Problem 3 - Campbell Biology

Question

Knowledge/Comprehension Which of the following is not properly paired? (A) seminiferous tubule-cervix (B) vas deferens-oviduct (C) testosterone-estradiol (D) scrotum-labia majora

Step-by-Step Solution

Answer

(C) testosterone-estradiol

Step 1: Identify Paired Structures

Analyze each given pair and determine if the structures are correctly paired based on their functions and locations within male and female reproductive systems.

Step 2: Check Option (A)

The seminiferous tubule is part of the male reproductive system, where sperm is produced. The cervix is part of the female reproductive system, acting as the lower part of the uterus. These do not correspond to each other.

Step 3: Check Option (B)

The vas deferens is a duct in the male reproductive system that transports sperm from the testes to the urethra. The oviduct (or fallopian tube) is part of the female reproductive system where fertilization typically occurs. These also do not correspond to each other.

Step 4: Check Option (C)

Testosterone is a male sex hormone, while estradiol is a form of estrogen, a female sex hormone. These hormones are analogues in male and female reproductive systems and thus can be paired.

Step 5: Check Option (D)

The scrotum is a part of the external male genitalia. The labia majora are parts of the external female genitalia. These are properly paired as analogues.

Step 6: Conclusion

Based on the analysis, the correct answer is the one pair that is not properly matched, which is Option (C): testosterone-estradiol.

Key Concepts

male reproductive system

The male reproductive system is designed to produce, store, and transport sperm, as well as deliver it to the female reproductive system for reproduction.
One of the key components is the **testes**, where sperm is produced in structures called **seminiferous tubules**.
From here, sperm moves into the **epididymis** where it matures.
During ejaculation, sperm travels through the **vas deferens**, a duct that connects the testes to the **urethra**.
The **prostate gland**, **seminal vesicles**, and **bulbourethral glands** contribute fluids to form semen, which nourishes and protects the sperm.

The external structure includes the **penis** and **scrotum**. The scrotum houses the testes and regulates their temperature, which is crucial for sperm production.
The penis is the organ that delivers semen into the female reproductive system during intercourse.

female reproductive system

The female reproductive system is designed to produce eggs, facilitate fertilization, and support the development of a fetus.
The primary organs are the **ovaries**, which produce eggs (ova) and secrete female hormones like estrogen and progesterone.
Each month, an egg is released during **ovulation** and travels down the **oviduct** (fallopian tube) where fertilization by sperm can occur.

The fertilized egg then moves to the **uterus**, a muscular organ where it can implant and develop into a fetus.
The lower part of the uterus is the **cervix**, which opens into the **vagina**, the canal leading to the outside of the body.
During childbirth, the cervix dilates to allow the baby to pass through the vagina.
The external genitalia include the **labia majora**, **labia minora**, **clitoris**, and **vaginal opening**, which collectively are known as the **vulva**.

hormones in reproduction

Hormones play a crucial role in regulating the reproductive systems of both males and females.

In males, the primary hormone is **testosterone**, produced by the testes.
Testosterone is responsible for the development of male secondary sexual characteristics, such as facial hair, deepening of the voice, and increased muscle mass.
It also plays a key role in spermatogenesis, the production of sperm.

In females, the key hormones are **estrogen** and **progesterone**.
Estrogen, including estradiol, helps in the development of secondary sexual characteristics like breast development and regulation of the menstrual cycle.
Progesterone prepares the uterus for pregnancy by thickening the uterine lining to support a fertilized egg.
Both hormones are produced by the ovaries.

Additionally, the **pituitary gland** in the brain releases **follicle-stimulating hormone (FSH)** and **luteinizing hormone (LH)**, which regulate both male and female reproductive functions.
In females, FSH promotes egg development, while LH triggers ovulation.
In males, these hormones stimulate sperm production and testosterone secretion.