Reproductive and Hormonal Functions of the Male (and Function of the Pineal Gland)
Physiology, MBBS Second Year. This chapter is split into 10 topics and has
386 practice questions. The topics covered are listed below, followed by
10 free sample questions from the chapter.
Topics in this chapter
Male reproductive anatomy, spermatogenesis & hormonal control46 questions
Sperm formation, maturation & the epididymis42 questions
Male sexual act & testosterone secretion/metabolism39 questions
Functions of testosterone40 questions
Mechanism of testosterone action & hormonal control36 questions
Male climacteric, prostate abnormalities, hypogonadism & testicular tumours39 questions
Function of the pineal gland in controlling seasonal fertility30 questions
Sample questions: Reproductive and Hormonal Functions of the Male (and Function of the Pineal Gland)
10 sample questions with the correct answer and an explanation. Try to answer each one before reading the explanation.
Q1. Why must sperm undergo maturation and later capacitation before they can fertilize an ovum?
A. Because sperm acquire mitochondria only in the female tract
B. Because epididymal sperm are immotile with suppressed metabolism and their acrosomes are stabilized, so they need maturation for motility and capacitation in the female tract to release acrosomal enzymes(correct answer)
C. Because epididymal sperm lack a nucleus
D. Because capacitation produces the acrosome
Answer: B.Epididymal sperm are non-motile with motility suppressed by inhibitory proteins and their acrosomes stabilized by cholesterol; maturation on ejaculation (with Sertoli cell secretions) enables full motility, and capacitation in the female tract removes inhibitory factors, reduces acrosomal cholesterol and increases calcium permeability so that the acrosome can release its enzymes for fertilization.
Q2. Why does the ejaculate contain contributions from several glands rather than sperm alone?
A. Because each secretion serves a distinct purpose — nutrition and prostaglandin-mediated transport, buffering of vaginal acid, and clotting with later liquefaction — all needed for sperm survival and delivery(correct answer)
B. Because sperm cannot survive without fructose alone
C. Because buffering alone suffices
D. Because clotting is the only requirement
Answer: A.Seminal vesicle fluid supplies fructose for nutrition, prostaglandins to aid transport and fibrinogen for clotting; prostatic fluid supplies alkaline citrate and phosphate for buffering of the acidic female tract along with the clotting enzyme and profibrinolysin for clotting and later liquefaction — so the combined ejaculate provides nutrition, transport, buffering and clot regulation essential for fertility.
Q3. How does increased calcium permeability assist the sperm?
A. Calcium blocks the acrosome reaction
B. Calcium provides the energy for motility
C. Calcium ions cause changes in the membrane covering the acrosome, making it possible for the acrosome to release its enzymes; without these changes the sperm cannot penetrate the ovum(correct answer)
D. Calcium dissolves the zona pellucida directly
Answer: C.The increase in sperm permeability to calcium ions causes changes in the membrane covering the acrosome, making it possible for the acrosome to release its enzymes; without these changes the sperm cannot enter the ovum to cause fertilization. Calcium also produces a powerful whiplash motion of the flagellum.
Q4. Which sequence correctly describes the acrosome reaction and ovum penetration?
A. Proteolytic enzymes digest the corona radiata first
B. Sperm reaches the ovum → hyaluronidase digests the corona radiata → sperm reaches the zona pellucida and binds receptor proteins → entire acrosome dissolves releasing enzymes → proteolytic enzymes digest the zona pellucida → sperm head penetrates the ovum(correct answer)
C. The sperm tail penetrates first
D. The acrosome dissolves before reaching the ovum
Answer: B.When the sperm reaches the ovum, hyaluronidase digests the corona radiata; the sperm then reaches the zona pellucida and binds specifically with receptor proteins there, the entire acrosome rapidly dissolves releasing its enzymes, and proteolytic enzymes digest the zona pellucida so the sperm head penetrates within minutes.
Q5. Which sequence correctly explains why only one sperm normally enters the oocyte?
A. Sperm are destroyed by antibodies
B. Sperm penetrates the zona pellucida → calcium ions diffuse inward through the oocyte membrane → multiple cortical granules are released by exocytosis into the perivitelline space → substances in the granules permeate the zona pellucida → additional sperm binding is prevented and already-bound sperm fall off(correct answer)
C. The oocyte membrane becomes permeable to all sperm
D. The zona pellucida dissolves completely
Answer: B.Once a sperm penetrates the zona pellucida, calcium ions diffuse inward through the oocyte membrane, causing exocytosis of multiple cortical granules into the perivitelline space; substances in the granules permeate the zona pellucida, preventing binding of additional sperm and causing any already bound to fall off — so almost never does more than one sperm enter the oocyte.
Q6. Why is the block to polyspermy essential?
A. Because extra sperm would consume the egg's nutrients
B. Because the zona pellucida would otherwise dissolve
C. Because entry of more than one sperm would produce an abnormal chromosome number, so cortical granule release prevents additional sperm from entering(correct answer)
D. Because calcium would be lost from the oocyte
Answer: C.If more than one sperm entered, the resulting zygote would have an abnormal chromosome complement; release of cortical granule contents into the perivitelline space and their permeation of the zona pellucida prevent additional sperm binding and cause already-bound sperm to detach, so almost never does more than one sperm enter the oocyte.
Q7. Why is dihydrotestosterone important in some target tissues while testosterone acts directly in others?
A. Because in tissues such as the prostate and fetal genitalia testosterone is converted by 5α-reductase to DHT, which is the more potent androgen for those tissues, whereas other tissues respond to testosterone itself(correct answer)
B. Because DHT is a peptide hormone
C. Because testosterone cannot enter cells
D. Because DHT is formed in the liver only
Answer: A.In certain target tissues (prostate gland, male fetal genitalia) testosterone is converted to dihydrotestosterone, which then forms the active complex with the androgen receptor; other tissues respond to testosterone directly or after conversion, so the local expression of 5α-reductase determines which androgen predominates.
Q8. Which sequence correctly describes the intracellular mechanism of testosterone action?
A. Testosterone binds a membrane receptor → cAMP → protein synthesis
B. Testosterone enters the nucleus unchanged and binds DNA directly without a receptor
C. Testosterone activates JAK2 in the cytoplasm
D. Testosterone diffuses into the cytoplasm → converted to dihydrotestosterone by 5α-reductase → DHT binds the cytoplasmic androgen receptor → the complex moves to the nucleus and binds nuclear receptor sites on DNA → activates transcription factors and mRNA production → protein synthesis in the cell(correct answer)
Answer: D.Testosterone diffuses through the cell membrane into the cytoplasm, where 5α-reductase converts it to dihydrotestosterone; DHT binds the cytoplasmic androgen receptor, and the complex moves into the nucleus, binds nuclear receptor sites on DNA, activates transcription factors and produces mRNA, which directs protein synthesis.
Q9. Why does the intratesticular testosterone concentration matter more than the circulating level for spermatogenesis?
A. Because testosterone cannot leave the testis
B. Because spermatogenesis occurs within the seminiferous tubules, where locally produced testosterone from the adjacent Leydig cells acts in high concentration, so exogenous androgen that suppresses LH can lower intratesticular testosterone despite normal or high blood levels(correct answer)
C. Because Sertoli cells produce testosterone
D. Because blood testosterone is inactive
Answer: B.Spermatogenesis depends on the high local testosterone concentration within the seminiferous tubules, supplied by the neighbouring Leydig cells; when exogenous androgen suppresses LH, Leydig cell production falls and intratesticular testosterone drops even though circulating levels may be high, so spermatogenesis is impaired.
Q10. Why does the pineal gland matter more for seasonally breeding animals than for humans?
A. Because pineal tumours do not affect humans
B. Because humans lack a pineal gland
C. Because human melatonin is inactive
D. Because in seasonal breeders melatonin-mediated suppression of the gonadotropic axis times reproduction to the appropriate season, whereas in humans this photoperiodic control is not clearly operative and the gland's reproductive role is unclear(correct answer)
Answer: D.In seasonally breeding animals the pineal, via darkness-driven melatonin secretion and suppression of gonadotropic hormone secretion, times reproductive cycles to the appropriate season; in humans this photoperiodic regulation of reproduction is not clearly established and the gland's role in human reproduction remains unclear, although pineal tumours are associated with changes in gonadal function.