sexual reproduction Flashcards
Spermatogenesis
The process of sperm production within the seminiferous tubules in the testes.
where does spermatogenesis take place?
takes place in the seminiferous tubules
how many seminiferous tubules are formed in each testis?
around 1000, where spermatozoa are formed
where does the mobility of spermatozoa improve?
the epididymis where they are collected
what do the seminal vesicles secrete?
mucus
what fluids mix during ejaculation?
mucus and prostate fluid
what is the purpose of the mucus and prostate fluids?
helps to maintain sperm mobility, provide nutrients e.g. fructose and are alkaline which neutralises acidity found in urine and the vagina
what are the cells (in order of division and maturation) that are involved in spermatogensis?
germinal epithelial, spermatogonium, primary then secondary spermatocytes, spermatids and spermatozoon.
how are spermatogonium produced?
diploid germinal epithelial cells divide by mitosis to produce diploid spermatogonium
how do spermatocytes divide to form spermatids?
- primary spermatocytes divide by meiosis I to produce secondary spermatocytes.
- secondary spermatocytes undergo meiosis II forming spermatids
how is spermatozoa formed?
when the spermatids differentiate, they mature into spermatozoa
what is the purpose of Sertoli cells?
provide spermatozoa with nutrients and protect them from male’s immune system
what do interstitial cells (cells of Leydig) secrete?
testosterone which is involved in stimulating the process of spermatogenesis
what is an oocyte?
a developing egg
what is the purpose of cilia in the oviduct?
wafts the secondary oocyte along the- oviduct
how is polyspermy (entry of additional sperm) prevented to the secondary oocyte?
changes to the zona pellucida is made following the entry of a single spermatazoon
what is capacitation?
glycoproteins are removed by enzymes from the surface of the sperm, making the plasma membrane more permeable to swim more rapidly
what is the acrosome reaction?
hydrolytic enzymes in the
what happens to the egg cell following fertilisation?
completion of the second meiotic division and formation of the ovum/ the cortical reaction.
what is the cortical reaction?
occurs when the cortical granule membranes fuse with the oocyte cell membrane. The zona pellucida is converted into a fertilisation membrane
what is the acrosome reaction?
when the acrosome releases enzymes which digest cells forming the corona radiate surrounding the oocyte allowing the sperm head to contact the zona pellucida. Now acrosin hydrolyses the zona pellucida, allowing the head to enter the oocyte.
how is the diploid zygote formed?
when the sperm pronucleus fuses with the ovum pronucleus
what happens to the Graafian follicle following fertilisation?
Becomes the corpus luteum and produces progesterone.
- if no fertilisation occurs, it regresses
what happens if an embryo fails to emplant?
the endometrium layer that is filled with blood sheds each month during the menstrual cycle
what is the function of the acrosome?
it contains proteases to digest the cells of the corona radiata and zona pellucida
explanation of sexual intercourse
the erect penis is inserted into the vagina and semen is ejaculated by contractions of the smooth muscle in the walls of the epidiymis, vas deferns and penis.
where is FSH produced?
anterior pituitary gland
what is the effect of FSH?
stimulates the maturation of follicles and oocytes in the ovaries and to stimulate the follicles to produce oestrogen
where is LH produced?
anterior pituitary gland
what is the effect of LH?
stimulates the release of the secondary oocyte from the ovaries (for ovulation) and stimulates the empty follicle to produce progesterone
where is oestrogen produced?
the ovaries
what is the effect of oestrogen?
stimulates the repair of the endometrium and the release of LH but inhibits the release of FSH
where is progesterone produced?
the ovaries
what is the effect of progesterone?
stimulates further development of the endometrium and inhibits the release of LH and FSH
why does the developing embryo secrete HCG just before and following implantation?
the release of HCG maintains the corpus luteum for the first 16 weeks of pregnancy
what hormone does the placenta secrete?
progesterone and oestrogen which then increases to high levels in the blood plasma
what hormones are inhibited during pregnancy?
FSH and LH
what effect does progesterone have on the uterine wall?
supresses the uterine wall’s ability to contract
why is oestrogen important for the growth of the uterus?
it stimulates the growth of the uterus to accommodate the growing foetus and stimulates the growth and development of the mammary glands during pregnancy
what is negative feedback?
when a disturbance to a system brings about a response that restores the system to its original state
what is positive feedback?
when a disturbance to a system brings about a response that increases the disturbance even further
where is the hormone HCG made?
the embryo
where is excess HCG excreted?
in the urine, where its presence is used to test for pregnancy
what happens to secretion of hormones just prior to birth?
progesterone levels decrease (for contractions to begin), whilst oestrogen levels increase
what happens in the cervix just prior to birth?
contractions stimulate stretch receptors in the service, oxytocin to be released from pituitary glands which stimulates contraction
what is the effect of prolactin?
stimulates milk production in the mammary glands
What does suckling stimulate?
the nerves in the nippe and aerola that travels to the hypothalamus
what hormones does the hypothalamus stimulate?
posterior pituitary oxytocin to release milk and anterior pituitary to release prolactin for additional milk production
