Reproductive System Flashcards

The Male Reproductive System

Overview of Male Anatomy

  • Male anatomy consists of:
    • Essential organ: Testes.
    • Ducts: Seminiferous tubules, Epididymis, Vas (Ductus) Deferens, Ejaculatory Duct, Urethra.
    • Glands: Seminal Vesicles, Prostate Gland, Bulbourethral (Cowper’s) Gland.
    • Supporting Structures: Penis, Scrotum, Spermatic cords.

Functions of the Male Reproductive System

  • Sperm production.
  • Maturation of sperm.
  • Androgen production.
  • Transfer of sperm to the female reproductive tract.

The Scrotum

  • Testes are housed in the scrotum, a sac external to the body.
  • The external location maintains a temperature of 2−42-4 degrees Celsius lower than body temperature, which is necessary for sperm development.
  • The cremaster muscle, a muscular sheath derived from the internal oblique, covers the testes and can elevate or descend them in response to temperature changes.

Spermatic Cords

  • Connect the scrotum to the body, containing vessels and nerves.
  • Components include the testicular artery, testicular vein, vas deferens, lymphatic vessels, and nerves.
  • Covered by the cremaster muscle and skin, leading to the pelvic cavity.

The Testes

  • Male gonads that produce sperm and testosterone throughout a male's life.
  • Approximately 2 inches in length and ovoid in shape.
  • Covered by two connective tissue layers: tunica vaginalis (superficial) and tunica albuginea (deep).
  • The tunica albuginea invaginates to form 300-400 lobules, which contain seminiferous tubules where sperm develop.

Seminiferous Tubules

  • Tightly coiled within the lobules of the testes.
  • Developing sperm cells reside in the walls of the tubules, moving closer to the lumen as they mature.
  • The location where meiosis takes place in males.
  • Sertoli cells create a blood-testis barrier, preventing harmful substances from reaching sperm cells.

Spermatogenesis

  • Begins at puberty and continues throughout life.
  • The process from spermatogonia to spermatozoa takes approximately 64 days.
  • A new process starts every 16 days, but start days are staggered.
  • Mitosis produces one cell that continues through meiosis (primary spermatocyte) and one that acts as a feeder cell.
  • Meiosis in the primary spermatocyte creates two secondary spermatocytes, each of which divides to form a spermatid.
  • The spermatid matures into a full spermatozoa (sperm).

Sperm

  • 100-300 million sperm are produced per day.
  • Smaller than most body cells.
  • The head contains a nucleus and is covered by an acrosome, containing lysozyme to help penetrate the egg.
  • The midpiece contains mitochondria for energy production.
  • The tail, made of cytoskeleton, facilitates movement.

Sperm Transport

  • Sperm moves through a duct system from the seminiferous tubules to the urethra to exit the body.
  • Pathway: Seminiferous tubules → Epididymis → Vas Deferens → Ejaculatory Duct → Urethra (Membranous) → Penile Urethra.
  • Mnemonic Device: SEVEn UP

The Epididymis

  • A C-shaped, tightly coiled tube on the posterior edges of the testes.
  • Sperm take about 12 days to travel through the epididymis.
  • Initially moved by testicular fluid, sperm develop the ability to move on their own.
  • Sperm are stored in the tail of the epididymis until ejaculation.

The Vas (Ductus) Deferens

  • A muscular tube leading from the epididymis to the prostate gland.
  • Has a three-layer structure.
  • Accessible through the scrotum, making it a site for vasectomies (male birth control).
  • Ends posterior to the bladder, dilates, enters the prostate, and meets the urethra.
  • Vasectomy involves cutting the vas deferens to disrupt the pathway of sperm.

The Seminal Vesicles

  • Paired glands bilateral to the prostate gland.
  • Secrete a fluid that makes up 60% of semen volume.
  • The fluid joins sperm from the vas deferens.
  • Seminal fluid is mostly fructose, providing a monosaccharide for ATP production for sperm movement.

Ejaculatory Duct

  • Formed from the widening of the vas deferens and the seminal vesicle duct.
  • Carries the combination of sperm and seminal fluid to the prostate gland.

Prostate Gland

  • Anterior to the rectum and inferior to the bladder.
  • Contributes about 30% of semen volume which is alkaline to raise the acidic pH found in the vaginal tract, and also helps to coagulate semen, and then de-coagulate it.
  • Enlarges during puberty and around age 25.
  • Benign hyperplastic prostate can cause urination issues.

Bulbourethral Glands

  • Paired glands (Cowper’s glands) that contribute about 5% of semen.
  • Secrete a thick, salty fluid that lubricates and cleanses the male urethra after arousal and before ejaculation.

The Penis

  • The male organ used to transfer sperm into the female.
  • Flaccid unless sexually aroused, when it engorges with blood and becomes turgid.
  • The shaft surrounds the urethra and contains three bodies of erectile tissue.
  • Nitric Oxide increases blood flow into the erectile bodies, disallowing venous drainage.
  • Erection is due to parasympathetic stimulation; ejaculation is due to sympathetic stimulation.

Testosterone

  • Produced by Leydig (interstitial) cells outside of the seminiferous tubules.
  • In males during the 7th week through the second trimester: development of male genitalia.

Testosterone Functions

  • In the testes, promotes spermatogenesis; low levels can lead to infertility.
  • In the blood, promotes muscle development, bone growth, and secondary sex characteristics (thyroid cartilage enlargement, voice deepening, body hair growth).
  • Maintains the male sex drive.
  • Leydig cell function declines after age 40−5040-50, reducing testosterone secretion.

Testosterone Production

  • Operates on a negative feedback loop.
  • At puberty, the hypothalamus secretes GnRH, directing the anterior pituitary to release LH and FSH.
  • LH binds to Leydig cell receptors, prompting testosterone production.
  • Rising testosterone levels reduce production; lowered levels increase production.

Review of Sperm/Semen Course and Content

  • Course of sperm:
    • Produced in the seminiferous tubules.
    • Matures in the epididymis.
    • Travels through the Vas Deferens.
    • Meets contributions from seminal vesicles in the ejaculatory duct.
    • Flows through the prostate urethra (membranous).
    • Meets contributions from the bulbourethral gland.
    • Flows through the penile urethra.
  • Semen content:
    • 5% Sperm
    • 5% Pre-Ejaculate from the Bulbourethral Glands
    • 30% Prostate fluid
    • 60% Seminal Vesicle fluid

Male Infertility

  • Primary pathologies of the male reproductive system can lead to infertility.
  • Male accessory gland infection.
  • Immature / Abnormal Spermatoza.
  • Environmental lifestyle factors like drugs, smoking, pollution, and radiation.
  • Systemic pathologies like Diabetes or Cancer.
  • Prolonged stasis of spermatozoa in the epididymis or during transit can cause dysfunction.
  • Oxidative Stress creates free radicals: H<em>2O</em>2H<em>2O</em>2 and OHOH.
  • Systemic infection can cause Oxidative Stress.
  • Infertility can be evaluated by looking for oxidative stress.
  • Treatment of infertility can include, treating underlying pathology, antioxidant supplementation, and avoiding factors promoting ROS gene value

The Female Reproductive System

Overview of Female Anatomy

  • Female anatomy involves an essential organ, a series of ducts, and a number of glands.
    • Essential Organ: The ovaries
    • Ducts: The vagina, the uterus, and the fallopian (uterine) tubes
    • Glands: The mammary glands, the Bartholin’s glands
    • Supporting Structures: Vulva consisting of labia, the mons pubis, and the clitoris

Functions of the Female Reproductive System

  • Oocyte production
  • Oocyte expulsion
  • Androgen production
  • Receive sperm from the male tract
  • Provide a place for fertilization
  • Provide a place for embryo and fetus development
  • Nourish the baby upon birth

The Vulva

  • The external female genitalia are referred to as the vulva
  • They consist of:
    • Mons pubis – fat pad covered with hair over the pubic bone
    • Labia majora – hair covered skin posterior and inferior to the mons pubis
    • Labia minora – thinner, pigmented skin folds internal to the majora
    • Clitoris – nerve body originating from the same cells as the glans penis
    • Hymen – thin partial membrane covering the vaginal entrance
    • Bartholin’s glands – also called Greater Vestibular Glands, just deep to the labia minora

The Vagina

  • The vagina is a smooth muscle canal and the beginning of the female reproductive tract
  • It is the entrance for the penis and the exit for menstruation and childbirth
  • It is lined with mucosa that creates folds called rugae
  • The Bartholin’s glands and a pair of lesser vestibular glands lubricate the vagina to keep it moist
  • Bacteria in the vagina keep its pH acidic

The Ovaries

  • The ovaries are the female gonads and are the size and shape of an almond
  • Ligaments connect them to the uterus and the abdominal wall; those ligaments also help direct the ovarian arteries and veins, and lymphatic vessels to and from the ovary
  • Ovaries have an outer tunica albuginea connective tissue covering a cortex layer (blue)
  • Oocytes develop in this layer surrounded by a group of supporting cells called a follicle (red)

The Ovarian Cycle - Oogenesis

  • Oogonia are formed in development and divide by mitosis to form primary oocytes before birth (unlike in the male)
  • Primary oocytes will undergo meiosis to form gametes but are halted in Meiosis I until puberty when meiosis resumes.
  • Each time a woman is nearing the middle of the ovarian cycle, meiosis will progress until Metaphase II and then halt, waiting to be fertilized
  • Primary oocytes undergo atresia (wasting) throughout a woman’s reproductive life from 1-2 million at birth to 400,000 at puberty to nearly zero at the end of menopause

The Ovarian Cycle – Mature Ovum Creation

  • About every 28 days, a surge of Luteinizing hormone prompts the development of a primary oocyte halted in Prophase I to continue meiosis
  • The cell divides into two cells, one of which receives more cytoplasm than the other and becomes a secondary oocyte; the other cell is useless
  • The secondary oocyte halts in metaphase II until/if fertilization at which point it makes its final division, again creating one mature cell and one useless cell

The Union of Ovum and Sperm

  • Upon sperm penetration of the egg, meiosis II resumes and finishes, producing the mature ovum and the useless polar body
  • The larger amount of cytoplasm in the mature ovum nourishes the fertilized egg (now a zygote)
  • The male’s sperm carries very little cytoplasm, needing room for the nucleus and mitochondria; therefore, male DNA is all that’s really contributed to the zygote. The organelles are nearly all maternal, including the maternally inherited mitochondrial DNA

The Ovarian Cycle - Folliculogenesis

  • Folliculogenesis begins with primordial follicles in the female infant
  • These have a single layer of granulosa cells
  • After puberty, each month a group of follicles is stimulated to develop into:
    • Primary follicles
    • Secondary follicles
    • Tertiary follicles

Hormonal Regulation of Folliculogenesis

  • The 28 day on average cycle to develop from a primordial to a tertiary follicle ready to rupture is governed by the same hormones that are at work in the male
  • GnRH from the hypothalamus prompts the Anterior Pituitary to release FSH and LH
  • FSH stimulates the follicles to grow while LH stimulates the theca cells of the follicle to produce estrogen
  • The more thecal cells a follicle has, the more estrogen they produce which leads to higher circulating levels of estrogen that cause a negative feedback response by the hypothalamus and anterior pituitary

Hormonal Regulation of Ovulation

  • With one dominant follicle remaining, its estrogen secretion surges; production is more than even before the other follicles underwent atresia
  • This time the feedback on the hypothalamus and anterior pituitary is not negative – but positive. FSH and LH secretion increases
  • The LH surge results in ovulation (expulsion of the mature oocyte/ovum)
  • In a typical 28 day cycle, ovulation occurs on day 14.

Hormonal Regulation in the Luteal Phase

  • Post-ovulation is a time called the luteal phase
  • With the ovum expelled, the ruptured follicle becomes a temporary endocrine gland called the corpus luteum
  • This body begins to produce progesterone which does have a negative feedback effect on the hypothalamus and anterior pituitary gland
  • In 10-12 days, if no fertilization occurs, the corpus luteum degenerates into a corpus albicans

The Uterine Tubes

  • The uterine tubes (or Fallopian tubes or oviducts) are paired three-layer tubes that extend medio-laterally across the posterior abdominal wall
  • They conduct the oocyte from the ovary to the uterus
  • They are attached to the uterus at the isthmus
  • The middle section is the ampulla and is where fertilization should take place
  • The infundibulum flares into finger-like projections called fimbriae
  • Here, the ovary isn’t physically attached to the uterine tubes

The Uterus

  • The 2x3 inch uterus has three layers: the perimetrium of serous epithelial tissue, myometrium of smooth muscle, and the bi-layered endometrium of epithelial and connective tissue
  • It is shaped like an upside- down pear with a widened superior fundus, middle body, and narrow cervix
  • Ligaments affix the uterus to the pelvic wall and uterine tubes

The Endometrium

  • The endometrium has a permanent stratum basalis and a temporary stratum functionalis
  • The basalis is connected to the myometrium
  • The functionalis is shed during menses
  • It contains glands and grows under the influence of estrogen (which causes growth) and progesterone (which maintains it)

The Menstrual Cycle

  • Menses is the term for the shedding of the uterine lining during the female reproductive cycle
  • The menstrual cycle involves three phases: the menses phase, the proliferative phase, and the secretory phase
  • The cycle typically lasts on average 28 days but can range between 21 and 35 days

The Menses Phase

  • During this phase, the lining is shed
  • It ranges from 2 to 7 days with an average of 5
  • The first day of menses is considered the first day of a woman’s cycle
  • Declining progesterone levels, caused by the degeneration of the corpus luteum into the corpus albicans in the ovaries, bring on the shedding

The Proliferative Phase

  • Increasing amounts of estrogen due to the growing follicle in the ovaries cause the now shed uterine lining to begin building again
  • The end of this phase is marked by ovulation which, during a typical 28-day cycle, occurs on day 14

The Secretory Phase

  • The increasing levels of LH cause the secretory phase
  • The uterine lining is maintained while glands in the functionalis secrete glycogen-rich fluid that will nourish the zygote if fertilization has taken place and it implants
  • Arteries also begin to secrete even more blood into the uterine lining

Mammary Glands

  • The breasts supply nourishment in a process called lactation
  • Central to the breast is a pigmented area called the areola, containing glands that secrete a lubrication
  • The breast itself consists of modified sweat glands that are surrounded by adipose
  • Milk is created in clusters of milk secreting cells called alveoli
  • The milk exits through the nipple via ducts

The Onset of Puberty

  • About age 8 or 9, the hypothalamus begins to release Gonadotropin Releasing Hormone (GnRH)
  • GnRH prompts the Anterior Pituitary Gland to release Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH) in both genders
  • The hypothalamus becomes less sensitive to the negative feedback effect on these hormones
  • The gonads become more sensitive to these hormones
  • The actual onset of puberty varies but has been shown to be related to a number of things, among them genetics, the environment, psychological factors, and nutrition

Menopause

  • Fertility in the female peaks in the later 20s and declines slowly until 35 on average, after which it declines rapidly
  • After a full year without menses, a woman is said to have completed menopause
  • Reduced levels of estrogen and progesterone lead to a number of symptoms during menopause
  • Post-menopause, lowered estrogen can lead to other issues with female overall health