Reproduction: Gametes And Hormones Flashcards
What are the two main functions of the testes?
- sperm production
- hormone production
Where does sperm production occur in the testes? What is it controlled by?
- occurs in seminiferous tubules
- controlled by Sertoli (nurse) cells
- spermatogenesis also occurs
Where does hormone production occur in the testes? What hormones are produced? What produces these hormones?
- hormones produced by Leunig cells in between tubules
- produces testosterone (steroid or androgen)
What molecule is the precursor to testosterone?
Cholesterol.
What is spermatogenesis?
- Mitosis produces spermatogonium
- then converted into primary spermatocyte via meiosis
- meiosis then produces secondary spermatocyte
- then spermatid
- then sperm is moved along lumen via muscle cells.
What is the function of the acrosomal vesicle in sperm?
- contains enzymes that will degrade part of egg so sperm can fuse with egg (ensures close contact with DNA)
Do sperm have mitochondrion?
Yes
What does the axial filament of the sperm contain? Where is it located?
Contains 9+2 array of microtubules seen in cilia and flagella
What enables movement of sperm?
Beating flagella
What is testosterone produced by and where? What does testosterone act via?
- made by Leydig cells in between tubules
- acts via androgen receptor in cells
What can testosterone be converted into and why?
Can be converted into olestra diol by Sertoli cells to aid spermatogenesis
Describe the relationship between testosterone and accessory sex organs.
Testosterone stimulates accessory sex organs (prostate and seminal vesicles)
What does testosterone modulate? Describe an animal example.
Modulates secondary sex characteristics and male type behaviour e.g courtship and aggression.
E.g peacock has high level of testosterone during courtship behaviour (shows feathers).
Explain the process of controlling testis function (hypothalamo-pituitary-gonadal HPG axis).
- Gonadotropin releasing hormone (GnRH) from hypothalamus stimulates release of LH and FSH (the Gonadotropins) from the pituitary gland
- LH enters testis where it stimulates Leydig cells to produce testosterone
- Testosterone either binds to Sertoli cells or enters reproductive tract/accessory sex organs
- FSH enters testis where it stimulates Sertoli cells to undergo spermatogenesis and produces Inhibin
- testosterone from Leydig cells inhibits GNRH and LH production
- inhibin from Sertoli cells inhibits FSH production
How many eggs are females born with? Does this change?
Born with 2 million eggs. Decreases as time passes.
What is the surface of an ovary made of?
Tough epithelium
What occurs in the cortex of the ovary? What does the cortex contain?
Growth occurs in the cortex. It contains:
- germ cells
- follicles
- corpora lutea
- corpora albicans
What is the fastest growing tissue in the body of females?
Corpora lutea on ovary
What is the function of the medulla in the ovary? What does it contain?
Function is to supply blood in the ovary. Contains fibrous connective tissue, blood vessels, and nerves
Does the number of follicles in the ovary cortex change?
Fixed number set at birth
What is folliculogenesis?
Development of the follicle and the egg (oocyte)
What is the oocyte?
The egg cell that develops into ovum and then an embryo.
What is the function of Theca cells in the ovary? What would they be equivalent to in males?
Make androgens from cholesterol . Equivalent to Leydig cells
What is the function of Granulosa cells in the ovary?what would they be equivalent to in males?
Makes oestradiol from androgen. Equivalent to Sertoli cells
What is the uterus? What is it lined with?
- uterus is the site of embryo implantation
- lined with endometrium that is secretory tissue lining regulated by progesterone and oestrogen
Why do some species have multiple corpus luteum?
If they produce more than one fertilised egg at a time.
E.g mouse produce litters
When is progesterone produced?
Produced by corpus luteum after ovulation.
What are three main functions of oestradiol?
- regulates oviduct, uterus, cervix, vagina and other sex organs
- prepares the endometrium for implantation (spiral artery formation)
- promotes oestrus behaviour (mating)
What produces oestradiol? What does oestradiol act via?
- produced by granulosa cells of follicle
- acts via oestrogen receptors
Describe three functions of progesterone
- regulates sex organs
- prepares endometrium for implantation- spinal artery growth
- modulates effects of oestradiol - acts as ‘brake’ to stop follicle growth
What produces progesterone? What does progesterone act via?
- produced by corpus luteum
- acts via progesterone receptors
Explain the steps of folliculogenesis using the HPG axis.
- GnRH produced by hypothalamus stimulates anterior pituitary gland to produce LH and FSH
- FSH stimulates folliculogenesis (follicle growth), oocyte growth (oogenesis) and oestradiol production.
- oestradiol from growing follicle in ovary positively affects reproductive tract
- oestradiol negatively regulateS GnRH
- inhibin from granulosa cells negatively inhibits FSH
Explain the steps of ovulation with mature follicles.
More oestradiol is produced as follicles get bigger and mature. Once a threshold of high oestradiol production is reached, this triggers positive feedback.
Oestradiol triggers hypothalamus to produce more LH and it is this surge of LH that causes ovulation.
Explain the steps of the luteal phase, after ovulation.
- ovulated follicle transforms into corpus luteum
- oestradiol production decreases and progesterone production increases
- progesterone negatively regulates FSH preventing follicle growth, allows low LH concentrations
- after about 2 weeks, corpus luteum regresses due to lack of signal from embryo. This allows increase FSH and follicle growth.
What phase in the menstrual cycle is progesterone dominant and what phase is oestrogen dominant?
Progesterone - luteal phase
Oestrogen - follicular phase
What separates the luteal phase form the follicular phase?
Ovulation
What happens to corpus luteum if pregnant?
No luteal regression as signal from embryo maintains CL
How does the combined oral contraceptive pill work? What does it contain?
Contains progestin plus oestrogen that suppresses GnRH and therefore leads to decrease in FSH and LH
Prevents follicle growth and ovulation
Increases cervical mucus thickness to help stop sperm
Thins endometrium to prevent implantation
What does vasectomy result in?
Cuts vas deferens preventing release of sperm
What does tubal ligation do?
Cuts Fallopian tube preventing egg from entering uterus
