Chapter 18 - Reproduction In Humans

Question 1

What are 2 functions of the testes?

Answer 1

1) produce sperms

2) produce testosterone that is responsible for development and maintenance of secondary sexual characteristics in males

Question 2

What is the function of epididymis?

Answer 2

Store inactive sperms from testis before they are released into sperm duct

Question 3

What is the function of the spermatic cord?

Answer 3

Supply blood to testis

Question 4

What are the functions of the prostate gland, Cowper’s gland and Seminal vesicle?

Answer 4

Produce alkaline, milky fluid that contains nutrients and enzymes which nourish and activate the sperms, helping them swim towards the egg.
(Sperm+fluid=semen)

Question 5

What is the function of the scrotum(scrotal sac)?

Answer 5

They are located outside the body cavity to help maintain a lower temperature for the development of sperms.

Question 6

What is the function of sperm duct(vas deferens)?

Answer 6

Carry sperms from testes to urethra.

Question 7

What is the function of the sphincter muscles in context of sexual reproduction?

Answer 7

Prevents urine from exiting the body during ejaculation.

Question 8

What is the function of the penis?

Answer 8

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

Question 9

How does an erection occur?

Answer 9

Blood is pumped into the penis faster than it can return to the bloodstream via the veins. The spongy tissue in the penis thus fills with blood (vasodilation).

Question 10

What is the function of the urethra in context of sexual reproduction?

Answer 10

Passes sperms out of the body

Question 11

How is the sperm adapted for its function?(3)

Answer 11

1) its head contains an acrosome that contains enzymes for breaking down part of the egg membrane for sperm penetration
2) it contains numerous mitochondria in the middle piece, providing energy for the sperm to swim towards the egg.
3) its tail (flagellum) beats to enable the sperm to swim towards the egg

Question 12

What is the function of the ovary?(2)

Answer 12

1) produce eggs

2) produce oestrogen and progesterone

Question 13

What is the function of oviduct(fallopian tube)?(2)

Answer 13

1) transport eggs to uterus by peristalsis of muscular wall and sweeping action of the cilia. It has a funnel-like opening close to the ovary, making it easier for eggs to enter the oviduct.
2) site of fertilization

Question 14

What is the function of the uterus?(2)

Answer 14

1) site of implantation of embryo

2) site of fetus development during pregnancy

Question 15

What is the uterine lining(endometrium)?

Answer 15

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

Question 16

What are 2 functions of cervix?

Answer 16

1) allows menstrual blood to flow out into vagina during menstruation
2) enlarges to allow passage of fetus during birth

Question 17

What is the function of the vagina?(2)

Answer 17

1) birth canal

2) where semen is deposited during sexual intercourse

Question 18

What is the structure of the egg?(3)

Answer 18

1) large nucleus containing one haploid set of chromosomes
2) abundant cytoplasm which may contain a small amount of yolk
3) cell surface membrane that is surrounded by an outer membrane

Question 19

What are 4 differences between a male and female gamete in humans?

Answer 19

1) structure - sperms have a head, middle piece and a tail, while eggs are spherical
2) chromosomes - sperms contain either X or Y chromosome while egg contains only one X chromosome
3) motility - sperm is motile and has a tail that enables it to swim towards the oviduct, while the egg is non motile. There is only passive movement of egg along the oviduct due to peristalsis and sweeping
4) numbers - numerous sperms are produced throughout life from puberty onwards, and a large amount of sperms are released per ejaculation. However, the number of eggs are determined at birth, and only one egg is released per month.

Question 20

Define puberty.

Answer 20

Puberty is the stage of human growth and development in which a person becomes physically mature.

Question 21

What are 4 signs of puberty in males?

Answer 21

1) facial hair begins to grow and hair appears in the pubic region and under armpits
2) penis and testicles increase in size
3) larynx enlarges and voice deepens
4) production of sperms begin

Question 22

What are 4 signs of puberty in females?

Answer 22

1) hair appears in the pubic region and under armpits
2) breasts and uterus enlarge
3) hips broaden
4) menstruation and ovulation start

Question 23

What happens on day 1-5 of the menstrual cycle?

Answer 23

1) the first day of menstruation is the first day of the menstrual cycle.
2) the uterine lining breaks down and flows out through the vagina
3) the anterior pituitary gland secretes follicle-stimulating hormone(FSH) into the bloodstream.

Question 24

What happens on day 6-13 of the menstrual cycle? (2-2,2-3)

Answer 24

1) FSH takes effect, stimulating
a) the development of follicles int he ovaries. One follicle develop into a Grafiaan follicle (contains egg surrounded by follicle cells and fluid-filled space) in one of the ovaries.
b) follicles in ovaries to secrete oestrogen
2) Oestrogen takes effect,
a) it causes the repair and growth of the uterine lining. The uterine lining becomes thick and spongy with blood vessels.
b) when oestrogen is present in high concentration, it inhibits FSH production, preventing the maturation and development of more follicles
c) oestrogen at high concentration also stimulates the pituitary gland to secrete luteinising hormone (LH).

Question 25

What happens on day 14 of the menstrual cycle?(3)

Answer 25

Luitenising hormone (LH) takes effect,

1) causing ovulation. The Graafian follicle ruptures and releases the egg into the oviduct
2) causing formation of the corpus luteum from the remains of the Graafian follicle
3) corpus luteum secretes progesterone and some oestrogen, preparing the body for pregnancy

Question 26

What happens on day 15-28 of the menstrual cycle?(3)

Answer 26

Progesterone takes effect,

1) maintains the uterine lining by causing it to thicken further and be richly supplied with blood capillaries, preparing it for the implantation of the embryo
2) inhibits ovulation and FSH production.
3) fertilization might occur. If not, the cycle repeats.

Question 27

What happens if no fertilization occurs?(6)

Answer 27

1) the ovum (egg) breaks down.
2) eventually, LH production is inhibited by high concentration of progesterone in the blood. The drop in LH level in the blood causes corpus luteum to break down
3) when the corpus luteum breaks down, progesterone is not secreted.
4) without progesterone, the thickened uterine lining cannot be maintained and breaks down
5) the lining flows from the uterus together with some blood through the vagina.
6) FSH is produced again by the pituitary gland and the cycle repeats.

Question 28

What happens if fertilization occurs? (4)

Answer 28

1) the fertilized egg becomes a zygote. The zygote divides repeatedly and develops into an embryo.
2) the embryo embeds itself in the uterine lining
3) the embryo secretes a hormone which prevents the corpus luteum from breaking down until the placenta is formed
4) the corpus luteum continues to secrete progesterone and oestrogen until the placenta is able to take over the production of progesterone and oestrogen.

Question 29

When is the fertile period of a female?

Answer 29

The egg can survive for 2 days while the sperm can live for 3 days. Day 11-16 has the highest chances of getting pregnant.

Question 30

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

Answer 30

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

Question 31

How does fertilization take place?

Answer 31

1) semen is deposited in the vagina. Sperms travel up through the cervix and uterus, and enters the oviduct
2) when sperm makes contact with the ovum, the sperm’s acrosome releases an enzyme, dispersing the follicle cells and breaking down part of the membrane to allow the sperm to enter
3) only one sperm nucleus enters the egg.
4) the haploid sperm nucleus fuses with the haploid egg nucleus, forming a diploid zygote.

Question 32

How does the embryo develop?(3)

Answer 32

1) implantation
2) development of placenta
3) development of amniotic sac

Question 33

What happens during implantation?(4)

Answer 33

1) the cilia lining of the oviduct sweeps the fertilized egg towards the uterus. Peristaltic movements in the wall of the oviduct also help move the zygote to the uterus
2) as the zygote travels along the oviduct, it undergoes mitosis to form an embryo
3) it takes 5 days for the embryo to reach the nucleus, and the embryo may float freely in the uterus for 2 days
4) eventually, the embryo becomes embedded in the uterine lining. (Implantation)

Question 34

What happens during development of the placenta? (3)

Answer 34

1) after implantation, finger-like projections known as villi grow from the embryo to the uterine lining.
2) the embryonic villi and the uterine lining make up the placenta.
3) a tube known as the umbilical cord attaches the embryo to the placenta

Question 35

What happens during the development of the amniotic sac?

Answer 35

The amniotic sac begins to develop at about the same time as the placenta. It encloses the embryo in a fluid-filled space known as the amniotic cavity, with amniotic fluid in the amniotic cavity.

Question 36

What are 6 functions of the amniotic fluid in the amniotic sac?

Answer 36

1) supports and cushions fetus before birth
2) absorb shock if the mother falls
3) protects fetus from physical injury
4) lubricates and reduces friction in the vagina during birth
5) allows fetus to move freely during growth
6) prevents temperature fluctuations

Question 37

Why is the fetal blood system separated from the maternal blood system?(2)

Answer 37

1) possible agglutination. Maternal antibodies will cause the fetus’ blood to agglutinate, fatal to both mother and fetus
2) difference in blood pressure of mother and fetus may kill the fetus.

Question 38

How does exchange of dissolved substances occur between mother and fetus?

Answer 38

Fetal capillaries are surrounded by maternal blood spaces. In the placenta, blood capillaries of the fetus are separated from the mother’s blood system by a thin layer of tissue. Diffusion of dissolved substances occur across the layer of tissue.

Question 39

What are 4 functions of the placenta?

Answer 39

1) allows nutrients such as glucose, amino acids and oxygen to diffuse from the mother’s BLOOD to the fetus’ BLOOD.
2) allows metabolic waste products such as urea and carbon dioxide to diffuse from fetus’ BLOOD to mother’s BLOOD.
3) allows antibodies (not bloodtype antibodies) to diffuse from mother’s BLOOD to fetus’ BLOOD to protect fetus from diseases.
4) take over function of corpus luteum and produce progesterone to maintain the uterine lining

Question 40

What are 2 functions of the umbilical cord?

Answer 40

1) umbilical vein (towards) transports oxygenated blood and food substances such as glucose and amino acids from placenta to fetus
2) umbilical arteries (away) transport deoxygenated blood and metabolic waste products like urea from fetus to placenta.

Question 41

How is the human immunodeficiency virus (HIV) / STI transmitted?(4)

Answer 41

1) having sexual intercourse with an infected person, where the semen or fluid in vagina comes in contact with mucuous membrane in vagina/urethra
2) sharing hypodermic needles with an infected person
3) blood transfusion with blood from an infected person
4) during pregnancy when an infected mother passes the virus to her fetus

Question 42

What are 6 symptoms of AIDS?

Answer 42

1) chronic fever
2) severe diarrhoea that lasts for months
3) pneumonia
4) Kaposi’s sarcoma (cancer of blood vessels)
5) brain infection
6) widespread tuberculosis

Question 43

How to prevent HIV infection?(5)

Answer 43

1) keep to one sex partner/do not have sex
2) use a condom during sexual intercourse
3) do not abuse drugs as drug addicts tend to share needles
4) do not share instruments that can break skin and get contaminated with blood
5) sterilize needles before use