Collecting tubule

Collecting Tubule

The collecting tubule is a vital component of the kidney's nephron, playing a crucial role in the body's fluid and electrolyte balance. It is part of the renal tubule system, which also includes the proximal convoluted tubule, the loop of Henle, and the distal convoluted tubule. The collecting tubule is responsible for the final modification of urine before it is conveyed to the renal pelvis.

Structure

The collecting tubule is composed of two main types of cells: principal cells and intercalated cells. Principal cells are primarily involved in the reabsorption of water and sodium ions, as well as the secretion of potassium ions. This process is regulated by hormones such as aldosterone and antidiuretic hormone (ADH). Intercalated cells, on the other hand, play a role in the regulation of the acid-base balance through the secretion of hydrogen ions and the reabsorption of bicarbonate ions.

Function

The primary function of the collecting tubule is to concentrate urine and regulate its composition. This is achieved through the selective reabsorption of water and solutes, a process that is tightly regulated by several hormones. The collecting tubule is also involved in the regulation of blood pressure through the renin-angiotensin-aldosterone system and the maintenance of acid-base balance.

Pathophysiology

Dysfunction of the collecting tubule can lead to a variety of renal disorders, including diabetes insipidus, which is characterized by the inability to concentrate urine, leading to excessive urination and thirst. Other conditions, such as renal tubular acidosis, involve the improper acidification of urine due to the malfunction of intercalated cells.

Clinical Significance

Understanding the function and pathology of the collecting tubule is essential for the diagnosis and treatment of various kidney diseases. It is also a target for several diuretic drugs that act to increase urine output by inhibiting sodium and water reabsorption in this segment of the nephron.