Theriogenology MCQS Set 3
51. The corpus luteum is a principal source of:
a) Prostaglandin F2a
b) Estradiol
c) Testosterone
d) Progesterone
Correct Answer: d) Progesterone
Explanation: The Corpus Luteum (CL) is a temporary endocrine structure formed from the follicle after ovulation. Its primary function is the secretion of progesterone, which is essential for maintaining the uterine environment during pregnancy and inhibiting further ovulations.
52. In the mare, foal heat occurs:
a) 21-30 days after foaling
b) 21-30 hours after foaling
c) 7-13 days after foaling
d) 7-13 hours after foaling
Correct Answer: c) 7-13 days after foaling
Explanation: Foal heat is the first estrus that occurs in a mare after giving birth. It typically begins within 7 to 13 days postpartum. While mares can be bred during this heat, conception rates are generally lower than in subsequent cycles.
53. At puberty, a female attains about:
a) 100% of its mature body weight
b) 30% of its mature body weight
c) 90% of its mature body weight
d) 60% of its mature body weight
Correct Answer: d) 60% of its mature body weight
Explanation: Puberty in heifers and other domestic ruminants is closely linked to growth. It generally occurs when the animal reaches approximately 60% of its projected mature body weight, provided the minimum age for that breed has been met.
54. A corpus luteum of pregnancy is also known as:
a) Corpus luteum spurium
b) Corpus luteum verum
c) Corpus haemorrhagicum
d) Corpus albican
Correct Answer: b) Corpus luteum verum
Explanation: The Corpus Luteum Verum (true CL) is the CL that persists throughout pregnancy. In contrast, the CL of a normal estrous cycle that regresses is called the Corpus Luteum Spurium (false CL).
55. In a pregnant cow, placentomes can be palpated per rectum as early as:
a) 30th day of gestation
b) 65th day of gestation
c) 90th day of gestation
d) 120th day of gestation
Correct Answer: c) 90th day of gestation
Explanation: While the fetal membrane slip can be felt at 35 days and the fetus at 65 days, the placentomes (the button-like attachment points) become large enough to be clearly and reliably palpated per rectum starting around day 90.
56. Ovarian cells that respond to FSH are:
a. Theca interna
b. Granulosa
c. Interstitial ovarian cells
d. Theca externa cells
Correct Answer: b. Granulosa
Explanation: Follicle Stimulating Hormone (FSH) binds to receptors on the granulosa cells to stimulate follicular growth and the conversion of androgens to estrogens. The theca interna cells primarily respond to LH to produce those androgens.
57. What is the chemical nature of GnRH?
a. Fatty acid
b. Polypeptide
c. Steroid
d. Glycoprotein
Correct Answer: b. Polypeptide
Explanation: Gonadotropin-Releasing Hormone (GnRH) is a decapeptide (a polypeptide consisting of 10 amino acids). It is produced in the hypothalamus and triggers the release of FSH and LH from the anterior pituitary.
58. The inhibin hormone selectively suppresses the secretion of:
a. FSH and LH
b. LH only
c. FSH only
d. eCG
Correct Answer: c. FSH only
Explanation: Inhibin is produced by the granulosa cells of the follicle. Its specific physiological role is to exert negative feedback on the anterior pituitary to selectively suppress FSH secretion without affecting LH.
59. Oxytocin is stored in and released from the:
a. Neurohypophysis
b. Adenohypophysis
c. Hypothalamus
d. None of the above
Correct Answer: a. Neurohypophysis
Explanation: Oxytocin is synthesized in the paraventricular and supraoptic nuclei of the hypothalamus but is transported down axons to be stored and released from the Neurohypophysis (posterior pituitary).
60. Which is the main luteolytic hormone in mammals?
a. FSH
b. LH
c. eCG
d. PGF2a
Correct Answer: d. PGF2a
Explanation: Prostaglandin F2-alpha ($\text{PGF}_{2\alpha}$) is the primary luteolysin in most domestic mammals. It is secreted by the endometrium (in the absence of an embryo) to cause the regression of the Corpus Luteum.
61. Which gland secretes melatonin hormone?
a. Anterior Pituitary
b. Posterior Pituitary
c. Thymus
d. Pineal
Correct Answer: d. Pineal
Explanation: The Pineal gland secretes melatonin in response to darkness. This hormone plays a vital role in regulating seasonal breeding in species like the sheep (short-day breeders) and the mare (long-day breeders).
62. From which germ layer of embryo internal reproductive organs develops?
a. Ectoderm
b. Mesoderm
c. Endoderm
d. Trophoblast
Correct Answer: b. Mesoderm
Explanation: The Mesoderm is the germ layer responsible for the development of the skeletal, muscular, urinary, and reproductive systems (including the gonads and duct systems).
63. Fructose, a source of energy for spermatozoa, is found primarily in secretions from the:
a) Testis
b) Epididymis
c) Prostate
d) Seminal vesicles
Correct Answer: d) Seminal vesicles
Explanation: The seminal vesicles (vesicular glands) secrete a fluid rich in fructose, which serves as the primary glycolytic energy substrate for sperm motility after ejaculation.
64. Average ejaculation volume in a normal adult ram is:
a). 0.5-2 ml
b). 3-4 ml
c). 5-10 ml
d). None of the above
Correct Answer: a). 0.5-2 ml
Explanation: The ram produces a very low volume of semen (0.5-2 ml) but it is extremely concentrated, often containing billions of sperm per milliliter.
65. For cow A.I. with liquid semen, recommended number of motile spermatozoa per semen dose is:
a. 1 billion
b. 10 million
c. 40 million
d. 70 million
Correct Answer: b. 10 million
Explanation: For liquid (chilled) semen, lower numbers are required than for frozen semen. Usually, 10 million motile sperm is sufficient for high fertility, whereas frozen-thawed doses typically require 20-40 million.
66. The primary circulating androgen in animal body is:
a. Androstenidione
b. Testosterone
c. Dihydrotestosterone
d. Estradiol
Correct Answer: b. Testosterone
Explanation: Testosterone is the principal androgen secreted by the Leydig cells of the testes. While Dihydrotestosterone (DHT) is more potent at the cellular level in certain tissues, testosterone is the primary circulating form.
67. The sac-like organelle on the anterior portion of the sperm head is known as:
a. Acrosine
b. Acrosome
c. Acrocentric
d. Lysosome
Correct Answer: b. Acrosome
Explanation: The Acrosome is a specialized lysosome-like organelle that caps the anterior half of the sperm nucleus. It contains enzymes (like acrosin) required to penetrate the egg’s protective layers.
68. Absence of sperm in the semen is called:
a. Azoospermia
b. Haemospermia
c. Anspermia
d. Oligospermia
Correct Answer: a. Azoospermia
Explanation: Azoospermia is the medical term for the complete absence of spermatozoa in the ejaculate. Aspermia refers to the complete lack of ejaculate volume altogether.
69. The descend of testes into scrotum takes place in cattle at:
a. One month after delivery
b. One month before delivery
c. 100-115 days of gestation
d. At the time of delivery
Correct Answer: c. 100-115 days of gestation
Explanation: In cattle, testicular descent occurs in utero, typically between days 100 and 115 of gestation. In contrast, in dogs and horses, it often occurs much closer to or after birth.
70. The seminal vesicles are:
a. Absent in dog and cat
b. Present in dog and cat
c. Absent in cattle
d. Absent in the horse
Correct Answer: a. Absent in dog and cat
Explanation: Carnivores (dogs and cats) lack seminal vesicles (vesicular glands). The dog only has a prostate gland, while the cat has both a prostate and bulbourethral glands.
71. In the stallion the prostate gland is:
a. Wholly external
b. Partially external
c. Half external and half internal
d. None of the statements is correct
Correct Answer: d. None of the statements is correct
Explanation: In the stallion, the prostate gland is a distinct, multi-lobed structure that is internal, located on the pelvic floor at the neck of the bladder. The provided options “external/internal” usually refer to the “disseminate/body” parts of the prostate found in ruminants.
72. Spermatozoa contain lactic dehydrogenase enzyme:
a. More than seminal plasma
b. Less than seminal plasma
c. Equal to seminal plasma
d. None of the statements is correct
Correct Answer: a. More than seminal plasma
Explanation: Lactic dehydrogenase (LDH) is an intracellular enzyme. In a healthy sample, its concentration is significantly higher within the spermatozoa themselves than in the surrounding seminal plasma. High levels in the plasma usually indicate sperm cell damage.
73. Important cations of mammalian seminal plasma are:
a. Calcium and sodium
b. Sodium and potassium
c. Potassium and calcium
d. Calcium and magnesium
Correct Answer: b. Sodium and potassium
Explanation: The primary cations in seminal plasma are sodium ($\text{Na}^{+}$) and potassium ($\text{K}^{+}$). Sodium is the predominant extracellular cation, while potassium levels are higher than in blood plasma to support sperm function.
74. Spermiogenesis has the following phases:
a. Golgi, cap and maturation phases
b. Golgi, acrosomal and maturation phases
c. Cap, acrosomal and maturation phases
d. Golgi, cap, acrosomal and maturation phases
Correct Answer: d. Golgi, cap, acrosomal and maturation phases
Explanation: Spermiogenesis (the transformation of spermatids into spermatozoa) consists of four distinct phases: the Golgi phase, the Cap phase, the Acrosomal phase, and the Maturation phase.
75. The duration of spermatogenesis in ram is:
a. 54-63 days
b. 64-74 days
c. 38-44 days
d. 40-49 days
Correct Answer: d. 40-49 days
Explanation: The entire process of spermatogenesis in the ram takes approximately 47 to 49 days. This is faster than in the bull (~60 days) or the man (~74 days).