Week 5

Question 1

Sperm

Answer 1

Sperm are immobile at body temperature;
therefore, the testes are external to the body so
that a correct temperature (2 C° lower than body
temp) is maintained for motility.
* Semen is a mixture of sperm (about 5% of the
total) and fluids from accessory glands that
contribute most of the semen’s volume.
* Sperm are haploid cells, consisting of a
flagellum for motility, a neck that contains the
cell’s energy-producing mitochondria, and a
head that contains the genetic material.
* This structure contains enzymes that can digest
the protective coverings that surround the egg
and allow the sperm to fuse with the egg. An
ejaculate will contain from 50–120 million
sperm per milliliter.
* Sperm form in the walls of seminiferous
tubules that are coiled inside the testes.

Question 2

Scrotum and testes

Answer 2

• The scrotum houses the testicles and provides
  passage for blood vessels, nerves, and muscles
  related to testicular function.
• The testes are a pair of male gonads that produce
  sperm and reproductive hormones.
• Each testis is divided into wedge-shaped lobes by
  septa. Coiled in each wedge are seminiferous
  tubules that produce sperm.

Question 3

Semininferous tubules

Answer 3

The walls of the seminiferous tubules are
made up of the developing sperm cells,
with the least developed sperm at the
periphery of the tubule and the fully
developed sperm next to the lumen.
* The sperm cells are associated with Sertoli
cells that nourish and promote the
development of the sperm.
* Other cells present between the walls of
the tubules are the interstitial cells of
Leydig, which produce testosterone once
the male reaches adolescence.
* When the sperm have developed flagella,
they leave the seminiferous tubules and enter
the epididymis

Question 4

Epididymis

Answer 4

The epididymis lies along the top and
posterior of the testes and is the site of
sperm maturation. The sperm leave the
epididymis and enter the vas deferens,

Question 5

Vas deferens

Answer 5

carries the sperm behind the bladder, and
forms the ejaculatory duct with the duct from
the seminal vesicles.
* During a vasectomy, a section of the vas
deferens is removed, preventing sperm from
being passed out of the body during
ejaculation and preventing fertilization.

Question 6

Spermatogenesis

Answer 6

• Spermatogenesis occurs in the wall of the Spermatogenesis seminiferous tubules, with the most primitive cells
  at the periphery of the tube and the most mature
  sperm at the lumen of the tube.
• Immediately under the capsule of the tubule are
  diploid, undifferentiated cells. These stem cells,
  each called a spermatogonium, go through mitosis
  to produce one cell that remains as a stem cell and
  a second cell called a primary spermatocyte.
• The diploid primary spermatocyte goes through
  meiosis I to produce two haploid cells called
  secondary spermatocytes.
• Each secondary spermatocyte divides after meiosis
  II to produce two cells called spermatids.
• Spermiogenesis is the last stage wherein the
  formation of spermatozoa takes place. In the last
  stage, the spermatid cells see an increase in the
  size of the tail and a decrease in the spermatozoa
  head.
• Four sperm result from each primary spermatocyte
  that goes through meiosis.

Question 7

FSH in males

Answer 7

• FSH enters the testes and stimulates the Sertoli cells
  located in the walls of the seminiferous tubules to
  begin promoting spermatogenesis.

Question 8

LH in males

Answer 8

LH also enters the testes and stimulates the interstitial
cells of Leydig, located in between the walls of the
seminiferous tubules, to make and release
testosterone into the testes and the blood.

Question 9

Testosterone

Answer 9

• Testosterone stimulates spermatogenesis. This
  hormone is also responsible for the secondary sexual
  characteristics that develop in the male during
  adolescence.
• Secondary sex characteristics in males include a
  deepening of the voice, the growth of facial, axillary,
  and pubic hair, an increase in muscle bulk, and the
  beginnings of the sex drive.

Question 10

Negative feedback system in males

Answer 10

• A negative feedback system occurs in the male
  with rising levels of testosterone acting on the
  hypothalamus and anterior pituitary to inhibit
  the release of GnRH (gonadotropin-releasing
  hormone), FSH, and LH.
• In addition, the Sertoli cells produce the
  hormone inhibin, which is released into the
  blood when the sperm count is too high.
• This inhibits the release of GnRH and FSH,
  which will cause spermatogenesis to slow
  down. If the sperm count reaches a low of 20
  million/mL, the Sertoli cells cease the release
  of inhibin, and the sperm count increases.

Question 11

Ovary

Answer 11

The outermost layer of the ovary is made up of
follicles, each consisting of one or more
follicular cells that surround, nourish, and
protect a single egg.

Question 12

Fallopian tubes/oviducts

Answer 12

• The oviducts, or fallopian tubes, extend
  from the uterus in the lower abdominal
  cavity to the ovaries, but they are not in
  contact with the ovaries.
• The lateral ends of the oviducts flare out
  into a trumpet-like structure and have a
  fringe of finger-like projections called
  fimbrae.
• When an egg is released at ovulation, the
  fimbrae help the nonmotile egg enter into
  the tube.
• The walls of the oviducts have a ciliated
  epithelium over smooth muscle. The cilia
  beat, and the smooth muscle contracts,
  moving the egg toward the uterus.
• Fertilization usually takes place within the
  oviduct and the developing embryo is
  moved toward the uterus. It usually takes
  the egg or embryo a week to travel through
  the oviduct

Question 13

Uterus

Answer 13

• The uterus is a structure about the size of
  a woman’s fist. The uterus has a thick
  muscular wall and is lined with an
  endometrium rich in blood vessels and
  mucus glands that develop and thicken
  during the female cycle.
• Thickening of the endometrium prepares
  the uterus to receive the fertilized egg or
  zygote, which will then implant itself in
  the endometrium. The uterus supports
  the developing embryo and fetus during
  gestation.
• The endometrium builds up again in
  preparation for implantation.

Question 14

Cervix

Answer 14

Part of the uterus, called the cervix,
protrudes into the top of the vagina.

Question 15

Vagina

Answer 15

The vagina is a muscular tube that serves
several purposes. It allows menstrual flow
to leave the body. It is the receptacle for
the penis during intercourse and the
pathway for the delivery of offspring.

Question 16

Oogenesis

Answer 16

• Oogenesis occurs in the outermost layers of the
  ovaries.
• Oogenesis starts with a germ cell. In oogenesis,
  this germ cell is called an oogonium and forms
  during the embryological development of the
  individual.
• The oogonium undergoes mitosis to produce about
  one to two million oocytes by the time of birth.
• The primary oocytes begin meiosis before birth.
  However, the meiotic division is arrested in its
  progress in the first prophase stage.
• At the time of birth, all future eggs are in prophase I.
  This situation is in contrast with the male reproductive
  system in which sperm are produced continuously
  throughout the life of the individual.
• Starting at adolescence, anterior pituitary hormones
  cause the development of a few follicles in an ovary
  each month. This results in a primary oocyte finishing
  the first meiotic division.
• The cell divides unequally, with most of the cytoplasm
  and organelles going to one cell, called a secondary
  oocyte, and only one set of chromosomes and a small
  amount of cytoplasm going to the other cell. This
  second cell is called a polar body and usually dies.
• Cell division is again arrested, this time at metaphase II.
• At ovulation, the secondary oocyte is released and
  travels toward the uterus through the oviduct.
• If the secondary oocyte is fertilized, the cell continues
  through meiosis II, producing a second polar body and
  haploid egg, which fuses with the haploid sperm to
  form a fertilized egg (zygote) containing all 46
  chromosomes.

Question 17

Gonads

Answer 17

a specialized organ that contains germ cells which are responsible for producing
the haploid cells required for sexual reproduction.

Question 18

Gonadotropim

Answer 18

Any hormone having a stimulating effect on the gonads.
Two such hormones are secreted by the anterior pituitary gland:
▪ Follicle-stimulating hormone (FSH)
▪ Luteinizing hormone (LH)

Question 19

Yellow Body

Answer 19

After ovulation, the follicle in which the egg was located becomes a so-called
yellow body and begins to produce progesterone in addition to estrogen.

Question 20

Endometrium

Answer 20

The inner mucous membrane lining of the womb (uterus) that undergoes changes
in structure and thickness at different stages of the menstrual cycle, and much of
which is shed at menstruation

Question 21

Ovulation

Answer 21

Ovulation is the process in which a mature egg is released from the ovary

Question 22

Menstural Phase

Answer 22

• The menstrual phase is the first stage of the menstrual
  cycle when the period (bleeding) occurs
• This phase starts when an egg from the previous cycle
  isn’t fertilized.
• Because pregnancy hasn’t taken place, levels of the
  hormones estrogen and progesterone drop.
• The thickened lining of the uterus, which would support
  a pregnancy, is no longer needed, so it sheds through
  the vagina.
• During the period, a combination of blood, mucus, and
  tissue from your uterus are released.
• On average, women are in the menstrual phase of their
  cycle for 3 to 7 days.

Question 23

Follicular Phase

Answer 23

• Starts when the hypothalamus sends a signal
  to the pituitary gland to release folliclestimulating hormone (FSH).
• FSH stimulates the ovaries to produce
  around 5 to 20 small sacs called follicles.
  Each follicle contains an immature egg.
• The follicular phase starts on the first day of
  the period (so there is some overlap with
  the menstrual phase)
• The maturing follicle sets off a surge in
  estrogen that thickens the lining of the
  uterus. This creates a nutrient-rich
  environment for an embryo to grow.
• The average follicular phase lasts for about
  16 days.
• Only the healthiest egg will eventually
  mature. (On rare occasions, a woman may
  have two eggs mature.)
• The rest of the follicles will be reabsorbed
  into the body.
• Follicular phase ends when ovulation
  occurs.

Question 24

Ovulation Phase

Answer 24

• Rising estrogen levels during the follicular
  phase trigger the pituitary gland to release
  luteinizing hormone (LH). This is what
  starts the process of ovulation.
• Ovulation is when your ovary releases a
  mature egg. The egg travels down the
  fallopian tube toward the uterus to be
  fertilized by sperm.
• The ovulation phase is the only time
  during the menstrual cycle when a female
  can get pregnant.
• Symptoms of Ovulation:
  oa slight rise in basal body temperature
  othicker discharge that has the texture
  of egg whites
• Ovulation happens at around day 14 if you have a 28-day cycle — right
  in the middle of your menstrual cycle. It lasts about 24 hours. After a
  day, the egg will die or dissolve if it isn’t fertilized.

Question 25

Luteal Phase

Answer 25

• After the follicle releases its egg, it changes
  into the corpus luteum.
• The corpus luteum releases hormones, mainly
  progesterone and some estrogen. The rise in
  hormones keeps the uterine lining thick and
  ready for a fertilized egg to implant.
• If a female gets pregnant, her body will
  produce human chorionic gonadotropin
  (hCG). This is the hormone pregnancy tests
  detect. It helps maintain the corpus luteum
  and keeps the uterine lining thick.
• If pregnancy does not occur, the corpus
  luteum will shrink away and be resorbed.
  This leads to decreased levels of estrogen
  and progesterone, which causes the onset of
  the period.
• The uterine lining will shed during the
  period.
• The luteal phase lasts for 11 to 17 days. The
  average is 14 days.