What Is the Structure and Function of the Human Penis
The penis is the copulatory organ in male mammals and is also the organ responsible for urine discharge from their body. While in higher vertebrates this organ is called the penis, in lower invertebrates the corresponding structure is often referred to as cirrus.
Penis Structure
A part of the penis is outside the body and the other part is inside. The internal part of the penis is attached to the bony edges of the pubic arch which is the front part of the pelvis, at the base of the trunk. This internal part is called the root of the penis. The external part of the penis, called the body of the penis, is pendulous and is covered by skin.
Penis Anatomy
The penis anatomy is segregated into two parts: the external portion or the body and the root. The root of the penis has two projections (crura) and the bulb of the penis. The crura are joined to the edges of the pubic arch and the bulb is attached to the perineal membrane that makes the base of the trunk. The location of the penis root is right under the bulbourethral glands with the corpus spongiosum (or corpus cavernosum urethrae). It is a long cylindrical body of tissue that runs through the body of the penis right to its tip. At this point, it forms a mushroom-shaped structure that is termed a glans penis. The base of the glans penis has the corona (projecting margin).
The urethra is a tube that passes through the center of the corpus spongiosum. It provides the common route for the passage of both urine and semen. At the tip of the glans penis, the urethra provides a slit-like opening. At the sides of the bulbourethral glands, there is a pair of long cylindrical parts called the corpora cavernosa. They course through the body of the penis and located at the sides and in the area directly above the corpus spongiosum. The corpora cavernosa ends right before the glans penis. The groove where the corona is overhanging the corpora cavernosa is called the neck of the penis.
The penis anatomy has been illustrated in the penis diagram below.
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The corpora cavernosa has empty spaces that are divided by tissue partitions. These are made of collagen (fibrous protein), muscle, and elastic fiber. The corpora cavernosa are called erectile tissue since, at the time of sexual excitation, blood flows and fills their empty spaces, expanding their fibrous tissue. This blood is normally allowed to flow out by the blood vessels but their constriction holds the bloods in the penis for some time. This process enlarges and hardens the penis, making it erect due to the increased blood pressure.
The corpora cavernosa and corpus spongiosum are both covered by a circular layer of elastic tissue that is covered by a thin layer of skin. This skin is slightly darker than the rest of the body, is loose, and gets folded when the penis is in a flaccid state. The glans penis has a circular fold of skin where it begins. This skin is commonly known as the foreskin (prepuce) and it extends further to cover the glans.
Blood Supply to the Penis
The penis gets its blood supply from the internal pudendal artery which is a branch of the internal iliac artery. This artery supplies blood to the pelvic structures and organs and the inside of the thighs. The penis also has sensory and autonomic (involuntary) nerves. In the autonomic nerve fibers, the parasympathetic fibers cause the dilation of the blood vessels while the sympathetic fibers cause their constriction. The sympathetic system causes ejaculation which inhibits the desire to urinate at the time of erection and prevents the semen from entering the bladder at the same time.
Types of Penis
Some penises are straight at the time of erection while others have s slight curvature. Both types of penis are perfectly normal. There are three categories of a curved penis:
Curved downward from the base of penis.
Curved upwards from the base.
Curved to the left or right.
FAQs on Penis Anatomy Structure and Reproductive Functions
1. What is the penis in human biology?
The penis is the external male reproductive organ that functions in reproduction and urination. It is part of the male reproductive system and has two main roles:
- Delivers semen containing sperm into the female reproductive tract during sexual intercourse.
- Allows the passage of urine from the bladder through the urethra.
2. What are the main parts of the penis?
The penis is composed of three main anatomical parts: the root, shaft, and glans.
- Root: The internal portion attached to the pelvic bones.
- Shaft (body): The elongated external portion containing erectile tissues.
- Glans penis: The rounded tip, which is highly sensitive and contains the urethral opening.
3. What is the function of the penis?
The primary function of the penis is to enable reproduction and excretion. It performs two key biological roles:
- Reproductive function: Transfers semen during ejaculation for fertilization.
- Urinary function: Expels urine from the body via the urethra.
4. How does an erection occur?
An erection occurs when blood fills the erectile tissues of the penis, making it firm and enlarged. The process involves:
- Sexual stimulation triggering nerve signals.
- Release of chemicals that relax smooth muscles in blood vessels.
- Increased blood flow into the corpora cavernosa and corpus spongiosum.
- Reduced blood outflow, maintaining rigidity.
5. What tissues make up the erectile tissue of the penis?
The erectile tissue of the penis consists mainly of the corpora cavernosa and the corpus spongiosum.
- Corpora cavernosa: Two cylindrical columns responsible for most of the erection.
- Corpus spongiosum: Surrounds the urethra and forms the glans, preventing urethral compression during erection.
6. What is the difference between the penis and the scrotum?
The penis is the organ used for reproduction and urination, while the scrotum is a sac that holds and regulates the temperature of the testes. Key differences include:
- Penis: Contains erectile tissue and the urethra.
- Scrotum: Contains the testes, where sperm and testosterone are produced.
7. What is the role of the urethra in the penis?
The urethra is the tube that carries urine and semen through the penis to the outside of the body. It runs through the corpus spongiosum and serves two functions:
- Transports urine from the bladder.
- Transports semen during ejaculation.
8. What is the glans penis and why is it sensitive?
The glans penis is the rounded, distal tip of the penis that contains a high concentration of sensory nerve endings. Its sensitivity is due to:
- Dense networks of sensory receptors.
- Thin epithelial covering compared to the shaft.
9. How does ejaculation occur?
Ejaculation is the forceful release of semen from the penis through coordinated muscular contractions. The process occurs in two main phases:
- Emission: Semen moves into the urethra from the reproductive glands.
- Expulsion: Rhythmic contractions of pelvic muscles propel semen out through the urethral opening.
10. Is the penis part of both the reproductive and urinary systems?
Yes, the penis is part of both the male reproductive system and the urinary system because it serves dual functions.
- In reproduction, it delivers sperm-containing semen into the female reproductive tract.
- In urination, it expels urine from the bladder.
