Which letter indicates a P wave?

The image illustrates the hypothalamic-pituitary-endocrine organ axis. Letter Apoints to the mammary gland (breast tissue), which is the target organ for milk production. The hormone at A is Prolactin (PRL). The hormone pathway originates from the pituitary gland. The line labeled Apoints directly to the mammary gland. The hormone responsible for stimulating milk production in the mammary glands is Prolactin (PRL), which is secreted by the anterior pituitary gland.

A. Squamous alveolar cells:Squamous alveolar cells (type I pneumocytes) form the thin lining of alveoli to facilitate gas exchange. They do not produce mucus and are not involved in air cleansing.

B. Goblet cells:Goblet cells are specialized epithelial cells found in the respiratory tract that secrete mucus. This mucus traps dust, pathogens, and other particles in inhaled air, playing a critical role in respiratory defense.

C. Great alveolar cells:Great alveolar cells (type II pneumocytes) secrete pulmonary surfactant to reduce alveolar surface tension. They do not produce mucus or participate directly in cleansing inhaled air.

D. Ciliated cells:Ciliated epithelial cells help move mucus along the respiratory tract through coordinated beating of cilia, but they do not secrete mucus themselves.

E. The pleurae:The pleurae are membranes surrounding the lungs and lining the thoracic cavity. They produce pleural fluid to reduce friction during breathing but do not produce mucus.