Exercise 11 Articulations And Body Movements Review Sheet

Alright, let's dive into the world of articulations and body movements. This review will cover essential concepts, terminology, and examples, providing you with a solid understanding of how your body moves.

Exercise 11: Articulations and Body Movements Review Sheet

Introduction

Understanding articulations, or joints, and the movements they allow is fundamental to comprehending human anatomy and physiology. This review sheet focuses on the different types of joints, their structural and functional classifications, and the various body movements that occur at these joints. By grasping these concepts, you’ll gain a deeper appreciation for the intricate mechanics of the human body.

I. Articulations: The Meeting Points

Articulations, also known as joints, are the points where two or more bones meet. They are responsible for providing mobility to the skeleton and allowing a wide range of movements. Joints can be classified based on their structure (the material that binds the bones together) and their function (the degree of movement they allow).

A. Structural Classification of Joints

Structural classification categorizes joints based on the type of tissue that connects the bones. There are three main structural classifications: fibrous, cartilaginous, and synovial.

1. Fibrous Joints

Fibrous joints are characterized by bones that are connected by fibrous connective tissue. These joints typically allow little to no movement.

• Sutures: Found only in the skull, sutures are immovable joints that interlock bones with short connective tissue fibers. The sutural ligament ossifies and fuses completely during middle age; these fused sutures are then called synostoses.
• Syndesmoses: In syndesmoses, bones are connected by ligaments, which are longer bands of fibrous tissue. The amount of movement allowed depends on the length of the connecting fibers. An example is the distal tibiofibular joint, which allows slight movement.
• Gomphoses: Gomphoses are peg-in-socket fibrous joints. The only example is the articulation of a tooth with its bony alveolar socket in the jaw. The fibrous connection in this case is the periodontal ligament.

2. Cartilaginous Joints

Cartilaginous joints have bones connected by cartilage. Like fibrous joints, they allow for only limited movement. There are two types of cartilaginous joints:

• Synchondroses: In synchondroses, a bar or plate of hyaline cartilage unites the bones. A classic example is the epiphyseal plate in long bones of children, which is a temporary joint. Another example is the joint between the first rib and the sternum.
• Symphyses: Symphyses involve articular surfaces of the bones covered with hyaline cartilage fused to an intervening pad or plate of fibrocartilage. Symphyses are designed for strength with flexibility. Examples include the intervertebral joints and the pubic symphysis.

3. Synovial Joints

Synovial joints are the most common type of joint in the body and allow for a wide range of movements. These joints are characterized by a fluid-filled joint cavity.

• General Structure: Synovial joints possess several key features:
  • Articular Cartilage: Hyaline cartilage covers the opposing bone surfaces.
  • Joint (Synovial) Cavity: A potential space filled with synovial fluid.
  • Articular Capsule: A two-layered capsule enclosing the joint cavity. The external layer is a tough fibrous capsule, and the inner layer is a synovial membrane.
  • Synovial Fluid: Viscous, slippery fluid that lubricates and nourishes the articular cartilage.
  • Reinforcing Ligaments: Bandlike ligaments that reinforce and strengthen the joint.
• Additional Features: Some synovial joints may also contain:
  • Menisci (Articular Discs): Fibrocartilage pads that improve the fit between articulating bone ends.
  • Bursae: Fibrous sacs lined with synovial membrane and containing synovial fluid, acting as cushions to reduce friction.
  • Tendon Sheaths: Elongated bursae that wrap completely around tendons subjected to friction.

B. Functional Classification of Joints

Functional classification categorizes joints based on the degree of movement they allow. There are three main functional classifications: synarthroses, amphiarthroses, and diarthroses.

1. Synarthroses

Synarthroses are immovable joints. These joints provide strong connections between bones but do not allow movement. Examples include sutures in the skull and gomphoses.

2. Amphiarthroses

Amphiarthroses are slightly movable joints. These joints allow limited movement and provide both stability and flexibility. Examples include the intervertebral discs and the pubic symphysis.

3. Diarthroses

Diarthroses are freely movable joints. These joints allow a wide range of movements and are characteristic of synovial joints. Examples include the shoulder, hip, knee, and elbow joints.

II. Types of Synovial Joints

Synovial joints are further classified based on the shape of their articular surfaces, which determines the type of movement they allow.

A. Plane Joints

Plane joints, also known as gliding joints, have flat articular surfaces that allow for gliding or translational movements. These movements are nonaxial, meaning they do not involve rotation around an axis. Examples include the intercarpal and intertarsal joints.

B. Hinge Joints

Hinge joints feature a cylindrical projection of one bone fitting into a trough-shaped surface on another bone. This arrangement allows for uniaxial movement, specifically flexion and extension. Examples include the elbow joint and the interphalangeal joints.

C. Pivot Joints

Pivot joints allow for uniaxial rotation. They consist of a rounded or conical end of one bone articulating with a ring-shaped structure formed by another bone or by a ligament. Examples include the atlantoaxial joint (allowing rotation of the head) and the proximal radioulnar joint (allowing pronation and supination of the forearm).

D. Condylar Joints

Condylar joints, also known as ellipsoid joints, feature an oval articular surface of one bone fitting into a complementary depression in another bone. This allows for biaxial movement, including flexion and extension, as well as abduction and adduction. An example is the radiocarpal (wrist) joint.

E. Saddle Joints

Saddle joints resemble miniature saddles, with each articular surface having both concave and convex areas. This allows for biaxial movement, similar to condylar joints, but with greater freedom of movement. The best example is the carpometacarpal joint of the thumb, which allows for opposition.

F. Ball-and-Socket Joints

Ball-and-socket joints are the most freely movable type of synovial joint. They feature a spherical head of one bone articulating with a cup-like socket of another bone. This arrangement allows for multiaxial movement, including flexion, extension, abduction, adduction, rotation, and circumduction. Examples include the shoulder and hip joints.

III. Body Movements

Understanding the various movements that occur at synovial joints is crucial for describing and analyzing human motion. These movements can be broadly categorized as angular, rotational, and special movements.

A. Angular Movements

Angular movements involve changing the angle between two bones. These movements include flexion, extension, abduction, adduction, and circumduction.

• Flexion: Decreases the angle of the joint and brings the articulating bones closer together. Examples include bending the elbow or knee.
• Extension: Increases the angle of the joint and straightens the articulating bones. Examples include straightening the elbow or knee.
• Abduction: Moving a limb away from the midline of the body. Examples include raising the arm or leg laterally.
• Adduction: Moving a limb toward the midline of the body. Examples include lowering the arm or leg back to the side.
• Circumduction: Moving a limb in a circular motion, involving a combination of flexion, extension, abduction, and adduction. Examples include drawing circles with the arm or leg.

B. Rotational Movements

Rotational movements involve turning a bone around its longitudinal axis. These movements include medial rotation and lateral rotation.

• Medial Rotation: Turning the anterior surface of a bone toward the midline of the body. Examples include rotating the thigh inward.
• Lateral Rotation: Turning the anterior surface of a bone away from the midline of the body. Examples include rotating the thigh outward.

C. Special Movements

Special movements are those that occur at specific joints and do not fit neatly into the categories of angular or rotational movements. These movements include pronation, supination, dorsiflexion, plantar flexion, inversion, eversion, protraction, retraction, elevation, depression, and opposition.

• Pronation: Rotating the forearm so that the palm faces posteriorly or inferiorly.
• Supination: Rotating the forearm so that the palm faces anteriorly or superiorly.
• Dorsiflexion: Lifting the foot so that its superior surface approaches the shin.
• Plantar Flexion: Depressing the foot (pointing the toes).
• Inversion: Turning the sole of the foot medially.
• Eversion: Turning the sole of the foot laterally.
• Protraction: Moving a body part anteriorly in the horizontal plane. Examples include jutting out the jaw.
• Retraction: Moving a body part posteriorly in the horizontal plane. Examples include pulling the jaw back.
• Elevation: Lifting a body part superiorly. Examples include shrugging the shoulders.
• Depression: Moving a body part inferiorly. Examples include lowering the shoulders.
• Opposition: Touching the thumb to the tips of the other fingers on the same hand.

IV. Examples of Specific Joints and Their Movements

To further illustrate the concepts discussed, let’s examine some specific joints and the movements they allow.

A. Shoulder Joint (Glenohumeral Joint)

The shoulder joint is a ball-and-socket joint formed by the head of the humerus and the glenoid cavity of the scapula. It allows for a wide range of movements, including:

• Flexion: Raising the arm forward.
• Extension: Moving the arm backward.
• Abduction: Raising the arm laterally.
• Adduction: Lowering the arm back to the side.
• Medial Rotation: Rotating the arm inward.
• Lateral Rotation: Rotating the arm outward.
• Circumduction: Moving the arm in a circular motion.

B. Elbow Joint

The elbow joint is a hinge joint formed by the humerus, ulna, and radius. It primarily allows for flexion and extension of the forearm.

• Flexion: Bending the elbow.
• Extension: Straightening the elbow.

The proximal radioulnar joint, located near the elbow, allows for pronation and supination of the forearm.

• Pronation: Turning the palm downward.
• Supination: Turning the palm upward.

C. Hip Joint

The hip joint is a ball-and-socket joint formed by the head of the femur and the acetabulum of the hip bone. It allows for movements similar to the shoulder joint, including:

• Flexion: Raising the thigh forward.
• Extension: Moving the thigh backward.
• Abduction: Raising the thigh laterally.
• Adduction: Lowering the thigh back to the side.
• Medial Rotation: Rotating the thigh inward.
• Lateral Rotation: Rotating the thigh outward.
• Circumduction: Moving the thigh in a circular motion.

D. Knee Joint

The knee joint is a complex hinge joint formed by the femur, tibia, and patella. It primarily allows for flexion and extension of the leg.

• Flexion: Bending the knee.
• Extension: Straightening the knee.

The knee joint also allows for some rotation when the knee is flexed.

E. Ankle Joint

The ankle joint, also known as the talocrural joint, is a hinge joint formed by the tibia, fibula, and talus. It primarily allows for dorsiflexion and plantar flexion of the foot.

• Dorsiflexion: Lifting the foot upward.
• Plantar Flexion: Pointing the toes downward.

The subtalar joint, located below the ankle joint, allows for inversion and eversion of the foot.

• Inversion: Turning the sole of the foot inward.
• Eversion: Turning the sole of the foot outward.

V. Factors Affecting Joint Movement

Several factors can affect the range of motion and stability of joints. These factors include:

A. Shape of Articular Surfaces

The shape of the articular surfaces of the bones in a joint plays a crucial role in determining the type and range of movement allowed. For example, the deep socket of the hip joint provides more stability but limits the range of motion compared to the shallow glenoid cavity of the shoulder joint.

B. Ligaments

Ligaments are strong, fibrous bands that connect bones and provide stability to joints. The number and strength of ligaments in a joint directly influence its stability. Taut ligaments limit movement, while lax ligaments allow for greater range of motion but may compromise stability.

C. Muscle Tone

Muscle tone is the constant, low-level contraction of muscles that surround a joint. Strong muscle tone provides dynamic stability to the joint and helps to prevent injury. Muscles that cross a joint also contribute to movement by contracting and pulling on the bones.

D. Other Factors

Other factors that can affect joint movement include:

• Age: Joint flexibility and range of motion tend to decrease with age due to changes in cartilage, ligaments, and muscles.
• Injury: Previous injuries to a joint can lead to pain, stiffness, and decreased range of motion.
• Disease: Conditions such as arthritis can damage the articular cartilage and other joint structures, leading to pain and limited movement.
• Genetics: Inherited factors can influence joint flexibility and stability.
• Physical Activity: Regular exercise and stretching can improve joint flexibility and range of motion.

VI. Common Joint Injuries and Conditions

Joint injuries and conditions are common and can significantly impact a person's quality of life. Some of the most common joint problems include:

A. Sprains

Sprains are injuries to ligaments caused by excessive stretching or tearing. They are often caused by sudden twists or impacts to a joint. Common sites for sprains include the ankle, knee, and wrist.

B. Dislocations

Dislocations occur when the bones in a joint are forced out of their normal alignment. They can be caused by trauma or excessive force. Dislocations are often painful and require medical attention to realign the joint.

C. Bursitis

Bursitis is inflammation of a bursa, a fluid-filled sac that cushions tendons and ligaments around a joint. It can be caused by overuse, trauma, or infection. Common sites for bursitis include the shoulder, elbow, hip, and knee.

D. Tendinitis

Tendinitis is inflammation of a tendon, a fibrous cord that connects muscle to bone. It is often caused by overuse or repetitive movements. Common sites for tendinitis include the shoulder, elbow, wrist, and ankle.

E. Arthritis

Arthritis is a general term for conditions that cause joint pain, stiffness, and inflammation. There are many different types of arthritis, including osteoarthritis, rheumatoid arthritis, and gout. Arthritis can significantly impact a person's ability to move and perform daily activities.

VII. Maintaining Joint Health

Maintaining joint health is essential for preventing injuries and preserving mobility throughout life. Some strategies for promoting joint health include:

• Regular Exercise: Engage in regular physical activity that includes both strengthening and stretching exercises. This helps to maintain muscle tone, flexibility, and joint stability.
• Proper Nutrition: Consume a balanced diet rich in vitamins, minerals, and antioxidants. Adequate calcium and vitamin D intake are essential for bone health.
• Weight Management: Maintain a healthy weight to reduce stress on weight-bearing joints such as the knees and hips.
• Good Posture: Practice good posture to maintain proper alignment of joints and prevent strain.
• Proper Lifting Techniques: Use proper lifting techniques to avoid injuring the back and other joints.
• Avoid Overuse: Avoid repetitive movements and activities that place excessive stress on joints.
• Rest and Recovery: Allow adequate rest and recovery time for joints after strenuous activity.
• Protective Equipment: Use protective equipment such as braces or pads during activities that carry a risk of joint injury.

VIII. Conclusion

Understanding articulations and body movements is fundamental to comprehending human anatomy, physiology, and kinesiology. By mastering the structural and functional classifications of joints, the types of synovial joints, and the various body movements that occur at these joints, you gain a comprehensive understanding of how the human body moves and functions. Furthermore, knowledge of factors affecting joint movement and common joint injuries and conditions enables you to take proactive steps to maintain joint health and prevent injuries.

IX. FAQ

Q: What is the difference between a sprain and a strain?

A: A sprain is an injury to a ligament, while a strain is an injury to a muscle or tendon.

Q: How can I improve my joint flexibility?

A: Regular stretching exercises, such as yoga or Pilates, can help to improve joint flexibility.

Q: What are some good exercises for strengthening my knees?

A: Exercises such as squats, lunges, and leg presses can help to strengthen the muscles around the knees.

Q: Is it possible to reverse the effects of arthritis?

A: While there is no cure for arthritis, treatments such as medication, physical therapy, and lifestyle modifications can help to manage symptoms and improve quality of life.

Q: What are some warning signs that I may have a joint problem?

A: Warning signs of a joint problem include pain, stiffness, swelling, tenderness, clicking or popping sounds, and decreased range of motion.

This comprehensive review sheet provides a solid foundation for understanding articulations and body movements. By applying this knowledge, you can better appreciate the intricate mechanics of the human body and take proactive steps to maintain joint health and prevent injuries. Remember to consult with healthcare professionals for personalized advice and treatment for any joint-related concerns.