The capillaries and lymphatics that transport nutrients absorbed across the wall of the GI organs lie in the

A. It promotes vasoconstriction of blood vessels:Angiotensin II (RAAS mediator) is a potent vasoconstrictor, raising systemic vascular resistance and affecting renal blood flow.
B. It stimulates thirst:Angiotensin II acts on the brain (hypothalamus) to stimulate thirst and ADH release, promoting fluid intake and retention.
C. It lowers blood pressure:RAAS activation raises blood pressure by vasoconstriction and increased sodium/water retention.
D. It increases water reabsorption in the kidneys:Aldosterone promotes Na⁺ reabsorption (water follows), and angiotensin II/ADH actions lead to increased water retention—overall increasing water reabsorption.
E. It stimulates the release of renin:Renin release is the initiating step of RAAS activation (triggered by low renal perfusion); once RAAS is active, angiotensin II typically provides negative feedback that suppresses further renin release rather than stimulating it.

A. Produce surfactant for the alveoli: Surfactant is produced by type II pneumocytes in the alveoli, not by tracheal cartilage.
B. Move mucus towards the alveoli using their cilia: Mucus is moved by ciliated epithelium (mucociliary escalator), not by cartilage rings.
C. Perform external respiration between air and blood: Gas exchange (external respiration) occurs in alveoli, not at the trachea.
D. Allow the trachea to always remain open for passage of air: The C-shaped cartilage rings provide rigid structural support and prevent tracheal collapse while allowing the posterior tracheal wall to flex -this maintains an open airway.