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Feralis' Biology > Feralis Ch 4 > Flashcards

Feralis Ch 4 Flashcards

1
Q

Asexual Reproduction - Fission

A

separation of an organism into two new cells (amoeba)

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2
Q

Asexual Reproduction - Budding

A

occurs when a new individual grows from an existing one and then splits off (hydra)

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3
Q

Asexual Reproduction - Fragmentation + Regeneration

A

when a single parent breaks into parts that regenerate into new individuals (sponge/ planaria/starfish)

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4
Q

Asexual Reproduction - Parthenogenesis

A

process in which egg develops without fertilization, resulting in an adult that is either haploid or diploid (honeybees, wasps, ants, some lizards, and hammerhead sharks)

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5
Q

Gonads

A

Gonads describe the reproductive structures responsible for the production of gametes. In males, the gonads are the testis, while in females, the gonads are the ovaries. The gonads are responsible for primary sex characteristics, and are directly involved in reproduction.

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6
Q

Secondary sex characteristics

A

differ from primary characteristics in that they indicate sexual maturity but are not involved in reproduction, such as breast development or increased body fat in females during puberty.

Testosterone results in the secondary sex characteristics in men, but also closes the epiphyses of long bones

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7
Q

Ovary

A

ova, or eggs, are produced here, and each female has two ovaries

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8
Q

Oviduct (fallopian tube/uterine tube)

A

allows for eggs to move from the ovary to the uterus, with one oviduct for each ovary (2)

The ovary isn’t actually directly connected to its adjacent oviduct, so the egg is swept into the oviduct via finger-like fimbrae. Fertilization occurs here!

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9
Q

Uterus

A

muscular chamber where development of the embryo occurs until birth. A fertilized ovum implants (attaches) on the inside uterine wall, or endometrium, on day 6 after fertilization

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10
Q

Vagina

A

at birth, the fetus passes through the cervix, an opening in the uterus, and out of the body

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11
Q

Testis

A

each consists of seminiferous tubules for production of sperm, and interstitial cells (Leydig cells) that produce male sex hormones testosterone and androgens at the beginning of puberty. These hormones are secreted in the presence of LH.

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12
Q

Testis - Sertoli cells

A

are stimulated by FSH and serve to surround and nurture sperm, as well as secrete peptide hormone inhibin, which acts on the anterior pituitary to inhibit FSH release

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13
Q

Testis - Scrotum

A

testis are located here; provides an external cavity about 2oC lower than the body temperature for sperm production.

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14
Q

Epididymis

A

a coiled tube attached to each testis that serves as the site for final maturation and storage of sperm

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15
Q

Vas deferens

A

transfers sperm from one epididymis to the urethra

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16
Q

Seminal vesicles

A

two glands that, during ejaculation, secrete into vas deference and provide mucus (liquid for sperm), fructose (energy for sperm), and prostaglandins (stimulate uterine contractions that help sperm move into uterus).

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17
Q

Prostate gland

A

secretes milky alkaline fluid into urethra and neutralizes acidity of urine that may still be in the urethra, as well as acidity of the vagina. This gland also neutralizes seminal fluid, which is too acidic from metabolic waste of sperm

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18
Q

Bulbourethral (Cowper’s) glands

A

secrete small amount of thick mucus of unknown function into urethra

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19
Q

Penis

A

transports semen (fluid containing sperm and secretions) into the vagina

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20
Q

Sperm

A

are compact packages of DNA specialized for effective male genome delivery.

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21
Q

Sperm - sperm head

A

Haploid (23 chromosomes); at tip is acrosome, a lysosome-like organelle containing enzymes (hyaluronidase), which are used to penetrate the egg. The acrosome originates from Golgi body vesicles that fuse together, and only the nuclear portion of the sperm enters the egg

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22
Q

Sperm - Mid-piece

A

flagellum (9+2 microtubule array) arising from one member of centriole pair, and contains lots of mitochondria

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23
Q

Sperm - Tail

A

remainder of flagellum; sperm is propelled by whiplike motion of tail and mid-piece

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24
Q

mnemonic SEVEn UP

A

Use the mnemonic SEVEn UP to memorize the path of sperm: Seminiferous tubules —> Epididymis —> Vas deferens —> Ejaculatory duct —> Urethra —> Penis (pause before the V for maturation!)

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25
Q

Gametogenesis in Humans

A

Gametogenesis describes the meiotic cell divisions that produce eggs (oogenesis) and sperm (spermatogenesis).

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26
Q

Egg vs sperm

A

The egg contains most of the cytoplasm, RNA, organelles, and nutrients needed by the developing embryo, which explains why the egg is much larger in size than the sperm. The sperm contributes very little cytoplasm during fertilization.

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27
Q

Oogenesis

A

Oogenesis - begins during the female embryonic development (before birth). Oogonia (fetal cells) undergo mitosis and become primary oocytes. These primary oocytes begin meiosis, but remain in prophase I until puberty. During puberty, one primary oocyte is selected and stimulated via FSH to continue its development through meiosis I during the ~28 day menstrual cycle.

i. This primary oocyte continues its development within a follicle, which is formed via encircling cells that protect and nourish the oocyte.
ii. Within the follicle, the oocyte completes meiosis I and becomes the secondary oocyte, which consists mostly of cytoplasm. The secondary oocyte also contains a polar body, which has much smaller cytoplasm content, and may or may not divide, but its products disintegrate.
iii. The secondary oocyte remains arrested in metaphase II until ovulation occurs.

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28
Q

Ovulation

A

Releases the secondary oocyte from a vesicular follicle, which is stimulated by an LH surge. If this oocyte is fertilized by a sperm, the oocyte completes meiosis II, and the resulting ovum/egg becomes diploid. The polar body degenerates.

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29
Q

Ovulation - at puberty

A

At puberty, FSH stimulates the growth of granulosa cells around the primary oocyte, which release a viscous substance that forms the zone pellucida, a jelly like layer around the egg. The structure at this stage is still a primary follicle.

Next, theca cells differentiate from the interstitial tissue and grow around the follicle to form a secondary follicle. Upon stimulation, by LH, theca cells secrete androgen, which is converted to estradiol (a type of estrogen) by the granulosa cells in the presence of FSH and is secreted into the blood.

Typically, estradiol inhibits LH secretion by the anterior pituitary, but just before ovulation, estradiol levels rise rapidly, causing a dramatic increase in LH secretion.

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30
Q

Spermatogenesis

A

begins at puberty within the seminiferous tubules of testes. This differs from oogenesis, which begins during fetal development.

31
Q

Spermatogonia cells

A

undergo mitosis and become primary spermatocytes. These primary spermatocytes undergo meiosis I and form two secondary spermatocytes, which undergo meiosis II to become four spermatids.

32
Q

Sertoli cells

A

Are found in seminiferous tubules, provide nourishment, and “nurse” spermatids as they differentiate into mature spermatozoa (sperm). The sperm complete maturation (gain motility and are stored) in the epididymis.

33
Q

Semen

A

the combination of spermatozoa and fluids that leave the penis upon ejaculation.

34
Q

Capacitation

A

the penultimate step in the maturation of the spermatozoa while in the vagina that allows for egg penetration. This is the final maturation of spermatozoa.

During capacitation, physiological changes occur to the sperm, including changes in intracellular ion concentration, motility, and metabolism.

35
Q

What do eggs release to help sperm motility

A

eggs release progesterone which aids in sperm motility and increases the likelihood of fertilization

36
Q

Spermatogenesis vs oogenesis

A

spermatogenesis is a continuous process, while oogenesis is discontinuous.

37
Q

Female reproductive cycle

A

consists of ovarian cycle (in the ovary) and the menstrual cycle (involves uterus)

38
Q

Female reproductive cycle - Menstrual cycle

A

is divided into the proliferative, secretory, and menstruation (menstrual flow) phases. Menstruation begins with the disintegration of the endometrium (menstrual flow phase)

Hypothalamus and anterior pituitary initiate, Follicle develops, LH surge, Development of endometrium, Corpus luteum disintegrates (no longer maintained by LH)

39
Q

Female reproductive cycle - Menstrual cycle - Hypothalamus and anterior pituitary initiate

A

Monitor estrogen and progesterone in blood. Low levels of estrogen and progesterone stimulate hypothalamus → secretes GnRH → stimulates anterior pituitary to release FSH and LH →

40
Q

Female reproductive cycle - Menstrual cycle - Follicle develops

A

FSH stimulates follicle to secrete estrogen → lots of estrogen (positive feedback on hypothalamus) → produces GnRH → anterior pituitary produces sudden mid cycle surge of LH →

41
Q

Female reproductive cycle - Menstrual cycle - LH surge

A

triggers ovulation (follicle is now the corpus luteum, which develops and is maintained by LH, which along with estrogen, begins to decrease after ovulation), secretes estrogen and progesterone, which stimulate → Development of endometrium

42
Q

Female reproductive cycle - Menstrual cycle - Development of endometrium

A

thickens in preparation for implantation of fertilized egg. If no implantation occurs, then negative feedback on anterior pituitary from increased estrogen And progesterone terminates production of FSH and LH, due to low GnRH from hypothalamus → Corpus luteum disintegrates

43
Q

Female reproductive cycle - Menstrual cycle - Corpus luteum disintegrates

A

Corpus luteum disintegrates (no longer maintained by LH) - becomes corpus albicans; no estrogen and progesterone results in the endometrium shed during the menstruation flow phase!

44
Q

Female reproductive cycle - implantation

A

If implantation occurs, then the embryo (placenta) secretes chorionic gonadotropin (HCG), which maintains the corpus luteum.

The production of estrogen and progesterone remains high, so the endometrium is not shed. HCG is later replaced by progesterone from the placenta. Without HCG, menstruation would begin, and the embryo would abort, as the embryo “maintains” pregnancy. This is why pregnancy tests check the presence of HCG in urine to deduce if a female is pregnant or not. If a fertilized egg implants anywhere other than the endometrium of the uterus, it is considered an ectopic pregnancy, and usually spontaneously aborts.

45
Q

Graafian follicle

A

The follicle that releases the secondary oocyte is also called the Graafian follicle

46
Q

Female reproductive cycle - Ovarian cycle - Follicular phase

A

development of egg and secretion of estrogen from follicle [ends at ovulation]

47
Q

Female reproductive cycle - Ovarian cycle - Ovulation

A

mid-cycle release of egg

48
Q

Female reproductive cycle - Ovarian cycle - Luteal phase

A

secretion of estrogen and progesterone from corpus luteum after ovulation [shedding of the uterine lining lasting approximately 5 days]

Note that the secretory phase of the menstrual cycle overlaps with the luteal phase of the ovarian cycle

49
Q

Estrogen vs progesterone

A

estrogen serves to thicken the endometrium, while progesterone serves to develop and maintain the endometrial wall.

Progesterone also inhibits lactation during pregnancy. The fall in progesterone after delivery allows for milk production.

50
Q

Male reproductive cycle

A

GnRH → FSH + LH (also known as

ICSH, interstitial cell stimulating hormone → testosterone and androgens from testes)

51
Q

Male reproductive cycle - FSH and testosterone

A

FSH and testosterone → influence Sertoli cells to promote development of sperm (nourish sperm during development, or spermatogenesis). Hormone and gamete production are constant unlike in females.

52
Q

Male reproductive cycle - LH

A

LH stimulates Leydig cells (in the interstitium between seminiferous tubules) to release testosterone + androgens that promote spermatogenesis in tubules.

53
Q

Male reproductive cycle - Sertoli cells

A

Sertoli cells secrete inhibin that acts on the anterior pituitary to inhibit FSH secretion.

54
Q

Male contraception

A

a pill would interfere with LH and FSH to decrease sperm production

55
Q

Female hormonal contraception

A

estradiol and/or progesterone are spiked artificially high → negative feedback suppresses LH/FSH surge → no ovulation can occur → no fertilization possible

56
Q

Animal embryos follow four stages in growth and development

A

Animal embryos follow four stages in growth and development: gametogenesis (sperm/egg formation), embryonic development (fertilization of egg until birth), reproductive maturity (puberty), and aging process to death

57
Q

Development in mammals

A

development occurs in two stages: embryonic development followed by fetal development. A fetus is an embryo that resembles the human infant form, and in humans, an embryo is called a fetus at about 8 weeks.

58
Q

Stages of embryonic development (sea urchin, echinoderm) - Fertilization

A

sperm penetrates plasma membrane of secondary oocyte

59
Q

Stages of embryonic development (sea urchin, echinoderm) - Fertilization - Recognition

A

before penetrating, the sperm secretes proteins that bind with receptors that reside on a glycoprotein layer surrounding the plasma membrane of the oocyte. In humans, this layer is a vitelline layer (zona pellucida). In both organisms, the layer ensures same species fertilization.

60
Q

Zona pellucida

A

external glycoprotein membrane surrounding the plasma membrane (jelly coat) of an oocyte. This first appears in unilaminar oocytes, and is secreted by both the oocyte and follicular cells. At puberty, FSH stimulates growth of granulosa cells around the primary oocyte that secrete the viscous zona pellucida.

61
Q

Zona pellucida binding sperm

A

The zona pellucida expresses specific receptor proteins called ZP3, which bind to proteins expressed in the head of the sperm. The binding of ZP3 triggers the acrosome reaction, during which the enzymatic contents of the acrosome are released.

When the zona pellucida binds sperm, the acrosome reaction is initiated.

The sperm releases the contents of its acrosome as it approaches the egg, and contributes to a charge- based ‘fast block’ of polyspermy

62
Q

5 days after fertilization

A

blastocyst undergoes zona hatching (zona pellucida degenerates and is replaced by the underlying layer of trophoblastic cells so it can implant in the uterus)

63
Q

Capacitation

A

In capacitation, secretions from the uterus wall and uterine tube destabilize the plasma membrane surrounding the head of the sperm (acrosome), making the head more fluid, which helps prepare it for fertilization and makes the sperm hyperactive (faster and wiggle more).

The capacitated sperm moves through the corona radiata (dense layer of granulosa cell surrounding the oocyte) and comes into contact with the zona pellucida.

64
Q

Acrosome reaction - enzymatic contents of the acrosome

A

These enzymes help digest a path through the zona pellucida, allowing the sperm to enter the perivitelline space (space between the plasma membrane of the secondary oocyte and the zona pellucida), which then fuses with the oocyte’s plasma membrane.

65
Q

How to ensure only one sperm penetrates the zona pellucida and fuses with the oocyte membrane

A

The fusion of sperm to zona pellucida activates a fast block and a slow block to polyspermy

First, during the fast block, which takes place after fusion, the oocyte membrane depolarizes, preventing other sperm from fusing with it. Slow block to polyspermy is then stimulated by this depolarization —

during slow block to polyspermy, a wave of intracellular calcium is released, causing small cortical granules beneath the oocyte membrane to release their contents outward, rendering ZP3 in the zona pellucida inactivate and making it impermeable. Note that intracellular Ca2+ triggers cortical granule release, but the granules themselves don’t contain Ca2+.

66
Q

Zona pellucida in non-mammals

A

In non-mammals, the zona pellucida plays an important role in preventing cross-breeding of different species, especially in species where fertilization occurs outside of the body.

67
Q

Zona pellucida - immunocontraception

A

The zona pellucida is also commonly used to control wildlife population via immunocontraception. When the zona pellucida of one animal species is injected into the bloodstream of another, sterility of the second animal occurs due to an immune response. Fertilization cannot occur because antibodies have already bound to the zona pellucida, thus preventing sperm from binding

68
Q

Fertilization - eggs

A

Fertilization can be external in water (lots of eggs laid since the chance of fertilization is lower - frogs/amphibians) or internal (terrestrial vertebrates). The # of eggs laid is affected by the following factors: internal vs external fertilization, early development, and amount of parental care (less care = more eggs)

69
Q

Steps after capacitation and the acrosome reaction

A

Penetration, Formation of fertilization membrane, Completion of meiosis II in secondary oocyte, Fusion of nuclei and replication of DNA

70
Q

Steps after capacitation and the acrosome reaction - Penetration

A

plasma membrane of sperm and oocyte fuse, and the sperm nucleus enters the oocyte

71
Q

Steps after capacitation and the acrosome reaction - Formation of fertilization membrane

A

the vitelline layer forms a fertilization membrane that blocks additional sperm (remember, this is due to the cortical reaction, which is the exocytosis of enzymes produced by cortical granules in egg cytoplasm during fertilization → called slow block in mammals)

72
Q

Steps after capacitation and the acrosome reaction - Completion of meiosis II in secondary oocyte

A

sperm penetration triggers meiosis II to complete. The oocyte was previously arrested in metaphase in humans. The result is an ovum and a second polar body, which is discharged through the plasma membrane

73
Q

Steps after capacitation and the acrosome reaction - Fusion of nuclei and replication of DNA

A

sperm and ovum nuclei fuse → diploid zygote forms. This is associated with a sharp increase in protein synthesis and metabolic activity.

74
Q

Fertilization location

A

Fertilization takes place in the oviduct (fallopian tubes); cleavage while swept; and the embryo is at the blastula stage by the time it reaches the uterus for implantation

Feralis' Biology (6 decks)

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