Medical brain Notes 3

  Conception   Other terms used to describe this phenomenon are fertilization, impregnation or fecundation.   Definition -Fertilization is the union of the ovum and a sepermatozoa.   Fertilization must occur fairly quickly after release of the ovum because it usually occurs in the outer third of a fallopian tube, the ampullar portion. The functional life span of aspermatozoa is about 48 hours / may be as long as 72 hours or longer. Therefore, sexual coitus during this time may result in fertilization /pregnancy.

  Development of the Fertilized Ovum   After fertilization the ova passes through the fallopian tube and reaches the uterus 3 or 4 days later. Division takes place and the fertilized ovum divides into two cells, and then into four, then eight, and sixteen and soon until a cluster of cells is formed known as the morula.   These divisions occur quite slowly about once every 12 hours. Next, fluid filled the cavity or blastocele appears in the morula which now becomes known as the blastocyst.   Around the out side of the blastocyst there is a single layer of cell known as the trophoblast while the remaining cells are clumped together at one end forming the inner cell mass. The trophoblast will form the placenta and chorion, while the inner cell becomes the fetus, umbilical cord and the amnion. Embedding of the blastocyst is normally completed by the 11 th  day after ovulation and the endometrium closes over it completely.   The Decidua   This is the name g...

  Functions of Placenta   Respiration -  As pulmonary exchange of gases does not takeplace in the uterus the fetus must obtain oxygen and excrete carbon dioxide through the placenta     Nutrition -  Food for the fetus derives from the mother’s dietand has already been broken down into forms by the time reachs the placenta site. The placenta is able to select those substances required by the fetus, even depleting the mother’s own supply in some instances.   Storage -  The placent metabolises glucose and can alsostores it in the form of glycogen and reconverts it to glucose as required. The placenta store iron and the fat soluble vitamins.   Excretion - The main substance excerted from the fetus iscarbondioxide; bilrubin will also be excreted as red blood cells are released relatively frequently.   Protection -  It provides a limited barrier to infection with theexception of the treponeona of syphilis and, few bacteria can penetrate. ...

  The Fetal Circulation   At the birth there is a dramatic alteration in this situation and almost instaneous change must occur. Besides this all, the postnatal structures must be in place and ready to take over. There are several temporary structures inaddition to the placenta itself and the umblical cord and these enable the fetal circulation to take place while allowing for the changes at birth.   The Umbilical vein  Leads from the umblical cord to theunderside of the liver and carries blood rich in oxygen and nutrients. It has a branch which joins the portal vein and supplies the liver.   The ductus vensous  (from a vein to a vein) connects theumblica vein to the inferior venacava. At this point the blood mixes with deoxygenated blood returning from the lower parts of the body. Thus the blood throughout the body is at best partially oxygenated.   The foramen ovale  (oval opening) is a temporary openingbetween the atria which allows the majorit...

  Succenturiate lobe of placneta:   A small extra lobe is present, separate from the main placenta and joined to it by blood vessles which ran through the memebrane to reach it.   The danger  is that this small lobe may be retained in utroafter delivery, and if it is not removed it may lead to haemorrhage and infection.   Identification  On inspection, the placenta will appear torn atthe edge, or torn blood vessles may extend beyond the edge of the placenta.   Circumvallate placenta  In this situation an opaque ring isseen on the fetal surface. It is formed by a doubling back of the chorion and amnion.   Danger  may result in the memberanes leaving the placentanearer the center instead of at the adge as usually.   Battledore inseration of the cord  The cord in this case isattached at the very edge of the placenta in the manner of the table tennis bat.   Danger  Likely it is detached up on applying traction duringactiv...

  Physiological Changes of Pregnancy   ·                There are physiological biochemical and anatomical changes that occur during pregnancy. These changes may be systemic or local.   ·                Most of the systemic changes return to pre pregnancy status 6 weeks after delivery.   ·                These changes occur during pregnancy to maintain a healthy environment for the fetus with out compromising the mother’s health. And prepare for the process of delivery and care of the newborn.   ·                Understanding of the normal changes helps to understand coincidental disease processes.   1. Gastro Intestinal Tract (GIT)     ·      ...