Explain/describe the mechanism of gaseous exchange in a frog.

a)Buccal/ mouth cavity
Inhalation/breathing in/inspiration.
-The mouth floor is lowered; increasing the volume in the mouth cavity; and decreasing pressure; The air in the atmosphere flows into the mouth cavity through the nostrils;
-The concentration of oxygen is higher in inhaled air; hence it diffuses into blood capillaries across the lining of the mouth cavity; and is carried by haemoglobin to all parts of the body.
-Carbon (IV) oxide which is higher in concentration in blood; diffuses into the mouth cavity through the lining;
Exhalation/expiration/breathing out.
-The floor of the mouth is raised; decreasing the volume in the mouth cavity; and increasing pressure; Air is forced out of mouth cavity into the atmosphere through the nostril;
b)LUNGS.
Inhalation/breathing in/inspiration.
-The floor of the mouth is lowered causing the nostrils to open; The volume of the mouth cavity increases; decreasing pressure;
-Air rushes in through the nostrils into the mouth cavity; When air is in the mouth, the nostrils close;
-The floor of the mouth cavity is raised; This reduces the volume; but increases pressure in the mouth; Air is forced into the lungs;
-Oxygen which is at higher concentration in the inspired air than in blood; It dissolves into the moist lining of the alveoli and diffuses across the wall of capillaries; into blood and transported to all parts of the body by haemoglobin.
-Carbon (IV) oxide is in higher concentration blood than alveolar cavity hence it diffuses across the wall of capillaries into alveoli;
Exhalation/expiration/breathing out
-The nostrils and the mouth remain closed and the floor of the mouth is lowered; this increases the volume of the mouth cavity; but decreases pressure; this forces air from the lungs to the mouth cavity.
 The mouth floor is raised and the nostrils are opened; this decreases the volume; of the mouth cavity increasing pressure; this forces air out through the nostrils;
c)Skin
-Oxygen is at a higher concentration in the atmosphere/ water than in the blood; it diffuses from the atmosphere/ water into the blood capillaries through the moist skin;
-Carbon (IV) oxide is at a higher concentration in the blood of the frog than in the atmosphere/ water; it diffuses from the blood into water/ atmosphere through the moist skin;