Presentation on theme: "Fetal Development. Create a timeline outlining the stages of human development Label a diagram of the stages of human development KEY WORDS ImplantationEmbryoTrimester."— Presentation transcript:
Create a timeline outlining the stages of human development Label a diagram of the stages of human development KEY WORDS ImplantationEmbryoTrimester Fetus
Haploid gametes contain 23 total chromosomes – 22 regular chromosomes and 1 sex chromosome. Two types of sex chromosomes- called X and Y Sperm can have either one X OR one Y. Eggs always have one X chromosome. Every male body cell has one X and one Y. Every female body cell has two X.
Egg and sperm meet in the oviduct - fertilization. Sex is determined by the male at fertilization. Nuclei are joined to produce a single diploid cell called a zygote. 2 stages of development - fertilization to birth: 1.Embryo stage: first eight weeks. 2.Fetus stage: from eight weeks to birth.
1.Embryo Stage Zygote implants in endometrial lining and begins to grow (divide) by mitosis for first eight weeks. Once implanted – called an embryo. Cleavage: mitotic divisions begin, changing zygote to a multicellular embryo.
2. Fetus Stage Developing embryo forms bone cells around the ninth week of pregnancy. Once bone forms - called a fetus until born. Placenta - exchanges waste and nutrients through umbilical cord. Amnion – protective sac filled with fluid.
Pregnancy can also be divided in 3 trimesters: 1 st trimester – conception to 3 rd month development of all body systems and organs. sex can be determined embryo movements not perceptible to the woman. she may not know that she is pregnant At end - fetus weighs 28 grams, 7.5 mm long. fetus is particularly sensitive to alcohol, smoking and other drugs.
1 st trimester
2 nd trimester – 4 th to 6 th months period of rapid and continuous growth. Only brain and lungs still developing. embryo movements can be felt. At end - fetus weighs 650 grams, 30 cm long. If born prematurely: Might survive with great medical assistance. Most do not survive.
2 nd trimester
3 rd trimester – 7 th to 9 th (birth) month fetus kicks, stretches and moves freely. Eyes sense light, fingerprints have formed. At end – fetus weighs 3300 grams, 35 cm long. Dangers include complications during delivery and lifestyle choices.
3 rd trimester
And then, before you know it...
Zygote at fertilization. Embryo at implantation to endometrium. Fetus after bone development. Baby at birth. Fertilization to birth can be separated into 2 stages – embryo and fetus. Pregnancy can be separated into 3 trimester.
Homologous chromosomes are similar but NOT identical. Homologous means that the chromosomes contain the same types of genes. Gene - piece of DNA with instructions for a specific trait – hair colour, height, eye colour…
A diploid cell will contain two variations of each gene. 1 – mom 1 – dad