Q.What would be the number of chromosome in the spermatids?
Concept understanding — Hormonal Regulation Spermatogenesis
Let’s begin with an everyday picture. Think of a factory that produces a specific product — say, a car factory. The factory doesn’t just run on its own; it needs a central command centre that sends signals to start production, keep it steady, and stop it when enough cars are made. In the male body, the “factory” is the testes, and the “product” is sperm. The command centre is the brain — specifically two tiny glands: the hypothalamus and the pituitary gland. The signals they send are hormones (chemical messengers that travel through the blood).
Hormonal regulation of spermatogenesis means that the entire process of sperm production is controlled by a chain of hormones, each one triggering or suppressing the next. This ensures that sperm are made at the right time, in the right quantity, and that the body doesn’t overproduce them.
The Hormonal Chain (Step by Step)
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Hypothalamus releases GnRH
The hypothalamus, a region at the base of the brain, secretes Gonadotropin-Releasing Hormone (GnRH). This is the “start” signal. GnRH travels a short distance to the pituitary gland, telling it to get ready.
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Pituitary releases two key hormones
In response to GnRH, the anterior pituitary releases two hormones into the bloodstream:
- LH (Luteinizing Hormone) — targets the Leydig cells in the testes.
- FSH (Follicle-Stimulating Hormone) — targets the Sertoli cells in the seminiferous tubules (the actual “assembly line” where sperm are made).
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LH stimulates testosterone production
Leydig cells, when activated by LH, produce testosterone. Testosterone is the main male sex hormone and is absolutely essential for spermatogenesis. It acts directly on the seminiferous tubules to drive sperm production.
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FSH supports the Sertoli cells
Sertoli cells are like the “nourishers” and “quality controllers” inside the tubules. FSH makes them produce nutrients and other factors that help developing sperm cells survive and mature. Sertoli cells also convert some testosterone into a more active form.
Both LH and FSH are needed for normal sperm production. LH provides the fuel (testosterone), and FSH ensures the assembly line runs smoothly. If either is missing, spermatogenesis slows down or stops.
The Feedback Loop (Why It Doesn’t Go Wild)
The body hates waste. If too much testosterone is produced, it sends a message back to the brain to slow down. This is called negative feedback.
- High testosterone in the blood signals the hypothalamus to reduce GnRH release, and the pituitary to reduce LH and FSH release.
- Low testosterone does the opposite — the brain increases GnRH, LH, and FSH to boost production.
This keeps testosterone levels within a narrow, healthy range. Sertoli cells also produce a hormone called inhibin, which specifically suppresses FSH when sperm production is adequate.
Think of it like a thermostat: when the room gets warm enough, the heater turns off. When it cools, the heater turns back on. The hypothalamus and pituitary are the thermostat; testosterone is the heat.
Why This Matters (Even for a Commerce/Humanities Student)
- Fertility: If any link in this hormonal chain breaks — say, the pituitary fails to produce LH or FSH — a man may become infertile. This is why some fertility treatments involve giving synthetic FSH or LH.
- Medical context: Drugs that block GnRH (like those used in prostate cancer treatment) intentionally stop testosterone production, which also halts spermatogenesis.
- Real-world example: Anabolic steroid abuse (taking synthetic testosterone) shuts down the body’s own GnRH and LH production, leading to shrunken testes and temporary infertility.
Summary in One Line
Hypothalamus → GnRH → Pituitary → LH (→ Leydig cells → testosterone) + FSH (→ Sertoli cells) → Spermatogenesis
(with negative feedback from testosterone and inhibin to keep everything balanced)
No formulas, no numbers — just a chain of chemical commands that turns a factory on, keeps it running, and knows when to stop.
Many learners look this topic up as "Hormonal Regulation Spermatogenesis: Definition, Diagram & Examples", "Hormonal Regulation Spermatogenesis notes class 12 biology", or "NCERT biology syllabus hormonal regulation spermatogenesis". This concept is directly part of the Human Reproduction chapter in the NCERT/CBSE Class 12 Biology syllabus, and it is also an important topic for NEET and state medical/CET entrance exams, making it worth mastering for both board and competitive-exam preparation.
23 chromosomes. A spermatid is haploid, exactly like the secondary spermatocyte it comes from — the second meiotic division (which produces spermatids from secondary spermatocytes) is an EQUATIONAL division, not a reductional one, so it does not halve the chromosome number again.
A spermatid has 23 chromosomes (haploid, n) — the same haploid number as the secondary spermatocyte, since the second meiotic division does not reduce the chromosome number further.
Spermatids have 23 chromosomes — the haploid number — because meiosis II (which produces them) is an equational division, not a further reduction.
Section 2.3 traces the full lineage: a spermatogonium (46 chromosomes, diploid) undergoes mitotic multiplication, and some become primary spermatocytes (still 46). The first meiotic division (meiosis I) is the REDUCTION division — it halves the chromosome number, producing two secondary spermatocytes, each with 23 chromosomes (haploid).
The secondary spermatocytes then undergo the second meiotic division (meiosis II) to form spermatids. Meiosis II is an EQUATIONAL division — like an ordinary mitosis, it separates sister chromatids but does not halve the chromosome number again. So each of the four spermatids produced from one primary spermatocyte retains the same haploid chromosome number as the secondary spermatocyte: 23 chromosomes.
This is exactly what Figure 2.8(a)'s own chromosome-number column shows: 46 (spermatogonia/primary spermatocyte) -> 23 (secondary spermatocyte) -> 23 (spermatids) -> 23 (spermatozoa, after spermiogenesis just repackages the same haploid nucleus).
Each spermatid has 23 chromosomes — the haploid number, unchanged from the secondary spermatocyte, since meiosis II does not reduce the chromosome number further.
Showing the 12 most recent of 13 on this concept.
- CBSE 2026Set ANNUAL1 markQ.Fill in the blank: Leydig cells, synthesise and secrete testicular hormone called as ______.
›Reveal solutionSolution
Leydig (interstitial) cells located between the seminiferous tubules secrete testosterone, the main male sex hormone.
Within the testis, the region outside the seminiferous tubules contains Leydig (interstitial) cells, which synthesise and secrete androgens, principally testosterone, under LH stimulation. Testosterone regulates spermatogenesis and the development of secondary sexual characters in males.
✓Final answerTestosterone.
- CBSE 2025Set X11 markMCQQ.The process of transformation of spermatids into sperms is called(a) Spermatogenesis(b) Spermiogenesis(c) Spermiation(d) Oogenesis
›Reveal solutionSolution
The transformation of spermatids into mature spermatozoa is called spermiogenesis.
During spermatogenesis, spermatids are produced. The subsequent morphological transformation of these non-motile spermatids into motile spermatozoa (sperms) is termed spermiogenesis. Spermatogenesis is the whole process of sperm formation; spermiation is the release of sperms from the Sertoli cells into the seminiferous tubule lumen; and oogenesis is egg formation. Hence the specific term for spermatid-to-sperm transformation is spermiogenesis.
✓Final answer(b) Spermiogenesis
- CBSE 2025Set F1 markMCQQ.Sertoli cells are controlled by which of the following hormones?(a) LH(b) FSH(c) Prolactin(d) GH
›Reveal solutionSolution
Sertoli (nurse) cells are stimulated by FSH from the anterior pituitary.
In the male, the anterior pituitary secretes two gonadotropins. LH (Luteinising Hormone / ICSH) acts on the Leydig (interstitial) cells to stimulate secretion of testosterone (androgens). FSH (Follicle Stimulating Hormone) acts on the Sertoli cells located within the seminiferous tubules; these nurse cells then provide nutrition and factors (such as ABP and inhibin) needed for the maturation of developing sperm. Hence Sertoli cells are under FSH control.
✓Final answer(B) FSH.
- CBSE 2025Set ANNUAL1 markQ.Define spermiogenesis.
›Reveal solutionSolution
Spermiogenesis is the final stage of spermatogenesis where spermatids differentiate structurally into functional sperm.
After meiosis II produces haploid spermatids, these round, non-motile cells undergo a process of structural transformation called spermiogenesis, during which they develop a head (with an acrosome and condensed nucleus), a middle piece (packed with mitochondria for energy) and a tail (flagellum) for motility — converting them into mature, motile spermatozoa capable of fertilising an ovum.
✓Final answerSpermiogenesis = transformation of spermatids into mature, motile spermatozoa.
- CBSE 2025Set ANNUAL1 markMCQQ.There are two statements marked as Assertion (A) and Reason (R). Mark your answer as per the code given below : Assertion (A): From one diploid primary spermatocyte, four haploid sperms are formed. Reason (R): A primary spermatocyte is large and diploid, it contains 46(2n) chromosomes(i) Both (A) and (R) are true and 'Reason' is the corrrect explanation of (A).(ii) Both (A) and (R) are true but 'Reason' is not the correct explanation of (A).(iii) (A) is true but (R) is false.(iv) Both (A) and (R) are false.
›Reveal solutionSolution
Both statements are factually correct, but stating that the primary spermatocyte is diploid with 46 chromosomes does not, by itself, explain why exactly FOUR haploid sperm result — that comes from it undergoing two successive meiotic divisions.
Assertion (A): A primary spermatocyte, which is diploid, gives rise to four haploid sperm — this is true. It first undergoes meiosis I (a reductional division) to form two haploid secondary spermatocytes, and each secondary spermatocyte then undergoes meiosis II (an equational division) to form two spermatids each — giving four spermatids in total, which differentiate (spermiogenesis) into four sperms.
Reason (R): A primary spermatocyte is indeed large and diploid, containing 46 (2n) chromosomes — this is also true.
However, R only describes the ploidy/chromosome number of the starting cell. It does not, by itself, account for WHY the outcome is exactly four cells — that specific outcome depends on the primary spermatocyte undergoing TWO successive meiotic divisions (meiosis I then meiosis II), not merely on the fact that it started out diploid. So R is a true statement but is not the correct/complete explanation of A.
✓Final answerOption (ii) — Both (A) and (R) are true, but (R) is not the correct explanation of (A).
- CBSE 2024Set A11 markMCQQ.The secondary spermatocytes undergo the second meiotic division to produce four equal, haploid(a) Spermatogonium(b) Spermatids(c) Primary spermatocyte(d) Secondary spermatocyte
›Reveal solutionSolution
Secondary spermatocytes complete the second meiotic division to form four haploid spermatids.
During spermatogenesis, a diploid primary spermatocyte undergoes the first meiotic division to give two haploid secondary spermatocytes. Each secondary spermatocyte then undergoes the second meiotic division, producing four equal, haploid spermatids. The spermatids later differentiate into sperms (spermiogenesis).
✓Final answer(b) Spermatids
- CBSE 2024Set ANNUAL1 markMCQQ.LH acts on :(a) Leydig cells(b) Sertoli cells(c) Both (A) & (B)(d) Spermatogonia
›Reveal solutionSolution
Luteinizing Hormone (LH) targets the Leydig (interstitial) cells of the testis.
In the male, the anterior pituitary secretes LH, which acts on the Leydig cells (interstitial cells lying between the seminiferous tubules). LH stimulates these cells to synthesise and secrete androgens, mainly testosterone, which in turn regulates spermatogenesis and the development of secondary sexual characters. FSH, the other gonadotropin, instead acts on the Sertoli cells, stimulating them to secrete factors that help in spermiogenesis.
✓Final answer(a) Leydig cells.
- CBSE 2024Set ANNUAL1 markMCQQ.During spermatogenesis, meiotic division results in the formation of spermatozoa from primary spermatocytes. The total number of meiotic divisions required to produce 400 spermatozoa will be :(a) 200(b) 300(c) 100(d) 50
›Reveal solutionSolution
Each primary spermatocyte undergoes 2 meiotic divisions to give 4 spermatozoa, so producing 400 spermatozoa needs 300 total meiotic divisions.
During spermatogenesis, a primary spermatocyte (diploid, 2n) first undergoes meiosis I to form two secondary spermatocytes (haploid, n). Each secondary spermatocyte then undergoes meiosis II to form two spermatids each, so one primary spermatocyte ultimately gives rise to 4 spermatids (which differentiate into 4 spermatozoa) through a total of 2 meiotic divisions (1 meiosis I + 2 meiosis II, i.e. 1 + 2 = 3 individual division events per primary spermatocyte if counted cell-by-cell: 1 meiosis I of the primary spermatocyte, and 2 separate meiosis II divisions of its two secondary spermatocytes).
To produce 400 spermatozoa:
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Number of primary spermatocytes needed = 400 / 4 = 100
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Meiosis I divisions = 100 (one per primary spermatocyte)
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Meiosis II divisions = 200 (two secondary spermatocytes per primary spermatocyte, each dividing once)
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Total meiotic divisions = 100 + 200 = 300
✓Final answer(b) 300 meiotic divisions are required to produce 400 spermatozoa.
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- CBSE 2023Set ANNUAL1 markQ.Write the name of one sex hormone secreted by human male.
›Reveal solutionSolution
Testosterone is the principal male sex hormone (androgen) secreted by the Leydig cells of the testis.
In the human male reproductive system, the interstitial cells (Leydig cells) present in the testis secrete testosterone under stimulation by luteinising hormone (LH) from the pituitary. Testosterone regulates the development of male secondary sexual characters (facial hair, deepening of voice, muscle growth), supports spermatogenesis in the seminiferous tubules, and maintains the accessory reproductive glands and ducts.
✓Final answerTestosterone, the male sex hormone secreted by the Leydig (interstitial) cells of the testis.
- CBSE 2023Set ANNUAL1 markMCQQ.Leydig cells secretes(a) Estrogens(b) Androgens(c) Progesterone(d) Corticosterone
›Reveal solutionSolution
Leydig (interstitial) cells of the testis secrete androgens (testosterone), which control male secondary sexual characters and spermatogenesis.
The Leydig cells (interstitial cells) are located in the interstitial spaces (regions) between the seminiferous tubules within each testicular lobule. They secrete a group of hormones called androgens, principally testosterone, which regulate the development, maturation, and function of the male accessory sex organs, control secondary sexual characteristics (like facial hair, deep voice), and act along with FSH to stimulate spermatogenesis within the seminiferous tubules. Estrogens and progesterone are mainly female sex hormones (though present in small amounts in males too); corticosterone is a hormone secreted by the adrenal cortex, unrelated to Leydig cells.
✓Final answer(b) Androgens
- CBSE 2022Set ZOOLOGY1 markMCQQ.Which cell organelle of spermatid forms acrosome of sperm?(i) Mitochondria(ii) Golgi body(iii) Ribosome(iv) Lysosome
›Reveal solutionSolution
The acrosome of the sperm is derived from the Golgi body of the spermatid.
As a spermatid matures into a spermatozoon (spermiogenesis), its organelles are reorganised. The Golgi complex collects and condenses hydrolytic enzymes into a membrane-bound vesicle that spreads as a cap over the anterior part of the nucleus - the acrosome. These acrosomal enzymes later help the sperm penetrate the layers of the egg during fertilization. Mitochondria form the sperm's middle-piece (for energy), while ribosomes and lysosomes are not the source of the acrosome.
✓Final answer(ii) Golgi body.
- CBSE 2020Set WK1 markQ.Define spermatogenesis.
›Reveal solutionSolution
Spermatogenesis = formation of sperms from spermatogonia in the testis.
Definition. Spermatogenesis is the process by which the immature male germ cells (spermatogonia) are converted into mature spermatozoa (sperms) inside the seminiferous tubules of the testis.
Outline. Diploid spermatogonia multiply and grow into primary spermatocytes; these undergo meiosis to give haploid secondary spermatocytes and then spermatids; the spermatids finally differentiate (spermiogenesis) into motile sperms. It begins at puberty under the influence of FSH and testosterone.
✓Final answerSpermatogenesis = formation of mature sperms from spermatogonia in the seminiferous tubules of the testis.
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