1. Sections 53.4-53.6

2. What He$# is Organogenesis? Organogenesis is the formation of organs in their proper location by interactions of cells within and between the three germ layers. Three Germ Layers * Endoderm, Ectoderm, and Mesoderm When does Organogenesis Begin??? It Follows right on the heels of gastrulation… Known fact in animals it begins before gastrulation is complete.. So what develops Again?? Tissues “Which are the Germ Layers” develop into organs and animal embryos assume their unique body form…

3. Blah…Blah...Blah More Info Cell-Signaling Molecules and Transcription help the genetic control of organogenesis in Vertebrates and Invertebrates. CELLS…CELLS…CELLS Cell Determination- a cell’s location in the developing embryo determines its fate.. Induction- a cells fate can be established by inheritance of cytoplasmic determinant from the mother and by interaction of cells… Nonporous Barrier- Prevents Induction Porous Filter- Permits Induction

4. Development and Stuff… In Vertebrates Organogenesis begins with Neurulation and Somitogenesis.. It also start the formation of two morphological features found only in Chordates……Notochord and Dorsal Nerve Cord…. Neurulation is the development of the dorsal nerve cord… Which forms the basic nervous system in vertebrates. Notochord is form from mesoderm and is a flexible rod located along the dorsal midline in the embryos of all chordates.. Somitogenesis is the process in which somites are form.. A somite is a division of the body of an animal. Neural crest cells arise from the neural tube and migrate to many sites to form a variety of cells types… Are important in the evolution of vertebrates..

5. Vertebrate Axis Formation The dorsal-ventral axis is determined by the Spemann organizer.. Organizers are a cluster of cells that produce gradients of diffusible signal molecules, conveying positional information to other cells.. Wnt genes encode a large family of cell –signaling proteins that affect the development of a number of structures in both vertebrates and invertebrates..

6. The Sperm Meets the Egg and a Human Develops!!!! “Random Fact” Human development from fertilization to birth takes an average of 266 days or about 9 months… This time is divided into three period called Trimesters.. First Trimester…Second…and Third

7. First Trimester Development in First Month The placenta is formed from the chorion and the endometrial tissues. The placenta provides nourishments for the embryo, detoxifies certain molecules that mass through and secretes hormones. Human Chorionic Gonadotropin (hCG) is a hormone released by the placenta. Gastrulation takes place in 2 nd week after fertilization and the three germ layers are formed. Organogenesis begins in fourth week.. The eyes form, tubular heart develops its 4 chambers, and will pulsate. “Another Random Fact” At 70 beats per minute, the heart is destined to beat more than 2.5 billion times during a lifetime of 70 years.

8. 1 st Trimester Continued….. The Second MonthThe Third Month Organogenesis continues…. The miniature limbs of the embryo assume their adult shapes. The arms, legs, knees, elbows, fingers, and toes can all be seen, as well as a short bone tail.. Major organs such as the liver, pancreas, and gallbladder become evident. The 9 th week the embryo becomes a fetus. All of the major organs in the body has been set in there proper locations … The Nervous System Develops…. Shows Facial Expressions and starts primitive reflexes… (hCG)declines and the corpus lutem regresses as a result. ** High levels of estadioal and progesterone in the blood during pregnancy continues to inhibit the release of FSH and LH, thereby preventing ovulation

9. First Trimester Photos Conception Blastocyst Gestational Sac Ultrasound 12 weeks

10. Second Trimester Bones Enlarge A rapid Heartbeat can be Heard. The fetus weighs about 1.3lbs is about 1 ft long. The fetus cannot survive outside the uterus without special medical interventions… Can tell if it a boy or girl??

11. Third Trimester Organs Mature to the Point at which the baby can survive outside the womb. The weight of the fetus doubles several times… Major Nerve Tracts in the brain is formed… Continues to develop and produce new neurons for months after birth..

12. Birth…… Birth is initiated by secretion of corticosteroids from the fetal adrenal cortex that induce prostaglandin, which cause contractions. Estadioal also stimulates the uterus to produce ore oxytocin receptors which it becomes sensitive to. Working together oxytocin and prostaglandin further stimulate uterine contractions, forcing the fetus downward labor. After birth, continuing uterine contractions expel the placenta and associated membranes, called afterbirth http://youtube.com/watch?v=GB3xu2krjuc&feature=related

13. Milk is Coming Out of My Br@#%!! This process is called lactation or milk production. It occurs in the alveoli of mammary glands when they are stimulated by the prolactin.. During pregnancy high levels of progesterone stimulates the development of alveoli and estadioal stimulate the development of the alveolar ducts. When the placenta is discharge after birth…progesterone and estadioal declines as prolactin is secrete and milk is made.. The pathway In which milk is released is called the milk-let down reflex. Colostrums is the first milk produced after birth…it hold nutritious and is rich in maternal antibodies.

14. Postnatal Development in Humans The growth of infants continue rapidly after birth.. Allometic Growth A pattern of growth in which different components grow at different rates.