Exercise 7 Review Sheet Overview Of The Skeleton

Exercise 7 Review Sheet: An Overview of the Skeleton

This comprehensive review sheet delves into the intricacies of the human skeletal system, providing a detailed overview perfect for students and anyone interested in learning more about this fascinating and vital body system. We'll cover key skeletal components, functions, classifications, and important clinical considerations.

I. Major Functions of the Skeletal System

The skeletal system is far more than just a rigid framework; it performs a multitude of crucial functions essential for life. Let's explore these key roles:

A. Support and Structure:

The skeleton provides the structural framework for the body, supporting soft tissues and organs. Think of it as the scaffolding upon which our entire body is built. Without this foundational support, we would collapse. This support is crucial for maintaining posture and overall body shape.

B. Protection of Vital Organs:

The skeleton acts as a protective shield for several delicate and vital organs. The skull safeguards the brain, the rib cage protects the heart and lungs, and the vertebral column shields the spinal cord. This protective function is paramount for survival.

C. Movement and Locomotion:

Bones serve as attachment points for muscles. The interaction between muscles and bones, facilitated by joints, allows for a wide range of movements, from the subtle flick of an eyelid to the powerful stride of a runner. The skeletal system is integral to our ability to move and interact with our environment.

D. Hematopoiesis (Blood Cell Production):

Red and white blood cells, as well as platelets, are produced within the bone marrow, a soft, spongy tissue found inside certain bones. This vital process, hematopoiesis, is essential for maintaining a healthy blood supply.

E. Mineral Storage and Homeostasis:

Bones serve as a reservoir for essential minerals, primarily calcium and phosphorus. These minerals are crucial for various bodily functions, and the skeleton regulates their release into the bloodstream, maintaining mineral homeostasis.

II. Classifications of Bones:

Bones are categorized into several types based on their shape and structure. Understanding these classifications is critical for comprehending their individual functions and roles within the skeletal system.

A. Long Bones:

These bones are longer than they are wide, featuring a shaft (diaphysis) and two ends (epiphyses). Examples include the femur (thigh bone), humerus (upper arm bone), tibia, and fibula (lower leg bones). Long bones are primarily involved in locomotion and weight-bearing. The diaphysis contains the medullary cavity, which houses bone marrow.

B. Short Bones:

Short bones are roughly cube-shaped, with their length, width, and height being approximately equal. Examples include the carpal bones (wrist bones) and tarsal bones (ankle bones). They provide support and stability with limited movement.

C. Flat Bones:

These bones are thin, flattened, and often curved. Examples include the cranial bones (skull bones), ribs, sternum (breastbone), and scapulae (shoulder blades). Flat bones offer protection for underlying organs and provide large surfaces for muscle attachment.

D. Irregular Bones:

Irregular bones have complex shapes that don't fit neatly into the other categories. Examples include the vertebrae (spinal bones) and facial bones. Their unique shapes reflect their specialized functions, such as support, protection, and attachment points for muscles and ligaments.

E. Sesamoid Bones:

These small, round bones are embedded within tendons. The patella (kneecap) is a classic example. Sesamoid bones protect tendons from excessive wear and tear and can improve the efficiency of muscle action.

III. Major Skeletal Divisions:

The human skeleton is broadly divided into two main parts: the axial skeleton and the appendicular skeleton.

A. Axial Skeleton:

The axial skeleton forms the central axis of the body. It includes:

• Skull: Encases and protects the brain. It's composed of cranial bones and facial bones. The cranial bones protect the brain, while the facial bones form the structure of the face. Understanding the sutures (joints) connecting the cranial bones is vital.
• Vertebral Column (Spine): Supports the head and trunk, protects the spinal cord, and allows for flexibility and movement. It consists of cervical (neck), thoracic (chest), lumbar (lower back), sacral (pelvic), and coccygeal (tailbone) vertebrae. The intervertebral discs provide cushioning and flexibility between vertebrae.
• Thoracic Cage (Rib Cage): Protects the heart and lungs. It consists of 12 pairs of ribs, the sternum, and costal cartilages. The ribs are attached to the thoracic vertebrae posteriorly and connect to the sternum anteriorly (except for floating ribs).

B. Appendicular Skeleton:

The appendicular skeleton comprises the bones of the limbs and their attachments to the axial skeleton. It includes:

• Upper Limbs: Include the clavicle (collarbone), scapula (shoulder blade), humerus (upper arm bone), radius and ulna (forearm bones), carpals (wrist bones), metacarpals (hand bones), and phalanges (finger bones). The shoulder joint allows for a wide range of movement, while the elbow and wrist joints offer more specific movements.
• Lower Limbs: Include the pelvic girdle (hip bones), femur (thigh bone), patella (kneecap), tibia and fibula (lower leg bones), tarsals (ankle bones), metatarsals (foot bones), and phalanges (toe bones). The hip joint provides stability and weight-bearing, while the knee and ankle joints allow for complex movements.

IV. Bone Structure:

Understanding the microscopic structure of bone is essential for appreciating its strength, resilience, and ability to remodel.

A. Compact Bone:

This dense, outer layer of bone provides strength and protection. It's organized into osteons (Haversian systems), which are cylindrical units containing blood vessels and nerves.

B. Spongy Bone (Cancellous Bone):

This less dense, inner layer of bone is found within the epiphyses of long bones and in the interior of other bone types. It contains a network of trabeculae (thin, bony plates) that provide lightweight yet strong support. Red bone marrow is found within the spaces of spongy bone.

C. Bone Marrow:

Red bone marrow is responsible for hematopoiesis, while yellow bone marrow is primarily composed of adipose tissue. The distribution of red and yellow bone marrow changes with age.

D. Periosteum and Endosteum:

The periosteum is a tough, fibrous membrane that covers the outer surface of bones (except for articular surfaces), providing protection and serving as an attachment site for tendons and ligaments. The endosteum is a thin membrane lining the inner surfaces of bones, including the medullary cavity.

V. Bone Growth and Development:

Bone tissue is constantly undergoing remodeling, a process involving bone resorption (breakdown) and bone deposition (formation). This dynamic process allows the skeleton to adapt to stress and repair injuries.

A. Intramembranous Ossification:

This process forms flat bones such as skull bones and clavicles. Bone tissue develops directly from mesenchymal connective tissue.

B. Endochondral Ossification:

This process forms most bones in the body, involving the replacement of a cartilage model with bone tissue. Long bone growth occurs at the epiphyseal plates (growth plates) until maturity.

C. Bone Remodeling:

Osteoblasts (bone-forming cells) and osteoclasts (bone-resorbing cells) work together to maintain bone integrity and respond to mechanical stress. This continuous remodeling process is essential for maintaining bone strength and adapting to changing demands.

VI. Important Clinical Considerations:

Several conditions can affect the skeletal system, leading to pain, dysfunction, and other health problems.

A. Fractures:

A fracture is a break in a bone. Types of fractures vary depending on the nature and extent of the break. Treatment options include immobilization (casting or splinting), surgery, and rehabilitation.

B. Osteoporosis:

This condition results in decreased bone density, making bones more susceptible to fractures. Risk factors include age, gender, genetics, and lifestyle factors. Treatment often involves medication and lifestyle changes to improve bone health.

C. Arthritis:

This broad term encompasses many joint disorders characterized by inflammation, pain, and stiffness. Different types of arthritis have varying causes and treatments. Osteoarthritis is a common degenerative joint disease, while rheumatoid arthritis is an autoimmune disease.

D. Osteogenesis Imperfecta (Brittle Bone Disease):

This genetic disorder results in extremely fragile bones prone to fractures. Treatment focuses on managing fractures and improving bone strength.

E. Scoliosis:

This abnormal lateral curvature of the spine can cause pain, deformity, and respiratory problems. Treatment options range from observation to bracing to surgery.

VII. Key Terms and Definitions:

This section provides a concise glossary of key terms related to the skeletal system:

• Articulation: A joint; the point where two bones meet.
• Bone Marrow: Soft tissue found within bones, responsible for blood cell production.
• Cartilage: A flexible connective tissue found at the ends of bones and in other locations.
• Diaphysis: The shaft of a long bone.
• Epiphysis: The end of a long bone.
• Epiphyseal Plate: The growth plate in long bones.
• Fracture: A break in a bone.
• Joint: The point where two or more bones meet.
• Ligament: Connective tissue that connects bones to other bones.
• Osteoblast: A bone-forming cell.
• Osteoclast: A bone-resorbing cell.
• Osteocyte: A mature bone cell.
• Osteoporosis: A condition characterized by decreased bone density.
• Periosteum: The tough, fibrous membrane covering the outer surface of bones.
• Spongy Bone: A less dense type of bone tissue.
• Sutures: Immovable joints found in the skull.
• Tendons: Connective tissues that connect muscle to bone.
• Trabeculae: Thin, bony plates found in spongy bone.

This detailed review sheet provides a comprehensive overview of the human skeletal system. By understanding the various components, functions, classifications, and clinical considerations, you'll gain a much deeper appreciation for this vital and fascinating part of the human body. Remember to consult relevant textbooks and other resources for further in-depth learning and to always seek professional medical advice when needed.