2)

  • Odontoid process (dens)

• Thoracic vertebrae

• Lumbar vertebrae

• Sacrum

• Coccyx

• Sternum

  • Manubrium

  • Body

  • Xiphoid process

• Ribs

  • Costal (rib) cartilage

  • True ribs (1-7)

  • False ribs (8-12)

  • Floating ribs (11-12) – no attachment to sternum

• Hyoid bone

Appendicular Skeleton

Upper Limb

The appendicular skeleton includes the bones of the limbs and girdles, enabling movement and manipulation of the environment.

• Scapula

  • Glenoid cavity

  • Coracoid process

  • Acromion

  • Spine

• Clavicle

• Humerus

  • Head

  • Greater tubercle

  • Lesser tubercle

  • Trochlea

  • Olecranon fossa

• Ulna

  • Olecranon process (funny bone)

  • Coronoid process

  • Ulnar head

  • Styloid process

• Radius

  • Radial head

  • Radial neck

  • Styloid process

• Carpals

• Metacarpals

• Phalanges

Lower Limb

• Pelvis/Pelvic bone

  • Ilium

  • Ischium

  • Pubis

  • Acetabulum

  • Pubic symphysis

• Femur

  • Head

  • Fovea capitis

  • Neck

  • Greater trochanter

  • Lesser trochanter

  • Medial condyle

  • Lateral condyle

• Patella

• Tibia

  • Tibial plateau

  • Medial malleolus

• Fibula

  • Head

  • Lateral malleolus

• Tarsals

  • Calcaneus

  • Talus

• Metatarsals

• Phalanges

Joints

Classifications

Joints are classified by their function and structure, which determines their range of movement and stability.

• Function

  • Synarthrosis (immovable)

  • Amphiarthrosis (slightly movable)

  • Diarthrosis (freely movable)

• Structure

  • Fibrous

    • Sutures

    • Gomphosis

    • Syndesmosis

  • Cartilaginous

    • Symphyses

    • Synchondroses

  • Synovial

    • Plane

    • Condyloid

    • Saddle

    • Hinge

    • Pivot

Types of Movements

Joints allow various types of movements essential for daily activities and locomotion.

• Extension/Flexion/Hyperextension

• Rotation (medial and lateral)

• Abduction/Adduction

• Circumduction

• Dorsiflexion/Plantar flexion

• Supination/Pronation

• Inversion/Eversion

• Protraction/Retraction

• Elevation/Depression

Parts of the Knee Joint

The knee is a complex synovial joint with several important structures for stability and movement.

• Medial and lateral condyles

• Tibial plateau

• Ligaments

  • ACL (anterior cruciate ligament)

  • PCL (posterior cruciate ligament)

  • MCL (medial collateral ligament)

  • LCL (lateral collateral ligament)

• Meniscus

  • Medial

  • Lateral

• Patella

  • Patellar ligament

  • Quadriceps femoris tendon

Muscles

Muscles of the Head, Neck, Face, Trunk, and Scapula

These muscles are responsible for facial expressions, chewing, and movements of the head and neck.

• Frontalis

• Occipitalis

• Orbicularis oculi

• Orbicularis oris

• Buccinator

• Zygomaticus minor and major

• Masseter

• Temporalis

• Sternocleidomastoid

• External & internal intercostals

• Diaphragm

• Rectus abdominis

• External oblique

• Internal oblique

• Transverse abdominis

• Serratus anterior

• Trapezius

Muscles that Move the Arm

• Latissimus dorsi

• Pectoralis major

• Deltoid

• Biceps brachii

• Brachialis

• Brachioradialis

• Triceps brachii

Muscles that Move the Leg

• Gluteus maximus

• Gluteus medius

• Quadriceps

  • Rectus femoris

  • Vastus medialis

  • Vastus intermedius

  • Vastus lateralis

• Sartorius

• Hamstring group

  • Biceps femoris

  • Semitendinosus

  • Semimembranosus

• Gastrocnemius

• Soleus

• Tibialis anterior

Muscle Tissues

Muscle Fiber Model

Muscle fibers are specialized cells that contract to produce movement. Their structure is essential for understanding muscle function.

• Endomysium

• Sarcolemma

• Sarcoplasm

• Nucleus/Nuclei

• Mitochondria

• Neuromuscular junction

• Myofibrils

• Sarcomere

  • Actin (thin filament)

  • Myosin (thick filament)

  • Z disc (anchor for thin filament)

Neuromuscular Junction Model

The neuromuscular junction is the site where a motor neuron communicates with a muscle fiber to initiate contraction.

• Motor neuron

• Axon terminal

• Synaptic vesicles with acetylcholine (ACh)

• Mitochondria

• Synaptic cleft

• ACh receptors on muscle end plate

Key Terms and Definitions

• Foramen: An opening or hole in a bone for passage of nerves and blood vessels.

• Process: A projection or outgrowth of bone for muscle attachment or articulation.

• Condyle: A rounded articular area at the end of some bones.

• Trochanter: Large, blunt projection found only on the femur.

• Suture: Immovable joint between skull bones.

• Fontanel: Soft spot on a fetal skull where bone formation is incomplete.

• Synovial joint: Freely movable joint with a fluid-filled cavity.

• Ligament: Connective tissue that connects bone to bone.

• Tendon: Connective tissue that connects muscle to bone.

Example: Synovial Joint Movements

• Hinge joint (e.g., elbow): Allows flexion and extension.

• Ball-and-socket joint (e.g., shoulder, hip): Allows movement in multiple axes and planes.

Additional info:

• The sarcomere is the functional unit of muscle contraction, defined as the segment between two Z discs.

• Acetylcholine (ACh) is the neurotransmitter responsible for stimulating muscle contraction at the neuromuscular junction.

• Ligaments such as the ACL and PCL are crucial for stabilizing the knee joint and preventing excessive movement.