46 Chapter Flashcards
(123 cards)
1
Q
Reproduction
A
The generation of new individuals from existing ones
2
Q
There are two modes of animal reproduction:
A
Sexual and asexual
3
Q
Zygote
A
The diploid cell produced by the union of haploid gametes during fertilization; a fertilized egg.
4
Q
Egg
A
The female gamete; is large and nonmotile
5
Q
Sperm
A
The male gamete; is small and motile
6
Q
In asexual reproduction,
A
New individuals are generated without the fusion of egg and sperm.
7
Q
For most asexual animals, reproduction relies entirely on mitotic cell division.
A
True
8
Q
Budding
A
A mechanism for asexual reproduction, in which new individuals arise from outgrowths of existing ones.
9
Q
Fission
A
A mechanism of asexual reproduction, involving the separation of a parent organism into two individuals of approximately equal size.
10
Q
Common mechanism of asexual reproduction involve which two steps?
A
Fragmentation: the breaking of the body into several pieces
Regeneration: Regrowth of lost body parts.
If more than one piece grows and develops into a complete animal, the effect is reproduction.
11
Q
Parthenogenesis
A
A form of asexual reproduction, in which an egg develops without being fertilized.
12
Q
Ovulation
A
The release of an egg from an ovary. In humans, an ovarian follicle releases an egg during each uterine (menstrual) cycle.
13
Q
Hermaphroditism
A
A condition in which an individual has both female and male gonads and functions as both a male and a female in sexual reproduction by producing both sperm and eggs.
14
Q
Sessile
A
stationary
15
Q
In some species, hermaphrodites can also self-fertilize, allowing a form of sexual reproduction that doesn’t require any partner.
A
True
16
Q
Fertilization
A
The union of sperm and egg
17
Q
Fertilization can either be _________ or _________
A
External, internal
18
Q
In species with external fertilization,
A
The female releases eggs into the environment, where the male then fertilizes them.
19
Q
In internal fertilization,
A
Sperm are deposited in or near the female reproductive tract, and fertilization occurs within the tract.
20
Q
Spawning
A
A process of external fertilization, in which individuals clustered in the same area release their gametes into the water at the same time
21
Q
Eutherian
A
Placental
22
Q
Placenta
A
A temporary organ in the mother which supplies the fetus with the mother’s blood supply
23
Q
Gonads
A
Organs that produce gametes
24
Q
Spermathecae (spermatheca sing.)
A
Are sacs in which sperm may be stored for extended periods, a year or more in some species. Is found in many insect species.
25
Cloaca
A common opening for the digestive, urinary, and reproductive tracts found in many nonmammalian vertebrates but in few mammals.
26
The human male’s external reproductive organs are the:
Scrotum and penis
27
Testes
The male gonads; produce sperm in highly coiled tubes called seminiferous tubules
28
Seminiferous tubules
A highly coiled tube in the testes in which sperm are produced.
29
Most mammals produce sperm properly only when the testes are cooler than the rest of the body.
True
30
Scrotum
A pouch of skin outside the abdomen that houses the testes; functions in maintaining the testes at the lower temperature required for spermatogenesis.
31
Testicle
A testis within a scrotum
32
Epididymis
A coiled tubule located adjacent to the mammalian testis where sperm are stored. It functions to provide an environment where sperm can complete maturation and become motile.
33
Ejaculation
The propulsion of sperm from the epididymis through the muscular vas deferens, ejaculatory duct, and urethra.
34
Vas deferens
In mammals, the tube in the male reproductive system in which the sperm travel from the epididymis to the urethra.
35
Each vas deferens (one from each epididymis) extends around and behind the urinary bladder, where it joins a duct from the seminal vesicle, forming ______________
A short ejaculatory duct
36
Urethra
The outlet tube for both the excretory system and the reproductive system
37
Three sets of accessory glands produce secretions that combine with sperm to form semen:
The seminal vesicles
The prostate gland
The bulbourethral gland
38
Semen
The fluid that is ejaculated
39
Two seminal vesicles contribute about 60% of the volume of semen.
True
40
Seminal vesicle
A gland in males that secretes a fluid component of semen that lubricated and nourishes the sperm. The fluid contains mucus, fructose, a coagulating enzyme, ascorbic acid, and prostaglandins.
41
Prostate gland
A gland in human males that secretes an acid-neutralizing component of semen. This fluid is deposited directly into the urethra through small ducts and contains anticoagulant enzymes and citrate.
42
Bulbourethral glands
A pair of small glands along the urethra below the prostate. Functions to secrete clear mucus that neutralizes any acidic urine remaining in the urethra.
43
There is evidence that bulbourethral fluid carries some sperm released before ejaculation, which may contribute to the high failure rate of the withdrawal method of birth control (coitus interruptus).
True
44
Penis
The copulatory structure of male mammals. Contains the urethra as well as three cylinders of spongy erectile tissue.
45
Glans
The rounded structure at the tip of the clitoris or penis that is involved in sexual arousal.
46
Prepuce
Foreskin
47
The human female’s external reproductive structure are:
the clitoris and two sets of labia, which surround the clitoris and vaginal opening.
48
Ovary
In animals, the structure that produces female gametes and reproductive hormones. The female gonads.
49
Follicles
A microscopic structure in the ovary that contains the developing oocyte and secretes estrogens.
50
Oocyte
A cell in the female reproductive system that differentiates to form an egg. A partially developed egg surrounded by support cells.
51
Oviduct
A tube passing from the ovary to the vagina in invertebrates or to the uterus in vertebrates, where it is also called the fallopian tube.
52
Upon ovulation, cilia on the epithelial lining of the oviduct help collect the egg by drawing fluid from the body cavity into the oviduct. Together with wavelike contractions of the oviduct, the cilia convey the egg down to the uterus, also known as the womb.
True
53
Uterus
A female organ where eggs are fertilized and/or development of the young occurs. The uterus is a thick, muscular organ that can expand during pregnancy to accommodate a 4-kg fetus.
54
Endometrium
The inner lining of the uterus, which is richly supplied with blood vessels.
55
Cervix
The neck of the uterus, which opens into the vagina.
56
Vagina
Part of the female reproductive system between the uterus and the outside opening; the birth canal in mammals. During copulation, the vagina accommodates the male’s penis and receives sperm.
57
Vulva
Collective term for the female external genitalia.
58
Labia majora
A pair of thick, fatty ridges that encloses and protects the rest of the vulva.
59
Labia minora
A pair of slender skin folds that surrounds the openings of the vagina and urethra.
60
The vaginal opening and the separate opening of the urethra are located within a cavity bordered by the labia minora.
True
61
Hymen
A thin piece of tissue that partly covers the vaginal opening in humans at birth and usually until sexual intercourse or vigorous physical activity ruptures it.
62
Clitoris
Is located at the top of the labia minora and consists of erectile tissue supporting a rounded glans, or head, covered by a small hood of skin, the prepuce.
63
Mammary gland
An exocrine gland that secretes milk for nourishing the young. Mammary glands are characteristic of mammals. Are present in both sexes in humans.
64
Gametogenesis
The production of gametes
65
Spermatogenesis
The formation and development of sperm
66
Oogenesis
The development of mature oocytes
67
Where are stem cells that give rise to sperm situated?
Near the outer edge of the seminiferous tubules.
68
Sperm-producing stem cells’ progeny are released into the lumen of the seminiferous tubules as they pass through the following stages:
Spermatocyte stage
Spermatid stage
69
Spermatogonia (spermatogonium)
A cell that divides mitotically to form spermatocytes. Present in mature testes.
70
Each spermatocyte gives rise to four spermatids through meiosis, reducing the chromosome number from diploid (2n=46 in humans) to haploid (n=23).
True
71
Acrosome
A vesicle in the tip of a sperm containing hydrolytic enzymes and other proteins that help the sperm reach the egg.
72
Oogonia (oogonium)
A cell that divides mitotically to form oocytes.
73
Oogenesis begins in the female embryo with the production of oogonia from primordial germ cells.
True
74
Primary oocytes
An oocyte prior to completion of meiosis I. Are the result of dividing oogonia, which divide by mitosis to form cells that begin meiosis, but stop the process at prophase I before birth. Reside within a small follicle.
75
At birth, the ovaries together contain about 1-2 million primary oocytes, of which about 500 fully mature between puberty and menopause.
True
76
Secondary oocyte
An oocyte that has completed meiosis I and is arrested at meiosis II. Is released at ovulation, when its follicle breaks open. Only if a sperm penetrates the oocyte does meiosis II resume.
77
Gonadotropin-releasing hormone (GnRH)
A tropic hormone secreted by the hypothalamus that directs the anterior pituitary to secrete the gonadotropins, follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
78
Testosterone levels are roughly ten times higher in males than in females. In contrast, estradiol levels are about ten times higher in females than in males; females also produce more progesterone.
True
79
The gonads are the major source of sex hormones, with much smaller amounts being produced by the adrenal glands.
True
80
Secondary sex characteristics
The physical and behavioral differences between males and females that are not directly related to the reproductive system.
81
Follicle stimulating hormone effect in male reproductive system
FSH stimulates Sertoli cells, located within the seminiferous tubules, to nourish developing sperm.
82
Luteinizing hormone effect on male reproductive system
LH causes Leydig cells, scattered in connective tissue between the seminiferous tubules, to produce testosterone and other androgens, which promote spermatogenesis in the tubules.
83
Inhibin
A hormone that in males is produced by Sertoli cells. Functions in one of the two negative feedback mechanisms that control sex hormone production in males by acting on the anterior pituitary gland to reduce FSH secretion. Testosterone also functions in negative feedback.
84
Menstruation
The shedding of portions of the blood-rich endometrium during a uterine cycle.
85
Ovarian cycle
The cyclic recurrence of the follicular phase, ovulation, and the luteal phase in the mammalian ovary, regulated by hormones.
86
The female reproductive cycle is actually one integrated cycle involving two organs, the uterus and the ovaries.
True
87
Ovarian cycle step 1-2
1. The hypothalamus releases GnRH, which stimulates the anterior pituitary.
2. Anterior pituitary secretes small amounts of FSH and LH.
88
Ovarian cycle step 3-4
3. FSH (as its name implies) stimulates follicle growth, aided by LH.
4. The cells of the growing follicles start to make estradiol. Known as the follicular phase because it is the part of the ovarian cycle during which follicles grow and oocytes mature.
89
Ovarian cycle step 5-6
5. Estradiol secretion by the growing follicle begins to rise steeply.
6. The FSH and LH levels increase markedly due to the estradiol increase. Although a low level of estradiol inhibits the secretion of pituitary gonadotropins, a high concentration has the opposite effect: It stimulates gonadotropin secretion by causing the hypothalamus to increase its output of GnRH. A high estradiol concentration also increases the GnRH sensitivity of LH-releasing cells in the pituitary, resulting in a further increase in LH levels.
90
Ovarian cycle step 7
7. The maturing follicle, containing a fluid-filled cavity, enlarges, forming a bulge at the surface of the ovary. The follicular phase ends at ovulation, about a day after the LH surge. In response to both FSH and the peak in LH level, the follicle and adjacent wall of the ovary rupture, releasing the secondary oocyte. At or near the time of ovulation, women sometimes feel a distinctive pain in the lower abdomen, on the same side as the ovary in which the oocyte was released.
91
Ovarian cycle step 8
8. The beginning of the luteal phase. The ruptured follicle transforms into a corpus luteum due to stimulation by LH. The corpus luteum secretes progesterone and estradiol, which in combination exert negative feedback on the hypothalamus and pituitary. This feedback reduces the secretion of LH and FSH to very low levels, preventing another egg from maturing when a pregnancy may already be under way.
If pregnancy does not occur, low gonadotropin levels at the end of the luteal phase cause the corpus luteum to disintegrate, triggering a sharp decline in estradiol and progesterone concentrations.
92
Ovarian cycle step 9
9. Secretory phase of the uterine cycle.
The estradiol and progesterone secreted by the corpus luteum stimulate maintenance and further development of the uterine lining, including enlargement of arteries and growth of endometrial glands. These glands secrete a nutrient fluid that can sustain an early embryo even before it implants in the uterine lining. Thus, the luteal phase of the ovarian cycle is coordinated with the secretory phase of the uterine cycle.
93
Proliferative phase of the uterine cycle
Prior to ovulation, ovarian steroid hormones stimulate the uterus to prepare for support of an embryo. Estradiol secreted in increasing amounts by growing follicles signals the endometrium to thicken. In this way, the follicular phase of the ovarian cycle is coordinated with the proliferative phase of the uterine cycle.
94
Ovarian cycle step 10
10. If an embryo has not implanted in the endometrium by the end of the secretory phase, the corpus luteum disintegrates. The resulting drop in ovarian hormone levels causes arteries in the endometrium to constrict. Deprived of its circulation, the uterine lining largely disintegrates, releasing blood that is shed along with endometrial tissue and fluid. The result is menstruation—the menstrual flow phase of the uterine cycle. During this phase, which usually lasts a few days, a new group of ovarian follicles begin to grow.
95
Endometriosis
The condition resulting from the presence of endometrial tissue outside of the uterus.
96
Ectopic
Occurring in an abnormal location
97
Menopause
The cessation of ovulation and menstruation. Occurs after about 500 cycles. During this interval, the ovaries lose their responsiveness to FSH and LH, resulting in a decline in estradiol production.
98
Estrous cycles
A reproductive cycle characteristic of female mammals except humans and certain other primates, in which the nonpregnant endometrium is reabsorbed rather than shed, and sexual response occurs only during mid-cycle at estrus. Estrus is the period surrounding ovulation.
99
Vasocongestion
The filling of a tissue with blood.
100
Myotonia
Increased muscle tension.
101
The sexual response cycle can be divided into four phases:
Excitement
Plateau
Orgasm
Resolution
102
Coitus
Sexual intercourse
103
The zygote begins a series of cell divisions called cleavage about 24 hours after fertilization and after an additional 4 days produces a blastocyst, a sphere of cells surrounding a central cavity.
True
104
Blastocyst
The blastula stage of mammalian embryonic development, consisting of an inner cell mass, a cavity, and an outer layer, the trophoblast. In humans, the blastocyst forms 1 week after fertilization.
105
Pregnancy, or gestation
The condition of carrying one or more embryos in the uterus; also called gestation.
106
The roughly nine months of human gestation are divided into three trimesters of equal length.
True
107
During the first trimester,
The implanted embryo secretes hormones that signal its presence and regulate the mother’s reproductive system.
108
Human chorionic gonadotropin (hCG)
An embryonic hormone that acts like pituitary LH in maintaining secretion of progesterone and estrogens by the corpus luteum through the first few months of pregnancy.
109
Some hCG passes from the maternal blood to the urine, where it can be detected by the most common early pregnancy tests.
True
110
Trophoblast
The outer layer of the blastocyst
111
During the embryo’s first 2-4 weeks of development, the embryo obtains nutrients directly from the endometrium. Meanwhile, the outer layer of the blastocyst, which is called the trophoblast, grows outward and mingles with the endometrium, eventually helping form the placenta.
True
112
Organogenesis
The development of the body organs.
113
The main period of organogenesis is the _____________
The first trimester
114
Fetus
A developing mammal that has all the major structures of an adult. In humans, the fetal stage lasts from the 9th week of gestation until birth.
115
During the second trimester,
The fetus grows to about 30 cm in length and is very active.
116
During the third trimester,
The fetus grows to about 3-4 kg in weight and 50 cm in length. Fetal activity may decrease as the fetus fills the available space. As the fetus grows and the uterus expands around it, the mother’s abdominal organs become compressed and displaced, leading to digestive blockages and a need for frequent urination.
117
Labor
A series of strong, rhythmic uterine contractions that push the fetus and placenta out of the body.
118
Three stages of labor
Dilation of cervix
Expulsion: delivery of the infant
Delivery of the placenta
119
Lactation
The production of mother’s milk
120
Contraception
The deliberate prevention of pregnancy
121
Vasectomy
The cutting and tying off of each vas deferens to prevent sperm from entering the urethra.
122
Abortion
The termination of a pregnancy in progress
123
Miscarriage
Spontaneous abortion
