Human Reproduction Class 12 Notes
System of Male Reproduction
The male reproductive system is divided into four major components:
- Testes
- Auxiliary Ducts
- Glands
- External Genital Organs
Testes
The testis is located in the pelvic area outside the abdominal cavity in a pouch called the scrotum. The scrotum is a tiny muscular sac that holds and protects the testes. The scrotum is a component of the external male genitalia that is placed behind the penis. The testes are located outside the abdominal cavity to keep their temperature roughly 2-2.5 degrees Celsius cooler than the usual human body temperature. This condition is required for sperm synthesis.
The lower temperature in the testes is necessary for spermatogenesis since normal human body temperature might cause sperm mutation. The testis is oval, about 4-5cm long and 2-3cm broad. The testis includes around 250 compartments known as Testicular lobules. Each lobule typically contains 1-3 strongly coiled seminiferous tubules that are important in sperm production. Seminiferous tubules are the sites where spermatozoa are formed during the meiotic process.
In the inner lining of each seminiferous tubule, there are two types of cells: spermatogonia and Sertoli cells. These spermatogonia are diploid in nature and are known as immature germ cells. They create sperm through the process of meiosis. Their cells have 46 chromosomes. Sertoli cells in the seminiferous tubules feed the spermatogonia.
The interstitial spaces are the areas that exist outside of the seminiferous tubule and include tiny blood arteries, Leydig cells, and certain immunocompetent cells. Leydig cells produce and release the interstitial spaces are the areas that exist outside of the seminiferous tubule and include tiny blood arteries, Leydig cells, and certain immunocompetent cells. The testicular hormones known as androgens are synthesized and secreted by Leydig cells.
Accessory Ducts
The accessory ducts help to transfer sperm from the testes to the urethra for discharge outside the body. There are four auxiliary ducts in the male reproductive system: Testis Rete, efferentia vasa, Epididymis, and Vas difference.
The ducts where the seminiferous tubules open into a series of channels are known as the rete testis.
Vasa Efferentia: These ducts form a conduit from the rete testis to the epididymis, which is located on the posterior surface of each testis. The epididymis is a long, coiled tube that joins the Epididymis.
Vas deferens The ducts where the seminiferous tubules open into a series of channels are known as the rete testis. Each testicle has an Epididymis on the backside. Vas deferens is a muscle channel that ascends into the abdominal cavity and loops around the urine bladder. It is responsible for transporting sperm from the epididymis to the ejaculatory duct.
The Ejaculatory Duct is located on each side of the prostate gland. The sperms are stored and transported in the ejaculatory ducts. and forms a loop around the urine bladder It is responsible for transporting sperm from the epididymis to the ejaculatory duct.
Urethra: The urethra is a narrow muscular tube that extends from the urine bladder via the penis to its external opening, known as the urethral meatus.
Glands
Seminal Vesicles: Seminal vesicles provide a considerable part of the fluid in sperm, accounting for roughly 60-75 percent of the fluid in sperm. Enzymes, proteins, vitamin C, fructose, prostaglandins, and phosphorylcholine are abundant in this fluid. The spermatozoa receive nutritional energy from the high fructose content.
The prostate gland is a thick organ that is located right below the urinary bladder. The prostate gland discharge is somewhat alkaline, thin, and milky in appearance. It aids sperm survivability in the acidic vaginal environment while also improving sperm motility. The production of these glands aids in the lubrication of the penis and also neutralises any leftover acidity in the urethra.
Female Reproductive System
The female reproductive system is specialized to perform a variety of duties such as gametogenesis, ovulation, fertilization, pregnancy, birth, and child care. The female reproductive system is composed of various components:
The ovaries are the major female sex organs and are tiny and oval in appearance. They generate the female gamete known as the ovum as well as ovarian hormones.
The ovaries are around 2-4cm in length. They are joined to the pelvic wall and the uterus via ligaments. A thin epithelium that surrounds the ovarian stroma protects the ovaries. Ovarian stroma- This is the ovary’s matrix, which is separated into two sections:
- Cortex of the periphery
- Internal medulla
- Additional Ducts:
The accessory ducts of the female reproductive system accessory ducts include the oviducts, uterus, and vagina.
Oviduct (Fallopian Tube)
The fallopian tube is usually 10-12 cm long. It extends from the ovarian periphery to the uterus.
Infundibulum: A proximal section of the oviduct located closer to the ovary. It has fimbriae and is funnel-shaped.
Fimbriae: These are the finger-like projections on the infundibulum’s margins. They aid in the collecting of the ovum following ovulation. The ampulla is the larger section of the oviduct that links to the infundibulum.
Isthmus: The oviduct’s last segment, which penetrates through the uterine walls and opens into a tiny lumen.
Uterus: The uterus is also known as the womb. It is shaped like an inverted pear and is held in place by ligaments linked to the pelvic wall. The embryo grows into the fetus in the uterus. It enters the vagina through a narrow cervix. The uterine wall is made up of three layers of tissue: perimetrium, myometrium, and endometrium.
The thin exterior membranous membrane that shields the uterus from friction is known as the perimetrium. Myometrium: This is the thick middle layer of smooth muscle. It depicts heavy contractions during the baby’s birth. Endometrium: The inner glandular layer lining the uterine cavity. It goes through a process.
Cervical Canal: The cervical canal links the cavity of the uterine body to the vaginal lumen.
Birth Canal: The birth canal is formed by the cervical canal and the vagina, and it aids in the birth of the infant.
External Female Genitalia: The mons pubis, labia majora, labia minora, hymen, and clitoris are the main external female genitalia of the female reproductive system.
Mons Pubis is a fatty tissue cushion that is covered by hair and skin.
Labia Majora are tissue folds that surround and protect the external reproductive organs. It covers the vaginal entrance and extends from the mons pubis.
Labia Minora: These are the paired tissue folds that reside just inside the labia major.
Gametogenesis
Following are the important terms for human reproduction class 12 notes. Spermatogonia are immature male germ cells that divide meiotically to generate sperms. Spermatogonium (plural) is a diploid organism with 46 chromosomes.
Primary Spermatocytes: Spermatogonia that go through meiosis to generate two equal haploid cells termed secondary spermatocytes. Each cell has 46 chromosomes.
Secondary Spermatocytes: These haploid cells develop from primary spermatocytes as a result of meiosis I. They have 23 chromosomes.
Spermatids are cells that develop from secondary spermatocytes as a result of meiosis II. Spermatogonia are haploid cells with 23 chromosomes.
Spermiogenesis is the process through which spermatozoa or sperms develop from spermatids.
Spermiation: The process by which sperms are liberated from the seminiferous tubules.
Gonadotropin-releasing hormone (GnRH) is a hypothalamic factor. This hormone’s levels mostly rise throughout puberty. GnRH production increases the anterior pituitary gland’s release of two gonadotropins, Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH). human reproduction class 12 notes.
Follicle Stimulating Hormone (FSH): This hormone induces the release of several components that are vital in the process of spermatogenesis.
Luteinizing Hormone (LH): LH regulates the function of the testicles and ovaries. It operates on Leydig cells, stimulating androgen production and secretion.
Oogenesis
Oogenesis is the process through which a mature female gamete is formed. It is first introduced during the embryonic period. A few million gamete mother cells, or oogonia, are generated in the foetal ovary at this time. No additional oogonia are made or added after delivery.
The oogonia create primary oocytes during the process of meiosis and are halted at the Prophase stage. Each primary follicle is made up of primary oocytes surrounded by granulosa cells. A high percentage of primary follicles deteriorate between birth and adolescence. As a result, around the time of puberty, the ovary has only about 60,000-80,000 primary follicles. A few additional layers of skin surround the remaining basic follicles.
Menstrual Cycle
- Menstruation: In this process, the blood and mucosal tissue are regularly discharged in a periodic manner. It occurs due to the breakage of the inner lining of the uterus. This process takes place once a month and is called a period.
- Menarche: Menarche is the first menstruation for a human female that begins at puberty. The actual age for menarche generally differs from person to person. The first menstruation is the signal of the beginning of reproductive age in females.
- Menopause: Menopause is defined as the permanent ceasing of the menstrual cycle in females. It occurs due to the depletion of oocytes and the loss of the ability of the ovary to produce estrogen as a result of aging. menopause. The average age of menopause is between 45-50 years and it varies from person to person.
An important topic in the female reproductive system is the Menstrual Phase: The menstrual flow occurs during this phase. The flow usually lasts 3-5 days.
During this stage, the breakdown of the uterine endometrium and blood vessels produces a crimson liquid fluid that emerges from the vagina. This procedure takes happens only when the ovum discharged by the ovary is not fertilised. The menstrual flow does not occur during pregnancy. Menstruation is affected by variables such as stress, bad food, poor health, and so forth.
The Graafian follicle matures during the Follicular Phase. Primary follicles develop in the ovary to become fully mature Graafian follicles. The uterine endometrium regenerates via proliferation. These endometrial and follicular regeneration alterations are caused by ovarian hormones such as Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH). In this phase, the release of LH and FSH gonadotropins steadily rises to encourage follicular growth. This increasing amount of LH and FSH also stimulates the release of estrogens by developing follicles.
Ovulation/Ovulatory Phase: This is the stage at which the ovum is released from the ovary. LH and FSH levels peak mid-cycle, around the 14th day, during this period.
Luteal Period: This is the phase of corpus luteum production, also known as the secretary phase.
After ovulation, the burst portions of the Graafian follicle produce the yellow corpus luteum. It secretes a considerable amount of progesterone hormone, which keeps the endometrium healthy. The endometrium is essential for the implantation of the fertilized ovum as well as subsequent pregnancy processes.
There is no menstruation during pregnancy because all menstrual cycle events cease. In case of fertilization doesn’t occur, The corpus luteum degenerates. This causes the endometrium to disintegrate, resulting in menstruation and the start of a new cycle.
Insemination is the process by which the penis releases sperm into the vagina during coitus or copulation. The motile male gamete or sperm travels quickly past the cervix, through the uterus, and eventually to the site of fertilisation in the ampullary area of the fallopian tube.
Fertilization is the joining of a haploid male gamete or sperm and a haploid female gamete or egg. During fertilisation, the sperm produces modifications in the ovum’s zona pellucida layer to prevent additional sperms from entering. This ensures that a single sperm can fertilze just one ovum.
The acrosome’s secretions facilitate sperm entrance into the ovum via the zona pellucida as well as the plasma membrane. This event causes the secondary oocyte to go through meiosis completely. This is another uneven division that results in the formation of a second polar body and a haploid ovum.
Conclusion
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