The Reproductive System 2 Flashcards
What is the Endocrine system?
A collection of glands located throughout the body that manufacture and
secrete hormones to regulate physiological function
* generally act in a paracrine or endocrine manner
What are hormones?
A chemical substance produced by ductless glands within the endocrine system
What are the major endocrine glands?
- Adrenal glands
- Hypothalamus
- Ovaries and testes
- Pancreas
- Thyroid and parathyroid
- Pineal gland
- Pituitary gland
- Thymus gland
What are the 3 general classes of hormones + details?
- Hormones derived from amino acids
- Dopamine, epinephrine (tyrosine precursor)
- Proteins and peptides
- Insulin (peptide), growth hormone (protein)
- Hormones derived from lipids
- Prostaglandins (derived from phospholipids)
- Steroids (derived from cholesterol)
- Most RH steroids but stimulated by other classes
Details overview of cholesterol + source?
- Large molecule
- 4 cycloalkane rings
- Large hydrocarbon chain
- Essential component of all cellular
membranes - Source?
- Diet and de-novo
cholesterol: what sex hormones/ steroids is it in + precursor for?
- Oestrogens
- Progestogens
- Androgens
- Steroid hormones
- Adrenal steroids
- Glucocorticoids
- Mineralcorticoids
What are the 3 classes of reproductive hormones?
- Commonly called sex steroids or steroid hormones
- Produced mainly by the gonads (ovaries and testes)
- Some production by placenta, adrenal glands
- Three classes:
- Oestrogens
- Androgens
- Progestogens
- Interact with oestrogen (ER), androgen (AR) or progesterone (PR)
receptors respectively
Oestrogens types/classes?
- Oestradiol
- Oestrone
- Oestriol
What are the types of androgens?
- Testosterone
- 5⍶-dihydrotestosterone
(DHT) - androstenedione
- dehydroepiandrosterone
(DHEA)
what are the types of progestogens?
progesterone
Give an overview of the major functions of reproductive hormones?
- Bind to specific receptors in target tissues
- AR, ER, PR
- Exert a range of effects on both organs and the body as a whole
- Primary role: maturation of reproductive organs, fertility and pregnancy
- Secondary role: development of physical characteristics
Where is testosterone produced?
leydig cells
where are oestrogens produced?
ovarian granulosa cells
Where are androgens produced?
ovarian theca cells
Where are progesterones produced?
corpus luteum + placenta - placental syncytiotrophoblasts
* Eventually takes over from corpus luteum
Describe reproductief hormones and molecular action?
- Generic mechanism of action
- Hormones enter cells
- Hormones bind to intracellular receptor
- Conformation change and translocation
- DNA binding (HRE’s)
- Gene expression (or repression)
what regulates gonadal steroidogenesis?
- Endocrine function of gonads is regulated by HPG axis
- Hypothalamus
- Pituitary
- Gonad
What is the hypothalamus + what is does?
- Small structure at base of forebrain
- Hypothalamus releases GnRH
(Gonadotrophin Releasing Hormone) - Peptide hormone
- Released into blood
- Reach pituitary
What is the pituitary gland + what it do?
- Pea-sized gland located at the base of the
skull ventral to the hypothalamus - Comprised of two elements
- Posterior and anterior lobes
- Anterior pituitary contains specialised cells
(gonadotropes) - GnRH stimulates gonadotropes to
- Produce gonadotrophins
- glycoproteins
- FSH (follicular stimulating hormone)
- LH (Lutenising hormone)
- hCG (human chorionic gonadotrophin)
What are gonadotrophin?
LH + FSH
What do LH + FSH do?
- LH main functions
- ♀acts on ovarian follicle inducing
ovulation - ♂acts on testes producing testosterone
- FSH main functions
- ♀promotes ovarian follicle development
& oestrogen production - ♂stimulates spermatogenesis in testes
Negative feedback on hormones?
decreases level of signal and maintains homeostasis
Direct feedback on hormones?
- Steroid hormones (testosterone/oestrogen) decrease
secretion of gonadotrophins (FSH, LH)
Positive feedback on hormones?
- Steroid hormones inhibit their own production indirectly by
inhibiting hypothalamus GnRH - → decreased pituitary gonadotrophin secretion
- → reduced steroid hormone production
Negative regulation of steroidogenesis by inhibin
- Inhibin
- Protein hormone
- In females, released by granulosa cells in response to FSH
- In males, produced by Sertoli cells in response to androgens
- Negative regulator of FSH
Positive feedback of reproductive hormones
- Positive feedback
- leads to an increase in hormone level
- Occurs within follicular phase of uterine (menstrual) cycle
- Oestrogen-induced LH to trigger ovulation
