Reproductive Physiology - NCLEX-PN

Seminal fluid is formed by several glands: the prostate contributes proteolytic enzymes, citric acid, acid phosphatase, zinc, fibrinolysin, and prostate specific antigen. The seminal vesicles contribute various flavins, fructose, and amino acids. The bulbourethral glands secrete a mucus that allows the semen to travel rapidly through the urethra, potentially aiding its route toward the cervix.

The prostate, a fleshy endocrine gland inferior to the outlet of the male bladder, secretes a slightly alkaline milky fluid that makes up one third of the volume of semen. This alkalinity helps neutralize the acid environment of the vagina, increasing the likelihood of conception. Lubrication of the urethra is provided by the bulbourethral gland, while fructose is produced within the seminal vesicles. The prostate does not take part in sperm production.

The urethra travels through the corpus spongiosum, one of three cavernous bodies in the human penis. The other two cavernous bodies are a set of sponge-like erectile tissues called the corpus cavernosum. The vas deferens and epididymis are both part of the storage and transportation of semen. The vas deferens joins with the urethra in the penis to facilitate ejaculation.

The pudendal nerve transmits sensation from the external genitalia, the skin around the anus, and the perineum. It also provides motor function to several important structures in the area, including musculature of the pelvic floor, the external urethral sphincter, and the external anal sphincter. The other nerves listed do not provide any sensory or motor innervation to the genitals.

Most pregnancy tests detect human chorionic gonadotropin (hCG), a hormone produced by the embryo that is detectable shorty after implantation (10-14 days after fertilization). The function of hormone is to mimic the effects of luteinizing hormone, ultimately preserving the corpus luteum, which secretes progesterone. The progesterone maintains and vascularizes the uterus, making it a more favorable environment for the implanted embryo.

Luteinizing hormone stimulates the production of estrogen by the ovary, triggers the release of the mature egg during ovulation, and then stimulates the ruptured follicle to develop into the corpus luteum, the structure responsible for providing progesterone to the endometrium in preparation for implantation, if a pregnancy were to occur.

In polycystic ovarian syndrome (PCOS), luteinizing hormone (LH) levels are elevated, while follicle-stimulating hormone (FSH) levels are often low. Because FSH aromatizes androgens to estrogen, low FSH will cause androgens to increase. Low levels of FSH and high androgens keep the follicle from maturing & prevent ovulation. Hypogonadism is significantly more rare, and while extreme stress and poor nutrition may inhibit ovulation, in the United States PCOS is the leading cause of anovulation (failure to release an ovule from the ovary).

Normal FSH values for a menstruating adult female are . A FSH of would be considered normal in a premenarchal female, while normal FSH after menopause can range from .

In a menstruating woman, follicle-stimulating hormone stimulates the maturation of follicles in the ovary. Rupture of the mature follicle and formation of the corpus luteum are both stimulated by lutenizing hormone (LH). The uterus itself does not contain follicles.

In an adult male, normal FSH can range from . It may be slightly lower in children. Follicle-stimulating hormone is released from the anterior pituitary gland; its target is the testes.

In a healthy adult male, follicle stimulating hormone stimulates the Sertoli cells of the testes to produce androgen-binding protein, it stimulates primary spermatocytes to undergo meiosis, and triggers the initiation of spermatogenesis.

In a menstruating female, LH values can vary widely during the menstrual cycle. It is its highest at the peak of the menstrual cycle and lowest during the luteal phase of the menstrual cycle .

The Sertoli cells of the testes are responsible for the secretion of many substances, including anti-Müllerian hormone, androgen binding protein, glial cell line-derived neurotrophic factor, and estradiol.

Normal LH values for an adult male range from . These can be slightly lower in pre-pubescent males. Adult levels above can be seen in certain conditions of gonadal dysfunction, such as hypogonadism.

In an adult male, luteinizing hormone triggers the production of testosterone by the Leydig (interstitial) cells in the testes. Testosterone is converted to DHT (dihydrotestosterone) by the enzyme 5-alpha reductase. Sperm production and maturation is triggered by follicle-stimulating hormone (FSH) rather than LH in adult males.

The most prevalent and biologically active estrogen in an adult female is estradiol (E2). Estrone and estriol are less active forms of estrogen, and progesterone is not a form of estrogen, but rather a distinct progestogen reproductive hormone.

After menopause, the most predominant form of circulating estrogen is estrone (E1). Estradiol is more prevalent in pre-menopausal women who are not pregnant, while estriol and estetrol are both only elevated during pregnancy.

The only form of estrogen that is exclusively present in pregnant women is estetrol (E4).

The conversion of androgens into estrogen is performed by aromatase, also known as estrogen synthetase or estrogen synthase. 5-alpha-reductase is responsible for the conversion of testosterone to dihydrotestosterone. Amylase is a salivary enzyme that breaks down starches during mastication, and protease is a digestive enzyme that aids in the breakdown of proteins.

All of the hormones listed, and testosterone, are androgens except 2-hydroxyestrone, which is a metabolite of estrone (a form of estrogen).