Appendicular Skeleton

Introduction to the Appendicular Skeleton

• Appendicular skeleton

  • Represents 60% of the bones in the human body.

  • Facilitates movement and manipulation of objects.

  • Comprises:

  • Bones of the limbs.

  • Supporting bone girdles.

Overview of the Appendicular Skeleton (Figures 8-1)

• Bones Breakdown:

  • Pectoral Girdles: 4 bones (2 clavicles and 2 scapulae).

  • Upper Limbs: 60 bones (includes humerus, radius, ulna, carpal bones, metacarpals, phalanges).

  • Pelvic Girdle: 2 bones (hip bones).

  • Lower Limbs: 60 bones (includes femur, patella, tibia, fibula, tarsal bones, metatarsals, phalanges).

The Pectoral Girdles

• General Characteristics:

  • Connect each arm to the body.

  • Facilitate shoulder joint positioning and arm movement.

  • Each girdle consists of:

  • One clavicle.

  • One scapula.

  • Connects with the axial skeleton only at the manubrium.

Clavicles (Collarbones)

• Description:

  • S-shaped bones.

  • Originate at the manubrium (sternal end).

  • Articulate with the scapulae at the acromial end.

Scapulae (Shoulder Blades)

• Description:

  • Broad, flat triangles.

  • Articulates with the humerus and clavicle.

  • Anterior surface has a depression known as the subscapular fossa.

  • Comprises three borders:

  • Superior border.

  • Medial border (vertebral border).

  • Lateral border (axillary border).

Features of the Scapulae

• Corners:

  • Superior angle.

  • Inferior angle.

  • Lateral angle (supports glenoid cavity and articulates with humerus).

• Scapular Processes:

  • Coracoid Process: Small and anterior.

  • Acromion: Large and posterior, articulates with clavicle at acromioclavicular joint.

  • Spine: Ridge across posterior surface dividing the supraspinous fossa and infraspinous fossa.

The Upper Limbs

• Skeleton Composition:

  • Consists of bones from the arms, forearms, wrists, and hands.

Humerus

• Description:

  • The only bone in the arm (brachium).

  • Extends from scapula to elbow.

Anatomy of the Humerus (Figures 8-4)

• Key Features:

  • Head: Round proximal portion that articulates with the scapula.

  • Greater and Lesser Tubercle:

  • Greater tubercle: Rounded projection on lateral surface, forms lateral contour of shoulder.

  • Lesser tubercle: Anterior, medial projection; tubercles separated by intertubercular sulcus (bicipital groove).

  • Anatomical Neck: Marks extent of joint capsule.

  • Surgical Neck: Corresponds to the metaphysis of growing bone.

  • Deltoid Tuberosity: Large, rough elevation on lateral surface.

Forearm Anatomy

• Composition:

  • Two long bones: Ulna (medial) and Radius (lateral).

• Articulations:

  • At extension: Olecranon swings into olecranon fossa.

  • At flexion: Coronoid process projects into coronoid fossa.

Wrist and Hand Anatomy

• Carpal Bones:

  • Eight carpal bones categorized into proximal and distal groups.

• Metacarpals and Phalanges:

  • Five metacarpals and 14 phalanges. The thumb (pollex) has two phalanges, while other fingers have three.

The Pelvic Girdle

• General Characteristics:

  • Composed of two hip bones (coxal bones or pelvic bones).

  • Connects to lower limbs and is strong enough to bear body weight.

• Components of Each Hip Bone:

  • Ilium, ischium, pubis (three fused bones).

Acetabulum

• Description:

  • Socket on the lateral surface of each hip bone.

  • Articulates with the head of the femur.

  • The meeting point of ilium, ischium, and pubis.

Pelvis Structure

• Include:

  • True pelvis: Inferior to the pelvic brim, encloses the pelvic inlet.

  • False pelvis: Superior to the pelvic brim.

• Pelvic Outlet:

  • Opened bounded by coccyx, ischial tuberosities, and inferior border of pubic symphysis.

Comparing Male and Female Pelvis

• Characteristics:

  • Female Pelvis: Wider, smoother, lighter, with less prominent markings compared to male pelvis.

  • Wider pelvic outlet for childbirth.

• Sex Differences:

  • Male pelvis is generally narrower with prominent markings.

The Lower Limbs

• General Functions:

  • Bearing weight and facilitating movement.

• Bones of the Lower Limbs:

  • Femur, patella, tibia, fibula, tarsals, metatarsals, and phalanges.

Femur (Thigh Bone)

• Description:

  • Longest and heaviest bone in the body.

  • Head articulates with hip bone at acetabulum.

  • Joins shaft at an angle of approximately 125 degrees.

Knee Joint Anatomy

• Components:

  • Composed of multiple articulations transferring weight from femur to tibia.

• Menisci:

  • Fibrocartilage pads located at femur-tibia articulations, providing cushioning and stabilization.

• Supporting Ligaments:

  • Patellar ligament, popliteal ligaments, anterior and posterior cruciate ligaments, tibial, and fibular collateral ligaments.

Ankle and Foot Structure

• Tarsal Bones: (7 total)

  • Include talus, calcaneus (heel), cuboid, and three cuneiform bones.

• Metatarsals and Phalanges:

  • Five metatarsals, numbered I-V, and 14 phalanges similar to the fingers.

Foot Arches

• Function:

  • Help distribute weight and provide balance.

  • Include: Longitudinal and transverse arches.

Individual Skeletal Variation

• Reveals:

  • Muscle strength and mass, medical history, sex and age, body size.

• Modifications in Female Pelvis:

  • Hormonal changes such as relaxin during pregnancy that allows pelvic inlet and outlet size increase.

Additional Notes on Joints and Movements

• Joints (Articulations):

  • Where two bones meet, facilitating movement.

  • Trade-off exists between strength and mobility.

• Classifications of Joints:

  • Structural: Fibrous, cartilaginous, bony, synovial.

  • Functional: Synarthrosis (immovable), amphiarthrosis (slightly movable), diarthrosis (freely movable).

Aging Effects on Joints

• Common Conditions:

  • Rheumatism, arthritis, osteoarthritis with age as common factors affecting mobility.

• Preventive Measures:

  • Regular physical activity and joint movement to enhance synovial fluid distribution.