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Biology 12 > Reproduction > Flashcards

Reproduction Flashcards

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1
Q

What are testes?

A
  • sometimes called testicles
  • paired organs that develop from gonads within abdomen of fetus
  • the scrotum maintains testes at cooler temperature than the abdominal cavity; this is necessary for producing viable sperm
  • inside the tests are seminiferous tubules which are tubules packed into lobes of the testes that produce sperm
  • inside the seminiferous tubules are other cells called sertoli cells that nourish the developing sperm cells
  • interstitial cells in the testes surround the seminiferous tubules and produce male hormones
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2
Q

What is sperm?

A

-the male gamete(sex cell)
-men can produce up to 1 000 000 000 sperm per day, and over 100 million sperm per ejaculation; but usually fewer than 100 reach the egg
-the whole spermatogenesis takes about 9-10 weeks
-sperm is produced inside seminiferous tubules in the testes
-the testes contains lobules, each with one to three coiled seminiferous tubules with total length of 250 m/testis
-the sperm mature and are stored in the tubular epididymis behind each testes and once mature, sperm are propelled into vas deferens by smooth muscle contractions(peristalsis)
-the sperm moves from storage to vas deferens to urethra for ejaculation
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3
Q

What three parts are sperm composed of?

A
  • head; contains DNA of 23 chromosomes and on tip of the the head is the acrosome cap; the acrosome cap contains enzymes needed to penetrate the outer barriers of the egg
  • middle piece; contains numerous mitochondria
  • tail
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4
Q

What is spermatogenesis?

A
  • the development of sperm
  • it involves meiosis(cell division that reduces the number of chromosomes by half from 46 to 23)
  • sertoli cells are other cells inside the seminiferous tubules that support, nourish and regulate the cells that generate sperm cells
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5
Q

What is the penis?

A
  • The penis is a cylindrical-shaped organ in that hangs in front of scrotum.
  • The spongy tissue inside the shaft of the penis is flaccid (soft) with normal blood flow in the penis.
  • Erection occurs from increased blood flow filling spongy tissue.
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6
Q

What is semen?

A

-a thick, whitish fluid containing sperm and secretions
-about 10% of semen is a sperm, which constitutes around 300-400 million semen per ejaculation
-semen comes from three organs:
^seminal vesicles that join the vas deferens. Its secretions are added to the semen at the time of ejaculation; they secrete fructose for ATP production and prostaglandins which are hormones that cause the uterus to control and help propel the sperm
^Prostate glandthat surrounds urethra below bladder. It secretes a milky alkaline fluid that aids sperm motility and survival (helps to neutralize the acidic enviornment in the vagina)
^Bulbourethral glands (often called Cowper’s glands) have mucous secretions with lubricating effect.

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7
Q

What is ejaculation?

A
  • the process in which semen is forced from the penis
  • Sexual arousal can cause an erection, and ejaculation occurs when sexual arousal reaches its peak.
  • After sperm enters the ejaculatory duct, the seminal vesicles, prostate gland, and Cowper’s gland release their secretions.
  • Rhythmical contractions (peristalsis) of the ejaculatory duct and urethra expels semen from the penis. This (and accompanying physiological and psychological sensations) is known as the male orgasm.
  • The “refractory period” is typical time following ejaculation during which erection cannot occur. This time tends to increase as a man ages
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8
Q

What are the hormones that control the development and maintenance of the male reproductive system?

A
  • Hormones and negative feedback cycles control the development and maintenance of the male reproductive system.
  • GnRH; gonadotropin releasing hormone
  • FSH; follicle stimulating hormone
  • LH; leutinizing hormone
  • inhibin
  • First the hypothalamus secretes gonadotrophic releasing hormone (GnRH). GnRH triggers the anterior pituitary to produce the two hormones, FSH and LH. Finally Inhibin is produced
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9
Q

What does FSH do?(male)

A
  • promotes spermatogenisis in seminiferous tubules
  • it does this by entering the sertoli cells and causing them to take up more testosterone
  • this enhances sperm production
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10
Q

What does LH do?(male)

A
  • controls production of testosterone by interstitial cells
  • causes increased testosterone levels in the blood as a negative feedback cycle
  • interaction of hormones maintains fairly constant production of sperm and testosterone
  • in general, hormone levels are higher in the morning
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11
Q

What does inhibin do?

A
  • As sperm is made, Sertoli cells in the seminiferous tubules also release hormone inhibin.
  • The more sperm that is made, the more inhibin is released.
  • As inhibin (and therefore sperm) levels rise, this is detected by the hypothalamus and anterior pituitary gland.
  • The hypothalamus and anterior pituitary in turn, reduce the release of GnRH and FSH, which in turn reduces the amount of sperm and inhibin being released. This is a classic negative feedback cycle.
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12
Q

What does testosterone do?

A
  • Promotes normal development and function of primary sexual organs of male (penis & testes)
  • Causes development of secondary sexual characteristics during puberty (beard growth, axillary & pubic hair), deepens voice, greater muscle growth)
  • Development of sperm (FSH causes spermatogenic cells in testes to take up testosterone – testosterone causes these cells to produce sperm).
  • Sex drive is also related to testosterone levels. Indeed, testosterone is administered to people (male or female!) who complain of a low sex drive.
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13
Q

What some side effects of testosterone?

A
  • testosterone increases secretions from oil and sweat glands(contributes to acne and body odor)
  • baldness(which is also controlled by genetic factors)
  • Since testosterone causes an increase in muscle mass, athletes have used testosterone and other “anabolic steroids” to artificially boost their body’s natural male hormone levels. However, anabolic steroids have serious negative side effects.
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14
Q

What are ovaries?

A
  • two egg-shaped organs on each side of uterus in the pelvic abdominal cavity
  • produce eggs and the sex hormones estrogen & progesterone
  • contain follicles that contain oocytes(eggs)
  • females are born with about 2 million follicles which is reduced to around 350 000-400 000 and only 400 follicles that will mature in a lifetime
  • each month, an ovary produces an egg that bursts from ovary during ovulation(release of egg)
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15
Q

What is the oviduct(fallopian tube)?

A
  • tubes to the uterus and extend from near ovaries into uterus
  • sweep up eggs from the ovary using cilia lining and waiting fimbria at end of oviducts
  • muscular contractions and cilia lining the oviducts waft the egg toward uterus by peristalsis
  • the site of fertilization; sperm usually meets and fertilize the egg in the upper oviduct
  • tubular pregnancies occur when embryo implants in oviduct; ectopic pregnancy is any implantation outside body of uterus; any tubular pregnancy must be removed by surgery as it can be life threatening
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16
Q

What is the uterus?

A
  • a thick walled muscular, hollow, pear-shaped organ for nurturing an embryo(fetus develops here)
  • it lies on top of bladder and the opening in cervix which leads to vagina
  • it is muscular because contraction for birthing must use strength and must be able to stretch to 30cm
  • the lining of the uterus is called the endometrium; it is composed of connective tissue, glands, and blood vessels
  • the endometrium lines the uterus, and if pregnancy occurs, forms the placenta
17
Q

What is the cervix?

A
  • located at back of vaginal canal and is a muscular sphincter that must stretch when birthing
  • between the vagina and uterus
  • has numerous mucosal glands that help to form the mucus plug in the cervix to prevent bacteria and sperm from entering the uterus; this mucus plug only disappears during ovulation
18
Q

What is the vagina?

A
  • a muscular tube with mucosa lining for lubrication
  • has a 45 degree angle with small of back which makes childbirth more difficult in humans compared to animals
  • serves in sexual intercourse and the birth canal during childbirth
  • it’s rich in glycogen(energy source) and has an acidic environment pH 4.5) to kill bacteria
  • yeast infections occur when the pH balance is off
19
Q

What are some external genitalia?

A

-the external genitals are known as the vulva
-there are 2 sets of skin folds called labia
^outermost are a pair fat-padded skin folds called the labia majora
^the labia minora extend from vaginal opening to encircle clitoris at front
-the clitoris is partly enclosed by the labia minora; is an erectile organ that has many sensory nerve recptors which makes it sexually sensitive and is prominent in the process of femal orgasm; equivalent to male’s penis and has a shaft of erectile tissue capped by a pear-shaped gland
-the hymen is a ring of tissue that may partially close the vaginal opening; can be broken by vigorous exercise, injuring to the area, or sexual intercourse

20
Q

What is the female cycle broken down into?

A
  • uterine cycle
  • ovarian cycle
  • before ovulation(called the follicular phase)
  • after ovulation(called the luteal phase)
21
Q

What is the timing in the 28 day cycle?

A
  • day 1-5: low levels of estrogen and progesterone cause endometrium to disintegrate, blood vessels rupture and flow out of vagina during menstruation
  • day 6-13: endometrium becomes thicker and move vascular due to increased amounts of estrogen called proliferative phase(lining is being shed and built)
  • day 14: ovulation occurs
  • day 15-28: endometrium doubles in thickness, uterine glands mature and secrete mucus due to production of progesterone by corpus luteum; readies uterus to receive developing embryo
22
Q

What happens in the ovarian cycle?

A

-follicular phase:
^low levels of female hormones in blood from days 1-5
^FSH(follicle stimulating hormone and is released by the pituitary gland) levels increase from during days 6-13; this causes a follicle to mature. As follicle matures, it makes more and more estrogen so estrogen levels rise
^high levels of estrogen in blood causes hypothalamus to secrete a large amount of GnRH which leads to a LH surge at day 13 which causes ovulation at day 14
^negative feedback by estrogen on FSH ends follicular phase
-luteal phase:
^days(15-28): corpus luteum makes increasing amounts of progesterone
^high progesterone causes negative feedback control over anterior pituitary secretions of LH causing corpus luteum to degenerate
^as luteal phase ends, menstruation occurs

23
Q

What happens in the uterine cycle?

A

-proliferative phase:
^low levels of female hormones causes menstruation(days 1-5); endometrium breaks down
^days 6-13: the rising levels of estrogen makes the endometrium thicken and become vascular & glandular; the endometrium rebuilds itself
-secretory phase:
^days 15-28: progesterone makes endometrium double in thickness
^uterine glands mature and release thick mucold secretions
^as corpus luteum degenerates, progesterone secretion decreases, this causes menstruation to occur again

24
Q

What happens when the follicle is developing?

A
  • menstruation occurs, followed by a rebuilding of the uterine lining
  • increased levels of female hormones follow menstruation
  • estrogen predominates
  • an LH surge causes ovulation on day 14
25
Q

What happens when the follicle is awaiting fertliization? (luteal phase)

A
  • progesterone predominates
  • the endometrium doubles in thickness and secretes mucus
  • around about day 25, the corpus luteum “dies”
  • the endometrium lining starts to degenerate by about day 28
  • as luteal phase ends, menstruation begins, and the whole cycle begins again
26
Q

What is estrogen and what does it do?

A
  • steroid hormone that is produced by the ovaries
  • stimulates growth of uterus and ovaries at puberty
  • works with progesterone for breast development
  • responsible for secondary sex characteristics (body hair, fat distribution under skin, enlargement of pelvic girdle)
  • responsible for uterine cycle and growth of the endometrium
  • matures egg
27
Q

What does FSH and estrogen do?(female)

A
  • when it’s released from the anterior pituitary gland, it stimulates the growth of a follicle which in turn stimulates the secretion of estrogen
  • estrogen, which is released from the follicle, stimulates the growth and repair of the endometrium lining; the growing levels of estrogen have a negative feedback on FSH and eventually shut of its release; it also has a positive feedback on LH causing more released around mid cycle
28
Q

What does LH do?(female)

A
  • it’s released from the anterior pituitary gland around mid cycle, caused by a build up of estrogen
  • stimulates ovulation
  • LH converts the follicle to develop into a corpus luteum; the corpus luteum secretes estrogen and progesterone
  • the corpus lutuem maintains hormone levels of estrogen(this still blocks FSH)
  • the corpus luteum increases levels of progesterone stimulating the final growth of the uterine lining; it also has a negative feedback on LH
29
Q

What happens when fertilization occurs?

A
  • only 1 sperm fertilizes the egg
  • Fertilization occurs in the fallopian tube (oviduct) and the acrosome releases its enzymes which break through the outer layer of the egg.
  • The plasma membranes of the egg and sperm fuse, and the nucleus from the sperm enters the egg.
  • Finally, the sperm nucleus fuses with the egg nucleus. This could correctly be viewed as the moment of conception; The new individual at this point is called a zygote
30
Q

What happens after fertilization occurs?

A
  • the fertilized egg develops as it travels down the fallopian tube to uterus
  • the embryo embeds in endometrial lining several days after fertlization(usually at the end of the first week)
  • to implant, the trophoblast secretes enzymes to digest blood vessels and endometrium

Biology 12 (11 decks)

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