chapter 16 embryo development

inner cell mass forms

the embryo

outer trophoblast will form

the placenta

Syncytial trophoblast cells

secrete enzymes that allow blastocyst to penetrate the uterine lining and become buried in the endometrium

amniotic fluid

cushions and protects the embryo from trauma and extreme temperatures and keeps the fetal tissues moist

yolk sac

provides nourishment to the embryo while the placenta is being established

what forms the chorion ?

the extraembryonic mesoderm and trophoblast layers

in the third week of development a process known as gastrulation occurs and divides into three primary germ layers, what are they?

1. ectoderm

2. mesoderm

3. endoderm

epiblast becomes

ectoderm

hypoblast becomes

endoderm

Ectoderm

gives rise to epidermis, glands and nervous tissue

mesoderm

form muscle , blood, bones , heart and kidneys

endoderm

gives rise to the epithelial lining and glands of digestive , respiratory

Allantois

forms part of they urinary bladder and contriubutes. to the stalk

mesoder forms a connecting stalk between the embryonic disc and developing chorion which will become:

the umbilical cord

what is ectopic pregnancy

implantation that occurs outside of the uterus

where location does not support its growth

what is placenta previa ?

when the placenta attaches low in the uterus

may be covering the opening of uterus

Dizygotic twins

two eggs are released during ovulation and is fertilized by different sperms, sharing 50% of genes

this is known as faternal twins

Monozygotic twins

a single fertilized egg splits into two embryos

sharing 100% genetic material

known as identical twins

what is breech presentation?

the fetus in the longitudinal, lie with the buttocks or lower extremity entering the pelvis first

false labour pains

knwon as braxton hicks

contractions are unpredictable and dont follow a patter

this does not lead to cervical changes

True labour pains

contractions become regular and occur predictable interval

causes cervix to dilate