Reproduction Test - Zoology, Class 12 - Class 12 MCQ

Male Rabbit Reproductive System
The male rabbit reproductive system consists of various organs involved in the production and transport of sperm. One of the important structures in this system is the Mullerian duct, which is responsible for the development of female reproductive organs in other animals but regresses in males.
Mullerian Duct in Male Rabbit
Among the given options, the correct answer representing the Mullerian duct in male rabbits is Seminal vesicle (B). Here's why:
- Prostatic utricle (A): The prostatic utricle is a structure found in some mammals, including humans, but not in rabbits. It is not related to the Mullerian duct in male rabbits.
- Seminal vesicle (B): The seminal vesicle is an accessory gland in the male reproductive system that secretes a fluid rich in fructose, which provides energy for sperm. In male rabbits, the seminal vesicle is derived from the Mullerian duct, making it the correct answer.
- Cowper's gland (C): The Cowper's gland, also known as the bulbourethral gland, is another accessory gland in the male reproductive system. It produces a clear lubricating fluid that helps in the passage of sperm. However, it is not related to the Mullerian duct in male rabbits.
- Urethra (D): The urethra is a tube that carries urine and semen out of the body. While it is a part of the male reproductive system, it is not specifically related to the Mullerian duct.
In conclusion, the correct representation of the Mullerian duct in male rabbits is the Seminal vesicle (B).

Testes are permanently retained in abdominal cavity in

A: Elephant

B: Whale

C: Armadillo

D: All the above

Answer: D

The testes are permanently retained in the abdominal cavity in all of the above mentioned animals, including elephants, whales, and armadillos. This means that the testes do not descend into a scrotal sac outside the abdominal cavity, as seen in many other mammals.

Here is a detailed explanation:

Elephant:

• Elephants are large mammals, and their testes are located inside the abdominal cavity.


• They do not have a scrotal sac where the testes can descend into.


• This is an adaptation that helps protect the testes from injury while the elephant moves through dense vegetation or during mating.

Whale:

• Whales are marine mammals, and their testes are also located inside the abdominal cavity.


• They do not have a scrotal sac either.


• This adaptation is believed to be related to the hydrodynamic shape of the whale's body, allowing them to move efficiently through the water.

Armadillo:

• Armadillos are small mammals, and their testes are also permanently retained in the abdominal cavity.


• They do not have a scrotal sac.


• This adaptation may be related to their burrowing lifestyle, protecting the testes from potential injury in underground tunnels.

All the above:

• Therefore, the correct answer is option D - all the above mentioned animals have their testes permanently retained in the abdominal cavity.

It is important to note that the permanent retention of testes in the abdominal cavity is a unique characteristic of these animals and is different from most other mammals where the testes descend into a scrotal sac outside the body.

To compare the temperature of the scrotum and the abdominal cavity, we need to consider the normal body temperature and the factors that affect temperature regulation in these areas.
1. Normal body temperature: The normal body temperature is around 37°C (98.6°F).
2. Scrotum temperature: The scrotum is the external pouch of skin that holds the testicles. The temperature of the scrotum is lower than the rest of the body to maintain proper sperm production. This is because sperm production requires a lower temperature than the body's core temperature. The scrotum temperature is usually around 2-4°C (3.6-7.2°F) lower than the abdominal cavity temperature.
3. Abdominal cavity temperature: The abdominal cavity is the space within the abdomen that contains various organs such as the stomach, intestines, liver, and kidneys. The temperature of the abdominal cavity is closer to the body's core temperature, which is around 37°C (98.6°F).
Based on the above information, we can conclude that the temperature of the scrotum is less than the temperature of the abdominal cavity by approximately 2-4°C (3.6-7.2°F).
Therefore, the correct answer is C: 30C.

The outer coat of the seminiferous tubules in the testes is composed of fibrous connective tissue called the Tunica albuginea. It is a dense layer of collagen fibers that surround the seminiferous tubules and provides structural support to the testes. Here is a detailed explanation of the options provided:
A: Tunica propria:
- The tunica propria is a layer of connective tissue found in various organs, but it is not specifically associated with the seminiferous tubules.
B: Lamina propria:
- The lamina propria is another layer of connective tissue found in various organs, but it is not specifically associated with the seminiferous tubules.
C: Plica semilunaris:
- The plica semilunaris is a fold of conjunctiva in the corner of the eye, and it is not related to the seminiferous tubules.
Therefore, the correct answer is D: Tunica albuginea, as it is the fibrous connective tissue that forms the outer coat of the seminiferous tubules in the testes.

Answer:
The vas deferens is a tube that carries sperm from the testicles to the urethra. Cutting the vas deferens is a surgical procedure known as vasectomy, which is performed for male sterilization. It is a permanent method of contraception that prevents sperm from being released during ejaculation.
Reasons for cutting the vas deferens for male sterilization:
- Preventing pregnancy: Vasectomy is a highly effective method of birth control, with a failure rate of less than 1%. It provides long-term contraception without the need for daily pills or other forms of contraception.
- Simplicity and safety: Vasectomy is a relatively simple and safe procedure that can be performed in a doctor's office or clinic. It is usually done under local anesthesia and takes about 15-30 minutes to complete.
- No impact on sexual function: Cutting the vas deferens does not affect a man's ability to have an erection or enjoy sexual pleasure. It only prevents the release of sperm during ejaculation.
- Reversibility: Although vasectomy is considered a permanent form of sterilization, it can sometimes be reversed through a surgical procedure called vasectomy reversal. However, the success of reversal depends on various factors, including the time since the vasectomy and the presence of scar tissue.
In conclusion, cutting the vas deferens is performed for male sterilization, as it provides a reliable and permanent method of contraception for men who no longer wish to father children.

The muscles in the penis during sexual excitation:
There are three types of muscles in the penis, and their actions during sexual excitation can be described as follows:
1. Smooth Muscles:
- These muscles are found in the walls of blood vessels and are responsible for controlling blood flow.
- During sexual excitation, the smooth muscles in the penis relax.
- This relaxation allows the blood vessels to dilate, increasing blood flow to the penis.
- The increased blood flow is essential for achieving and maintaining an erection.
2. Ischiocavernosus Muscles:
- These muscles surround the base of the penis and help support and maintain an erection.
- During sexual excitation, the ischiocavernosus muscles contract.
- This contraction helps to compress the veins that drain blood from the penis, helping to maintain the erection.
3. Bulbospongiosus Muscles:
- These muscles are located on the underside of the penis and surround the urethra.
- During sexual excitation, the bulbospongiosus muscles also contract.
- This contraction helps to propel semen through the urethra during ejaculation.
In summary, during sexual excitation, the muscles in the penis have different actions:
- The smooth muscles relax, allowing increased blood flow to the penis.
- The ischiocavernosus muscles contract, helping to maintain the erection.
- The bulbospongiosus muscles contract, aiding in the propulsion of semen during ejaculation.

Which acid occurs in semen?
The acid that occurs in semen is citric acid. Here is a detailed explanation:
1. Citric acid:
- Citric acid is a weak organic acid that is found in various fruits and vegetables, including citrus fruits.
- It is naturally present in the human body and is involved in several metabolic processes.
- Citric acid is also found in semen, where it serves various functions.
- It provides a source of energy for sperm by participating in the citric acid cycle (also known as the Krebs cycle) within the seminal vesicles.
- Citric acid helps maintain the pH balance in semen, which is necessary for sperm survival and motility.
- The presence of citric acid in semen can be detected through biochemical tests.
2. Other acids not found in semen:
- Malic acid: Although malic acid is naturally present in fruits like apples, it is not found in semen.
- Oxaloacetic acid: Oxaloacetic acid is an intermediate compound in the citric acid cycle, but it is not directly found in semen.
- Succinic acid: Succinic acid is another intermediate compound in the citric acid cycle, but it is not present in semen.
Therefore, the correct answer is A: citric acid.

Secretion of which gland has high percentage of fructose:
- Prostate gland: The prostate gland secretes several substances, including prostate-specific antigen (PSA) and enzymes. However, it does not secrete a high percentage of fructose.
- Cowper's gland: Also known as bulbourethral gland, Cowper's gland secretes a clear, viscous fluid that helps with lubrication during sexual arousal. It does not secrete a high percentage of fructose.
- Seminal vesicle: The seminal vesicles are responsible for producing a significant portion of the fluid that makes up semen. This fluid contains various substances, including fructose. The fructose in the seminal vesicle secretion provides energy for sperm motility.
- Tyson: Tyson glands, also known as preputial glands, are located in the foreskin of the penis. They secrete an oily substance called smegma, but it does not contain a high percentage of fructose.
Therefore, the gland that secretes a high percentage of fructose is the seminal vesicle.

Explanation:
If the testes of a male rabbit are not transferred from the abdominal cavity to the testes sac, the following consequences can occur:
1. Absence of male characters:
- The testes are responsible for the production of testosterone, the male sex hormone.
- Without the testes in the scrotum, there will be a lack of testosterone production.
- Testosterone is crucial for the development of male characteristics such as the growth of facial hair, deepening of the voice, and muscle development.
- Therefore, the absence of testes in the scrotum may result in the absence or underdevelopment of these male characteristics.
2. Development of male reproductive system will not occur:
- The testes play a vital role in the development of the male reproductive system.
- They produce sperm, which is necessary for reproduction.
- If the testes are not transferred to the scrotum, the male reproductive system may not develop properly or may not develop at all.
3. Sperms will not form:
- Sperm production occurs in the testes.
- If the testes remain in the abdominal cavity, the temperature may not be suitable for sperm production.
- Sperms require a slightly lower temperature than the core body temperature to develop properly.
- Therefore, if the testes are not in the scrotum, sperm production may be negatively affected or may not occur at all.
Based on these points, it can be concluded that if the testes of a male rabbit are not transferred from the abdominal cavity to the testes sac, sperms will not form.

The function of seminal fluid is to provide a medium for the movement of sperm. Seminal fluid is a mixture of fluids produced by various glands in the male reproductive system. It is released during ejaculation and plays a crucial role in supporting the survival and transport of sperm.
The key functions of seminal fluid include:
1. Transport medium: Seminal fluid provides a medium for the movement of sperm from the male reproductive tract to the female reproductive tract. It helps to propel and nourish the sperm, allowing them to swim towards the egg.
2. Nourishment: Seminal fluid contains various nutrients, including fructose, amino acids, enzymes, and vitamins, which provide energy and nourishment to the sperm. This helps the sperm to maintain their motility and viability.
3. Protection: Seminal fluid contains substances that protect the sperm from the acidic environment of the female reproductive tract. It helps to neutralize the acidity and provides a more favorable environment for the sperm to survive and fertilize the egg.
4. Lubrication: Seminal fluid acts as a lubricant during sexual intercourse, facilitating the movement of the penis in the vagina. This helps to enhance sexual pleasure and reduce friction, making the sexual experience more comfortable.
5. Enhancing fertility: Seminal fluid contains substances that enhance the fertilization process. It helps to activate the sperm, preparing them for fertilization and increasing their chances of successfully penetrating the egg.
In summary, seminal fluid plays a vital role in supporting the movement, nourishment, protection, and fertilization of sperm. It provides a suitable environment for the sperm to reach and fertilize the egg, ultimately contributing to successful reproduction.

Explanation:
The vasa efferentia are small, coiled tubules that connect the testes with the epididymis in the male reproductive system. They play a crucial role in transporting sperm from the testes to the epididymis, where they mature and are stored before ejaculation.
Key Points:
- The vasa efferentia are part of the male reproductive system.
- They connect the testes with the epididymis.
- Their primary function is to transport sperm from the testes to the epididymis.
- Sperm mature and are stored in the epididymis before ejaculation.
- Option A, "Testes with epididymis," is the correct answer.
Conclusion:
The vasa efferentia connect the testes with the epididymis in the male reproductive system.

Explanation:
The development of the uterus-masculinus in mammals is derived from the Müllerian duct.
Reasoning:
The development of the reproductive organs in mammals involves the differentiation of two sets of ducts - the Wolffian ducts and the Müllerian ducts. The Müllerian ducts are responsible for the development of female reproductive structures, including the uterus, fallopian tubes, and upper part of the vagina.
On the other hand, the Wolffian ducts are responsible for the development of male reproductive structures, including the epididymis, vas deferens, and seminal vesicles.
In mammals, the uterus-masculinus is a structure found in some species of male mammals, such as rodents and rabbits. It is derived from the Müllerian ducts, which normally regress in males during embryonic development. However, in certain species, the Müllerian ducts persist and give rise to the uterus-masculinus.
Therefore, the correct answer is C: Müllerian duct.

Explanation:
The failure of the testes to descend into the scrotum is known as cryptorchidism.
Details:
Cryptorchidism is a condition where one or both testes fail to descend into the scrotum. It is a common condition in male infants and may also occur in adult males.
Here is some more information about cryptorchidism:
- Cryptorchidism is usually diagnosed at birth or during early childhood. If the testes do not descend on their own within the first few months of life, medical intervention may be required.
- The exact cause of cryptorchidism is unknown, but it is believed to be a combination of genetic and hormonal factors.
- If left untreated, cryptorchidism can lead to complications such as infertility and an increased risk of testicular cancer.
- Treatment for cryptorchidism typically involves surgical intervention to bring the undescended testes into the scrotum. This is usually done before the age of 1 to improve long-term outcomes.
In conclusion, the correct answer is C: Cryptorchidism.

Clupein protein occurs in:
- Human sperms
- Avian sperms
- Human ova
Detailed
Clupein protein is found in multiple sources, including human sperms, avian sperms, and human ova. Here is a detailed explanation:
1. Human Sperms:
- Clupein protein is present in human sperms. This protein plays a crucial role in sperm function and fertility.
2. Avian Sperms:
- Clupein protein is also found in avian sperms. Avian species, such as birds, produce sperm cells that contain clupein protein.
3. Human Ova:
- Clupein protein is present in human ova, which are the female reproductive cells or eggs. This protein is involved in various processes related to egg development and fertilization.
4. All the Above:
- Therefore, the correct answer is option D: All the above. Clupein protein is present in human sperms, avian sperms, and human ova.
In summary, clupein protein occurs in human sperms, avian sperms, and human ova. This protein plays important roles in sperm function, egg development, and fertilization.

Development of Testis Partitions:
The partitions of the testis develop from different structures within the reproductive system. Let's examine each option and determine which one is correct.
A: Tunica albuginea:
- The tunica albuginea is a fibrous capsule that surrounds the testis.
- It provides structural support and protection to the testis.
- However, it does not give rise to the partitions of the testis.
B: Tunica vasculosa:
- The tunica vasculosa is a network of blood vessels that supply the testis.
- It helps in the transportation of nutrients and oxygen to the developing testis.
- However, it does not play a role in the formation of the testis partitions.
C: Tunica vaginalis:
- The tunica vaginalis is a serous membrane that covers the testis.
- It consists of two layers, the visceral layer, which is closely attached to the testis, and the parietal layer, which lines the scrotal cavity.
- The tunica vaginalis does not contribute to the development of the partitions of the testis.
D: Rete testis:
- The rete testis is a network of tubules located at the mediastinum testis.
- It serves as a collecting system for the spermatozoa produced in the seminiferous tubules.
- While the rete testis is involved in the transportation of spermatozoa, it does not give rise to the partitions of the testis.
Therefore, the correct answer is A: Tunica albuginea. The partitions of the testis develop from the tunica albuginea.

Vasa-efferentia posses:
- Peristalsis: The vasa efferentia are responsible for the movement of sperm from the rete testis to the epididymis. This movement is achieved through peristalsis, which is the coordinated contraction and relaxation of the smooth muscle in the walls of the vasa efferentia.
- Secretory cells: The vasa efferentia are lined with secretory cells that produce and release substances necessary for the transportation and maturation of sperm. These secretions help provide nutrients and support for the sperm as they pass through the vasa efferentia.
- Ciliated cells: The vasa efferentia also contain ciliated cells on their inner lining. These cilia have a waving motion that helps to propel the sperm forward through the vasa efferentia and towards the epididymis.
- Opening for seminal vesicle: At the end of the vasa efferentia, there is an opening that connects to the seminal vesicle. This opening allows for the passage of seminal fluid, which contains additional nutrients and substances that are important for the function and survival of sperm.
In summary, the vasa efferentia possess peristalsis for the movement of sperm, secretory cells for the production and release of substances, ciliated cells for propulsion, and an opening for the connection to the seminal vesicle.

Explanation:
The vas deferens is a tube in the male reproductive system that carries sperm from the epididymis to the urethra. It is responsible for transporting sperm during ejaculation.
The correct answer is option A: Cauda-epididymis. The vas deferens arises from the cauda (tail) of the epididymis, which is the part of the male reproductive system where sperm are stored and matured.
Here is a breakdown of the options and why they are incorrect:
- Option B: Caput epididymis. The caput (head) of the epididymis is not the origin of the vas deferens. It is the initial part of the epididymis where sperm enter from the efferent ductules.
- Option C: Corpus-epididymis. The corpus (body) of the epididymis is not the origin of the vas deferens. It is the middle part of the epididymis where sperm continue to mature.
- Option D: Rete testis. The rete testis is a network of tubules within the testis, and it is not the origin of the vas deferens. Sperm enter the rete testis from the seminiferous tubules and then pass through the efferent ductules to reach the epididymis.
Therefore, the correct answer is option A: Cauda-epididymis, as the vas deferens arises from the cauda of the epididymis.

Common duct formed by union of vas-deferens and duct from seminal vesicle is:
The correct answer is Ejaculatory duct (C).
Explanation:
The common duct formed by the union of the vas deferens and the duct from the seminal vesicle is called the ejaculatory duct. Here is a detailed explanation of why the ejaculatory duct is the correct answer:
- Vas deferens: The vas deferens is a tube that carries sperm from the testes to the urethra. It is a part of the male reproductive system.
- Duct from seminal vesicle: The seminal vesicle is a gland located behind the bladder. It produces a fluid that mixes with sperm to form semen. The duct from the seminal vesicle carries this fluid to the ejaculatory duct.
- Ejaculatory duct: The ejaculatory duct is a short duct that connects the vas deferens with the urethra. It is formed by the union of the vas deferens and the duct from the seminal vesicle.
- Function: The ejaculatory duct plays a crucial role in ejaculation. During ejaculation, sperm from the testes, along with the fluid from the seminal vesicle, pass through the ejaculatory duct and mix with other fluids in the urethra to form semen. Semen is then expelled from the body through the urethra during ejaculation.
In conclusion, the common duct formed by the union of the vas deferens and the duct from the seminal vesicle is the ejaculatory duct.

Mesorchium is the peritoneal covering of the Testis.
The mesorchium is a double-layered fold of peritoneum that attaches the testis to the posterior abdominal wall. It extends from the posterior aspect of the testis to the posterior abdominal wall, passing through the inguinal canal.
Here is a detailed explanation:
1. Peritoneal covering: The mesorchium is a peritoneal covering that surrounds and supports the testis. The peritoneum is a serous membrane that lines the abdominal cavity and covers many of the abdominal organs.
2. Attachment to the testis: The mesorchium attaches to the posterior surface of the testis. It forms a fold around the testis, providing support and stability.
3. Extension to the abdominal wall: The mesorchium extends from the testis to the posterior abdominal wall. It passes through the inguinal canal, which is a passage in the lower abdominal wall.
4. Function: The mesorchium helps to suspend and position the testis within the scrotum. It also provides a pathway for blood vessels, nerves, and the vas deferens to reach the testis.
In conclusion, the mesorchium is the peritoneal covering of the testis. It plays a crucial role in supporting and positioning the testis within the scrotum.

Scrotum communicates with abdominal cavity through the inguinal canal.
The inguinal canal is a passage in the lower abdominal wall that connects the abdominal cavity with the scrotum. It allows structures such as blood vessels, nerves, and the spermatic cord to pass between the two areas. Here is a detailed explanation of how the scrotum communicates with the abdominal cavity through the inguinal canal:
1. Anatomy of the inguinal canal:
- The inguinal canal is located in the lower abdominal wall, just above the inguinal ligament.
- It is a tubular structure that measures about 4-6 cm in length.
- The canal is formed by layers of abdominal muscles, including the external oblique, internal oblique, and transversus abdominis muscles.
- It is lined with a layer of fascia called the inguinal canal fascia.
2. Passage of structures:
- The inguinal canal serves as a pathway for various structures to pass between the abdominal cavity and the scrotum.
- The spermatic cord, which contains the vas deferens, testicular artery, and veins, as well as nerves, passes through the inguinal canal.
- The inguinal canal also allows the descent of the testes during fetal development.
3. Inguinal hernias:
- The inguinal canal is a common site for hernias to develop.
- An inguinal hernia occurs when there is a weakness in the abdominal wall, allowing abdominal contents to protrude into the inguinal canal and sometimes into the scrotum.
- This can cause pain, discomfort, and a visible bulge in the groin area.
In summary, the scrotum communicates with the abdominal cavity through the inguinal canal. This canal provides a pathway for structures such as the spermatic cord to pass between the two areas. Understanding the anatomy and function of the inguinal canal is essential in diagnosing and managing conditions such as inguinal hernias.

Tunica albuginea is the covering around the:
- Testis
The tunica albuginea is a dense fibrous capsule that surrounds the testis. It provides support and protection to the testis.
- Oviduct
The oviduct, also known as the fallopian tube, is not surrounded by the tunica albuginea. The oviduct has its own specialized structures and layers.
- Kidney
The kidney is not surrounded by the tunica albuginea. It is covered by a fibrous capsule called the renal capsule.
- Heart
The heart is not surrounded by the tunica albuginea. It is covered by the pericardium, a double-layered sac that protects and supports the heart.
Therefore, the correct answer is B: Testis. The tunica albuginea is the covering around the testis.

The functional unit of testis in man is the seminiferous tubules.
The seminiferous tubules are the main structures within the testes where sperm production takes place. These tubules are coiled structures located within the testes and are responsible for the production and maturation of sperm cells. Here is a detailed explanation of the functional unit of the testis:
- Structure of the testis: The testes are paired reproductive organs located in the scrotum. Each testis is composed of several lobules, and within each lobule, there are numerous seminiferous tubules.
- Seminiferous tubules: The seminiferous tubules are long, coiled structures that make up the majority of the testicular tissue. They are lined with specialized cells called Sertoli cells, which provide support and nourishment to developing sperm cells.
- Sperm production: The seminiferous tubules are responsible for the production of sperm cells through a process called spermatogenesis. Spermatogenesis involves the differentiation and maturation of spermatogonia (immature sperm cells) into fully developed sperm cells.
- Hormonal regulation: The seminiferous tubules are under the influence of hormones, such as follicle-stimulating hormone (FSH) and testosterone. FSH stimulates the Sertoli cells to support sperm production, while testosterone is essential for the maturation of sperm cells.
- Transport of sperm: Once sperm cells are produced within the seminiferous tubules, they are transported to the epididymis for further maturation and storage before ejaculation.
In conclusion, the seminiferous tubules are the functional units of the testis in man. They play a crucial role in the production, maturation, and transport of sperm cells necessary for reproduction.

Testosterone is secreted by Leydigs cells in the testis.
Leydigs cells are located in the interstitial tissue of the testis and play a crucial role in the production of testosterone. Testosterone is the primary male sex hormone and is responsible for the development and maintenance of male reproductive organs and secondary sexual characteristics.
Here is a detailed explanation of the secretion of testosterone by Leydigs cells:
1. Leydigs cells:
- Leydigs cells, also known as interstitial cells of the testis, are found in the spaces between the seminiferous tubules in the testis.
- These cells are responsible for the production and secretion of testosterone.
2. Production of testosterone:
- Leydigs cells possess a unique enzyme called 17β-hydroxysteroid dehydrogenase, which converts cholesterol into testosterone.
- Cholesterol is obtained from the bloodstream and transported into Leydigs cells.
- Inside Leydigs cells, cholesterol is converted into pregnenolone, which is then converted into testosterone through a series of enzymatic reactions.
3. Regulation of testosterone secretion:
- The secretion of testosterone by Leydigs cells is regulated by a complex feedback mechanism involving the hypothalamus and pituitary gland.
- The hypothalamus releases gonadotropin-releasing hormone (GnRH), which stimulates the pituitary gland to release luteinizing hormone (LH).
- LH acts on Leydigs cells, promoting the synthesis and secretion of testosterone.
- Testosterone exerts a negative feedback on the hypothalamus and pituitary, inhibiting the release of GnRH and LH, respectively, to maintain a balance.
In conclusion, testosterone is primarily secreted by Leydigs cells in the testis. These cells convert cholesterol into testosterone through a series of enzymatic reactions. The secretion of testosterone is regulated by a feedback mechanism involving the hypothalamus and pituitary gland.

Penile Urethra
The penile urethra is a part of the male reproductive system that carries urine from the bladder out of the body. It also serves as the conduit for sperm during ejaculation. It traverses through different structures in the penis.
Corpora Cavernosa
The corpora cavernosa are two cylindrical spaces that run along the length of the penis. They are responsible for the erection of the penis during sexual arousal. However, the penile urethra does not pass through the corpora cavernosa.
Corpus Spongiosum
The corpus spongiosum is a single cylindrical space that surrounds the penile urethra. It is located on the ventral side of the penis and contains numerous blood vessels. The penile urethra traverses through the corpus spongiosum, allowing the passage of urine and semen.
Corpus Callosum
The corpus callosum is a structure in the brain that connects the two cerebral hemispheres. It is not related to the penile urethra.
Corpus Striatum
The corpus striatum is a part of the basal ganglia in the brain. It is involved in motor control and reward-based learning. It is not associated with the penile urethra.
Conclusion
The correct answer is B: Corpus spongiosum. The penile urethra traverses through the corpus spongiosum, which is a cylindrical space located on the ventral side of the penis.

Seminiferous tubules are composed of:
The seminiferous tubules are the functional units of the testes where sperm production occurs. They are composed of several cell types that work together to produce and transport sperm.
- Germinal epithelium: The inner lining of the seminiferous tubules is made up of a specialized type of epithelial cells called the germinal epithelium. These cells are responsible for sperm production through a process called spermatogenesis.
- Spermatogonia: Spermatogonia are the stem cells within the germinal epithelium that give rise to sperm cells. They undergo a series of divisions and differentiations to produce mature sperm cells.
- Glandular epithelium: The seminiferous tubules also contain glandular epithelial cells that secrete fluid and nutrients to support the development and maturation of sperm cells.
- Sensory epithelium: The term "sensory epithelium" is not applicable to seminiferous tubules. The function of the seminiferous tubules is primarily related to sperm production and not sensory perception.
Therefore, the correct answer is D: Germinal epithelium.

The correct answer is C: Extra-abdominal cavity. Here is a detailed explanation:
1. Introduction:
Mammals are a class of animals that possess internal testes. The location of the testes can vary among different mammalian species. In most mammals, the testes are located outside the abdominal cavity.
2. Extra-abdominal cavity:
The extra-abdominal cavity refers to the space outside the abdominal cavity. This cavity is also known as the scrotal sac or scrotum. It is a unique structure found only in male mammals and serves as the location for the testes.
3. Purpose of the extra-abdominal cavity:
The extra-abdominal location of the testes serves several important functions, including:
- Temperature regulation: The testes need to be kept at a slightly lower temperature than the rest of the body for optimal sperm production. The extra-abdominal cavity provides a cooler environment, which is necessary for the development and maturation of sperm.
- Protection: Placing the testes outside the abdominal cavity reduces the risk of damage from internal organs or external injuries. The scrotum acts as a protective covering for the testes.
4. Other options:
Now, let's briefly discuss the other options mentioned in the question:
- A: Abdominal cavity: While some animals, such as rodents, may have testes located in the abdominal cavity, it is not the general location for mammalian testes.
- B: Thoracic cavity: The thoracic cavity contains organs such as the lungs and heart. It is not a suitable location for the testes as it lacks the necessary conditions for sperm production and protection.
- D: Pericardial cavity: The pericardial cavity is the space surrounding the heart. It is not a suitable location for the testes and is not found in mammals.
Conclusion:
In conclusion, mammalian testes are located in the extra-abdominal cavity or scrotum. This location provides the necessary conditions for temperature regulation and protection, which are crucial for sperm production and overall reproductive function in mammals.

Sustentacular cells are found in the testis of mammals.
- Sustentacular cells, also known as Sertoli cells, are specialized cells found in the testis.
- These cells are located within the seminiferous tubules, which are responsible for the production of sperm.
- Sustentacular cells provide support and nourishment to developing sperm cells.
- They form a barrier between the developing sperm cells and the bloodstream, creating a microenvironment necessary for spermatogenesis.
- Sustentacular cells also produce various hormones and growth factors that regulate the process of sperm production.
- They play a crucial role in the development and maturation of sperm cells.
- In addition to their supportive functions, sustentacular cells also help in the removal of defective or damaged sperm cells.
- These cells are unique to the testis and are not found in other reproductive organs or species.
- The presence of sustentacular cells in the testis is essential for the proper functioning of the male reproductive system.
Therefore, the correct answer is A: Testis of mammal.

Answer:
The bundles of muscles in the penis are called the corpora cavernosa and the corpus spongiosum.
Corpora cavernosa:
- The corpora cavernosa are two cylindrical bundles of erectile tissue located on the upper side of the penis.
- They are responsible for the majority of the erectile response during sexual arousal.
- The corpora cavernosa contain a network of blood vessels that become engorged with blood during an erection, causing the penis to become firm and erect.
Corpus spongiosum:
- The corpus spongiosum is a single midline erectile tissue that surrounds the urethra, which carries urine and semen.
- It is located on the underside of the penis and extends to the glans penis (the tip of the penis).
- The corpus spongiosum helps to maintain the urethra open during an erection and also contributes to the rigidity of the penis.
Conclusion:
Both the corpora cavernosa and the corpus spongiosum are bundles of muscles in the penis. The corpora cavernosa are responsible for the majority of the erectile response, while the corpus spongiosum surrounds the urethra and helps to maintain its openness during an erection.

Glans penis is covered by the prepuce.

• Prepuce: The prepuce, also known as the foreskin, is a fold of skin that covers the glans penis.

Explanation:

• The glans penis is the sensitive tip or head of the penis.


• The prepuce is a retractable fold of skin that covers and protects the glans penis.


• During circumcision, the prepuce is surgically removed, leaving the glans penis exposed.


• The prepuce serves several functions, including protecting the glans penis, maintaining moisture, and enhancing sexual pleasure.


• In some cases, the prepuce may be too tight or difficult to retract, a condition known as phimosis, which may require medical intervention.


• It is important to note that not all individuals have a prepuce, as circumcision is a common cultural or religious practice in some parts of the world.

Conclusion:

In summary, the glans penis is covered by the prepuce, a retractable fold of skin that serves to protect and enhance the sensitivity of the glans penis.

Lutein cells are found in:
- Corpus luteum: The corpus luteum is a temporary endocrine structure that develops from the ruptured ovarian follicle after ovulation. It secretes hormones, including progesterone, and contains lutein cells. These cells are responsible for producing and releasing luteinizing hormone (LH) and estrogen.
- Primary follicle: The primary follicle is an early stage of follicular development in the ovary. It is characterized by the presence of an oocyte (immature egg cell) surrounded by a single layer of granulosa cells. Lutein cells are not typically found in the primary follicle.
- Corpus albicans: The corpus albicans is a degenerated form of the corpus luteum. It is formed when the corpus luteum regresses and undergoes fibrosis. Lutein cells are not present in the corpus albicans.
- All: The correct answer is C: Corpus luteum. Lutein cells are specifically found in the corpus luteum.
In summary, lutein cells are only found in the corpus luteum, which is a temporary endocrine structure formed from the ruptured ovarian follicle after ovulation. These cells play a crucial role in hormone secretion and are responsible for producing and releasing luteinizing hormone (LH) and estrogen. They are not found in the primary follicle or corpus albicans.