Seminal plasma, the fluid part of semen, is contributed by: (i) Seminal vesicle (ii) Prostate gland (iii) Uret

NCERT Exemplar · Q4

Q. Seminal plasma, the fluid part of semen, is contributed by:

(i) Seminal vesicle

(ii) Prostate gland

(iii) Urethra

(iv) Bulbourethral gland

(a) i and ii

(b) i, ii and iv

(d) i and iv

Karnataka PUCMCQ· 1mImportance★★★★★

42% · 32/77 Questions

🔒 Locked · start free trial →

You're viewing a preview — the full solution, concept, methods & PYQ mapping are locked.

Start your 14-day free trial to unlock the full solution →

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)

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.
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).
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.
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.

Important

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.

Note

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) …

Start your 14-day free trial to unlock the full solution →

Seminal plasma is the fluid part of semen, and it is contributed by the seminal vesicles, the prostate gland, and the bulbourethral glands — but not by the urethra.

The question asks which structures contribute to seminal plasma, the fluid that carries and nourishes sperm. To answer correctly, you need to know the role of each accessory gland and duct in the male reproductive system.

The seminal vesicles are a pair of glands located behind the bladder. They secrete a thick, alkaline fluid rich in fructose (a sugar that provides energy for sperm), prostaglandins, and clotting proteins. This secretion makes up about 60–70% of the total volume of semen. So (i) is correct.

The prostate gland surrounds the urethra just below the bladder. It secretes a thin, milky, alkaline fluid that contains enzymes, citric acid, and prostate-specific antigen (PSA). This fluid helps activate sperm and neutralises the acidity of the female reproductive tract. It contributes roughly 20–30% of semen volume. So (ii) is correct.

The bulbourethral glands (also called Cowper’s glands) are two small glands located near the base of the penis. They secrete a clear, slippery, alkaline fluid that lubricates the urethra and neutralises any residual acidity from urine. This fluid is released before the main ejaculate and makes up a small but important part of seminal plasma. So (iv) is correct. …

Start your 14-day free trial to unlock the full solution →

Same / Similar Concept — real previous-year questions on the same or a closely similar concept, not this exact question.

KCET 2023Set B-41 markMCQ

Q. From the following table, select the option that correctly characterizes various phases of menstrual cycle: Menstruation phase | Follicular phase | Luteal phase (A) Regeneration of endometrium | High level of progesterone | Developing corpus luteum (B) Matured follicle | Regression of corpus luteum | Ovulation (C) Menses | Developing corpus luteum | Follicle maturation (D) Menses | L.H. Surge | Regeneration of endometrium

›Reveal solution

Eliminate by the menstrual-phase column first (it must be menses), then reject (C) because it puts the corpus luteum in the follicular phase — leaving (D).

1. Establish the true events of each phase

The ~28-day menstrual cycle has three phases:

Phase	Days	What actually happens
Menstrual phase	1–5	Menses — breakdown and shedding of the endometrial lining with blood, because the corpus luteum has regressed and progesterone has fallen
Follicular (proliferative) phase	5–13	Primary follicles grow into a Graafian follicle; FSH and LH rise, culminating in the mid-cycle LH SURGE; oestrogen from the growing follicle drives proliferation of the endometrium
Luteal (secretory) phase	15–28	After ovulation the ruptured follicle becomes the CORPUS LUTEUM, which secretes large amounts of progesterone to prepare/maintain the endometrium for implantation

2. Test the options column by column

Column 1 must be a menstruation-phase event.

(A) "Regeneration of endometrium" ✗ — in menstruation the endometrium breaks down; it does not regenerate. Rejected.
(B) "Matured follicle" ✗ — a matured (Graafian) follicle is the end-point of the follicular phase, not of menstruation. Rejected.
(C) "Menses" ✓ — survives.
(D) "Menses" ✓ — survives.

Column 2 must be a follicular-phase event. Now (C) and (D) are separated: …

Start your 14-day free trial to see the full solution →

KCET 2022Set A-11 markMCQ

Q. Menstrual cycle is exhibited by : (A) Apes (B) Cow (C) Tiger (D) Rat

›Reveal solution

Menstrual cycle = primates only (apes, monkeys, humans); all other mammals show an oestrus cycle.

Step 1 — The distinction the question is testing.

	Menstrual cycle	Oestrus cycle
Shown by	Primates — humans, apes, Old-World monkeys	Non-primate mammals — cow, sheep, dog, tiger, rat, deer
Fate of the unfertilised endometrium	Shed with blood — menstruation	Reabsorbed — no bleeding
Sexual receptivity	Throughout the cycle	Only during "heat" (oestrus)

Step 2 — Apply it to the options.

(A) Apes — primates $\Rightarrow$ menstrual cycle $\checkmark$
(B) Cow — non-primate mammal $\Rightarrow$ oestrus cycle
(C) Tiger — non-primate mammal $\Rightarrow$ oestrus cycle
(D) Rat — non-primate mammal $\Rightarrow$ oestrus cycle (a very short one, ~4–5 days)

Step 3 — Why only primates menstruate. …

Start your 14-day free trial to see the full solution →

KCET 2019Set A-11 markMCQ
$5^{\text{th}}$
›Reveal solutionSolution
Ovulation occurs approximately 14 days before the next expected menses. For a woman whose menses began on 5th April, with a typical 28‑day cycle, ovulation is expected around 19th April — but the closest given option is 18th April.

The concept: why ovulation happens when it does

The menstrual cycle is counted from the first day of one menses to the first day of the next. In a textbook 28‑day cycle, the luteal phase (the time after ovulation until the next menses) is relatively fixed at about 14 days. Ovulation therefore occurs roughly 14 days before the next period, not 14 days after the last one.

This is a common point of confusion. Many students mistakenly count 14 days forward from the start of menses and land on 19th April — which is actually correct for a 28‑day cycle — but the exam often expects the nearest option. Let’s walk through it carefully.

Step‑by‑step reasoning

Identify the cycle length

The question does not state the cycle length explicitly. In standard exam problems, unless told otherwise, assume a 28‑day cycle. This is the most common textbook cycle.

Find the expected date of the next menses

If menses started on 5th April and the cycle is 28 days, the next menses is due on:

$5\text{ April} + 28\text{ days} = 3\text{ May}$

Apply the fixed luteal phase Ovulation occurs about 14 days before the next menses. So:

$3\text{ May} - 14\text{ days} = 19\text{ April}$

Check the options

The options given are:

(A) 18th April

(B) 14th April

(C) 10th April

(D) 29th April

19th April is not listed. The closest is 18th April (option A). …
Start your 14-day free trial to see the full solution →

←Previous questionQ3 — Spot the odd one out from the following structures with reference to t…→Next questionQ5 — Spermiation is the process of the release of sperms from: (a) Seminife…

Q.Seminal plasma, the fluid part of semen, is contributed by:

🎓Unlock everything free for 14 days

Unlock everything free for 14 days