Anatomy & Physiology

Anatomy & Physiology Study Guide The lungs, surrounded by a pleural membrane, are paired organs containing alveoli, which permit gaseous exchange: • The right lung is separated into three lobes, and the left into two by fissures. • The anterior and lateral surfaces of the lungs follow the inner curvature of the rib cage. The cardiac notch, the concavity of the medial surface of the left lung, conforms to the shape of the pericardium. • The bronchial tree is formed by the primary bronchi and their branches. Secondary and tertiary bronchi are branches within the lungs. Cartilage levels in their walls decrease as they branch and the quantity of smooth muscle increases. • Each tertiary bronchus supplies air to a single bronchopulmonary segment. • Within bronchopulmonary segments, there are bronchioles which eventually branch into terminal bronchioles which then branch into respiratory bronchioles. Each terminal bronchiole delivers air to a single pulmonary lobule. The connective tissues of the root of the lung extend into the parenchyma of the lung as a series of trabeculae (partitions) that branch to form interlobular septa, which divide the lung into lobules. • The respiratory bronchioles open into alveolar ducts, at each of which many alveoli are interconnected. The respiratory exchange surfaces are extensively connected to the circulatory system via the vessels of the pulmonary circuit. • The respiratory membrane consists of simple squamous epithelium, the endothelial cell lining an adjacent capillary, and the fused basal laminae; pneumocytes type II (septal cells) scattered in the respiratory membrane produce surfactant that keeps the alveoli from collapsing. Alveolar macrophages patrol the epithelium and engulf foreign particles. • Each lung occupies a single pleural cavity lined by a pleura (serous membrane). The two types of pleurae are the parietal pleura, covering the inner surface of the thoracic wall, and the visceral pleura, covering the lungs. • The regulating portions of the respiratory tract receive blood from the bronchial arteries, external carotid arteries, and the thyrocervical trunks. Venous blood flows into the pulmonary veins, bypassing the rest of the systemic circuit and diluting the oxygenated blood leaving the alveoli. Gaseous exchange within the body is allowed due to external and internal respiration: • Respiratory physiology centers in on a series of integrated processes. External respiration is the transfer of oxygen and carbon dioxide between interstitial fluid and the external environment; while internal respiration is the exchange of oxygen and carbon, The exchange of oxygen and carbon dioxide between interstitial fluid and the external environment is external respiration (includes pulmonary ventilation, aka breathing), and internal respiration when those same gases are exchanged between interstitial fluid and cells. A decline in oxygen levels affect tissues causing hypoxia, and if oxygen is completely shut off, then the tissue dies as a result of anoxia.

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