Rutgers Functional Human Anatomy Lec 21 (Pregnancy & Embryonic development)

Prenatal development

pre-embryonic development:

- fertilization to implantation

- approx. 2 weeks

Embryonic development:

- implantation to end of 8th week of pregnancy

- 1st 2 months

Fetal development:

- 9th week to birth

- 3rd-9th month

- fetus

prenatal development known as

gestation period (9 month period)

- 40 weeks

3 month trimesters:

1st, 2nd, 3rd

1st trimester

rudiments of all organs appear

most dangerous period in prenatal life (40% conceptions survive)

3 months (1-12 weeks)

4 events in 1st trimester

cleavage (sequence of cell division):

- blastocyst forms

implantation:

- embryo implants to endometrial lining

placentation:

- formation of placenta

embryogenesis:

- development of embryo

implantation in 1st trimester

blastocyst further develops, creating 3 layers

process called gastrulation and makes germ layers:

ectoderm

mesoderm

endoderm

ectoderm forms

integumentary system

skeletal system

entire nervous system

part of endocrine system

respiratory system

digestive system

mesoderm forms

integumentary

skeletal

entire muscular

placentation (1st trimester)

Placental circulation:

- blood flow from fetus to placenta in paired umbilical arteries

- blood returns via single umbilical vein

amnion

innermost membrane of placental sac, encloses embryo/fetus

chorion

outer most membrane

contributes to formation of placenta

mucus plug

forms in area of cervix to prevent bacteria from entering

embryogenesis (1st trimester)

- 12 weeks post-fertilization

organogenesis:

organs begin to form

2nd trimester

- development of organs and organ systems

- fetus looks human

- fetus covered by amnion

- fetus grows faster than placenta

3rd trimester

- rapid growth

- all fetal organs become functional

changes in uterus during gestation

- uterus increases in length (7.5cm to 30cm)

- contains almost 5L fluid

- uterus & contents weigh around 22 lbs

- maternal abdominal organs are pushed out of their normal positions

labor

series of strong, rhythmic uterine contractions

goal of labor

parturition:

expulsion (delivery) of fetus

3 stages of labor

dilation:

- cervix dilates

- fetus pushed by muscular contractions into cervical canal

- amnion ruptures

expulsion:

- movement of fetus through cervical canal and vagina

- delivery can be helped by episiotomy (cutting skin between vagina & anus) or cesarian section

placental:

- ejection of placenta (afterbirth)

breech presentation

birth position in which the buttocks, feet, or knees emerge first

premature labor

- labor begins before fetus completes normal development

- 23/24-36 weeks generally survive w/ care

- before 23/24 weeks generally dies (respiratory/cardiovascular/urinary system not developed enough)

neonatal period

from birth to 1st month

events in neonate during neonatal period

- lungs fill w/ air

- blood circulation changes w/ closing of ductus arteriosus and foramen ovale of heart

- heart rate drops from 120-140 bpm to 70bpm

- breathing rate drop from 30-60 breaths per min to normal rate (30)

- kidneys filters infant own blood

- digestive system becomes active

- metabolic rate increased to maintain warmth for few days after birth