Upper and Lower Respiratory System Quiz

Upper Respiratory System

• The pharynx is a chamber shared by the digestive and respiratory systems.
• It extends between the choanae and the entrances to the larynx and esophagus.
• It is divided into three regions:
  • Nasopharynx: The superior portion of the pharynx, containing the pharyngeal tonsil and the pharyngeal openings of the auditory tubes.
  • Oropharynx: Connects directly to the oral cavity.
  • Laryngopharynx: The inferior portion of the pharynx, located between the hyoid bone and the entrance to the larynx and esophagus.

Lower Respiratory System

• Air flows from the pharynx to the larynx through the glottis, a slit-like opening between the vocal cords.
• The larynx is formed by three large unpaired cartilages:
  • Thyroid cartilage
  • Cricoid cartilage
  • Epiglottis
• There are also three pairs of smaller paired hyaline cartilages in the larynx:
  • Arytenoid cartilage
  • Corniculate cartilage
  • Cuneiform cartilage
• Each segmental bronchus branches into multiple bronchioles, which further branch into terminal bronchioles.
• Each segmental bronchus forms about 6500 terminal bronchioles.
• Bronchioles do not have cartilage and are dominated by smooth muscle.
• The autonomic nervous system controls the luminal diameter of bronchioles by regulating smooth muscle.
  • Bronchodilation: Enlarges the luminal diameter of the airway, caused by sympathetic activation, reducing resistance to airflow.
  • Bronchoconstriction: Reduces the luminal diameter of the airway, caused by parasympathetic activation and histamine release during allergic reactions.

Gas Exchange Structures

• Each terminal bronchiole branches to form several respiratory bronchioles.
• Respiratory bronchioles are connected to alveoli along alveolar ducts.
• Alveolar ducts end at alveolar sacs, common chambers connected to many individual alveoli.
• Each alveolus has an extensive network of capillaries surrounded by elastic fibers.

The Lungs

• Blood pressure in the pulmonary circuit is lower than in the systemic circuit.
• Pulmonary vessels are easily blocked by blood clots, fat, or air bubbles.
• Pulmonary embolism is a blocked branch of the pulmonary artery that stops blood flow to lobules or alveoli.
• There are two pleural cavities separated by the mediastinum.
• Each pleural cavity contains a lung lined with a serous membrane called the pleura.
• The pleura consists of two layers:
  • Parietal pleura: Lines the inner surface of the thoracic wall.
  • Visceral pleura: Covers the outer surfaces of the lungs.
• Pleural fluid lubricates the space between the two layers.

External and Internal Respiration

• Respiration involves two integrated processes:
  • External respiration: All processes involved in the exchange of oxygen and carbon dioxide with the external environment.
  • Internal respiration: Uptake of oxygen and release of carbon dioxide by cells, resulting from cellular respiration.
• External respiration includes the following steps:
  • Pulmonary ventilation (breathing).
  • Gas diffusion across the blood-air barrier in the lungs and across capillary walls in other tissues.
  • Transport of oxygen and carbon dioxide between alveolar capillaries and capillary beds in other tissues.

Pulmonary Ventilation

• The primary respiratory muscles are the diaphragm and external intercostal muscles.
• Accessory respiratory muscles are activated when respiration increases significantly.
• Inhalation is always active, while exhalation can be active or passive.
• Muscles involved in inhalation:
  • Diaphragm: Contraction draws air into the lungs, contributing 75% of normal air movement.
  • External intercostal muscles: Assist inhalation, contributing 25% of normal air movement.
  • Accessory muscles: Assist in elevating the ribs, including the sternocleidomastoid, scalenes, pectoralis minor, and serratus anterior.
• Muscles involved in exhalation:
  • Internal intercostal muscle and transversus thoracis: Depress the ribs.
  • Abdominal muscles: Compress the abdomen, forcing the diaphragm upward.

Gas Transport

• The Bohr effect describes the effect of pH on the hemoglobin saturation curve, caused by CO2.
  • CO2 diffuses into red blood cells, where carbonic anhydrase catalyzes its reaction with H2O, producing carbonic acid (H2CO3).
  • Carbonic acid dissociates into hydrogen ion (H+) and bicarbonate ion (HCO3–).
  • Hydrogen ions diffuse out of red blood cells, lowering pH.