FIRST TRIMESTER BY: Heather, Maria, & Ibelise

STAGE ONE : one day post ovulation Fertilization begins when a sperm penetrates an oocyte (an egg) and it ends with the creation of the zygote. The fertilization process takes about 24 hours. Within 11 hours following fertilization, the oocyte has extruded a polar body with its excess chromosomes. The fusion of the oocyte and sperm nuclei marks the creation of the zygote and the end of fertilization. It takes only one sperm to fertilize the egg Penetration of the zona pellucida takes about twenty minutes

STAGE TWO : days post ovulation The cells divide into two smaller sets called blastomeres Each cell division occurs every twenty hours becoming smaller with every division When cell division generates about sixteen cells, the zygote becomes a morula. It leaves the fallopian tube and enters the uterus three to four days after fertilization The blasocele then forms in the morula and creates the blastocyte, which forms two more cells

STAGE days post ovulation The uterus is therefore swollen with new blood capillaries and the circulation between mother and blastocyst begins, a process needed for the continuation of pregnancy Trophoblast cells destroy cells of the uterus and make blood pools that eventually form the placenta. The blastocyst forms into two layers 1)The epiblast – the embryo and the ambiotic fluid 2)The hypoblast- the yolk sac

STAGE days post ovulation Villi forms & embryo attaches to the uterus Fetus is attached by an umbilical cord Gastrulation occurs & embryonic disc forms The layers of the embryonic disc are the ectoderm the mesoderm and the endoderm Eventually the ectoderm changes from two layers to three layers The egg is now shaped like a pear Blood cells are already developed Endocardial cells fuse to form embryo’s two heart tubes

DEVELOPMENT

STAGE days post ovulation Neural crests contribute to the skull and face formation Heart tube takes on a s shape and cardiac muscle contraction begins Fluids begin to get pumped through the body Central nervous system is most developed Embryo curves into a C shape and arches that are the neck and face show under the forebrain Brain and Spinal cord are largest most compact tissue of embryo Blood system continues to develop Somite form sclerotome which becomes cartilage Back muscle is formed along with the ribs The digestive epithelium layer begins to differentiate into the future locations of the liver, lung, stomach and pancreas

Weeks 4 -10

STAGES days post ovulation Brain and head grow rapidly and the mandibular and hyoid arches are noticeable Spinal cord wall contains three zones : ventricular the mantle and the marginal. The adenohypophyseal pouch develops into the anterior pituitary Brain has increased in size Thorax appears more and the esophagus lengthens Brain has cerebral hemispheres and the hind brain is responsible for heart regulation breathing and muscle movements Retina pigment is visible and lens pit has grown into a d shape.

Medical Tests

STAGE 17 – days post ovulation Jaw and facial muscle are now developing & teeth beds begin to form. Nasofrontal groove becomes distinct and sense of smell forms in brain Heart separate into 4 chambers and nipples form Eye pigments develop and scalp gets nerves Kidney produces urine, body is cubed shaped & ossification of skeleton begins Head is more erect inner ear forms the canals Gonads and limbs form Toenails bone cartilage and muscle forms Brain is connected to tiny muscles and nerves Testes & ovaries are distinguishable Upper limps are longer and toes are formed.

STAGE days post ovulation Eyes are still on the side of the embryos head Fingers lengthen and features are still in a web shape The have and head become more humanly shaped Heart development slows down the clitoris and penis begin to form Taste buds form & primary teeth are at cap stage Intestine begin to migrate to the body Limbs are well formed Tail is gone and surface layer skin appears

DISORDERS : ectopic pregnancy

ECTOPIC PREGNANCY

If a fertilized egg implants outside the uterus, it's called an ectopic pregnancy. One in 50 pregnancies ends this way. Here's how it happens: After conception, the fertilized egg travels down your fallopian tube on its way to your uterus. If the tube is damaged or blocked and fails to move the egg toward your womb, the egg may become implanted in the tube and continue to develop there. Because almost all ectopic pregnancies occur in one of the fallopian tubes, they're often called "tubal" pregnancies The only way to handle this is to abort the pregnancy Failure to get the pregnancy aborted can result in fallopian tubes bursting which causes internal bleeding and could eventually lead to death