Chapter 36: Reproduction

Question 1

Compare and contrast sexual and asexual reproduction, genetically same

Answer 1

Asexual:1 Parent, No gametes, no sex organs, no fertilization

Sexual: 2 Parents, Sperm and eggs, gonads and accessory organs, fertilization, genetically unique

Question 2

Give examples of different forms of sexual and asexualreproduction

Answer 2

Sexual: Bisexual Reproduction; Hermaphroditism

Asexual: Budding; Gemmulation; Fragmentation

Question 3

Give examples of animals reproducing asexually; and reproducing sexually

Answer 3

Sexually: Vertebrates

Asexually: Annelid worms, sponges, cnidarians, sea stars

Question 4

Define parthenogenesis

Answer 4

A form of asexual reproduction in which females produce offspring from unfertilized eggs

Question 5

Contrast internal and external fertilization

Answer 5

Internal Fertilization: The fusion of eggs and sperm within the female reproductive tract; sperm deposited in or near tract; enables sperm to reach an egg efficiently; requires sophisticated and compatible reproductive systems and cooperative behavior

External Fertilization: The female releases eggs into the environment where the male fertilizes them; moist habitat needed to prevent gametes from drying out and to allow sperm to swim

Question 6

Distinguish betweenrandKstrategists

Answer 6

• R-strategists
  
  • External fertilization → Many offspring (because) → Unstable environment (Lower rate of survival so more chances)
• K-strategists
  
  • Internal fertilization → Fewer offspring (because) → Stable environment (Higher rate of survival so less chances)

Question 7

Defineand distinguish the terms: sex, gender, and gender identity

Answer 7

• Sex: the biological aspects of being male or female
• Gender: the behavioral, psychological, & social characteristics of men and women
• Gender identity: person’s own sense of identification as female, male, both, neither, or somewhere in between

Question 8

Give examples offunctional and behavioraldifferences between sex

Answer 8

• Males are generally better at:
  
  • Visuospatial skills
  • Targeting accuracy
  • Navigation
• Females are generally better at
  
  • Memory for object location
  • Fine motor skills
  • Verbal memory
  • Fluency

Question 9

What are gametes and where are they made?

Answer 9

• Gametes - A haploid reproductive cell, such as an egg or sperm, that is formed by meiosis or is the descendant of cells formed by meiosis.
• Gametes are made in the gonads
• Gonads - Male or female gamete-producing organ

Question 10

Explain the general hormonal regulation of the reproductive system in humans

Answer 10

• The male and female reproductive cycles are controlled by hormones released from the hypothalamus and anterior pituitary as well as hormones from reproductive tissues and organs.
• In the male, FSH and LH stimulate Sertoli cells and interstitial cells of Leydig in the testes to facilitate sperm production. The Leydig cells produce testosterone, which also is responsible for the secondary sexual characteristics of males.
• In females, FSH and LH cause estrogen and progesterone to be produced. They regulate the female reproductive system which is divided into the ovarian cycle and the menstrual cycle. Menopause occurs when the ovaries lose their sensitivity to FSH and LH and the female reproductive cycles slow to a stop.

Question 11

Describe the male reproductive system, including be able to annotate the various structures

Answer 11

• The human male’s external reproductive organs are the scrotum and penis. The internal reproductive organs consist of a pair of gonads that produce both sperm and reproductive hormones, accessory glands that secrete products essential to sperm movement, and ducts that carry the sperm and glandular secretions
• The male gonads, or testes (singular, testis), produce sperm in highly coiled tubes called seminiferous tubules.

Question 12

Recognize that the urethra is used by both the reproductive and urinary system

Answer 12

The ejaculatory ducts open into the urethra, the outlet tube for both the excretory system and the reproductive system. The urethra runs through the penis and opens to the outside at the tip of the penis.

Question 13

Explainwhy the testes are held outside of thebody

Answer 13

Most mammals produce sperm properly only when the testes are cooler than the rest of the body. In humans and many other mammals, the scrotum, a fold of the body wall, maintains testis temperature about    2  ° C below the core body temperature.

Question 14

Explainwhat semen is

Answer 14

Three sets of accessory glands—the seminal vesicles, the prostate gland, and the bulbourethral glands—produce secretions that combine with sperm to form semen, the fluid that is ejaculated.

Question 15

Orderthe path of the semen through the relevant structures

Answer 15

Seminiferous tubules —> Epididymis —> Vas deferens —> Ejaculatory ducts —> Urethra

Question 16

Explainthe functions of the secretions fromtheaccessory glands

Answer 16

• Seminal Vesicles - contribute about 60% of the volume of semen; thick, yellowish, and alkaline (neutralizes acidic vaginal area) fluid (contains mucus, fructose, coagulation enzymes, ascorbic acid, prostaglandins)
• Prostate Gland - secretes its products into the urethra through small ducts; fluid is thin and milky; it contains anticoagulant enzymes and citrate (a sperm nutrient).
• Bulbourethral Glands - before ejaculation, secretes clear mucus that neutralizes acidic urine remaining in the urethra; also carries sperm released before ejaculation (one reason for withdrawal birth control failure rate)

Question 17

Describe the anatomy of theseminiferoustubules

Answer 17

• Open space in the center of the tubule is the lumen
• The walls of the seminiferous tubules are composed of:
  
  • Several layers of germ cells (spermatogonia) and primary & secondary spermatocytes in the process of becoming sperm
  • Sustentacular (Sertoli cells) that facilitate the development of sperm cells
• Clusters of Leydig cells are found in the interstitial spaces between the seminiferous tubules

Question 18

Explain the process of spermatogenesis and where it takes place

Answer 18

• Spermatogenesis: Primordial germ cell → Spermatogonium → Mitosis → Primary Spermatocyte → Meiosis 1 → Secondary Spermatocyte → Meiosis 2 → Spermatids → Maturation → Sperm
• One of the cells produced by the mitosis is another spermatogonium, so the male never runs out of sperm
• Spermatogenesis takes place in the seminiferous tubules

Question 19

Describethe function ofSustentacular(Sertoli) andLeydig Cells

Answer 19

• Sustentacular (Sertoli cells) play an essential role innurturing and providing structural support for the sperm cells during their development
• Leydig cells are theprimary source of testosterone or androgens in males

Question 20

Describethe glands and hormones involved in regulatingspermatogenesis

Answer 20

• Follicle Stimulating Hormone - Causes Sertoli cells to nourish developing sperm
• Luteinizing Hormone - Causes Leydig cells to produce testosterone; Produced by Anterior Pituitary
• Testosterone - Promote spermatogenesis in the tubules; Produced by Leydig cells

Question 21

Describe the male sexual response

Answer 21

During sexual arousal, the erectile tissue, which is derived from modified veins and capillaries, fills with blood from the arteries. As this tissue fills, the increasing pressure seals off the veins that drain the penis, causing it to engorge with blood. The resulting erection enables the penis to be inserted into the vagina.

Question 22

Describe the female reproductive system, including be able to annotate the various structures

Answer 22

The human female’s external reproductive structures are the clitoris and two sets of labia, which surround the clitoris and vaginal opening. The internal organs are the gonads, which produce both eggs and reproductive hormones, and a system of ducts and chambers, which receive and carry gametes and house the embryo and fetus

Question 23

Recognize that the female reproductive and urinary systems are totally separated

Answer 23

In the male, the systems are not fully separated (semen passes through the urethra), while in the female, they aremorphologically separated (vagina and urethra).

Question 24

Explain the functions of the ovaries, fallopian tubes and uterus

Answer 24

• Ovaries - The female gonads that flank the uterus and are held in place in the abdominal cavity by ligaments
• Fallopian Tube (Oviduct) - extends from the uterus toward a funnel-like opening at each ovary.
• Uterus (womb) - thick, muscular organ that can expand during pregnancy to accommodate a 4-kg fetus. The inner lining of the uterus, the endometrium, is richly supplied with blood vessels.

Question 25

Explain what an ovarian follicle is

Answer 25

A small, fluid-filled sac in the ovary that contains one immature egg (developing oocyte). There are thousands of follicles in the ovaries. It secretes estrogens.

Question 26

Explain the process of oogenesis and where it takes place

Answer 26

Oogenesis: Primordial germ cell → Oogonium → Mitosis → Primary Oocyte Meiosis 1 → Secondary Oocyte + Polar bodies → Meiosis 2 → Oocyte becomes Ootid → Maturation → Ovum

Happens in ovary

Question 27

Contrastoogenesisand spermatogenesis

Answer 27

Spermatogenesis - Production of sperm cells; Oogenesis - Production of eggs

• Spermatogenesis is continuous in adult males (hundreds of millions of sperm per day). Oogenesis is a prolonged process in the human female (could take years/decades to complete development).
• In spermatogenesis, the four products of meiosis develop into mature gametes. In oogenesis, cytokinesis during meiosis is unequal, with almost all the cytoplasm segregated to a single daughter cell (egg). Smaller cells called polar bodies degenerate.
• Spermatogenesis occurs throughout adolescence and adulthood. In contrast, the mitotic divisions of oogenesis in human females are thought to be complete before birth, and the production of mature gametes ceases at about age 50.
• Spermatogenesis produces mature sperm from precursor cells in a continuous sequence, whereas oogenesis has long interruptions.

Question 28

What are the ovarian and uterine (menstrual) cycles

Answer 28

Ovarian cycle - Cyclic events in the ovaries

Uterine (Menstruation) cycle - Changes in the uterus

Question 29

Describemajoreventsoccurringduring each phase of theovariancycles

Answer 29

Follicular phase (days 0-13) → Ovulation (day 14) → Luteal phase (days 15-28)

• Follicular phase: Hypothalamus releases GnRH → Stimulates Anterior Pituitary to secrete FSH and LH → Follicle begins to grow and create estradiol (type of estrogen) → Rising levels of estradiol increase FSH and LH blood levels (positive feedback) → Follicle matures
• Ovulation: Happens about a day after the LH surge → Peak in LH levels causes the follicle and wall of the ovary to rupture, releasing the secondary oocyte.
• Luteal phase: LH stimulates corpus luteum formation → Corpus luteum secretes progesterone and estradiol → Negative feedback on hypothalamus → FSH and LH reduce → Corpus luteum disintegrates because low GnRH → Progesterone and estradiol decline → Hypothalamus restarts cycle

Question 30

Describemajoreventsoccurringduring each phase of theuterine cycles

Answer 30

(Coordinated with Ovarian cycle) Proliferative phase (days 6-14) → Secretory phase (days 15-28) → Menstrual phase (days 1-5)

• Proliferative: Estradiol signals endometrium to thicken
• Secretive: estradiol and progesterone of corpus luteum stimulate uterine lining development after ovulation → corpus luteum disintegrates and causes drop in hormone levels which causes the uterine lining to disintegrate
• Menstrual: Blood shed with endometrial tissue → New set of ovarian follicles grow → Day 1 of flow is day 1 of each cycle

Question 31

Explain how and why the ovarian and uterine cycles are interconnected

Answer 31

• The follicular phase of the ovarian cycle is coordinated with the proliferative phase (days 6–14) of the uterine cycle because uterus prepares for potential child
• The luteal phase of the ovarian cycle is coordinated with what is called the secretory phase (days 15–28) of the uterine cycle

Question 32

List the hormones and glands involved in regulating the ovarian and uterine cycles

Answer 32

• Ovarian: Hypothalamus release GnRH, which stimulates the anterior pituitary to secrete FSH and LH. FSH stimulates follicle growth which makes estradiol. Rise in estradiol increases FSH and LH. LH surge causes ovulation a day later, and LH stimulates corpus luteum formation. Corpus luteum secretes progesterone and estradiol which reduces LH and FSH. Low levels of LH and FSH trigger hypothalamus to restart cycle.
• Uterine: Estradiol signals endometrium to thicken. After ovulation, estradiol and progesterone stimulate maintenance of uterine lining.

Question 33

Describe the specific effects of FSH and LH on the ovarian cycle

Answer 33

Ovarian: Hypothalamus release GnRH, which stimulates the anterior pituitary to secrete FSH and LH. FSH stimulates follicle growth which makes estradiol. Rise in estradiol increases FSH and LH. LH surge causes ovulation a day later, and LH stimulates corpus luteum formation. Corpus luteum secretes progesterone and estradiol which reduces LH and FSH. Low levels of LH and FSH trigger hypothalamus to restart cycle.

Question 34

Describe the effects of estrogen and progesterone on the functional layer of theendometrium

Answer 34

Uterine: Estradiol signals endometrium to thicken. After ovulation, estradiol and progesterone stimulate maintenance of uterine lining. Lining deteriorates after hormone levels drop

Question 35

Give examples of negative and positive feedback in hormonal controlof the femalereproductivecycle

Answer 35

• Positive feedback: Estradiol secretion by follicle increases FSH and LH levels
• Negative feedback: Progesterone and estradiol secreted by corpus luteum reduce FSH and LH secretion

Question 36

Describe different outcomes for the uterus depending on whether or not the egg isfertilized

Answer 36

• If the egg is not fertilized, the corpus luteum degenerates, progesterone levels decrease, and the endometrium is shed.
• If the egg is fertilized, the zygote preserves the corpus luteum, progesterone levels remain high, and the endometrium thickens in preparation for implantation.

Question 37

Give example of cannabis impact on male and female reproduction

Answer 37

Males: Testicular failure; Erectile Dysfunction

Females: Ovulatory Disfunction; Impact on embryonic development and baby development