Anatomy & Physiology

Anatomy & Physiology Study Guide • Fetal hemoglobin has a stronger attraction to oxygen compared to regular adult hemoglobin. This aids in the process of removing the oxygen from the maternal blood. • Aerobic metabolism in peripheral tissues generates CO2. About seven percent of the CO2 transported in blood is dissolved in the plasma, 23 percent is bound as carbaminohemoglobin, and 70 percent is converted to carbonic acid, which dissociates into H+; and HCO –. • Guided by differences in partial pressure, oxygen enters the blood at the lungs and gets left in the peripheral tissues; similar forces drive carbon dioxide into the blood at the muscles and alveoli in the lungs. Respiration is controlled respiratory reflexes, pons, and neurons in the medulla oblongata: Typically, the cellular rates of gas generation and absorption are matched by capillary rates of delivery and removal; and are also identical to the rates of oxygen absorption and carbon dioxide removal at the lungs. An irregularity in these rates causes homeostatic mechanisms to restore equilibrium. • Local factors regulate alveolar blood flow (lung perfusion) and airflow (alveolar ventilation). Alveolar capillaries constrict under conditions of low oxygen, and bronchioles dilate under conditions of high carbon dioxide. • The respiratory centers include three pairs of nuclei in the reticular formation of the pons and medulla oblongata. The respiratory rhythmicity centers set the pace for respiration; the apneustic centers cause strong, sustained inspiratory movements; and the pneumotaxic centers inhibit the apneustic centers and promote exhalation. • Stimulation of the chemoreceptor reflexes is based on the level of carbon dioxide in the blood and CSF. The inflation reflex prevents overexpansion of the lungs during forced breathing. The deflation reflex stimulates inhalation when the lungs are collapsing. • Before delivery, the fetal lungs are filled with body fluids and collapsed. At the first breath, the lungs inflate and do not collapse entirely after that. • Conscious and unconscious thought processes can affect respiration by affecting the respiratory centers. The respiratory system provides oxygen to the lungs and eliminates carbon dioxide from, other organ systems. Respiratory performance declines with age: • The respiratory system is less efficient in the elderly because elastic tissue deteriorates, lowering the vital capacity of the lungs; movements of the chest are restricted by arthritic changes and decreased flexibility of costal cartilages, and some degree of emphysema is present.

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