兽医产科学4.ppt

* * * * * * * * Figure: 37-12 Title: The placenta Caption: The placenta is formed from both the chorion of the embryo and the endometrium of the mother. Capillaries of the endometrium break down, releasing blood that forms pools within the placenta. Chorionic villi containing embryonic capillaries extend into these pools of maternal blood. The placenta allows diffusion of oxygen, carbon dioxide, nutrients, and wastes between the fetal capillaries and the maternal blood pools, while keeping the fetal and maternal blood supply separate. Umbilical arteries carry deoxygenated blood from the fetus to the placenta, and umbilical veins carry oxygenated blood back to the fetus. Question Some mammals lack a placenta. What would you predict about the nature of development in nonplacental mammals? * * * * * * * * Figure: 37-3 part c Title: A blastula becomes a gastrula part c Mesoderm differentiates. * * Table: 37-T2Title:Derivation of Adult Tissues from Embryonic Cell Layers * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Clinical Methods Transrectal Palpation Palpation of the amniotic vesicle Palpation of the allantochorion(membrane slip) Unilateral horn enlargement Palpation of the early fetus Palpation of placentomes Palpation of the cervix Hypertrophy of the middle uterine artery and development of fremitus震颤 Palpation of the late fetus Accuracy of pregnancy diagnosis by palpation Induced prenatal death due to rectal palpation Vaginal Examination Ultrasonographic Methods * 2011 * * * 2011 Optimum Time for Diagnosing Pregnancy The aim of pregnancy tests is to identify, as early and as accurately as possible, the absence of pregnancy so that steps can be taken to ensure that the cow is served again and thus ensure an optimum calving pattern. However, it is important that inexperienced veterinarians should select a time when they are confident of their accuracy in making the diagnosis, irrespecti