Role in the Accessory Gland System
In male reproductive system anatomy, three main groups of accessory glands contribute to the formation of the ejaculate:
- Paired seminal vesicles (vesiculae seminales).
- Unpaired prostate gland (prostate).
- Paired bulbourethral glands (Cowper's glands).
Anatomy and Duct System
Topographically, the organ is located strictly posterior to the urinary bladder, adjacent to its base. Macroscopically, the seminal vesicle is a highly coiled tube with a narrowed end. Due to its tortuosity in its natural state, the organ reaches a length of about 5 cm. However, if this tube is isolated and fully straightened, its length ranges from 10 to 15 cm.
The secretion drainage system is arranged as follows: the narrowed end of the seminal vesicle merges with the terminal part of the ductus deferens. This fusion forms a single ejaculatory duct. This duct then travels inward, passes through the substance of the prostate gland, and opens directly into the urethra.
Histological Structure of the Wall
At the microscopic level, the wall of the seminal vesicle consists of three well-defined layers:
- Mucosa. Characterized by a very complex relief: it forms numerous branching folds. These folds frequently fuse with one another, giving the surface a characteristic "honeycomb" appearance in cross-section. The lining layer is a simple columnar epithelium. Beneath it lies the lamina propria, consisting of loose fibrous connective tissue. An important feature of the lamina propria is its high content of elastic fibers and the presence of alveolar mucous glands.
- Muscular layer. Composed of two layers of smooth myocytes. The inner layer has circularly arranged bundles, and the outer layer is longitudinal.
- Adventitia. The outer layer of the wall is formed by dense fibrous connective tissue. Like the lamina propria of the mucosa, the adventitia is extremely rich in elastic fibers.
Functional Significance
The primary role of the seminal vesicles as hollow glandular organs is the secretion of the fluid component of semen. Their secretion contains several components critical for reproduction:
- Fructose. Acts as the primary energy substrate, providing trophic support (nutrition) for spermatozoa.
- Proteins. Primarily seminogelin, which is necessary to give semen its characteristic viscosity.
- Prostaglandins. Powerful biologically active substances that regulate various physiological processes.