Human and Molecular Reproduction Flashcards
What is testes determining factor (TDF)
A protein that promotes sex determination. TDF turns gonads into testes, no TDF produces ovaries.
What is testosterone
A hormone secreted by the testes causes the male genitalia to form, at puberty, this increases leading to sperm production and other developmental changes.
What is estrogen and progesterone
First secreted by the mother’s ovaries and then her placenta, it leads to the development of the female genitalia. At puberty, this causes egg release and other developmental changes.
What menstrual hormones are secreted by the pituitary
FSH - stimulates oocyte development
LH - matures oocyte and causes release (ovulation)
What menstrual hormones are secreted by the ovaries
Estrogen - develops endometrium, positive feedback on FSH and LH when early, negative when late
Progesterone - maintains endometrium, negative feedback
Menstrual Cycle
Follicular Phase (Day 1-4) - Menstruation, endometrium shed, FSH increases stimulating follicle development.
Ovulatory Phase (Day 5-14) - FSH and follicles stimulate estrogen release which stimulates endometrium development and LH. Peak in LH causes ovulation.
Luteal Phase (Day 14-28) - Fall in LH, corpus luteum forms releasing progesterone maintains the endometrium and inhibits FSH and LH
Causes of infertility in men and women
Women - Ova not maturing or being released, abnormal uterus, antibodies in cervical mucus
Men - Unable to ejaculate, low sperm count/low mobility, blocked vas deferens
Describe the process of IVF
- FSH and LH stimulate many egg releases
- eggs are collected
- eggs are fertilized and collected in a dish
- blastocytes are selected and developed into embryos
- up to 3 embryos can be selected
- a test can be taken to see if an embryo ‘took’
William Harvey’s deer investiagtion
- Dissected female deer to observe changes in sexual organs, found none
- Aristotle believed a male seed + menstrual blood = fetus, Harvey put this to rest
- His biggest problem was that he did not have a microscope.
The process of spermatogenesis
- Germinal epithelium cells are always dividing produce 2n spermatogonium
- Primary spermatocytes form which are 2n
- Secondary spermatocytes form through meisosi 1, which are n
- Spermatids are produced through meiosis 2, which are n
- Sertoli cells help spermatids develop into spermatozoa (n)
- Sperm detach from Sertoli cells and are carried out of the testis in the seminiferous tubule
The process of oogenesis
- oogonium are formed through mitosis
- oogonium undergoes meiosis 1, primary oocytes form in primary follicles
- a. First meiotic division, polar body forms, secondary oocyte continues into meiosis 2
- b. The secondary oocyte develops into an egg, released into the fallopian tube, remaining follicle cells form the corpus luteum which produces progesterone
- Egg completes meiosis 2 if it is fertilized forming the ovum and a polar body
- polar bodies eventually degenerate
Internal and external fertilization
External is mostly aquatic species:
- eggs are released followed by sperm
- susceptible to environmental variation, so large quantities of both are produced
Internal is mostly terrestrial animals:
- prevents dehydration of gametes and developing embryo
What is polyspermy?
Multiple sperm enter the egg. Egg will die.
What are the four steps of fertilization?
- Sperm pushes through follicular cells and bind to receptacles in zona pelucida
- Enzymes are released from the acrosome and digest the glycoprotein-based zona pelucida
- Membrane of the sperm and ova fuse.
- cortical granules releases proteases into the zona pelucida to harden and prevent polyspermy
- Influx of Ca2+ into ova prompts the completion of meiosis 2 - nucleus of sperm is deposited into the ovas cytoplasm and fuses with the ovas nucleus forming a diploid zyogote
Implantation of the blastocyst
- Zygote undergoes many miotic divisions and becomes a morula
- Morula divides and forms a fluid-filled cavity in the middle
- It is now called a blastocyst which forms in the fallopian tubes
- Implants in the endometrium in the uterus
- embryo receives nutrients and o2 through tissue fluid through the endometriums capilaries
HCG and hormonal control of pregnancy
- Blastocyst releases HCG, which increase over 8-10 weeks
- Causes corpus luteum to secrete estrogen and progesterone, inhibiting LH and FSH, no eggs
- progesterone maintains endometrium where blastocyst develops and placenta forms
Placenta
- 10 weeks - placenta takes the hormonal role of corpus luteum
- Releases: Estrogen maintains uterine lining. Progesterone maintains endometrium and prevents contractions
- exchanges material between mother and fetus
What materials are exchanged through the diffusion of the placenta
Mother to fetus:
- O2, H2O, lipids, glucose, AA, vitamins, minerals, antibodies
Fetus to mother:
- Urea, H2O, CO2, HCG
Placenta structure
- carries deoxygenated blood from fetus via umbilical arteries
- carries oxygenated blood from fetus via umbilical vein
- Mother’s arteries deposits blood to the intervillous space, bathing villi more greater absorption
- Chorionic (fetal portion) villi increase exchange area
- Placental cells secrete hormones and anti-immune substances to prevent an attack.
Hormonal control of birth
- Rise in estrogen no longer prohibits progesterone, causing contractions in smooth muscle
- Contractions stimulate stretch receptors, oxytocin released from pituitary
- Oxytocin grows contractions
- Contractions continue after birth to eject placenta
Relation of adult size and newborns in mammals
- Altricial mammals give birth to helpless offering
- Precocial mammals give birth to mobile offspring
- Relationship b/w adult size, gestation period and development stage of offspring
