Reproductive System - Biology

At day 14 of a menstrual cycle, the LH surge begins, which causes the follicle to burst, resulting in ovulation. The LH surge is caused by a rise in estrogen, which causes the pituitary gland to release LH.

Progesterone ("pro-gestation") is responsible for the maintenance of a pregnancy. Initially, the corpus luteum secretes progesterone in preparation for pregnancy. Then, after fertilization, human chorionic gonadotropin (hCG) is released which causes the corpus luteum to keep secreting progesterone. The placenta takes over it's function after 6 weeks gestation.

Eggs, or oocytes, are produced in the ovaries. During ovulation, the egg is released from the ovary into the fallopian tube. If fertilized, the egg transitions into a zygote and is implanted into the uterus for gestation and development.

The spleen is involved in filtering the blood and lymph, and is not involved in reproduction.

The epididymis is responsible for storing sperm in order for it to mature. Upon ejaculation, it will be propelled into the vas deferens and out of the urethral opening.

Dysmenorrhea is a term used to describe painful cramps that are present during menstruation. In most cases, the cramps are cause by involuntary contractions of the uterus, which is a muscle. Amenorrhea describes the abnormal absence of a menstrual period. Mastodynia describes breast tenderness during menstruation. Menarche describes a female's first menstrual period.

The urinary bladder is not a part of the female reproductive tract. Rather, it collects urine created by the kidneys. The ovary produces the female gametes. The fallopian tubes transport the eggs from the ovary to the uterus each month. The uterus provides a location and the necessary nutrients to the fertilized egg that develops into the fetus. The vagina receives the penis during sexual intercourse and expels menstrual flow from the uterus.

Ejaculation is the act of ejecting sperm and semen from the male body. Fertilization and implantation are the first steps of pregnancy that occur inside the female body after sexual reproduction has begun. Transpiration is the evaporation of water from plant leaves.

Fertilization occurs when the genetic material from a sperm and egg combine to form a zygote. This is a form of sexual reproduction because it required the genetic information from two sources to combine**,** and then form another individual. The new offspring will have genetic material from both parents, making it genetically different from either individual parent.

Asexual reproduction occurs when the offspring come from a single parent and only have the genes from a single parent. Fission typically occurs in bacterial reproduction when a single organism splits into two; each of these pieces of the original organism forms a separate organism with the same genetic material as the parent. Budding occurs when a new organism is formed from a bud off of the original organism. When the process is completed, two separate organisms can survive on their own. Sporogenesis usually happens in plant and fungal species, and occurs when the parent organism forms spores which later develop into mature organisms. Vegetative propagation occurs when a piece of a "parent" plant is cultivated and develops into a new organism. This can be done by scientists and horticulturalists or it can occur naturally. None of these processes require more than a single organism to create offspring, and each offspring will be genetically identical to the parent.

There are three primary structures that contribute fluids to sperm in order to create semen in the body: the seminal vesicles, the prostate, and the bulbourethral glands. The pituitary gland has an impact on the development and maturation of sperm, but does not directly add fluid to semen.

As estrogen increases in the female body, it can cause a spike of luteinizing hormone (LH) resulting in a temporary positive feedback loop (the luteal surge). This spike in estrogen and LH levels causes the follicle to burst, releasing the egg into the fallopian tube. This event is called ovulation.

Females' ovaries secrete estrogen, testosterone, and progesterone. Estrogen has many functions, including development of female secondary sex characteristics. Such charactersistics include, but are not limited to: development of breast tissue, redistribution of body fat to the hips, thighs, buttocks, and breasts, and initiation of menses. In females, testosterone functions primarily to increase sexual arousal. Progesterone, luteinizing hormone, and follicle-stimulating hormone play roles in the menstrual cycle. The corpus luteum is formed from the follicle and remains in the ovary after the egg has been released. It secretes progesterone for about two weeks, then deteriorates in the absence of a pregnancy.

The male gonads, the testes, are responsible development and maturation of sperm and secretion of testosterone. Ovaries and fallopian tubes can be ruled out because they are found only in females, and thus do not contribute to the development of sperm. The prostate gland does not produce sperm, rather it secretes fluid that nourishes and protects sperm. The bulbourethral gland aids in the process of ejaculation.

Sperm are produced in the testes. They then travel into the epididymis where they mature and are stored. During the time of ejaculation, the sperm are expelled into the right and left vasa deferentia which join and form the urethra, through which they leave the body.

The bulbourethral glands aid in the process of ejaculation by lubricating the urethra. The thyroid, thymus and adrenal glands are not parts of the reproductive system. The thyroid gland secretes thyroid hormones which controls the body's metabolism and homeostasis. The thymus gland is responsible for secreting thymosine, which facilitates the maturation of T cells of the immune system. The adrenal glands are responsible for regulation of many body processes including the stress response, fluid and electrolyte balance, sex hormone production, blood glucose levels, and the fight, flight and fight response.

The anterior pituitary gland produces both FSH and LH, two hormones that play key roles in the menstrual cycle. The hypothalamus produces several tropic hormones and is responsible for maintaining homeostatis of the body via the endocrine system. The thyroid gland determines metabolic rate. The prostate gland does not produce any hormones. The uterus does not produce these two hormones; however, since LH and FSH regulate the menstrual cycle, events in the uterus are indirectly influenced by FSH and LH.

The menstrual phase is divided into two halves—the first 14 days are involved in follicular maturation, and is thus known as the follicular phase, while the last 14 days involve the degneration of the corpus luteum, and is thus known as the luteal phase. Ovulation occurs around day 14, but there is no ovulatory phase. Menstruation normally occurs during the first 2-7 days of the cycle, during the follicular phase.

Oxytocin is the hormone responsible for stimulating uterine contractions during pregnancy. All other answer choices occur via stimulation by estrogen.

Testosterone has many functions in males. Others functions than those listed include: enlargement of genitalia, increased libido, decrease in subcutaneous fat in face, aggression, and increased oil production—which may cause acne. In females, testosterone primarily functions to increase sexual arousal.

At the midpoint of the 28-day menstrual cycle, ovulation occurs. This involves the realease of one mature egg from the follicle in one ovary. Fertilization refers to the fusion of the nuclei of a sperm and an egg, resulting in a zygote. Menstruation occurs at the beginning of the menstrual cycle, around days 2-7. Gestation refers to the period marked by pregnancy. During the time of ovulation, progesterone levels are gradually rising, preparing the uterus for reception of the implanted zygote.

Testosterone is synthesized by Leydig cells. Sertoli cells aid in spermatogenesis. The seminal vesicles secrete semen, which comprises most of the seminal fluid. The scrotum is the skin pouch which contains the testes. The spermatic cord contains the vas deferens, nerves, blood vessels, and lymphatic vessels. Note that Leydig cells are sometimes called interstitial cells.