The reproductive system Flashcards
What does seminal fluid consist of?
- Fructose
- Citric acid
- Bicarbonate (used to neutralise the acidic environment of the vagina)
- Fibrinogen
- Fibrinolytic enzymes
Describe the spermatic cord.
Formed at deep inguinal ring
Contains several structures including:
- Testicular artery
- Pampiniform plexus (v)
- Autonomic & GF nerves
- Lymph vessels
- Vas deferens
Describe the penis.
- 2 x Corpora Cavernosa
- 1 x Corpora Spongiosum
- Erection due Parasympathetic stim
- Ejaculation due Sympathetic stim
- Point and Shoot
(see diagram 4/68)
What is the arterial blood supply for the testes?
- testicular arterties from the aorta via the spermatic cord
Which lymph nodes do the tests drain to?
para-aortic lymph nodes
see diagram 5/68
Where are the ovaries?
Ovaries inside peritoneal cavity (remainder outside)
see diagram 6/68
What is the arterial blood supply for the ovaries and uterus/vagina?
ovaries: ovarian arteries (from aorta)
uterus/vagina: uterine arteries (from internal iliac a)
Which nervous system stimulates erection?
para-sympathetic nervous system
Which nervous system stimulates ejaculation?
sympathetic nervous system
Which are the lymphatic drainage systems for the ovaries and the uterus/vagina?
Ovaries: para-aortic LNs
Uterus/Vagina: iliac, sacral, aortic and inguinal LNs
What is the gametogenesis?
production of gametes from reproduction
What are the two functions of the gonads?
- gametogenesis
2. reproductive hormone production
When does gametogenesis begin?
at puberty
Describe the Germ cells in males across a lifespan.
- Gametogenesis begins at puberty
- Spermatogonia undergo differentiation and self-renewal -> pool available for subsequent spermatogenic cycles throughout life (continuous fertility)
- Produce ~1,500 mature sperm/second
(see diagram 9/68)
What happens to the germ cells before birth in females?
- Multiplication of Oogonia to ~ 6 million/ovary
- Form 10 Oocytes within ovarian follicles (= primordial follicle) -These begin meiosis (halted in prophase)
- Some primordial follicles degenerate (atresia).
- At birth ~2 million/ovary remain
What happens to the germ cells by puberty in females?
-By puberty <0.5 million/ovary remain (due further atresia)
What is the name for gametogenesis in males?
spermatogenesis
Define spermatogenesis.
production of mature spermatozoa
What is the Vas deferens surrounded by?
muscle (for ejaculation)
Is the vagina sterile or non-sterile?
non-sterile
What do the fallopian tubes have?
• Fallopian tubes have cilia and spiral muscle
Where does fertilisation occur?
• Fertilisation in ampulla (wider part of Fallopian tube)
What is the uterus supported by?
• Uterus supported by tone of pelvic floor (levator ani & coccygeus) and ligaments (broad, round, uterosacral)
When is the endometrium shed?
• Endometrium shed at menses due to vasoconstriction of arterioles
Where is the ureter in relation to the cervix?
• 1cm lateral to cervix is ureter
Which areas of the female reproductive system are sterile?
• All areas superior to cervix are sterile (shedding, thick
mucus, narrow os, pH<4.5)
How many mature sperm are produced per second?
1500
Describe spermatogenesis.
Spermatognium (44XY) -> [mitosis] primary spermatocytes (44XY) -> [1st meiotic divison] secondary spermatocytes (22X or 22Y) -> [2nd meiotic division] spermatids (22X or 22Y) -> [differentiation] spermatozoa (22X or 22Y)
(see diagram 13/68)
Describe the seminiferous tubules.
- Sertoli cell inside
- Leydig cell outside
(see diagrams 14-15/68)
What are the main reproductive hormones in males?
androgens:
- testosterone
- dihydrotestosterone
- Androstenedione
inhibin + activin
oestrogens (from androgen aromatisation)
Where are the sertoli cells?
within seminiferous tubules
Which receptors do the sertoli cells have?
FSH receptors
What are the functions of sertoli cells?
Support developing germ cells • Assist movement of germ cells to tubular lumen • Transfer nutrients from capillaries to developing germ cells • Phagocytosis of damaged germ cells
Hormone synthesis
• Inhibin & Activin (-ve or +ve on FSH)
• Anti-Mullerian Hormone (AMH)
• Androgen-Binding Protein (ABP)
Enrico Sertoli 1865
Where are the Leydig cells?
between seminiferous tubules
What receptors do the Leydig cells have?
LH receptors
Leydig cells have a pale cytoplasm as they are cholesterol-rich
What are the functions of Leydig cells?
Hormone synthesis • On LH stimulation, secrete androgens: - Testosterone (oestrogens) - Androstenedione - Dehydroepiandrosterone (DHEA) (can be aromatised to oestrogens)
What is the name for gametogenesis in females?
oogenesis
What is the definition of oogenesis?
production of mature oocytes
Describe oogenesis.
in 2nd trimester of pregnancy, all oogonia in foetus develop into primary oocytes (forming primordial follicles):
oognium (44XX) -> [mitosis] primary oocytes (44XX)
Menarche:
primary oocytes (44XX) -> [1st meiotic division] secondary oocytes (22X)
(shedding of polar body)
Sperm fusion occurs around the 2nd meiotic division.
secondary oocytes (22X) -> [2nd meiotic division] ootids (22X) -> [differentiation] ova (22X)
(see diagram 22/68)
What is menarche?
first menstrual cycle
What does sperm fusion cause?
the final stage of differentiation of the ova
What is folliculogenesis?
follicle development
Describe folliculogenesis.
- Primordial follicle (10 Oocyte at birth)
- Primary (=Preantral) follicle
- 10 Oocyte and layers of granulosa cells and outer theca cells - Secondary (=Antral) follicle
- Fluid-filled cavity (antrum) develops
- FSH and LH receptors - Mature (=Graafian/Preovulatory)
follicle
- Forms due to LH surge
- 20 Oocyte formed - Ruptures surface of ovary
6-7. Corpus Luteum
- Progesterone & oestrogen (stim by LH/HCG)
- In pregnancy, progesterone & oestrogen production taken over by placenta
(see diagram 24/68)
Describe the mature follicle.
Mature follicle = Graafian follicle = Preovulatory follicle
contains the ovum
(see diagram 25/68)
What are the main female reproductive hormones?
Oestrogens:
- Oestradiol
- Oestrone
- Oestriol
Progestogens:
- Progesterone
Androgens:
- Testosterone
- Androstenedione
- DHEA (but not DHEAS which is made in adrenals)
Relaxin
Inhibin
What are the Theca cells associated with?
outer part of ovarian follicles
What are the functions of the Theca cell?
Support folliculogenesis
• Structural & nutritional support of growing
follicle
Hormone synthesis
• LH stimulates synthesis of androgens
- Overactivity -> high androgen levels
What are the Granulosa cells associated with?
inner part of ovarian follicles
What are the functions of the Granulosa cell?
Hormone synthesis
• FSH stimulates granulosa cells to convert
androgens to oestrogens (by aromatase)
• Secrete Inhibin & Activin (effects on FSH)
After ovulation
• Turn into granulosa lutein cells that produce:
- Progesterone (-ve feedback, promote pregnancy by maintaining endometrium)
- Relaxin (helps endometrium prepare for pregnancy and softens pelvic ligaments/cervix)
What are the gonadal sex steroid hormones?
oestradiol
+
testosterone
both chemicals are very similar
in men, all of human steroidgenesis occurs in the Leydig cells, but in females it depends.
(see diagram 31-32/68)
Describe the Hypothalamic-Pituitary-‘Gland’ (HPG) Axis for reproduction.
Kisspeptin -> [Hypothalamus] GnRH -> [pituitary] LH/FSH -> [glands/targets] Gonads -> [Target hormones] Oestrogen, Progesterone, Androgen
Oestrogen and progesterone can feedback to act on the hypothalamus and the pituitary
(see diagram 34-35/68)
How many hormones are produced by the anterior pituitary gland?
6
How many hormones are produced by the posterior pituitary gland?
2
What effect can hyperprolactinaemia have on kisspeptin neurons?
Hyperprolactinaemia inhibits Kisspeptin Neurons
When are testosterone levels highest for men
in morning
Describe Hyperprolactinaemia.
Prolactin binds to prolactin receptors on kisspeptin neurons in hypothalamus -> Inhibits kisspeptin release.
- > Decreases in downstream GnRH/LH/FSH/T/Oest
- > Oligo (>35d menses) or amenorrhoea (3-6m no menses)/Low libido/Infertility/Osteoporosis
(see diagram 36/68)
What the menstrual cycle comprise of?
Ovarian Cycle & Uterine Cycle driven by hormonal level changes
What are the phases in the Ovarian Cycle
- Follicular Phase
- Ovulation (=pre-ovulatory phase)
- Luteal Phase
What is the typical duration of the menstrual cycle?
28 days
What are the phases in the Uterine Cycle? (Endometrial cycle)
- Menstrual Phase
- Proliferative Phase
- Secretory Phase
What is the menstrual cycle driven by?
feedback loops involving:
- Hypothalamic Kisspeptin & GnRH
- Pituitary LH & FSH
- Ovarian Oestrogen, Progesterone, Activin, Inhibin
Describe the menstrual cycle.
Day 1:
First day of bleeding (Blood & cellular debris from necrotic endometrial lining)
Ovulation:
~Day 14 (with surge of LH)
Length: Average 28d (21-35) >35 days = oligomenorrhoea
on the day after ovulation, body temperature increases by at least 0.5*C (due to progesterone)
(see diagram 38-39/68)
What does tubular fluid reabsorption result in?
concentration (induced by oestrogen)
What is secreted into the epididymal fluid?
Nutrients (e.g. fructose) and glycoproteins secreted
Induced by androgens
(See diagram 43/68)
How far does spermatozoa travel?
100,000 times its length from testis to Fallopian tube
Equivalent to 150km for a 1.5m human
What is semen made out of?
Spermatozoa (15-120 million/ml)
Seminal fluid (2-5ml)
Leucocytes
Potentially viruses (e.g. hep B, HIV)
What fraction of spermatozoa in ejaculate enter the cervix?
1/100
What fraction of spermatozoa in ejaculate gets through the cervix to the ovum?
1/10,000
What fraction of spermatozoa in ejaculate reach ovum?
1/million
What does seminal fluid contain?
- Fructose
- Citric acid
- Bicarbonate
- Fibrinogen
- Fibrinolytic enzymes
Where is seminal fluid secreted from?
Mainly from accessory sex glands:
- seminal vesicles
- prostate
- bulbourethral glands
Small contribution from:
- epididymis/testis
(See diagram 46/68)
What is the capacitation of sperm?
To achieve fertilising capability in the female reproductive tract
Occurs in the female reproductive tract
How is the capacitation of sperm achieved?
- Loss of glycoproteins ‘coat’
- Change in surface membrane characteristics
- Develop whiplash movements of tail
(See diagram 47/68)
What is required for the capacitation of sperm?
- Takes place in ionic & proteolytic environment of the Fallopian tube
- Oestrogen-dependent
- Ca2+-dependent
Describe the acrosome reaction.
- sperm binds to ZP3 (sperm receptor)
- Ca2+ influx into sperm (stimulated by progesterone)
- release of hyaluronidase + proteolytic enzymes (from acrosome)
What happens as the result of the acrosome reaction?
Spermatozoon penetrates the Zona Pellucida
See diagram 48-49/68
Where does fertilisation occur?
Fallopian tube
What reaction does fertilisation trigger?
Cortical reaction
What happens in the cortical reaction?
- cortical granules release molecules which degrade Zona Pellucida (e.g. ZP2 +3)
Therefore preventing further sperm binding as there are no receptors
Goes from haploid to diploid
(See diagram 50/68)
Describe the development of the conceptus.
- continues to divide as it moves down the fallopian tube to the uterus (3-4 days)
- received nutrients from uterine secretions
This free-living phase can last for 9-10 days until implantation.
(See diagram 52/68)
List the phases in implantation.
Attachment phase
Decidualisation phase
(See diagram 54-56/68)
What is the attachment phase?
Outer trophoblast cells contact uterine surface epithelium
What is the decidualisation phase?
Changes in underlying uterine stromal tissue (within a few hours)
What does implantation require?
Progesterone domination in the presence of oestrogen
What two key molecules are involved in the process of attachment?
Leukaemia inhibitory factor (LIF)
Interleukin-11 (IL11)
There are others involved (e.g. HB-EGF)
What is the role of LIF?
LIF from endometrial cells stimulates adhesion of blastocyst to endometrial cells
What is the role of IL11?
IL11 from endometrial cells is released into the uterine fluid, and may be involved in attachment
What occurs in decidualisation?
Endometrial changes due to progesterone
- glandular epithelial secretion
- glycogen accumulation in stromal cell cytoplasm
- growth of capillaries
- increase vascular permeability (can lead to oedema)
Which factors are involved in decidualisation?
IL11, histamine, certain prostaglandins, TGF-beta (which promotes angiogenesis)
What is angiogenesis?
Formation of new blood vessels
Which hormone is only present in pregnancy?
hCG (human chorionic gonadotropin)
(can only be produced by the placenta)
measured in blood or urine
What are the key hormones in pregnancy?
hCG
oestrogen (mainly oestriol)
human placental lactogen
progesterone
(see diagram 60/68 for hormone changes and effects during pregnancy)
Describe the progesterone and oestrogen production during pregnancy during the first 40 days.
produced in corpus luteum (in maternal ovary)
- stimulated by hCG (produced by trophoblast) which acts on LH receptors
essential for developing fetoplacental unit
inhibits maternal LH and FSH (-ve feedback)
(see diagram 62/68)
What happens to progesterone and oestrogen production from day 40 of pregnancy?
placenta starts to take over
Which maternal hormones increase during pregnancy?
ACTH Adrenal steroids Prolactin IGF1 (stimulated by placental GH-variant) Iodothyronines PTH related peptides
Which maternal hormones decrease in pregnancy?
Gonadotrophins Pituitary GH (due to placenta making its own growth hormone) TSH (due to placenta producing hCG; which has a similar action as TSH)
What is parturition?
labour
What cells does oxytocin affect in partruition?
myometrium and endometrial cells
What does oxytocin do (with some action from oestrogen and progesterone)?
- uterine contraction
- cervical dilation
- milk ejection
(see diagram 65/68)
What is prolactin for?
milk synthesis
Where is oxytocin made?
posterior pituitary gland
What is lactation?
breastfeeding
Describe the endocrine control of lactation.
suckling (stimulus) -> neural pathways -> hypothalamus -> pituitary
posterior pituitary -> [neurohypophysis] oxytocin
anterior pituitary -> [adenohypophysis] prolactin
therefore milk ejection and milk synthesis
(see diagram 67/68)
What is hyperprolactinemia?
galactorrhea due to high/excess prolactin
