Download Pregnancy Notes

Pregnancy Notes
Fertilization:
Takes place in the fallopian tube. Head of the sperm cell
penetrates the egg cell. The forms a single cell, the zygote. (23
pairs of chromosomes, 46 total in humans)
Following fertilization, the embryo implants itself into the lining
of the uterus. The embryo will develop its own support system,
the placenta.
Oocyte (egg):
Viable for 12-24 hours after it is cast out of the ovary. Sperm
are viable within the female reproductive tract for 12-72 hours
after ejaculation.
Pregnancy:
The period from conception to the birth of the baby.
Pregnancy Tests: The hCG human chorionic gonadotropin
hormone which provokes the ovary to continue producing
hormones, this is what is detected in the urine of pregnancy
tests.
 First 8 weeks of pregnancy are known as the embryo stage,
the embryo is no larger than your thumb!
1)Zygote:
A fertilized egg. The cells dividing in the zygote is known as
cleavage.
2) Morula:
After 3-4 days following fertilization this blackberry cluster of
cells leaves the fallopian tube and enters the uterus.
3) Blastocyst:
6 days after fertilization, forms a hollow cavity. Lands on the
endometrium (lining of the uterus) and implants itself. Fertilized
cell develops into an enlarging cluster of cells known as the
blastocyst.
4) Embryonic Disk:
With in the cell mass, a disk forms and also forms an amniotic
cavity which develops into a sac filled with fluid. Disk develops
into three germ layers, ectoderm, mesoderm, endoderm, all body
structures will form from these layers.
 Endoderm: digestive, respiratory, and glands…
 Ectoderm: epidermis, skin, hair nails, tooth enamel, eyes
 Mesoderm: bone, muscle, heart
*Usually development is head down: brain and head then body,
followed by arms and lastly the legs. 8 weeks after fertilization,
all major organs and body parts are formed. The baby is now
known as a fetus.
DEVELOPMENTS:
 3 weeks: neural tube forms, and becomes the spinal cord.
The heart pulsates. 2-3mm long
 4 weeks:
4 chambered heart, organs can be seen. 4-5mm long
 8 weeks:
The face and neck take shape. Fingers and toes form, embryo
can move. 25-30mm
Fetus:
From the eighth week of pregnancy the baby is known as a fetus.
Most major development has taken place during the embryo
stage.
12 weeks: fetus has a large head compared to the rest of the
body. Features are distinctly human. All major organs are
developed. External genetalia are visible, and hair (lanugo) grows.
Eyes remain closed until about the 7th month.
24 weeks: movement can be felt by the mother.
36 weeks: Fetus is restricted by the uterus.
Placenta:
The embryo develops an organ called the placenta, which produces
hormones crucial to the continuation of pregnancy. The main
function of the placenta is to supply the fetus with oxygen and
nutrients and rid waste products via diffusion. Acts as a barrier
against harmful substances that may enter the body of the fetus.
The placenta also becomes an endocrine organ and secretes
hormones that help maintain pregnancy.
Umbilical Cord:
Structure that connects the placenta and the fetus. Link to the
mother.
Amniotic Fluid: shock absorbing liquid in which the fetus floats.
Changes in the mother:
pregnancy lasts 38-40 weeks. Each trimester is 3 months.
1st trimester: breasts become tender and larger. Frequency of
urination, nausea and vomiting are common.
2nd trimester: enlarging uterus, showing,compresses intestines
heart rate increases, skin may darken (mask of pregnancy)
3rd trimester: skin stretches, fatigue, back pain, heartburn.
Uterus: usually the size of a fist. During pregnancy can reach all
the way up to the tip of the sternum!
 Pregnant women need about 300 additional calories a day to
sustain proper fetal growth!
Morning sickness: Due to elevated levels of hormones
(progesterone and estrogen) women’s bodies react with nausea.
Heartburn: esophagus is displaced, constipation because digestive
motility decreases to make room for baby.
Urinary System: The kidneys have to function more because they
are also filtering the wastes of the baby. Produce more urine and
uterus compresses the bladder.
Preparing for birth:
Twins or multiple births: twins = 1/80 pregnancies, triplets
1/8000.
monozygotic twins: one egg forms an embryo that splits in two.
Identical, same genes, same sex. Share one placenta.
Dizygotic twins: two eggs are fertilized separately each with its
own placenta, may be different or the same sex. Fraternal twins.
Most common fetal position is head down facing the mothers
back! However, 1/30 babies are breech, where legs or buttocks
emerge first before the head. Frank breech: incomplete breech,
legs extended. Complete breech: feet beside buttocks.
Cervix: Lower end of the uterus, top of the vaginal canal.
Childbirth:
AKA parturition is the end of pregnancy. Usually occurs 15 days
of the due date. The series of events that expel the infant from
the uterus is known as labor.
Why do women go into labor?
Release of the hormones called prostaglandins and oxytocin. Both
hormones stimulate the rhythmic, expulsive contractions.
Stages of Labor:
1) Dilation stage: time from the appearance of true
contractions until the cervix is fully dilated by the baby’s
head, about 10cm. The amnion ruptures, releasing amniotic
fluid (water breaking). Longest part of labor and usually
lasts from 6-12 hours.
2) Expulsion Stage: full dilation until delivery of the infant.
The infant passes through the cervix and the vagina to the
outside of the body. 20-50 minutes.
Dystocia: birthing difficulty a C-section may be preformed.
A cesarean section is delivery of an infant through surgery.
3) Placental Stage: delivery of the placenta. 15 minutes after
birth of the infant. (afterbirth)