RESPIRATORY SYSTEM Topic 6.4 IB Biology Miss Werba

NERVOUS & ENDOCRINE SYSTEMS TOPIC 6 - PHYSIOLOGY 6.1 DIGESTIVE SYSTEM 6.2 CIRCULATORY SYSTEM 6.3 IMMUNE SYSTEM 6.4 RESPIRATORY SYSTEM 6.5 NERVOUS & ENDOCRINE SYSTEMS 6.6 REPRODUCTIVE SYSTEM J WERBA – IB BIOLOGY 2

THINGS TO COVER Ventilation, gas exchange and cell respiration Need for ventilation system Features of alveoli adapted for gas exchange Structure of ventilation system Mechanism of ventilation of the lungs J WERBA – IB BIOLOGY 3

RESPIRATORY SYSTEM TERMS 6.4.1 RESPIRATORY SYSTEM TERMS Ventilation: The exchange of air between the lungs & the environment (via act of breathing) Gas Exchange: The exchange of O2 and CO2 between the alveoli & bloodstream Cell Respiration: Release of energy from the breakdown of organic compounds (aerobic = O2) J WERBA – IB BIOLOGY 4

THE NEED FOR VENTILATION 6.4.2 THE NEED FOR VENTILATION Maintains a concentration gradient of gases between alveoli and the blood The body needs O2 for cell respiration and produces CO2 as waste, which must be removed The alveoli must have high levels of O2 and low levels of CO2 to promote diffusion of gases (O2 in ; CO2 out) The ventilation system removes CO2 and replenishes O2 from the atmosphere to maintain the gradient It also has a large surface area J WERBA – IB BIOLOGY 5

THE RESPIRATORY SYSTEM: Command terms: DRAW and LABEL 6.4.4 THE RESPIRATORY SYSTEM: Command terms: DRAW and LABEL nasal cavity buccal cavity pharynx epiglottis oesophagus larynx ring of cartilage trachea R. bronchus cut rib L. lung bronchioles external intercostal muscles pleural cavity inner pleural membrane internal intercostal muscles outer pleural membrane abdominal cavity diaphragm capillary network alveoli Ref: Rowland p205 J WERBA – IB BIOLOGY 6

THE RESPIRATORY SYSTEM: Command terms: DRAW and LABEL 6.4.4 THE RESPIRATORY SYSTEM: Command terms: DRAW and LABEL J WERBA – IB BIOLOGY 7

6.4.3 THE ALVEOLI J WERBA – IB BIOLOGY 8

6.4.3 THE ALVEOLI There are a number of features of alveoli that make them highly efficient in their job of gas exchange: They have a large surface area: there are hundreds of millions of alveoli huge overall surface area:volume ratio They have very thin walls: walls only a single layer of flattened cells creates short diffusion distances for gases J WERBA – IB BIOLOGY 9

THE ALVEOLI The walls are kept moist: alveolus walls secrete a fluid 6.4.3 THE ALVEOLI The walls are kept moist: alveolus walls secrete a fluid keeps the inner surface moist and allows gases to dissolve They have a very good blood supply: a dense capillary network surrounds the alveoli brings deoxygenated blood from the heart J WERBA – IB BIOLOGY 10

THE ALVEOLI Remember: TRIM 6.4.3 THE ALVEOLI Remember: TRIM Thin lining (single cell layer = less diffusion) Rich capillary network (for gas exchange) Increased SA:Vol ratio (↑ gas exchange) Moist (dissolves gases; prevents collapsing) J WERBA – IB BIOLOGY 11

BREATHING INHALATION EXHALATION diaphragm contracts and flattens 6.4.5 BREATHING INHALATION EXHALATION diaphragm contracts and flattens diaphragm relaxes and curves upwards external intercostal muscles contract, raising ribs internal intercostal muscles contract, lowering ribs volume in thoracic cavity is increased (pressure decreased) volume in thoracic cavity is decreased (pressure increased) pressure in lungs drops below atmospheric pressure pressure in lungs rises above atmospheric pressure air flows into lungs along a pressure gradient air flows out of lungs along a pressure gradient J WERBA – IB BIOLOGY 12

Sample questions Q1 What is the function of the structure labelled X? Gas exchange Ventilation Respiration Inspiration J WERBA – IB BIOLOGY 13

Sample questions Q2 Describe the need for a ventilation system in humans. [2] Q3 Describe the structure of the ventilation system, including the alveoli. [8] J WERBA – IB BIOLOGY 14

Sample questions A1 A A2 most cellular respiration is aerobic/requires oxygen / produces carbon dioxide; ventilation system exchanges gases between inhaled air and lungs/blood stream; ventilation system maintains high concentration gradient of gases in alveoli/lungs; J WERBA – IB BIOLOGY 15

Sample questions A3 ventilation occurs within the lungs; trachea divides to form two bronchi; bronchi divide to form bronchioles; several divisions of bronchioles; alveoli connected to bronchioles; trachea/bronchi/bronchioles/airways lined with cilia/ciliated epithelium; diaphragm and intercostal muscles; trachea/bronchi have rings/c-shaped pieces of cartilage; alveolus is an (air) sac; very small / diameter is (about) 100 μm; many alveoli so large total surface area; wall of alveolus is a single layer of cells; cells in alveolus wall are very thin; surrounded by a network of capillaries; some (larger) cells in the wall secrete fluid/surfactant/natural detergent; Award any of the above points if clearly drawn in a diagram. J WERBA – IB BIOLOGY 16