Place in the accessory gland system
In the anatomy of the male genital system, it is customary to distinguish three main groups of accessory glands, each contributing to the formation of the ejaculate:
- Paired seminal vesicles (vesiculae seminales).
- Unpaired prostate gland (prostate).
- Paired bulbourethral glands (Cowper's glands).
Anatomy and excretory system
Topographically, the organ is located strictly posterior to the urinary bladder, adjacent to its base. Macroscopically, the vesicle is a highly convoluted 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 will be from 10 to 15 cm.
The secretion excretion system is arranged as follows: the narrowed end of the seminal vesicle merges with the terminal part of the ductus deferens. The result of this fusion is a single ejaculatory duct. Further, this duct is directed inward, passes through the thickness 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 is formed by three clearly distinguishable layers:
- Mucosa (mucous membrane). It features a very complex relief: it forms numerous branched folds. These folds often fuse with each other, giving the surface a characteristic "honeycomb" appearance on cross-section. The lining layer is simple columnar epithelium. Beneath it lies the lamina propria (lamina propria), consisting of loose fibrous connective tissue. An important feature of the lamina propria is the high content of elastic fibers and the presence of alveolar mucous glands.
- Muscular coat. It is represented by two layers of smooth myocytes. The inner layer has a circular direction of 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 characterized by an extremely high content of elastic fibers.
Functional significance
The main task of the seminal vesicles as hollow glandular organs is the secretion of the fluid part of semen. The secretion they produce contains a number of components critical for reproduction:
- Fructose. It acts as the main energy substrate, ensuring the trophic supply (nutrition) of spermatozoa.
- Proteins. First of all, this is seminogelin, which is necessary to give semen its characteristic viscosity.
- Prostaglandins. They are potent biologically active substances that regulate various physiological processes.
Briefly: answers to topical questions
Into which specific section of the urethra does the ejaculatory duct open?
The ejaculatory duct opens into the prostatic part of the urethra.
Features of the formation and topography of the duct:
- Ejaculatory duct (ductus ejaculatorius) — is formed by the fusion of the terminal part of the ductus deferens (ampulla) and the narrowed end of the seminal vesicle.
- The duct penetrates the thickness of the prostate gland.
- Its orifices open on the posterior wall of the prostatic urethra (pars prostatica), located on the sides of the seminal colliculus.
To remember the three key components of the secretion, use the FPS abbreviation: Fructose (nutrition), Prostaglandins (biological activity), Seminogelin (viscosity).
Class and exam questions
Which layers make up the wall of the seminal vesicles?
The wall is formed by three coats: mucosal (with simple columnar epithelium), muscular (two layers of smooth myocytes), and adventitial (dense connective tissue).
Why does the mucosa have a "honeycomb" appearance on a slide?
This appearance is due to the fact that the mucosa forms many branched folds that can fuse with each other, forming a complex network of cells.
How is the ejaculatory duct formed?
It is formed as a result of the fusion of the narrowed excretory end of the seminal vesicle and the terminal part of the ductus deferens.
What else to study on this topic
- Histological structure of the prostate gland
- Structural features of bulbourethral glands
- Spermatogenesis and structure of the epididymis
- Structure and functions of the ductus deferens
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