Pregnancy

Question 1

Describe the basic formation and voyage of semen

Answer 1

Semineferoud tubule: spermatozoa released into white matter, Sertoli cells in tissue and leydig cells around. The tubular fluid is reabsorbed-induced by oestrogen (from testosterone via aromatise) - produces by Sertoli cells. Nutrients and glycoprotein secreted into epidural fluid under the influence of androgens.

Voyage: from testes to Fallopian tube.

Question 2

Describe the contents of the seminal fluid and process of ejaculation

Answer 2

Seminal fluid: mainly from accessory sex glands (seminal vesicles, prostate, bulbourethral gland) and some small contribution from epididymis/ testis.

Ejaculation: semen, Leukocytes, potentially viruses. They enter cervix, into ovum.

Question 3

Describe the capacitation of sperm and its binding to ovum

Answer 3

When sperm first leaves male, it’s not ready for activation to occur so it:

1. Loses glycoproteins coat (acrasome enzyme)
2. Change in surface membrane characteristics (in the ionic environment if Fallopian tube, oestrogen dependent and calcium dependent
3. Develop whiplash movements of tail.

Sperm binds to ZP3 receptor on ovum, this causes influx of calcium into sperm, this causes the activation of luteal phase by progesterone. Release of hyaluronide and proteolytic enzymes (from acromose). The spermatozoa penetrates the zona pellucida (glycoprotein of the ovum)

Question 4

Describe the process of fertilisation and development of the conceptus

Answer 4

Fertilisation occurs in the Fallopian tube, triggers corticol granules which degrade the zona pellucida, therefore prevents further sperm binding as no receptors, the cells go from haploid to diploid, all Ca dependent.

The conceptus continues to divide as it moves down the Fallopian tube to uterus, it receives nutrients from uterine secretion (free loving phase of 9/10 days - waits for HCG)

Question 5

Describe the process of implantation

Answer 5

1. Attachment phase: outer trophoblast cells contract uterine surface epithelium (LIF from endometrial secretory glands)
2. Decidualisation phase: changes in underlying uterine strolls tissue (due to progesterone - glandular epithelial secretion, glycogen accumulation in stromal cell cytoplasm, growth of capillaries, increase vascular permeability), the factors involved - IL-11, histamine, prostaglandins, TGFb (to promote angiogenesis)
3. Requires progesterone domination in the presence of oestrogen.

Question 6

Describe the hormonal changes during pregnancy

Answer 6

1. HCG first goes up, from placenta, maintains corpus luteum, source of progesterone and oestrogen (acting on LH receptor - inhibits LH/FSH).
2. human placental lactogen promotes nutrients (insulin resistant)
3. Oxytocin - uterine contraction, milk ejection, cervical dilation.
4. Prolactin - milk synthesis.

Question 7

Describe the physiological changes in maternal hormones

Answer 7

Increase: ACTH, adrenal steroids, prolactin, IGF1, iodothyronines, PTH related peptide

Decrease: Gonadotrophins, Pituitary GH, TSH.