BIOH 201: Lab 05 - Skeletal System Notes

Functions of the Skeletal System

• Movement (Appendicular Skeleton): Provides a framework for muscles to act upon, facilitating both voluntary and involuntary movements. The appendicular skeleton includes the limbs, shoulders, and pelvic girdles, allowing for more complex motion like running and manipulation of objects.

• Blood Cell Production: The bone marrow within certain bones is responsible for producing red blood cells, white blood cells, and platelets through a process called hematopoiesis. This function is crucial for maintaining healthy blood levels and immune response.

• Protection: Bones offer structural protection to vital organs. For instance, the skull houses and protects the brain and the rib cage guards the heart and lungs from physical injury, thus playing a critical role in overall safety and functionality of the body.

• Storage: The skeletal system serves as a reservoir for minerals, particularly calcium and phosphorus, which are vital for many physiological processes including nerve conduction, muscle contraction, and blood clotting. This mineral storage function can also be mobilized as needed to maintain mineral balance throughout the body.

• Muscle Attachment: The skeletal system provides various attachment points for skeletal muscles, which facilitate movement. Tendons connect muscles to bones at these points, ensuring effective force generation and movement.

Bone Markings

• Definition: Bone markings refer to specific landmarks on the surface of bones that serve various functions related to muscle attachment, joint articulation, and passage of nerves and blood vessels.

• Types:

  1. Projections for Muscle Attachment: Areas where muscles attach to bones.

  2. Depressions: Indentations or hollows in bones that can receive muscles, tendons, or ligaments.

  3. Projections to Form Joints: Structures forming part of a joint to facilitate movement.

  4. Passages for Nerves and Blood Vessels: Holes or openings in bones allowing the transit of important bodily structures.

Projections for Muscle Attachment

Types of Bone Projections

• Tuberosity: A rounded, raised area on a bone that provides leverage and support for muscles.

• Trochanter: A large, rough process found specifically on the femur, serving as a major attachment point for muscles of the hip and thigh.

• Tubercle: A small rounded surface on a bone that facilitates muscle attachment, often found on the humerus.

• Process: A general term for any raised area or projection on the surface of bones, which may serve various functions.

Depressions for Muscle Attachment

• Fossa: A shallow depression or hollow area on a bone surface, such as the glenoid fossa of the scapula, which accommodates other structures.

• Sulcus: A groove or furrow on the bone surface that typically serves as a pathway for nerves, blood vessels, or tendons, allowing for better organization and protection of these structures.

Projections that Help Form Joints

• Head: A rounded end of a bone that often articulates with another bone to form a joint, like the head of the femur in the hip joint.

• Facet: A flat surface on a bone allowing for a smooth articulation with another bone, common in vertebrae.

• Condyle: A rounded projection at the end of a bone that connects with another bone to form a joint, such as the femoral condyles in the knee joint.

Passages for Nerves and Vessels

• Foramen: Round holes in the bone that allow the passage of nerves, blood vessels, and other essential structures, ensuring communication and support within the skeletal system.

Types of Bones

1. Long Bones: Support body weight and facilitate movement through levers.

   • Examples: Humerus, Femur, Tibia.

2. Flat Bones: Provide protection to internal organs and serve as attachment points for muscles.

   • Examples: Skull bones, sternum, scapulae.

3. Short Bones: Typically cube-shaped, providing stability and support with limited motion.

   • Examples: Carpals, Tarsals.

4. Irregular Bones: Characterized by complex shapes and functions that do not fit into the other categories.

   • Examples: Vertebrae, sacrum.

5. Sesamoid Bones: Embedded in tendons, they help to reinforce and protect these tendons from stress and wear.

   • Example: Patella, or kneecap.

Structure of Long Bones

• Compact Bone: The dense outer layer that provides strength and support, critical for bearing weight.

• Spongy Bone: Found inside bones, consists of a network of trabeculae that form a reticular structure, facilitating the distribution of stress and pressure. The ends of femurs often consist mainly of spongy bone, which is lighter yet strong.

• Medullary Cavity: The cylindrical cavity within long bones, which is filled with bone marrow; crucial for blood cell production and fat storage.

• Bone Marrow: This vital tissue is categorized into red marrow, responsible for blood cell production, and yellow marrow, which is rich in fat and serves as an energy reserve.

Bone Tissue Histology

• Major Components: The microscopic structure of bone consists of:

  • Osteoclasts: Bone-resorbing cells that break down the bone matrix, playing a crucial role in bone remodeling and calcium homeostasis.

  • Osteoblasts: Cells responsible for synthesizing the bone matrix and facilitating bone formation; essential during growth and healing.

  • Osteocytes: Mature bone cells that maintain bone structure and communicate with other bone cells to ensure its health.

  • Presence of lamellae (the concentric layers of bone), canaliculi (tiny channels connecting osteocytes), and trabeculae (the supporting strands of spongy bone) are also important for bone integrity.

Articular Movements and Joints

1. Flexion/Extension: Movements that decrease or increase the angle between two body parts; occur in joints like the elbow and knee.

2. Abduction/Adduction: Movements away from or toward the midline of the body; significant in shoulder and hip joints.

3. Rotation: Twisting movements around an axis, seen in joints like the head and hip, allowing for directional changes.

4. Circumduction: Circular movements that combine flexion, extension, abduction, and adduction; commonly seen in the shoulder joint.

5. Pronation/Supination: Movements specific to the forearm that turn the palm up or down.

6. Inversion/Eversion: Movements at the ankle that tilt the sole of the foot inward or outward, respectively.

Types of Joints

• Ball and Socket Joint: Allows for the widest range of movement, enabling rotation and multidirectional movement; examples include the shoulder and hip joints.

• Pivot Joint: Allows for rotational movement; an example is found between the first two cervical vertebrae, enabling head rotation.

• Saddle Joint: Permits movement in two planes; an example is the joint of the thumb, allowing for opposition movement essential for grasping.

• Hinge Joint: Functions similarly to a door hinge, permitting flexion and extension; a classic example is the elbow joint.

• Condylar Joint: Allows movement but with limited rotation; examples include the finger joints, enabling a grasping motion.