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IB objective 6.4 Pgs Campbell

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1 IB objective 6.4 Pgs. 889-897 Campbell
Gas Exchange IB objective 6.4 Pgs Campbell

2 Gaseous exchange in animals
Gaseous exchange is the exchange of gases between an organism and its surroundings Intake of oxygen and release of carbon dioxide This exchange takes place by diffusion Three factors determine the rate: 1. the size of the surface area 2. difference in concentration 3. length of the diffusion path Therefore, thin surfaces

3 For many reasons … Mammals have lungs Ventilation system:
Specialized organs for gas exchange Large, thin surface Protected by the thorax (chest) Must be ventilated Ventilation system: Pumping mechanism that moves air into and out of the lungs Maintains concentration gradient for diffusion Blood circulation system Respiratory pigment (hemoglobin)

4 The working lungs Lungs are housed in the thorax Airtight
Lined by the pleural membrane Secretes pleural fluid which protects the lungs from friction Formed by the rib cage and its muscles (intercostal muscles) and the diaphragm (floor) Separates the abdomen from the thorax

5 The working lungs The lungs connect with the pharynx at the rear of the mouth by the trachea Air reaches the trachea from the mouth and nose, passes through the larynx Glottis Epiglottis The trachea has incomplete rings of cartilage which prevent collapse under pressure from food

6 The working lungs The trachea then divides into two bronchi (one to each lung) Smooth muscle and cartilage rings The finest bronchioles end in air sacs (alveoli)

7 The structure of the thorax

8 Alveoli

9 Alveoli

10 How we breath (ventilation)
Air is drawn into the alveoli when air pressure in the lungs is lower than atmospheric pressure Air is forced out when pressure is higher than atmospheric pressure Since the thorax is air tight, pressure changes in the lungs occurs when the volume of the thorax changes

11 Ventilation The volume of the thorax is increased when:
The ribs are moved up and out The diaphragm is lowered Contraction of diaphragm The volume of the thorax is decreased when: Muscles relax Diaphragm is more dome-shaped Ribs move down and in

12 Inspiration vs. expiration
Inspiration (inhalation) Structure/outcome Expiration (exhalation) Muscles contract, flattening of diaphragm Diaphragm Muscles relax, pressure form abdomen pushes up Contract, rib cage up and out External intercostal muscle Relax Internal intercostal muscle Contract, moves rib cage down and in Increases Volume of thorax cavity Decreases Falls below atmospheric pressure Air pressure of thorax Rises above atmospheric pressure In Air flow Out

13 Ventilation

14 Alveolar structure Arranged in clusters Served by tiny bronchiole
Elastic connective tissue in their walls Capillary system wraps around the clusters Each capillary is connected to a branch of the pulmonary artery and is drained by a branch of the pulmonary vein Pulmonary circulation Supplied with deoxygenated blood from the right side of the heart Returns oxygenated blood to the left side of the heart to be pumped to the rest of the body

15 Alveoli

16 Why are lungs are so efficient
Feature Effects and consequences Surface area of alveoli Huge; 700 million alveoli in our lungs (70 m2) Wall of alveoli Very thin, flattened epithelium; diffusion pathway is very short Capillary supply to alveoli Network of capillaries; maintains concentration gradient of O2 and CO2 Surface film of moisture O2 dissolves in water lining the alveoli; O2 diffuses into the blood

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