Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

biology > 18 — reproduction in humans > Flashcards

18 — reproduction in humans Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards
1
Q

Testis (singular) (plural: testes)

A

produces sperms and male sex
hormones such as testosterone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Epididymis

A

stores inactive sperms from
the testis before they are
released into the sperm ducts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Spermatic cord

A

supplies blood to the testis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Scrotum (scrotal sac)

A

pouch-like sacs located outside
the body cavity to help
maintain a lower temperature
for the development of sperms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Prostate gland

A

Mixes sperm with a fluid which nourishes sperm with nutrients and contains enzymes which activate sperm to swim actively.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Sperm duct (vas deferens)

A

the pathway travelled by sperms
after they are released from the
testis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Seminal vesicle

A

stores sperms temporarily
before they are released
through the urethra

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Semen

A

Seminal vesicle, prostate
gland, and Cowper’s gland
activate sperms by secreting a
slippery fluid that contains
nutrients and enzymes. The mixture of this fluid and sperms is called semen.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Urethra

A

a tube that extends from the
bladder, through the penis, to
outside the body

Both urine and semen exit the
body through the urethra, but
never at the same time.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

sphincter muscles

A

he sphincter muscles at
the base of the urinary
bladder prevent urine from
exiting the body during
ejaculation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Penis

A

erectile organ that becomes
erect and hard during sexual
intercourse in order to enter
and deposit semen into the
vagina

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Erection

A

An erection occurs when the
spongy tissue in the penis
is filled with blood.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Sperms (spermatozoa)

A

The head contains:
* a nucleus that carries one haploid set of chromosomes,
* small amount of cytoplasm, and
* an acrosome that contains enzymes for breaking down part of
the egg membrane for sperm penetration.
2) The middle piece:
* contains numerous
mitochondria that release energy for sperm to swim to the egg
3) The tail (flagellum):
* beats to enable the sperm to swim towards the egg. The sperm is motile.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

why the need for many sperms

A
  • Increases chance of fertilising the egg by increasing ratio of sperms to egg (e.g. 100,000,000:1)
  • Fast-swimming sperm can reach the egg in half an hour, while others may take days.
  • The sperm can live up to 48-72 hours.
  • Only a few hundred will even come close to the egg because of the many natural barriers that exist in a woman’s body.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Ovary

A

produces eggs/ ova and female
sex hormones such as estrogen
and progesterone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Oviduct (fallopian tube)

A

a narrow muscular tube with a
funnel-like opening at the ovary that transports eggs to the uterus by peristalsis of the muscular wall and sweeping action of the cilia; site of fertilisation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Ova

A

Mature eggs/ova are released from the ovary into the oviduct to be fertilised, from the time a female reaches puberty until she reaches menopause which is abt 45-55 yo. (usually one matured ovum is released by one of ovaries each month)

The ovum is made up of a:
* large nucleus containing
one haploid set of chromosomes,
* large amount of cytoplasm which may contain a small amount of
yolk, and
* cell surface membrane that is surrounded by an outer membrane.

Each ovary releases about 250 mature ova in thelife of the female.
Singular: ovum
Plural: ova

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Uterus (womb)

A

Site of implantation of embryo and the location where the fetus
develops; it has elastic muscular walls that enable contraction during birth to expel the fetus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

uterine lining (endometrium)

A

the soft, smooth inner lining
of the uterus rich in blood
supply that is important for
embryo implantation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Cervix

A

the circular ring of muscle at
the lower end of uterus which enlarges to allow passage of the fetus during birth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Vagina (birth canal)

A

the location where semen is
deposited during sexual intercourse; spans the area from the cervix to the vulva

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

State the differences between the male gamete and female gamete in terms of structure, motility and numbers.

A

Structure:
M:
* Has a head, mid body and a
flagellum
* Haploid nucleus contains either X or
Y chromosome
* 60micrometer long

F:
* Spherical in shape
* Haploid nucleus contains
only X chromosome
* Diameter 120m to 150m

Motility:
M: motile
F: non-motile

Numbers:
* Numerous sperms are produced
throughout the life from puberty
onwards
* Large number of sperms released
during each ejaculation
* Number of eggs
determined at birth
* Usually only one matured
egg is released per month

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Puberty

A

Puberty refers to the stage of human growth and development in which a person’s body becomes capable of reproduction.

During this period:
* Sex organs mature
* Sex organs secrete sex hormones:
Testosterone (male)/Estrogen and progesterone (female)
* Sex hormones cause secondary sexual characteristics to develop.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Secondary sexual characteristics

A

In males:
* Hair starts to grow in the
pubic region, at the armpits and on the face.
* The penis and testicles increase in size
* Larynx enlarges and voice deepens
* Production of sperm begins

In females:
* Hair starts to grow in the
pubic region and at the armpits.
* Breast and uterus enlarge
* Hips broaden
* Menstruation and ovulation begin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

The menstrual cycle

A

The cycle of events that takes place in the female reproductive organs every month

average length of a menstrual cycle
is 28 days.
* There is a natural variation in the length of the menstrual
cycle; ranging from 21 to 33 days.
* The menstrual cycle can be affected by stress, illness,
unbalanced diet, and/or malnutrition.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Menstruation

A

The monthly discharge of blood from the uterus via the vagina

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Ovarian cycle (in the ovaries)

A
  • Development of follicles
  • Release of sex hormones (estrogen and progesterone) in regulating uterine cycle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Uterine cycle (in the uterus)

A
  • The repair/ growth / shedding of uterine lining
  • Regulated by sex hormones released by ovaries
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Changes in a follicle during the
menstrual cycle

A
  • The ovary contains developing
    follicles.
  • Young follicles are called
    primary follicles.
  • Each primary follicle consists of
    a potential egg cell surrounded
    by a layer of smaller cells known
    as follicle cells.
  • Developing follicles will
    secrete estrogen, which
    stimulates growth and repair of
    uterine lining in the uterus
  • A primary follicle may develop
    into a Graafian follicle that
    contains a mature egg/ovum
    surrounded by follicle cells and
    a fluid-filled space.
  • The egg is now ready to be
    released into the oviduct.
  • Generally, one egg/ovum is released every month. The
    ovaries take turns to release an egg/ ovum.
  • Ovulation occurs when
    the Graafian follicle ruptures and releases the egg/ovum into the
    oviduct funnel.
  • Ovulation typically occurs
    on the 14th day from the
    start of menstruation.
  • After ovulation, the ruptured
    Graafian follicle develops
    into a corpus luteum.
  • The corpus luteum produces
    hormones (progesterone)
    that prepare the body for pregnancy.
  • If fertilisation does not
    occur, the corpus luteum will
    eventually break down.
    (menstruation starts and
    the cycle repeats)
30
Q

Describe and explain the changes in the concentration of oestrogen and progesterone during the menstrual cycle.

A
  • Day 1 to 5: Low levels of estrogen and progesterone during menstruation.
  • Day 6 to 13: Estrogen level increases as the follicle-stimulating
    hormone (FSH) from anterior pituitary causes follicles to
    develop and they secrete estrogen. Estrogen level is the highest a few days before ovulation. Progesterone remains low.
  • Day 14: High estrogen level stimulates luteinizing hormone for
    ovulation to occur.
  • Day 15 to 28: Formation of corpus luteum, corpus luteum produces high levels of progesterone and some estrogen.
31
Q

Fertile and infertile periods of the
menstrual cycle

A
  • Ovulation occurs on day 14.
  • The egg can be fertilised up to 48 hours (2 days) after its release from the ovary.
  • Sperms can live for three to four days in the female reproductive system.
  • Therefore, if sexual intercourse takes place between days 11
    to 16, there is a higher chance of fertilisation. This period is known as the fertile period.
  • The rest of the days make up the infertile period of the menstrual cycle.
32
Q

If fertilisation does not occur

A
  1. Egg/ovum breaks down
  2. High concentration of progesterone inhibits LH production. Lowered LH levels result in the corpus luteum breaking down.
  3. Progesterone is no longer secreted.
  4. Uterine lining breaks down
  5. Uterine lining is discharged together with blood through the vagina (This marks the beginning of menstruation.)
  6. Menstrual cycle repeats
33
Q

If fertilisation occurs

A
  1. The fertilised egg becomes a zygote, which develops mitotically into an embryo.
  2. The embryo embeds itself in the uterine lining and is implanted.
  3. The embryo secretes a hormone (human chorionic gonadotropin,
    hCG) that prevents the corpus luteum from breaking down.
  4. The corpus luteum continues to secrete estrogen and progesterone until the placenta forms and is able to take over the production of both hormones.
34
Q

How does one test for pregnancy?

A
  • During pregnancy, a hormone called human chorionic
    gonadotropin (hCG) is produced, which circulates in the blood and is also present in the urine.
  • The pregnancy test kit detects the presence of hCG in your urine. Most pregnancy test kits will be able to
    detect hCG between the fourth to fifth week of pregnancy.
35
Q

What would happen to an embryo if levels of progesterone suddenly drop during pregnancy?

A

Miscarriage can occur as the thickness of the uterine lining cannot be maintained for the
embryo to obtain sufficient nutrients and oxygen from the blood vessels.

36
Q

Sexual intercourse (copulation)

A
  1. Sexual arousal
  2. Penis becomes erect as blood is
    pumped into the spongy erectile tissue
  3. Semen containing millions of sperms is ejaculated into the vagina.
  4. Sperms swim up the oviduct to meet the egg.
37
Q

Fertilisation in humans

A
  1. During sexual intercourse, the penis is inserted into the vagina.
    2.
    * Semen (containing sperms and
    nutrients) ejaculated from the penis is deposited into the upper end of the vagina.
    * The sperms will begin to swim into the uterus and enter the oviduct.
  2. If an ovum is present in the oviduct, fertilisation may
    take place.
  3. Sperms deposited in the vagina during sexual intercourse travel up the uterus to the oviduct to
    fertilise the ovum released by the
    ovary.
  4. The fertilised egg (zygote) divides mitotically to form embryo, which moves into the uterus and becomes embedded in the uterine lining and is implanted.
38
Q

Fertilisation in humans

A

Fertilisation occurs when the haploid nucleus of sperm (n) fuses with the haploid nucleus of an ovum (n) to form a diploid zygote (2n).

39
Q

Process of fertilisation in humans

A
  • When the sperm makes contact
    with the egg, the sperm’s
    acrosome releases an enzyme
    that: disperses the follicle cells, and breaks down part of the egg
    membranes to allow the sperm
    to enter.
  • Only one sperm nucleus
    enters the egg
  • The haploid sperm nucleus fuses with the haploid egg/ovum nucleus, to form a diploid zygote (a fertilised egg).
  • As soon as a sperm enters the egg, the membrane of the egg changes such that no other sperms can enter.
  • The sperms that were unable to fertilise the egg eventually die.
40
Q

Describe the sequence of events that occur after a human egg cell is fertilised which enable it to develop and survive in the uterus 5

A

1) Implantation
* The cilia lining the oviduct sweep the fertilised egg towards
the uterus and peristaltic action of oviduct causes the zygote to travel along the oviduct and undergoes mitosis to form an embryo.
* Embryo takes typically five days to reach the uterus and may float freely in the uterus for two days before it(*embryo) implants into the uterine lining. The embryo secretes a hormone which prevents the corpus luteum from breaking down until the placenta is formed. Corpus luteum continues to secrete progesterone and estrogen until the placenta is ready to produce both hormones.
* Implantation refers to the event where the embryo becomes embedded in the uterine lining.

2) Development of the placenta
* After implantation, villi grow from the embryo into the uterine
lining to form placenta.
* Fetal blood capillaries are separated from the maternal blood by a thin layer of tissue. Placenta allows useful substances such as glucose, oxygen amino acids and mineral salts to diffuse from maternal blood into fetal blood and allows metabolic waste products eg CO2 and urea to diffuse from fetal blood into maternal blood to be excreted. Placenta allows antibodies in maternal blood to diffuse into fetal blood.
* The umbilical cord attaches the embryo to the placenta.

3) Development of the amniotic sac
* The amniotic sac is the
membrane that encloses
the embryo in a fluid-filled
space called the amniotic
cavity. Progesterone maintains the uterine lining during pregnancy.
* the amniotic fluid supports and cushions the fetus and act as shock absorbers. It allows the movement of the fetus to promote muscular development.

41
Q

Ectopic pregnancy

A

An ectopic pregnancy occurs
when an embryo implants and
grows outside the main cavity of the
uterus.
* An ectopic pregnancy most
often occurs in a fallopian tube.
* This type of ectopic
pregnancy is called a tubal pregnancy.

42
Q

Describe the blood transported by umbilical arteries and umbilical
vein.

A
  • To transport blood away from the heart and towards the fetus’s heart
  • Umbilical arteries carry deoxygenated blood while umbilical vein carries oxygenated blood.
43
Q

The fetal blood system

A
  • Fetal blood capillaries are not connected to the maternal blood capillaries.
  • The fetal blood capillaries are surrounded by the maternal blood spaces.
  • Diffusion of dissolved substances can occur across the maternal blood spaces.
44
Q

Why the fetal blood system is separated from the maternal blood system

A
  • the mother’s blood pressure would be too high for the fetus, and
  • the fetus’s and mother’s blood type may be different.
    If both blood systems were allowed to mix, the maternal antibodies would cause the fetus’s blood to agglutinate. This could be fatal to both the mother and fetus.
45
Q

Function of the placenta

A
  1. Allows oxygen and food substances (glucose and
    amino acids) to diffuse from
    the mother’s blood into the
    fetus’s blood
  2. Allows excretory products (urea and CO2) to diffuse from the fetus’s blood into the mother’s blood
  3. Produces progesterone to
    maintain and thicken the uterine lining
  4. Allows antibodies to diffuse
    from the mother’s blood into the fetus’s blood to protect the fetus against diseases
46
Q

Why is it not advisable for pregnant
mother to smoke / consume alcohol/ take drugs without doctors’
recommendation?

A

Harmful substances such as nicotine, alcohol and drug molecules are able to diffuse across the placenta from the mother to the fetus and cause severe damage to the fetus’s development.

47
Q

Functions of the umbilical cord

A

Umbilical vein: transports oxygenated blood and food
substances such as glucose and amino acids from the placenta to the fetus

Umbilical arteries: transport deoxygenated blood and metabolic waste products (urea and carbon
dioxide) from the fetus to the
placenta

The blood system of the mother and the fetus cannot mix due to possible agglutination and difference in blood pressure of the mother and the fetus which may kill the fetus.

48
Q

Functions of the amniotic fluid

A
  • found in amniotic sac which encloses the fetus in the amniotic cavity
    1. Allows the fetus to move freely
    during growth
    2. Lubricates and reduces friction in the vagina during birth
    3. Protects the fetus against physical injury by absorbing shock
    4. Supports and cushions the fetus
    5. Prevents temperature fluctuations
49
Q

STIs

A
  • A sexually transmitted infection (STI) is a disease that is spread through sexual intercourse.
  • STIs are caused by bacteria or viruses.
  • STIs can be transmitted from an infected person to an uninfected person via:
    1) semen,
    2) fluid in the vagina, and
    3) blood.
50
Q

Acquired Immune Deficiency
Syndrome (AIDS)

A
  • AIDS is a STI.
  • It is caused by the Human
    Immunodeficiency Virus (HIV).
  • HIV destroys the body’s immune system by attacking white blood cells, thus making infected individual prone to many
    infections
  • A person infected with AIDS is not able to produce sufficient antibodies to protect
    him or herself from other infections.
  • Infections that are normally mild may become fatal for a person with AIDS.
51
Q

Symptoms of AIDS

A
  1. Severe diarrhoea that lasts for months
  2. Pneumonia
  3. Kaposi’s sarcoma
  4. Brain infection
  5. Widespread tuberculosis
  6. Chronic fever
52
Q

Modes of transmission of AIDS and HIV

A
  1. Unprotected sexual intercourse with an infected person
  2. Passed from mother to fetus
    during pregnancy
  3. Blood transfusion with blood from an infected person
  4. Sharing of hypodermic needles
    with an infected person
53
Q

How to prevent HIV infection

A
  1. Do not have sex
  2. Keep to one sex partner.
  3. Use a condom when having sexual intercourse.
  4. Do not abuse drugs as drug addicts tend to share needles.
  5. Do not share instruments that can break skin and get contaminated with blood (e.g. razors, toothbrushes).
  6. Make sure that the needles used
    in acupuncture, ear-piercing and/or tattooing are sterilised.
54
Q

Describe the menstrual cycle from Day 1 to Day 14 and explain the roles of the hormones in stimulating the changes. [6]

A

Day 1-5 (Menstrual flow stage)
● Menstruation occurs. Both oestrogen and progesterone level are low and menstruation occurs as uterine lining could not be maintained. [1]
● During menstruation, the uterine lining breaks down and flows out through the vagina. Damage to blood vessels causes bleeding. [1]

Day 6-13 (follicle stage)
● Follicle in one of the ovaries start to develop in response to follicle stimulating hormone from pituitary gland. [1]
● The developing follicle secrete hormone, oestrogen for the repair and growth of the uterine lining.[1]
Level of estrogen is the highest.

Day 14 (ovulation stage)
● Follicle matures to become Graafian follicle
● Surge /increase in oestrogen production caused the pituitary gland to release the luteinizing hormone. [1]
● Ovulation occurs whereby a mature ovum is released from the Graafian follicle.[1]

Corpus Luteum stage (day 15 - 28)
* Progesterone prepares the uterine lining for the fertilised egg by causing it to thicken further, and supplying it with blood capillaries.
* Progesterone inhibits ovulation

55
Q

Describe the early development of the zygote after fertilisation has taken place. [4]

A

The fertilised egg, zygote continues to divide by mitosis to form a ball of cells called an embryo. [1]
The embryo travel / move down the oviduct into the uterus by the
contraction of the oviduct muscles via peristalsis [1] and with the help of the cilia. [1]
Implants itself into the uterine lining/uterus wall. [1]

56
Q

Describe and explain the adaptations and functions of the placenta during pregnancy. [4]

A

● The placenta produces progesterone to maintain the uterus lining during pregnancy.
● It also allows nutrients such as glucose, amino acids and oxygen to diffuse from the mother’s blood to that of the blood of the fetus.
● Metabolic waste product such as urea and carbon dioxide diffuse from the fetus’s blood to the mother’s blood.
● Antibodies from the mother’s blood can diffuse into the to the fetus’s blood to protect the fetus from diseases.
● The blood system of the mother and fetus are segregated and they cannot mix to prevent agglutination and difference in blood pressure of the mother and the fetus, which may potentially kill the fetus.

57
Q

Prostate gland

A

Produces alkaline, milky fluid that contains nutrients and enzymes which nourish and activates the sperms and helps them to swim towards the egg.

58
Q

Fertile period

A

An egg can survive for 2 days whereas sperms can live for 3 days. Ovulation usually occurs on day 14. Chance of getting pregnant is highest betw days 11 to 16. The rest of the days make up the infertile period.6

59
Q

Describe fertilisation and early development of the zygote

A
  1. Semen is deposited into the vagina.
  2. Sperms travel up thru thee cervix and uterus and enters the oviduct
  3. When sperms reach the egg, sperms release acrosome enzymes to break down the egg membrane.
  4. Only 1 sperm nucleus enters the egg
  5. When the haploid nucleus of sperm fuses with the haploid nucleus of egg to form a diploid zygote, fertilisation occurs. Fertilisation takes place in the oviduct.
  6. The zygote moves from the oviduct to the uterus. It is swept by cilia and peristalsis of the oviduct muscles.
  7. The zygote undergoes mitosis to form a ball of cells called the embryo, which gets implanted in the uterine lining on the wall of the uterus.
60
Q

Define implantation

A

The process where y the embryo embeds itself in the uterus lining

61
Q

If fertilisation occurs, what will happen to the thickness of the uterine lining after day 28? Explain your answer. [3]

A

If fertilisation occurred, the ovary continues secreting oestrogen and progesterone, keeping their levels high.

Hence, these hormones maintain the uterine lining even after day 28, in preparation for the implantation of the embryo.

The lining does not break down, and there is no menstruation.

62
Q

On which days of the menstrual cycle is the woman most fertile? Explain your answer. [4]

A

Ovulation occurs on day 14, where a mature ovum is released from an ovary into an oviduct.

Sperm survive up to 4 days, so if sexual intercourse occurs on day 10, sperm can still meet ovum on day 14 immediately upon ovulation, resulting in fertilisation.

Ovum can survive up to 1 day, so if sexual intercourse occurs at the start of day 15, sperm can still meet the ovum.

Thus the fertile period, the days where sexual intercourse would lead to the highest chance of pregnancy, is from day 10 to 15.

63
Q

Describe the sequence of events that occur after a human egg cell after it is fertilised, which enable it to develop and survive in the uterus. [5]

A

After fertilisation, the zygote is moved from the oviduct towards the uterus, by peristaltic action of the oviduct walls and the sweeping action of cilia.

Meanwhile, the zygote divides by mitosis into an embryo,

Which embeds itself into the uterine lining during implantation, where it develops into a foetus.

(along with any 2 more points):

Finger-like projections called villi, containing the blood vessels from the embryo, grow into the uterine lining, forming the placenta.

The placenta secretes progesterone and oestrogen, maintaining the thickness of uterine lining.

In the placenta, oxygen and nutrients diffuse from maternal to foetal capillaries, and are delivered to the foetus via the umbilical cord, while metabolic waste products such as urea and carbon dioxide are removed.

The amniotic sac develops, containing amniotic fluid that protects foetus from physical injury/allows for movement for muscular development/trains the foetus’ digestive system.

64
Q

Describe the functions of the placenta during pregnancy. [4]

A

The placenta is made up of the embryonic villi and the uterine wall. Fetal blood capillaries are separated from the maternal blood by a thin layer of tissue.

The placenta secretes oestrogen and progesterone, to maintain the thickness of the uterine lining throughout pregnancy.

Within the placenta, oxygen and nutrients diffuse from maternal to foetal capillaries, while metabolic waste products such as urea and carbon dioxide diffuse from foetal to maternal blood vessels.

The placenta allows some antibodies to diffuse from maternal to foetal blood, giving the foetus immunity to those diseases.

65
Q

Explain why the maternal and foetal blood vessels are not directly connected. [2]

A

Maternal and foetal blood types may be incompatible, and direct mixing of blood would lead to agglutination of red blood cells which is dangerous both mother and foetus.
The mother’s blood pressure is higher than that of the foetus, which may burst foetal blood vessels if they were connected.

66
Q

Describe the ways in which HIV can be transmitted. [4]

A

Unprotected sexual intercourse, where semen containing HIV comes into contact with the mucous membrane of an uninfected female’s vagina.
Or when vaginal fluids containing HIV come into contact with the mucous membrane of an uninfected male’s urethra.
By sharing contaminated needles, such as between drug addicts.
By blood transfusion with blood from an infected person.
During pregnancy, where the virus travels from an infected mother to the foetus.

67
Q

Describe the early development of the zygote after fertilisation has taken place. [4]

A

The fertilised egg, zygote continues to divide by mitosis to form a ball of cells called an embryo. [1]
The embryo travel / move down the oviduct into the uterus by the
contraction of the oviduct muscles via peristalsis [1] and with the help of the cilia. [1]
Implants itself into the uterine lining/uterus wall. [1]

68
Q

Suggest a role for the cilia found in oviduct. [1]

A

Rhythmic movement of cilia helps sweep the embryo towards the uterus.

69
Q

Describe the process of fertilisation and outline the early development of the embryo. [6] (until implantation)

A

Fertilisation:
Millions of sperms are released during ejaculation and deposited in the vagina. Sperms travel from the vagina up through cervix and uterus, to the oviduct. One matured ovum is released by the vary every month which contains a nucleus and an abundant cytoplasm with stored nutrients. Haploid nuclei of a sperm fuses with a haploid nuclei of an ovum, forming a diploid zygote at the oviduct. The zygote undergoes mitosis to form an embryo which is made up of a hollow ball of cells. Cilia lining sweeps the embryo and peristaltic movement of oviduct allows the travel of embryo to the uterus for implantation in the uterine lining. The embryo reaches uterus 5 days after fertilisation and may float freely in the uterus before implantation for 2 days. On day 7, embryos implants into uterine lining.

70
Q

Describe 2 functions of the ovaries in a healthy young woman who is not pregnant. [3]

A

The ovaries produce and release oestrogen to maintain the secondary sexual characteristics in the young woman and enable the repair of the uterine lining after menstruation

The ovaries produce ovum and releases the matured ovum during ovulation in the menstrual cycle of the woman on a monthly basis.

The ovaries produce and release progesterone to maintain and thicken the uterine lining after ovulation in preparation fro the implantation of an embryo.

71
Q

Compare the progesterone levels in the pregnant woman to the progesterone levels expected in a healthy young woman who is not pregnant during the same 9 months. [4]

A

Progesterone levels in the pregnant woman from month 0-1 is similar to the maximum progesterone levels of the woman who is not pregnant before she starts menstruating

The non-pregnant woman’s progesterone level decreases rapidly prior to menstruation, leading to the breakdown of the uterine lining during menstruation. However, the progesterone levels of the regnant woman r maintained in months 0-1, before increasing from x to y units in months 8-9. Progesterone is needed for the maintenance of a thick uterine lining to provide ample blood supply for the formation of the placenta and development of the foetus.

72
Q

Effects of estrogen and progesterone

A

Estrogen: high level needed for ovulation; repairs the uterus lining

Progesterone: high level needed to stop development of more ova; maintains the uterine lining

biology (18 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions