Organ Systems PDF

ORGAN SYSTEM - Definition: An organ system consists of multiple organs working together to carry out complex physiological functions essential for survival, such as digestion, circulation, or respiration. - Differences: - Cell: The basic unit of life capable of performing essential processes. -...

ORGAN SYSTEM - Definition: An organ system consists of multiple organs working together to carry out complex physiological functions essential for survival, such as digestion, circulation, or respiration. - Differences: - Cell: The basic unit of life capable of performing essential processes. - Tissue: Groups of similar cells organised to perform specific tasks (e.g., epithelial tissue lining organs). - Organ: Structures composed of tissues that perform specific functions (e.g., the stomach or heart). - Organ System: A group of organs that work together to achieve a common goal, such as maintaining homeostasis (e.g., the digestive or respiratory systems). --- RESPIRATORY SYSTEM 2. Main Function: To supply oxygen to the bloodstream for cellular respiration and remove carbon dioxide. 3. Organs of the Respiratory System**: - Nose: Filters, moistens, and warms incoming air using mucus and cilia. - Pharynx: Connects the nasal cavity to the larynx, directing air towards the respiratory tract. - Trachea: A rigid tube reinforced with cartilage rings that ensures air passage to the bronchi. - Bronchi: Split into bronchioles and lead air into each lung. - Alveoli: Tiny sacs surrounded by capillaries where gas exchange occurs via diffusion. - Lungs: Provide the surface area for gas exchange. - Diaphragm: Contracts and flattens during inhalation, increasing lung volume to draw in air. 4. Effect of Exercise on Breathing Rate: During exercise, the body’s demand for oxygen increases, and carbon dioxide production rises, leading to faster and deeper breathing to maintain gas exchange and homeostasis. --- CIRCULATORY SYSTEM 1. Differences Between Blood Vessels: - Arteries: Thick, muscular walls; carry oxygenated blood under high pressure away from the heart (except pulmonary artery). - Veins: Thinner walls; carry deoxygenated blood back to the heart, often with valves to prevent backflow. - Capillaries: One-cell-thick walls; site of nutrient and gas exchange between blood and tissues. 3. Main Function: To transport oxygen, nutrients, hormones, and waste products, ensuring that all body cells receive what they need and waste products are efficiently removed. 4. Double-Circulatory System: - Pulmonary circulation: Blood flows from the heart to the lungs and back, exchanging carbon dioxide for oxygen. - Systemic circulation: Oxygenated blood is pumped from the heart to the rest of the body and back. 5. Oxygenated vs. Deoxygenated Blood: - Oxygenated blood: Rich in oxygen; carried by arteries (except pulmonary artery). - Deoxygenated blood: Low in oxygen; carried by veins (except pulmonary vein). 6. Blood Components: - Red blood cells: Transport oxygen using haemoglobin. - Haemoglobin: Binds oxygen in the lungs and releases it in tissues. - White blood cells: Defend the body against pathogens. - **Platelets**: Aid in clotting to prevent bleeding. - Plasma: A liquid medium that carries nutrients, hormones, waste products, and other blood cells. 7. Connection Between Systems: Oxygen from the respiratory system diffuses into the bloodstream in the lungs, and the circulatory system transports it to tissues. Carbon dioxide from tissues is carried back to the lungs for exhalation. --- DIGESTIVE SYSTEM 1. **What is Digestion?**: The process of breaking down food into smaller, absorbable molecules to provide energy and nutrients for growth, repair, and metabolism. 2. Types of Digestion: - Mechanical digestion: Physical breakdown of food (e.g., chewing, churning in the stomach). - Chemical digestion: Enzymatic breakdown of macronutrients into smaller molecules. 4. Key Concepts: - Teeth Functions: - Incisors: Cutting food. - Canines: Tearing food. - Molars: Grinding food. - Bolus: Chewed food mixed with saliva, ready to be swallowed. - Oesophagus: Uses peristalsis (wave-like muscle contractions) to move food to the stomach. - Gastric Juice: Contains hydrochloric acid and enzymes (e.g., pepsin) to digest proteins. - Small Intestine : Main site of nutrient absorption, aided by villi that increase surface area. - Large Intestine: Absorbs water and forms faeces.  - Liver: Produces bile, detoxifies substances, and processes nutrients. - Bile: Emulsifies fats, aiding their digestion and absorption. - Villi: Found in the small intestine; tiny, finger-like projections that absorb nutrients into the bloodstream. 5. Macronutrients: - Proteins: Broken down into amino acids by enzymes like pepsin and trypsin. - Fats: Broken down into fatty acids and glycerol by bile and lipase enzymes. - Carbohydrates: Broken down into glucose by enzymes like amylase.