Male Reproductive System Quiz
101 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which of the following structures is NOT part of the male reproductive system?

  • Testes
  • Seminal vesicles
  • Epididymis
  • Ovaries (correct)

    • Which process involves the transformation of spermatids into mature spermatozoa?

  • Spermatogenesis
  • Spermiogenesis (correct)
  • Oogenesis
  • Gamete fusion

    • What role do the hypothalamus and pituitary gland play in male reproduction?

  • They produce sperm directly.
  • They hold male gametes during fertilization.
  • They store ejaculatory fluid.
  • They regulate the secretion of hormones involved in spermatogenesis. (correct)

    • What is the primary function of the seminal vesicles in the male reproductive system?

    <p>Secretion of ejaculatory fluid (A)</p> Signup and view all the answers

    Which part of the penis is removed during circumcision?

    <p>Glans penis (B)</p> Signup and view all the answers

    What role does nitric oxide (NO) play during the process of erection?

    <p>Relaxes smooth muscle leading to vessel dilation (C)</p> Signup and view all the answers

    What is the primary function of the dartos muscle in the scrotum?

    <p>Contracts to reduce heat loss in cold conditions (C)</p> Signup and view all the answers

    What do Leydig cells in the interstitial compartment of the testis primarily produce?

    <p>Testosterone (C)</p> Signup and view all the answers

    What is the significance of the blood-testis barrier formed by Sertoli cells?

    <p>Maintains optimal conditions for germ cell development (B)</p> Signup and view all the answers

    How many spermatozoa does each primary spermatocyte yield upon division?

    <p>4 (B)</p> Signup and view all the answers

    What happens to the small arteries supplying the penis when it is flaccid?

    <p>They remain constricted to limit blood supply (C)</p> Signup and view all the answers

    Which part of the spermatic cord is responsible for maintaining testicular temperature?

    <p>Cremaster muscle (B)</p> Signup and view all the answers

    What stage of sperm development is indicated when sperm are described as elongated with tails extending into the tubular lumen?

    <p>Stage 7 (C)</p> Signup and view all the answers

    What process produces sperm in the seminiferous tubules?

    <p>Spermatogenesis (A)</p> Signup and view all the answers

    How many new sperm can the testes produce each day?

    <p>400 million (D)</p> Signup and view all the answers

    Which cell type is responsible for nourishing developing germ cells during spermatogenesis?

    <p>Sertoli cells (B)</p> Signup and view all the answers

    What is the primary function of the acrosome in sperm?

    <p>Penetration of the egg (B)</p> Signup and view all the answers

    During spermatogenesis, when do primary spermatocytes undergo their first meiotic division?

    <p>In the adluminal compartment (C)</p> Signup and view all the answers

    What transformation occurs during spermiogenesis?

    <p>Elongation of spermatids (C)</p> Signup and view all the answers

    What characterizes the spermatic cycle in seminiferous tubules?

    <p>Sequential development occurs along different lengths (D)</p> Signup and view all the answers

    Where does the final functional maturation of sperm occur?

    <p>In the female reproductive tract (D)</p> Signup and view all the answers

    What is the role of the epididymis in sperm transport?

    <p>Monitoring and adjusting fluid composition (D)</p> Signup and view all the answers

    What happens to the cytoplasm during spermiogenesis?

    <p>It is sloughed away (B)</p> Signup and view all the answers

    What type of chromosomes do secondary spermatocytes have after division?

    <p>23 1-chromatid chromosomes (B)</p> Signup and view all the answers

    What is the primary regional characteristic of the sperm midpiece?

    <p>Contains mitochondria (B)</p> Signup and view all the answers

    What role do the seminal vesicles play in the male reproductive system?

    <p>They release a viscous fluid that enhances sperm motility. (A)</p> Signup and view all the answers

    What happens to sperm stored for an extended period in the epididymis?

    <p>They are phagocytosed by epithelial cells. (B)</p> Signup and view all the answers

    What hormone acts locally in the testes to stimulate spermatogenesis?

    <p>Testosterone (D)</p> Signup and view all the answers

    What impact does elevated testosterone have on the secretion of luteinizing hormone (LH)?

    <p>It suppresses LH secretion. (B)</p> Signup and view all the answers

    During spermatogenesis, which hormone does inhibin specifically inhibit the secretion of?

    <p>Follicle-stimulating hormone (FSH) (C)</p> Signup and view all the answers

    What is the primary function of the prostate in male reproductive physiology?

    <p>Activating sperm and producing seminal fluid (B)</p> Signup and view all the answers

    What is the physiological consequence of the binding of follicle-stimulating hormone (FSH) to Sertoli cells?

    <p>It stimulates spermatogenesis indirectly through paracrine factors. (B)</p> Signup and view all the answers

    What substance is released by bulbourethral glands, and what is its primary function?

    <p>Thick mucus for lubrication and neutralization of acidic urine (A)</p> Signup and view all the answers

    Which of the following enzymes converts testosterone into dihydrotestosterone (DHT) in the prostate?

    <p>5α-reductase (C)</p> Signup and view all the answers

    How does testosterone influence secondary sexual characteristics?

    <p>It opposes the action of estrogen. (B)</p> Signup and view all the answers

    What is the predominant hormone secreted by the corpus luteum after ovulation if fertilization occurs?

    <p>Progesterone (A)</p> Signup and view all the answers

    During which phase of folliculogenesis does the zona pellucida begin to form around the oocyte?

    <p>Primary follicle phase (B)</p> Signup and view all the answers

    What happens to non-dominant follicles during the menstrual cycle?

    <p>They undergo atresia (C)</p> Signup and view all the answers

    What initiates ovulation in the menstrual cycle?

    <p>LH surge (A)</p> Signup and view all the answers

    What is the process of degeneration of the corpus luteum called?

    <p>Luteolysis (B)</p> Signup and view all the answers

    Which cell type in the ovarian follicle converts androgens to estrogen?

    <p>Granulosa cells (D)</p> Signup and view all the answers

    What role does folicular fluid play after ovulation?

    <p>It carries the oocyte to the fallopian tube (A)</p> Signup and view all the answers

    What is the main function of granulosa cells during folliculogenesis?

    <p>To convert androgens into estrogen (D)</p> Signup and view all the answers

    What marks the transition from a secondary follicle to an early antral follicle?

    <p>Development of the antrum (B)</p> Signup and view all the answers

    What triggers the pulsatile release of GnRH from the hypothalamus?

    <p>Increased estrogen levels (B)</p> Signup and view all the answers

    What primarily causes the hormonal changes that precede menstruation?

    <p>Degeneration of the corpus luteum (B)</p> Signup and view all the answers

    What is the primary function of inhibin in the reproductive system?

    <p>To inhibit FSH production (B)</p> Signup and view all the answers

    Why do only 400 oocytes get released during a woman’s lifetime?

    <p>Oocytes undergo atresia (C)</p> Signup and view all the answers

    Which layer of the uterus undergoes changes to allow for implantation of a fertilized egg?

    <p>Endometrium (B)</p> Signup and view all the answers

    What is the estimated number of oocytes remaining at menopause?

    <p>Approximately 1,000 (B)</p> Signup and view all the answers

    During which phase of the ovarian cycle does ovulation occur?

    <p>Follicular phase (A)</p> Signup and view all the answers

    Which structure in the female reproductive system is responsible for capturing the oocyte after ovulation?

    <p>Fimbriae (B)</p> Signup and view all the answers

    What hormone is primarily produced by the ovaries after ovulation?

    <p>Progesterone (B)</p> Signup and view all the answers

    What is a significant difference between male and female gamete production?

    <p>Females undergo a cyclic production of gametes (C)</p> Signup and view all the answers

    What is the main role of the myometrium?

    <p>To contract during childbirth (D)</p> Signup and view all the answers

    Which part of the female reproductive system serves as the site for fertilization?

    <p>Ampulla of fallopian tube (C)</p> Signup and view all the answers

    What role does cervical mucus play during the menstrual cycle?

    <p>It blocks sperm entry except at mid-cycle (D)</p> Signup and view all the answers

    What hormonal axis regulates the ovarian and uterine cycles?

    <p>Hypothalamic-pituitary-gonadal axis (A)</p> Signup and view all the answers

    What condition may result from the stretching of pelvic floor muscles during delivery?

    <p>Uterine prolapse (B)</p> Signup and view all the answers

    Which part of the ovary is where follicles mature?

    <p>Cortex (C)</p> Signup and view all the answers

    How often does the menstrual cycle typically occur?

    <p>Every 28 days (D)</p> Signup and view all the answers

    What can prevent bacterial spread into the uterus from the vagina?

    <p>Cervical mucus (B)</p> Signup and view all the answers

    What are the end products of the first meiotic division of oocytes?

    <p>One secondary oocyte and one polar body (A)</p> Signup and view all the answers

    What is the average viability period of an ovulated oocyte?

    <p>1-2 days (A)</p> Signup and view all the answers

    What is the role of fimbriae during ovulation?

    <p>To sweep the oocyte into the fallopian tube (B)</p> Signup and view all the answers

    What must happen to sperm before they can successfully fertilize an ovulated oocyte?

    <p>They must undergo capacitation (B)</p> Signup and view all the answers

    What triggers the acrosomal reaction in sperm during fertilization?

    <p>Binding to the zona pellucida via ZP3 glycoproteins (D)</p> Signup and view all the answers

    What is the significance of second meiotic division in oogenesis?

    <p>It occurs only if fertilization happens (C)</p> Signup and view all the answers

    Which of the following describes a major issue affecting sperm transport to the fallopian tube?

    <p>Length and energy requirements of the trip (A)</p> Signup and view all the answers

    What are the functional implications of follicular cells during oocyte development?

    <p>They provide signals necessary for meiosis and oocyte growth (C)</p> Signup and view all the answers

    What typically happens to the first polar body during oocyte development?

    <p>It degenerates (C)</p> Signup and view all the answers

    In oocyte development, how many of the initial million oocytes typically ovulate?

    <p>Approximately 400 (A)</p> Signup and view all the answers

    What hormone is primarily produced by granulosa cells of small follicles?

    <p>Inhibin B (C)</p> Signup and view all the answers

    Which hormone is thought to have a significant inverse correlation with FSH during the follicular phase?

    <p>Inhibin B (A)</p> Signup and view all the answers

    During which phase of the uterine cycle does the functional layer begin to shed?

    <p>Menstrual phase (C)</p> Signup and view all the answers

    What initiates the LH surge that drives ovulation?

    <p>High concentrations of estrogen (B)</p> Signup and view all the answers

    How does the corpus luteum mainly contribute to the menstrual cycle when there is no pregnancy?

    <p>By degrading after two weeks and lowering progesterone levels (A)</p> Signup and view all the answers

    What effect does rising estrogen levels have during the menstrual cycle?

    <p>Exerts negative feedback on hypothalamus and pituitary (B)</p> Signup and view all the answers

    What happens to the endometrial layer during days 6-14 of the cycle?

    <p>It undergoes proliferation and thickens (A)</p> Signup and view all the answers

    What triggers the primary oocyte to complete its first meiotic division?

    <p>LH surge (C)</p> Signup and view all the answers

    Which layer of the endometrium does not respond to ovarian hormones?

    <p>Basal layer (A)</p> Signup and view all the answers

    What physiological changes occur to the endometrium in the secretory phase?

    <p>It thickens and secretes nutrients (D)</p> Signup and view all the answers

    How does the corpus luteum's secretion of progesterone affect the uterine cycle?

    <p>It prepares the endometrium for embryo implantation (A)</p> Signup and view all the answers

    What role do the theca cells play in the early stages of ovarian follicle development?

    <p>They produce androgens (D)</p> Signup and view all the answers

    What happens to the developing follicles when only one becomes dominant?

    <p>Only the dominant follicle survives the FSH dip (A)</p> Signup and view all the answers

    What happens to serum levels of FSH and LH in response to high levels of progesterone?

    <p>They decrease (A)</p> Signup and view all the answers

    What effect does the degeneration of the corpus luteum have on the ovarian cycle?

    <p>It begins the menstruation phase (A)</p> Signup and view all the answers

    What function does the zona pellucida serve in fertilization?

    <p>It prevents polyspermy and mediates species-specific gamete interaction. (C)</p> Signup and view all the answers

    Which proteins are involved in the fusion of sperm and eggs during fertilization?

    <p>Izumo and CD9 (D)</p> Signup and view all the answers

    What triggers the acrosome reaction in sperm?

    <p>Binding to ZP3 (B)</p> Signup and view all the answers

    How does the cortical reaction prevent polyspermy immediately after fertilization?

    <p>It hardens the zona pellucida and depolarizes the oocyte membrane. (A)</p> Signup and view all the answers

    What role does calcium play during the fertilization process?

    <p>It triggers the acrosome reaction and aids in fusion of membranes. (D)</p> Signup and view all the answers

    Which protein is crucial for sperm binding to the zona pellucida?

    <p>ZP3 (B)</p> Signup and view all the answers

    What prevents further sperm from entering the egg after the first successful fertilization?

    <p>Calcium surges that change the oocyte's membrane properties. (B)</p> Signup and view all the answers

    What happens to sperm that successfully penetrate the zona pellucida?

    <p>They undergo acrosomal reaction and fuse with the egg. (D)</p> Signup and view all the answers

    What occurs during the transition from egg to embryo following fertilization?

    <p>Completion of the second meiotic division of the egg. (B)</p> Signup and view all the answers

    What is the role of actin filaments in sperm during fertilization?

    <p>They form the acrosomal process binding to the oocyte. (B)</p> Signup and view all the answers

    How is the zygote formed during fertilization?

    <p>By the fusion of sperm and egg nuclei. (D)</p> Signup and view all the answers

    What is the fate of polar bodies formed during oocyte maturation?

    <p>They undergo apoptosis. (A)</p> Signup and view all the answers

    What is a consequence of ectopic pregnancies?

    <p>They require medical intervention due to risks. (B)</p> Signup and view all the answers

    Why is it essential for the zona pellucida to be intact during fertilization?

    <p>It mediates the correct sperm-egg binding. (A)</p> Signup and view all the answers

    Study Notes

    Male Reproductive System

    • The male reproductive system consists of four major components: testes, ducts, exocrine glands, and the penis.
    • The testes are responsible for producing sperm and androgens.
    • The ducts collect, store, and transport sperm.
    • The exocrine glands secrete fluids that make up semen.
    • The penis delivers semen to the female reproductive tract.

    The Penis

    • The penis is composed of three main parts: the root, shaft, and glans penis.
    • The glans penis is the enlarged tip covered by the foreskin (prepuce).
    • It contains three cylindrical columns of erectile tissue: two corpora cavernosa and one corpus spongiosum.
    • The urethra runs through the middle of the corpus spongiosum.
    • The penis is highly vascularized and innervated.

    Erection

    • During sexual stimulation, parasympathetic nerves release nitric oxide (NO) which causes relaxation of smooth muscles in the penile arteries.
    • This leads to vasodilation, increased blood flow, and engorgement of the vascular channels, resulting in an erection.

    The Scrotum

    • The scrotum is a sac of skin and superficial fascia that houses the testes.
    • It maintains the testes at a lower temperature (around 34 degrees Celsius) which is essential for sperm production.
    • The dartos and cremaster muscles regulate temperature.
    • The dartos muscle contracts in cold temperatures, wrinkling the scrotal skin and decreasing heat loss.
    • The cremaster muscle contracts in cold temperatures, elevating the scrotum and moving the testes closer to the body.

    The Testes

    • Each testis is divided into lobules by fibrous septa that project inwards from the tunica albuginea.
    • Each lobule contains 1-4 seminiferous tubules, where spermatogenesis (sperm production) takes place.
    • Seminiferous tubules converge to form the rete testis, which leads to the efferent ductules and then the epididymis.
    • The epididymis is a long, coiled tube that stores and matures sperm.
    • The vas deferens is a large, thick-walled tube that carries sperm from the epididymis to the urethra.

    Spermatogenesis

    • Spermatogenesis is the process of sperm production.
    • It occurs in the seminiferous tubules and begins at puberty.
    • It is a continuous process throughout adult life, with each mature sperm taking approximately 10 weeks to form.
    • Each seminiferous tubule has a basement membrane, a fluid-filled lumen, and a tubular wall made of germ cells and supporting cells (Sertoli cells).
    • Sertoli cells form tight junctions that create a blood-testis barrier.
    • The barrier prevents chemicals from moving from the blood into the seminiferous tubule lumen and helps maintain the correct conditions for germ cell development.

    Spermatogenesis Pathway

    • Spermatogenesis begins with stem cells in the testes, located in the basal compartment.
    • Type A spermatogonia divide through mitosis to produce Type B spermatogonia.
    • Type B spermatogonia differentiate and divide to form two primary spermatocytes.
    • Primary spermatocytes move into the adluminal compartment and undergo meiotic division.
    • Each primary spermatocyte forms two secondary spermatocytes.
    • Each secondary spermatocyte then forms two spermatids.
    • Spermatids differentiate into spermatozoa during spermiogenesis.

    Spermiogenesis

    • Spermiogenesis is the process of transforming spermatids into functional sperm, taking approximately 24 days.
    • It involves extensive cellular remodeling and no further cell division.
    • During spermiogenesis, the Golgi apparatus packages hydrolytic enzymes into the acrosomal vesicle, the acrosome forms at the anterior end of the nucleus, microtubules elongate to form the flagellum, mitochondria multiply and move to the proximal portion of the flagellum, and excess cytoplasm is sloughed away.
    • Immature sperm are released from Sertoli cells in the process of spermiation.
    • Sperm mature and become motile in the epididymis.

    Sperm Structure

    • Sperm have a head, midpiece, and tail.
    • The head contains the nucleus and the acrosome which contains hydrolytic enzymes that help the sperm penetrate an egg.
    • The midpiece contains mitochondria that provide energy for the flagellum.
    • The tail propels the sperm through the female reproductive tract.

    The Spermatogenic Cycle

    • Spermatogenesis is cyclic, occurring sequentially along the length of the seminiferous tubules, resulting in a continuous release of spermatozoa.
    • Different stages of germ cell development occur at different levels of the tubule.

    Sperm Transport

    • Sperm travel through the epididymis, where they mature and gain motility.
    • The vas deferens carries sperm from the epididymis to the urethra.
    • During ejaculation, sperm and seminal fluid mix in the ejaculatory duct and enter the prostatic urethra.

    Seminal Vesicles

    • The seminal vesicles attach to the vas deferens to form the ejaculatory duct.
    • They secrete a viscous fluid that makes up 70% of semen volume.
    • This fluid contains substances that enhance sperm motility and fertilizing ability.
    • These substances include fructose (energy source), prostaglandins (smooth muscle contractions), and vesciculase (coagulating enzyme).

    Prostate

    • The prostate is a donut-shaped gland that produces approximately 1/3 of semen volume.
    • It secretes a milky, acidic fluid that contains citrate (nutrient source), prostate-specific antigen (PSA), and enzymes like hyaluronidase.

    Bulbourethral Glands

    • The bulbourethral glands line the urethra and secrete thick mucus to lubricate the glans penis and neutralize traces of acidic urine.

    Hormonal Control of Male Reproductive Function

    • Spermatogenesis is controlled by the hypothalamic-pituitary-gonadal (HPG) axis.
    • The hypothalamus secretes gonadotropin-releasing hormone (GnRH) which stimulates the anterior pituitary gland to release follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
    • LH binds to Leydig cells in the testes and stimulates testosterone production.
    • Testosterone feeds back to the hypothalamus and pituitary gland, inhibiting GnRH and LH secretion.
    • FSH binds to Sertoli cells and stimulates spermatogenesis.

    Testosterone Function

    • Testosterone stimulates the differentiation and function of male accessory organs, induces male secondary sex characteristics, opposes estrogen action, stimulates protein anabolism and bone growth, enhances sex drive, stimulates erythropoietin (EPO) secretion, and increases basal metabolic rate.

    Regulation of FSH Levels

    • Sertoli cells produce inhibin in response to FSH action.
    • Inhibin inhibits FSH secretion from the pituitary gland.

    Inhibin

    • Inhibin is produced by Sertoli/granulosa cells in response to follicle stimulating hormone (FSH), released and acts on gonadotroph cells in the pituitary, blocking activin signalling and hence FSH production.

    Female Reproduction

    • The female reproductive system produces gametes and nurtures a developing fetus for 9 months before childbirth.
    • The ovaries are the primary reproductive organs, producing female gametes (ova/eggs) and synthesizing/secreting estrogen and progesterone.
    • The production of eggs and their release from the ovaries is cyclical unlike continuous sperm production in men.
    • The structure and function of elements of the female reproductive system are synchronized with the ovarian cycle (menstrual cycle).
    • The hypothalamic-pituitary-gonadal axis regulates the cyclical changes in the ovaries and uterus.
    • The ovary changes prepare the uterus to receive the developing embryo.

    Anatomy

    • The ovaries and the duct system are located in the pelvic cavity.
    • Accessory ducts from adjacent to the ovary to the exterior of the body include the fallopian tubes, uterus and vagina.
    • The vagina provides a passageway for menstrual fluid, the penis during intercourse, and the expulsion of the fetus during childbirth.
    • At the upper end of the vagina, it connects to the uterus (latin for womb).

    Uterus

    • The uterus is a hollow, thick-walled muscular organ that receives, retains and nourishes the fertilized ovum.
    • The uterus has three layers:
      • Perimetrium (outermost layer).
      • Myometrium – bulky layer of smooth muscle.
      • Endometrium – mucosal inner layer.
    • The endometrium has two strata:
      • Stratum functionalis – undergoes cyclical changes depending on ovarian hormones, allows for implantation of a fertilized egg and is shed during menstruation.
      • Stratum basalis – unresponsive to ovarian hormones, generates a new functional layer after menstruation ends.

    Fallopian Tubes

    • Also known as oviducts or uterine tubes.
    • Each fallopian tube extends from the fundus of the uterus to the ovaries.
    • Finger-like projections (fimbriae) sweep over the ovary to capture the oocyte.
    • The oocyte travels through the infundibulum and then the ampulla, where fertilization usually takes place.
    • The egg is carried to the uterus through a mixture of muscular peristalsis and beating of mucosal cell cilia.

    Ovaries

    • Produce female gametes (oocytes/eggs) and female sex hormones: estrogen and progesterone.

    Ovarian Cycle

    • A series of changes in the ovary during which a follicle matures, an ovum is shed and a corpus luteum develops.
    • Consists of two phases:
      • The follicular phase (days 1-14) during which follicles grow, ending in ovulation.
      • The luteal phase (days 15-28) during which the corpus luteum is active.

    Oocyte Development

    • At birth, ovaries contain 1-2 million eggs (female lifetime supply).
    • Many oocytes degenerate during development leaving 300k and less than 1000 at menopause.
    • Only 400 oocytes are released in a woman's lifetime.
    • Oocytes remain in structures known as follicles throughout their life in the ovary.

    Follicle Growth

    • Primordial follicles – one oocyte surrounded by a single layer of granulosa cells.
    • Primary follicles – cells around the oocyte become cuboidal, the zona pellucida forms and the oocyte enlarges.
    • Secondary follicles – granulosa cells proliferate and form a stratified epithelium around the oocyte.
    • Early antral follicle – a fluid-filled space forms between the granulosa cells.
    • Mature follicle – antrum expands with follicular fluid and a mound of the oocyte with its surrounding granulosa cells forms.

    Ovulation

    • The mature follicle bulges from the ovarian surface.
    • Ovulation occurs when the follicle walls rupture and the secondary oocyte is released into the peritoneal cavity.
    • The follicular fluid provides a medium to carry the oocyte and protects and nourishes it.

    Corpus Luteum

    • The ruptured follicle collapses around the antrum and develops.
    • Granulosa cells enlarge and combine with thecal cells to form the corpus luteum (yellow body).
    • The corpus luteum secretes progesterone and some estrogen (for 3 months if pregnancy occurs).
    • If the egg is not fertilized, the corpus luteum degenerates 10 days after ovulation and its hormonal output ends.
    • The corpus luteum degeneration results in the formation of a scar, the corpus albicans (white body).

    Hormonal Control of Ovarian Function

    • Hormonal regulation is similar to that of the testes.
    • GnRH secretion from hypothalamic neurons into the hypothalamo-hypophyseal portal vessels regulates LH and FSH, which control female reproductive cycles.
    • The frequency and amplitude of GnRH pulses changes across the cycle in women.

    Hormonal Levels

    • FSH increases in the early follicular phase, decreasing throughout the cycle except for a small mid-cycle peak.
    • LH remains constant throughout most of the follicular phase but increases dramatically mid-cycle (LH surge).
    • Estrogen levels are low and stable for the first week but increase rapidly in the second week as the dominant follicle grows.
    • Progesterone is not secreted by the ovaries until just before ovulation.

    Inhibin

    • Inhibin A and B are produced in a discordant way.

    Hormonal Control of the Ovarian Cycle

    • Inhibin B is primarily produced by granulosa cells of small follicles, while inhibin A is predominantly produced by large follicles and the corpus luteum.
    • Inhibin B levels are inversely correlated with FSH levels in the follicular phase.
    • FSH and LH are released from the anterior pituitary gland, stimulated by GnRH from the hypothalamus.
    • FSH promotes the growth of preantral and early antral follicles, while LH stimulates theca cells to produce androgens.
    • Granulosa cells convert androgens into estrogen using aromatase.
    • Rising estrogen levels in the follicular phase exert negative feedback on the hypothalamus and anterior pituitary, suppressing FSH and LH release.
    • Inhibin also exerts negative feedback on FSH synthesis.
    • Only one dominant follicle typically survives the FSH dip, becoming more sensitive to FSH and producing large amounts of estrogen.
    • High estrogen levels from the dominant follicle briefly exert a positive feedback effect, inducing the LH surge.
    • The LH surge triggers ovulation and the transformation of the ruptured follicle into the corpus luteum.

    Corpus Luteum and Hormonal Changes

    • The corpus luteum produces progesterone and some estrogen.
    • Progesterone helps maintain the endometrium and is essential for pregnancy.
    • Progesterone exerts strong negative feedback, suppressing LH and FSH synthesis.
    • Without fertilization, the corpus luteum regresses within two weeks, causing a decrease in progesterone and estrogen levels.
    • This decline in ovarian hormones stimulates FSH, LH, and potentially GnRH release, initiating a new cycle.

    Uterine Cycle

    • The endometrium undergoes cyclic changes in response to ovarian hormones.
    • The endometrium consists of a functional layer (shed during menstruation) and a basal layer.
    • During menses, the functional layer is shed due to vasoconstriction of spiral arteries and uterine contractions, mediated by prostaglandins.
    • The proliferative phase rebuilds the endometrium under the influence of estrogen, thickening the functional layer and developing spiral arteries.
    • Estrogen promotes progesterone receptor expression, preparing the endometrium for the secretory phase.
    • The secretory phase is characterized by the dominant influence of progesterone, leading to glandular development, coiling of spiral arteries, and a thick cervical plug.
    • Progesterone inhibits uterine contractions.
    • Without fertilization, progesterone levels fall, triggering menstruation and a new uterine cycle.

    Fertilization

    • Oogenesis, the development of oocytes, begins with all oogonia developing into primary oocytes.
    • Only oocytes destined for ovulation complete the first meiotic division, forming a secondary oocyte and a first polar body.
    • The secondary oocyte undergoes a second meiotic division, but only completes it if fertilization occurs.
    • In vitro oocyte production from mouse pluripotent stem cells has successfully produced viable offspring.
    • Sperm transport and capacitation are essential for fertilization.
    • Capacitation involves changes in the sperm membrane that make it capable of fusing with the oocyte.
    • Sperm must penetrate the cumulus granulosa cells and zona pellucida to reach the oocyte.
    • The acrosomal reaction releases enzymes that digest the zona pellucida.
    • The zona pellucida mediates species-specific fertilization and prevents polyspermy.
    • The cortical reaction, triggered by calcium surges, prevents further sperm entry by hardening the zona pellucida.
    • After fertilization, the egg completes its second meiotic division, forming a mature ovum and a second polar body.
    • The sperm and egg nuclei fuse, forming the diploid zygote.
    • The zygote undergoes its first mitotic division, marking the start of embryogenesis.
    • Ectopic pregnancies occur when a fertilized egg implants outside the uterus, typically in the fallopian tube.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Description

    Test your knowledge of the male reproductive system with this quiz. Explore key structures, processes, and functions integral to male reproduction. Answer questions regarding hormones, sperm development, and anatomical features.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser