2Q_Sebastian_Science

Musculoskeletal System

• The musculoskeletal system is composed of the skeleton and muscles (smooth, skeletal, and cardiac).
• The skeleton provides support, protects internal organs, stores minerals (like calcium).
• Muscles allow movement, protect organs, and help with digestion and nutrient absorption.
• The nervous system coordinates with the musculoskeletal system for movement.
• The skeleton comprises the axial skeleton (skull, spinal column, ribs, sternum) and appendicular skeleton (clavicle, scapula, hip bones, appendages).
• Bones are classified as long (limbs), short (hands/feet), flat (shoulder blades/skull), and irregular (wrists/ankles/face/vertebral column).

Bone Structure

• Bones contain collagen fibers in mineral salts (calcium & phosphorus).
• Compact bone provides strength & protection.
• Spongy bone has bone marrow (red, yellow).
• Red bone marrow creates blood cells (RBCs, WBCs, platelets).
• Yellow bone marrow is fatty tissue.

Joints

• Joints are where bones meet to enable movement.
• Immovable joints (like skull sutures) don't allow movement.
• Gliding joints allow side-to-side and back-and-forth movement (wrist, ankles, vertebrae).
• Pivot joints allow rotation (lower arm bones).
• Hinge joints allow movement in one direction (elbow, knee).
• Ball-and-socket joints allow movement in all directions (shoulder, hip).

Muscles

• Muscles work in pairs to allow movement (e.g., biceps & triceps).
• Muscles contract (shorten) and relax.
• Muscles are made of muscle fibers.
• Types of muscles include skeletal (voluntary), smooth (involuntary), and cardiac (involuntary in the heart).
• Tendons attach muscles to bones.

Integumentary System

• The integumentary system is the skin, hair, nails, and glands.
• The skin protects, regulates temperature, detects sensations, stores water/fat, produces vitamin D, and removes waste.
• The skin has layers including epidermis (outer) and dermis (inner).
• Melanin gives skin color and protects against UV radiation.
• Sweat helps regulate body temperature.
• The skin has sensory receptors to detect stimuli like touch, pressure, temperature, and pain.

Digestive System

• The digestive system breaks down food to absorb nutrients.
• Mechanical digestion (chewing) breaks food into smaller pieces.
• Chemical digestion uses enzymes to break down large molecules (carbohydrates, proteins, lipids).
• The digestive system includes the mouth, esophagus, stomach, small intestine, large intestine, rectum, and anus.
• Enzymes (e.g., salivary amylase) break down food in different parts of the system.
• Nutrients are absorbed in the small intestine.
• Undigested material is eliminated through the anus.