All-female mammals possess a pair of functional mammary glands. Neutrophils migrate readily through midcycle human cervical mucus (Parkhurst and Saltzman, 1994). A pregnancy may end in a live birth, a miscarriage, Naturally occurring hormones drive the cycles; the cyclical rise and fall of the follicle stimulating hormone prompts the production and growth of oocytes (immature egg cells). Assisted conception in humans and other mammals relies on techniques to either assist sperm to reach the site of fertilization (by techniques of insemination) or generate embryos in the laboratory (by means of IVF) that can then be returned to the uterine cavity at a later time. This fluid is rich in enzymes, proteins, vitamin C, fructose, prostaglandins, and phosphorylcholine. Bleeding from a ruptured ectopic pregnancy is usually intra-abdominal, not vaginal. for Permissions, please email: journals.permissions@oupjournals.org, The impact of vincristine on testicular development and function in childhood cancer, Contraceptives and cancer risks in BRCA1/2 pathogenic variant carriers: a systematic review and meta-analysis, Temporal trends in sperm count: a systematic review and meta-regression analysis of samples collected globally in the 20th and 21st centuries, Efficacy of psychological interventions for mental health and pregnancy rates among individuals with infertility: a systematic review and meta-analysis, About the European Society of Human Reproduction and Embryology, Vaginal defenses against infectious organisms may affect sperm, Transport through the uterotubal junction, Preserving sperm fertility during storage, Advancement of sperm beyond the tubal reservoir, Hyperactivation of sperm and the final stages of transport, Receive exclusive offers and updates from Oxford Academic, Copyright 2022 Human Reproduction Update. Other uncategorized cookies are those that are being analyzed and have not been classified into a category as yet. The serum B-hCG should be monitored every 48 hrs to ensure it is falling by equal to or greater 50% of the level until it falls to approximately <5mIU/ml. Its also commonly described as an upside-down pear. There also can be a history of amenorrhoea. In addition to providing a haven, the storage reservoir maintains the fertility of sperm until ovulation. In a variety of non-human species, this phenomenon has been seen in vitro or in vivo (Suarez, 1987; Suarez et al., 1990, 1991a; Smith and Yanagimachi, 1991; Thomas et al., 1994; Petrunkina et al., 2004). Some species, such as pigs, bypass the vagina altogether and deposit semen directly into the uterine cavity, where sperm may quickly gain access to the oviduct (Hunter, 1981; Roberts, 1986). The dominant follicle continues to secrete estrogen, and the rising estrogen levels make the pituitary more responsive to GnRH from the hypothalamus. By BruceBlaus [CC BY-SA 4.0], via Wikimedia Commons, By Hggstrm, Mikael. [4] At puberty, a child's body begins to mature into an adult body capable of sexual reproduction; the first period (called menarche) occurs at around 12 years of age and continues for about 3045 years. In estrous domestic cats, both ascending and descending contractions were observed by fluoroscopy (Chatdarong et al., 2002). [47], Only two-thirds of overtly normal menstrual cycles are ovulatory, that is, cycles in which ovulation occurs. It has three main differential diagnoses; (i) very early intrauterine pregnancy; (ii) miscarriage; and (iii) ectopic pregnancy. [58] In early pregnancy progesterone also increases blood flow and reduces the contractility of the smooth muscle in the uterus[22] and raises the woman's basal body temperature. Capacitation involves changes in the plasma membrane, including shedding of proteins and cholesterol, that prepare sperm to undergo the acrosome reaction and fertilize oocytes (reviewed by De Jonge, 2005) and therefore loss or modification of proteins on the surface of the plasma could reduce affinity for the endosalpingeal epithelium. There is evidence that the estrogens enhance contraction by stimulating secretion of PGF-2 (Claus, 1990). Rapid transport of sperm through the uterus by myometrial contractions can enhance sperm survival by propelling them past the immunological defenses of the female. The oogonia form primary oocytes that form by the process of meiosis and get arrested at the stage of Prophase. Students can learn many important things about the process of reproduction in this chapter. Webfallopian tube, also called oviduct or uterine tube, either of a pair of long narrow ducts located in the human female abdominal cavity that transport male sperm cells to the egg, provide a suitable environment for fertilization, and transport the egg from the ovary, where it is produced, to the central channel (lumen) of the uterus. [15] The other third lack ovulation or have a short luteal phase (less than ten days[60]) in which progesterone production is insufficient for normal physiology and fertility. In rabbits and humans, vaginal insemination stimulates the migration of leukocytes, particularly neutrophils and macrophages, into the cervix as well as into the vagina (Tyler, 1977; Pandya and Cohen, 1985). D) uterus. [31] As they mature, the ovarian follicles secrete increasing amounts of estradiol, an estrogen. It transports the sperm from the epididymis to the ejaculatory duct. This phenomenon induces the secondary oocyte to complete meiosis. ", "The microenvironment of human implantation: determinant of reproductive success", "Autonomic control of body temperature and blood pressure: influences of female sex hormones", 1983/c0c1058c-553b-4563-8dd1-b047d9b672c1, "Abnormal uterine bleeding in adolescents", "Primary Dysmenorrhea: Diagnosis and Therapy", "The impact of menstrual cycle phase on athletes' performance: a narrative review", "The cycling brain: menstrual cycle related fluctuations in hippocampal and fronto-striatal activation and connectivity during cognitive tasks", "Cognition, the menstrual cycle, and premenstrual disorders: a review", "Evaluation of acute pelvic pain in women", "Treatments for seizures in catamenial (menstrual-related) epilepsy", "There might be blood: a scoping review on women's responses to contraceptive-induced menstrual bleeding changes", "First evidence of a menstruating rodent: the spiny mouse(Acomyscahirinus)", "Altered exploratory behaviour and increased food intake in the spiny mouse before menstruation: a unique pre-clinical model for examining premenstrual syndrome", "Characteristics of the endometrium in menstruating species: lessons learned from the animal kingdom", "The evolution of menstruation: a new model for genetic assimilation: explaining molecular origins of maternal responses to fetal invasiveness", "Testosterone and reproductive effort in male primates", Extended cycle combined hormonal contraceptive, The Convention on the Elimination of All Forms of Discrimination against Women, Declaration on the elimination of violence against women, International Center for Research on Women, https://en.wikipedia.org/w/index.php?title=Menstrual_cycle&oldid=1126137904, Short description is different from Wikidata, Creative Commons Attribution-ShareAlike License 3.0, This page was last edited on 7 December 2022, at 19:10. Pregnancy usually occurs by sexual intercourse, but can also occur through assisted reproductive technology procedures. It is a cushion of fatty tissue which is covered by hair and skin. Removal of the seminal vesicles significantly reduced the pregnancy rate in mice (Peitz and Olds-Clarke, 1986). [4][67][66][68] Dysmenorrhea (menstrual cramps or period pain) is felt as painful cramps in the abdomen that can spread to the back and upper thighs during the first few days of menstruation. The sex chromosome in the sperm is the factor that determined the sex of the fetus. Note: In a salpingotomy, HCG follow up is required until the level reaches <5iU (negative), to ensure there is no residual trophoblast. At first, we have mentioned the topics covered in this class 12 Biology chapter 3 notes PDF below: The initial section in chapter 3 Biology class 12 notes begin with the explanation and diagrammatic representation of both male and female reproductive organs. Mons Pubis: It is a cushion of fatty tissue which is covered by hair and skin. The ovarian cycle describes changes that occur in the follicles of the ovary,[1] whereas the uterine cycle describes changes in the endometrial lining of the uterus. [2] Following further stimulation by LH, the corpus luteum produces and releases estrogen, progesterone, relaxin (which relaxes the uterus by inhibiting contractions of the myometrium), and inhibin (which inhibits further secretion of FSH). Testis is oval in shape with the length of 4-5cm and 2-3cm wide. Your uterus is one of the most unique organs in your body. Glucose is a nutrient for the egg and sperm, whereas the rest of the chemicals provide an appropriate environment for fertilization to occur. The risk factors for an ectopic pregnancy are shown in Table 1. The female reproductive system is made up of several parts: The ovaries are small and oval-shaped and are known as primary female sex organs. First is the outer layer called the trophoblast and the other is the inner cell mass which is attached to the trophoblast. Luteinizing Hormone (LH): LH is important in regulating the function of testes and ovaries. Found an error? This causes them to spasm, contract and break up. The uterotubal junction presents anatomical, physiological and/or mucous barriers to sperm passage in most mammals. However, in a 5 year study of 11 female volunteers Baker and Bellis (1993) examined the characteristics of sperm loss from the vagina following coitus (flowback). It is designed like an inverted pear and attached to the pelvic wall by ligaments. menopause. [77] Improvements in spatial reasoning ability during the menstruation phase of the cycle are probably caused by decreases in levels of estrogen and progesterone. The uterus, also known as the womb, is an about 8 cm long hollow muscular organ in the female pelvis and lies dorsocranially on the bladder.It consists of several anatomical parts, such as the cervix, isthmus, and body. This cookie is set by GDPR Cookie Consent plugin. The fertilized ovum divides mitotically to become a blastocyst , which implants into the endometrium and derives nourishment from blood vessels which develop exclusively for this purpose. Furthermore they estimated that a median of 35% of spermatozoa were lost through flowback but that in 12% of copulations almost 100% of the sperm inseminated were eliminated. Menstruation: In this process, the blood and mucosal tissue are regularly discharged in a periodic manner. WebThe fallopian tubes, also known as uterine tubes, oviducts or salpinges (singular salpinx), are paired tubes in the human female that stretch from the uterus to the ovaries.The fallopian tubes are part of the female reproductive system.In other mammals they are only called oviducts.. Each tube is a muscular hollow organ that is on average between 10 Knowledge of the biology of sperm transport can inspire improvements in artificial insemination, IVF, the diagnosis of infertility and the development of contraceptives. Biology Notes for Class 12 Chapter 3 Free PDF Download, Key Points of CBSE Class 12 Revision Notes, Download the NCERT Class 12 revision notes today and accelerate your preparation in an appropriate manner. In this phase, the levels of LH and FSH attain a peak at mid-cycle, around the 14th day. You can also check out, for Physics, Chemistry, Maths, Economics, Business Studies and more by visiting our website. Whereas, a bull normally deposits several billion sperm into the vagina, artificial inseminators deposit 520 million frozen/thawed sperm directly into the body of the uterus leading to successful conception about 70% of the time (Foote and Kaproth, 1997; Lpez-Gatius, 2000; Vishwanath, 2003). The ovarian cycle controls the production and release of eggs and the cyclic release of estrogen and progesterone.The uterine cycle governs the preparation and It is a long, coiled tube that connects a testicle to a vas deferens. Vaginal examination may reveal fullness in the pouch of Douglas. It shows strong contractions at the time of the delivery of the baby. Menopause is defined as the permanent ceasing of the menstrual cycle in females. Each fallopian tube is 1013 cm (45 inches) long and 0.51.2 cm (0.20.6 inch) in diameter. During this phase usually only one ovarian follicle fully matures and gets ready to release an egg. While its anatomy sounds simple, its histology is more complicated. Vas Deferens: Vas deferens is a muscular duct that ascends into the abdominal cavity and makes a loop over the urinary bladder. 1. The secretion of these glands helps in the lubrication of the penis and also neutralizes any residual acidity in the urethra. Fig 1 An ectopic pregnancy is one that is implanted outside the uterine cavity. Luteal Phase: This is the phase of formation of the corpus luteum and it is also known as the secretary phase. Infundibulum: It is a proximal part of the oviduct that is present closer to the ovary. As the time of ovulation approaches, sperm become capacitated and hyperactivated, which enables them to proceed towards the tubal ampulla. Free access to premium services like Tuneln, Mubi and more. A small muscular sac is known as Scrotum that contains and protects the testes. Spermatogonium (singular) is diploid in nature and contains 46 chromosomes. The ovaries also secrete hormones that play a role in the menstrual cycle and fertility. Coitus on the day of maximal mucus hydration in women is more closely correlated with incidence of pregnancy than coitus timed with respect to ovulation detected using basal body temperature (Bigelow et al., 2004). What do you know about spermatogenesis Class 12 Biology? Peak levels of estrogen are reached at around day thirteen of the cycle and coincide with ovulation. Approximately 200-300 million sperms are released during ejaculation. [82][83], Hormonal contraceptives prevent pregnancy by inhibiting the secretion of the hormones, FSH, LH and GnRH. Fluoroscopy and scintigraphy have been used in domestic dogs and cats to examine cervical patency. Reproduced from Pacey et al. The fundamental parts of a male reproductive system are testes, accessory ducts, glands and external genitalia. If it is not fertilized by a sperm, the oocyte degenerates. It mainly occurs in female primates like monkeys, apes, and human beings. A few thousand sperm swim through the uterotubal junctions to reach the Fallopian tubes (uterine tubes, oviducts) where sperm are stored in a reservoir, or at least maintained in a fertile state, by interacting with endosalpingeal (oviductal) epithelium. This is when pregnancy officially begins, and you miss your menstrual period. These cycles are concurrent and coordinated, normally last between 21 and 35 days, with a median length of 28 days, and continue for about 3045 years. Activate your 30 day free trialto continue reading. Although a distinct tubal sperm reservoir has not been reported for humans, hyperactivation and capacitation could serve to speed sperm movement into the ampulla as the time of ovulation approaches. An additional factor, likely a sperm surface protein or proteins, is required by each sperm for it to pass through the junction. If positive, a pelvic USS should be performed this can determine the presence or absence of an intrauterine (normal) pregnancy. Vigorously motile sperm have been recovered from the human cervix up to 5 days after insemination (Gould et al., 1984), and the presence of sperm in mid-cycle cervical mucus forms the basis of the post coital test (PCT) (Mortimer, 1994). Sperm progress would also be slowed by the mucus in the lumen. This is the process by which sperms are released from the seminiferous tubules. Since boar semen is deposited directly into the uterine cavity, the uterus is exposed to the full amount of estrogens in the semen. [15] Although the average length of the human menstrual cycle is similar to that of the lunar cycle, there is no causal relation between the two. This plexus has been well described in cattle (Wrobel et al., 1993). The testes are sited outside the abdominal cavity to maintaining the low temperature of the testes nearly 2-2.5C lower than the average human body temperature. These revision notes will aid in a quick and efficient revision of every chapter, thereby saving your time during stressful exam days. The other cells are discarded as polar bodies, which cannot be fertilized. If one were found, it could have vast implications for the development of contraceptives, as well as assessment and treatment of infertility. Whereas most of the semen of murine rodents is rapidly transported into the uterine cavity, some remains in the vagina where it coagulates to form a copulatory plug. [40] Falling levels of progesterone trigger menstruation and the beginning of the next cycle. Cervix: The lowest part of your uterus. This information is intended for medical education, and does not create any doctor-patient relationship, and should not be used as a substitute for professional diagnosis and treatment. Spermatogonia: They are the immature male germ cells that undergo meiotic divisions to form sperms. Note: Vaginal bleeding in ectopic pregnancy is the result of decidual breakdown in the uterine cavity due to suboptimal -HCG levels. Doppler flow sonography revealed increased perfusion of these anastomosing vessels on the side of the pre-ovulatory follicle (Kunz, 1998). Although a visibly distinct sperm reservoir has not been seen in the Fallopian tubes of humans, a functional reservoir may be created by detaining human sperm in the tubal isthmus. Taken together, these observations indicate that capacitation-induced changes in the sperm head surface are responsible for reducing binding affinity, although the pull produced by hyperactivation can almost certainly hasten the detachment of bound sperm from the epithelium. [55] For women who are practicing fertility awareness, it is a sign that ovulation may be about to take place,[55] but it does not mean ovulation will definitely occur. The inner cell mass differentiates to cover the blastocyst. 7. When hyperactivation was blocked in capacitated, acrosome-reacted hamster sperm bound to the zona, they were unable to penetrate it (Stauss et al., 1995). menopause. Ameer MA, Fagan SE, Sosa-Stanley JN, et al. The human female reproductive system is specialized to carry out various functions like gametogenesis, ovulation, fertilization, pregnancy, birth, and child care. Either you can download it on your mobile, laptop or desktop or you can study online. Progesterone levels exceed those of estrogen (estradiol) by a hundred-fold. [20] An enzyme called plasmin breaks up the blood clots in the menstrual fluid, which eases the flow of blood and broken down lining from the uterus. Interestingly, transport of the spheres was greater to the isthmus ipsilateral to the dominant follicle than to the contralateral isthmus. This is in contrast to contractions occurring during menses, which involve all layers of the myometrium. This phenomenon is called implantation which leads to pregnancy. The ruptured parts of the Graafian follicle after ovulation form the yellow body called corpus luteum. Studies of uterine contractions during estrus should be interpreted with caution if coitus did not occur. The average age of menopause in women is 52 years, and it typically occurs between 45 and 55 years of age. Also, sperm from male mice that are null mutants for CatSper1 or CatSper2 genes and cannot hyperactivate also cannot penetrate the zona (Ren et al., 2001; Quill et al., 2003). Little is known about how long sperm spend traversing the cervix or whether sperm are stored there. It is an interesting chapter and includes many important topics. The widest section of the tube, this is where the fertilisation of the ovum with the sperm happens. The main external female genitalia of the female reproductive system consists of the mons pubis, labia majora, labia minora, hymen, and clitoris. Each spermatogonium is diploid in nature and contains 46 chromosomes. The plug may serve to prevent other males from mating with the female. Overall, data of human sperm distribution in the Fallopian tubes of women have not provided a clear picture of the events of sperm transport. Stress, anxiety and eating disorders can cause a fall in GnRH, and a disruption of the menstrual cycle. Sperm is a male reproductive cell that is made up of a head, neck, middle piece, and tail. Sperm recovered at various times in different regions of the Fallopian tube have varied so much in numbers that the data do not permit the construction of a model for the pattern of tubal sperm transport (Williams et al., 1993). It has been proposed that this coagulum serves to hold the sperm at the cervical os (Harper, 1994) and that it protects sperm against the harsh environment of the vagina (Lundwall et al., 2003). The first menstruation is the signal of the beginning of reproductive age in females. Often a woman's normal mood variation is falsely attributed to the menstrual cycle. Your uterus looks like an upside-down pear and sits in your pelvis between your hips. WebThe cervix is part of the female reproductive system.Around 23 centimetres (0.81.2 in) in length, it is the lower narrower part of the uterus continuous above with the broader upper partor bodyof the uterus. [59], If pregnancy does not occur the ovarian and uterine cycles start over again. The secretion of milk takes place by the cells of the alveoli. However, if there is failure of the contraception types below, the pregnancy is more likely to be ectopic. The definitive management of ectopic pregnancy can be medical, surgical, or conservative. The leading symptom of ectopic pregnancy is pain. The major constituents of the fluid are calcium, sodium, chloride, glucose (a sugar), proteins, bicarbonates, and lactic acid. On the other hand, scanning electron microscopy of the human cervix indicates that mucosal grooves forming a preferential pathway for sperm could be present as in the bovine (Figure 2). It consists of three major layers, but the exact Isthmus: The part of your uterus between your corpus and cervix. It secretes large amounts of progesterone hormone which maintains the endometrium. Most people have an anteverted uterus. If implantation does not occur within about two weeks, the corpus luteum degenerates into the corpus albicans, which does not produce hormones, causing a sharp drop in levels of both progesterone and estrogen. A fallopian tube is generally 10-12 cm in length. In addition to assisting sperm in reaching the oocyte, hyperactivation also aids sperm in penetrating the zona pellucida. Original Author(s): Nandhaa Pazhaniappan Last updated: 20th December 2016 Foetal hemoglobin has an X affinity for oxygen than that of the mothers hemoglobin during gestation. If the tubes are blocked or damaged, for example, sperm are unable to reach the egg, or the fertilized egg may be prevented from traveling to the uterus. Although anovulation is not considered a disease, it can be a sign of an underlying condition such as polycystic ovary syndrome. Because sperm are terminally differentiated cells, deprived of an active transcription and translation apparatus, they must survive in the female without benefit of reparative mechanisms available to many other cells. It has reached the blastocyst stage at the time of implantation: this is when pregnancy begins. The secretion of LH and FSH gonadotropins increases gradually in this phase to stimulate follicular development. The mucosal folds increase in height and complexity towards the ovary, thus offering increasingly greater obstacles to the advancement of sperm into and through the ampulla. Thus, sperm must somehow use their limited resources to maintain their fertility in the face of numerous impediments. In these null mutants, both the motility and morphology of the sperm are normal. Weve updated our privacy policy so that we are compliant with changing global privacy regulations and to provide you with insight into the limited ways in which we use your data. Medical management of an ectopic pregnancy is withIM methotrexate. Both cycles can be divided into phases. Sperms are essential for fertilizing a female egg. Human sperm must contend, however briefly, with the acidic pH of vaginal fluid. [9] Meiosis (cell division) remains incomplete in the egg cells until the antral follicle is formed. These are the ducts where the seminiferous tubules open into a series of channels. The narrowness of the lumen is especially apparent in living tissue (Suarez, 1987) and in frozen sections, in which tissue does not shrink as it does during standard preparation of paraffin-embedded sections (Suarez et al., 1997). This is the reproductive cycle that starts from one menstruation till the next one. Often this is in combination with ovarian stimulation of the female partner (Balasch, 2004). (C) Hyperactivated motility of sperm in Fallopian tube. [48], The flow of blood normally serves as a sign that a woman has not become pregnant, but this cannot be taken as certainty, as several factors can cause bleeding during pregnancy. Urethra is a thin muscular tube that originates from the urinary bladder and then passes through the penis to its external opening known as the urethral meatus. Your cervix opens to your vagina. [74], In some women, ovulation features a characteristic pain[d] called mittelschmerz (a German term meaning middle pain). Anatomy, Abdomen and Pelvis, Perineal Body. If a pregnancy cannot be identified on ultrasound scan (but -HCG is positive), this is termed a pregnancy of unknown location. Human Reproduction forms an immensely crucial lesson of class 12 Biology, and you must be thorough with the text to write precise answers during exams. The ovaries are protected by a thin epithelium which encircles the ovarian stroma. It extends from the mons pubis and covers the vaginal opening. Students can easily understand the organs of the reproductive system and the entire process of reproduction from the Class 12 Biology Chapter 3 notes available online. Functional cookies help to perform certain functionalities like sharing the content of the website on social media platforms, collect feedbacks, and other third-party features. The release of an ovum from a mature Graafian follicle is known as ovulation. However, you can remain assured to find exact and required information to score full marks in exams. In these cases, the only route available to the sperm was through the peritoneal cavity. The bovine uterotubal junction is sigmoidal in shape and supported by muscular ligaments that appear capable of increasing the flexure of the curve and thus compressing the lumen (Hook and Hafez, 1968; Hafez and Black, 1969). This process only takes place in the condition when the ovum released by the ovary is not fertilized. In a miscarriage, HCG level would be expected to halve every 48 hours. The hormone estrogen stimulates the uterus lining (endometrium) to thicken to accommodate an embryo should fertilization occur. Leydig cells synthesize and secrete the testicular hormones called androgens. The fertilized egg (called a blastocyte) burrows into the endometrial lining of your uterus (implantation). Transport of sperm through the uterus is likely aided by pro-ovarian contractions of the myometrium. In some women, the hymen can continue even after coitus so it shows that the presence or absence of a hymen is not a reliable indication of virginity or sexual experience. Mucus has been found in the uterotubal junction in humans (Jansen, 1980), as well as in rabbits (Jansen, 1978; Jansen and Bajpai, 1982), pigs (Suarez et al., 1990) and dairy cattle (Suarez et al., 1997, 1990). The mechanism for preventing rises of cytoplasmic Ca2+ in sperm are not known, but one suggestion is that catalase, which has been detected in the bovine tube, serves to protect against peroxidative damage to the sperm membranes, perhaps preventing inward leakage of Ca2+ (Lapointe et al., 1998). The high fructose content gives nutrient energy to the spermatozoa. This can provide the force necessary for overcoming the attraction between sperm and epithelium (Ho and Suarez, 2001; Suarez and Ho, 2003). Around day fourteen, an egg is usually released from the ovary. At the time of fertilization, the sperm makes changes in the zona pellucida layer of the ovum to block the entry of other sperms. The ova or oocytes are the egg cells produced by the ovaries that are subsequently transferred to the fallopian tube, then fertilised by a sperm. Hymen is a thin membrane that surrounds the opening of the vagina. The resulting chimeric XY/XY males produced a mixture of sperm, about half of which were mutant, as identified by the presence of the fluorescent acrosomes. The average age of menopause is between 45-50 years and it varies from person to person. The mature egg has a diameter of about 0.1mm (0.0039in),[29] and is the largest human cell. [60], Although a normal and natural process,[65] some women experience premenstrual syndrome with symptoms that may include acne, tender breasts, and tiredness. It is introduced during the embryonic development stage. Entrapment and storage of sperm in the initial segment of the tube may serve to prevent polyspermic fertilization by allowing only a few sperm at a time to reach the oocyte in the ampulla. The primary oocyte increases in size and completes its first meiotic division. Theoretically, sperm could be released from the reservoir either through loss of binding sites on the epithelium or by alterations in the sperm themselves. In humans, semen is deposited at the external os of the cervix so that sperm can quickly move out of the vagina (Sobrero and MacLeod, 1962).