human reproduction Flashcards
Discuss the function of the hormone progesterone in maintaining pregnancy.
Progesterone levels increase; keeping the endometrium thickened;
which prevents menstruation / ovulation from taking place.
Name any three functions of the placenta during pregnancy
Nutrition of the embryo excretion; gaseous exchange acts as a micro-filter (barrier) prevents entry of pathogenic micro-organisms has an endocrine function
Describe the importance of meiosis
Halving the number of chromosomes to balance the doubling effect of fertilization.
Ensures variability in the offspring / other gene combinations.
Formation of gametes
Why does the cell divide twice during meiosis?
First meiotic division — parent cell split into two cells (2n) / reduction division.
and
second meiotic division — two cells divide to form four sex cells / gametes (n)
Corpus cavernosa
two columns of erectile tissue
Corpus spongiosum
erectile tissue that ensures the urethra stays open during erection for the passage of semen
The testes
Produce sperm
Develop in abdominal cavity and descend into the scrotum just before birth
Optimum temperature for sperm development 350C – below body temperature
Sperm produced in seminiferous tubules
Process involves several cell divisions
Epididymis – stores and matures sperm cells
where is testosterone produced
Leydig (interstitial) cells in testes produce male hormone testosterone
where is the hormone oestrogen produced in females
produced by mature Graafian follicles – causes appearance of secondary sexual characteristics in young women
where is the hormone progesterone produced in females
produced by the corpus luteum – establishes the menstrual cycle with the aid of oestrogen – maintains pregnancy – prepares breasts for milk production
what is the site of fertilization
Fallopian tubes
explain the ovarian cycle and ovulation
- primodial follicle
- mature graafican follicle
- FSH stumlates the follicle to secrte oestrogen and form antrum ( cavity)
- secondary oocyte
- LH cause the ripe follicle burst and an oocyte is released
what happens to the graafian follicle after ovulation
forms the corpus luteum which secretes progesterone
what happens to the corpus luteum if fertilization takes place
its matures
what is the purpose of the menstrual cycle
prepares body for pregnancy
explain the negative feedback system between oestrogen and FSH
- FSH stimulates the development of the follicle which thus secretes oestrogen
- oestrogen stimulates pituitary gland to secrete LH as well as repairs the endometrium after menstruation has taken place
- LH inhibits the secretion of FSH
- therefore only one follicle is produced
explain the negative feedback system between progesterone and LH
- LH stimulates the ovary to secrete progesterone from the corpus luteum
- progesterone prepares the endometrium for implantation and inhibits the secretion of LH and FSH
what are the 4 phases of the menstrual cycle
- menstrual phase
- follicular phase
- ovulation phase
- luteal phase
what structure allows the blasotocyst to embed itself into the endometrium
the chorion villi
what is the function of glycoprotiens
allows blastocyst to attach to endometrium
what is the outer layer of the blastocyst called
trophoblast
what do the arteries in the umblical cord do
carry deoxygenated blood and waste from foetus to placenta
what does the vien in the umblical cord do
carries oxygenated blood which is also rich in nutrients to the foetus from placenta
functions of the placenta
- Water, by osmosis
- Nutrients – glucose, amino acids, fatty acids, ions, vitamins – active transport – good nutrition for mother important during pregnancy
- Nitrogenous waste such as urea – diffuse
- Antibodies produced by mother – move to foetus and provide short-term passive immunity
what is the placenta
Transfer of substances by diffusion via the thin membranes separating maternal and foetal blood
what hormone is secreted during pregancy
Human chorionic gonadotrophin
what is another word for birth
parturition
what hormones are secreted during birth
Placenta secretes hormone, relaxin, which causes pelvic ligaments to relax, widen and become more flexible in preparation of birth
Hormone oxytocin from pituitary stimulates uterine contractions which dilate the cervix and expel the baby
