[...]... infection, and more than half of all women have suffered from such an infection at some time 54 MICROLIFE HUMAN BODY II 55 Bad Company Deadly Nightmare icroorganisms can be habitual companions of the human body There are bacteria that live in the digestive tract and interact in a positive way with humans because they exchange nutrients However, there is a group of parasitic protists that obtain benefits... established pathways to the interior of the human body: the eyes and ears; the respiratory system, through the nose and mouth; the digestive system, in food and water; the genitals and anus; and the skin, the most exposed pathway, although the bacteria can enter only through wounds Eyes and ears Respiratory system Digestive system Genitals Skin HUMAN BODY II 51 50 MICROLIFE Minuscule Life Anatomy of... day 40 of intrauterine life The shape of the face has begun to develop and will continue to do so until the third month 20 C1 DE CIGOTO A EMBRIÓN FROM ZYGOTE TO EMBRYO Day HUMAN BODY II ATLAS VISUAL DE LA CIENCIA CUERPO HUMANO II 21 1 44 LENGTH: 0.6 inch (16 mm) WEIGHT: 0.02 ounce (0.5 g) FORMATION OF THE PLACENTA The cells of the trophoblast extend inside the blood vessels of the uterus The blood... three-dimensional images They show the entire surface of the fetus and help to identify any deformation 28 FETAL DEVELOPMENT AND CHILDBIRTH HUMAN BODY II 29 Growth Begins The Taste Buds uring the fourth month, the mother senses the fetus's first movements The fetal body changes; its face is completely formed The skin has a pinkish tone, and the first ribs and cartilage appear The external sex organs finish... are already developed and the baby kicks with rapid movements 34 FETAL DEVELOPMENT AND CHILDBIRTH HUMAN BODY II 35 Closer with Every Moment he beginning of the third trimester of pregnancy marks a key point in gestation The process of strengthening and calcification of the bones of the fetus begins Its body needs nutrients, such as calcium, folic acid, and iron The baby can already open and close its... AND CHILDBIRTH HUMAN BODY II 45 An Answer to the Resemblance he baby has the mother's eyes but the father's hair color; the nose is like the grandfather's, and the mouth is like the grandmother's These and other possible combinations are caused by genetic inheritance The genes transmitted by the father combine with genes in the mother's egg, forming a single cell that will turn into a new human being... EACH CELL IN THE HUMAN BODY 1 2 6 MAN The normal karyotype of men is 46XY ADENINE (A) 3 CYTOSINE (C) Each human cell (except for a few, such as red blood cells) has a nucleus Inside the nucleus are the genes, contained in the chromosomes Each cell nucleus has 46 chromosomes with the person's genetic information Each gene has information with a code that determines a function in the body, such as hair... as bacteria or cancer cells? In this chapter, we will also show you how platelets, another defense system of the body, prevent hemorrhages, or bleeding While learning about our internal functions, you will be surprised and captivated by illustrations and much more 48 MICROLIFE HUMAN BODY II 49 Bacteria acteria are the smallest, most abundant, and hardiest lifeforms on Earth They are so microscopic... innermost layer It forms the lining of the digestive and respiratory tracts, liver ducts, pancreatic ducts, and glands such as the thyroid gland and the salivary gland 14 FROM ZYGOTE TO EMBRYO HUMAN BODY II 15 First Human Forms Day ine days after fertilization, the blastocyst has installed itself in the wall of the uterine endometrium, where it will spend the rest of the nine months of gestation before... the new viruses disperse They are ready to attack again 52 MICROLIFE HUMAN BODY II 53 Fungi 0.00020 inch ungi are living beings from the Fungi kingdom that are similar to plants, but they do not have the ability to synthesize their own food; this forces many of them to be parasites of other vegetables or animals and, of course, humans Multicellular fungi tend to be formed by filaments and spores that . ■ Seoul ■ Sydney ■ Taipei ■ Tokyo Britannica Illustrated Science Library Britannica Illustrated Science Library HUMAN BODY II HUMAN BODY II © 2 008 Editorial Sol 90 All rights reserved. Idea. Number (volume): 978-1-59339-810-1 Britannica Illustrated Science Library: Human Body II 2008 Printed in China w ww.britannica.com Human Body II Contents From Zygote to Embryo Page 6 Fetal Development and. Control Marilyn L. Barton Manufacturing Kim Gerber, Director Britannica Illustrated Science Library Britannica Illustrated Science Library Enc yclopædia Britannica, Inc. Jacob E. Safra, Chairman