The upper part of the prostate is called the base. It rests against the lower part (neck) of the bladder. The lower, narrowed part of the prostate is called the apex. The prostate is divided into a right lobe and a left lobe.
The prostate is made up of many branching ducts surrounded by the stroma. The stroma is made up of connective tissue and muscle fibres. The cells that line the ducts make prostatic fluid, which is mixed with sperm and other fluid to make semen. Most of the prostate is covered by a thin layer of connective tissue called the capsule. The apex of the prostate is covered by the anterior fibromuscular stroma, which is made up of muscle fibres and connective tissue.
The seminal vesicles are glands found on each side of the prostate. They make most of the fluid in semen. The seminal vesicles are sometimes removed during surgery to remove the prostate (called a radical prostatectomy).
The main function of the prostate is to make prostatic fluid. Prostatic fluid is rich in enzymes, proteins and minerals that help protect and nourish sperm. When a man is sexually aroused, the prostate pushes prostatic fluid through the ducts and into the urethra. Prostatic fluid mixes with sperm and other fluids in the urethra and is ejaculated as semen.
Hormones, including testosterone and those made by the pituitary gland and adrenal glands, help control the function of the prostate gland.
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