Chapter 15 Reproduction In Humans Flashcards
What is a gamete?
A reproductive cell of an animal or plant
Define ovaries:
Organs that produce female gametes
Define oviducts (fallopian tubes):
Tubes leading from the ovaries to the uterus
Define uterus:
The organ in which a fetus develops before birth (womb)
Define cervix:
A narrow opening leading from the uterus to the vagina
Define vagina:
Opening from the uterus to the outside of the body
Are the oviduct directly connected to the ovaries?
No
What is the uterus walls made of?
Thick walls of muscle
What tube is in front of the vagina?
Urethra - opening from the bladder
What tube is behind the vagina?
Rectum
What does the female reproductive system consist of?
1) ovaries (produce gamete)
2) ovum (female gamete in ovaries)
3) oviducts (tubes that lead from the ovaries to the uterus)
4) uterus (where fetus develops)
5) cervix (opening from uterus to vagina)
6) vagina (opening from uterus to outside of body)
Define testes:
singular: testis
Organs in which the male gametes (sperm) made
Define scrotum:
The sac that contains the testes
Define sperm duct:
A tube that transports sperm from the testis to the urethra
Define penis:
Organ containing the urethra through which urine and sperm of carried
Define prostate gland:
Organ that produces a nutritious fluid (semen) in which sperm are transported
Define epididymis:
Part of the testes in which sperm are stored
What is another name for male gamete, sperm?
Spermatozoa
What does the male reproductive system consist of?
1) 2 testes (produce gamete)
2) sperm (male gamete in testes)
3) scrotum (sacs of skin that contain each testis)
4) sperm duct (tube that carries sperm from each testis to join up with the urethra)
5) penis (urethra travels down penis to tip where it opens)
6) prostate gland (where the sperm duct joins the urethra) (makes semen)
How many eggs mature at a time when a girl reaches puberty?
Usually only one develops at a time
What is the egg made off?
A single cell
What is ovulation?
The release of an egg from an ovary
How often does ovulation happen?
Once a month
From when on a sperm made?
From puberty onwards
Where is sperm stored?
Epididymis
How do sperm develop?
It develops from cells in the walls of the tubules in the testes
Why are the testes positioned outside the body?
→ sperm production is heat sensitive
→ if they get too hot, the cells in the tubules will not develop into sperm
→ sperm will be cooler if positioned outside of the body
What type of cells are egg and sperm cells?
Haploid cells
How is eggs and sperm made in the ovaries and testes?
They are made when the cells divide by meiosis
How many chromosomes are in the nucleus of the human egg and human sperm?
There is a single set of 23 chromosomes in the nucleus of the human sperm and egg
Define flagellum:
plural: flagella
A long, whip-like ‘tail’ structure found on sperm cells, used for swimming
Define acrosome:
Structure containing digestive enzymes, in the head of a sperm cell
What is the structure and function of the acrosome in the sperm cell?
Vesicle containing enzymes → to dissolve through the jelly surrounding the egg cell
What is the structure and function of the nucleus in the sperm cell?
Contains mitochondria → to release energy for swimming
What is the structure and function of the sperm cell?
head
Contains acrosome → contains enzymes → dissolve a way through the jelly surrounding the egg cell
Contains nucleus → mitochondria → release energy for swimming
middle piece
Contains middle piece → to release energy for swimming
tail
Flagellum → for swimming
What happens after ovulation?
1) An egg is caught in the funnel of the oviduct
2) The egg travels towards the uterus
3) Cilia lining the oviduct help to move it along
4) Muscles in the wall of the oviduct also helped to move it, by producing gentle rippling movements
How long before the egg dies?
If the egg is not fertilised by a sperm within 8 to 24 hours after ovulation it dies
How is the sperm board as close as possible to the egg?
The penis is placed inside of the vagina so that sperm travels directly into the vagina
How does sperm travel out of the penis?
1) The walls of the tubes containing the sperm contract rhythmically
2) The wave of contraction begins in the testes, travels along the sperm duct, and into the penis
3) The sperm are squeezed along the tubes, out of the man’s urethra and into the woman’s vagina
Why is it important that the sperm is carried in the semen?
The liquid part of semen is produced by the prostate gland
It contains sugars and other nutrients → provide sperm within energy
Where is the semen deposited?
At the top of the vagina near the cervix
What is the pathway that the sperm swims?
Testes → sperm duct → urethra → vagina → cervix → uterus → oviducts
How fast do sperm swim?
4mm per minute
How many sperm actually make it to the oviducts?
Only some out of 1 million
Briefly describe what happens when the sperm cell comes into contact with the egg cell:
1) Acrosome is activated
2) Releases digestive enzymes
3) Enzymes digest the jelly coat of the egg cell
4) The head of the sperm is able to push through and get into the cytoplasm of the egg
5) The flagellum is left outside
6) The nucleus of the sperm fuses with the nucleus of the egg (fertilisation)
What happens when a successful sperm enters the egg?
The egg membrane and jelly coat become impenetrable → no other sperm can get in → they all die
How is a zygote formed?
When an egg nucleus and sperm nucleus have fused together
What happens to the zygote after it is formed?
Continues to move down the oviduct (in direction of uterus)
As it moves it divides repeatedly → forming a ball of cells (embryo) after several hours
Define embryo:
The ball of cells that is produced by repeated division of the zygote
What from the egg does the embryo contain?
The nutrients and yolk
How long does it take for the embryo to reach the uterus?
Several hours
How many cells does the embryo consist of of when it finally reaches the uterus?
It is a ball of 16 or 23 cells
How is the lining of the uterus fitting for implantation?
The lining is thick and spongy, and the embryo just sinks into it
Define implantation:
Attachment of the embryo to the lining of the uterus
What is the placenta?
An organ that connects the growing fetus to its mother, in which the blood of the fetus and mother of all close together so that materials can be exchanged between them
What is a fetus:
An unborn mammal, in which all the organs have been formed
Define umbilical cord:
Structure containing blood vessels that connects the fetus to the placenta
True/false: The cells in the embryo stop dividing after it has sunk into the lining of the uterus.
False
Name 3 characteristics of the placenta and its function:
1) soft
2) dark red
3) has villi that fit closely into the uterus wall
F) this is where substances are exchanged between the mothers blood and the embryo’s blood
How long does it take for the embryo to develop most of its organs?
11 weeks
When is the embryo called a fetus?
After about 11 weeks
How is the placenta joined to the fetus?
By the umbilical cord
Describe the structure and function of the umbilical cord:
Consists of:
A) 2 arteries → take blood from the fetus into the placenta
B) vein → return the blood to the fetus
True/false: The mother and embryos blood does not mix.
Give a reason for your answer
True, the mother and embryo blood is separated by the placenta
How can materials successfully be exchanged between the placenta and uterus?
Placenta
1) contains tiny capillaries filled with the fetus’s blood
2) very thin → so placenta and uterus are brought very close together
Uterus
1) lining of uterus contains large spaces filled with the mother’s blood
By means of what process does oxygen and dissolved nutrients from the mothers blood move into the placenta, into the fetus’s blood?
Diffusion
Briefly describe how the fetus receives it nutrients and oxygen:
Oxygen and dissolved nutrients from the mother’s blood diffuse across the placenta into the fetus’s blood and are carried along the umbilical cord to the fetus
How is unwanted substances removed from the fetus’s blood?
Carbon dioxide and other excretory products diffuse in the other direction of the mothers nutrients diffusing into the blood, and all carried away in the mother’s blood
How big is the placenta by the time the baby is born
Placenta is a flat disk
12cm in diameter
3cm thick
Define amniotic sac:
A tough membrane that surrounds a developing fetus in the uterus
Define amniotic fluid:
Liquid secreted by the amniotic sac, which supports and protects the fetus
Why is amniotic fluid important?
Allows the fetus to freely move its arms and legs, which help the muscles and skeleton to develop correctly
How long before the fetus is ready to be born?
Nine months
What is the first sign that a woman is about to give birth?
The amniotic sac breaks because of contractions of muscles in the uterus wall
Amniotic fluid is released so that it flows into the vagina
Explain the difference between a fetus and an embryo:
An embryo is a ball of undifferentiated cells, formed by repeated division of the zygote. A fetus develops from an embryo when the cells have formed different tissues and organs.
List five substances that are transferred from the mothers blood to the embryo blood in the placenta:
oxygen, glucose, amino acids, fatty acids, glycerol, minerals (or named minerals), vitamins (or named vitamins), water
Name two substances that are transferred from the embryo’s blood to the mother’s blood:
Carbon dioxide
Urea
Define puberty:
The time at which sexual maturity is reached
What is the main reproductive hormone in men?
Testosterone
What is the main reproductive hormone in woman?
Oestrogen
Progesterone
What happens during adolescence?
Sperm production begins in a boy
Ovulation begins in a girl
What does testosterone cause in men:
1) Facial hair
2) Pubic hair
3) Broadening shoulders
4) General muscular development
5) Deepening voice
What characteristics does oestrogen cause?
1) breasts grow bigger
2) pubic hair
3) hips grow wider
Define follicle:
The structure within an ovary, in which an egg develops
Define menstruation:
The loss of the broken down uterus lining through the vagina
What 4 hormones control the occurring event of the menstrual cycle
1) oestrogen
2) progesterone
3) FSH
4) LH
Where is oestrogen and progesterone secreted?
Ovaries
What does the pituitary gland secrete?
FSH
LH
Define pituitary gland:
A small endocrine gland attached to the underside of the brain
Define FSH:
Follicle stimulating hormone, a hormone secreted by the pituitary gland which causes a follicle to develop in an ovary
Define LH:
Luteinising hormone, hormone secreted by the pituitary gland that causes of ovulation to happen
Define corpus luteum (yellow body):
Structure that develops from the empty follicle after an egg has been released from an ovary
What does the hormone progesterone do?
Keeps the lining of the uterus thick and spongy, ready to receive a fertilised egg
Why do no more follicles develop in the ovary during pregnancy?
Because progesterone levels are very high and inhibits the secretion of FSH 
What is the hormone oestrogen?
Causes the lining of the uterus to become thicker and better supplied with blood
Define sexually transmitted infection (STI):
Disease caused by pathogens that are transmitted during sexual contact
Define AIDS:
Acquired immune deficiency syndrome
A disease caused by HIV, which destroys white blood cells and therefore reduces the ability of the immune system to defend against other pathogens
Define HIV:
The human immunodeficiency virus
What type of cells does HIV infect?
White blood cells, in particular type called T cells
How can HIV be transmitted?
Through sexual contact
Direct blood to blood contact
Breastfeeding
How can you reduce the spread of HIV?
Trace contacts
Use condoms
Using antiretroviral drugs
Avoiding sharing needles
