Reproductive biology

Question 1

What are the 4 pelvic organs?

Answer 1

• Urinary bladder, Urethra, Reproductive systems, gastrointestinal system

Question 2

What is the urethra, and how does it differ in males and females?

Answer 2

Tube which begins at the bladder and ends in the external opening (perineum - pee hole)
Urethra is longer in males and is involved in the reproductive tract in males

Question 3

What are the 6 things that the female reproductive tract contains?

Answer 3

Ovary
Uterus
Vagina
Cervix
Uterine tubes (fallopian tubes)
Fimbriae

Question 4

What are fimbriae, in terms of the female reproductive tract?

Answer 4

Finger like projections found on the end of the uterine tubes
They catch eggs from the ovary into the uterine tubes

Question 5

Where exactly are the ovaries located, what do they do, and what is ovulation?

Answer 5

In shallow fossa (holes) on the lateral pelvic wall
Produce sex hormones and release mature ova (eggs)
Ovulation = when a follicle ruptures and releases an ova into the peritoneal cavity before being caught by the fimbriae

Question 6

What type of organ is the ovary and why? What is it the site of?

What are the 2 main zones of the ovary and what do they contain?

Answer 6

Endocrine organ as it releases the hormones oestrogen and progesterone

Site of oogenesis (formation of ova)

Peripheral zone - Cortex (outer zone)
Contains ovarian follicles with each follicle containing one ovum

Central zone - Medulla (middle)
Contains blood vessels

Question 7

What are the 2 functions of the uterine/fallopian tubes?

Answer 7

To transport ovum from the ovaries to the uterus
To be the site of fertilisation

Question 8

Where exactly is the uterus found and what shape is it?
What are the 3 areas of the uterus and where are they found?

Answer 8

On top of the bladder
Pear-shaped

3 Areas:
- Fundus = top of the uterus
- Body = middle
- Cervix = bottom (see summary sheet)

Question 9

Describe the 3 layers of the uterine wall, including where they are found and what their purpose is?

Answer 9

Endometrium = innermost mucosal layer and is divided into 2 separate layers:
- Functional layer = Thickens and becomes rich in blood vessels, shed during menstruation
- Basal layer = Regenerates the fresh functional layer during each cycle

Myometrium = Middle, muscular layer. Thickest layer, where contractions occur that are needed for childbirth and produce period cramps

Perimetrium = outermost, thinnest layer

Question 10

What are the 6 parts of the testes that make up the male reproductive tract and what does each of them do?

Answer 10

• Ductus deferens = Duct that goes from the testes to the urethra
• Spermatic chord = contains blood vessels and are formed by the ductus deferens
• Seminiferous tubules = where sperm is produced
• Rete testis = tubes where the seminiferous tubules meet
• Epididymis = where the sperm reach final maturation (Gains ability to swim and fertilise an egg)
• Leydig cells = found just outside the seminiferous tubules, produce testosterone

Question 11

What does semen contain?

Answer 11

Sperm and seminal fluid

Question 12

What is the hormonal axis for females called, and what happens in it?

Answer 12

HPO axis - Hypothalamus releases GnRH which targets the Anterior pituitary to release FSH and LH which targets the Ovaries to produce progesterone and oestrogen.
Progesterone and oestrogen have negative feedback effects on the hypothalamus and anterior pituitary (see summary sheet)

Question 13

What are the 5 hormones the HPO axis contains and what do they do in relation to the menstrual cycle and when are their levels high during the menstrual cycle??

Answer 13

• GnRH = stimulates the synthesis and secretion of FSH and LH from the anterior pituitary
• FSH = Stimulates growth of ovarian follicles and stimulates the follicles to produce oestrogen - high before ovulation, when follicles are developing
• LH = surge in LH causes ovulation to occur - high during ovulation
• Oestrogen = Secreted by the ovarian follicles, inhibits the secretion of FSH and stimulates the LH surge that causes ovulation - so high levels just before ovulation
• Progesterone = produced from the corpus luteum (matured egg after ovulation) and maintains the uterus lining in case an embryo is implanted - high levels after ovulation, when the corpus luteum is formed (see diagram on summary sheet)

Question 14

What is the hormonal axis for males called and what happens in it?

Answer 14

HPT axis
Hypothalamus releases GnRH which targets the anterior pituitary gland which releases LH and FSH which targets the testis which releases testosterone.

Testosterone has negative feedback affects on the hypothalamus and anterior pituitary gland (see diagram on summary sheet)

Question 15

What are 2 examples of female reproductive disorders?

Answer 15

PCOS and endometriosis

Question 16

What is endometriosis, what are the symptoms (5), how does this affect reproductive health, and what are the treatments available (3)?

Answer 16

Endometriosis = chronic, inflammatory condition where endometrial-like tissue grows outside the uterus (on the ovaries, fallopian tubes or pelvic lining)
The tissue responds to hormonal changes, causing pain and inflammation

Symptoms = chronic pelvic pain, painful periods (dysmenorrhea), pain during sexual intercourse (dyspareunia), infertility, and fatigue

Causes infertility

Treatments:
- Pain relief (NSAIDs)
- Hormonal therapies (birth control/GnRH antagonists)
- Surgical interventions (removing the tissue)

Question 17

What is PCOS, how does it affect reproduction, and what is it linked to?

How is it diagnosed using the Rotterdam criteria? (required symptoms)

What are the current treatments available? (3)

Answer 17

Endocrine disorder characterised by hormonal imbalances, irregular periods, and ovarian cysts.

Disrupts ovarian function and involves excessive androgen production (male hormone production) - can cause infertility

Linked to: genetics, insulin resistance (diabetes), and lifestyle factors.
Increase in insulin levels contributes to excess androgen production, worsening symptoms

Rotterdam criteria = must have at least 2 of the following to diagnose:
- irregular ovulation
- hyperandrogenism ( high levels of androgens, which are hormones that trigger male characteristics)
- cysts found in ovaries on Ultrasound scan

Current treatments to help symptoms:
- Medications (hormonal contraceptives to regulate cycles)
- Anti-androgens
- Met formin (type 2 diabetes medication)

Question 18

What are the 7 different cell types present in an ovarian follicle, and what do they all do? Where are they all found within the follicle?

Answer 18

• Basement membrane = structural support system - found on the membrane
• Mural granulosa cells = produces oestrogen in the follicular phase and progesterone in the luteal phase - found just within the cell
• Theca cells = Endocrine cells that produce androgens, essential for fertility - found on the outside of the cell membrane
• Cumulus granulosa cells = regulates the oocyte’s growth, maturation and meiosis - surround the oocyte in a small circle
• Oocyte = the egg itself
• Zona pellucida = extracellular matrix that surrounds the plasma membrane of the egg itself (found inside the cell). Helps to protect the egg and plays a role in letting sperm fertilise the egg
• Antrum = filled with follicular fluid - a mixture of blood plasma and secretions from the granulosa and theca cells. Helps to nourish and support the oocyte as it matures.
  Found in a gap in the mural granulosa cells, inside the cell
  (see original jotter for diagram)

Question 19

What are primordial follicles?
What causes menopause to happen and when abouts does it occur?

Answer 19

Follicles at the starting point of their development
When there’s only 1,000 primordial follicles (1,000 eggs) left - around ages 45-52

Question 20

what are the 6 stages of follicle growth (including the primordial) and what happens at each of them?

Answer 20

• Primordial = starts off with just the oocyte and small granulosa cells
• Primary = growth occurs (bigger than primordial), develops zona pellucida, bigger granulosa cells
• Preantral = bigger than primary follicle (grown), developed a base membrane and theca cells
  The first 3 stages are independent of FSH and LH
• Antral = Has grown (bigger than preantral), developed cumulus and mural granulosa cells, and an antrum - development from preantral to antral is FSH dependant
• Preovulatory = antrum is bigger (bigger gap), and the granulosa cells have started to break away (overall follicle growth has stopped)
• Ovulatory = oocyte with surrounding cumulus granulosa cell and zona pellucida is released from the follicle ready to be fertilised - development from preovulatory to ovulatory requires a surge in LH
  (see power point/ original jotter for diagram)

Question 21

What is a mono-ovular species and an example?
What is a poly-ovular species and an example?

Answer 21

Mono-ovular = one egg released during ovulation e.g. humans
Poly-ovular = more than one egg is released at ovulation e.g. dogs (animals with a litter of pups)

Question 22

When do the 2 meiotic arrests occur in oocyte development?
What are the 3 requirements of an oocyte to be capable of fertilisation?

Answer 22

• First meiotic arrest happens after prophase 1 and before metaphase 1 just before ovulation. Meiosis resumes once a surge of LH at ovulation occurs
• Second meiotic arrest occurs after Metaphase 2 and before Anaphase 2. Meiosis resumes after fertilisation occurs

Requirements to be fertilised:
- Re-entered meiosis after ovulation
- Extruded the first polar body (occurs at prophase 2) (smaller cell produced during the first stage of meiosis)
- Arrested at metaphase 2

Question 23

What cells does the prepubertal testes contain? (2)
What cells do the pubertal testes contain and what do all the cells do? (6) (include what is spermiation?)

Answer 23

Prepubertal = spermatogonial stem cells and spermatogonia (can’t produce sperm)

Pubertal:
- Sertoli cells = Provides nutrients and essential factors to developing sperm cells
Spermiation = mature spermatids are released from the Sertoli cells into the seminiferous tubules
- Leydig cells = stimulated by LH and is the primary source of testosterone in males
- Spermatogonial stem cells = stem cells in the testes that create sperm and maintain male fertility by reproducing to allow sperm to keep being produced - divide to produce primary spermatocytes
- Primary spermatocytes = diploid cells that divide into haploid secondary spermatocytes
- Secondary spermatocytes = haploid cells that are produced by primary spermatocytes undergoing the first meiotic division
- Spermatozoa (sperm) = microscopic male reproductive cells produced in the seminiferous tubules of the testes and are added to semen before ejaculation. Formed when the secondary spermatocytes undergo the second meiotic division (see summary sheet - might want to memorise the last 4 through summary sheet)

Question 24

What are the 5 stages involved in sperm transportation (from seminiferous tubules to ejaculation)?

Answer 24

• Starts in seminiferous tubules in the testes, where the sperm is produced
• Maturation = immature sperm travel to the epididymis where they mature and are stored for a period of time
• Vas deferens = during ejaculation, sperm is forcefully propelled from the epididymis into the vas deferens, which is a muscular tube that carries the sperm towards the urethra
• Seminal vesicles = as sperm enter the ejaculatory duct, it mixes with fluids from the seminal vesicles to form semen
• Ejaculation = rhythmic muscle contractions during ejaculation push the semen through the urethra and out of the body

Question 25

What is capacitation, when does it occur, and what 3 things does it involve? What reaction does capacitation allow to happen?

Answer 25

Preparing the sperm for fertilisation Occurs as sperm travel through the female reproductive tract Involves: - Changes in the sperm's membrane, cytosol, and cytoskeleton - Development of hyperactivated mobility - Generation of reactive oxygen species Acrosome reaction to fertilise the egg

Question 26

What trigger the acrosome reaction and what is the acrosome reaction's function?

Answer 26

Trigger = sperm coming into contact with the zona pellucida of the egg Function = released enzymes from the acrosome (top part of head of sperm) help the sperm to "digest" through the zona pellucida, enabling penetration (allowing the sperm to reach the oocyte)

Question 27

What abnormality is caused by aged eggs? (including what is aneuploidy and how abnormalities are tested)

Answer 27

Trisomy = meiosis doesn't occur properly, resulting in aneuploidy (chromosomes not separating properly), causes genetic abnormalities in the embryo Can get blood tests for trisomy caused syndromes e.g. down syndrome

Question 28

How much sperm needs to be deformed for a man to be considered as infertile? What 2 techniques can be used to improve chances of fertility when the man has deformed sperm?

Answer 28

More than 96 percent IVF and ICSI (sperm injection into egg)

Question 29

What 3 important things does the oocyte contains (after ovulation)? What 3 important things does the sperm contain?

Answer 29

Egg: - First polar body (located between the zona pellucida and cell membrane of the egg) (see jotter for diagram) - Cytoplasm containing ribosomes, mRNA, proteins, and mitochondria (normal cell contents) - Cortical granules (again, see jotter for diagram) Sperms: - Acrosome containing enzymes - Equatorial segment - part of the head where the sperm fuses to the egg (fusses side on) - Mitochondria - to provide energy for movement

Question 30

What are the 4 main roles of the zona pellucida?

Answer 30

- To protect the oocyte - Mediate species-specific recognition (prevents cross breeding, can only bread with other humans) - Prevents polyspermy = prevents fertilisation by more than one sperm which would cause the embryo to die - Protects preimplantation embryo from reabsorption

Question 31

What are the 5 stages of fertilisation and what occurs in each of them?

Answer 31

- Acrosome reaction = releases enzymes and exposes the IZUM01 ligand - transmembrane protein on the sperm - Zona pellucida penetration = Unknown sperm ligand allows the sperm to bind to to sperm receptor ZP2 (and ZP3?) on the zona pellucida, keeping the sperm in contact with it. This allows Acrosin and other enzymes digest a pathway through the zona pellucida. - Sperm-egg binding = IZUM01 ligand on sperm binds to the JUNO receptor on the egg, stabilised by the transmembrane protein Cd9 - Sperm-egg fusion = Microvilli engulf the sperm starting at the equatorial segment (segment where sperm bonded). The sperm is engulfed by pinocytosis (see jotter for diagram) - Polyspermy block and resumption of meiosis = meiosis 2 resumes. Polyspermy block via cortical reaction (more detail on separate flashcard)

Question 32

What is the cortical reaction? (2 steps)

Answer 32

- Cortical granules fuse with the the plasma membrane of the egg and the contents are released into the perivitelline space. These granules contain proteases, peroxidases, and polysaccharides - This changes the structure of the zona pellucida - cleaves ZP2 and removes oligosaccharides from ZP3 which prevents fertilisation by another sperm (polyspermy block)

Question 33

Once the egg is fertilised, it contains the pronucleus of the sperm and egg (haploid nucleus of egg and sperm). What happens to form the female pronucleus? (2) What happens to form the male pronucleus? (4) (formation of the zygote)

Answer 33

Female: - Meiosis 2 is completed (which forms a second polar body) - Nuclear membrane forms around the DNA Male: - Sperm nucleus decondenses - Nuclear membrane forms around sperm DNA - Sperm DNA is actively demethylated - Histones (involved in gene expression) replace protamine (inactive) in sperm chromatin (chromosomes)

Question 34

What are the 2 division stages involved in pre-implantation embryo development and where do these stages occur? (including what syngamy and blastomeres mean) Where is the embryo eventually implanted?

Answer 34

First, mitotic division to form 2-cell embryo: - Pronuclei move towards the centre of the egg and the DNA replicates - Pronuclear envelopes dissolve - maternal and paternal chromosomes merge on the spindle, forming a 2 cell embryo Syngamy = coming together of the gametic chromosomes (pronuclei merging together) Reductive division = series of rapid cell divisions without cell growth (cells get smaller and smaller as they divide). Known as blastomeres Blastomeres are totipotent - can differentiate into any cell, including cells that form the placenta (pluripotent can't form the placenta) Eventually divides enough to reach the implantation stage (blastocyst size) These stages occur in the fallopian tube Implantation stage embryo is implanted into the uterus

Question 35

What happens after the oocyte is implanted into the uterus?

Answer 35

Hatches from the zona pellucida

Question 36

What are the 3 main things that can go wrong during fertilisation and what do they mean for the embryo? (including what a hydatidiform mole and trophoblastic tumour is and what polyploidy means)

Answer 36

- Spindle may migrate towards the centre = could result in 2nd polar body not being extruded. - Spindle may disintegrate = maternal chromosomes may be lost. If fertilised this could lead to a hydatidiform mole (mass that forms inside the uterus). Could also lead to a benign (not harmful) trophoblastic tumour (tumours that develop in the uterus from cell found in the placenta) - Cortical granules migrate towards the centre = after fertilisation, contents may not be released into the perivitelline space, could cause polyspermy to occur, causing polyploidy (if 2 or more sperm fertilise egg, can end up with more than 2 sets of chromosomes - 3 sets if 2 sperm fertilise)

Question 37

What is the definition of infertility? What is primary infertility? What is secondary infertility?

Answer 37

Infertility = failure to conceive after 12 months of regular, unprotected sex, or 6 months for couples over 35 years Primary infertility = infertility of someone who has never conceived a child before Secondary infertility = infertility of someone who has had 1 or more children before (struggling to have another one)

Question 38

What are the 4 main causes of infertility for females and how?

Answer 38

-STIs = can lead to blocked fallopian tubes and ectopic pregnancies (embryo implants in fallopian tube instead of uterus). Can also lead to pelvic inflammatory disease - Ovulation disorders e.g. PCOS or premature loss of eggs (premature menopause as a result of genetic condition or chemotherapy) - Hypothalamic dysfunction = disrupts production of FSH and LH - Lifestyle factors like obesity, smoking, alcohol

Question 39

What are the 7 main causes of infertility for males and how?

Answer 39

- Hypogonadism (low testosterone) - Varicocele - enlarged veins near the testis - Testicular infection/cancer - Sexual dysfunction/injury (can't have sex) - Low sperm count, poor sperm mobility, abnormal sperm - Drugs (medicinal/recreational) - Lifestyle factors such as obesity, smoking and alcohol

Question 40

What are the 5 Assisted reproductive technology (ART) fertility treatments and in what situations they are used? (include what are the 3 type of fertility drugs used)

Answer 40

- Fertility drugs = for patients with PCOS, hormone imbalances, or irregular cycles Most common = Clomid, metformin, Gonadtropins - IVF = variety of issues - ICSI = sperm-related issues - Artificial insemination (usually with donor sperm) = for couples without fertility issues (e.g. single females or same-sex couples) - Use of donor sperm/eggs

Question 41

What does the fertility drug clomid do and what are the pros and cons? (include success rate)

Answer 41

Binds to oestrogen receptors in the hypothalamus to help trigger ovulation Pros = effective, easy, cheap Cons = can generate multiple ovulations/pregnancies, can increase risk of ovarian cancer Success rate = 73% ovulation rate

Question 42

What is the IVF procedure in detail, and what is it's success rate?

Answer 42

Ovarian stimulation - daily injections of FSH and LH/hcg to retrieve 10-14 eggs Eggs then fertilised and incubated into embryos Embryos then implanted back into the uterus Success rate = varies with maternal age. 85% in patients in their 20s 50% in patients in their 40s (failure = miscarriage)

Question 43

What is the ICSI procedure in detail and what is the success rate?

Answer 43

Basically same as IVF, but sperm is injected directly into the egg (in IVF sperm is just placed into the petri dish and fertilisation occurs naturally, no needle) Same success rate as IVF: 85% in patients in their 20s 50% in patients in their 40s (failure = miscarriage)