Unit 12: Reproduction

Question 1

Testes and scrotum

Answer 1

Male gonad

• Produce sperm
• Found in a sac called scrotum, which suspends the testes outside of the body. The scrotum can bring the testes closer or farther away from the body to regulate the temperature.

Question 2

Seminiferous tubules

Answer 2

Testes are composed of compartments, in which contains sets of 3 tightly coiled seminiferous tubules. These are sites of spermatogenesis, the production of sperm.

Question 3

Interstitial cells

Answer 3

Cells found between the seminiferous tubules. Secretes testosterone.

Question 4

Epididymis

Answer 4

Tightly coiled duct lying just outside each testis.

-Stores sperm as they mature

Question 5

Ductus vas deferens

Answer 5

Long tube that starts from the epididymis, pass through the abdominal cavity, curves around the bladder and leads into an ejaculatory duct.

• Stores sperm
• Conducts sperm from the testes to the uterus

Question 6

Urethra

Answer 6

Tube that the ejaculatory duct leads into

-Conducts sperm out of the body

Question 7

Prostate gland

Answer 7

A single doughnut shaped gland that surround the upper portion of the urethra just below the bladder
-Contributes basic fluid to seminal fluid

Question 8

Bulbourethral gland

Answer 8

Pair of pea-sized organs that lie below the prostate gland

-Contributes mucoid fluid to seminal fluid

Question 9

Seminal vesicles

Answer 9

Lies at the base of the bladder, each has a duct that joins with a vas deferens
-Contributes nutrients and fluid to seminal fluid

Question 10

Sperm structure

Answer 10

• Head: contains the nucleus, with 23 chromosomes.
• Acrosome: a cap covering the head; contains hydrolytic enzymes so that sperm may penetrate the egg
• Midpiece: contains mitochondria to produce energy for the movement of the tail
• Tail: structure of a flagella, provides mobility

Question 11

Seminal fluid function

Answer 11

• Slightly basic pH to counteract the acid environment in the vagina. Sperm are more viable in a basic environment
• Contains fructose to provide energy for the sperm to swim
• Contains prostaglandins to cause the uterus to contract; this helps propel the sperm towards the egg
• Contains mucous which provides a protective medium for the sperm and lubrication during sexual intercourse

Question 12

Testosterone function

Answer 12

• Essential for development of primary sex organs
• Essential for development of sperm
• During puberty, brings about and maintains male sex characteristics (deeper voice, prominent Adam’s apple, broader shoulders, maturation of penis/testes, aggression, muscular strength)
• Cause development of noticeable facial, armpit, chest, and pubic hair

Question 13

Gonadotropin releasing hormone (GnRH)

Answer 13

Hormone released by the hypothalamus

Causes the anterior pituitary to release FSH and LH

Question 14

Follicle-stimulating hormone (FSH)

Answer 14

Promotes spermatogenesis in the seminiferous tubules

Promotes the development of a follicle in the ovary

Question 15

Luteinizing hormone (LH)

Answer 15

Promotes production of testosterone in the interstitial cells.
Promotes the development of the corpus luteum

Question 16

Hormonal regulation of testosterone

Answer 16

• Testosterone levels are regulated by negative feedback mechanism:
  i) Increased testosterone levels in blood -> less LH -> less testosterone
  ii) Decreased testosterone levels -> more LH -> more testosterone

Question 17

Ovaries

Answer 17

Female gonad

• Pair of grape-like organs, with each ovary lying on either side of the upper pelvic cavity
• Each alternate to produce one egg per month
• Produce reproductive hormones

Question 18

Follicles

Answer 18

Small sacs of fluid found on the outside layer of the ovaries
-Each contains an immature egg, called an oocyte

Question 19

Corpus luteum

Answer 19

Glandlike structure developed from a follicle that has lost its oocyte through ovulation
-Produces sex hormones

Question 20

Oviduct

Answer 20

Two-arm like organ that extends from the uterus to the ovaries

• Site of fertilization (sperm fusing with egg)
• Conducts the fertilized egg towards the uterus

Question 21

Uterus

Answer 21

Thick-walled, muscular organ lying and tipping over the urinary bladder

• Site of implantation (embryo embeds itself in the uterus wall)
• Site of the development of the embryo

Question 22

Cervix

Answer 22

Narrow end of uterus leading to the vagina

-Dilates at birth to allow the passage of the baby from the uterus into the vagina

Question 23

Vagina

Answer 23

Tube that lies at a 45-degree angle from the cervix

• Female organ of sexual intercourse; receives the penis
• Serves as a birth canal, as well as an exit for menstrual flow

Question 24

Vulva

Answer 24

6. Vulva: The external female genital organ
   Consists of:
   i) Labia majora: Two large, hair-covered protective folds of skin
   ii) Labia minora: Two small, protective folds of skin lying just inside the labia majora
   iii) Clitoris: Female organ of sexual arousal; comparable to the male penis, contains a shaft of erectile tissue that swells with blood during sexual stimulation

Question 25

Ovarian cycle: Follicular phase

Answer 25

Days 1-13 1. Hypothalamus releases GnRH 2. GnRH stimulates the secretion of FSH by the anterior pituitary 3. FSH promotes the development of a follicle in the ovary 4. Developing follicle starts to secrete estrogen 5. Oogenesis (meiosis) occurs, resulting in the oocyte dividing into a secondary oocyte and a polar body 6. The chromosome count goes from 46 -> 23 – this is the egg 7. The follicle matures – known as the vesicular follicle

Question 26

Ovarian cycle: Ovulation

Answer 26

Day 14 1. Surge in estrogen levels triggers an LH spike 2. LH spike causes the vesicular follicle to burst and the egg to be released -> ovulation 3. Increasing estrogen levels exert negative feedback to the hypothalamus/anterior gland so that FSH levels decrease and the follicular phase ends

Question 27

Ovarian cycle: Luteal phase

Answer 27

1. LH is secreted by the anterior pituitary, in the same way as the FSH 2. LH promotes the development of the corpus luteum 3. Corpus luteum secretes progesterone and some estrogen 4. Increasing progesterone levels exert negative feedback so that LH levels decrease and the luteal phase ends. 5. i) No fertilization: Corpus luteum will degenerate ii) If fertilization/implantation occur: Corpus luteum continue to secrete hormones for 3-4 months, until the placenta can take over

Question 28

Ovarian cycle vs the Uterine cycle

Answer 28

Ovarian: The development of follicle, ovulation, and corpus luteum Uterine: Changes in the endometrium – the lining of the uterus, due to the hormones secreted by the ovary during the ovarian cycle.

Question 29

Uterine cycle: Menstruation

Answer 29

Days 1-5 - Low levels of all female sex hormones, the corpus luteum has just been degenerated - Causes the endometrium to disintegrate and its blood vessels to rupture - Blood and disintegrated tissue, known as the menses, passes out of the vagina

Question 30

Uterine cycle: Proliferative phase

Answer 30

Days 6-13 - A new developing follicle secretes estrogen - Increasing levels of estrogen cause the endometrium to thicken, and become more vascular/glandular

Question 31

Uterine cycle: Secretory phase

Answer 31

Days 14-28 - Corpus luteum secretes progesterone and some estrogen - Increasing levels of progesterone cause the endometrium to double/triple in thickness - The endometrium becomes highly vascularized, and the uterine glands mature - The uterus is now ready for implantation of the embryo

Question 32

Human chorionic gonadotropic hormone (HCG)

Answer 32

Produced by the placenta, after implantation Prevents the breakdown of the corpus luteum, which maintains the production of progesterone that keeps the endometrium from breaking down.

Question 33

Estrogen/Progesterone function

Answer 33

Main female sex hormones Estrogen: Development of the sex organs, responsible for body hair development, fat distribution beneath the skin, etc during puberty. Both are responsible for breast development