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Sexual reproduction


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fertilized egg
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zygote

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Sexual reproduction - Marcador

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Sexual reproduction - Detalles

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How does a placenta form?
Partly from an embryo's tissue and partly from uterus
Stages of implantation
1. Ovulation- A mature follicle bursts and releases an egg into the oviduct 2. Fertilization- A sperm haploid nucleus fuses with an egg haploid nucleus forming a diploid zygote. 3.Zygote divides 4. A ball of cells is formed. 5. The cells in the ball keep dividing as it moves down the oviduct. It is now called an embryo. 6. Implantation- The embryo sinks into the soft lining of the uterus and placenta forms
How does embryo obtain food?
From yolk of an egg
How does a zygote divide?
By means of mitosis
Implantation
After about six days, embryo implants itself in the uterus wall. As the embryo grows, a placenta develops.
Piece of info
If fertilization occurs then corpus luteum does not disintegrate- it continues to divide producing progesterone to maintain and thicken uterus wall.
Piece of info
Blood from the baby flows continuously to and from placenta through umbilical cord. In the placenta, baby's blood comes very close to mother's blood so substances pass between mother and baby by diffusion and active transport.
Describe what happens when identical twins are formed.
A single zygote splits into two separate embryos. Both embryos have identical DNA.
Describe what happens when twins are formed(non-identical).
Two eggs released from the ovary at the same time. Each egg is fertilized by a different sperm.
Fertilization process
Haploid nucleus from a sperm fuses with haploid nucleus of an egg cell. Only one sperm fertilizes the egg. As the head of the sperm enters the egg, it triggers off the formation of an extra cell membrane around the egg. This stops any sperm entering the egg. The sperm's tail is left outside the egg. The head contains a nucleus and this fuses with the egg's nucleus. Both are haploid(23 chromosomes). After fertilization, a diploid zygote is formed(46 chromosomes).
Copulation
Sexual intercourse
What is fructose used for?
The sperm use fructose in the semen to provide energy.
What does the fluid from seminal vesicles do
Provide food/nutrients for sperm
Describe process of sexual intercourse
Man's penis becomes hard and erect to penetrate woman's vagina. Ejaculation(release of sperm) occurs due to contractions of the sperm ducts and other muscles. As the sperm pass along the sperm duct and urethra, they are mixed with a fluid from seminal vesicles and prostate gland to make a sticky fluid called semen. Semen is ejaculated from penis into vagina.
Release of sperm
Ejaculation
Describe ovulation process
First, a follicle develops inside an ovary. The development of follicle is stimulated by FSH. The developing follicle secretes oestrogen. Levels of oestrogen steadily increase in blood. The oestrogen makes the uterus lining thick and spongy. LH and FSH are secreted by the pituitary gland throughout this whole time. These two hormones stimulate follicle to keep secreting oestrogen. When the follicle is fully developed, there is a surge in the production of LH. This causes ovulation to take place. The now empty follicle stops secreting oestrogen. It becomes corpus luteum. The corpus luteum secretes progesterone. Levels of LH and FSH fall. Progesterone keeps the uterus lining thick, spongy and well supplied with blood in case the egg is fertilized. If not, corpus luteum disappears gradually and progesterone is no longer secreted so uterus lining breaks down and mensuration occurs. A new follicle develops and the cycle begins again.
How can AID be controlled as there's no cure?
1. Educating the public and the precautions to be taken 2. Never sharing or exchanging needles 3. Staying with an STD- free partner 4. Using a condom or any other barrier of contraception which prevents direct contact between body fluids of the two partners 5. Treating all blood and blood products used in transfusion to destroy AIDS virus
Diaphragm advantages or disadvantages
Adv: effective if fitted correctly. Dis: Fitting must be done by doctor but after that a woman can put it in and out when needed.
Diaphragm or cap
Circular sheet of rubber placed over the cervix at the top of the vagina. Spermicidal(sperm-killing) cream is first applied around the edges. Sperm deposited in the vagina cannot pass through into uterus.
Condom advantages and disadvantages
Adv: safe method of contraception and prevents infection transmission such as gonorrhea and HIV from one partner to another
Condom
Placed over an erect penis and traps semen as it is released, stopping it from entering vagina
Advantages of breast feeding
1. Baby receives antibodies from mother and not by baby formula 2. No formula milk can exactly replicate human milk so the baby does not get the best mix of nutrients 3. Formula milk is often based on cow's milk to which some babies may be allergic to 4. Breast fed babies do not become over weight 5. Helps form a mother-baby bond 6. Breastmilk is FREE and does not need to be strerilised.
Postnatal care
For first few days, breasts secrete a yellow watery fluid called colostrum on which baby feeds. Colostrum is rich in protein and contains antibodies to protect baby from diseases. After about three days, the milk is produced. At first, the baby feeds 10 to 12 times a day. The more the baby feeds , the more milk is produced.
Afterbirth
Contractions of the uterus continue to push the placenta until it has been expelled through vagina. Labor is then complete!
Delivery
Contractions of the uterus push the baby through cervix. Baby is born head first. Once the baby is out, mucus is cleared from its nose and mouth and once the baby is breathing, the umbilical cord is tied in two places and cut.
Dilation
When birth starts, uterus begins to contract rhythmically. This is the beginning of labor. Contractions become stronger and more frequent. The opening of cervix gradually widens(dilates) sufficient to allow baby's head to pass through. The amniotic sac bursts and amniotic fluid is released breaking of the waters. Labor takes 4-12 hours on average.
Gestation period
From fertilization to birth. Piece of info: few weeks before birth, the fetus comes to lie with head downwards just above cervix.
What are the secretion of female sex hormones controlled by?
Two other hormones secreted by the pituitary gland in the brain called LH and FSH.
How is HIV transmitted?
1. Host to host through intravenous drugs users sharing unsterilized needles. 2.Semen from one partner to the blood of another, if there is any tearing of tissues during sexual intercourse 3. From an infected mother's blood to her baby blood during birth process 4. In untreated blood during blood transfusion
Gonorrhoea
Cause by bacterium. Symptoms: severe pain on urination(especially in males) since the bacterium invades the tissue of the urethra. Discharge of pus from urethra in the end of the penis in males. This infection may spread to produce inflammation of the uterus in females and epididymis in males. The disease is not fatal but can lead to sterility.
Sexually transmissible diseases
Disease spread through sexual contact
What is the dangerous virus pregnant woman are under risk of?
Rubella producing rash and fever. If rubella crosses placenta, it can cause serious harm to fetus and born deaf with disabilities. In many countries, teenage girls are offered vaccinations.
Embryo also called as--------
Foetus once recognized as human being
Amniotic sac(amnion)
Inside uterus, embryo becomes enclosed with a sac called amnion which is filled with or secretes amniotic fluid which protects embryo from damage and maintains a suitable temperature and shock absorber.
What does the placenta produce?
Oestrogen and progesterone(corpus luteum produces) to stimulate growth of uterus and mammary glands
What substances pass from mother to baby?
Food and oxygen antibodies other substances which may be in mother's blood like alcohol, chemicals from cigarettes, viruses...
What substances pass from baby to mother?
Carbon dioxide, urea and other wastes
Uterus
Implantation and development of foetus
Males puberty?
Testes start secreting testosterone
Puberty
Stage where sex organs mature
Female
Female reproductive system
Female
Female reproductive system
Male
Male reproductive system
Male
Male reproductive system
How does the uterus being muscular help?
Expands a lot during pregnancy
Funnel of oviduct
Catches egg/ovum
Oviducts/fallopian tube
Egg passes along here on its way to the uterus. Fertilization occurs here.
Vagina
Reception of penis/semen during sexual intercourse. For passage of baby during birth.
Cervix
Opening at base of uterus for passage of sperm.Baby emerges through uterus at birth
Female puberty?
Ovaries produce oestrogen
Ovaries
Produce eggs(ova)
Why do we need to produce so many sperm?
A lot are abnormal and cannot fertilize an egg , increase chances of sperm reaching an egg. Most die before they reach the oviduct.
Scrotum
Protection of testis
Urethra
Carries urine out of the body and semen out of the body( during sexual intercourse). Also valves stop both going down at the same time..
Prostate gland
Make liquid semen- nutrition for sperm
Seminal vesicles
Make liquid semen- nutrition for sperm
Epididymis
Storage and activation(make them swim)of sperm
What happens after mensuration?
Uterus lining repairs due to oestrogen made by ovaries and egg starts to mature inside a follicle in the ovary.
How many female sex hormones are there?
Two- oestrogen and progesterone
Adolescence
Time when a person approaches sexual maturity
When is the woman most likely to conceive?
After ovulation. Fertile period is time in the menstrual cycle a woman can become pregnant.
What happens if egg is fertilized/pregnancy occurs?
Progesterone continues to increase and the uterus thickens to receive embryo. Progesterone prevents mensuration, therefore, period stops during pregnancy and release of more eggs.
What happens if egg is not fertilized?
Level of progesterone decreases by day 28 and next period starts. Day 1 of a new menstrual cycle.
Progesterone
Hormone which continues maintaining the uterus wall(also slightly raises body temperature).
Corpus luteum
Once the follicle releases the egg, it collapses, becomes hard and yellow and is now corpus luteum.
Describe ovulation
Fluid pressure inside follicle causes it to burst and a mature egg is released. The release of an egg is called ovulation. The funnel of the oviduct pulls in the egg and the egg moves along the oviduct with the help of cilia by peristalsis.
Ovulation
Release of an egg
Testis function
Make sperm and testosterone
When does bleeding occur in a menstrual cycle?
When no egg has been fertilized and the inner lining of the uterus breaks down.
Sperm description?
Tail for swimming, middle piece containing mitochondria to release energy for swimming from respiration, acrosome- vesicle containing enzymes to dissolve a way through jelly surrounding egg cell.
Egg description?
Egg larger than sperm, egg contains large food store for development of a ball of cells following fertilization, before implantation.
Male and female gametes?
Egg/ovum and sperm
Male and female gonad?
Testes and ovaries
Female secondary sexual characteristics?
Menstrual cycle begins, public and armpit hair, hips widen and more fat stored in this area, mammary glands(breasts) develop, growth of uterus, ovaries start to release eggs(ovulation)
Male secondary sexual characteristics?
Growth of facial& public hair, hair on armpits and chest, voice deepens, body more muscular, production of sperm begins, growth of penis and testes