Anatomy of the Prostate Gland

Understanding Prostate Zones and Lobes

The prostate is a small gland (about the size of a walnut when it has not been enlarged in size by disease) that wraps around the urethra, the tube that carries urine from the bladder to outside the body.

Doctor using digital tablet to talk to older adult man
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While it is small, different areas of the prostate have different functions. Most surgeons attempt to remove only the necessary tissue when performing ​prostate surgery (for benign enlargement, or outflow obstruction) or a biopsy in order to preserve as much function as possible. For known prostate cancer, surgical intervention includes removal of the entire gland of the prostate (called a radical prostatectomy).

When describing the prostate's anatomy, it is divided into both zones and lobes. Your surgeon may refer to a specific zone, a specific lobe, or both when describing your surgery or diagnosis.

Zones of the Prostate

The prostate anatomy can be divided into zones, which are categorized by the function of the prostate tissue. The prostate is made up of the peripheral, central, and transitional zones.

The peripheral zone is the outermost area of the prostate, resting closest to the wall of the rectum. It makes up approximately 70 percent of a healthy prostate gland.

The next layer is the central zone, which is approximately 25 percent of the prostate tissue. This area contains the ejaculatory ducts, which help move semen through the urethra and out of the body.

The transitional zone of the prostate, resting next to the urethra, makes up around 5 percent of the prostate at puberty. This zone continues to increase in size throughout adulthood.

Lobes of the Prostate

The anatomy of the prostate is made up of three lobes: the central lobe and lobes on either side called the anterior lobes.

The central lobe of the prostate is pyramid-shaped and rests between the ejaculatory ducts and the urethra.

The anterior lobes of the prostate rest near the urethra. This tissue is non-glandular, meaning it does not secrete fluids. It is made up of muscle and fibrous tissue.

The Size of the Prostate

A typical prostate is approximately slightly larger than the size of a walnut and weighs about 10-12 grams. Radiation and some treatments for prostate disease can make the prostate smaller than usual, while diseases such as benign prostatic hyperplasia or prostate cancer can make the prostate much larger than usual, as large as 70-100 grams. It is common for men to experience symptoms, including difficulty urinating, when the prostate begins to enlarge. 

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  • Anatomy of the Prostate Gland. The Ohio State University Hospitals.