What is amniocentesis? The liquid (amniotic fluid) around the unborn baby (fetus) in the womb contains skin cells shed by the fetus and waste products from the fetus. The fetal skin cells in the amniotic fluid - like every cell in our bodies - carry genetic information (DNA: in the form of chromosomes and mitochondrial DNA1.) A small amount of amniotic fluid (about 2 tablespoons; 20mls or so) is removed through a hollow needle inserted into the pregnant woman ’s uterus (womb), through her abdomen. Any fetal material in the fluid can then be tested - for example to determine whether the fetus has a genetic abnormality. What conditions can amniocentesis detect or exclude? In addition to determining the sex of the fetus, analysis of genetic material from fetal cells in the amniotic fluid can detect (or exclude) numerous genetic abnormalities or diseases such as Down syndrome, Fragile X, cystic fibrosis (CF), myotonic dystrophy (DM), mitochondrial disorders, Turner syndrome, Tay-Sachs disease, Huntington ’s Disease (HD), Sickle Cell Disease (SCD) or Sickle Cell Anaemia (SCA) and Beta-Thalassaemia (β-thal). The number of fetal cells in the amniotic fluid will probably not be enough for immediate genetic testing; so more fetal cells have to be cultured (grown) from the sample to provide enough material for genetic analysis. This can take several weeks. Chemicals in the fluid can also be tested for neural tube defects (abnormalities in the formation of the brain and spinal cord - such as spina bifida and anencephaly - now usually detected by blood screening test and non-invasive ultrasound) and for conditions that affect a child ’s metabolism. Amniocentesis cannot detect conditions such as cleft lip and palate, limb abnormalities, extra fingers and toes, heart defects or hernia: non-invasive ultrasound may be able to do so. When is amniocentesis carried out? Amniocentesis is usually conducted in the middle trimester (three months) of pregnancy - from about 15-20 weeks ’ gestation. Occasionally it is carried out later.
Top 3 pics: sperm enters egg Duplication of cells (Immediately the cell begins to duplicate, taking approximately 30 hours to complete the first cell division.) Formation of embryo (At an increasingly faster rate, new cells are added until they form a hollow, fluid-filled ball, called a blastocyst (about 4 or five days after conception). Approximately 60 to 70 cells form the blastocyst. Those on the inside (called the embryonic disk) will become the new organism whereas those on the outside will provide the protective covering.) Implantation (Around the seventh or ninth day, the blaystocyst implants itself into the uterine lining. The protective covering quickly develops into the amnion, surrounding the organism in amniotic fluid . A yolk sac also develops, producing blood cells until the liver, spleen, and bone marrow is mature.)
5 wk old embryo (The Period of the Embryo lasts from about 2 weeks until about the eighth week of pregnancy. During this time, the groundwork for all body structures and organs is laid.) 6 wk old embryo (Even before the mother knows she is pregnant, the heart has begun to pump bood, the muscles, backbone, and ribs have begun to appear, and tiny buds have developed into arms, legs, fingers, and toes.) 7 wk old embryo (By the seventh week, the liver and spleen begins producing blood cells and the heart has developed separate chambers. At this time, the tiny organism shows sensitivity to touch and freely moves about in the amniotic sac. However, at less than an inch long and only an ounce in weight, the organism is still too tiny for any movements to be felt by the mother.)
A 10mm embryo from an ectopic pregnancy, still in the oviduct. This embryo is about five weeks old (or from the 7th week of pregnancy).
6 week old human embryo
CHECKPOINT 1 TB Pg 89
Lower Secondary - Sexual Reproduction
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ASEXUALREPRODUCTION The new organism hasthe same geneticmaterial as the parent. Only one parentrequired. Cell simply divides intotwo. Method used by mostunicellular organisms. The new organism doesnot have the samegenetic material as theparent. A male & a femalerequired. Involves a male & afemale gamete (sex cells). Method used by mostmulticellular organisms.SEXUALREPRODUCTION
ADVANTAGES OF ASEXUALREPRODUCTION Quick – no need to find a mate Because the genetic material of thenew organism is the same as that ofthe parent, thus the new organism hasthe desirable qualities of its parent.
ADVANTAGES OF SEXUALREPRODUCTION Genetic material of the new offspringis a combination of the geneticmaterial from the parents thus thenew offspring may have good traitse.g. better looking than the parents. A variety of new organisms areproduced.
SEX CELLS (gametes) Male sex cell = sperm(plural sperms) Female sex cell = ovum (egg)(plural ova) Sex cells are made in the reproductivesystem of a man and a woman.
NO. OF CHROMOSOMES No. of chromosomes in a normalhuman cell (excluding sex cell)= 46 (23 pairs)
23NO. OF CHROMOSOMES IN A NORMALHUMAN CELL (EXCEPT SEX CELL) = 46
PARTS OF THE MALEREPRODUCTIVE SYSTEM TESTIS (plural TESTES)- Produce sperms & male sex hormones. SCROTUM- A bag of skin which holds the testesoutside the body.- Testes are outside the body thus lowertemperature for production & storageof sperm.
PARTS OF THE MALEREPRODUCTIVE SYSTEM SEX GLANDS- Produce fluids in which the sperms‘swim’.- Semen = mixture of sperms and fluids
PARTS OF THE MALEREPRODUCTIVE SYSTEM SPERM DUCT- A tube that carries the sperms to thepenis. PENIS- The organ from which semen leavesthe body and is deposited in thevagina of the female.
PARTS OF THE MALEREPRODUCTIVE SYSTEM URETHRA- A tube which carries sperms & urine atdifferent times. URETER- A tube that links the kidney to theurinary bladder.
PARTS OF THE FEMALEREPRODUCTIVE SYSTEM OVARY- Produces eggs & sex hormones.- A young girl’s ovary contains about 70 000ova (eggs). About 500 will become mature.- An ovum (egg) is released from the ovaryevery 28 days.- The ovaries take turns to release an ovum.
A hamster egg entering the funnel of the oviduct
PARTS OF THE FEMALEREPRODUCTIVE SYSTEM OVIDUCT- Also called fallopian tube.- Connects the ovary to the uterus.- Funnel of oviduct collects the ovum.- Fertilisation takes place in the oviduct. UTERUS- Also called womb.- Where the baby grows during pregnancy.
PARTS OF THE FEMALEREPRODUCTIVE SYSTEM CERVIX- The narrow opening of the uterus.- Becomes wider during the birth of the baby. VAGINA- Also called birth canal.- A muscular tube where sperms from thepenis are deposited.- Becomes wider during the birth of the baby.
REVISIONLabel the parts in the male &female reproductive system.
FERTILIZATION The sperm and egg each have 23chromosomes. The zygote formed will have 46chromosomes. Then the zygote divides by normal celldivision.
AFTER FERTILIZATION As the zygote divides by normal celldivision, it moves along the oviducttowards the uterus with the help of: cilia sweeping the fertilised egg(zygote) along the oviduct. peristaltic movements in theoviduct.
AFTER FERTILIZATION When it reaches the uterus, it is a ball-like structure consisting of many cells –an embryo.
DEVELOPMENT OF THE EMBRYO It takes about 5 days for the embryoto reach the uterus. Implantation: Eventually the embryosinks or becomes embedded in theuterine lining (wall of the uterus).
THE AMNION• The amnion (a membrane) enclosesthe embryo in the amniotic cavity,which is filled with amniotic fluid.
FUNCTIONS OFTHE AMNIOTIC FLUID1) A shock absorber - protects thefoetus against mechanical injurybecause it is incompressible.2) Allows the foetus to move freelyduring growth.3) Lubricates and reduces friction in thevagina (birth canal) during birth.
WHAT IS AMNIOCENTESIS? A hollow needle inserted into theuterus through the abdomen. Remove a small amount of amnioticfluid (about 2 tbsps, 20 ml). Carried out during the middletrimester (3rdto 6thmonth).
WHY AMNIOCENTESIS?The amniotic fluid around the foetuscontains skin cells shed by the foetus.These skin cells contain DNA.From this genetic material, we candetermine: Genetic diseases e.g. Down Syndrome (Gender of the foetus)
FUNCTIONS OF THE PLACENTA1) Allow food, oxygen & water to passfrom the mother’s blood to the fetus.2) Allow waste substances produced bythe fetus to pass back into themother’s blood for removal.3) Prevents some harmful substances inthe mother’s blood from reaching thefetus.
THE UMBILICAL CORD The umbilical cord attaches the foetusto the placenta. The umbilical cord contains the bloodvessels of the foetus, namely: 2 umbilical arteries 1 umbilical vein