Biology 9 Quarter 1: Respiratory System

Respiratory System

• Responsible for breathing; oxygen intake and carbon dioxide expulsion are critical functions.
• Nose: Filters, warms, humidifies air; primary entry point for inhalation.
• Mouth: Alternative airway that allows for increased airflow during activities such as exercise.
• Pharynx: Connects nasal and oral cavities to the larynx and esophagus, serving as a passageway for air and food.
• Larynx: Contains vocal cords; directs air from the pharynx to the trachea, preventing food from entering the airway.
• Trachea: Tube that transports air; lined with cilia to trap particles and transport inhaled air to bronchi.
• Lungs: Spongy organs facilitating gas exchange between air and bloodstream.
• Bronchi: Main branches from the trachea that carry air into each lung, dividing into smaller passages.
• Bronchioles: Smaller air passages that lead to alveoli, branching from the bronchi.
• Alveoli: Tiny air sacs where oxygen enters the blood and carbon dioxide is expelled; critical for gas exchange.
• Diaphragm: Dome-shaped muscle that contracts and relaxes to change chest cavity pressure, enabling breathing.

Breathing Mechanism

• Inhalation (Inspiration): Diaphragm and intercostal muscles contract, expanding chest cavity and reducing thoracic pressure, allowing air to flow into lungs.
• Exhalation (Expiration): Diaphragm relaxes, chest cavity volume decreases, thoracic pressure increases, forcing air out of the lungs.

Circulatory System

• Life support structure that nourishes cells with oxygen and nutrients; transports waste products away from the body.
• Comprises the heart, blood, and blood vessels, distributing oxygen and nutrients while removing carbon dioxide and waste.

Components of the Circulatory System

• Heart: Pumps blood throughout the body; has four chambers - two atria (upper chambers) and two ventricles (lower chambers).

  • Atria: Receive blood from the body (Right Atrium) and lungs (Left Atrium).
  • Ventricles: Pump blood to the lungs (Right Ventricle) and body (Left Ventricle).
  • Four valves prevent backward blood flow, controlling circulation through heart and vessels.

• Blood Vessels: Transport blood throughout the body.

  • Arteries: Carry oxygenated blood away from the heart to tissues.
  • Veins: Transport deoxygenated blood back to the heart.
  • Capillaries: Smallest vessels, connecting arteries and veins; site for gas and nutrient exchange.

• Blood: Delivers materials (oxygen and nutrients) throughout the body.

Blood Flow through the Heart

• Blood from lungs enters the left atrium.
• Contraction of the left atrium pushes blood to the left ventricle.
• Left ventricle contraction sends blood to the body.
• One-way valves ensure blood flows in the correct direction and prevents backflow.
• Blood circulates through two pathways: pulmonary circulation and systemic circulation.