Appendicular skeleton

Appendicular Skeleton: Structure, Function, and Importance

Definition of the Skeletal System

• The skeletal system is the framework of bones and cartilage that supports and protects the body, facilitates movement, produces blood cells, and stores minerals such as calcium and phosphorus.

• Critical Functions of the Skeletal System:

  • Supports the body.

  • Facilitates movement.

  • Protects internal organs.

  • Produces blood cells.

  • Stores and releases minerals and fat.

• Purpose of the Skeletal System:

  • Primary purpose is to give the body its shape and provide attachment points for muscles that move the body.

  • Other purposes include:

    • Storing minerals (such as calcium) and fats (most of the body's calcium is stored in bones).

    • Producing red blood cells.

    • Protecting internal organs.

Overview of the Human Skeletal System

• Classified into two main parts:

  1. Axial Skeleton (80 bones):

     • Central axis of the body that includes the:

       • Skull

       • Vertebral column (spine)

       • Rib cage (ribs and sternum)

  2. Appendicular Skeleton (126 bones):

     • Includes the limbs and girdles (structures that attach limbs to the axial skeleton), which further include:

       • Pectoral girdle (shoulders)

       • Upper limbs (arms and hands)

       • Pelvic girdle (hips)

       • Lower limbs (legs and feet)

Components of the Appendicular Skeleton

• The appendicular skeleton consists of 126 bones divided into two main regions:

  1. Pectoral Girdle and Upper Limbs:

     • Pectoral Girdle (Shoulder Girdle):

       • Clavicle (collarbone)

       • Scapula (shoulder blade)

     • Upper Limbs:

       • Humerus (upper arm)

       • Radius and Ulna (forearm)

       • Carpals (wrist bones)

       • Metacarpals (hand bones)

       • Phalanges (finger bones)

  2. Pelvic Girdle and Lower Limbs:

     • Pelvic Girdle:

       • Hip bones (ilium, ischium, and pubis)

     • Lower Limbs:

       • Femur (thigh bone)

       • Patella (kneecap)

       • Tibia and Fibula (lower leg)

       • Tarsals (ankle bones)

       • Metatarsals (foot bones)

       • Phalanges (toe bones)

Functions of the Skeletal System

• Body Support:

  • Provides structural support and shape to maintain posture and stability.

• Protection of Organs:

  • Protects vital organs (e.g., brain, heart, lungs) from injury by forming protective cages.

• Movement Facilitation:

  • Provides attachment points for muscles, enabling limb and body part movement through joint action.

• Mineral Storage and Blood Production:

  • Stores minerals such as calcium and phosphorus.

  • Produces blood cells in bone marrow, supporting bodily functions.

Comparison of Axial and Appendicular Skeleton

Pectoral Girdle

• Importance of the Pectoral Girdle:

  • Consists of two bones:

    • Scapula

    • Clavicle

  • The clavicle is an S-shaped bone located on the anterior side of the shoulder.

    • Attached medially to the sternum of the thoracic cage (axial skeleton).

    • Laterally articulates with the scapula above the shoulder joint.

  • Right and left pectoral girdles operate independently, providing PTs for maximal limb motion.

• Clavicle Details:

  • Only long bone that lies in a horizontal position.

  • Three regions: medial end (articulates with sternum), lateral end (articulates with scapula), and shaft.

  • Functions:

    • Supports scapula, allows upper limb movement, transmits forces to the sternum, protects nerves and blood vessels.

Scapula

• The scapula anchors the upper limb to the body and is located posteriorly, surrounded by muscles.

• Anatomy of the Scapula:

  • Margins: Superior, medial, and lateral borders.

  • Corners: Superior angle, inferior angle, and glenoid cavity (articulates with humerus).

  • Features: Suprascapular notch, supraglenoid tubercle, and infraglenoid tubercle.

Upper Limb Bones

• Divided into three regions:

  • Arm (between shoulder and elbow)

  • Forearm (between elbow and wrist)

  • Hand (distal to wrist)

• Contains 30 bones:

  • Humerus (upper arm)

  • Ulna and radius (forearm)

  • Eight carpals (wrist)

  • Five metacarpals (palm)

  • Fourteen phalanges (fingers)

Humerus

• Single bone of the upper arm.

• Anatomy Features:

  • Head (articulates with glenoid cavity)

  • Greater tubercle and lesser tubercle (muscle attachment points).

  • Anatomical neck and surgical neck (common fracture sites).

  • Intertubercular groove (bicipital groove for biceps tendon).

  • Distal end articulates with ulna and radius to form elbow.

Radius

• Parallel to ulna on the lateral side of the forearm.

• Anatomical Features:

  • Head (disc-shaped, articulates with capitulum of humerus).

  • Neck and radial tuberosity (muscle attachment).

  • Distal end articulates with carpal bones, forming the wrist joint.

Ulna

• Medial bone of the forearm, resembling a crescent wrench at its proximal end.

• Anatomical Features:

  • Trochlear notch (articulates with trochlea of the humerus).

  • Coronoid process and olecranon process (bony tip of the elbow).

Carpal Bones

• Writs formed by eight carpal bones in two rows:

  • Proximal row: Scaphoid, Lunate, Triquetrum, Pisiform.

  • Distal row: Trapezium, Trapezoid, Capitate, Hamate.

• The scaphoid, lunate, and triquetrum contribute to the radiocarpal joint.

Metacarpal Bones and Phalanges

• Metacarpal Bones:

  • Five elongated bones that form the palm of the hand.

  • Articulate with proximal phalanges to form metacarpophalangeal joints.

• Phalanx Bones:

  • Total of 14 phalanges in fingers and thumb; thumb has two, others have three each.

  • Interphalangeal joints articulate adjacent phalanges.

Pelvic Girdle

• Formed by the hip bone (coxal bone), connecting to the sacrum.

• Pelvis Structure:

  • Composed of two hip bones, sacrum, and coccyx.

  • Areas: Ilium, Ischium, Pubis converge to form the acetabulum of the hip joint.

  • The pelvis bears weight and serves as a foundation for the upper body.

Hip Bone Components

• Adult hip bone is formed from:

  • Ilium (largest part), Ischium (posteroinferior), Pubis (anterior).

• Key Features of the Ilium:

  • Iliac crest, anterior superior iliac spine, arcuate line, greater sciatic notch.

Ischium

• Posterolateral bone of the hip which supports the body when sitting.

• Features: Ischial tuberosity (sitting) and ischial spine.

Pubis

• Anterior portion of the hip bone with features such as:

  • Pubic body, pubic tubercle, superior and inferior pubic rami.

  • Joins at the pubic symphysis.

Overview of Male & Female Pelvis

Lower Limb Structure

• Divided into three regions:

  1. Thigh (hip joint to knee joint)

  2. Leg (knee joint to ankle joint)

  3. Foot (distal to ankle)

• Contains 30 bones:

  • Femur (thigh bone)

  • Patella (kneecap)

  • Tibia and Fibula (lower leg)

  • Tarsals (posterior foot)

  • Metatarsals (mid-foot)

  • Phalanges (toes)

Femur

• Longest and strongest bone in the body (one-quarter of one's height).

• Anatomy Features:

  • Head (articulates with acetabulum).

  • Neck (common fracture site).

  • Greater and lesser trochanters (muscle attachments).

Patella

• Largest sesamoid bone, found in the tendon of quadriceps femoris muscle.

• Articulates with femur, providing leverage and preventing tendon damage.

Tibia

• Main weight-bearing bone, larger than fibula.

• Features: Medial and lateral condyles, intercondylar eminence, and medial malleolus (ankle bump).

Fibula

• Lateral, slender bone not involved in weight-bearing, serves muscle attachment.

• Features: Head (articulates with tibia) and lateral malleolus (ankle bump).

Tarsal Bones

• Seven tarsal bones form the posterior half of the foot.

• Key bones include:

  • Talus (articulates with tibia/fibula to form ankle joint).

  • Calcaneus (heel bone, largest bone of the foot).

  • Cuboid and cuneiform bones (supports foot structure).

Metatarsal Bones and Phalanges

• Five metatarsal bones formed in the anterior half, numbered 1-5.

• Fourteen phalanges (two in big toe, three in other toes).

Congenital and Developmental Abnormalities

• Bone Shape Abnormalities:

  • Irregular shapes affect mobility and function.

• Bone Growth Disorders:

  • Impairs normal bone growth needing medical intervention.

Common Disorders and Injuries

• Degenerative Diseases:

  • Osteoarthritis - deteriorates cartilage and joints.

  • Symptoms: Joint pain and reduced mobility impact quality of life.

Conclusion

• The appendicular skeleton plays a vital role in movement and support, offers protection to vital organs by forming structural frameworks, and understanding disorders enhances appreciation of its role in daily living.