Sciene mid yr8

• Gas exchange

  Oxygen is exchanged for carbon dioxide waste through the process called external respiration
• Normal inhalation

  Diaphragm and external intercostal muscles contract, ribcage elevates, volume of the lungs increases, air pressure drops, and air rushes in
• Pulmonary ventilation

  Air is inhaled through the nasal and oral cavities, moves through the pharynx, larynx, and trachea into the lungs, then exhaled back through the same pathway
• Breathing

  1. Inhalation: air is taken into the lungs

  2. Exhalation: air is passed out of the lungs
• Oxygen from inhaled air diffuses
• Adaptation of Alveolus for Gas Exchange

  • Large surface area
  • Very thin walls
  • Moist inner surface
  • Surrounded by numerous blood capillaries
• Changes to the volume and air pressure in the lungs

  Trigger pulmonary ventilation
• Structures of the human respiratory system

  • Nose
  • The nasal cavity
  • Larynx
  • Trachea
  • Bronchus
  • Bronchiole
  • Lungs
  • Rib cage
  • Diaphragm
  • The intercostal muscles
• Normal exhalation


  Muscles relax, lungs become smaller, air pressure rises, and air is expelled
• Every living species, from a single-celled organism to dominant multicellular organisms, performs respiration
• Blood plasma is a light yellow, slightly cloudy liquid consisting of over 90% water and less than 10% dissolved substances, mostly proteins. It also contains electrolytes, vitamins, and nutrients
• Carbon dioxide diffuses from the tissues into red blood cells and plasma
• External respiration

  Oxygen is exchanged for carbon dioxide waste in the lungs through alveoli
• Red blood cells carry oxygen absorbed from the lungs around the body
• Transport of gases to and from alveoli

  Helped by capillaries to do so quickly
• Respiration


  A metabolic process occurring in all organisms where energy (ATP) is produced by the breakdown of glucose within cells
• Respiration exchanges gases between the bloodstream and body tissues

  Bloodstream delivers oxygen to cells and removes waste carbon dioxide through internal respiration
• Oxygenated blood reaches narrow capillaries, where red blood cells release the oxygen which diffuses into body tissues
• Deoxygenated blood carries the carbon dioxide back to the lungs for release
• Platelets

  Blood component
• Blood as Transport System

  Blood transports oxygen from the lungs to the cells where it is needed for metabolism; Carbon dioxide produced during metabolism is carried back to the lungs by the blood for exhalation; Blood provides cells with nutrients, transports hormones, and removes waste products
• pH value of the blood is kept at a level ideal for the body, which is crucial for proper bodily functions
• Red Blood Cells (RBC)

  Blood component
• White Blood Cells (WBC)

  Blood component
• Blood helps to keep certain things in the body in balance, such as maintaining the right body temperature and pH value
• Plasma

  Blood component: light yellow, slightly cloudy liquid; over 90% water, less than 10% dissolved substances, mostly proteins; contains electrolytes, vitamins, and nutrients like glucose and amino acids
• Regulation of body temperature and protection against diseases are important functions of blood
• Functions of Blood

  • Transport of substances from one part of the body to the other (e.g., respiratory gases, waste products, enzymes); Protection against diseases; Regulation of body temperature