Unit 3.3 The Reproductive System Flashcards
Which system functions to ensure that survival of the species and the genes of an individual are passed on to the next generation?
The reproductive system!
What do specialised sex cells or gametes contain?
Half of the chromosome number of the adult.
What happens to these gametes at fertilisation?
At fertilisation these gametes fuse together to form a new, genetically unique cell known as the zygote.
What does the fusion of two gametes producing a genetically unique cell introduce to a species?
Genetic variation which is key to the survival of a species.
In humans, what are the primary reproductive organs or gonads? what are these responsible for?
The ovaries and testes responsible for producing the gametes and for production of hormones.
What are the female and male gametes?
The female gametes are the egg cells and the male gametes are the sperm cells or spermatozoa
What two things are hormones important in the development of?
In both sexes the hormones are important i the development of secondary sexual characteristics (for example facial hair and deep voice in men or wider hips and breasts in women) and in the development and function of the reproductive system.
What are the structures called that sustain or transport the gametes and nurture the developing foetus?
All other organs, ducts and glands in the reproductive system are considered secondary or accessory reproductive organs.
What is the role of the female in mammalian reproduction?
- To produce a relatively small number of large gametes (eggs) ready to be fertilised by a male.
- To provide the developing embryo with food, oxygen and protection and remove its waste products.
- To give birth to the foetus at the end of pregnancy
- Too provide the baby with food (milk) for a period of time.
What makes up the female reproductive system?
The vagina, cervix, uterus, fallopian tubes (oviduct) and ovaries.
What is the vagina?
A fibro-muscular tube about 7 to 9 cm long which can stretch a great deal during the birth process. Its structure varies with age and hormonal activity.
What does the vagina produce?
Lubricating sections.
What is the vagina home to that helps maintain vaginal health?
Millions of bacteria.
What is the pH of the vagina? what helps maintain this? Why this pH?
Lacterobacilli produce lactic acid which helps to maintain an acid pH in the vagina of less than 4.5. This reduces the chances of invasion by external bacterial pathogens and fungi.
What is the cervix? what is its size and function?
The cervix is the entrance to the uterus which extends into the vagina. It is about 3cm long and 2-2.5cm in diameter. with an opening normally less than 1cm but during childbirth expands to allow passage of the baby (about 10cm diameter) after delivery the cervix returns to normal in a very short time.
What is the cervix covered in for much of the monthly menstrual cycle?
thick acidic mucus to prevent bacteria from entering the uterus.
What happens to the cervix mucus during the fertile stage of the cycle? What is this thought to help?
It becomes thinner and plentiful with an alkaline pH - this is thought to help the sperm move through the cervix into the uterus. After ovulation the mucus thickens and becomes acidic again.
What is the uterus?
The organ in which a baby grows and develops.
What is the uterus made from?
The body and fundus (top section) of the uterus have thick walls of smooth muscle.
What is the body of the uterus lined with?
The body of the uterus is linked by endometrium which thickens and becomes more vascular each month in preparation of pregnancy
What happens in the uterus after fertilisation?
The developing embryo implants itself into the endometrium where it continues to grow and develop in the uterus and after 10 week is known as a foetus.
What happens if fertilisation does not take place?
The thickened endometrium is lost during menstrual bleeding
What are the fallopian tubes (oviducts)? How long are they? what are they lined with?
These are found either side of the uterus and are the site of fertilisation of the ovum by the sperm. they are about 10-12 cm long and linked with specialised ciliated epithelium.
When the ovum is released from the ovary how is it guided into the fallopian tubes?
By the wide ends of the tubes known as the funnels of the oviduct or the fimbria.
What are ovaries? What are they the source of? what do they produce?
These are the primary sex organs, the source of mature ova and the endocrine organs that produce the steroid hormones (oestrogen and progesterone) that prepare the endometrium for conception and maintain pregnancy if fertilisation occurs. They also support the female secondary sex characteristics such as breasts and body shape.
At birth, what does each of the ovaries contain?
About 1 million follicles containing potential ova and no new ones are developed after birth - these cells are called primary oocytes.
How many ova will be released during a woman’s lifetime?
around 400-500 ova will be ovulated during a womans lifetime at the rate of one per month.
In the ovaries, where are the immature ova found?
In structures known as follicles.
What happens to these follicles each month?
Several of these follicles mature each month and hen they are mature they are about 1.5cm in diameter.
What does the follicle develop as it matures?
It develops cells which secrete oestorgen and small amounts of progesterone just before ovulation
What forms around the oocyte?
A thick layer of material known as the zona pellucida.
What is the mature follicle also known as?
A Graafian follicle.
What accessory reproductive organ is fully functional in the female and present but underdeveloped in the male?
The mammary glands.
When and why do the female mammary glands develop and increase in size?
During puberty and in response to the hormone oestrogen.
What are the mammary glands modified versions of and part of which system?
they are modified sweat glands that are actually part of the skin system.
What does each mammary gland consist of?
15-20 lobes which are separated from each other by connective tissue and fat.
What is within each lobe? What do these produce?
Within each lobe are lobules which contain clusters of alveolar glands - these produce milk when a woman is lactating.
What opens to the outside via the nipple to release milk?
The lactiferous ducts
What does human milk consist of?
88% water, 7% lactose, 4% fat, 1% protein and various ions, principally calcium, sodium, potassium, phosphate and chloride. A wide range of growth factors is also secreted in breast milk along with antibodies to protect the baby from some diseases - it is the ideal food for human babies.
The female reporductive system prepares for pregnancy in a 4 week cycle known as what?
The menstrual cycle.
What happens in each cycle?
Several follicles mature, the lining of the uterus builds up in preparation of a pregnancy, an ovum is released from the follicle that matures first and then if it is not fertilised, the ovum dies and is lost with the lining of the uterus as the whole cycle begins again.
What 4 different hormone sis the menstrual cycle under control of?
Follicle stimulating hormone (FSH) and luteinising hormone (LH) from the pituitary gland in the brain and oestrogen and progesterone from the ovaries.
How long does the cycle normally last?
About 28 days including the bleeding period which is called menstruation.
Although the first day of menstrual bleeding suggests the end of a cycle, what does it actually mark?
The beginning of development of the next ovarian follicle. It is also an easily observed and clearly marked feature in the cycle hence day one of menstruation is traditionally numbered day one of a menstrual cycle.
How long does menstrual bleeding typically last for?
5 days.
On day one of the menstrual cycle what do low levels of oestrogen and progesterone trigger?
The menstrual bleeding (loss of the endometrial lining of the uterus) and stimulation of FSH from pituitary gland.
What does FSH stimulate?
Some of the follicles in the ovary to mature.
What do the maturing Graafian follicles being to secrete?
Oestrogen.
What does the secretion of oestrogen stimulate?
The build up of the endometrial lining of the uterus into a rick vascular spongy layer, ready for a pregnancy.
Also stimulates the pituitary to release LH.
What are FSH and LH known as?
The gonadotrophic hormones.
What does the combined action of oestrogen, LH and FSH cause?
One of the mature Graffian follicles to rupture and release a ripe ovum at about day 14 - this is ovulation when the woman is fertile and the egg can be fertilised by a sperm.
Under the influence of LH, what does the empty Graafian follicle develop into?
A corpus luteum
What does the corpus luteum produce?
Progesterone
What do high levels of progesterone maintain?
The thickened endometrium so it is prepared to recieve a fertilised ovum.
If fertilisation does not take place what happens?
The corpus luteum breaks down and progesterone production stops - without progesterone the endometrium breaks down and the richly vascular lining is shed in the process of menstruation, and the cycle begins again.
What is menarche?
The very first period a girl has.
What is he average age of menarche in the UK?
Around 13 years but it may be as early as 8 or as late as 18 within the normal range.
It may take some time for the menstrual cycle to settle into a regular pattern in any individual and often the first few cycles do not produce mature ova. What should normal menstrual cycles vary between?
21 and 35 days.
What is the menopause (climacteric)?
This takes place when the finite number of follicles in the ovaries are used up - oestrogen and progesterone levels fall and menstrual periods become erratic and eventually stop completely. It is a completely normal stage of life which can cause problems for some women. The body may react in a number of ways to reduced levels of oestrogen and progesterone.
What age does the menopause take place?
The early stages of the menopause usually begin in the mid-late 40s and the final menstrual period usually takes place between the ages of 45 and 55.
How long can symptoms associated with menopause?
May last as long as seven years.
In some women, what is menopause characterised by?
In some women, the menopause is characterised by a number of vasomotor symptoms including palpitations, night sweats and hot flushes. They may suffer with sleep disturbance and repeated UTIs. It is also linked in some women with mood changes, depression and loss of libido although others find the exact opposite.
What is the loss of oestrogen in menopausal women believed to be associated with?
In the long term with a reduction in bone density (osteoporosis) and increased risk of heart problems.