Skeletal System: Axial and Appendicular Divisions

Overview of the Skeletal System

  • Objective: Identify key structures in the axial and appendicular skeletal divisions.

  • Overview includes an anterior view, posterior view, and lateral view of the body.

Axial Skeletal System

  • Definition: The axial skeleton forms the central axis of the body, protecting vital organs.

  • Regions:

    • Trunk and Head: Comprises bones protecting the brain, heart, and lungs.

    • Key Bones/Structures:

    • Highlighted in blue on various views.

Skull and Cranial Bones

  • Components of the Skull:

    • Frontal Bone: Located at the forehead (shown in blue).

    • Parietal Bone: Lateral to the frontal bone (shown in yellow).

    • Temporal Bone: Found around the ear region.

    • Occipital Bone: Situated at the back of the skull, involved in vision processing.

  • Hyoid Bone:

    • Unique Characteristics:

    • Does not articulate with other bones.

    • Suspended from the styloid processes of the temporal bone.

    • Attachment site for muscles of the tongue (important for speech and chewing).

Vertebral Column

  • Function: Supports and protects the spinal cord.

  • Structure: Forms a flexible longitudinal axis (lengthwise axis of skeleton).

  • Vertebrae Characteristics:

    • Most have a vertebral foramen (opening for spinal cord).

    • Cervical Vertebrae:

    • C2 (Axis): Has a projection (dens) allowing head rotation.

    • C1 (Atlas): Supports the skull.

    • Seventh Cervical Vertebra: Long, blunt spinous process for muscle attachment.

  • Abnormalities:

    • Different curvature can lead to health issues.

Thoracic Region

  • Sternum Structure: (Bone in anterior chest wall)

    • Manubrium: Superior-most part.

    • Body of Sternum: The middle and longest part.

    • Xiphoid Process: The inferior projection.

  • Thoracic Cage:

    • Protects heart, lungs, and abdominal organs.

    • Rib Structure: 12 pairs of ribs classified into:

    • True Ribs: Ribs 1-7 (attach directly to sternum).

    • False Ribs: Ribs 8-12 (do not attach directly, allowing more flexibility).

    • Floating Ribs: Ribs 11 and 12 (only attached by cartilage).

Ribs

  • Types:

    • 12 pairs, articulate with thoracic vertebrae.

    • Ribs 1-7 attach directly to the sternum via costal cartilage.

    • Ribs 8-12 attach indirectly or not at all to the sternum.

  • Functionality: More flexibility with false ribs enhances body movement.

Appendicular Skeleton

  • Definition: Comprises limbs and their points of attachment (shoulders and hips).

Shoulder Girdle

  • Encompasses:

    • Scapula: Shoulder bone.

    • Clavicle: Collarbone.

Upper Limb Structure

  • Humerus: The single bone of the upper arm.

    • Proximal End: Attaches to shoulder.

    • Distal End: Attaches to elbow.

  • Forearm Bones:

    • Ulna: Medial side of the forearm.

    • Radius: Lateral side, in line with the thumb.

Wrist and Hand Bones

  • Carpal Bones: Eight bones forming the wrist, allowing flexibility.

    • Arranged in two rows of four, forming tight ligaments.

    • Connections allow motion in multiple planes.

  • Metacarpal Bones: (Hand bones)

    • Each engages with carpals and phalanges (finger bones).

  • Phalanges Composition:

    • Proximal, middle, and distal phalanx in fingers (thumb has 2, others have 3).

Pelvic Girdle

  • Composed of:

    • Sacrum: Base of the spine.

    • Two Coxal Bones: Fused structures made from ilium, ischium, and pubis.

  • Function: A stable base supporting the trunk and attaching lower extremities.

Lower Limb Structure

  • Femur: The longest and heaviest bone in the body (from hip to knee).

  • Patella: Largest sesamoid bone, acts as a kneecap.

  • Tibia: Known as the shinbone, the stronger, medial bone.

  • Fibula: Laterally placed, thinner than the tibia.

Knee Joint

  • Strengthened by Ligaments:

    • Anterior Cruciate Ligament (ACL): Protects from forward slip.

    • Posterior Cruciate Ligament (PCL): Crosses ACL, provides strength.

Foot Structure

  • Similar to the hand but adapted for weight support and movement.

  • Phalanges: Toe bones, similar in structure to fingers.

  • Tarsal and Metatarsal Bones:

    • Tarsals: Ankle bones.

    • Metatarsals: Foot bones providing structure beyond the ankle.

Foot Arches

  • Two arches in foot allowing movement and energy efficiency.

  • Flat-foot Condition: Lack of arch can cause movement difficulties.

  • High Heels Impact: Increased pressure on the metatarsal heads due to altered arch.

Skeletal Differences between Males and Females

  • Pelvic Structure Comparison:

    • Male Pelvis: Larger, heavier, and deeper (funnel-shaped).

    • Female Pelvis: Shallow, broad, with a wider pubic arch to facilitate childbirth.