Alveoli in the Lungs

Key Questions

  • Answer:

    Through diffusion


    Alveoli are specially designed for maximizing the surface area for diffusion process.

    They have thin walls which facilitate diffusion process and are richly supplied with blood capillaries.

    The oxygen which has higher concentration in the alveoli diffuses into the blood capillaries which have lower concentration of oxygen.

    Whereas , the carbon dioxide which has higher concentration in the blood capillaries diffuses into alveoli which have lower concentration of carbon dioxide.

    In this way , exchange of gases takes place in the alveoli.

  • Bronchioles begin with rings and then slivers of cartilage which helps to keep them open. As they become smaller and smaller, the cartilage is replaced by smooth muscle. These smooth muscles regulate how much air comes into the lungs.

    If the sympathetic nervous system stimulates cardiac muscles to increase the heart rate, this causes dilation of the bronchioles of the lungs (increasing oxygen intake) by relaxing the smooth muscle.

    Stretch receptors in the walls of bronchi and bronchioles are activated when the lungs expand to their physical limit. These receptors signal the respiratory center to discontinue stimulation of the inspiratory muscles, allowing expiration to begin as the muscles relax and return to their original size. This response is called the inflation (Hering-Breuer) reflex.

    Problems with relaxation of the smooth muscles can cause problems associated with emphysema and asthma.

    As found in Cliffs Notes and Hole's A&P.

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