D3.1 Flashcards

Question

# The Menstrual Cycle Oocyte?

Answer 1

* The term for the **egg before it's matured.** * The **gamete** forming during **meiosis**. * At the **end of Meiosis |, it's called the primary oocye**. * It **begins Meiosis || and is called a secondary oocyte**, and is released and often then called an egg.

Answer 2

* Following fertilization the sperm's nucleus enters the egg, but **the two sets of chromosomes remain separate inside temporary nuclear membranes**. * These are called pronuclei and they undergo DNA replication separately first before merging ahead of mitosis to grow the zygote.

Answer 3

* If a women (for IVF) is given injections of FSH that cause elevated levels of the hormone that multiple follicles in each ovary are matured --> superovulation. * Meaning, when the surgeon goes to extract eggs from the ovary to fetilize, they can get many eggs.

Answer 4

The hormone GnRH is produced & released by the hypothalamus and trvales just to the pituitary to stimulate the release of FSH and LH. * It controls the entire process of sexual development and gamete maturation and release. * FSH and LH are then released from the pituitary into the bloodstream to travel to the ovaries. * The hormone is regulated by feedback mechanisms - positive and negative at different times.

Answer 5

* Secreted by the anterior pituitary * It's target cells are the follicle cells in the ovary. * It stimulates their growth and maturaiton and as they develop, they release estrogen. * FSH also stimulates sperm production in males

Answer 6

* Released by the anterior pituitary, generally in response to a positive feedback loop, whereby the increasing levels of estrogen stimulate the release of higher levels of LH. * When LH levels are high, ovulation is triggered and the matured oocye is released from the ovary. * LH levels therefore must be regulated to release the egg at its ideal maturity for fertilization. * The LH surge is very short and used by ovulation tests to predict ovulation within a 1-2 day window.

Answer 7

*Estrogen is a broader term for multiple sex hormones with different functions like sexual development* * An important hormone is estradiol, which plays the role in the monthly menstrual cycle. * It rises in response to maturing follicles and stimulating the further release of high levels of FSH and LH needed for ovulation * . It thickens the lining for possible fertilization.

Answer 8

The hormone responsible for the luteal phase (second hald of the cycle). * It rises after ovulation and is secreted by the corpus luteum for about 10-12 days post ovulation. * Retains the thick lining of the endometrium for possible pregnany and send negative feedback messages to stop FSH and LH release. * If implantation occurs, progesterone levels say high by the embryo. * If not, they drop post ovulation leading to menstruation.

Answer 9

IVF is an invasive and expensive medical breathrough that can enable pregnany for couples with infertility. * Women intiially takes birth control medication to stop her natural cycle. * She then is injected with FSH to mature many eggs. * Those eggs are retrieved from the ovary and the male provides a semen collection. * Fertilisation occurs in the lab and a 5-day embryo is then inserted into a uterus to develop there.

Answer 10

A group of hormones that are (generally) released from the anterior pituitary, under the instructinons of GnRH released from the hypohtalams. * This stimulates the ovaries and testes to mature gametes. * The two main gonadotropins are Follicle Stimulating Hormone (FSH) and Lueinizing Hormone (LH). * These both stimulate the 'gonad's. *Note that hCG is also a gondadotropin, however is only released during pregnancy.*

Answer 11

As a term it encompasses meiosis to form the nuclei as well as cell differentiation that causes the development of the flagella for motility.

Answer 12

Diploid germ cells that go through meiosis to become mature sperm cells. * The spermatogonia first goes through mitosis, creating two small diploid cells. * One of those two will enter meioisis to become four sperm, while the other will grow and go through mitosis again in the future. * This keeps number of stem cells consistent.

Answer 13

Large, tightly packed cells inside the seminiferous tubules that provide nutrients for the developing sperm. * Also referred to as nurse cells as they take care of the developing sperm * Secrete some proteins that aid in development

Answer 14

The process by which egg cells are produced. * Involves the meiotic divisions of the genetic material and the cell specialization to form the large and complex structure of an egg cell. * More complex than spermatogensis, as the oocyte arrests twice during meiosis, in Prophase | and then in Metaphase ||.

Answer 15

* Humans only aim to release one mature egg each month to limit births. * However, meiosis must divide the DNA into 4 nuclei for reduction division to occur. * As only one egg will be matured, cytokinesis is unequal, with the secondary oocyte keeping majority of the cytoplasm and the polar body being essentially just a nucleus. * This secondary oocyte only compeltes meiosis || if it's fertilized, if that happens, another polar body is created.

Answer 16

A diploid germ cell captable of entering meiosis to develop into a primary oocyte in the ovary. * The oogonium stalled in Prophase | is still a diploid cell, but called a primary oocyte so oogoniums are only found in utero.

Answer 17

The event when more than 1 sperm fertilizes an egg. * Would result in a triploid set of chromosomes, so not a succesful pregnancy. * Hence, there are adaptations in place to prevent polyspermy from occuring to faciliate successful pregnancies.

Answer 18

A complex extracellular matrix (glycoprotein layer) that changes in consistency before and after fertilization. * Before, it's like jelly, wih accessible sperm binding sites. * After a sperm breaks through to fertilize the egg, enzymes are released that causes the zona pellucida to harden, making it impenetrable to sperm.

Answer 19

* GnRH is released from the hypothalamus during puberty. * It's triggered by a protein (kisspeptin) that's released late in childhood to stimulate puberty. * GnRH then releases FSH and LH that stimulates ovaries and testes. * They then release estrogen and testosterone which lead to the development of secondary sexual characteristics. * In women there'a delay (few years) before FSH and LH levels are sufficient to initiate menstruation.

Answer 20

**Oocytes**: terms for immature eggs that haven't finished meiosis. **Primary Oocyte**: Cell that has arrested in Prophase | of Meioisis, occurs in utero * The oogoniums begin Meiosis | before birth but stop in Prophase | as a diploid cell. **Secondary Oocyte**:During puberty this oocyte completes Meiosis | and has entered Meioisis ||, called a secondary oocyte. * It's now a halpoid cell. * It pauses at Metaphase || and is ovulated as such and only finishes Meiois || if fertilized. * Hence, the egg that is ovulated is a secondary oocyte.

Answer 21

* The zona pellucida covers the binding sites for sperm to insert their nuclei into the egg. * This prevents easy penetration of sperm (could otherwise result in polyspermy) * Sperm do however need to be able to get through this layer. * This is done by using the enzymes that are contained in the acrosome head. * **The acrocome head detatches and the enzymes then degrade the coat to reach the binding site.**

Answer 22

* After sperm has inserted its DNA into the egg cells, these vesciels contain enzymes called cortical granules (in the cytoplasm of the egg, and will release their enzymes into the cell membrane) * These enzymes cause a reaction that leads to the **hardening of the zona pellucida and resulting removal of attachment sites** * This prevents polyspermy upon fertilizaiton

Answer 23

Once a fertilized egg, which enters mitosis, exponentially increases and reaches the uterus (7-10 days post ovulation). * It's 100 cells big with a distinct shape, consisting of an outer layer of cells, inner group of cells and fluid cavity. * The stage the embryo is at for implanting into the endormetrium.

Answer 24

The surrounding layer of cells around the spherical blastocyst. * These cells will go on to form the fetal portion of the placenta and the umbilical cord.

Answer 25

The process by which the embryo sinks into the highly vacularized endormetrium wall of the uterus. * Following fertilization, the embryo is 100 cells but very small, and has limited nutrients used for simple metabolism. * For growth to occur the embryo must access the mother's blood source. * The thick, vacularizied layer was sustained by high progesterone levels to ensure the embryo can be embedded in the uterus to access the nutrients from blood supply.

Answer 26

Lab produced anitbodies (proteins, not living cells) that are made from pure cultures of B cells that are cloned and will mass produce in a single type of antibody that is sensitive to one single antigen. * Created for targeted specific tools to treat disorders * Produced and used in home pregnancy tests

Answer 27

Specialized tissues that arises from the trophoblast of the embryo and material uterine tissue. * The 'pancake' shaped (flattened disc) structure that enables a connection between maternal and fetal blood vessels. * Necessary, as the embryo grows to maintain the surface area to volume ratio needed for efficient diffusion of materials. * The maternal blood leaves its capillairies to best faciliate diffusion with embryonic capillaries.

Answer 28

A protective sheath that covers the important fetal blood vessels, which carry blood to and from the placenta for material exchange. * Forms two vessels that deliver deoxygenated blood to the placenta, and one larger vessel that returns oxygentated blood to the fetus's heart (a vein).

Answer 29

The fetal blood vessels branch into numerous projections (placenta villi) that are surrounded by maternal blood (outside of vessels in intervillous spaces). * These projections are spread out to maximise the surface area for rapid diffusion of materials between mum and baby.

Answer 30

A peptide hormone that faciliates bonding - **made in the hypothalamus and released by the posterior pituitary**. * Has a role in attachment, but specifically for reproduction as it **stimulates labour/birth and the onset of breastfeeding**. * Operates by positive reinforcement loops in both birth & breastfeeding.

Answer 31

The period in a female's life when her mentrual cycle first becomes less predictable and then eventually stops altogether. * Generally begins in a woman's 40s, but there's variation. * Occurs becuase **ovaries stop producing estrogen & progesterone, usually because there's no viable follicles maturing to trigger the release anymore**. * Hormone changes cause symptons: trouble sleeping, hot flushes, muscle & hair loss.

Answer 32

* The trophoblast cells of the embryo secrete hCG and later the embryonic placenta cells secrete it. * Remember that the corpus luteum will secrete progesterone for about 12 days post ovulation and then will break down and progesterone levels drop, stripping the endometrium. * If pregnancy is successful, the embryo must signal the corpus luteum to continue producing progesterone until placenta is fully formed.

Answer 33

Monoclonal antibodies can be made that specifically bind to the anigen on hCG. * These antibodies are attached to pregnancy tests. * If hCG is present it binds to these antibodies. * Often a second antibody with a dye has been mixed in (often urine) * So, if hCG is present thr dyed antibodies will stick to it and then it will also bind to the anitbodies attached to the tsick creating a visable dye if hCG is present.

Answer 34

* During the menstrual cycle progesterone contributes to the **maintaining of the uterine wall**. * During early pregnancy its necessary to help the embryo stay implanted in the uterus * When placenta has formed it continues to release progesterone **that inhibits uterine contractions to prevent labour**. * As the fetus approaches a full term of pregnancy it stops producing as much hormone, allowing for contractions to occur which releases oxytocin.

Answer 35

* Fetus grows larger, causes strain on walls of uterus which then increases. * The production of progesterone decreases, the uterus starts to contract which pushes the baby's head into the cervix. * This causes the cervix to signal the hypothalamus to signal the pituitary to release oxytocin. * Oxytocin then causes the uterine muscle contractions (more strain on the cervix and thus more oxytocin) * This positive loop continues with rising oxytocin levels until birth is completed

Answer 36

HRT is supplementary oestrogen and progesterone that helps increase low levels at menopause. **Advantages**: Can alleviate symptoms like hot flushes, mood swings, and emotional changes. The added estrogen can strengthen bones and reduce the risk of osteoporosis. **Disadvantages**: Higher estrogen is linked to breast cancer, and correlation to CDH.

Answer 37

Refers to the fact that flowers contain both male and female reproductive structures. * One flower produces male and female gametes. * Male parts are called the staMEN * Female parts are called carpel or pistil.

Answer 38

The food source of the seed. * The female ovule maintains polar bodies/nuclei * Then when pollen enters, one fertilizes the ovule to make a 2n zygote and another pollen nucleus fertilizes the two polar bodies and this triploid mass develops into the endosperm.

Answer 39

* Pollen from a flower can sometimes land on a stigma of the same plant. * To reduce inbreeding, this often fails to create the pollen tubes necessary for it to reach the ovary. * This is done through evolution of alleles. * **Plants can't create pollen tubes if the same incompatibility alleles are present**. * **Alleles are an adaptation to prevent self-pollination**

Answer 40

The stages of early growth in a seed that will allow it to develop into a plant. * An adaptation plants have to manage harsh environments is for seeds to remain dormant until favourable conditions for successful growth. * When this happens, seeds begin to germinate.

Answer 41

The uptake of water from the soil via a small opening (micropyle). * Water triggers the start of metabolic pathways which break down food stores to increase rates of cell resp. and protein synthesis. * This allows plant embryo inside seed to grow. * The growing plant & absorbed water both exert pressure for the embryo to sprout out of tough seed coat.

Answer 42

The endosperm becomes used for plant growth - the original endosperm becomes a cotyledon, **which sprout off from the developing stem - they are the first 'leaves'** and can photosynthesize after sprouting. * Not as effective as mature leaves that develop later in growth. * If it splits into two leaves - dicot, one leaf - monocot.

Answer 43

**Male**: Pollen. Pollen consists of individual pollen grains which is actually two haploid nuclei to faciliate the double fertilization. **Female**: Ovule. One Ovary contains multiple ovules, which can each be fertilized and become on embryo --> seed. * Ovary becomes the fruit (many seeds in a fruit) * Each ovule contains many haploid nuclei (one will be fertilized and others will contribute to the endosperm & seed structure.

Answer 44

**Cross Pollintation**: the landing of pollen from one flower onto the flower of ANOTHER PLANT (not just another flower). * Generates more genetic diversity & the hybrid offspring are often healthy and stronger. **Self Pollination**: Still creates non identitical offspring, as the gametes are unique, but is associated with inbreeding challenges (reduced health due to greater genetic similarity.)

Answer 45

Purpose: **To attract pollinators**. * Often colourful, scented and sometimes contain guidelines that attract the pollinator into the center of the flower.

Answer 46

Purpose: **Surrounds the developing flower bud, protecting it and photosynthesizing for it.** * Often green and will often fall back and look small after blooming.

Answer 47

Purpose: **The top part of the stamen & contains pollen sacs that make & release pollen** * Appear large and green before pollination and then shrivelled and furry when covered in pollen.

Answer 48

Purpose: **stalks that hold up anthers, and elevate them away from the stigma (female part) of the plant.** * This helps ensure that pollen is picked up by an approaching pollinator and transferred without landing on its own stigma.

Answer 49

Purpose: **The top external part of the pistil/carpel (female part of the plant) that often excretes a sticky subtance/is spread out to increase surface coverage, which sticks pollen grains on it from travelling pollinators/wind.**

Answer 50

Purpose: **The tube that connects the stigma to the ovary, which allows the stigma to be help higher to increase the chance of pollenation.** * Once pollen lands, pollen tubes are formed in the style that transport the pollen grains down to the ovary containing the ovules.

Answer 51

Purpose: **Produces and stores the female gamete (ovules).** * The ovary contains ovules that can be fertilized at once. * When ovules are fertilized, the ovary will ripen into a usually edible fruit intended to attract herbivores to help dispere the seeds.

Answer 52

* Mature the pollena dn ovules at different times, so that ovules are immature at the time of pollen release. * Use of wind/water can move pollen away, as are animal pollinators (bees, birds, bats). * Self-incompatability mechanisms assist if pollen does land on a flower of the same plant.

Answer 53

Done by herbivores, water or wind - some seeds can be ejected out/have prickles to stick on fur. * Seeds need to be in an envrionment that has nutriends for growth. * It's often beneficial for the new offspring plant to be away from parent plant that's already utilizing that location's resources --> hence dispersal/movement of seeds away.

Answer 54

1. Water to initiate germination 2. Oxygen for cell. resp for ATP to allow for growth. 3. Appropriate temperature & pH for the enzymes involved in the metabolic processes to function.

D3.1 Flashcards

Reproduction (79 cards)