Penis: Structure, Functions, Practice Problems and FAQs

Every unisexual organisms have only one type of reproductive system. It can be either male or female reproductive systems. The male and female reproductive systems of various species show some differences in the structure. What is the main function of reproductive systems? Yes, the major function of male reproductive system is to produce sperm and that of the female reproductive system is to produce eggs. So that during sexual intercourse the male and female gametes fuse together and their fertilisation leads to the formation of zygote.

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GIF: Sperms approaching egg or ova for fertilisation

If you observe the reproductive system of humans, the sperms are produced in the seminiferous tubules of testis. Then these sperms are matured and stored in the epididymis, a structure above each testis. We know that the sperms should fuse with the eggs that are produced inside the ovary, right? How does this happen then? The external genitalia in males helps in the transfer of sperms to the vagina. That external genitalia is called penis in human beings. What should be the structure of a penis? It should be capable of entering the female genitalia and ejecting sperm inside it. What all can be the functions of a penis other than this? Let’s discuss the structure and functions of a penis in this article.

Table of contents

Male reproductive system
Penis
Structure of penis
Functions of penis
Practice Problems
FAQs

Male reproductive system

The human male reproductive system is located in the pelvic region. It is composed of the following structures:

Primary reproductive organs
Accessory ducts
Accessory glands
External genitalia

Primary reproductive organs

It is composed of one pair of testes. They helps in the production of sperms and sex hormones.

Fig: Testes

Accessory ducts

It is composed of seminiferous tubules, rete testis, vasa efferentia, epididymis and vasa deferentia. These ducts help in the storage and transfer of sperms during ejacutaion.

Fig: Accessory ducts

Accessory glands

It is composed of a pair of seminal vesicles, a pair of Cowper’s glands or bulbourethral glands, and a prostate gland.

Fig: Accessory glands

External genitalia

Penis is the external genitalia in human beings and it acts as the copulatory organ.

Fig: External genitalia

Penis

The male external genitalia is penis. Penis is the copulatory organ that lies just in front of the scrotum. It helps in the insemination or the transfer of sperms into the female reproductive tract.

Fig: Penis

Structure of penis

Penis consists of a long shaft having an expanded tip called glans penis. A loose fold of skin covers the glans penis and it is called prepuce or foreskin. There is a slit-like opening at the tip of glans penis which is known as the external urethral orifice or urinogenital aperture.

Fig: Structure of penis

Erectile tissues of penis

Penis contains three columns of erectile tissues under the skin and they are as follows:

Two corpora cavernosa (dorsal)
One corpus spongiosum (ventral)

Corpora cavernosa

The two corpora cavernosa lie next to each other on the dorsal side. It forms the major portion of the penis. It contains blood vessels that help in the erection of penis when blood gets filled in the vessels. The proximal parts of the corpora cavernosa is the crus of penis.

Corpus spongiosum

Corpus spongiosum lies between the two corpora cavernosa on the ventral side. It is an erectile tissue that surrounds the urethra. It contains penile urethra and forms the bulb of penis. The distal ends of the corpus spongiosum forms the glans penis.

Fig: Erectile tissues of penis

Functions of penis

The major function of penis is to transfer the sperm into the reproductive tract of the female. Both urine and semen are conducted through the penis, but both can not pass through it at the same time. When the sinuses inside the penis fill with blood, it gets rigid and erected. It acts as a copulatory organ too.

Ejaculation

The discharge of semen from the penis during a sexual arouse is called ejaculation. This is followed by the erection of penis. There are two phases for ejaculation and are as follows:

Emission
Expulsion

Fig: Penis

Emission

It is the first phase of ejaculation. During this phase, the spinal cord sends nerve impulses to the epididymis and vasa deferentia. Their motility causes sperm to enter the ejaculatory duct whereupon the seminal vesicles, prostate gland and the bulbourethral glands release their secretions.

Expulsion

It is the second phase of ejaculation. Rhythmic contractions of muscles at the base of the penis occur in this phase. The sperm is expelled within the urethral wall and it releases through the urethra.

Practice Problems

1. Which of the following is correct about the penis?

i) Penis is the copulatory organ that lies just in front of the scrotum.
ii) Penis helps in the insemination of sperms into the female reproductive tract.
iii) The expanded tip of the penis is called glans penis.
iv) The slit-like opening at the tip of glans penis is known as the rete testis.

i, ii, iii and iv
i, ii and iii
i, iii and iv
I and ii

Solution: The male external genitalia is penis. It is the copulatory organ that lies just in front of the scrotum. It helps in the insemination or the transfer of sperms into the female reproductive tract. Penis consists of a long shaft having an expanded tip called glans penis. A loose fold of skin covers the glans penis and it is called prepuce or foreskin. There is a slit-like opening at the tip of glans penis which is known as the external urethral orifice or meatus or urinogenital aperture. Hence the correct option is b.

Fig: Structure of penis

2. Which of the following structures of the penis contains blood vessels that help in the erection of penis when blood gets filled in the vessels?

Corpora cavernosa
Corpus spongiosum
Scrotum
Glans penis

Solution: The two corpora cavernosa lie next to each other on the dorsal side. It forms the major portion of the penis. It contains blood vessels that help in the erection of penis when blood gets filled in the vessels. The proximal parts of the corpora cavernosa is the crus of penis. Hence the correct option is a.

Fig: Erectile tissues of penis

3. Assertion: Both urine and semen are conducted through the penis.
Reason: Both urine and semen can not pass through the penis at the same time.
Which of the following statements are correct about the assertion and reason given above?

Both the assertion and the reason are true, and the reason is the correct explanation of the assertion
Both the assertion and the reason are true, but the reason is not the correct explanation of the assertion
Assertion is true, but the reason is false
Both the assertion and the reason are false

Solution: The major function of penis is to transfer the sperm into the reproductive tract of the female. Both urine and semen are conducted through the penis, but both can not pass through it at the same time. When the sinuses inside the penis fill with blood, it gets rigid and erected. Semen can come out of the penis only when the penis is hard. Urine can not pass through the penis, when it is hard. Hence the correct option is b.

Fig: Penis

4. Which of the following is the first phase of ejaculation?

Emission
Expulsion
Expansion
Execution

Solution: The discharge of semen from the penis during a sexual arouse is called ejaculation. This is followed by the erection of penis. There are two phases for ejaculation and are emission and expulsion. It is the first phase of ejaculation. During this phase, the spinal cord sends nerve impulses to the epididymis and vasa deferentia. Their motility causes sperm to enter the ejaculatory duct whereupon the seminal vesicles, prostate gland and the bulbourethral glands release their secretions. Hence the correct option is a.

FAQs

1. What is circumcision?
Answer: A surgical procedure by which a part or the entire prepuce is removed is called circumcision. It is usually performed after a few days of birth. This lowers the risk of urinary tract infections, gives protection against penile cancer, and possibly lower risk of sexually transmitted diseases.

2. What is erectile dysfunction?
Answer: The inability to develop and maintain an erection for the sexual performance is called erectile dysfunction. Many physical issues like high cholesterol, high blood pressure, heart disease and smoking can cause erectile dysfunction. Anxiety, depression and stress can also cause this.

Fig: Erectile dysfunction

3. What is an ejaculatory duct?
Answer: The thin walled tube inside the male reproductive system is called an ejaculatory duct. It is a paired structure formed by the union of vas deferens and the ducts from the seminal vesicle. The ejaculatory duct passes through the prostate and opens into the urethra.

Fig: Ejaculatory duct

4. What are the functions of seminal plasma?
Answer: Seminal plasma is a collection of secretions from seminal vesicles, prostate gland, and Cowper’s glands. The functions of seminal plasma are as follows:

Provides fluid medium for the transfer of sperms into the vagina of females.
It is alkaline and neutralises acidity of urethra of male and female, thereby protecting the sperm.
The lubrication of the female reproductive tract is done by the seminal plasma and it facilitates the movement of sperms.

Fig: Semen (Seminal plasma and sperms)