Monthly Archives: March 2013

11.4d Pregnancy & Birth

– earlier in the pregnancy, the embryo produces HCG (hormone)
– the hormone stimulates the corpus luteum in the ovary to continue to release progesterone and estrogen
– placenta: needed because the surface area to volume ratio decreases as the fetus increases
– placenta is made of fetal tissues
– fetus develops a amniotic sac that contains amniotic fluid
– this supports and protects the fetus
– in the ninth week of pregnancy, the placenta starts to release estrogen and progesterone in large quantities to sustain the pregnancy
– corpus luteum is no longer needed

Structure & Function

– maternal blood flows throw the spaces around the villi
– fetal blood flows in blood capillaries
– there is a placental barrier that separates the maternal and fetal blood

– during pregnancy, progesterone inhibits secretion of oxytocin by the pituitary gland and also inhibits contractions of the uterus
– at the end of the pregnancy, hormones produced by the fetus signal to the placenta to stop releasing progesterone, and the oxytocin is then released
– oxytocin stimulates contractions of muscles fibers in the uterus wall
– contractions push the baby out through the cervix and vagina

Chapter 26 Questions
1b) testosterone is used for spermatogenesis, develops the penis, maintains sex drive, and develops sexual characteristics


11.4c Fertilization

During intercourse, the sperm which is released into the vagina are stimulated to swim and they meet the egg.
1) the acrosome reaction
– zona pellucida is a coat of glycoproteins that surronds the egg
– the acrosome is a large membrane-bound sac in the head of the sperm
– when the sperm meets the zona pellucida, the contents of the acrosome are released
– this allows the sperm to force their way through
2) penetration of the egg membrane
– the acrosome reaction exposes an area of the membrane on the tip of the sperm that has proteins
– the first sperm that gets through the zona pellucida binds the membrane of sperm and egg fuse together
= fertilization
3) the cortical reaction
– cortical granules: vesicles located near the egg membrane
– there are thousands of these vesicles
– when activation of the egg has taken placed the contents are released from the egg by exocytosis
– the chemicals in the cortical granules interact with the glycoproteins in the zona pellucida
– this becomes a fertilization membrane and doesn’t allow any more sperm to enter into the egg

Data-Based Questions page 282

1) The maximum amount of live births are at the ages 20 to 24, from there, it is a downwards decline. From the teenage years, 20 to 24 had an increase.
3) They may not be ready and have the correct, full growth to carry and give birth to a healthy child
4) The women may be busy with other work, and not desiring to become pregnant at a younger age
5) The data shows that the ages 20 t0 24 are the less riskiest ages to become pregnant, therefore this is the ideal age.


11.4b Oogenesis

Oogenesis is the production of egg cells in the ovaries, the main type of ovary tissue is called the medulla, and the surrounding tissue is called the cortex. Oogenesis starts in the ovaries of a female fetus, the outer layer of the ovary is called germinal epithelium. Germs in the fetal ovary divide by mitosis and the cells formed move through the cortex. When the fetus is four to five months old, the cells divide by meiosis. Primary follicles is a cell that started to divide by meiosis, together with surrounding follicles cells. The epididymis are narrow tubes, which are used to pass the sperm out of the testes when they are fully formed.
Data- Based Questions page 278
1) the longer the sperm are, the higher cross section area of fibrous sheaths
2) the longer the sperm are, the area of the cross sectional fibrous sheaths increase
3) this may be because of the space, and the size that the animal is capable of holding and producing
4) there is no proven relationship for the size of sperm and the size of an animal


11.4a Spermatogenesis

Spermatogenesis occurs in the testes and is the production of the sperm. The testes are composed of mass narrow tubes with a small group of cells filling the gaps, which are called seminiferous tubules. These gaps are called interstices to the cells in them are interstitial cells. The outer layer of cells is called germinal epithelium, and is where the process of sperm production begins. Cells that have developed tails are called spermatozo (sperm). Large nurse cells in the wall of the tubule are called Sertoli cells.
Male and Female Gametes
Both of the male and female gametes contain haploid nucleus and both have microtubules organizing centrioles.

Data- Based Questions pg 276
1a) the amount of sperm produced in the summer is less than the sperm produced in the winter, yet the percent of % of normal sperm stays constant
1b) the cold weather in winter might stimulate the production of sperm
2a) Men aged around 18-20 have less sperm count than men aged around 20-45
2b) With with a matured age and steady hormones (after puberty) may affect the spermatogenesis
3) Men in Finland produce more sperm in both summer and winter therefore the hypothesis can be suggested to be true



Question #2)

a. Full employment is the point where most of the people who are willing and able to work in a nation are able to find employment. Economic growth is an increase in the total output of goods and services in a nation over time. Structural unemployment is a non- economic consequence of growth. Structural unemployment is when the labour’s skills do not match the skills demanded, for example, technology provides the same or better skills than the  labour force. As an economy grows, further advances in technology are bound to happen. In Japan for example, some of the supermarkets have already implemented a system where a customer can bill their products by themselves. This causes less demand for people who work as cash registration employees. This way, the unemployment rate increases.

b. As discussed above, the unemployment rate will increase structural unemployment is occurring. Therefore, the workers with insufficient skill’s household will get none or less income. For example, a cash register employee who can be replaced will be unemployed, compared to a doctor or civil engineer. Therefore, there is unfair balance of payments. For the households with less income, will have less disposable income and the demand for certain goods with decrease.

6.6b Male Reproduction & IVF

Human reproduction requires a sperm from a male and an egg from a female. Testosterone is the hormone that triggers puberty and the sexual drive in men. The abbreviation IVF stands for in vitro fertilization: fertilization can also happen outside the body in strictly controlled laboratory conditions.
in vitro fertilization (IVF) – getting the gametes :
1) down regulation: female takes a drug to stop her pituitary gland ordering it to stop producing FSH and LH hormones
2) super ovulation: follicules stimulated to develop by intramuscular injections of FSH and LH
3) follicle maturation: when the follicles reach 18mm they are stimulated to mature by an HCG injection
4) egg collection: a micropipette is placed on the ultrasound scanner and washes egg outs of the follicles
5) semen collection: man produces semen and collects it in a sample bottle
6) semen processing: semen is injected below a layer of sterile fluid, and later on the sperm that swum up into the fluid are collected
in vitro fertilization (IVF) – fertilization and implantation :
1) insemination: each egg is mixed with up to 100,000 sperm cells in a petri dish and is incubated at 37C till the day after
2) checking for fertilization: fertilization can be detected 12-20 hours after mixing eggs and sperm, two nuclei visible
3) embryo selection: the next day, the embryos are checked and the healthy four-cell embryos are selected for transfer when they are 2 days old
4) embryo transfer: up to three embryos are drawn into a plastic tube which is pushed into the uterus and the embryos are expelled
5) luteal support: extra progesterone is placed in the vagina as a tablet to ensure the uterus lining in maintained
6) pregnancy testing: two weeks after the embryo transfer, a pregnancy test can be done to see if an embryo is developing

Chapter 26 Question #3)

3a) the success rate of the IVF correlated with the mothers age. If the mother is older, then success rate decreases, and if the mother age is younger, the success of the IVF increases
3b) the success rate of the IVF increases as the number of embryos increases, and as the number of embryos decreases, the success rate of the IVF will decrease
3c) if the age of the mother increases, the chance of her conceiving twins decreases, therefore embryos can be planted in her


6.6a Female Hormones

Female Reproductive System
– estrogen & progesterone are two hormones that are always present in females during pregnancy
– these hormones assist development in the female genitalia
– if the gene tdf isn’t present, then the babies develop as females
Hormonal Control of the Menstrual Cycle
– humans are able to produce any time of the year
– an oocyte (egg), is inside a sac called a follicle
– the egg helps the endometrium thicken
– if no embryo is formed, the thickening breaks down and is passed out of the body during menstruation
– group of follicles are stimulated to grow
– when the follicles grow, the endometrium becomes thicker
– the most developed follicle releases an egg into the oviduct
– the other follicles degenerate
– when that follicle releases the egg, the body becomes corpus luteum
– further development of the endometrium prepares it for the implantation of an embryo
– if fertilization does not occur, the corpus luteum breaks down
– the thickening of the endometrium breaks down and sheds during menstruation
Hormonal Levels During the Menstrual Cycle
– pituitary hormones: FSH and LH are measured in nanograms and estrogen is measured in picograms
– first half of menstruation is called the follicular phase
– second half of menstruation is called luteal phase

Data-Based Questions page 272
1a) the higher amount of menstrual cycles, the higher bone density
1b) the neck of the femur has less cycles during the year, whereas the trochanter of the femur has many more cycles during the year, therefore the trochanter has more density.
2a) higher bone density is assisted by high diet in calcium, vitamin D, energy, and estrogen
2b) lower bone density is caused by low diet in calcium, vitamin D, energy, and estrogen
3a) the hormones levels may be affected when a female is exercising
3b) low body weights and eating disorders reduces the amount of protein, carbohydrates, and nutrition that is available to the body.