Year 2 Midterm Flashcards
6.6.1 Draw and label diagrams of the adult male and female reproductive systems
Female Reproductive System
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6.6.2 Outline the role of hormones in the menstrual cycle, including FSH (follicle stimulating hormone)
FSH (Anterior pituitary) –
- stimulates follicular growth
- stimulates estrogen secretion(from developing follicles
6.6.2 Outline the role of hormones in the menstrual cycle, including estrogen
Estrogen (Ovaries(developing follicle))
- development of endometrium
- stimulates LH secretion(follicular phase)
- inhibits LH and FSH(luteal phase
6.6.2 Outline the role of hormones in the menstrual cycle, including LH (luteinising hormone)
LH( Anterior pituitary)
- surge causes ovulation
- development of corpus luteum
- stimulates progesterone secretion
6.6.2 Outline the role of hormones in the menstrual cycle, including progesterone
Progesterone(Ovaries(corpus luteum))
- thickening of endometrium
- inhibits LH and FSH (luteal phase
6.6.3 Annotate a graph showing hormone levels in the menstrual cycle, illustrating the relationship between changes in hormone levels and ovulation, menstruation and the thickening of the endometrium
Follicular Phase:
FSH stimulates growth of several follicles
Dominant follicle secretes estrogen
Estrogen inhibits growth of other follicles (and FSH)
Estrogen stimulates development of endometrium
Ovulation:
A surge in LH causes ovulation (egg release)
Rupturing of follicle creates a corpus luteum
Luteal Phase:
Corpus luteum secretes progesterone (and estrogen)
Progesterone stimulates development of endometrium
Estrogen and progesterone inhibit FSH and LH
Corpus luteum degrades over time
When corpus luteum degrades, progesterone levels drop
Without progesterone, endometrium cannot be maintained
Endometrium is sloughed away (menstruation)
No longer inhibited, FSH can start menstrual cycle again
If fertilisation of egg occurs, the zygote releases a hormone (hCG) which maintains the corpus luteum
11.4.8 Compare the processes of spermatogenesis and oogenesis, including the number of gametes and the timing of formation and release of gametes
Similarities:
Both processes result in the formation of haploid gametes
Both processes involve mitosis, growth and meiosis
Differences:
Location: sperm- testis, oogenesis-ovary
Number of gametes produced: sperm-life long production(millions), egg-fixed amount only about 400 mature
gametes/germ cell: sperm-four, egg-one
beginning off process: sperm-puberty,egg-during fetal development
timing of gamete formation: sperm-continious, egg-once a month menstural cycle
end of process: sperm-lifelong but reduces, egg-stops at menopause
timing of gamete release:sperm-any time, egg-monthly cycle
meiotic divisions:sperm-uninterrrupted, egg-arrested
germ line epithelium:sperm -involved in gamete production, egg- not involved in gamete production
11.4.9 Describe the process of fertilisation, including the acrosome reaction, penetration of the egg membrane by a sperm and the cortical reaction
When the sperm enters the female reproductive tract, biochemical changes to the sperm occur in the final part of its maturation (capacitation)
The sperm is attracted to the egg due to the release of chemical signals from the secondary oocyte (chemotaxis)
Fertilisation generally occurs in the oviduct (fallopian tube)
To enter the egg membrane, the sperm must penetrate the protective jelly coat (zona pellucida) surrounding the egg via the acrosome reaction
The acrosome vesicle fuses with the jelly coat and releases digestive enzymes which soften the glycoprotein matrix
The membrane of the egg and sperm then fuse and the sperm nucleus (and centriole) enters the egg
To prevent other sperm from penetrating the fertilised egg (polyspermy), the jelly coat undergoes biochemical changes via the cortical reaction
The cortical granules release enzymes that destroy the sperm-binding proteins on the jelly coat
Now fertilised, the nucleus of the secondary oocyte completes meiosis II and then the egg and sperm nuclei fuse to form a diploid zygote
11.4.10 Outline the role of hCG in early pregnancy
The endometrium is a blood-rich environment in which an implanted zygote can grow and it is sustained by the hormone progesterone
If progesterone levels aren’t maintained (i.e. the corpus luteum degenerates), then the endometrium will be sloughed away (menstruation)
A fertilised zygote develops into a blastocyst that secretes human chorionic gonadotrophin (hCG)
hCG maintains the corpus luteum post-ovulation so that the blastocyst can remain embedded in the endometrium and continue to develop
Gradually the placenta develops and produces progesterone (at around 8 - 10 weeks), at which point the corpus luteum is no longer needed
11.4.11 Outline early embryo development up to the implantation of the blastocyst
After fertilisation, the zygote undergoes several mitotic divisions to create a solid ball of cells called a morula (at around 4 days)
Unequal divisions beyond this stage cause a fluid-filled cavity to form in the middle - this makes a blastocyst (at around 5 days)
The blastocyst consists of:
An inner mass of cells (this will develop into the embryo)
An outer layer called the trophoblast (this will develop into the placenta)
A fluid filled cavity (called the blastocoele)
These developments all occur as the developing embryo is moving from the oviduct to the uterus
When the blastocyst reaches the uterus, it will embed in the endometrium (implantation)
11.4.12 Explain how the structure and function of the placenta, including its hormonal role in secretion of estrogen and progesterone, maintain pregnancy
Structure and Function
The placenta is a disc-shaped structure that nourishes the developing embryo
It is formed from the development of the trophoblast upon implantation and eventually invades the uterine wall
The umbilical cord connects the fetus to the placenta and maternal blood pools via open ended arterioles into intervillous spaces (lacunae)
Chorionic villi extend into these spaces and facilitate the exchange of materials between the maternal blood and fetal capillaries
Nutrients, oxygen and antibodies will be taken up by the fetus, while carbon dioxide and waste products will be removed
The placenta is expelled from the uterus after childbirth
Hormonal Role
The placenta also takes over the hormonal role of the ovary (at around 12 weeks)
Estrogen stimulates growth of the muscles of the uterus (myometrium) and the development of the mammary glands
Progesterone maintains the endometrium, as well as reduces uterine contractions and maternal immune response (no antibodies against fetus)
Both estrogen and progesterone levels drop near time of birth
11.4.13 State that the fetus is supported and protected by the amniotic sac and amniotic fluid
The fetus develops in a fluid-filled space called the amniotic sac
Amniotic fluid is largely incompressible and good at absorbing pressure, and so protects the child from impacts to the uterine wall
The fluid also creates buoyancy so that the fetus does not have to support its own body weight while the skeletal system develops
Finally, amniotic fluid prevents dehydration of the tissues, while the amniotic sac provides an effective barrier against infection
11.4.14 State that materials are exchanged between the maternal and fetal blood in the placenta
The fetus relies on the exchange of materials across the placental wall to grow and develop:
Maternal blood to fetal body
oxygen, glucose, lipids, water,minerals, vitamins, antibodies,hormones, amino acids
Fetal blood-maternal blood
carbon dioxide,urea, waste hormones, water
11.4.15 Outline the process of birth and its hormonal control, including the changes in progesterone and oxytocin levels and positive feedback
The process of childbirth is called parturition and is controlled by the hormone oxytocin
After nine months, the fetus is fully grown and takes up all available space in the uterus, stretching the walls of the uterus
This causes a signal to be sent to the brain, releasing oxytocin from the posterior pituitary
Oxytocin inhibits progesterone, which was inhibiting uterine contractions
Oxytocin also directly stimulates the smooth muscle of the uterine wall to contract, initiating the birthing process
The contraction of the uterine wall causes further stretching, which triggers more oxytocin to be released (causing even more contraction)
Additionally, the fetus responds to the cramped conditions by releasing prostaglandins which cause further myometrial contractions
As the stimulus causing oxytocin release is increased by the effects of oxytocin, this creates a positive feedback pathway
Contractions will stop when labour is complete and the baby is birthed (no more stretching of the uterine wall)
6.6.5 Outline the process of in vitro fertilisation
Stop normal menstrual cycle (with drugs)
Hormone treatments to develop follicles (FSH to stimulate follicle growth ; hCG for follicle maturation)
Extract multiple eggs from ovaries
Sperm selected, prepared (capacitation) and then injected into egg via intra-cytoplasmic sperm injection (ICSI)
Fertilisation occurs under controlled conditions (in vitro)
Implantation of multiple embryos into uterus
Test for pregnancy is conducted to see if implantation was successful
