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Veterinary A & P
The Reproductive System & Pregnancy, Development, and Lactation
Question | Answer |
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Gametes | a mature haploid male or female germ cell which is able to unite with another of the opposite sex in sexual reproduction to form a zygote. |
meiosis | a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes |
diploid chromosome number | the number of chromosomes required for two complete copies of the organism's genome (the entirety of its genetic information). |
haploid chromosome number | the number of chromosomes that are half the diploid number of chromosomes. Haploid animals are very rare, as most organisms have diploid cells. It is defined as a cell having only a single set of chromosomes. |
chromosomes | a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes. |
mitosis | a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth. |
spermatogenesis | the production or development of mature spermatozoa. |
seminiferous tubule | Are the site of the germination, maturation, and transportation of the sperm cells within the male testes. They are made up of columnar Sertoli cells surrounded by spermatogenic cells on the epithelial interior and stem cells exteriorly. |
oogenesis | the production or development of an ovum. |
ovarian follicle | In the ovaries of the female reproductive system, an this is a fluid-filled sac that contains an immature egg, or oocyte. They are found in the ovaries. During ovulation, a mature egg is released from a this. |
oocyte | a cell in an ovary which may undergo meiotic division to form an ovum. |
polar body | each of the small cells which bud off from an oocyte at the two meiotic divisions and do not develop into ova. |
gonads | an organ that produces gametes; a testis or ovary. |
scrotum | a pouch of skin containing the testicles. |
interstitial cells | refers to any cell that lies in the spaces between the functional cells of a tissue. Examples: cells present in the male testes responsible for the production of androgen (male sex hormone). A portion of the stroma of ovary. |
androgens | a male sex hormone, such as testosterone. |
spermatozoa | the mature motile male sex cell of an animal, by which the ovum is fertilized, typically having a compact head, neck, and one or more long flagella for swimming. |
acrosome | an organelle that develops over the anterior half of the head in the spermatozoa (sperm cells) of many animals including humans. It is a cap-like structure derived from the Golgi apparatus. |
gubernaculum | a part or structure that serves as a guide especially : a fibrous cord that connects the fetal testis with the bottom of the scrotum and by failing to elongate in proportion to the rest of the fetus causes the descent of the testis. |
inguinal rings | either of two openings in the abdominal muscles on each side of the body that are the inlet and outlet of the inguinal canal, give passage to the spermatic cord in the male and the round ligament in the female, and are a frequent site of hernia formation |
cremaster muscle | a thin muscle consisting of loops of fibers derived from the internal oblique muscle and descending upon the spermatic cord to surround and suspend the testicle |
spermatic cord | the cord-like structure in males formed by the vas deferens (ductus deferens) and surrounding tissue that runs from the deep inguinal ring down to each testicle. Its serosal covering, the tunica vaginalis, is an extension of the peritoneum. |
pampiniform plexus | the venous network of approximately 10 veins draining the testis and epididymis. The network surrounds the testicular artery in the spermatic cord and lies anterior to the ductus deferens |
vaginal tunic | The mesothelium that surrounds the testes and the epididymis continuous with the parietal peritoneum through the inguinal canal and into the scrotum |
orchiectomy | (also named orchidectomy, and sometimes shortened as orchi) is a surgical procedure in which one or both testicles are removed (bilateral orchiectomy). |
ligated | tied off or tie up or otherwise close off (an artery or vessel). |
seminiferous tubules | the site of the germination, maturation, and transportation of the sperm cells within the male testes. They are made up of columnar Sertoli cells surrounded by spermatogenic cells on the epithelial interior and stem cells exteriorly. |
rete testis | is an anastomosing network of delicate tubules located in the hilum of the testicle (mediastinum testis) that carries sperm from the seminiferous tubules to the efferent ducts. It is the counterpart of the rete ovarii in females. |
interstitial cells | any cell that lies in the spaces between the functional cells of a tissue. Example: endocrine cells present in the male testes responsible for the production of androgen (male sex hormone). A portion of the stroma of ovary |
sertoli cells | the somatic cells of the testis that are essential for testis formation and spermatogenesis. They facilitate the progression of germ cells to spermatozoa via direct contact and by controlling the environment within the seminiferous tubules. |
duct of the testes | ductus deferens or vas deferens a fibromuscular tube that is a continuation of the epididymis and is an excretory duct of the testis. It serves to transport sperms cells from the respective epididymis to the ipsilateral ejaculatory duct. |
epididymis | a highly convoluted duct behind the testis, along which sperm passes to the vas deferens. |
efferent ducts of the testes | (or efferent ductules or ductuli efferentes or ductus efferentes or vasa efferentia) connect the rete testis with the initial section of the epididymis. |
vas deferens | the duct which conveys sperm from the testicle to the urethra. |
seminal vesicles | each of a pair of glands which open into the vas deferens near to its junction with the urethra and secrete many of the components of semen |
ejaculation | the action of ejecting semen from the body. |
ampulla | a cavity or the dilated end of a duct (shaped like a Roman ampulla) |
urethra | the duct by which urine is conveyed out of the body from the bladder, and which in male vertebrates also conveys semen |
prostate gland | a male reproductive organ whose main function is to secrete its respective fluid, one of the components of semen. The muscles of this gland also help propel the seminal fluid into the urethra during ejaculation |
bulbourethral gland | also called Cowper's Gland, either of two pea-shaped glands in the male, located beneath the prostate gland at the beginning of the internal portion of the penis; they add fluids to semen during the process of ejaculation |
penis | the male sex organ, reaching its full size during puberty. In addition to its sexual function, it acts as a conduit for urine to leave the body. |
erectile tissue | any tissue that is capable of stiffening or engorging with blood. During sexual arousal, this sexual tissue experiences increased blood flow and becomes engorged with blood, enlargening and/or stiffening. |
glans of the penis | can be described as the rounded head (or tip) of the penis. Located in the middle of the glans penis is the opening of the urethra, the tube through which semen and urine exits the body. "penis's 'head'" Latin word for 'acorn. |
prepuce | forms a complete sheath around the cranial end of the penis. In the cat it has an orifice with thick edges and is directed caudally and located under the scrotum. Purulent discharge from the prepuce occurs frequently in intact male dogs. |
os penis | baculum (also penis bone, penile bone) is a bone found in the penis of many placental mammals |
suspensory ligament of the ovary | continuous tissue that connects the ovary to the wall of the pelvis. In the anterior region, the suspensory ligament is attached to the wall of the pelvis via a continuous tissue called peritoneum |
ovaries | the female gonads — the primary female reproductive organs. These glands have three important functions: they secrete hormones, they protect the eggs a female is born with and they release eggs for possible fertilization. |
oogenesis | ovogenesis is the differentiation of the ovum (egg cell) into a cell competent to further develop when fertilized. It is developed from the primary oocyte by maturation. It is initiated in the embryonic stage. |
estrogens | are steroids that are secreted in both males and females by the adrenal cortex. In females by the ovary (main source) and placenta. Natural estrogens include estradiol, estrone, and estriol. |
progestins | Progesterone is a hormone produced by the ovaries and placenta that helps to maintain pregnancy |
corpus luteum | Latin for "yellow body". The structure formed during luteinisation of the follicle after ovulation. It is actually only yellow in cows. In other domestic species it is red. The yellow coloration is due to the pigment lutein. |
ovulation | occurs at the ovary surface and is described as the process in which an oocyte is released from the follicle. |
uniparous | An animal that only gives birth to one baby at a time: elephant |
multiparous | Having given birth two or more times or giving birth to more than one offspring at a time. |
granulosa cells | or follicular cell is a somatic cell of the sex cord that is closely associated with the developing female gamete (called an oocyte or egg) in the ovary of mammals. |
antrum | A general term for a nearly closed cavity or chamber. |
cumulus oophorus | is a cluster of cells (called cumulus cells) that surround the oocyte both in the ovarian follicle and after ovulation. In the antral follicle, it may be regarded as an extension of the membrana granulosa. |
corona radiata | the innermost layer of the cells of the cumulus oophorus and is directly adjacent to the zona pellucida, the inner protective glycoprotein layer of the ovum. Its main purpose in many animals is to supply vital proteins to the cell. |
ovulation | is the release of an egg from an ovary. After the egg is released, it travels down the Fallopian tube, where fertilization by a sperm cell may occur. |
oviduct | the tube that links the ovary to the uterus and which the ovulated oocyte travels down to become fertilized by sperm present in the female tract. It is also referred to as the Fallopian tube, Uterine tube or Ovarian tube. |
ovum | egg cells are also known as ova (singular ovum, from the Latin word ovum meaning egg or egg cell). The term ovule in animals is used for the young ovum of an animal. In vertebrates, ova are produced by female gonads (sexual glands) called ovaries. |
corpus hemorrhagicum | "bleeding corpus luteum" is a temporary structure formed immediately after ovulation from the ovarian follicle as it collapses and is filled with blood that quickly clots |
fimbriae | are the finger-like projections located at the ends of the fallopian tubes, closest to the ovaries. The majority of them do not touch the ovary: they hover very close. Activated by hormones to catch a released egg and move it down into the fallopian tube. |
uterus (womb) | the organ in the lower body of a woman or female mammal where offspring are conceived and in which they gestate before birth; the womb |
placenta (afterbirth) | a flattened circular organ in the uterus of pregnant eutherian mammals, nourishing and maintaining the fetus through the umbilical cord |
endometrium | the innermost lining layer of the uterus. Prevents adhesion between the opposed walls of the myometrium, maintaining the patency of the uterine cavity. During the estrous cycle, the endometrium grows thick (blood vessel-rich glandular tissue layer) |
myometrium | is the middle layer of the uterine wall, consisting mainly of uterine smooth muscle cells (also called uterine myocytes), but also of supporting stromal and vascular tissue. Its main function is to induce uterine contractions. |
perimetrium | the tunica serosa of the uterus. Typically composed of loose connective tissue, but contains large numbers of lymphatic vessels. |
cervix | the narrow passage forming the lower end of the uterus |
vagina | the muscular tube leading from the external genitals to the cervix of the uterus in women and most female mammals |
vulva | the external opening of the vagina or reproductive tract in a female mammal |
vestibule of the vulva | The vaginal opening |
homologous | similar in position, structure, and evolutionary origin but not necessarily in function. (of chromosomes) pairing at meiosis and having the same structural features and pattern of genes. |
estrous | the recurring reproductive cycle in many female mammals, including estrus, ovulation, and changes in the uterine lining. |
estrus | a recurring period of sexual receptivity and fertility in many female mammals; heat. |
polyestrus | having more than one period of estrus in a year |
seasonally polyestrous | seasonal breeders have more than one estrous cycle during a specific time of the year and can be divided into short-day and long-day breeders: Short-day breeders, such as sheep, goats, deer and elk are sexually active in fall or winter. |
diestrous | an animal that has two estrous cycles per year |
monoestrous | an animal that has one estrous cycle per year |
proestrus | a preparatory period immediately preceding estrus and characterized by growth of graafian follicles, increased estrogenic activity, and alteration of uterine and vaginal mucosa. |
estrus | a regularly recurrent state of sexual receptivity during which the female of most mammals will accept the male and is capable of conceiving |
anestrus | the period of sexual quiescence between two periods of sexual activity in cyclically breeding mammals |
metestrus | the luteal phase of the reproductive cycle in mammalian females, occurring after ovulation and characterized by development of the corpus luteum, increased progesterone secretion, and decreased estrogen secretion. |
cornification | The process by which squamous epithelial cells in vertebrate animals develop into tough protective layers or structures |
copulation | sexual intercourse |
intromission | the action or process of inserting the penis into the vagina in sexual intercourse |
capacitation | the change undergone by sperm in the female reproductive tract that enables them to penetrate and fertilize an egg. |
acrosome | an organelle that develops over the anterior half of the head in the spermatozoa (sperm cells) of many animals including humans. It is a cap-like structure derived from the Golgi apparatus. |
corona radiata | the innermost layer of the cells of the cumulus oophorus and is directly adjacent to the zona pellucida, the inner protective glycoprotein layer of the ovum. Its main purpose in many animals is to supply vital proteins to the cell. |
zona pellucida | a thick membrane that surrounds the unfertilized eggs of mammals. In order for an egg to be fertilized, sperm must first bind to, and then penetrate this. |
fertilization | occurs when an egg and sperm come together |
zygote | a cell that is formed when an egg is fertilized |
male pronucleus | is the sperm nucleus after it has entered the ovum at fertilization but before fusion with the female pronucleus. |
female pronucleus | is the nucleus of the ovum before fusion with the male pronucleus. |
cleavage | cell division, especially of a fertilized egg cell. |
morula stage | is an early-stage embryo consisting of 16 cells (called blastomeres) in a solid ball contained within the zona pellucida. |
multiparous species | a species of animals that normally bears more than one offspring at a birth. |
umbilical cord | a flexible cordlike structure containing blood vessels and attaching a mammalian fetus to the placenta during gestation. |
amnion | the innermost membrane that encloses the embryo of a mammal, bird, or reptile. |
amniotic sac | the fluid-filled sac that contains and protects a fetus in the womb. |
allantoic sac | a hollow sac-like structure filled with clear fluid that forms part of a developing amniote's conceptus (which consists of all embryonic and extra-embryonic tissues). It helps the embryo exchange gases and handle liquid waste. |
chorion | the outermost membrane surrounding an embryo of a reptile, bird, or mammal. In mammals, it contributes to the formation of the placenta. |
umbilical arteries | either of a pair of arteries that arise from the hypogastric arteries of the mammalian fetus and pass through the umbilical cord to the placenta to which they carry the deoxygenated blood from the fetus. |
umbilical vein | Present during fetal development. Carries oxygenated blood from the placenta into the growing fetus and provides convenient access to the central circulation of a neonate for restoration of blood volume and for administration of glucose and drugs. |
diffuse placental attachment | Almost the entire surface of the allantochorion is involved in formation of the placenta. Horses and pigs. |
cotyledonary placental attachment | Multiple, discrete areas of attachment called cotyledons are formed by interaction of patches of allantochorion with endometrium. Observed in ruminants. |
zonary placental attachment | The placenta takes the form of a complete or incomplete band of tissue surrounding the fetus. Seen in carnivores like dogs and cats, seals, bears, and elephants. |
discoid placental attachment | A single placenta is formed and is discoid in shape. Seen in primates and rodents. |
gestation | the period of time when something is conceived and developed |
gestation period | Fetal development period from the time of conception until birth. |
trimesters | gestational period divided by three |
fetal development | process of growth and development within the womb, in which a single-cell zygote (the cell formed by the combination of a sperm and an egg) becomes an embryo, a fetus, and then a neonate. |
fetal growth | a complex process that involves the interaction of the mother, the fetus, and the interconnecting placenta |
Three Stages of Labor | The first stage of parturition is dilation of the cervix. The second stage of parturition is defined as the delivery of the newborn. The third stage of parturition is the shedding of the placenta or fetal membranes. |
dystocia | refers to abnormal or difficult birth. Causes: maternal factors (uterine inertia, inadequate size of birth canal) and fetal factors (oversized fetus, abnormal orientation as the fetus enters the birth canal). |
neonatal period | sometimes extended from birth to weaning or birth to 2 weeks |
mammary glands | any of the large compound sebaceous glands that in female mammals are modified to secrete milk, are situated ventrally in pairs, and usually terminate in a nipple. |
lactation | describes the secretion of milk from the mammary glands and the period of time that a mother does this to feed her young. The process occurs in all female mammals, although it predates the origin of mammals |
udder | an organ formed of the mammary glands of female ruminants such as cattle, goats, sheep, deer and giraffes. In animals with udders, the mammary glands develop on the milk line near the groin |
mastitis | the inflammation of the mammary gland and udder tissue, and is a major endemic disease of dairy cattle. Milk-secreting tissues and various ducts throughout the udder can be damaged by bacterial toxins, and sometimes permanent damage to the udder occurs. |
teat sinus | the milk storage cavity within the teat and glandular body. The teat is the projecting part of the mammary gland containing part of the milk sinus. |
milk let-down | the process by which a cow will release the milk from her mammary tissues. This process occurs after the mammary gland is stimulated |
streak canal | entrance of the udder or teat canal. It is separated from the udder cistern by a ring of tissue: annular ring. Canals connect to the udder cistern like the branches of a tree and terminate in tiny circular areas known as alveoli which secrete milk. |
lactation | describes the secretion of milk from the mammary glands and the period of time that a mother does this to feed her young. The process occurs in all female mammals, although it predates the origin of mammals |
colostrum | the antibody-rich fluid produced in the mother's mammary glands during the first day or two after birth. It contains a number of antibodies and growth factors, which young animals can absorb intact for the first couple of days following birth. |
meconium | the earliest stool of a mammalian infant. Unlike later feces, it is composed of materials ingested during the time the infant spends in the uterus: intestinal epithelial cells, lanugo, mucus, amniotic fluid, bile, water. |
passive immunity | the short-term immunity which results from the introduction of antibodies from another person or animal. |
antibodies | a blood protein produced in response to and counteracting a specific antigen. They combine chemically with substances which the body recognizes as alien: bacteria, viruses, foreign substances in the blood. |
myoepithelial cells | (myoepithelium cells) usually found in glandular epithelium: thin layer above basement membrane but generally beneath the luminal cells. These may be positive for alpha smooth muscle actin and can contract and expel the secretions of exocrine glands. |
involution of the mammary gland | an essential process that removes the milk-producing epithelial cells when they become redundant at weaning. It is a two-step process that involves the death of the secretory epithelium and its replacement by adipocytes. |
stroma | the supportive tissue of an epithelial organ, tumor, gonad, etc., consisting of connective tissues and blood vessels. |
anastomosing | a connection or opening between two things that are normally diverging or branching, such as between blood vessels, leaf veins, or streams. Such a connection may be normal or abnormal; it may be acquired or innate; and it may be natural or artificial. |
lanugo | fine, soft hair, especially that which covers the body and limbs of a human fetus or newborn. |