PREGNANCY 1st and 2nd Trimesters

PREGNANCY 1st and 2nd Trimesters
Presentation lecture from: Orangecoastcollege

* General
o Sonography used after 4-5 weeks
o Events prior to this time:
1. Ovulation
2. Fertilization
3. Implantation
4. Placentation
5. Embryonic Development

OVULATION
A. Definition: a cyclic event controlled by two hormones (FSH and LH) that occurs monthly

1. ~ 20 ova begin maturing
2. Only one completes the maturation process
Phase??
3. After ovulation, ovum moves into uterine tube
4. If fertilized, the zygote begins to divide
5. Implantation begins in ~6 days

FERTILIZATION
A. Definition: penetration of the ovum by one spermatozooan

1. Hyaluronidase (from acrosome):enzyme that allows penetration
2. Lack of acrosome/enzyme: infertility
3. Polyspermy: More than one sperm penetrates ovum

B. Sperm and ovum are haploid (N)
C. Genetic material in nuclei fuses to form zygote (2N)
D. Zygote begins cell division (mitosis!) immediately
E. Differentiation: prior to reaching uterus, zygote has developed into morula
+ Cells continue to divide, form blastula or blastocyst
# trophoblast
# inner cell mass or blastoderm
G. Trophoblast will give rise to placenta
H. Inner cell mass will give rise to the embryo
1. Ectoderm (outer layer or “outer skin”)
2. Endoderm (inner layer or “inner skin”)
3. Mesoderm (middle layer or “middle skin”)


Primary Germ Layers

Implantation
The Uterus
Perimetrium
Myometrium
Endometrium
Placenta & Fetal Membranes
Placental formation
Chorion Frondosum
Formation of Umbilical Vessels
Fetal membranes
Umbilical Cord
Anomalies
Meckel’s Diverticulum
May indicate fetal demise, premature rupture of membranes
Omphalocele
Ectopic Pregnancy
Metastatic Carcinomas
Spread via lymph circulation
Rectouterine Pouch (of Douglas) or cul-de-sac
Hydrocephaly
Hydrocephalus
Anencephaly:
Porencephaly
Doppler U/S of the Circle of Willis in utero
Circle of Willis
Fetal circle of Willis: 3D U/S
Ultrasound-guided Prenatal Diagnosis
Amniocentesis and CVS
Pelvic masses
Uterine Anomalies
Uterus bicornis
Uterus didelphys
Uterus unicornis

PREGNANCY 1st and 2nd Trimesters.ppt