Embryonic Development

Morula, blastocyst, gastrula

stages of embryonic dev’t

morula

• solid mass of cells resulting from cleavage

• formed 3 days after fertilization

• consists of 20-30 cells, max: 60 cells

blastocyst

• ball of cells formed from morula

• 5-14 days after fertilization

embryonic disk

inner mass of cells of blastocyst

gastrula

embryo composed of 3 tissues: ectoderm, mesoderm, endoderm

ectoderm, mesoderm, endoderm

foundation of the body systems (germ layer theory)

cleavage, morphogenesis, differentiation, growth

Process of dev’t

ectoderm (outer layer)

• responsible for dev’t of epidermis (hair, nails, sweat glands) and nervous system dev’t

mesoderm (middle layer)

dev’t pf dermis, muscles, connective tissues, bones, cartilage, blood vessels, kidneys, and reproductive organs

endoderm (inner layer)

dev’t of pancreas, lining of digestive tract, lungs, gallbladder, urethra, thyroid and parathyroid glands, urinary bladder, thymus glands

cleavage

cell division without growth

morphogenesis

• shaping of embryo

• 8-10 weeks AOG

differentiation

• cells takes on specific structures and functions

• guided by fetal pituitary

• as early as 9 weeks; 8-16 weeks AOG

growth

• increase in size in cells

• 5 weeks AOG

neurula

• nervous system develops from ectoderm located just above the notochord

• marks the beginning of organogenesis

germ layer theory

all embryos are composed of distinct layers which gives particular tissues in the dev’t of fetus

gastrulation

• cell dev’t or movement

• enlargement or folding of cells

oogenesis

dev’t of an ovum

organogenesis

• organ dev’t

• 8-10 weeks AOG

notochord

• vertebral dev’t

• cues of the fetus

chorion, amnion, yolk sac, allantois,

extra-embryonic membranes

chorion

membrane that surrounds the embryo; protection and nurtures the fetus

chorionic fluid

allows exchange of fetal and maternal blood gases

amnion

provides full fluid environment; developed during early gastrulation

yolk sac

• site for RBC formation

• absorbs nutrients deposited in the yolk

• 2 weeks AOG

• responsible for nutrients and oxygen for the first 12 weeks of pregnancy

allantois

• embryonic respiratory system

• receives excretion of the embryonic kidneys (urine of fetus)

• absorbs albumin

albumin

protein necessary for the development of embryo (3rd week - 5th-7th week AOG)

fetal ciculation

occurs during pre-natal

umbilical cord

• supplier of oxygen and nutrients

• responsible for circulation in the fetus

AVA

2 arteries, 1 vein in fetal umbilicus

placenta

• formed during 4th week; full dev’t around 14-20 weeks

• take over oxygen production from the corpus luteum (8-12 weeks)

• supplies most of the oxygen

luteal-placental shift

process in which the placenta take over oxygen production from the corpus luteum (8-12 weeks)

umbilical cord and placenta

fetus obtains nutrients and oxygen from the mother

ductus arteriosus

short vessel; connects the fetal pulmonary artery to the aorta

hemoglobin

core concept of fetal circulation

fetal hemoglobin

has increased compatibility for oxygen

180 ml/meter/kilogram of estimated fetal weight; 25%

aorta will only allow the umbilical cord flow for about…; only takes ___ of the blood that enters the liver circulation

liver, ductus venosus

2 branches that leads to the inferior vena cava

1 umbilical vein

carries about 85% of oxygenated blood and nutrients from placenta to fetal side

2 umbilical arteries

receives blood out of the fetus to the placenta

2nd-8th week AOG

embryonic dev’t

3rd-9th month AOG

fetal dev’t

testosterone, FSH, LH

male hormones

estrogen, progesterone, scanty amounts of testosteronefer

female sex hormones

fertilization (1-3 days)

sex of an individual is determined

placenta (human placenta)

• lifeline for mother and developing fetus

• acts as endocrine gland (i.e., secretes estrogen, progesterone, HCG)

• 7 functions: nutrients, barrier (protection), gas exchange, acquire enough nourishment, regulation of fetal body temp., removes waster, filters germs, storage of fats, glycogen, nutrients

Passive immunity

• mother’s antibody (Immunoglobulin G (IGG)) is transferred to the fetus

• provides immunologic protection

folic acid, iron, calcium, vit. d, DHA, Iodine, Folate

6-7 essential nutrients for pregnant mothers

folic acid

• synthetic form of vitamin B

• 600 mcg intake daily; after meal

folate

natural form of vitamin b

iron

for oxygenation; daily with vit. c for proper absorption

calcium

for fetal bone and heart dev’t

vit. d

for proper calcium absorption; daily 600 IU

DHA (Docosahexaenoic Acid)

• omega-3 fatty acid; for brain and eye dev’t

• daily 8-12 ounces

iodine

for thyroid hormone and nervous system dev’t; daily

HCG (Human Chorionic Gonadotropin)

• made in placenta

• linked to cause nausea and vomiting

24 weeks AOG)

fetal respiration movements (what week)

28 weeks AOG

lung surfactant is fully developed in what week

lung surfactant

keeps alveoli open of the fetus

MTORC1 (Mechanistic Target of Rapamycin Complex 1

• positive regulator of placental nutrient transport

• filtration system of the placenta

• responsible for cell growth and metabolism

• activates translation of proteins; integrates signals to multiple growth factors

catabolism

destructive metabolism

maternal side (dirty duncan; cotyledon, septum of cotyledum)

fetal side (shinySchultz)

types of placenta

schultz - out coming from center (70%)

duncan - maternal side will separate first

separation of placenta

• 6 weeks AOG

• maximal activity: 6-7 weeks

• full capacity to perform: 6-7 months

dev’t of liver

urea, nitrogenous waste (ammonia); urination; kidney

fetus will excrete __________________ through _____ from fetal blood to maternal blood and filtered by the mother’s ____

13-16 weeks AOG

fetuses are active urinators in the womb in what starting week?

under stress (decrease blood and oxygen supply)

fetus will defecate if it is ____

meconium stain

greenish fluid induction during delivery

meconium aspiration syndrome (MAS)

when a newborn breathes a mixture of meconium and amniotic fluid into the lungs around the time of delivery

Immunoglobulin G, M, A, E, D

antibodies essential for fetal health

immunoglobulin M

• current infection (can be seen)

• high fever, intense coughing = increase in this IG class

immunoglobulin A

• antibody found in breast milk

• highest form of antibody

• saliva, tears

immunoglobulin E

• for allergic reactions

• trouble-maker

immunoglobulin d

uncommon; connected to other antibodies - replacement for a missing Ig class

dizygotic twins, monozygotic twins

multiple pregnancy

dizygotic twins

• most common: 2/3 of cases

• ‘fertilization of more than one egg by more than one person

• non-identical, may be of diff. sex

• 2 chorion, 2 amnion

• placenta may be separate of fused

• 80%

monozygotic twins

• constant incidence of 1:250 births

• not affected by heredity

• not related to induction of ovulation

• constitute 1/3 of twins

• 70% are diamniotic monochorionic

• 30% are diamniotic dichorionic

• 20%

twins

most common type of multiple pregnancy

binovular

2 diff. ova

heteropaternal superfecundation

2 diff. fathers

homopaternal superfecundation

only 1 father

thoracopagus twins

most common; twins attached by chest or umbilicus

pycopagus twins

twins are commonly joined back to back of the spine and buttocks

craniopagus twins

twins are joined at the head or cranium

ischiopagus-tripus conjoined twins/ caudal twins

twins are joined at the pelvic area or in the lower GIT

thoracopagus twins, pycopagus twins, craniopagus twins, ischiopagus-tripus conjoined twins/ caudal twins

late splitting of eggs during the embryonic disk