When cells are veryclose to one another, some of the mol-ecules on the cellsâ plasma membranesmay bind together in specific ways.Many of the important interactionsbetween cells in early developmentoccur by means of direct contact be-tween cell surfaces (figure 7.3 a).ecause these proteins may constituteless than 0.01% of the total mass of protein in a cell, puri-fying them is analogous to searching for a particular grainof sand in a sand dune! However, two recent techniqueshave enabled cell biologists to make rapid progress in thisarea. 7.1 Cells signal one another with chemicals.
The Maenads (pronounced Maynads) were female revelors in the cult of Dionysus. The god's frenzied Thracian worshippers, the Maenads, accompanied Dionysus on his travels crowned with wreaths of ivy, oak or fir and draped in the skins of animals.
The female gonads produce female gametes (eggs); the male gonads produce male gametes (sperm). After an egg is fertilized by the sperm, the fertilized egg is called the zygote (pronounced: ZY-gote). When a baby girl is born, her ovaries contain hundreds of thousands of eggs, which remain inactive until puberty begins. female's internal reproductive organs are the vagina, uterus, fallopian tubes, and ovaries. The vagina is a muscular, hollow tube that extends from the vaginal opening to the uterus. The vagina is about 3 to 5 inches (8 to 12 centimeters) long in a grown woman. Because it has muscular walls it can expand and contract.