Reproductive System: Reproduction and Embryogenesis

Stages of Development

zygote → 2-, 4-, 8-, 16- cell embryo (cleavage) → morula → blastula (blastocyte, implantation) → gastrula

Ectoderm (attractoderm)

epidermis, hair, nails, epithelial of nose, epithelial of mouth, epithelial of lower anal canal, lens of eyes, nervous system (and adrenal medulla), inner ear

Mesoderm (meansoderm, means of getting around)

musculoskeletal system, circulatory system, (most of) excretory system, gonads, muscular and connective tissue of digestive and respiratory systems, adrenal cortex

Endoderm (endernal organ lining)

epithelial of digestive tract, epithelial of respiratory tract (and lungs), pancreas, thyroid, bladder, distal urinary tract, (part of) liver

First Trimester

Major organs

22 D - heart beat

Eyes, gonads, limbs, liver

5 W - 10mm

6 W - 15mm

7 W - cartilagenous skeleton (turns to bone later)

8 W - “fetus,” organs made, brain developing

3 M - 9m

Second trimester

So much growth

Humanlike face

Moving a lot

Toes and fingers elongate

6 M - 30-36cm

Third Trimester

7-8 M - rapid growth and brain development

9 M - active transport of antibodies to fetus

Less active due to less room, growth slows

Phases of Birth

cervix thins, amniotic sac ruptures → strong uterine contractions → birth → placenta and umbilical cord expelled