Lab Practical #2 Review: The Skeletal System and Joints

The Skeletal System

Skull

The skull is composed of several bones and features that protect the brain and support facial structures.

• Frontal, Parietal, Occipital, and Temporal Bones: Major cranial bones forming the skull's structure.

• Coronal, Lambdoid, Squamous, and Sagittal Sutures: Immovable joints connecting skull bones.

• Sphenoid: Contains the greater wing, lesser wing, and superior orbital fissure (passage for nerves and vessels).

• Ethmoid: Features crista galli (attachment for brain membranes) and perpendicular plate (forms part of nasal septum).

• Vomer: Forms the inferior part of the nasal septum.

• Infraorbital and Supraorbital Foramina: Openings for nerves and blood vessels to the face.

• Orbits: Eye sockets formed by several bones.

• Maxilla: Upper jaw bone.

• Mandible: Lower jaw bone; contains mental foramina for nerves.

• Mastoid and Styloid Processes: Projections of the temporal bone for muscle attachment.

• External and Internal Auditory/Acoustic Meatus: Canals for sound transmission and nerve passage.

• Foramen Magnum: Large opening for the spinal cord to connect with the brain.

Hyoid Bone

The hyoid bone is a U-shaped bone in the neck that supports the tongue and is not directly attached to other bones.

• Function: Assists in swallowing and speech.

Vertebrae

The vertebral column consists of individual vertebrae, each with distinct features.

• Body: Main weight-bearing portion.

• Spinous and Transverse Processes: Projections for muscle and ligament attachment.

• Vertebral Foramen: Canal for the spinal cord.

• Intervertebral Foramina: Openings for spinal nerves.

• Cervical Vertebrae: Have transverse foramina for arteries; Atlas (C1) supports the skull; Axis (C2) has the dens for rotation.

• Thoracic Vertebrae: Articulate with ribs.

• Lumbar Vertebrae: Large bodies for support.

• Sacrum: Fused vertebrae; anterior and posterior sacral foramina for nerves.

• Coccyx: Tailbone; remnant of a vestigial tail.

Sternum and Ribs

The sternum and ribs protect thoracic organs and assist in respiration.

• Sternum: Consists of manubrium, body, and xiphoid process.

• Ribs: True ribs (1-7) attach directly to sternum; false ribs (8-12) do not; floating ribs (11-12) have no anterior attachment.

Pectoral Girdle

The pectoral girdle connects the upper limb to the trunk.

• Clavicle: Acromial (lateral) end articulates with the acromion of scapula; sternal (medial) end articulates with the sternum.

• Scapula: Features spine, acromion, coracoid process (attachment for pectoralis minor muscle), and glenoid cavity (articulates with head of humerus).

Upper Limb Bones

• Humerus: Head articulates with scapula; greater/lesser tubercles for muscle attachment; deltoid tuberosity (attachment for deltoid muscle); capitulum articulates with radius; trochlea articulates with trochlear notch of ulna.

• Ulna: Olecranon forms elbow; trochlear notch articulates with humerus; head at distal end.

• Radius: Head articulates with humerus; radial styloid process at distal end.

• Carpals: Eight wrist bones.

• Metacarpals: Five bones of the palm.

• Phalanges: Finger bones.

Pelvic Girdle

The pelvic girdle supports the lower limbs and protects pelvic organs.

• Coxal Bone: Composed of ilium, ischium (with ischial tuberosities), and pubis (with pubic symphysis).

• Obturator Foramen: Large opening for nerves and vessels.

• Acetabulum: Articulates with the head of femur.

Lower Limb Bones

• Femur: Head articulates with acetabulum; fovea capitis (ligament attachment); greater/lesser trochanters for muscle attachment; medial/lateral condyles and epicondyles; patellar surface articulates with patella.

• Patella: Kneecap; protects knee joint.

• Tibia: Tibial tuberosity (attachment for patellar ligament); medial malleolus (ankle).

• Fibula: Head at proximal end; lateral malleolus (ankle).

• Tarsals: Talus (ankle bone); calcaneus (heel bone).

• Metatarsals: Five bones of the foot.

• Phalanges: Toe bones.

Types of Joints

Structural Classification

Joints are classified by the material binding them and their movement capacity.

• Fibrous Joints: Bones joined by fibrous tissue; immovable. Examples: sutures (skull), gomphosis (teeth in sockets).

• Cartilaginous Joints: Bones joined by cartilage; slightly movable. Examples: symphysis (pubic symphysis, intervertebral discs).

• Synovial Joints: Freely movable; characterized by a joint cavity. Types include:

  • Hinge: Elbow, knee.

  • Pivot/Rotational: Proximal radioulnar joint (head of radius).

  • Ball and Socket: Hip, shoulder.

Functional Classification

Joints are also classified by their degree of movement.

• Synarthrosis: Immovable joints (e.g., sutures).

• Amphiarthrosis: Slightly movable joints (e.g., symphyses).

• Diarthrosis: Freely movable joints (all synovial joints).

Joint Classification Table

Structural Type	Example	Movement
Fibrous	Sutures, Gomphosis	Immovable (Synarthrosis)
Cartilaginous	Symphysis (pubic, intervertebral)	Slightly movable (Amphiarthrosis)
Synovial	Hinge, Pivot, Ball and Socket	Freely movable (Diarthrosis)

Range of Motion

Types of Movements

Joints allow various movements, essential for daily activities and locomotion.

• Flexion: Decreases the angle between bones (e.g., bending elbow).

• Extension: Increases the angle between bones (e.g., straightening elbow).

• Hyperextension: Extension beyond normal range.

• Abduction: Movement away from the midline.

• Adduction: Movement toward the midline.

• Circumduction: Circular movement combining flexion, extension, abduction, and adduction.

• Dorsiflexion: Upward movement of the foot at the ankle.

• Plantar Flexion: Downward movement of the foot at the ankle.

Example:

When walking, the knee joint (a hinge synovial joint) undergoes flexion and extension, while the hip joint (a ball and socket synovial joint) allows for circumduction.