Reproductive physiology Flashcards
What is Biological sex?
Identifies gender
Results from chromosomes
Results in production of gametes i.e. Sperm/ Ova
What is the result of sexual reproduction
Offspring that differ genetically from both parents.
List 4 functions of sexual intercourse
Required for sexual reproduction
Sexual activity
Sexual pleasure
Human bonding
Which 3 systems are linked to parenting, fertilitly, reward and pleasure?
Control of movements by nigrostriatal tract;
Pathways for reward + pleasure in mesolimbic dopaminergic system.
Neuroendocrine pathways regulating fertility + parenting
What encourages procreation?
Activation of pleasure pathways in the brain
What is penile erection controlled by?
Thoughts in the brain (limbic system) via the spinal cord + efferent nervous system.
Tactile stimulus can activate the afferent system via the pudendal nerve, feeding into the spinal cord
Describe the changes that occur during penile erection
Increased PNS activity to smooth muscle of pudendal artery
Increases NO, which increases production of cGMP
Induces dilation of arterial smooth muscle
Counteracts SNS maintained myogenic tone
Increases blood flow in corpus cavernosum, compresses dorsal vein, restricting outflow of blood
Urethra protected from increased pressure by surrounding corpus spongiosum
What reverses the changes leading to penile erection? How can this mechanism be utilised therapeutically?
cGMP being de-activated by a phosphodiesterase
Viagra inhibits the phosphodiesterase, thus potentiating the effects of cGMP
What is the female erectile tissue? What occurs during erection?
Clitoris
Increases in size due to increased blood flow
Same mechanism as penile executive tissue
What are the main functions of the Male reproductive system?
Provision of androgens: to initiate + sustain male phenotype
Production of mature sperm
Describe the function and contents of the Testis and Epididymis.
Testis: contains seminiferous tubules (produce sperm) + Leydig cells (produce testosterone)
Epididymis: store sperm prior to ejaculation.
Describe the passage of sperm at ejaculation
Sperm pass through the vas deferens + mix with fluid from seminal vesicles.
Fluid leaves ejaculatory duct + passes to urethra where it mixes with secretions from prostate gland.
How does spermatogenesis occur through life?
Starts at puberty + is continuous
Sperm quantity + quality decrease with age
200 million/ day
Describe the HPG axis in males
Hypothalamus releases GnRH
GnRH stimulates anterior pituitary secretion of FSH + LH
FSH stimulates SERTOLLI cells to grow, produce androgen binding protein + Inhibin
LH stimulates LEYDIG cells to produce testosterone
Describe the feedback effects in the HPG axis in males
Testosterone downregulates production of GnRH, LH + FSH
Inhibin downregulates production of LH + FSH
List the 3 key tissues of the female reproductive system
Ovary: produces gametes (oocytes) + steroids (progesterone + estrogens)
Fallopian tube-:oocyte reaches uterus via this; providing an appropriate environment to maintain an oocyte
Uterus: conceptus normally implants here + is supported throughout pregnancy.
What is the function of Thecal and Granulosa cells? Where are they found?
T of developing follicles produce estrogens
G of Corpus Luteum produce estrogens + progesterone during 2nd half of ovarian cycle
Describe the process of oogenesis
Germ cells (44XX) divide to produce oogonia.
Oogonia divide mitotically to produce primary oocytes (diploid).
Primary oocytes enter the 1st meiotic division straight away but are halted in prophase of the 1st meiotic division = “miotic arrest”
Oocytes are inside primordial follicles, some enter process of atresia
Remain dormant for 12-50 years.
At puberty complete 1st meiotic division to form secondary oocytes (22X) + a polar body
Secondary oocytes complete 2nd meiotic division at fertilisation to produce ovum + 2nd polar body, with a pause in metaphase 2.
What is meant by the formation of a secondary oocyte and a polar body?
1 daughter cell retains cytoplasm and all resources
Other cell is just membrane and chromosomes (polar body)
Describe the female reproductive cycle occurrence in life
Puberty till ~45
Cyclical
Egg quality decreases with age
Describe the HPG axis in females
Hypothalamus releases GnRH
GnRH stimulates anterior pituitary secretion of LH + FSH
FSH stimulates ovary to produce E2 + development of the follicles
LH stimulates ovary to produce preogesterone
Describe the feedback effects in the HPG axis in females
Follicular phase: Oestrogen downregulates production of GnRH, LH + FSH
Midcycle: Oestrogen upregulates production of GnRH, LH + FSH, due to change in sensitisation, thus stimulating increased oestrogen production
Luteal phase: Progesterone downregulates production of GnRH, LH + FSH
What are the 2 cycles within the menstrual cycle?
OVARIAN CYCLE (ovary) ENDOMETRIAL CYCLE (endometrium is the lining of the uterus)
What are the phases of the ovarian cycle?
Follicular: Growth of ovarian follicle. Increased production of E2
Ovulation
Luteal: Corpus luteum produces progesterone + E2
What are the phases of the endometrial cycle? Which hormones are dominant in each phase?
Menstrual (decline in P): Shed blood + lining
Proliferative (E2): Stimulation of proliferation + increase in thickness
Secretory (E2+P): Production of nutrients, increased coiling of spinal arteries
What is 17 B Oestradiol abbreviated to?
E2
When are levels of oestradiol and progesterone highest during the menstrual cycle?
Luteal phase
When do LH and FSH peak during the menstrual cycle? Why?
Just before ovulation ~day 13
To accelerate growth of main follicle + release egg in process of ovulation
How does basal body temperature change during the menstrual cycle?
It rises slightly around the time of ovulation.
What causes the LH surge that stimulates ovulation?
Switch from negative to positive feedback of E2 in the HPG axis
Describe hormone production sites through the menstrual cycle
As Follicle develops, produces E2
Ovulation occurs
Generates corpus luteum- produces P + E2, which then controls endometrium until corpus luteum breaks down at end of cycle
Describe the process of spermatogenesis
Germ cells (44+XY) divide to produce spermatogonia.
These remain dormant until puberty where there is division of spermatogonia to produce more spermatogonia + primary spermatocytes (still diploid).
Primary spermatocytes enter 1st meiotic division to form secondary spermatocytes (haploid).
Secondary spermatocytes enter 2nd meiotic division to form spermatids.
Spermatids mature into spermatozoa. (22X or 22Y)
How long between release of secondary follicles from an ovary? What allows this?
56 days
Ovaries contain multiple follicles at all stages of development at any time
1 dominant follicle enters the latter stages to form a secondary (Graafian) follicle.
Describe the process and main events of Fertilisation
Deposition of sperm near cervix
Passage of sperm through uterus + into Fallopian tube
Swim to ampulla (Survival of fittest (a few days))
Capacitation
Meeting of egg with sperm
Fusion of egg + 1 sperm (within 24 hours post ovulation)
Acrosome reaction
Resumption of meiosis, formation of female pro-nucleus, release of 2nd polar body
Duplication of chromatids in pro-nuclei
Alignment of maternal + paternal chromosomes
Change in Zona Pellucida to prevent additional sperm fusing with zygote.
Initiation of mitotic (cleavage) divisions in embryo.
Why must the cervical mucus change mid cycle?
Cervical mucus is normally hostile to sperm (forms a physical barrier)
Changes mid-cycle to allow sperm to enter uterus
What is Capacitation? When must it occur?
Physiological changes spermatozoa must undergo to have ability to penetrate + fertilize an egg.
Before sperm meet the oocyte
What occurs in the acrosome reaction?
Acrosome exocytosis allowing penetration of Zona Pellucida (+ Coronal cells)
