Organ
Transition zone of the prostate
Glandular tissue beside the proximal prostatic urethra
High-yield
Benign prostatic hyperplasia develops mainly in the transition and neighboring periurethral regions. Its relationship to the urethra helps explain obstruction, although smooth-muscle tone and bladder function also influence symptoms.
Overview
The transition zone forms paired glandular regions beside the urethra above the seminal colliculus. Small in a young prostate, it can expand substantially with benign prostatic hyperplasia. Enlargement changes the shape of the surrounding zones and bladder outlet, but tissue size alone does not determine urinary symptoms.
Reference facts
- Location
- It lies on either side of the proximal prostatic urethra, mainly above the seminal colliculus and behind the anterior fibromuscular stroma.
- Parts
- Two glandular regions flank the urethra. Adjacent periurethral glands are a related but separately described component of the zonal anatomy.
- Blood supply
- Branches of the prostatic arterial network enter near the bladder outlet and distribute through the inner gland; their origins and branching vary.
- Innervation
- The prostatic autonomic plexus supplies the gland and its smooth muscle. Adrenergic activity contributes to outlet tone as well as glandular size contributing to resistance.
- Venous/Lymphatic drainage
- Blood drains through the prostatic venous plexus. Lymph enters communicating pelvic nodal pathways, including iliac and obturator groups.
- Relations
- With hyperplasia, expanding inner tissue compresses surrounding tissue and can create an apparent surgical capsule, a boundary distinct from the outer prostatic covering.
- Function
- Its glands contribute prostatic fluid to semen; age-associated stromal and glandular growth makes this region important in benign outlet obstruction.
Clinical correlation
Procedures for benign obstruction can remove enlarged inner tissue while leaving much of the remaining prostate. Prostate cancer can therefore still arise afterward, including in residual peripheral tissue. The transition zone itself is also a possible site of carcinoma.
Frequently asked questions
Where is the transition zone of the prostate located?
It lies on either side of the proximal prostatic urethra, mainly above the seminal colliculus and behind the anterior fibromuscular stroma.
What does the transition zone of the prostate do?
Its glands contribute prostatic fluid to semen; age-associated stromal and glandular growth makes this region important in benign outlet obstruction.
What are the parts of the transition zone of the prostate?
Two glandular regions flank the urethra. Adjacent periurethral glands are a related but separately described component of the zonal anatomy.
What is the blood supply of the transition zone of the prostate?
Branches of the prostatic arterial network enter near the bladder outlet and distribute through the inner gland; their origins and branching vary.