Human Anatomy 205

Developmental Anatomy (Embryo)

See the Visible Embryo (Fertilization, Implantation, Gastrulation and Folding)
See Multi-dimensional Human Embryo at Univ. of Mich.
Topics to Study

Ovulation releases oocyte with zona pellucida + corona radiata

Sperm head contains nucleus (23 chromosomes)

Capacitation factors enable sperm to release acrosomal enzymes

Fertilization (fusion of sperm and ovum)

occurs in uterine tube
acrosomal reaction enables a sperm head to penetrate into oocyte
cortical reaction within oocyte forms fertilization membrane (blocks further sperm penetration)
head of sperm within oocyte is male pronucleus
oocyte completes oogenesis (meiosis) to form female pronucleus
Pronuclei fuse to form diploid nucleus of zygote

Zygote is new cell resulting from fertilization

Cleavage is rapid mitotic division of zygote

Spermatozoan
sperm

Morula (mulberry-like cluster of many cells), early embryo no larger than zygote

Blastocyst next embryo stage forms a cavity

Implantation is attachment of blastocyst embryo to endometrium of uterus

Extra embryonic membranes [yolk sac] [allantois] [amnion] [chorion]

Formation of three primary germ layers [layers differentiate into body systems]

Ectoderm differentiates into neural tube and epidermis
Mesoderm differentiates into muscle, bone, reproductive and urinary organs
Endoderm differentiates into lining of digestive tract, lungs, liver and pancreas

Human Blastocyst

Placenta [chorion + decidua basalis of endometrium]
- Exchange of molecules between maternal and fetal blood
- placenta is endocrine organ [hCG is early hormone] [ see diagram]
Gestation is period of development in uterus
- Embryo is first 8 weeks
- Fetus is week 9 to week 38
Parturition (giving birth)
- Contraction of myometrium of uterus
- Requires the action of the hormone oxytocin

Dynamic Human
at McGraw-Hill