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Human Reproductive System


Are you a student that has seen the awkward silence in the class when the teacher talks about human reproduction? Have you seen your classmates giggling away, as the teacher never really taught the topic? Worry not! You’re not the only one. We bring to you a comprehensive understanding of the human reproductive system.


  • Human reproduction is a form of sexual reproduction which takes place after unprotected sex between a male and a female

  • The male deposits the semen in the vagina, which then leads to the fusion of the sperm with the ovum (fertilization), creating the zygote which becomes the human baby


  • The coming together of the sperm (male) and the ovum (female) to create the zygote is called fertilization

  • The zygote is the first single cell of the newly born baby




The process of human reproduction involves well-function male and female reproductive systems

The Male Reproductive System

The male reproductive system consists of a group of organs that work together to produce and transport sperm, deliver the sperm to the female reproductive tract and produce the sex hormones required to maintain the male reproductive system.


Let’s take a look at the division and the functionality of the different organs in the male reproductive system:

Classification of the Male Reproductive Genitalia

  • External Male genitalia

  • Internal Male genitalia

  • Secretary parts


The External Male genitalia

External male genitalia are visible from the outside, and consist of the following organs:


  • Commonly known as the ball sack, the scrotum is a sack made of cutaneous tissue which contains the testes, epididymis and the vas deferens

  • The scrotum is divided into the right and the left scrotum through a ridge

  • This ridge is located below the penis

  • It has been commonly observed that the left scrotum hangs a little lower than the right scrotum, and this is not cause for concern

  • The size of the scrotum varies based on the external temperature

    • The scrotum shrinks and becomes smaller in cold temperatures, moving the sperm closer to the body

    • This action is to ensure that the sperm is maintained at the correct temperature and is performed by the dartos muscle



  • The penis is the male organ for sexual intercourse and is made up of three parts:

    • Root, which attaches to the abdomen wall

    • Shaft, which is the elongated muscle

    • Glans, which is the mushroom shaped tip of the penis

  • The shaft of the penis is the externally visible part which is completely enveloped in skin

  • The glans is covered with a loose layer of skin called foreskin. This skin is sometimes removed in a procedure called circumcision

  • The end of the penis consists of an opening known as the urethra, which aids in urination and also in expelling semen, which is called the process of ejaculation



Image source: :


Erection of the Penis 

  • The shaft of the penis contains many large empty spaces

  • Something you saw, felt, smelled, heard, or thought makes your nerves send chemical messages to the blood vessels in your penis

  • The arteries relax and these spaces fill with blood when a man is aroused, making the penis rigid, erect and ready for sex

  • When the penis is erect, the flow of urine from the urethra is blocked, ensuring that only semen is expelled



  • When a man is aroused and his erect penis is being stimulated, the tubes called vas deferens pushes sperm from the testes to the urethra

  • When sexual excitement reaches a peak, the urethra senses the sperm and sends a signal to the spinal cord

  • The spinal cord sends signal to the muscle at the root of the penis

  • These muscles expand and contract every 0.8 seconds, pushing the sperm out as a thick white fluid called semen

  • Ejaculation marks the end of the male orgasm


Internal Male Genitalia

Internal male genitalia are located inside the body and consist of the following organs:


Testes (singular: testis)


  • Most men have two testes, the right and the left testis, located in the right and the left scrotum respectively

  • The testes are responsible for production of testosterone, the male sex hormone, and for the creation of sperm cells (male gametes)

  • The process of formation of sperm is known as spermatogenesis


  • The epididymis is a coiled structure attached to the back of the testes 

  • It is responsible for carrying and storing the sperm cells produced in the testes

  • The epididymis is also responsible to bring the sperm to maturity, since the sperm that emerge from the testes are immature and incapable of fertilization

  • The epididymis consists of three parts, the head, the body and the tail 

Vas Deferens (Ductus Deferens)

  • The vas deferens is responsible for the transfer of mature sperm cells from the epididymis to the urethra

    • Mature sperm cells are contained in the seminal fluid (semen), which is thick and white

  • It is an elongated coil, with a lumen responsible for the movement of the seminal fluid

  • The process of vasectomy is performed on the vas deferens, resulting in male infertility




Secretory parts

The secretory parts of the male reproductive system are responsible for the secretion of the constituents of the seminal fluid, which contains sperm cells


The secretory parts of the male reproductive system include:


Seminal Vesicles

  • The seminal vesicles are sac-like pouches that attach to the vas deferens

  • It consists of the right and the left seminal vesicle and is in charge of secreting a large amount of fluid into the urethra

  • The fluid secreted by the seminal vesicles contains:

    • Fructose, which provides the sperm with a source of energy to help them move

    • Enzyme, which causes the coagulation of the seminal fluid, making it a thick whitish fluid

  • The secretions of the seminal vesicles make up most of the volume of a man’s semen



Image source: BD Chaurasia textbook of anatomy, volume 2


  • The prostate is a walnut-sized gland located below the urinary bladder

  • The secretion of the prostate adds to bulk of the seminal fluid and helps to nourish the sperm cells

  • The urethra, which carries the seminal fluid during ejaculation, passes through the centre of the prostate gland

  • Changes occur in the growth of the prostate according to the age of the man 

    • This process of growth starts around the age of puberty

    • The prostate enlarges up to the age of 30 and beyond the age of 45, there is increased chances of the prostate enlarging further and causing medical issues


Bulbourethral Glands (Cowper’s Glands)

  • Cowper’s glands are pea-sized glands located below the prostate, on either side of the urethra

  • It’s contribution to the seminal fluid is lesser in volume, as compared to that of the prostate and the seminal vesicles

  • These glands produce a clear, slippery fluid that empties directly into the urethra.

  • This fluid lubricates the urethra and neutralizes any acidity that may be present due to residual drops of urine in the urethra

Major Components of Seminal Fluid (Semen)

  • Sperm

  • Fructose

  • Coagulation enzyme

  • Antioxidant enzymes

  • Mineral elements

  • Fluid from all the secretory glands

When is the Sperm Viable?

  • Viability, in its most basic sense means “alive”, and refers to the live sperm present in the seminal fluid sample

  • The seminal fluid contains a large number of sperm cells, many of which will perish in the acidic environment of the vagina

  • Viability testing in done using dyes, where the non-viable sperm cells will absorb the dye due to damaged cell membranes

  • Viability tests are conducted if the number of motile sperm cells (moving cells) are on the lower side (Less than 40%)



  • Circumcision is the surgical removal of the foreskin covering the glans penis, which is the mushroom-shaped tip of the penis

    • The procedure is usually performed on newborn babies

  • Circumcision does not affect the fertility of a man

When is Circumcision Performed?

  • Circumcision is usually performed in some religions and cultures as a ritual

    • Jewish and Islamic religions

    • Tribal rituals in Africa and Australia

  • Circumcision may also be performed as a preventive health measure to reduce the risk of STDs, penile cancer and urinary tract infections in adult life

Benefits of Circumcision

  • The penis is easier to keep clean as there is not folded foreskin within which foreign objects or microbes may remain

  • Circumcision has been observed to lower the risk  of STIs and urinary tract infections

  • There is reduced risk of penile cancer in circumcised men


When Should Circumcision not be Performed?

● Children under intensive care for other health conditions

● Premature babies

● Children with penile abnormalities

● Men with blood clotting disorders

Procedure of Circumcision

Circumcision is a minor surgical procedure that needs to be performed by a certified surgeon.

The procedure is as follows:

    • The arms and legs of the man/baby are held back and the penis is exposed

    • The penis is cleaned with an antiseptic and a local anaesthetic is injected or applied on the tip of the penis

      • General anaesthetic may be used in adult men as the process can be more painful

    • A ring is placed to separate the glans from the shaft and the foreskin is removed by the surgeon, from the tip of the penis

    • The circumcised penis is now cleaned with an antiseptic and a gauge is applied to cover the area and it’s left to heal


  • Healing takes ~10 days and needs care to ensure that infections are avoided

  • Non-fragrant ointment or plain petroleum jelly can be applied on the region

  • The dressing has to retained until the doctor declares the wound healed

  • If there is a plastic ring around the penis, it will fall off after about 7 days


Warning Signs

Visit the nearest hospital if:

  • Fever develops

  • Normal urination does not resume within 12 hours of the surgery

  • There is persistent bleeding

  • here is any foul-smelling drainage from the urethra or around the cut

Female Reproductive System

The female reproductive system is a complex and versatile bodily system that is not only the site of fertilisation, but also nurtures the growing embryo and ensures that the female sex hormones are produced.


It consists of the following parts:

  • External Reproductive System

  • Internal Reproductive System 

  • Mammary Glands


External Reproductive System


The external reproductive system refers to the reproductive organs which are visible from the outside, and they include:

Mons Pubis 

  • The mons pubis is the inverted triangle-shaped fatty tissue on the pelvis, sitting on top of the pubic bone

  • The main purpose of it is to protect the pubic bones during sexual intercourse

  • It also has glands which secrete pheromones, which signal sexual stimulation

Labia Majora & Labia Minora 

  • Labia means lips and Majora means large, while Minora means small

  • Labia majora are the large horizontal lips that protect the external reproductive organs

  • Labia minora lie beneath the labia majora and cover the opening to the vagina and the urinary tract

  • Both labia majora and minora see hair growth during and after puberty, which further enhance their ability to keep foreign objects away


  • It is a thin transparent tissue which covers the entry to the vagina

  • It is not possible to determine the status of virginity just by looking at the hymen

    • Breakage or rupture of the hymen does not indicate loss of virginity


Clitoris (Clit)

  • The labia minora meet at the clitoris, which is a small protrusion above the urethra

  • The clitoris is very sensitive to stimulation and becomes hard/erect when aroused

  • Clitoris consists of erectile tissues and sensory nerves that help gain sexual pleasure and orgasm

    • Stimulation of the clitoris is necessary to reach orgasm

Bartholin’s Glands

  • These are two pea sized glands located on either side of the vaginal opening

  • They produce a fluid (mucus) secretion that lubricates the vagina





Internal Reproductive System

The internal reproductive system refers to the organs situated inside the female body.

The organs of the internal reproductive system are:

Vagina (Birth Canal)

  • The vagina, enclosed by labia majora and minora, is a canal joining the cervix to the outside of the body

  • The canal is approximately 10 cm long and has muscular walls, making it easy for it to expand and contract

  • Functions of the vagina include:

    • Serving as an opening for the penis to enter during sex

    • Children leave the mother’s body via the vagina in the natural birth process

    • Serving as an exit route for the blood expelled during menstruation

Uterus (Womb)

  • The uterus is a pear-shaped organ which becomes the home for the growing embryo (baby)

  • The uterus consists of two parts - the corpus (body) and the cervix (lower end)

  • The cervix is the lower part of the uterus/womb, with one end opening into the uterus and another end opening into the vagina

    • These are known as the internal orifice and the external orifice, respectively 

  • The corpus is where the growing embryo is contained and it consists of a thin lining of tissues and muscle walls, known as the endometrium lining

    • The shedding of the external layer of endometrium on a monthly basis, when not pregnant, is called menstruation

  • The corpus muscles are among the strongest muscles in the body as they expand with the size of the baby and are responsible for contracting and pushing the baby out through the vagina

Fallopian Tube

  • Fallopian tubes are tube-like structures which are attached to both the sides of the uterus

  • These tubes carry the eggs from the ovaries to the uterus and is the site of fertilisation where sperm and the ovum fuses


  • The ovaries are oval-shaped structures on either side of the uterus

  • They are responsible for producing, storing and releasing the female eggs through the fallopian tube - a process is known as ovulation

  • The ovaries also produce female sex hormones such as estrogen and progesterone


Mammary Glands (Breasts)

  • Breasts are an important part of the female reproductive system, for the following reasons:

    • Breasts are a secondary sexual trait which draws sexual attention

    • Breasts contain mammary glands, which produce milk to nourish the newborn baby after delivery


Tissues of the Breast   

  • Glandular tissue

    • Responsible for the production of milk which is secreted in milk ducts formed by the connection of multiple mammary gland nodes, called lobules

    • The milk exits the breast through 15 to 20 milk ducts that open on the surface of the nipple

  • Fibrous tissue

    • Helps in the support and suspension of the breast

  • Adipose (fatty) tissue

    • Determines the size and shape of the breast

    • The fatty covering helps to protect the breast

Structure of the Breast 

  • Nipples

    • It is a protrusion at the center of the breast surrounded by a pigmented area called the areola

    • The nipple contains lactiferous ducts that connect to the lobules producing milk in the breast

  • Areola

    • The surface of the areola contain numerous sebaceous glands which lubricate the nipple during lactation

  • Lobules

    • The lobules consist of a group or cluster of mammary sacs, capable of producing and storing milk

    • The lobules are interconnected, forming the lactiferous duct, which converges towards the nipple

  • The breast also contains arterial blood supply, venous drainage, lymph drainage and nerve supply



  • The process of milk production, storage and discharge through the nipple of the mother, after the delivery of the child, is known as lactation

  • Lactation involves release of two hormones, Prolactin and Oxytocin

    • Prolactin initiates the process of the lactation and is released from the anterior pituitary gland

    • Oxytocin releases the milk in response to the child sucking on the nipple of the mother

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