ch 14 ch 1

• what is the "major departure" from general mammalian embryogenesis

  rapidly enlarging brain that characterizes our species
• why does birth occur before the brain is fully matured in humans

  so that the expanding head is able to fit through the maternal pelvic outlet without injury to the baby's brain or to the mother
• what is meant by the statement that "the human baby is born helpless"

  brain is not fully developed
• how is human puberty seen as "roughly equivalent to metamorphosis"

  the animal becomes sexually mature and its body form changes as does its behavior
• humans undergo a period of "senescence", what does this mean?


  bodily functions diminish leading up to the person's eventual deaths; getting older
• conceptus


  zygote through birth
• embryo


  8 weeks following fertilization (cleavage and gastrulation)
• preimplantation embryo


  product of fertilization through attatchment of trophoblast to the uterine wall
• when does implantation occur? what happens to the uterine blood supply and what is formed

  implantation occurs when the embryo attatches to the uterus and burrows inside the uterine epithelium; it remodels the uterine blood supply and forms the placenta
• when is a woman said to be pregnant

  only when the embryo is embedded within the uterus
• between which embryonic weeks are most of the embryos tissues and organs specified and initiated

  weeks 2 and 8
• when is the embryo called a fetus

  9 weeks after fertilization
• what is the fetal stage characterized by

  growth and refinement of organs and tissues
• when does human birth usually occur

  38 weeks after fertilization
• the 3 temporal portions of a human pregnancy and describe them

  first trimester (from fertilization-start of week 12), second trimester (week 12-26), third trimester (remodeling and prepping the fetus for birth)
• ductus arteriosus


  an opening that diverts blood from the pulmonary artery into the aorta
• foramen ovale


  an opening that allows blood to pass through the septum that separates the right and left atria