Week 7: The reproducive system Flashcards
1
Q
What is the reproductive system made of?
A
- The gonads
- The external and internal genitalia/reproductive tracts
- Ducts that transport and/or house gametes (germ cells)
Mullerian duct (female) and Wollfian duct (male) derivatives
- Ducts that transport and/or house gametes (germ cells)
- Accessory sex glands
- Supportive secretions for gametes - secreted into reproductive tract
2
Q
What makes up the accessory reproductive organs?
A
- Organs of the reproductive tract: transport of gametes
- Glands: secrete fluids into reproductive tract
3
Q
What are the functions of the gonads?
A
- Produce haploid gametes (germ cells)= gametogenesis
- Spermatogenesis in the testis and oogenesis in the ovaries - Produce and secrete gonadal hormones; either peptide or steroid hormones (steroidogenesis)
4
Q
What are the 3 major hormone types secreted by the reproductive system?
A
- Steroid hormones (testosterone, progesterone and oestrogens)
- These are produced from cholesterol
- Gonadotropins - peptide/protein hormones
- FSH (pituitary gland)
- LH (pituitary gland)
- hCG (chorionic gonadotropin) - produced by placenta
- Oxytocin - a peptide/protein hormone
- Produced in the hypothalamus, excreted by the pituitary gland
5
Q
Where does progestogen orginate from?
A
Cholesterol (C27)
6
Q
Where does androgen originate from?
A
Progestogen
7
Q
How many carbons does progestogen and androgens have?
A
Progestogen - C21 , androgen - C19
8
Q
Where does oestrogen originate from?
A
Androgen
9
Q
How many carbons does oestrogen have?
A
C18
10
Q
Name a type of oestrogen and progestogen
A
Oestradiol and progesterone
11
Q
How does sex determination occur after the genetic sex is determined by XX or XY?
A
during fertilisation the SRY gene (sex-determining region of Y-chromosome) codes for the production of TDF (testis-determining factor)
12
Q
Without the TDF and SRY region what is the default?
A
To differentiate into ovaries
13
Q
Apart from testosterone what else do the testes secrete?
A
Mullerian-inhibiting factor
14
Q
What is the effect of the absence of testosterone?
A
Degeneration of Wolffian ducts + development of undifferentiated external genitalia to female reproductive lines
15
Q
What are the effects of testosterone?
A
Secondary sexual characteristics
Libido at puberty
Growth & maturation of genitalia
Protein anabolic effect
Spermatogenesis
Bone growth at puberty
16
Q
When is testosterone secreted?
A
- Secreted before birth (masculinize developing reproductive system)
- Ceases until puberty, continues throughout life
17
Q
Describe the progression of a ovary
A
primordial → primary → secondary → pre-antral → antral →ovulatory / Graafian follicle)
18
Q
What gonadal hormones are synthesized by the follicles?
A
androstenedione & oestradiol
19
Q
What gonadal hormones are synthesized by the corpus luteum?
A
progesterone & oestradiol
20
Q
What are the target cells of oestrogen and FSH?
A
Granulosa cells- they secrete chemical messengers in response
21
Q
What other hormones do Granulosa cells secrete in response to oestrogen and FSH?
A
- secrete inhibin - provides negative feedback to FSH secretion,
- transport nutrients to oocytes through gap junctions
- Secrete oestrogens
22
Q
What is the effect of oestradiol?
A
- ova maturation & release (ovulation)
- development of female sex characteristics
- transport of sperm within the female
23
Q
What is the function of progesterone?
A
- prepares suitable environment to nourish
- developing embryo/foetus
- breasts ability to produce milk
- breast differentiation (development of lobuloalveolar tissue- ability to produce milk)
24
Q
What hormones trigger the menstrual cycle?
A
decreased oestrogens and progesterone.
25
What hormone triggers ovulation?
Surge in LH, the surge is caused by high levels of estradiol secreted by the mature follicle
26
What does the corpus luteum produce?
Progesterone and oestrogen
27
Where are LH and FSH secreted from?
The anterior pituitary gland
28
Oestradiol and progesterone are secreted by what?
Oestradiol - follicles and CL
Progesterone is only secreted by the CL
29
Where does spermatogenesis occur?
In the seminiferous tubules
30
What is the function of a Sertoli cell?
To support spermatogenesis and secrete inhibin (which inhibits FSH)
31
Where are Leydig cells located and what is their function?
- Leydig cells are located between the seminiferous tubules (interstitial cells)
Function: To synthesise/secrete testosterone.
→ Secretion of testosterone is stimulated by LH
The release of hormones is regulated by a negative feedback loop
32
Where is GnRH (gonadotropin releasing hormone) secreted from and what does it do?
-Hypothalamus
-Activates the release of FSH and LH from the anterior pituitary (activating mechanism)
33
What is the effect of FSH in males?
acts on Sertoli cells and stimulates the production of gametes in the seminiferous tubules
34
What is the effect of LH in males?
acts on the interstitial space (between the seminiferous tubules) activates release of testosterone which further activates the production of sperm
35
Explain how the male hormones can act as a negative feedback loop
- High levels of testosterone inhibit the activation of the anterior pituitary and the hypothalamus
- So decrease in LH and FSH and GnRH
- Less testosterone
36
What are spermatogonia?
Undifferentiated haploid spermatids
37
What is the difference between spermatogenesis and spermiogenesis
Spermatogenesis = the whole process (stimulated by testosterone)
spermiogenesis = subset of spermatogenesis (stimulates by FSH)
38
How does a spermatogonium develop to a matuer spermatozoa?
Spermatogonium -> primary spermatocyte -> secondary spermatocyte -> spermatid -> mature spermatozoa
39
What hormone is more important in the early stages of meiosis and which one is more important in the later stages?
FSH- early stages
Androgens - later
40
Where do sperm complete their spermiogenesis
In the caput epididymis
41
Where are the sperm stored?
In the cauda epididymis
42
What fuels the spermatozoa for movement?
Epididymal secretions (e.g. glyceryl phosphorylcholine and inositol)
43
What makes up the accessory sexual organs/glands in the male reproductive system?
Seminal vesicles and prostate gland
44
What is the function of the seminal vesicles?
fructose production (anaerobic fructolysis)
45
What is the function of the prostate gland?
- release citrate (anticoagulant- chelates Ca2+ and prevents coagulation of the seminal fluid)
- Releases acid phosphatase (which cleaves choline from glyceryl phosphorylcholine)
46
What hormones does the placenta secrete?
1. Human chorionic gonadotropin (hCG)
2. Oestrogens (estrone, oestradiol and estriol)
3. Progesterone
47
What are the functions of hCG?
- maintains the CL during pregnancy (because it produces other hormones)
- Stimulates testosterone synthesis in the developing testes of the male (XY) embryo
48
What is the function of oestrogens on the placenta?
- Stimulate the endometrial growth
- Stimulates proliferation of mammary tissue (for lactation)
49
What is the effect of progesterone on the placenta?
- Promotes the formation of cervical mucus plug - which protects the embryo
- Supress the uterine contractions - to prevent early childbirth
- Stimulates the differentiation of lobuloalveolar system of the mammary glands (for lactation)
- Prevents subsequent follicular development and ovulation
- Negative feedback on LH and FSH; it suppresses the ovulatory LH surge
50
What is the effect of human chorionic somatomammotropin?
- Similar to growth hormone and Prolactin
- It increases the availability of glucose and NEFA (foetus)
51
What is the function of relaxin?
- To soften the cervix and loosen the connective tissue
- Parturition - cervical dilation
- Pelvic bones
52
What is the function of placental PTHRP?
To increase the maternal calcium
53
What hormones are seen in the first trimester of pregnancy?
The placenta secretes high levels of hCG
- This activates LH -Chorionic gonadotropin receptors in the CL to stimulate progesterone and oestradiol synthesis/secretion
54
What hormones does the placenta secrete in the 2nd and 3rd trimester?
- Secretes progesterone and oestradiol
- Produces oestriol from the foetal adrenal androgen substrate
55
How is the actual lactation suppressed during pregnancy and how is it stimulated?
Oestrogen and progesterone suppress
Prolactin and oxytocin stimulate
56
What are the theories for the initiation of birth (parturition)?
1. high levels of oestrogen
2. High levels of oxytocin
3. CRH (corticotropin releasing hormone) - placenta
4. Inflammation
57
How are high levels of oestrogen supposed to initiate parturition?
- Oestrogen upregulates connexins - increased gap junctions
- Upregulate myometrial receptors for oxytocin
- Stimulate the local prostaglandin synthesis
58
How are high levels of oxytocin supposed to initiate parturition?
- Myometrial responsiveness exceeds critical thresholds
- Increased Ca2+ which activates myosin light chain kinase (MLCK) which triggers contraction of the uterine muscles
59
How are high levels of CRH supposed to initiate parturition?
- May increase oestrogen synthesis (from foetal androgens)
- Increased cortisol (increases local prostaglandin synthesis and promotes lung maturation)
60
How is inflammation supposed to initiate parturition?
Increased nuclear factor k-B upregulates the inflammatory cytokines and increases local prostaglandin synthesis
61
What is the Fergusson reflex?
The positive spiral feedback for uterine contractions
62
Describe the steps that lead to uterine contractions
1. High levels of oestrogen increase uterine responsiveness to OT (1st high oestrogen promotes synthesis of connexins within uterine smooth-muscle cells.)
2. These are inserted into myometrial plasma membranes to form gap junctions so smooth muscle cells contract as co-ordinated unit.
3. 2nd high of oestrogen increases concentration of myometrial receptors for OT)
4. Foetal pressure stimulates receptors in cervix > neural signal to spinal cord to hypothalamus > triggers OT release from PP
- Positive-feedback cycle continues throughout labour until delivery when pressure on cervix (stimulus for oxytocin release) is removed
63
What is another myometrial stimulant apart from OT?
PGF2α is a powerful myometrial stimulant > further enhances uterine contractions
64
When do oestrogen and progesterone levels fall?
During labour
65
What are the two main groups of reproductive hormones?
steroid hormones and gonadotropins
66
Which chain is common between LH and FSH?
The alpha chain
67
What is testosterone converted to in target tissue cells in males?
Oestradiol
68
What is the effect of oestradiol in males?
Ligand for oestrogen receptors (ER) in testes, prostate, bone & brain
Affects spermatogenesis, bone homeostasis / epiphyseal fusion
69
What are the non-reproductive actions of oestradiol and progesterone in females?
Increased adipogenesis
Increased bone mineral denisty
70
What phase are unmature oocytes stuck in?
In prophase 1
71
What is the effect of anabolic steroids on males?
More testosterone inside the blood (not the testes)-> negative feedback loop, suppresses the anterior pituitary gland -> less FSH and LH + GnRH -> decreased activity of Sertoli cells and suppressed spermatogenesis
72
Where is oxytocin produced and released from?
produced - hypothalamus
released - pituitary gland
73
What are the secondary effects of oxytocin in females?
Neuromodulator in communication between neurons (e.g. recognition and trsut)
