Reproductive Physiology - NCLEX-PN

During a normal pregnancy, the volume of blood plasma increases by 50%. The erythrocyte count also increases, by as much as 30%. This may cause the hematocrit to appear lower than normal, due to dilution by the relatively larger increase in plasma.

While research is still being conducted to determine the cause of nausea and vomiting of pregnancy, it generally correlates with the surge in human chorionic gonadotropin (hCH) that occurs in the first trimester. Estrogen may be another contributing hormone. Aldosterone, DHEA, and corticotropin-releasing hormone (CRH) have no apparent involvement.

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.

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).

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.

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.

A fetus that assumes a "head down" position during labor is said to have a cephalic presentation. The infant may still be oriented in a number of directions, such as vertex position, with the occiput anterior and the face and front of the body toward the mother's spine, face presentation with the head tilted back into full neck extension, or occpito-posterior, in which the occiput is against the sacrum. In a transverse presentation, the fetus is sidelong, while a breech presentation the fetus' head is superior while the legs are inferior.

Contractions in labor are stimulated by oxytocin, a nonapeptide hormone produced in the hypothalamus and stored in the posterior pituitary. Oxytocin also triggers postpartum contractions in order to compress the lax uterine wall and reduce postpartum bleeding. Prolactin is a hormone essential to breast-milk production, while estrogen and progesterone have a multitude of roles in both fetal and placental development.

Oxytocin, a nonapeptide hormone produced in the hypothalamus, has a variety of physiological roles. It increases trust, generosity, and other markers of social cohesion. In intimate relationships, it increases feelings of affection, love, sexual arousal, and contentment. It is an important hormone in labor, as it triggers contractions both during labor and postpartum in order to reduce bleeding and uterine size after delivery. It also acts as an immune modulator in wound healing. It does not, however, increase appetite - studies have shown it to have the opposite effect, acting as an appetite suppressant in human and animal models.

The designations for parity are as follows:

• Nulliparous: Never delivered a child or carried a pregnancy past 20 weeks
• Primiparous: Has given birth once or is about to give birth for the first time
• Multiparous: Has given birth twice
• Grand multiparous: Has given birth three or more times

During the later stages of labor, the cervix, normally a four centimeter-long muscular sphincter, releases its mucus plug, then thins and shortens. The release of the mucus plug is termed the "bloody-show," and the thinning and shortening of the cervix is called effacement. Cervical effacement is almost always accompanied by cervical dilation, or a widening of the os in order to allow passage of the fetus. This all happens in the transition phase of labor.

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 .