Human Reproduction, Male & Female Reproductive Parts

Human Reproduction: Understanding the process of human reproduction is very important for the students of Class 12 Biology. It explains how new life starts and the coordination of the male and female reproductive systems. 

Human reproduction includes the interaction between the male sperm and the female egg, known as fertilization, which leads to the formation of the zygote. The chapter simplifies all major concepts like male and female systems, formation of gametes, fertilization, pregnancy, and childbirth in an easy, exam-ready format.

NEET Online Crash Courses

What is Human Reproduction?

Human Reproduction is the process by which humans produce offspring. It involves two types of gametes: the sperm from males and the ovum from females. It includes the formation of gametes, their fusion, implantation of the embryo, growth of the baby, and childbirth.

Male Reproductive System

In males, the system lies in the pelvic region and includes organs for the formation, maturation, and transportation of sperm.

Testes

The testes lie in the scrotum, which keeps them 2.5°C below the body temperature for sperm formation. Each testis is divided into 250 lobules, in each of which seminiferous tubules are present, the sites for spermatogenesis.

Cells in Seminiferous Tubules

• Spermatogonia: Diploid cells that produce sperm.
• Sertoli cells: Support and nourish the developing sperm.

Outside of the tubules, Leydig cells produce testosterone.

Sperm Transport Pathway

• Seminiferous tubules
• Rete testis
• Vas efferens
• Epididymis - stores and matures sperm
• Vas deferens
• Ejaculatory duct
• Urethra

Accessory Glands

• Seminal vesicles: Produce sperm nutrients
• Prostate gland: adds milky fluid
• Bulbourethral glands: add mucus for lubrication
• These secretions are called seminal plasma, in which sperm can swim.

Structure of Sperm

A sperm has:

• Head with nucleus and acrosome
• Middle piece with mitochondria
• Tail for movement

Female Reproductive System

The female system includes organs responsible for ova production, supporting fertilization, and nourishment of the baby during development.

Ovaries

Ovaries produce ova and female hormones. Each ovary has:

• Cortex: Contains follicles
• Medulla: Has blood vessels

Follicles grow from primary to secondary to tertiary stages and finally form the Graafian follicle.

Oviducts (Fallopian Tubes)

• Each tube is 10–12 cm in length and contains:
• Infundibulum with fimbriae
• The ampulla, where fertilization takes place
• Isthmus leading to the uterus

Uterus

A pear-shaped organ with:

• Perimetrium is the outer layer.
• Myometrium is the muscular layer for contractions.
• The endometrium is the inner layer where the embryo implants.

Vagina

The vagina is a muscular, hollow tube that connects the uterus to the outside of the body in females. It serves as the passage for menstrual flow, sexual intercourse, and childbirth. Its flexible walls can stretch to accommodate different functions that play a major role in the female reproductive system.

Oogenesis

Oogenesis starts before birth. Females are born with approximately 2 million primary oocytes arrested in prophase I. At puberty:

• Only a few follicles will mature each cycle.
• One secondary oocyte is usually released during ovulation.
• Meiosis is completed only upon fertilization.

Menstrual Cycle

The menstrual cycle is a natural, monthly process where the body prepares itself in case of a possible pregnancy in females. It is mainly an ongoing process from puberty through menopause. The entire cycle usually lasts approximately 28 days and has three phases:

1. Menstrual Phase: The endometrium is shed for 3–5 days because of low levels of estrogen and progesterone.

2. Proliferative Phase: Under estrogen influence, the endometrium rebuilds.

3. Secretory Phase: Endometrium thickens under progesterone and gets prepared for implantation.

Fertilization: Where New Life Begins

Fertilization is the process by which the sperm cell from the male unites with an egg cell from the female, marking the beginning of new life. It occurs in the ampulla of the fallopian tube.

Steps in Fertilization

• Sperms become capable of fertilizing by undergoing capacitation.
• Sperm bind to ZP3 receptors on the ovum.
• Acrosomal enzymes help sperm enter the ovum.
• Blocks ensure only one sperm enters, preventing polyspermy.
• A zygote forms a diploid cell.

Early Development

The zygote divides to form:

• 2-cell
• 4-cell
• 8-cell
• Morula
• Blastocyst

The blastocyst then implants in the uterus at about day 7.

Implantation and Pregnancy

The blastocyst then attaches to the endometrium of the uterus in a region called the fundus.

Placenta: The placenta is formed from maternal and fetal tissues. It:

• Exchanges nutrients and gases
• Removes wastes
• Produces hormones such as:

1. hCG

2. Progesterone

3. Estrogen

4. hPL

5. Relaxin

It serves as a connection between the fetus and the placenta.

Formation of Twins

Twins come about when either a single fertilized egg splits into two embryos, making identical twins with the same genetic makeup, or when two different eggs are fertilized by two different sperm cells, creating fraternal twins who share genetic similarities like regular siblings. This natural process results in a pregnancy that develops two babies.

Types of Twins are as follows:

• Monozygotic Twins: These develop from a single zygote that splits. They are genetically identical.
• Dizygotic twins: They form when the two ova are fertilized by two different sperms; they may or may not be alike.

Also Check: Most Repeated Questions in NEET Exam

Parturition (Childbirth)

Parturition, otherwise referred to as childbirth or labor, is the process by which the baby is delivered from the uterus through the vagina to the outside world. It generally happens approximately nine months after fertilization and consists of three stages:

• Dilation of the cervix
• Expulsion of the baby, and
• Delivery of the placenta.
• This life-giving process denotes the end of pregnancy and the start of a new life.

Also Check: How Many Days Left for NEET 2026

Lactation

Lactation is the normal course of production and release of milk from the mammary glands after giving birth. It helps in fulfilling vital nutrition and immunity needs for a newborn baby.  

Milk production involves hormones such as prolactin, responsible for milk production, and oxytocin, responsible for milk ejection during breastfeeding. The first milk is colostrum, rich in antibodies, boosting the immune system.

Prepare for NEET with PW Online NEET Coaching ! Our courses offer structured lessons, clear explanations of concepts, and interactive classes to support your NEET preparation effectively.

Also Check:

• NEET Exam Pattern 2026
• NEET 2026 Admit Card
• NEET Eligibility Criteria 2026
• NEET 2026 Exam Centres
• NEET Candidate Login 2026