Hormonal control of reproduction Flashcards
What does ICSH stand for?
Interstitial cell stimulating hormone
What are hormones?
Chemical messengers produced by the endocrine glands
Where are hormones directly released?
Into the bloodstream and travel to their target tissue or organ where they have their effect
What do hormones control?
The onset of puberty, sperm production and the menstrual cycle
At puberty what does the hypothalamus in the brain secret?
A releaser hormone that targets the pituitary gland
What is the pituitary gland stimulated to release?
One hormone called the follicle stimulating hormone (FSH) and a second hormone called luteinising hormone (LH) in women and interstitial cell stimulating hormone (ICSH) in men. By a releaser hormone produced in the hypothalamus. This triggers the onset of puberty.
In males what does FSH promote?
Sperm production in the seminiferous tubules of the testes
In males what does ICSH stimulate?
The interstitial cells in the testes to produce the male sex hormone called testosterone
What does testosterone stimulate?
Sperm production in the seminiferous tubules and also activates the prostate gland and the seminal vesicles to produce their fluid secretions
What happens if there is an overproduction of testosterone
Negative feedback mechanism controls FSH and LCSH
What does high levels of testosterone inhibit?
The secretion of FSH and LCSH from the pituitary gland, resulting in a decrease in the production of testosterone by the interstitial cells
What do seminiferous tubules unite to form?
Coiled tubes that connect to the sperm duct-free swimming sperm leave the testes in the sperm duct
what does semen contain?
Sperm and the fluid from the seminal vesicles and the prostate gland
what does seminal vesicles secrete?
A liquid rich in fructose to provide energy for sperm motility
What does the seminal vesicles liquid contain?
Hormone like compounds that stimulate contraction of the female reproductive tract
What does contractions of the seminal vesicles do?
Help the sperm reach the oviduct (where fertilisation takes place) quicker than ‘swimming’ alone
What does the prostate gland secrete?
Lubricating liquid containing enzymes of a thin consistency for the sperm to swim through the oviduct
what do the enzymes of the prostate gland do?
Maintain the fluid at optimum viscosity for sperm motility
Just before ovulation what do the cells lining the female cervox secret?
Watery mucus
What can the watery mucus do?
Be easily penetrated by sperm
What does GRH stimulate ?
The pituitary gland
What is produced at puberty
Gonad Releasing hormones (GRH)
What hormone is produced from the pituitary gland?
FSH/LH (ICSH)
After interstitial cells produces testosterone what does is help to do?
Helps FSH to produce sperm
What happens if there isn’t a constant concentration of testosterone?
The pituitary monitors this to then make ICSH increase or decrease testosterone production
When is the hypothalamus stimulated?
When it produces GRH
When are males fertile?
All the time
Where are interstitial cells found ?
Surrounding the sperm producing tubules of the testes
How are sperm formed?
from germline cells in tiny tubes called seminiferous tubules
How many days does the menstrual cycle take?
Approximately 28 days with the first day of menstruation regarded as day one of the cycle
What pituitary hormones are associated with the menstrual cycle?
FSH and LH and the ovarian hormones oestrogen and progesterone
What happens in the follicular phase (first half of the cycle)
FSH stimulates the development and maturation of a follicle surrounding the ovum and the production of the sex hormone oestrogen by the follicle
What does oestrogen stimulate?
The repair and vascularisation of the endometrium, thickening it and preparing it for the implant
What does high levels of oestrogen stimulate?
The secretion of LH by the pituitary gland
What happens in the luteal phase (second stage of the cycle)
A surge in LH triggers ovulation and then stimulates the development of the the corpus luteum from the follicle which secretes progesterone
What does LH also stimulate?
The corpus luteum to secrete the sex hormone progesterone
What does progesterone promote?
Further development and vascularisation of the endometrium, preparing it for the implantation of a blastocyst, if fertilisation occurs
What does high levels of oestrogen and progesterone inhibit?
The secretion of FSH and LH by the pituitary gland, which prevents further follicles from developing
What does oestrogen do to the cervical mucus?
It thins the cervical mucus making it more easily penetrated by sperm
What does a peak level of oestrogen stimulate?
A surge in the secretion of LH
What does the surge in LH trigger?
It triggers ovulation
What is ovulation?
The release of an egg (ovum) from a follicle in the ovary
When does ovulation occur?
Around mid-point of the menstrual cycle
What happens when there’s a lack of LH?
A degeneration of the corpus luteum with a subsequent drop in progesterone levels leading to menstruation
Give an account of gamete production in the testes
Sperm are produced in the seminiferous tubules
Gametes are formed from germline cells
Germline cells are formed in the seminiferous tubules of the testes
Germline cells divide by mitosis then meiosis to produce sperm
Testosterone stimulates sperm production in the seminiferous tubules
Give the location of fertilisation in the female reproductive system
Oviduct
Where is FSH produced in the body?
The pituitary gland
How is the concentration of testosterone in the blood prevented from becoming too high?
As testosterone production increase negative feedback to the pituitary inhibits ICSH production
Testosterone concentration decrease and ICSH production increases when testosterone drops
What indicates ovulation is likely to occur
Cervical mucus becomes watery and body temperature rises
What is an ovum surrounded by as it develops in the ovary
A follicle
When there’s a peak of oestrogen what starts to increase
progesterone
Describe the role of the secretion from the seminal vesicles
Produce fructose for energy
Enzymes to thin mucus
chemicals to produce contractions of oviduct
state an effect of oestrogen on the pituitary gland
stimulates LH production
Explain why the rise of ovarian hormones in the blood has a contraceptive effect
Ovarian hormones will inhibit FSH production and so no follicles containing ovules will develop
what day does ovulation occur?
Just after a peak of LH which stimulates ovulation
State one function of progesterone during early pregnancy?
Vascularisation of the endometrium
Describe two ways that the pituitary gland stimulates sperm production in the seminiferous tubules
FSH stimulates sperm production
ICSH stimulates testosterone production. Testosterone then stimulates sperm production
What effect does oestrogen have on the uterus between days 4 and 12
proliferation of endometrium
What effect does oestrogen have on the pituitary gland on day 12
stimulates LH production
How does FSH affect the structure of the follicle
Stimulates follicle development
How does lH affect the structure of the corpus luteum
Stimulates progesterone production
