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  2. Tracheid - Wikipedia

    en.wikipedia.org/wiki/Tracheid

    In radial section, two tracheids of a coniferous wood species are shown. A series of bordered pits are also appearing in each tracheid. A tracheid of oak shows pits along the walls. It has no perforation plates. Angiosperms have both tracheids and vessel elements. [1] A tracheid is a long and tapered lignified cell in the xylem of vascular ...

  3. Respiratory system - Wikipedia

    en.wikipedia.org/wiki/Respiratory_system

    The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies greatly, depending on the size of the organism, the environment in which it lives and its evolutionary ...

  4. Breathing - Wikipedia

    en.wikipedia.org/wiki/Breathing

    The breathing of all vertebrates with lungs consists of repetitive cycles of inhalation and exhalation through a highly branched system of tubes or airways which lead from the nose to the alveoli. [4] The number of respiratory cycles per minute is the breathing or respiratory rate, and is one of the four primary vital signs of life. [5]

  5. Lung - Wikipedia

    en.wikipedia.org/wiki/Lung

    The lower respiratory tract is part of the respiratory system, and consists of the trachea and the structures below this including the lungs. [32] The trachea receives air from the pharynx and travels down to a place where it splits (the carina) into a right and left primary bronchus.

  6. Air sac - Wikipedia

    en.wikipedia.org/wiki/Air_sac

    Diagram showing the general layout of air sacs in a bird. Birds have a system of air sacs in their ventilation system. [2] The air sacs work to produce a unidirectional flow where air enters and exits the lung at the same rate, contrasting the lungs of other tetrapods such as mammals where air enters and exits the lung in a tidal ventilation. [2]

  7. Head and neck anatomy - Wikipedia

    en.wikipedia.org/wiki/Head_and_neck_anatomy

    The respiratory system involving the head and neck includes: the nasal cavity for filtering, moistening, and warming the air; the pharynx or throat which is the combining point for respiratory and digestive system; the larynx or voice box containing the epiglottis; the trachea, or windpipe; These lead down into the lower respiratory tract.

  8. Respiratory tract - Wikipedia

    en.wikipedia.org/wiki/Respiratory_tract

    The lungs can be included in the lower respiratory tract or as separate entity and include the respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli. [3] Adult and pediatric airway anatomy. The respiratory tract can also be divided into a conducting zone and a respiratory zone, based on the distinction of transporting gases or ...

  9. Respiratory center - Wikipedia

    en.wikipedia.org/wiki/Respiratory_center

    The respiratory center is made up of three major respiratory groups of neurons, two in the medulla and one in the pons. In the medulla they are the dorsal respiratory group, and the ventral respiratory group. In the pons, the pontine respiratory group includes two areas known as the pneumotaxic center and the apneustic center.