the mammalian gaseous exchange system

Question 1

inspiration

Answer 1

• an energy using process
• diaphragm contracts, flattening and lowering. The external intercostal muscles contract moving the ribs upwards and outwards.
• the volume of the thorax increases so the pressure is reduced
• it is lower than the atmospheric air, so air is drawn in.
• equalizes the pressures inside and outside the chest.

Question 2

expiration

Answer 2

• a passive process
• diaphragm relaxes and moves up to its resting domed shape. The external intercostal muscles relax so ribs move down and inwards. The elastic fibers in the alveoli move to their normal length.
• decreases volume in the thorax increasing the pressure, now the pressure inside the thorax is greater than the pressure in the atmospheric air
• drawing air out until pressure is equal again.
• you can exhale forcibly using energy

Question 3

ventilating the lungs

Answer 3

• air is moved in and out of the lungs as a result of pressure changes in the thorax, this happens because of the breathing movements. This is called ventilation.
• the rib cage provides a semi-rigid case which pressure can be lowered

Question 4

trachea

Answer 4

• the main airway that carries warm moist air from the nose down to the chest.
• supported by incomplete rings of strong flexible cartilage which stop the trachea from collapsing.
• rings are incomplete so food can move easily down behind the trachea.
• lined with ciliated epithelium with goblet cells between them. Goblet cells secret mucus to trap microorganisms and dust.

Question 6

bronchioles

Answer 6

• bronchi divide to form many bronchioles.
• smaller bronchioles have no cartilage rings.
• contain smooth muscle, when muscle contracts, the bronchioles close up, when it relaxes the bronchioles dilate. this changes the amount of air that can reach the lungs.
• Layered with flattened epithelium, making some gaseous exchange possible.

Question 7

alveoli

Answer 7

• tiny air sacs which are the main gas exchange surfaces of the body.
• each alveoli has a diameter of around 200-300um and consists of a layer of thin flattened epithelial cells along with collagen and elastic fibers.
• these elastic tissues allow the alveoli to stretch as air is drawn in, when they return to resting size they help squeeze air out ( know as the elastic recoil of the lungs)