Yes, horses possess a penis, and the male horse capable of reproduction is called a stallion. When a stallion is relaxed or at rest, the organ is typically not visible, as it is housed entirely inside a protective sheath. This design keeps the majority of the penis safe within the body cavity until it is needed for urination or breeding.
Anatomy of the Equine Organ
The non-erect organ consists of three primary anatomical regions: the root, the body or shaft, and the glans. The shaft is cylindrical and composed largely of specialized erectile tissue. When relaxed, the entire organ measures approximately 50 centimeters (20 inches) in length, with a diameter between 2.5 and 6 centimeters (1 to 2.4 inches).
The glans is the free, distal end, which is highly sensitive and expands significantly upon sexual arousal. Covering and protecting the flaccid organ is the prepuce, often referred to as the sheath. The prepuce is a double fold of skin that retracts to expose the penis when it is fully extended.
The prepuce contains numerous sebaceous glands that produce a waxy, lubricating substance called smegma. Smegma acts to maintain skin health and facilitate smooth movement inside the prepuce. The penis usually hangs loosely within this sheath, secured by the retractor penis muscles which keep it mostly internal when not in use.
How the Equine Penis Differs
The horse possesses a musculocavernous type of penis, distinguishing it from other livestock like cattle. Erection is achieved primarily through vascular engorgement, meaning it swells dramatically with blood. This inflow causes a large increase in both the length and the diameter of the organ, which can double or triple in size during an erection.
In contrast, the fibroelastic penis of a bull contains a large amount of connective tissue and only small blood spaces. This causes it to lengthen without significant increase in diameter by straightening a bend known as the sigmoid flexure. The stallion’s glans has a distinctive mushroom shape with a prominent rim called the corona. The tip features a small dorsal depression known as the fossa glandis, unique to the horse.
The terminal part of the urethra extends slightly beyond the glans, forming the urethral process. This extension, along with the surrounding fossa glandis, is a common site for the accumulation of smegma and debris. The unique shape of the glans is thought to aid in the delivery of semen directly into the mare’s uterus during copulation.
Function and Associated Terms
The organ serves the dual purposes of eliminating urine and depositing semen during reproduction. When urinating, male horses will typically adopt a specific posture, often referred to as “dropping” the penis, where the organ is partially or fully extruded from the sheath. This dropping behavior can also be a sign of deep relaxation or discomfort.
A male horse that has been castrated is called a gelding. Castration significantly reduces testosterone, leading to a generally calmer temperament. Because geldings rarely fully extend the organ, they accumulate more smegma inside the sheath compared to stallions.
This accumulation of waxy secretion, dead skin, and dirt can form a hard lump, known as a “bean,” most often found within the fossa glandis. If this bean grows too large, it can cause discomfort or interfere with the flow of urine, necessitating occasional cleaning of the sheath.