WAn antral follicle, also known as Graafian follicle and tertiary follicle, is an ovarian follicle during a certain latter stage of folliculogenesis.
WArtificial insemination (AI) is the deliberate introduction of sperm into a female's cervix or uterine cavity for the purpose of achieving a pregnancy through in vivo fertilization by means other than sexual intercourse. It is a fertility treatment for humans, and is common practice in animal breeding, including dairy cattle and pigs.
WThe baculum is a bone found in the penis of many placental mammals. It is absent in the human penis, but present in the penises of other primates, such as the gorilla and chimpanzee. The os penis arises from primordial cells within soft tissues of the penis, and its formation is largely under the influence of androgens. The bone is located above the male urethra, and it aids sexual reproduction by maintaining sufficient stiffness during sexual penetration. The homologue to the baculum in female mammals is known as the baubellum or os clitoridis, a bone in the clitoris.
WDomestic sheep reproduce sexually much like other mammals, and their reproductive strategy is furthermore very similar to other domestic herd animals. A flock of sheep is generally mated by a single ram, which has either been chosen by a farmer or has established dominance through physical contest with other rams. Most sheep have a breeding season (tupping) in the autumn, though some are able to breed year-round.
WFrozen bovine semen is a method of preserving bovine semen for future artificial insemination, even after the death of the donor.
WThe spotted hyena, also known as the laughing hyena, is a hyena species, currently classed as the sole extant member of the genus Crocuta, native to sub-Saharan Africa. It is listed as being of least concern by the IUCN on account of its widespread range and large numbers estimated between 27,000 and 47,000 individuals. The species is, however, experiencing declines outside of protected areas due to habitat loss and poaching. The species may have originated in Asia, and once ranged throughout Europe for at least one million years until the end of the Late Pleistocene. The spotted hyena is the largest known member of the Hyaenidae, and is further physically distinguished from other species by its vaguely bear-like build, its rounded ears, its less prominent mane, its spotted pelt, its more dual purposed dentition, its fewer nipples and the presence of a pseudo-penis in the female. It is the only mammalian species to lack an external vaginal opening.
WInduced ovulation is when a female animal ovulates due to an externally-derived stimulus during, or just prior, to mating, rather than ovulating cyclically or spontaneously. Stimuli causing induced ovulation include the physical act of coitus or mechanical stimulation simulating this, sperm and pheromones.
WLactation describes the secretion of milk from the mammary glands and the period of time that a mother lactates to feed her young. The process naturally occurs with all post-pregnancy female mammals, although it predates mammals. In humans the process of feeding milk is also called breastfeeding or nursing. Newborn infants often produce some milk from their own breast tissue, known colloquially as witch's milk.
WIn human reproduction, a live birth occurs when a fetus, whatever its gestational age, exits the maternal body and subsequently shows any sign of life, such as voluntary movement, heartbeat, or pulsation of the umbilical cord, for however brief a time and regardless of whether the umbilical cord or placenta are intact.
WMost mammals are viviparous, giving birth to live young. However, the five species of monotreme, the platypuses and the echidnas, lay eggs. The monotremes have a sex determination system different from that of most other mammals. In particular, the sex chromosomes of a platypus are more like those of a chicken than those of a therian mammal.
WMaternal recognition of pregnancy is a crucial aspect of carrying a pregnancy to full term. Without maternal recognition to maintain pregnancy, the initial messengers which stop luteolysis and promote foetal implantation, growth and uterine development finish with nothing to replace them and the pregnancy is lost.
WA mating plug, also known as a copulation plug, sperm plug, vaginal plug, sement or sphragis, is gelatinous secretion used in the mating of some species. It is deposited by a male into a female genital tract, such as the vagina, and later hardens into a plug or glues the tract together. While females can expel the plugs afterwards, the male's sperm still gets a time advantage in getting to the egg, which is often the deciding factor in fertilization.
WMonochorionic twins are monozygotic (identical) twins that share the same placenta. If the placenta is shared by more than two twins, these are monochorionic multiples. Monochorionic twins occur in 0.3% of all pregnancies. Seventy-five percent of monozygotic twin pregnancies are monochorionic; the remaining 25% are dichorionic diamniotic. If the placenta divides, this takes place before the third day after fertilization.
WOvarian reserve is a term that is used to determine the capacity of the ovary to provide egg cells that are capable of fertilization resulting in a healthy and successful pregnancy. With advanced maternal age the number of egg cell that can be successfully recruited for a possible pregnancy declines, constituting a major factor in the inverse correlation between age and female fertility.
WPanda pornography refers generally to movies depicting mating pandas, intended to promote sexual arousal in captive giant pandas. Under zoo conditions, the animals have, in general, proven unenthusiastic about mating, placing their species in danger of extinction.
WThe rut is the mating season of certain mammals, which includes ruminants such as deer, sheep, camels, goats, pronghorns, bison, giraffes and antelopes, and extends to others such as skunks and elephants. The rut is characterized in males by an increase in testosterone, exaggerated sexual dimorphisms and increased aggression and interest in females. The males of the species may mark themselves with mud, undergo physiological changes or perform characteristic displays in order to make themselves more visually appealing to the females. Males also use olfaction to entice females to mate using secretions from glands and soaking in their own urine.
WSperm precedence, also known as sperm predominance, is tendency of a female who has been bred by multiple males to give birth to their offspring in unequal proportions. Sperm precedence is an important factor in the sperm competition.
WTwins are two offspring produced by the same pregnancy. Twins can be either monozygotic ('identical'), meaning that they develop from one zygote, which splits and forms two embryos, or dizygotic, meaning that each twin develops from a separate egg and each egg is fertilized by its own sperm cell.
WThe XY sex-determination system is a sex-determination system used to classify many mammals, including humans, some insects (Drosophila), some snakes, some fish (guppies), and some plants. In this system, the sex of an individual is determined by a pair of sex chromosomes. Females typically have two of the same kind of sex chromosome (XX), and are called the homogametic sex. Males typically have two different kinds of sex chromosomes (XY), and are called the heterogametic sex.