Reproduction Flashcards
What is the function of the epididymis?
Transports and stores spermatoza produced in testes Epididymis stimulates maturation process of sperm Site of breakdown of sperm if it is not ejaculated
What does the seminal fluid contain?
Bicarbonate (neutralise vaginal acidity),fructose,citrate, fibrinogen, fibrinolytic enzymes
What is the function of bicarbonate in the seminal vesicles?
Helps neutralise the acidic environment of the female reproductive tract
Where is the spermatic cord formed?
Deep inguinal ring
What structures does the spermatic cord contain?
Testicular artery
Pampiniform plexus (veins)
Autonomic and genitofemoral nerves (nervous supply to testicles)
Lymph vessels
Vas deferens
Which nervous systems stimulate erection and ejaculation?
Erection - Parasympathetic
Ejaculation - Sympathetic Point and shoot
What muscles does the penis contain?
2 x Corpora Cavernosa
1 x Corpora Spongiosum
What does the bulbo-urethral gland secrete?
Sugar-rich mucus into urethra for lubrication and contribute to pre-ejaculatory emissions from penis (seminal fluid)
How does the parasympathetic nervous system cause an erection?
Causes vasodilation of blood vessels going into the penis.There is more blood flow into the penis and the enlardged arteries push on the veins which occludes venous outflow and causes an erection.
Why is the testes suspended in the the scrotum?
Keep temperature 2-3 degrees lower than body If temperature increases then sperm production ceases
What is the lymphatic drainage of the testes?
Drains into para-aortic lymph nodes.
What is the vas deferens?
Tube from epididymis into seminal vesicle transporting mature sperm AKA - ductus deferens
Which layer of connective tissue forms the septa of the testes and which contains all blood vessels?
Septa are formed from tunica albuginea
Blood vessels contained in tunica vasculosa
Outline the arterial blood supply and lymphatic drainage of the testes
Arterial blood supply - Testicular arteries from the aorta via spermatic cord Lymphatic drainage - Para-aortic lymph nodes
Which organ can allow male sterilisation by vasectomy?
Vas deferens (minimal incision required)
Outline the lymphatic drainage in the female reproductive tract
Ovaries: para-aortic lymph nodes
Uterus/vagina: lliac, sacral, aortic, and inguinal lymph nodes
What do the ovaries sit inside?
Peritoneal cavity (remainder of organs outside)
What structures in the fallopian tube aid in the movement of the egg into the uterus?
Cilia and spiral muscle
Where does fertilisation of the egg occur?
Ampulla i.e. widest part of fallopian tube
How is the uterus supported?
Levator ani, coccygeus muscles and ligaments (broad, round, uterosacral)
What is the uterus lined by?
Endometrium
List the layers of the uterus
Perimetrium, myometrium (smooth muscle layer sensitive to hormones) and endometrium
Which layer of the uterus is shed during menses and why?
Endometrium Due to vasoconstriction of arterioles → Ischaemia/necrosis causing shedding and haemorrhage of menstruation
Outline the arterial blood supply of the ovaries and uterus/vagina
Ovaries → Ovarian arteries from aorta
Uterus/vagina → Uterine arteries (from internal iliac artery)
How is the sterility of structures above the cervix maintained?
Periodic shedding of the endometrium in the menstrual cycle,thick mucous,narrow os (hole in middle of cervix),pH<4.5
How much mature sperm is produced per second?
Around 1500
Explain why in general, men are continuously fertile?
Spermatogonia undergo differentiation and self-renewal → pool available for subsequent spermatogenic cycles throughout life. The pool of germ cells is not depleted
When does gametogenesis begin in males?
At puberty
Before birth, describe how the number of female gametes changes?
Multiplication of Oogonia to 6 million/ovary Form Primary Oocytes within ovarian follicles (=primordial follicles) These begin meiosis (halted in prophase) Some primordial follicles degenerate (atresia) At birth 2 million/ovary remain
Describe the process of spermatogenesis
Diploid germ cell (spermatogonium) divides to form diploid Primary Spermatocytes via mitosis
Diploid Primary Spermatocytes divide via meiosis to form Haploid Secondary Spermatocytes
Haploid Secondary Spermatocytes divide by 2nd meiosis to form Haploid Spermatids
Haploid Spermatids differentiate to form Haploid Spermatozoa
Does the sperm or the egg determine the sex of the baby?
Sperm
What is the function of the sertoli cell and where is it found?
It is found within the seminiferous tubules of the testes.>It has FSH receptors-Supports the process of spermatogenesis
- Supports developing germ cells by
-Assisting movement of germ cells to tubular lumen
-Transfer nutrients from capillaries to developing germ cells
-Phagocytosis of damaged germ cells - Hormone synthesis
-Inhibin and Activin (feedback on FSH)
-Anti-mullerian hormone (important in development of anatomy in men)
-Androgen-binding proteins
Which reproductive hormones are released by the Testes?
Androgens
-Testosterone
-Dihydrotestosterone
-Androstenedione
Inhibin (inhibits FSH)
-Activin (activates FSH) Oestrogens(from androgen aromatisation)
Which hormone are oestrogens derived from?
Testosterone
What are the functions of oestrogen in males?
Preservation of bone mass, sexual behaviour
What are the names of the cells that have FSH and LH receptors respectively in men?
Sertoli - FSH receptor
Leydig - LH receptor
What is the function of the leydig cell and where is it found?
Found outside of the seminiferous tubules, between them. Inside the testes it has a pale cytoplasm and is rich in cholesterolIt has LH receptors
It has a function in hormone synthesis
-Upon stimulation by LH, it secretes androgen hormones:
-testosterone (oestrogens formed from this)
-androstenedione
-dehydroepiandrosterone (DHEA)–> can be aromatised by aromatase enzyme to form oestrogens
What is the term for the first menstrual cycle in females?
Menarche
What are polar bodies?
Formed as a result of the first and second meiotic divisions in oogenesis.They are haploid and formed along side the secondary oocyte and ootids.Very low cytoplasm structures that get shed.
How does Oogenesis occur?
2nd trimester of pregnancy–>
-Oogonia (germ cells) in foetus undergo mitosis to develop into diploid primary oocytes (forming primordial follicles)
Process haulted until menarche
At menarche–>
-1st meiotic division of primary oocytes to form haploid secondary oocytes and polar bodies (these are shed).
Process haulted until just before fertilisation
After sperm fusion–>
-2nd meiotic division of secondary oocytes to form haploid ootids and polar bodies (these are shed).
-Ootids differentiate to form mature ova which are fertilised
Describe the steps involved in folliculogenesis.
- Primordial follical (Primary Oocyte at birth)
- Primary (preantral) follicle:
-Primary Oocyte and layers of granulosa cells and outer theca cells
3.Secondary (Antral) follicles:
-Fluid-filled cavity (antrum) develops
-Development of FSH and LH receptors - Mature (graafian/preovulatory) follicle:
-Formed towards the end of menstrual cycle
-Forms due to LH surge
-Secondary oocyte formed
5.Ruptures surface of ovary - Formation of corpus luteum (follicle without egg)
-Progesterone and oestrogen (stim by LH/HCG)
-In pregnancy, progesterone and oestrogen production taken over by placenta - If fertilisation occurs–> corpus albicans:
-Placenta produces HCG which keeps corpus luteum alive, to allow continued production of progesterone and oestrogen - If no fertilisation–> corpus luteum degenerates
Which type of follicle is most prevelant in polycystic ovarian syndrome?
Secondary (antral) follicles
What reproductive hormones are produced by the ovaries?
Oestroogens
-Oestradiol (classically measured in a blood test)
-Oestrone
-Oestriol
Progestogens (made by corpus luteum towards end of menstrual cycle)
-Progesterone
Androgens
-Testosterone
-Androstenedione
-DHEA (not in adrenals)
Relaxin (involved in relaxation of ligaments around pregnancy)
>Inhibin (negative feedback on FSH)
If there is no pregnancy, the corpus luteum degenerates and there is a withdrawal of progesterone. What effect does this have?
Vasoconstriction of aterioles in the endometrium causing pain and shedding. This leads to menstruation.
What hormone does the morning after pill contain? Why?
High dose progesterone.
Levels go up and then go down very rapidly causes shedding of the endometrium.
What is the location and function of theca cells?
Associated with outer part of ovarian follicle
Supports folliculargenesis:
-Structural and nutritional support of growing follicle
Hormone synthesis:
-LH stimulates synthesis of androgens
What does overactivity of theca cells cause?
High androgen levels. Typically seen in PCOS. PCOS patients have lots of follicles and hence more theca cells.
What is the name of the condition caused by increased androgen production by Theca cells?
Polycystic Ovarian Syndrome
What is the location and function of granulose cells?
Associated with inner part of ovarian follicles
Hormone synthesis:
-FSH stimulates granulosa cells to convert androgens produced by theca cells to oestrogens by action of aromatase enzyme
-Secretes Inhibin and Activin (feedback 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)
Why are leydig cells pale?
Because they are cholesterol rich
Describe the Hypothalamic-Pituitary-Gonadal (HPG) Axis
1.Kisspeptin neurons in the hypothalamus release kisspeptin
2. Kisspeptin activates kisspeptin receptor on GnRH (gonadotropin-releasing hormone) neurones in the hypothalamus
3. GnRH is secreted and passes through the hypophyseal portal circulation down to anterior pituitary
4. GnRH acts on gonadotrophs in the anterior pituitary
5. Gonadotrophins i.e. LH and FSH are released into systemic circulation
6. LH and FSH arrive at gonads where there are receptors to these hormones on leydig, sertoli, granulosa, and theca cells
7. Oestrogens, progesterones, and androgens are secreted
Can GnRH be detected in blood tests?
No, because it is only released locally into the hypophyseal circulation and not the systemic circulation. By the time they do enter the systemic circulation, its concentration is to minute to be detected in a blood test
When should Testosterone levels be tested?
In the morning as they are the highest then
Is the release of GnRH and consequently, LH and FSH continuous or pulsatile?
Pulsatile
What does the pulsatile release and continuous release of GnRH cause?
Pulsatile release causes appropriate levels of LH and FSH to be maintained while continuous release supresses the synthesis and secretion of LH and FSH leading to infertility.
Where do testosterone and oestrogen affect their feedback mechanism and what type of feedback is it?
They might have either positive or negative feedback on gonadotrophs (anterior pituitary) or the kisspeptin neurones (hypothalamus).
It is mostly negative but can switch to a positive feedback for instance in the mid-cycle surge (LH).
What is hyperprolactinaemia?
Tumour in prolactin secreting cells (lactotrophs in the anterior pituitary)
Too much prolactin made
Prolactin binds to prolactin receptors on the kisspeptin neurons in the hypothalamus
Inhibits kisspeptin release
Decreases in downstream GnRH/LH/FSH/Testosterone/Oestrogen
Leading to oligomenorrhea (>35d menses) or amenorrhea (3-6m no menses) / Low libido / Infertility / Osteoporosis
What is oligonmenorrhea?
Infrequent menstrual periods (less than 6-8 per year) >35d menses
What is amenorrhea and what are the types?
Absence of mentruation.
Primary amenorrhea:girl does not get her first period by age 15
Secondary amenorrhea:woman who already menstruates does not get her period for 3 months or more
How do patients with hyperprolatinaemia present in clinic?
Lactation despite not having given birth because of increased prolactin levels–> galactorrhoea (milkynipple dischargeunrelated to the normal milk production of breast-feeding)
Halted menstruation (oligomenorrhea/secondary amenorrhea)
At what stage in life is GnRH released in pulses in females?
After menarche
Describe the three main stages of the ovarian cycle
1. Follicular Phase:
Primary follicle → Secondary follicle → Mature follicle
Hormone changes during the Follicular phase:
-FSH increases from days 1-7 as it can bind to the FSH receptors on the granulosa cells to produce aromatase
-LH binds to LH receptors on the Theca cells to produce Androstenedione which is converted into Oestrogen by Aromatase
-Oestrogen negatively feedbacks to reduce the FSH and LH released by the Anterior Pituitary
-Follicle with most FSH receptors(Least FSH dependent) at this point continues to grow (Dominant Follicle) and the rest die off
-Dominant follicle produces more oestrogen and this positively feedbacks to produce more LH and FSH
2. Ovulation:
This surge of FSH and LH causes a rupture of the ovarian follicle and the Oocyte is released
3.Luteal Phase:
Corpus Luteum → Regression → Corpus Albicans
Hormone changes during Luteal phase:
-The remenants of the ovarian follicle forms a Corpus Luteum which is made up of leutinised theca and granulosa cells which continue forming androstenedione and oestrogen
-Leutinised Granulosa cells increase the activity of enzymes responsible for converting cholesterol into pregnenolone so more Progesterone is produced than oestrogen so progesterone becomes the dominant hormone
-Progesterone inhibits the release of LH and FSH
-Leutinised Granulosa cells also release inhibin which reduces the secretion of FSH
-Corpus Luteum → Corpus Albicans which doesn’t make hormones so low oestrogen and progesterone so spiral arteries collapse and functional layer of endometrium sheds
Describe the three stages of the uterine cycle
Menstrual phase: Old Endometrial lining sheds and causes menstrual bleeding (5 days)
Proliferative Phase: High Oestrogen levels stimulate–> thickening of endometrium, growth of endometrial glands and emergence of spiral arteries, raises lining of cervical mucus (more hospitable to sperm) (day 11-day 15)
Secretory Phase: High progesterone so–> spiral arteries grow longer and uterine glands secrete more mucus (thickens - less hospitable for sperm) (after day 15, window for fertilisation starts to close)
What does being hypogonadal mean?
Low testosterone in males, low oestrogen in females
Does the pulsatile nature of GnRH release change in males and females?
The pulse is fairly constant in males and changes in females depending on the phase of the menstrual cycle in which they are in
When is the feedback by FSH and LH positive on the hypothalamus and anterior pituitary gland?
Just before ovulation. Switch from negative to positive feedback. Big spike in FSH and LH which helps release the egg.
Does body temperature increase after ovulation?
Body temperature increases by at least 0.5 degrees Celcius due to Progesterone
How much of its length does a sperm travel from the Testis to the Fallopian tube?
100,000x its length
How do you clinically test if a woman has ovulated?
- Day-21 progesterone (this is when progesterone peaks). If above 10, there has been proper ovulation because the corpus luteum has formed.
- Ultrasound to look into ovaries and check if the corpus luteum has formed.
What percent of the testes make up the sperm generating machinery?
90%
Which hormone induces tubular fluid reabsorption in the male reproductive tract?
Oestrogen
Which hormone induces nutrient and glycoprotein secretion into the epididymal fluid?
Androgen
What is the concentration of spermatozoa in semen?
15-120 million/ml
What is the volume of ejaculant/seminal fluid approximately?
2-5 ml
What are the contents of semen?
-Spermatozoa
-Seminal fluid
-Leucocytes (WBCs)
-Might potentially contain viruses if the man is infected with an STI like Hepatitis B, HIV
Approximately how many spermatozoa reach the ovum?
1 in a million
Where is Seminal Fluid released from?
Seminal Vesicles (behind bladder, above prostate)
Prostate
Bulbourethral glands
Small contribution from epididymis/testis
What is the normal pH of the cervix and why might this normal pH be disturbed?
4.5. If woman takes antibiotics, this might affect the microbiota (bacteria) which control the pH in the cervix.
What is the meaning of the capacitation of sperm?
Achieving fertilising capability in the female reproductive tract.
What are the steps that constitute the capacitation of sperm?
- Loss of glycoprotein coat
- Change in surface membrane characteristics
- Develop whiplash movements of tail
Where does the Capacitation of Sperm occur?
In ionic and proteolytic environment of the Fallopian tube
What 2 chemicals is the Capacitation of Sperm reliant on?
Oestrogen, Ca2+
Describe the Acrosome Reaction?
Sperm binds to ZP3 receptor on the egg (Sperm receptor)
Causes a Ca2+ influx into sperm (also stimulated by progesterone)
Release of hyaluronidase and proteolytic enzymes from acrosome
Breakdown of glycoprotein coat (zona pellucida) around egg
Spermatozoon penetrates the Zona Pelllucida
What triggers the cortical reation?
Fertilisation
What is the cortical reaction?
Once the sperm enters the ovum, cortical granules release molecules which degrade the Zona Pellucida>Therefore any further binding of sperm to ZP2 or ZP3 is prevented as there are no receptors
What happens if a fertilized ovum remains/sticks in the fallopian tube?
Ectopic pregnancy
What is meant by the conceptus?
The conceptus includes all the structures that develop from the zygote, both embryonic and extraembryonic
What occurs in the Attachment phase of Implantation?
Outer trophoblast cells contact uterine surface epithelium
What is the day 4 embryo called?
Morula
What is the day 5 embryo called?
Blastocyst
What changes occur in the Decidualisation phase of Implantation?
Changes in underlying uterine stromal tissue
Endometrial changes due to progesterone:
-Glandular epithelial secretion
-Glycogen accumulation in stromal cell cytoplasm
-Growth of capillaries (need for increased blood supply to support pregnancy)
-Increased vascular permeability (oedema)
What hormones do both phases of Implantation of the blastocyst require?
Progesterone domination in the presence of oestrogen
During the attachment of the blastocyst to the endometrial lining, what are the factors involved that aid this adhesion?
Leukaemia Inhibitory Factor (LIF) (endometrial cells)
Interleukin-11 (IL-11) (endometrial cells)
Sometimes HB-EGF
Which cells are Leukaemia Inhibitory Factor and Interleukin-11 secreted from?
Endometrial cells
What factors are involved in the Decidualisation phase?
IL-11, Histamine, Certain Prostaglandins, TGF-beta (promotes angiogenesis)
In the first 40 days how is oestrogen and progesterone produced during pregnancy?
Produced by corpus luteum
Stimulated by hCG (produced by trophoblasts i.e. cells which go on to make the placenta) which act on LH receptors
Inhibits LH and FSH and hence prevents menstruation
What is the function of human placental lactogen?
Changes the metabolism of the pregnant mother
Why do HCG levels only go up in the beginning and then diminish?
Initially it goes up to help support the corpus luteum to continue making oestrogen and progesterone.
After the development of the placenta from the trophoblast cells, the placenta takes over and produces these hormones instead.
Hence HCG is no longer needed to keep the corpus luteum intact.
From day 40 of pregnancy how is progesterone and oestrogen produced?
By the Placenta
Do both the mother and foetus contribute to the production of progesterone and oestrogen?
Yes
Which hormones are increased during pregnancy?
ACTH: for placental synthesis and release of biologically active corticotrophin releasing hormone
Adrenal Steroids
Prolactin: increased lactotrophs in response to physiological need to develop breast tissues and to prepare for milk production
IGF1: stimulated by placental growth hormone variant
Iodothyronines (T4 and T3): TSH is decreased but T4 and T3 is increased because HCG can stimulate thyroid hormone secretion–> increased T4 and T3 because of increased metabolic demand on body
Parathyroid hormone related peptides: provides Ca2+ for growth of bones of foetus. These PTH related peptides normally come from breast tissue.
What effect does oestrogen have on prolactinomas?
Stimulate an increase in size of the prolactinoma
What defect might a growing prolactinoma cause?
Visual defect–> pushes on the optic chiasm causing bitemporal hemianopia
Glactorrhea
How can a prolactinoma be assessed during pregnancy? Why might prolactin levels not be measures?
Prolactin levels will anyway be high because of pregnancy
Instead, visual fields can be assessed during each trimester to ensure there is no peripheral vision loss.
Otherwise, an MRI can be taken and these are generally safe to do during pregnancy.
Which hormones are decreased during pregnancy?
LH and FSH (gonadotrophins): -ve feedback by progesterone
Pituitary growth hormone: Placenta makes own GH
Thyroid stimulating hormone: hCG has same alpha sub-unit as TSH so similar structure and less TSH needed for T4 and T3 synthesis
What processes does oxytocin stimulate during partruition?
Uterine contraction–> contraction of muscles in myometrium
Cervical dilation
Milk ejection
Which hormones are involved in parturition?
Oestrogen, cortisol, oxytocin
Where are receptors to oxytocin found?
On myometrial cells
What is Prolactin responsible for when there is a suckling stimulus on the nipple?
Milk Synthesis
Which hormones are responsible for milk production and milk ejection?
Prolactin and oxytocin respectively
Explain the endocrine control of lactation.
Suckling at nipple (stimulus)
Neural pathways from nipple goes up to hypothalamus producing a positive signal
Signal to pituitary gland
Posterior pituitary (neurohypophysis) secretes oxytocin
Anterior pituitary (adenohypophysis) secretes prolactin
Oxytocin causes milk ejection
Prolactin causes milk production
