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Lecture Biology 25 (Human Biology): Chapter 18 - Prof. Gonsalves

Chapter 18 provides knowledge of development & aging. The main contents of the chapter consist of the following: Fertilization, development before birth, development of male and female sex organs, birth, development after birth. | Chapter 18 Biology 25: Human Biology Prof. Gonsalves Los Angeles City College Based on Mader’s Human Biology,7th edition and Fox’s 8th ed Powerpoints Fertilization Ejaculation 300 million sperm, 100 reach (uterine) fallopian tube. Fertilization occurs in the uterine tubes Acrosomal reaction: Acrosome of sperm contains hyaluronidase, an enzyme that digests a channel through zona pellucida. Sperm fuses with ovum cell membrane. Fertilization As fertilization occurs, secondary oocyte completes 2nd meiotic division. Sperm enters ovum cytoplasm. Ovum nuclear membrane disappears, zygote formed. Blastocyct Formation Cleavage: 30-36 hrs. after fertilization the zygote divides by mitosis. Blastocyst develops: Inner cell mass: fetus. Surrounding chorion: trophoblasts form placenta. Implantation 6th day after fertilization, blastocyst attaches to uterine wall. Blastocyst secretes enzymes that allow blastocyst to burrow into endometrium. Trophoblast cells secrete hCG. Amnion Envelop the embryo. Amnionic fluid contains sloughed cells of the fetus. hCG Human chorionic gonadotropin. Trophoblast cells secrete hCG. Signals corpus luteum not to degenerate until placenta secretes adequate [hormone]. Effects similar to LH. Basis of pregnancy test. Placenta Syncytiotrophoblast secretes enzymes that create blood filled cavities in the maternal tissue. Cytotrophoblast then from projections (villi) that grow into the venous blood. Producing chorion frondosum on the side that faces the uterine wall. Other side of chorion bulges into the uterine cavity. Placental Changes Decidual reaction: Endometrial growth. Accumulation of glycogen. Decidua basalis: maternal tissue in contact with the chorion frondosum. Maternal and fetal blood do not mix. Placenta Function Gas exchange: 02 and C02. Nutrient exchange. Waste exchange. Synthesis of proteins and enzymes. Placental Hormones hCS: Chorionic somatomammotropin. GH effects. Diabetic-like effect: Glucose sparing effect. Polyuria. Lipolysis. . | Chapter 18 Biology 25: Human Biology Prof. Gonsalves Los Angeles City College Based on Mader’s Human Biology,7th edition and Fox’s 8th ed Powerpoints Fertilization Ejaculation 300 million sperm, 100 reach (uterine) fallopian tube. Fertilization occurs in the uterine tubes Acrosomal reaction: Acrosome of sperm contains hyaluronidase, an enzyme that digests a channel through zona pellucida. Sperm fuses with ovum cell membrane. Fertilization As fertilization occurs, secondary oocyte completes 2nd meiotic division. Sperm enters ovum cytoplasm. Ovum nuclear membrane disappears, zygote formed. Blastocyct Formation Cleavage: 30-36 hrs. after fertilization the zygote divides by mitosis. Blastocyst develops: Inner cell mass: fetus. Surrounding chorion: trophoblasts form placenta. Implantation 6th day after fertilization, blastocyst attaches to uterine wall. Blastocyst secretes enzymes that allow blastocyst to burrow into endometrium. Trophoblast cells secrete hCG. Amnion Envelop the embryo. .