Reproductive Organs in Mammals

SRY gene needed for

. Expression of the SRY (sex-determining region of the Y chromosome) gene in XY embryos causes the bipotential gonad of males to become the testis, which secretes several hormones, including testosterone, insulin-like growth factor (IGF), and Müllerian inhibiting substance (MIS). Testosterone promotes Wolffian duct differentiation into the male reproductive tract through the formation of the epididymis, vas deferens and seminal vesicles, and MIS eliminates the Müllerian ducts (Figures 6 and 7). Absence of these signals leads to preservation of the Müllerian ducts and the degeneration of the Wolffian ducts. Without MIS, the Müllerian ducts will continue to develop into the female internal genitalia

Leydig cell

A cell in the testes that produces testosterone.

BIG DIFFERENCE in male/female meiosis

A spermatocyte produces four mature sperm, while an oocyte produces only one mature ovum.

seminiferous tubule

A tightly coiled tube of tissue that exits in twos or threes within the testes where the sperm develop and testosterone is produced.

Fertilization and early development of the zygote.

After ovulation, the ovum is captured by the infundibulum with its finger-like fimbriae. Fertilization occurs as the ovum travels through the fallopian tube, often at a site called the ampulla. The fertilized ovum, or zygote, begins development as it travels to the uterus, where it eventually implants into the uterine wall.

oviduct

Channel from the ovary to the uterus through which the egg passes. also known as fallopian tubes

ovulation and tubes

During ovulation, an ovum is released into the abdominal cavity, near the opening, or infundibulum, of the oviduct, or fallopian tube. The ovum is captured by the infundibulum with its finger-like fimbriae. The ovum moves through the fallopian tube, propelled by muscular contractions and the movement of cilia lining the tube. Fertilization usually occurs as the ovum travels through the fallopian tube on its way to eventual implantation in the uterus. The uterus functions to support the embryo until birth, by providing an environment for implantation, supporting the fetus and placenta during gestation, and delivering the fetus via muscular contractions

ovulation

During ovulation, the mature follicle ruptures, releasing the mature ovum through the wall of the ovary. After ovulation, the granulosa and thecal cells of the now empty follicle form the corpus luteum, which produces estrogens and progesterone. Estrogens and progesterone act on the female reproductive tract to prepare it for the subsequent steps of fertilization, embryo development, implantation and pregnancy. The corpus luteum degenerates into the corpus albicans if fertilization does not take place.

Oogenesis differs from spermatogenesi

First, the male continually produces sperm during his reproductive years, but a femalealready has established all the oocytes she will ever produce during her embryonic development. Unlike sperm, oocytes mature individually and not at a constant rate. There is a resting period between the maturation of the ova, which depends on the species. A spermatocyte produces four mature sperm, while an oocyte produces only one mature ovum. The other products of oogenesis are polar bodies, which are haploid, but not used. This serves to preserve the larger part of the cytoplasm and organelles into the maturing oocyte.

follicle

Granulosa cells which surround the oocytes.

scrotum function? internal or external?

In terrestrial mammals, the testes are often held outside of the body in a pouch of loose skin called the scrotum. However, many mammals retain their testes internally. Why would the testes be held outside the body in some mammals? hypotheses claimed that a temperature lower than that of the core body is necessary to avoid a disruption of spermatogenesis. In humans, the body's internal temperature is too high for the production of sperm, and the scrotum is about 2 degrees Celsius lower than normal body temperature

Wolffian and Müllerian ducts

Moreover, the genital tracts of embryos of either sex are physically alike, possessing both Wolffian and Müllerian ducts. Wolffian and Müllerian ducts differentiate into male or female reproductive organs, respectively, according to the hormonal status of the fetus. In females, the bipotential gonad becomes the ovary. The Müllerian ducts differentiate into the female reproductive tract. Expression of the SRY (sex-determining region of the Y chromosome) gene in XY embryos causes the bipotential gonad of males to become the testis, which secretes several hormones, including testosterone, insulin-like growth factor (IGF), and Müllerian inhibiting substance (MIS). Testosterone promotes Wolffian duct differentiation into the male reproductive tract through the formation of the epididymis, vas deferens and seminal vesicles, and MIS eliminates the Müllerian ducts (Figures 6 and 7). Absence of these signals leads to preservation of the Müllerian ducts and the degeneration of the Wolffian ducts. Without MIS, the Müllerian ducts will continue to develop into the female internal genitalia

female internal reproduction structures

Most female mammals have two ovaries. The ovaries are attached to the abdominal cavity by connective tissue. In most animals, the female receptacle for the penis is called the vagina. A narrow opening called the cervix connects the vagina to the uterus. Sperm deposited in the vagina moves through the cervix and into the uterus.

Oogenesis starts when

Oogenesis begins before birth, but pauses midway. When a woman is born, all of her oocytes (about 2 million) are suspended in prophase of meiosis I; however, most will never be ovulated. In fact, most of the oocytes in a woman's ovary will die in a process called atresia. Hormonal stimulation is necessary for an oocyte to complete oogenesis. and in a woman's lifetime about 400 ova will be ovulated. During ovulation, the mature follicle ruptures, releasing the mature ovum through the wall of the ovary. After ovulation, the granulosa and thecal cells of the now empty follicle form the corpus luteum, which produces estrogens and progesterone. Estrogens and progesterone act on the female reproductive tract to prepare it for the subsequent steps of fertilization, embryo development, implantation and pregnancy. The corpus luteum degenerates into the corpus albicans if fertilization does not take place.

Oogenesis

Oogenesis, or the process of producing a mature ovum, occurs in the ovary. At birth, females have already established all the oocytes (precursor cells to ova) that they will ever produce. During oogenesis, immature diploid cells called oogonia develop into mature ova in one of the ovaries (Figure 5). Once an oogonium commits to oogenesis, it is called a primary oocyte. The primary oocyte undergoes meiosis I to produce a secondary oocyte and a polar body, which eventually degenerates and is resorbed. All of the oocytes are surrounded by granulosa cells, forming a primary follicle (supports oocyte and converts estrogen). Thecal cells are recruited to the follicles at the secondary follicle stage and produce androgens that the granulosa cells convert into estrogens. Upon fertilization, the secondary oocyte completes meiosis II to produce a second polar body and a haploid pronucleus, which is then united with the male pronucleus provided by the sperm during fertilization.

male internal reproduction structures

Sperm travel from each testis to the epididymis for further maturation and, finally, to the vas deferens. The two vas deferens join to form a short ejaculatory duct. The ejaculatory duct in turn joins to the urethra, the tube that carries urine from the bladder to the outside of the body via the penis. This same path also carries semen during ejaculation.

Briefly describe the process of spermatogenesis in relation to meiosis.

Spermatogenesis is the process of sperm formation.The most immature cells in the testes are the diploid spermatogonia. These cells become primary spermatocytes prior to meiosis. A primary spermatocyte undergoes meiosis I to form two secondary spermatocytes. These two secondary spermatocytes undergo meiosis II to form four haploid spermatids.

male and female gamates

The male gametes are sperm and the female gamete is an ovum (pl. ova), or egg. Some animals that are hermaphroditic produce both ova and sperm in organs called ovotestes. Animal reproductive systems are adapted to carry out the manufacture and storage of gametes, to enable the physical act of mating to take place, and to allow for protection of the developing embryo in some species

spermatogenesis

The process of sperm production and development, called spermatogenesis, occurs in the testes . A testis is made up of highly coiled tubes called seminiferous tubules where the sperm develop and are supported by accessory cells such as the Sertoli cells, and the Leydig cells, which produce testosterone. Spermatogenesis begins at puberty and occurs continuously until very old age. After sperm leave the seminiferous tubules, they enter the epididymis where they are stored until they reach their final stage of maturation. Spermatogenesis is the process of sperm formation.The most immature cells in the testes are the diploid spermatogonia. These cells become primary spermatocytes prior to meiosis. A primary spermatocyte undergoes meiosis I to form two secondary spermatocytes. These two secondary spermatocytes undergo meiosis II to form four haploid spermatids.

vas deferens

Tube from each testis to the ejaculatory duct through which the sperm swim.

Gamete Production

development of a vertebrate embryo, specialized cells called germ cells migrate from the endoderm (developing gut) to the site where the reproductive organs, or gonads, are forming. The germ cells are then incorporated into the developing gonads, where they will give rise to gametes. Damage to the germ cells may result in defective reproduction. The male gonads are the testes, which produce sperm. The female gonads are the ovaries, which produce ova.

corpus luteum

formed by the granulosa and thecal cells of the empty follicle.Produces progesterone (estrogen and progesterone);

A primary spermatocyte undergoes ___ to produce two secondary spermatocytes.

meiosis I Correct This answer is correct. A spermatocyte undergoes meiosis I to produce two secondary spermatocytes.

The entire process of oogenesis produces which of the following?

one ovum and two polar bodies Correct This answer is correct. The first meiotic division of a primary oocyte produces a secondary oocyte and one polar body. The secondary oocyte undergoes meiosis II during ovulation to produce one ovum and a second polar body.