Ch 24- Structure & Function of the Reproductive System

• Initially, male and female embryo reproductive structures consist of one pair of primary sex organs (gonads) and two pairs of ducts (mesonephric/wolffian and paramesonephric/müllerian), both emptying into the urogenital sinus.

Internal Structures Development:

• Reproduction system development begins in the fifth week of gestation.
• Male embryo differentiation happens around 6 to 7 weeks of gestation, influenced by testes-determining factor (SRY gene on the Y chromosome).
• Expression of the SRY gene leads to male gonadal development.
• Testosterone secretion starts, stimulated by TDF, around 8 weeks of gestation, which develops the male gonads into testes.
• By 9 months' gestation, the male gonads (testes) descend into the scrotum.
• After puberty, the testes produce sperm.
• Female gonadal development occurs without SRY expression, but with the expression of other genes.
• Regression of the wolffian system is caused by estrogen presence and testosterone absence.
• At 6 to 8 weeks' gestation, female gonads develop into ovaries to produce ova.
• By the 10th week of gestation, loss of wolffian ducts allows müllerian ducts to form the uterus, fallopian tubes, cervix, and upper two thirds of the vagina.

External Structure Development

• During the first 7 to 8 weeks of gestation, male and female embryos develop a genital tubercle.
• Testosterone is needed for the genital tubercle to differentiate into male genitalia; otherwise, female genitalia develop.

Hormone Production

• Anterior pituitary gland development starts between the 4th and 6th weeks of fetal life; the vascular connection between the hypothalamus and pituitary is established by the 12th week
• The hypothalamus produces Gonadotropin-releasing hormone (GnRH) by 10 weeks gestation and it controls the production of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) by the anterior pituitary gland.
• High levels of FSH and LH are excreted in the female fetus.
• FSH and LH stimulate estrogen and progesterone production by the ovary.
• FSH and LH production rises until about 28 weeks gestation, until the production of estrogen and progesterone by the ovaries and placenta is high enough to decrease gonadotropin production.
• Production of primitive female gametes (ova) occurs solely during fetal life.

Female GU System

• The female reproductive system functions to produce mature ova
• It provides protection/nourishment of the fetus if fertilization occurs until birth
• The ovaries, fallopian tubes, uterus, and vagina are the most important internal reproductive organs in females.

External Genitalia

• The mons pubis (mons veneris) is a fatty tissue layer over the pubic symphysis that gets covered in hair with active sebaceous/sweat glands during puberty, becoming mound-like because of estrogen.
• During sexual arousal, the labia swell with blood.
• Labia majora (labium majus) are two folds of skin arising at the mons pubis/extending back to the fourchette and protect inner vulva structures, which is highly sensitive to pain, pressure, touch and temperature.
• Labia minora (labium minus) are two smaller, thinner folds inside labia majora that form the clitoral hood and frenulum, converging near the anus to form the fourchette, which split to enclose the vestibule, and contain moist, pink, hairless skin with sebaceous glands, blood vessels, and nerves.
• The clitoris is richly innervated, an erectile organ between the labia minora with a visible glans/shaft and secretes smegma; sexual arousal fills erectile tissues, causing slight enlargement.
• The vestibule is an area protected by the labia minora, which contains the external opening of the vagina (introitus), the opening to the urethra and urinary meatus, and may have a thin membrane-covered introitus called the hymen.
• Skene glands lubricate the urinary meatus and the vestibule, opening on each side of the urinary meatus
• Bartholin glands secrete mucous to lubricate inner labial surfaces and enhance sperm motility, opening on each side of the introitus.
• Secretions from both gland sets facilitate coitus; sexual excitement causes highly vascular tissue under the vestibule to fill with blood and become engorged.
• The perineum is the area of skin covering the muscular perineal body (fibrous structure of connective/elastic tissue) and subcutaneous tissue lying beneath the vaginal orifice and anus with little subcutaneous fat, attaching to the bulbocavernosus, the external anal sphincter, and the levator ani muscles.
• The length of the perineum and the elasticity of the perineal body influences tissue resistance and injury during childbirth and varies in length (2-5+ cm)

Internal Genitalia

• Vagina: an elastic fibromuscular canal (9 - 10 cm long) lying between the rectum and the urethra that receives the penis during coitus, and is the canal through which mucosal secretions from the upper genital organs, menstrual fluids, and products of conception leave the body.
• The vaginal wall consists of four layers:
• Mucous membrane lining of squamous epithelial cells thickens and thins in response to hormones, particularly estrogen
• The squamous epithelial membrane is continuous with the membrane that covers the lower part of the uterus.
• The mucosal layer is arranged in transverse wrinkles/folds called rugae and permit stretching during childbirth and coitus in women of reproductive age.
• Fibrous connective tissue containing numerous blood and lymphatic vessels
• Smooth muscle
• Connective tissue and rich network of blood vessels
• Upper vagina surrounds cervix (lower end of the uterus)
• Recessed space around cervix is called the fornix of the vagina, where the cul-de-sac separates the posterior fornix and the rectum forming a pouch.
• The vaginal wall becomes engorged with blood during sexual arousal → fluid to the mucosa surface, enhancing lubrication.
• Two factors help maintain the self-cleansing action of the vagina and defend it from infection:
• Acid-base balance discourages proliferation of most pathogenic bacteria.
  • At puberty the pH is more acidic (4-5) and the lining of squamous epithelial thickens.
  • Protection is greatest during the years when a woman is most likely to be sexually active.
    • Defenses are greatest when estrogen levels are high.
    • The vagina contains a normal population of lactobacillus acidophilus.
  • Any condition that causes the vaginal pH to rise (i.e., douching/vaginal sprays/deodorants, low estrogen levels, destruction of L. acidophilus by antibiotics) → lowers vaginal defenses
• Uterus: hollow pear-shaped organ whose lower end opens into the vagina, anchors/protects a fertilized ovum, offers optimal environment for ovum’s development, and expels fetus
• During sexual excitement, opening of the uterus (cervix) goes up/back, uterus size increases slightly, cervix dilates, and the cervix is in a pool of semen.
• The uterus is made up of two major parts:
• Corpus (body)
• Fundus (top of corpus).
• Cervix: neck of the uterus, acting as a mechanical barrier to infectious microorganisms coming from vagina
• The uterine wall consists of three layers:
• Perimetrium: outer membrane.
• Myometrium: a thick muscular layer.
• Endometrium: uterine lining is responsive to the sex hormones estrogen and progesterone, sloughing off monthly and proliferating between menopause and puberty.
• Fallopian tubes conduct the ova from the spaces around the ovaries to the uterus, entering bilaterally beneath the fundus.
• Infundibulum: widened/fringed end
• Fimbriae: move and create the current drawing the ovum into the infundibulum.
• Ampulla: usual fertilization site (distal third of the fallopian tube)
• Ovaries: considered the primary reproductive organs in females or female gonads, are responsible for development/release of female gametes/ova and secretion of female sex hormones.
• Ovarian cycle: process of follicular maturation, ovulation, corpus luteum growth, and corpus luteum degeneration is continuous from puberty to menopause, but not during hormonal contraceptive use or pregnancy.

Hormones in Menstruation

• Estrogen is a generic term for three similar hormones: estradiol, estrone, and estriol, with estradiol most potent and plentiful, principally produced (95%) by the ovaries (ovarian follicle and corpus luteum).

1. Estrogen has numerous biologic effects and involves interactions with other hormones which lead to the maturation of reproductive organs, secondary sex characteristics, regulation of the menstrual cycle, endometrial regeneration after menstruation, and closure of long bones after the pubertal growth spurt.
2. Estrogen also effects the brain, kidneys, liver, blood vessels, central nervous system, bones, and skin.

Complementary and Opposing Effects of Estrogen and Progesterone

• Vaginal mucosa: Estrogen's effect is the proliferation of squamous epithelium, increase in glycogen content of cells; layering, while progesterone's effect is thinning of squamous epithelium and decornification.
• Cervical mucosa: Estrogen's effect is the production of abundant fluid secretions that favors survival and enhances motility of sperm, while progesterone's effect is the production of thick, sticky secretions that tend to plug the cervical os.
• Fallopian tube: Estrogen's effect is the increase of motility and ciliary action, while progesterone's effect is the decrease of motility and ciliary action.
• Uterine muscle: Estrogen's effect is the increase of blood flow, contractile proteins, uterine muscle, myometrial excitability to action potential, and sensitization to oxytocin, while progesterone's effect is the relaxation of myometrium and the decrease of sensitization to oxytocin.
• Endometrium: Estrogen stimulates the growth and increases the number of progesterone receptors, while progesterone activates glands and blood vessels, increasing the number of glycogen/enzymes, and decreases the number of estrogen receptors.
• Breasts: Estrogen causes the growth of ducts and promotes prolactin effects, while progesterone leads to the growth of lobules/alveoli and inhibits prolactin effects.
• Follicle-stimulating hormone (FSH): synthesized/secreted by gonadotrophs of anterior pituitary gland, it regulates body development, growth, pubertal maturation, and reproductive body processes, working synergistically with luteinizing hormone (LH) to act in reproduction
• Luteinizing hormone (LH) is derived from the anterior pituitary and stimulates the corpus luteum to secrete progesterone

More Hormones

• Gonadotropin-releasing hormone (GnRH): produced in the hypothalamus, which controls LH/FSH production.
• Menstruation: menstrual bleeding starts with menarche (first menstruation) and ends with menopause (cessation of menstrual flow), and menstrual bleeding (menses).
• Menarche is related to body weight (especially % body fat), triggering a change in the metabolic rate and leading to hormonal changes linked to early menarche
• Anovulatory cycles vary initially and fluctuate in length from 10 to 60+ days and become more regular as you become an adult (21 - 45 days)
• A common, accepted cycle is 28 (27 to 30) days, with 21 - 35 days being a normal rhythmic interval
• Cycles start to lengthen 2 - 8 years before menopause because of variations related to altering hormones

Hormonal Feedback Mechanism in The Menstrual Cycle

• Early Follicular Phase: Low estrogen levels and minute amounts of progesterone are secreted that stimulate the hypothalamus and anterior pituitary, resulting in low GnRH, FSH, and LH levels which lead to ovarian follicle development, and endometrium proliferation.
• Late Follicular (Preovulatory) Phase: High estrogen levels and high progesterone increases with a small surge before ovulation that positively stimulate the hypothalamus and anterior pituitary, resulting in all surges and LH dominates that starts the process of ovulation and ends with complete endometrial proliferation.
• Ovulatory Phase: Estrogen levels dip and progesterone levels begin to rise caused by negative and inhibitory feedback to the hypothalamus and anterior pituitary, resulting in all falling sharply, the corpus luteum begins to develop, and the endometrium enters the secretory phase.
• Early Luteal Phase: High estrogen and progesterone levels inhibiting the hypothalamus and anterior pituitary leads to levels continuing to decline, but gradually that results in corpus luteum fully developed and complete, and the endometrium is ready for implantation
• Late Luteal Phase: Late luteal phase feedback lessens slightly, and estrogen/progesterone sharply decreasing, leads to slightly increased GnRH, FSH, and LH levels, corpus luteum regression, broken down endometrium, and menstruation.
• Menstrual Phase: Low levels of minute amounts of hormones leads to negative and inhibitory influence over the hypothalamus and anterior pituitary, resulting in all low, more ovarian follicles developing, functional layer of endometrium being shed

Ovulation, Menopause, and Dysmenorrhea

• Ovulation is marked by the rise in LH.

1. FSH rises from the late luteal phase decline of estrogen, progesterone, and inhibin, stimulating granulosa cell growth and estrogen production in these cells in the next cycle
2. Minor increase in LH levels
3. Progesterone, proteolytic enzymes and prostaglandins trigger mechanisms that rupture the follicle and release the ovum

• FSH and LH transforms granulosa cells of the ovulatory follicle into corpus luteum that secretes estrogen and progesterone relative to good follicle development.
• Menopause is marked by 12 consecutive months of amenorrhea and characterized by a loss of ovarian follicles, low estradiol, lower progesterone but high FSH/LH, and a possible increase in sensitivity to lower androgen production because of the loss of estrogen's opposition.

Dysmenorrhea

• Painful menstruation associated with the release of prostaglandins in ovulatory cycles without pelvic disease (Primary).
• Excessive endometrial prostaglandin production (potent myometrial stimulant and vasoconstrictor)

1. Elevated levels of prostaglandins leads to increased uterine hypercontractility, decreased blood flow to uterus, increased nerve hypersensitivity, and PAIN.
2. Elevated leukotriene production further, increased synthesis of prostaglandins, and upregulation of cyclo-oxygenase enzyme function

• Pelvic pathologic disorders (Secondary).

1. Endometriosis (most common)
2. Endometritis (infection)
3. Adenomyosis
4. PID
5. Obstructive uterine or vaginal anomalies
6. Uterine fibroids
7. Polyps
8. Tumors and Ovarian cysts
9. Pelvic congestion syndrome

• breast milk nutrient composition changes over time to accommodate changing digestive capabilities and nutrition needs.

Breast Milk

• Physiologically, breast milk is the most appropriate newborn nourishment
• Colostrum (in low quantities postpartum) contains immunologic components of secretory IgA, lactoferrin, leukocytes, and epidermal growth factor-related developmental factors
• Lysosomes, Secretory IgA, and nonspecific antimicrobial factors, protect the infant against infection, asthma, and allergies.

Male External Genitalia

• The testes are essential for reproduction.
• Gametes produced include sperm
• Sex hormones produced include testosterone and androgens
• Suspended outside of the pelvic cavity, where the temperature is 1°C to 2°C (1.6°F-3.6°F) cooler than the body
• The spermatic cord suspends the tissues in the scrotal sac
• The tunica vaginalis is the outer tissue
• An inward extension of the tunica albuginea forms septa separating each into 250 different lobules/compartments that each has seminiferous tubules
• Tunica albuginea is the inner layer, which create septa dividing each testes into 250 compartments
• These tubules constitute 80% of the testicular volume and produce sperm surrounding the tissue, supporting blood/lymphatic vessels, macrophages, mast cells, fibroblastic support cells, and Leydig cells
• Leydig cells produce the testosterone androgen
• Seminiferous tubules each join and leave the lobule with the tubulus rectus connecting to the testis' central portion; the rete testis.
• Sperm travel from the seminiferous tubules, leading toward to the rete testis.
• Sperm moves from the rete testis through the efferent tubules/vasa efferentia to undergo maturation in the epididymis.
• The epididymis is comma-shaped, curves over the posterior of each testis that is composed of the coiled duct to conduct sperm from the efferent tubules to the vas deferens.
• The epididymis continues with the vas deferens where layers of muscular tissue conduct Sperm toward the urethra that are stored in the epididymal tail
• Scrotum: encloses/protects testes, spermatic cord, the epididymides
• Covered in rugae-textured skin which is thin to shrink for relaxation
• Under skin is a layer of tissue that helps regulate the environmental temperatures
• Penis: functions to eliminate urine and delivers sperm to the vaginal canal.
• Homologous the female clitoris.
• It internally contains the urethra and three muscle sections enclosed in a tuncia albuginea and the Buck fascia
• The structures inside are two corpora cavernosa and the corpus spongiosum
• The corpus spongiosum and ends at a sagittal slit in the glands.
• The urethra passes through that
• The urethra is not completely surrounded, leading to either the ventral surface (hypospadias) or the dorsal surface (epispadias) depending on the meatus, which may open on the penile shaft
• Engorgement of erectile tissues can cause penetration of the female vagina possible with 20-50 ml of blood.

Male Internal Genitalia

• Duets: Vasa deferentia, the uretha, the ejaculatory duct, conduct sperm from the testicular glands to the penis
• Glands: the prostate gland, seminal vesicles, and Cowper bulbourethral that secrete fluids to transport transport sperm, enhance motility and survival, and create a nutritious environment
• As the sperm move through the vas deferens they travel to the seminal vesicles behind the urinary bladder where they secrete a nutritive fluid rich from glucose
• Seminal vesicles provide fructose for energy and secrete a fluid of prostaglandin smooth muscle which helps with sperm transport.
• Seminal vesicle ducts join the vas deferens to become an ejaculatory duct.

Prostate

• Walnut sized gland surrounding the urethra structured with alveoli and fibers and with growth, development, and function androgens are regulated, making the location at high risk for malignant growth
• Required nerves travel along the surface, and epithelial secretions include prostate-specific antigen (psa), cytokeratins
• Prostatic portion of of ejaculation also helps keep the right balance and motility of fluids to enhance fertility
• Prostatic fluid helps sperm with alkaline PH survive.
• Helps mobalize sperm after ejaculation through enzymes

Cowper Glands

• Last pair of glands to add fluid to the ejaculate, which secretes mucus from the bulbourethral onto the base glands
  • Muscles push semen out from the penis base and into the vagina with about 2-6ml volume and 75-400 million sperm
• There are a low amount of ejaculate fluids (2%) vasectomy that that prevent sperm
• The vas deferens are severed to prevent sperm from the ejaculate.

What is the pathophysiology behind the signs and symptoms of menopause?

• Caused from ovarian failure to mark the end of reproduction normally between 50/53/4 in North America and is causative from genetic and lifestyle factors Premature menopause happens before age of ovulation for age
• The point is marked by 12 months of consecutive amenhorrhea Climacteric happens as symptoms start before and loss of follicular production of increased increased FSH, and LH
• 90% of women at perimenopause which fluctuate quality Estriadioal increases and cycles become anovulatroy
• Declines 1 year prior

Perimenopause Primary Utero and Ovarian

• Folliciles decrease and become atresia from stimulation
• Stimulation is increased which decreases mullein hormone
• Located in the endometric primarily
• Breast tissue and smaller and and lose formness from lack of fat and fat and connective tissue