Artlabeling Activity Internal Female Reproductive Organs 1 of 2 2 of 2

Weichert, Charles K. College of Arts and Sciences, Academy of Cincinnati, Cincinnati, Ohio.

Chang, M. C. Worcester Foundation for Experimental Biology, Shrewsbury, Massachusetts.

Harper, Michael J. One thousand. Reproductive Biology Division, Center for Inquiry, Section of Obstetrics and Gynecology, University of Texas-Wellness Science Center, San Antonio, Texas.

Hunter, R. H. F. School of Agronomics, Academy of Edinburgh, Edinburgh, United kingdom of great britain and northern ireland.

The anatomical structures concerned with the production of sex cells (gametes) and perpetuation of the species. The reproductive system consists of diverse trunk organs and glands that ensure the production of new individuals (that is, reproduction). In vertebrates, the reproductive role constitutes the only physiological function that necessitates the existence of ii morphologically different kinds of individuals in each animal species—the males and the females (sexual dimorphism). The purpose of the reproductive office is fertilization, that is, the fusion of a male sex jail cell and a female sex prison cell produced past two distinct individuals. In each sex activity, the reproductive system comprises a sexual activity gland or gonad, which produces sex cells (Fig. 1), or gametes, and ducts, which let the passage of the gametes. In some animals, such equally mammals, copulatory organs permit the male person germ cells to exist introduced into the female ducts, and fertilization is internal; yet, in many vertebrates, such every bit anuran amphibians and many fishes, no copulatory organ exists, and fertilization is external. Come across also: Brute reproduction; Copulatory organ; Fertilization (animate being); Gametogenesis; Gland; Reproductive behavior; Reproductive organization disorders; Sexual dimorphism

Fig. 1 Colored scanning electron micrograph (SEM) of a human sperm cell in a Fallopian tube. In the reproductive system of the female person, fertilization may occur, in which the sperm jail cell fuses with an egg cell. (Credit: Steve Gschmeissner/Science Photo Library/Alamy Stock Photo)

Anatomy

For both sexes, many of the organs of the reproductive system develop from similar embryonic tissue. Nevertheless, at later stages of evolution, specific changes occur that differentiate the female reproductive system (Fig. ii) and the male reproductive organization (Fig. iii). See also: Embryology

Fig. 2 The female reproductive system in humans. (Copyright © McGraw-Hill Education)

Fig. 3 The male person reproductive system in humans. (Copyright © McGraw-Hill Education)

Egg cells, or ova, and sperm cells, or spermatozoa, are formed in the primary reproductive organs, which are collectively known as gonads—those of the male person are called testes, whereas those of the female are called ovaries (Fig. four). Besides giving ascension to reproductive cells, both ovaries and testes give off endocrine secretions, or sex hormones, which pass into the blood or lymphatic streams and are carried to all parts of the torso, where they bring about profound effects. The gonads are paired structures; however, in some forms, what appears to be an unpaired gonad is the outcome of fusion of paired structures or of unilateral degeneration. See too: Endocrinology; Hormone; Oogenesis; Ovary; Ovum; Sperm cell; Spermatogenesis; Testis

Fig. 4 Section of a portion of rat ovary cortex, showing ovarian follicles in various stages of development, with the youngest beingness near the surface of the ovary. (Copyright © C. K. Weichert/McGraw-Loma Educational activity)

The reproductive elements formed in the gonads must be able to exist transported. In most vertebrates, ducts are utilized for this purpose. These ducts, together with the structures that serve to bring the gametes of both sexes together, are known as sex organs. The structures used to ship the reproductive cells in the male are known as deferent ducts [ductus (vas) deferens] and those of the female person are known as oviducts. In a few forms, no ducts are nowadays in either sexual practice, and eggs and sperm escape from the body cavity through genital or abdominal pores.

Oviducts, except in teleosts and a few other fishes, are modifications of Müllerian ducts formed early during embryonic development. In all female person mammals, each differentiates into an anterior, nondistensible Fallopian tube and a posterior, expanded uterus. In all female mammals, except monotremes, the uterus leads to a last vagina, which serves for the reception of the penis of the male during copulation. The lower part, or neck, of the uterus is commonly telescoped into the vagina to a slight caste. This portion is referred to equally the cervix. See besides: Fallopian tube; Penis; Uterus

In most vertebrates, the reproductive ducts in both sexes open posteriorly into the cloaca. In some, though, modifications of the cloacal region occur and the ducts open up separately to the outside or, in the male, join the excretory ducts to emerge past a common orifice.

The sexual activity of an individual is dependent on the chromosomes received from both parents at the time that the egg is fertilized. However, the balance between maleness and femaleness is a delicate 1 because environmental factors may presume an influential part in sexual development, and hormonal secretions may change the extent to which various structures and even behavioral characteristics develop and are maintained. See too: Chromosome; Sexual practice conclusion

Physiology

The physiological procedure by which a living being gives ascent to another of its kind is considered one of the outstanding characteristics of plants and animals. It is one of the two corking drives of all animals: self-preservation and species perpetuation. In contrast to other physiological processes, reproduction in vertebrates can exist achieved only by participation of ii individuals—the male person and the female person (Fig. five). Each produces germ cells called gametes. The male produces spermatozoa and the female person produces ova, which carry the biochemical information arranged as genes in the chromosomes for the transmission of inherited characters. No matter how discrepant the pairing gametes may be in size and in class within a species, they contribute the same number of chromosomes. Although reproductive devices are quite different from one species to another, all serve i end, that is, the bringing together of the spermatozoon and the ovum, with each containing one-half the number of chromosomes of the parent cells. After the matrimony of the chromosomes at fertilization, the newly constituted embryo possesses the proper number of chromosomes of its kind and so divides, differentiates, grows, and develops into an individual either outside the mother (oviparity) or within the female parent (viviparity). The obvious advantage in bisexual reproduction lies in the fact that young produced from the mingled genes of two bequeathed lines will non exist a direct re-create of either parent, but will represent different combinations of ancestral traits with cracking potential for the survival of the fittest. Reproduction is facilitated or inhibited past environmental and nutritional factors, as well equally by all other physiological activities, but it is controlled predominantly by the endocrine system and mediated at least in part by the nervous system. See also: Endocrine system (vertebrate); Nervous organization (vertebrate)

Fig. 5 Homologies in the development of the female genital tract (left) and male genital tract (right) of mammals. The gonads are shown on the inner side of the mesonephroi, and the ducts are shown on their outer border. (Credit: Based on an original drawing by Alfred Jost)

Breeding season

The season when animals perform their overt reproductive functions is known as the breeding season. This sexual periodicity is a general phenomenon common to plants and animals. In general, sexual periodicity is predominant in lower vertebrates, only all birds and wild mammals are seasonal breeders. Equally nutritional and ecology conditions improve, the reproductive season is not so restricted; for example, cattle, the domestic rabbit, and humans all illustrate this fact, although their fertility is higher in spring than in wintertime. Males of many mammalian species are capable of sperm production and copulation at any fourth dimension and rarely experience a true sexual catamenia, such as rut in the deer. In mice and rats, the testes do not descend to the scrotum until puberty; in sure other rodents, they descend but during the convenance season. About vertebrates breed only in jump or summer at the time when food, temperature, and light are optimal; they are so in the best physiological status for reproduction. Others, for example, sheep, brood at a time that allows parturition to occur at the flavour of year most suitable for successful survival of the young.

Estrous and menstrual cycles

The cyclic changes of reproductive activities in mammalian females are known as estrous or menstrual cycles (run across table). Most mammalian females accept males merely at estrus (heat). Estrus in mammals can occur several times in one breeding season; the mare, ewe, and rat come up to rut every 21, 16, and v days, respectively, if breeding does not have place. This condition is called polyestrus. The bitch is monestrous; she has merely 1 heat, or rut, to the convenance season and, if not served then, she does non come up into heat once again for a prolonged interval (iv–6 months according to dissimilar breeds). In monestrous and seasonally polyestrous species, the period of sexual quiescence betwixt seasons is called anestrus. See also: Oestrus

Table 1 - Average length of the ovulatory bicycle of some mammals

Animal	Length
Chimpanzee	37 days
Cow	21 days
Republic of guinea pig	16 days
Horse	21 days
Human	28 days
Macaque monkey	24–26 days
Mouse	5 days
Opossum	28 days
Sus scrofa	20–22 days
Rat	5 days
Sheep	16 or 17 days

The reproductive cycle of the female in the primate and human is well marked by menstruation, that is, the period of blood period from the vagina. Menstruation does non represent to estrus, but occurs between the periods of ovulation at the time that the corpus luteum declines precipitously. As a event of the plummet of the superficial capillaries in the endometrium, claret is extravasated in quantity and virtually 2-thirds of the endometrium is desquamated, or shed. Later on menstruation, there is a period in which the uterus is replenished under the influence of estrogens past the growth of the epithelium and its capillaries. This is known as the proliferative stage and is equivalent to proestrus and estrus in other mammals. See also: Menstruation

Mating

Mating, likewise called copulation or coitus, is the synchronized bodily activity of the two sexes that enables them to deposit their gametes in shut contact. It is essential for successful fertilization because the sperm and ovum have a very limited life span.

The logistics of sperm transport to the site of fertilization in the oviduct present many interesting features in mammals, merely information technology is important to distinguish between passive send of sperm cells in the female genital tract and sperm migration, which clearly attributes significance to the intrinsic move of the jail cell. Viable spermatozoa are actively motile; moreover, although myometrial (uterine) contractions play a major role in sperm transport through the uterus, progressive movement does contribute to migration into and within the oviducts. Even though a specific attractant substance for spermatozoa has not yet been demonstrated to be released from mammalian eggs or their investments, some form of chemotaxis may contribute to the last phase of sperm transport and orientation toward the egg surface.

Fertilization is a procedure that begins with penetration of the ovum surface layer (zona pellucida) and bounden to the vitelline membrane by the fully matured spermatozoon, followed by incorporation of the spermatozoon into the ovum cytoplasm and activation of the ovum. Fertilization takes place in the oviducts of mammals, and the fertilized eggs or embryos do not descend to the uterus for some three to four days in near species. During this interval, the embryo undergoes a series of mitotic divisions until it comprises a sphere of 8 or 16 cells and is termed a morula. Formation of a blastocyst occurs when the cells of the morula rearrange themselves effectually a central, fluid-filled crenel, called the blastocoele. As the blastocyst develops within the uterine environment, information technology sheds its protective glaze, the zona pellucida, and undergoes further differentiation earlier developing an intimate association with the endometrium, which represents the commencement of implantation or nidation. Early development of embryos in most species is largely under the control of the maternal genome, with sequential activation and utilization of oocyte components. Come across also: Cleavage (developmental biological science); Mitosis

Association of the embryo with the uterine epithelium, past either superficial zipper or specific embedding in or beneath the endometrium, leads in due course to the germination of a placenta and complete dependence of the differentiating embryo upon metabolic support from the mother. Implantation and placentation showroom a multifariousness of forms; however, in all instances, the hormonal status of the mother is of great importance in determining whether or not implantation tin continue. Run across too: Placentation; Pregnancy

Endocrine function in reproduction

The endocrine glands secrete sure substances (hormones) that are necessary for growth, metabolism, reproduction, response to stress, and various other physiological processes. The endocrine glands nigh concerned with the process of reproduction are the pituitary and the gonads. Other contributions to the proper functioning of the reproductive system are provided by the thyroid, pineal, and adrenal glands. The hypothalamus is also an of import organ for regulating reproduction. See also: Pituitary gland

The germination of gametes (spermatogenesis and oogenesis) is controlled past anterior pituitary hormones. The differentiation of male person and female reproductive tracts is influenced, and mating beliefs and estrous cycles are controlled, past male or female hormones. The occurrence of the breeding season is mainly dependent on the action of the inductive lobe of the pituitary, which is influenced through the nervous system by external factors, such every bit calorie-free and temperature. The ratio of light to nighttime during the daily wheel affects the secretion of melatonin by the pineal gland in the encephalon. Melatonin tin exist either stimulatory or inhibitory for reproductive activity in a wide diverseness of mammals, specially those with defined periods of estrus and anestrus (for instance, sheep and many rodents). Its role in human reproduction is uncertain, just it can inhibit ovulation in sure circumstances. The transportation of ova from the ovary to the Fallopian tube and their subsequent transportation, development, and implantation in the uterus are controlled by a balanced ratio betwixt estrogen and progesterone. Furthermore, information technology is known that estrogens, androgens, and progesterone can accept the effect of inhibiting the production or the secretion (or both) of gonadotropic hormones, permitting the circadian changes of reproductive action amongst different animals. See also: Androgens; Estrogen; Melatonin; Pineal gland; Progesterone

Mammary glands are essential for the nursing of young. Their growth, differentiation, and secretion of milk, and in fact the whole process of lactation, are controlled past pituitary hormones besides equally past estrogen and progesterone. Other glands and physiological activities also influence lactation, although this is largely via the trophic back up of other pituitary hormones. Run across also: Lactation; Mammary gland

M. C. Chang

Michael J. Chiliad. Harper

R. H. F. Hunter

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