Lecture 22.1 Respiratory Anatomy and Function PDF

Four processes of the respiratory system The four processes required for the appropriate saturation of blood with oxygen and appropriate perfusion of the body’s tissues include: ventilation, external respiration, transport, and internal respiration. 1. Ventilation:...

Four processes of the respiratory system The four processes required for the appropriate saturation of blood with oxygen and appropriate perfusion of the body’s tissues include: ventilation, external respiration, transport, and internal respiration. 1. Ventilation: This includes the rate at which we move air in rate and volume and out of the lungs and the volume of each breath.This is measured as the respiratory minute volume. 2. External respiration: This describes the transport of the transport of gas across resp respiratory gasses in and out of the blood across the membranes respiratory membrane. It is also referred to as alveolar ventilation. 3. Transport: This describes the rate at which we transport rate of blood blood around the body; it is a product of cardiac output. However, cardiac output and ventilation must be appropriately matched. 4. Internal respiration: This describes the transport of the transport of respiratory gasses into and out of the tissues. This ensures o2 blood to cells have an adequate supply of oxygen to perform cellular tissues respiration. Lung anatomy The respiratory system includes the passageways beginning at the external nares and progressing through the nasal cavity, larynx, and trachea all the way to the alveoli. The lungs sit inside separate pleural cavities in the thoracic cavity, separated by the mediastinum. Airways, unlike the passageways of the GI tract, must remain open; this ensures airway resistance is minimized. For this reason, the structures of the respiratory system, starting at the larynx, use cartilage to remain open. The respiratory system is divided into two major systems: 1) the conducting zone, which directs, moistens, and filters the air, and 2) the respiratory zone, which ensures gas exchange between atmospheric air and pulmonary blood. The conducting zone begins at the external nares, and includes the nasal cavity, pharynx, larynx, trachea, primary, secondary, and tertiary bronchi, bronchioles, and terminal bronchioles. The respiratory zone includes the respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli. The majority (70%) of gas exchange occurs in the alveoli, and the rest in the respiratory bronchioles, alveolar ducts, and alveolar sacs; no gas exchange occurs in the structures of the conducting zone. 1  smaller distance + efficient gas exchange Respiratory membrane The respiratory membrane lines the internal surface of the alveoli and must remain as thin as possible to maximize the efficiency of gas exchange. This is because oxygen and carbon dioxide must diffuse across this membrane, and diffusion is only an efficient mode of molecular transport over very short distances. For example, when air reaches the alveoli, oxygen diffuses across three layers: 1. The type 1 pneumocytes; these are organized as a simple squamous epithelium to minimize diffusion distances. 2. A thin, fused basement membrane; this is a shared basement membrane between the type1 pneumocytes and the underlying endothelial cells. 3. The endothelial cell of a pulmonary capillaries; these are also organized as a simple squamous epithelium. Also lining the respiratory membrane on the alveolar side are the cuboidal type 2 pneumocytes; these are responsible for producing surfactant, which prevents the alveoli from collapsing. Additionally, macrophages monitor the alveoli and phagocytose microbes and particulates that evade filtration along the conducting zone. Partial pressure Partial pressure describes the proportion (or concentration) of a component molecule in a gas. Atmospheric pressure measures 760 mmHg and is the combined concentrations of the most prominent gasses in the air we breathe: nitrogen (N2; 597 mmHg), oxygen (O2; 159 mmHg), water vapor (H2O; 4 mmHg), and carbon dioxide (CO2;