Presentation on theme: "Developed b y D. Ann Currie. Ovary gives rise to oogonial cells. Cells develop into oocytes. Meiosis begins and stops before birth. Cell division."— Presentation transcript:
Ovary gives rise to oogonial cells. Cells develop into oocytes. Meiosis begins and stops before birth. Cell division resumes at puberty. Development of Graafian follicle.
The female gamete are called Ovum. The ovum are considered fertile for about 12-24 hours after ovulation.
Production of sperm First meiotic division: ◦ Primary spermatocyte replicates and divides. Second meiotic division: ◦ Secondary spermatocytes replicate and divide. Produce four spermatids.
The male gamete are Sperm. The sperm can survive in the female reproductive tract for 48-72 hours. However they are believed to be healthy and highly fertile for only 24 hours. In a single ejaculation the male deposits approximately 200-500 million sperm in the vagina. Only hundreds of sperm actually reach the ampulla. Only one sperm fertilizes the ovum.
Zone pellucida blocks additional sperm from entering Secondary oocyte completes second meiotic division ◦ Forms nucleus of ovum Nuclei of ovum and sperm unite Membranes disappear Chromosomes pair up
Zygote moves through the fallopian tube towards the cavity of the uterus. Transportation takes 3 or more days. Rapid mitotic divisions called cleavage is occurring. 7-10days after fertilization the blastocyst implants. Most frequent site of attachment is the upper part of the posterior uterine wall.
About 10-14 days after conception Primary germ layers: Ectoderm Mesoderm Endoderm
Chorionic villi form spaces in decidua basalis Spaces fill with maternal blood. Chorionic villi differentiate: Syncytium: outer layer Cytotrophoblast: inner layer Anchoring villi form septa
Nutrition Excretion Fetal respiration Production of fetal nutrients Production of hormones Large molecular compounds can not crossthe placenta Other see text
Body stalk fuses with embryonic portion of the placenta Provides circulatory pathway from chorionic villa to the embryo Delivers oxygenated blood to the fetus: One Vein Returns waste material to maternal circulation: Two Arteries
Amnion: Encloses the amniotic cavity The inner membrane that forms about the 2 nd week of embryonic development Forms a fluid-filled sac that surrounds the embryo and later the fetus. Chorion: Is the outer membrane Becomes vascularized and forms the fetal portion of the placenta.
Consists of 800-1200 ml by the end the pregnancy Surrounds, cushions, protects, the fetus and allows for fetal movement. Maintains body temperature of the fetus. Contains fetal urine and is a measurement of fetal kidney function. The fetus modifies the amniotic fluid through the processes of swallowing, urinating, and movement trough respiratory tract. Other see text.
First 2 week after conception Cleavage Blastomeres form morula Blastocyst: - develops into embryonic disc and amnion Trophoblast: - develops into chorion
Beginning at Day 15 through approximately the 8 th week after conception.