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The seminal vesicle, a crucial component of the male reproductive system, plays a vital role in fertility and sexual function. This small, glandular organ, located near the prostate, has a significant impact on the production and quality of semen. Understanding the seminal vesicle’s function and anatomy is essential for anyone interested in male reproductive health or those facing related medical concerns.
This article delves into the various aspects of the seminal vesicle, covering its physiological role, anatomical relationships, and potential pathological conditions. We’ll explore what the seminal vesicle does, where it’s located, and how it interacts with other reproductive organs like the prostate gland. Additionally, we’ll discuss seminal vesicle secretion, the organ’s histology, and common issues such as cysts and inflammation. By the end, readers will have a comprehensive understanding of this often-overlooked but crucial part of male reproductive anatomy.
Physiological Role of Seminal Vesicles
Production of Seminal Fluid
The seminal vesicles, a pair of sac-like glands located within the male pelvis, have a significant role in the production of seminal fluid. These glands are responsible for generating approximately 70% of the total semen volume, which typically ranges from 1.5 to 2 ml of the 3 ml ejaculate volume. The fluid produced by the seminal vesicles combines with sperm cells and additional fluids from the prostate to form semen.
Regulation of Sperm Function
The seminal fluid produced by the vesicles has an essential impact on sperm function and survival. It contains several key components:
- Fructose: This sugar provides energy for sperm motility.
- Alkaline fluid: It helps neutralize the acidic environment of the male urethra and female vagina.
- Proteins: Substances like semenogelin form a protective gel-like layer around sperm.
- Phosphorus and potassium: These elements aid in sperm movement.
- Prostaglandins: These hormones lower the female immune response to semen.
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Impact on Fertility
The seminal vesicles have a significant influence on male fertility. Studies have shown that surgical removal of seminal vesicles in male mice and rats results in severe subfertility. The secretions from these glands contribute to the formation of the copulatory plug, which is crucial for preventing semen leakage from the vagina and ensuring an adequate number of sperm reach the uterus. Additionally, seminal vesicle secretions may improve sperm fertilization rates, particularly when low sperm numbers are present.
Anatomical Relationships
Position Relative to Other Organs
The seminal vesicles are located in the male pelvis, positioned behind the bladder and in front of the rectum. These glandular structures, approximately 5 cm long, are separated from the rectum by the rectovesicle pouch and the rectoprostatic fascia. The seminal vesicles have a close anatomical relationship with the vas deferens, which combines with the duct of the seminal vesicles to form the ejaculatory duct. This duct then drains into the prostatic urethra.
Vascular Supply
The blood supply to the seminal vesicles comes from multiple sources. The arteries supplying these glands are derived from the inferior vesical, internal pudendal, and middle rectal arteries, all of which originate from the internal iliac artery. Venous drainage occurs via the vesical venous plexus, which ultimately empties into the internal iliac veins. The lymphatic drainage follows a similar path, draining to both the internal and external iliac lymph nodes.
Innervation
The innervation of the seminal vesicles is primarily sympathetic in origin. This nervous supply comes from the hypogastric nerves and the inferior hypogastric plexus. In males, the prostatic plexus, which is derived from the inferior hypogastric plexus, plays a role in this innervation. The sympathetic innervation has an impact on the ejaculation process, including the contraction of the smooth muscle of the seminal vesicles.
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Pathological Conditions
Infections and Inflammation
Seminal vesiculitis, an uncommon condition characterized by inflammation of the seminal vesicles, can occur due to bacterial infections. This condition often accompanies infections elsewhere in the male genital tract, forming part of the spectrum of male accessory gland inflammation. Organisms that cause urethritis, chronic prostatitis, or acute epididymitis may also contribute to vesiculitis. In regions where tuberculosis and schistosomiasis are prevalent, these diseases can lead to chronic forms of vesiculitis. Treatment typically involves the use of antibiotics to address the underlying infection.
Congenital Abnormalities
Congenital anomalies of the seminal vesicles include agenesis, hypoplasia, duplication, fusion, and cysts. Seminal vesicle agenesis, a rare condition with an incidence of 0.08%, can be unilateral or bilateral. Bilateral agenesis is often associated with cystic fibrosis and mutations in the cystic fibrosis transmembrane conductance regulator gene. Unilateral agenesis frequently occurs with ipsilateral renal agenesis. Hypoplasia refers to underdevelopment of the seminal vesicles and is usually associated with other genitourinary anomalies. Seminal vesicle cysts, which can be acquired or congenital, have an incidence of 0.005% and are often associated with ipsilateral renal anomalies.
Neoplasms
Tumors of the seminal vesicles are rare, with primary malignancies being extremely uncommon. Most tumors in this region represent secondary spread from adjacent organs, particularly the prostate. Adenocarcinoma is the most common primary malignancy of the seminal vesicles. Other rare primary tumors include cystadenoma, mixed epithelial-stromal tumors, and various mesenchymal tumors such as leiomyosarcoma and angiosarcoma. Secondary involvement is more common, usually occurring through local invasion from prostate, bladder, or rectal carcinomas. Distant metastases to the seminal vesicles, though rare, have been reported from various primary sites including melanoma, renal cell carcinoma, and testicular tumors.
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Conclusion
The seminal vesicle plays a crucial role in male reproductive health, having a significant impact on fertility and sexual function. Its main job is to produce most of the seminal fluid, which helps sperm survive and move. The organ’s close ties with other parts of the reproductive system, like the prostate and vas deferens, highlight its importance in the complex process of reproduction. Understanding how the seminal vesicle works can help doctors better diagnose and treat issues related to male fertility.
While problems with the seminal vesicle aren’t common, they can have serious effects when they do occur. Infections, birth defects, and tumors can all affect how well this organ works. Keeping an eye on seminal vesicle health is key to maintaining overall reproductive wellbeing. As research continues, we’re likely to gain even more insights into how this small but mighty organ influences male fertility and sexual health.
FAQs
What do you need to know about seminal vesicles?
Seminal vesicles, also referred to as seminal glands or vesicular glands, are crucial components of the male reproductive system in individuals assigned male at birth. These small glands are primarily responsible for producing most of the fluid found in semen. However, they do not participate in sperm production, which occurs in the testicles.
Why are seminal vesicles clinically significant?
Clinically, the seminal vesicles, also known as vesicular or seminal glands, are essential because they produce many of the components found in semen. They are located in the male pelvis and contribute to about 70% of semen’s total volume.
What is responsible for producing 70% of seminal fluid?
The seminal vesicles are the main producers of seminal fluid, accounting for about 70% of its volume. These glands also produce fructose in the semen, which serves as an energy source for spermatozoa.
What is the significance of seminal vesicle secretions?
The secretions from the seminal vesicles are highly significant due to their composition and function. The fluid is viscous and rich in fructose, which fuels the sperm, prostaglandins that enhance sperm mobility and viability, and proteins that facilitate a mild coagulation reaction in semen after ejaculation.
