GESTATION FROM CONCEPTION TO BIRTH
141. A uterus with the ovaries and the fallopian tubes. One of the tubes has attached itself to the right ovary to take up an ovum. a) The uterus, b) the ovaries, c) the fallopian tubes, which have a thin internal duct through which the ovum reaches the uterus, d) the round ligaments, e) the broad ligaments, f) the cervix, g) a part of the vagina. 142. A fertilized female ovum, magnified 500-fold. The inner area consists of a large number of little globules, and at their center we can see a small bubble, the germinal vesicle, out of which the human being is generated. The afterbirth grows around the outer shell. The ovum is fertilized by spermatozoids. 143. A drop of male semen, magnified 600-fold. 144. Two spermatozoids, magnified 600-fold. They consist of mucous matter. 145. Six spermatozoids, same magnification as before, placed in close proximity to one another.
Separation of the ovum from the ovary
When the ovum has reached the uterus, about fourteen days after its fertilization, it is fixated there and will grow during the forty weeks of a normal pregnancy to about 50cm. in length and 6 pounds in weight, so that it will become 30,000 times larger and 50,000 times heavier than it was in the ovary. It receives the nutrients for this growth from the mother's body.
146. An ovary, cross-sectioned in the center. Each of the visible follicles (Graafian follicle) contains an ovum: a) a cross-sectioned ripe follicle. The female ovum is attached to its margin; b) scars that remain where the ovum has separated from the follicle. 147. A closed ovary with a ripe follicle. The ripening follicles move gradually to the surface of the ovary and remain closed until the fallopian tube (a) encloses them; then the follicle ruptures, and the small ovum, which is just visible in the center, is washed out into the uterine tube by the liquid surrounding it. 148. The attached fallopian tube has been partly slipped back. The Graafian follicle has expulsed the mature ovum and it is moving forward in the uterine tube. 149. An ovary showing the wound caused by the separation of the ovum; we can see coagulated blood with a yellow edge. When the Graafian follicle ruptures, a small orifice is opened up; this closes again, and the cavity of the follicle is filled with blood. The wound contracts progressively until all that remains is a line of green spots with a yellow edge (see No. 605). 150. A dissected uterus showing how the ovum is carried into the uterus: a) the blastocyst, which is formed before the ovum (now called zygote) reaches the uterus; b) a zygote that has arrived in the uterus; it pushes the blastocyst forward and thus creates a second sac, the amniotic cavity; c) dissected uterine tube; d) ruptured Graafian follicle from which the ovum has emerged. After the separation has occurred, the fimbriae of the fallopian tube detach themselves from the ovary and hang in a loose tangle, as on the other side. It also should be noted that the fallopian tubes can attach themselves to both ovaries at the same time: this is how twins, triplets, etc. are generated. It is also possible that two ova detach themselves from the same ovary if they happen to develop very close to each other. 151. The uterus of a pregnant woman, about 8 days into pregnancy: a) the blastocyst; b) the amniotic cavity created by the forward movement of the zygote; c) the fine white flakes (trophoblast) that will become the placenta. 152. A conceptus at ten days. The bubble-like structure appended to it was once the ovum from which the conceptus developed. 153. A conceptus at fifteen days. The yolk sac has moved away and the conceptus has attached itself to the placental villi. 154. An embryo of three weeks. The yolk sac has moved all the way to the back. The red spot between the head and the body is the heart, which develops externally. 155. An embryo in the middle of the fourth week: a) the umbilical cord; b) the dissected amniotic sac; c) the villi which form the blood vessels of the placenta; d) the decidua capsularis. 156. An embryo of about five weeks: a) the placenta; b) the amniotic sac; c) the amnion or the chorion; d) a part of the decidua capsularis. At this stage the mouth and nasal cavity form an orifice, and arms and legs are still of equal length. The parts of the brain are still divided. 157. An embryo in the middle of the seventh week: at this stage the legs have started to turn downward and the head has taken on a more rounded shape. 158. An embryo of eight weeks: the nostrils have formed and the mouth is still open. (Individual organs are identified as in No. 156). 159. An embryo of nine weeks with intact amnion (a). Every embryo is suspended in liquid like this; this liquid is known as the amniotic fluid. In all the preceding models, the amnion was cut open to display the embryo. The chorion (b) has been dissected to show chorionic and placental vessels, and d) the decidua capsularis.
The formation of the face
(Greatly magnified) 160. The head (in profile) of a conceptus of ten days. In reality, the head is about the size of the head of a small pin (see No. 152): a) the cerebrum, b) the corpora quadrigemina, c) the medulla oblongata, d) the eye, e) the facial bulges which show the faint lines of the facial folds; f) the bulge from which the heart will form. 161. The head of an embryo of fourteen days: a) the cerebrum; b) the maxillar fold; c) the lingual fold, from which the tongue will be formed; d) the mandibular fold; e) the hyoid fold; f) the heart bulge, which has started to bend forward. The two prominent blue spots on both sides are the eyes. 162. The head of an embryo of about two and a half weeks. The formation of the oral cavity is becoming apparent: a) is turning into the mandible; b) into the tongue; c) into the maxillae; d) the hyoid fold; e) the heart. 163. The head of an embryo of about three weeks: the cerebrum is beginning to separate. The facial folds have grown together: a) turning into the maxillae; b) the tongue; c) the mandible; d) the heart. 164. The head of an embryo of three and a half weeks: a) the maxillae; b) the tongue, which is moving more and more back into the oral cavity; c) the mandible; d) the hyoid fold; e) the heart, which is detaching itself increasingly from the head, but still remains external. 165. The head of an embryo of four weeks. The oral cavity and tongue are hinted at. In the center of the maxillae two elevations emerge (a), which play a role in the formation of the nose, b) the tongue, and the mandible (c). The two prominent spots on either side are the eyes. 166. The head of an embryo of five weeks: a) is forming the forehead; b) the nasal cones; c) the tongue; d) the mandible. 167. The head of an embryo of six weeks. One can see how the nasal cones (a) grow larger and begin to form the nostrils. The orifice (b) will develop into the ears. 168. The head of an embryo of seven weeks: the oral and nasal cavities are still an orifice; if a malformation occurs at this stage, it results in a cleft palate. 169. The head of an embryo of eight weeks: one can see how the nasal folds are starting to merge with the maxillae; if this process is not completed, it results in a simple or double harelip. 170. The head of an embryo of eight and a half weeks: the head has grown very round and its shape is much more recognizable; the upper lip and the nasal folds have fused, the nose has started to rise, and the eyes have become more prominent. 171. The head of an embryo of nine weeks. The face has recognizably human features and the mouth is growing smaller; the nose starts to grow downwards and the eyes have almost reached their final position; in about eight days eyes and mouth will close (see an embryo of nine weeks, No. 159).
The formation of the genital organs
(Magnified) 172. An embryo of five weeks. At this stage, the formation of the generative organs begins. 173. Magnified representation of the genitals at the same stage. In the centre, a fine ridge is noticeable, over which a promontory can be seen: a) the coccyx. 174. The two folds merge at the top and become more and more prominent. 175. The ridge becomes ever longer, the prominent part becomes the mesorchium or the mesovarium. 176. New ridges develop on both sides; these will either form the labia majora or the scrotum. From the genital ridge, the anus will also develop; all that is required is the fusion of the central segment (a). 177. An embryo of about ten weeks: the central segment of the ridge has grown together (a) and on top of this there remains a ridge; underneath it is the circular orifice of the anus. From the fifth until the tenth or eleventh week, the sex of the embryo cannot be distinguished; it is only from the twelfth week that a marked change occurs. 178 and 179. From the twelfth week. In No. 178, the orifice in the prominent part of the ridge remains: the child will be female. In No. 179 the orifice grows together, with the exception of a small opening that belongs to the urethra and forms the mesorchium. 180. An embryo in its actual size after twelve weeks, the stage at which its sex is determined. 181 and 182. From the fourteenth week. No. 181 will be female: the prominent part is the mesovarium, the ridges on either side will form the labia majora. No. 182 will be male, the small opening in the mesorchium is the urethral orifice. The bulge (a) will form the scrotum. No. 183 and No. 184. From the sixteenth week. No. 183 is female, the prominent part becomes the mesorchium and falls back increasingly in development; the labia majora (a) become more prominent. No. 184 is male. 185 and 186. Here the sex is easy to recognize. No. 185 is female, No. 186 is male. 187. An embryo of ten weeks, the eyes are still open. No. 188. An embryo of eleven weeks. Here the eyes are shut. 189. An embryo of thirteen weeks, suspended in the womb. The back of the head foremost is the correct position. 190. An embryo after four months, attached to the placenta. 191. An embryo of four and a half months, suspended in the womb. The uterus has changed: the cervix is no longer broad, but round. 192. A foetus of seven months. This age is of great interest, because embryos born at this stage are capable of surviving. The organ next to the foetus is the placenta. It consists of a large number of blood vessels, which criss-cross and branch intricately and are connected to the uterus, as can be see in all births. Blood is transported through the white (umbilical) cord to the child's heart. 193. A foetus of eight months. The blood vessels in the umbilical cord have been exposed - blood is supplied through the thick blue tube and carried out through the two red ones. 194. The circulation of blood of the child before its birth during the ninths month. 1. The heart. 2. The aorta, which distributes blood in all parts of the body. 3. The pulmonary artery, which transports its blood to the aorta rather than to the lungs. As soon as a human being is born, blood is drawn to the lungs by aspiration; as a consequence, the opening between the two arteries grows shut and the lungs are supplied with blood. From the branches of the aorta which run towards the legs, two further vessels branch off. These go to the navel and turn towards the umbilical vein until they reach the placenta. At its back, they spread as capillaries and fuse with the mother's blood vessels. Blood then returns, carrying the necessary nutrients, through the aorta (5), but this time it runs through the liver and from there through the inferior vena cava (6) into the right atrium (7) of the heart. Through an opening which is sealed off by a valve after birth, blood is carried into the left atrium (8) as well and is then, by the simultaneous contraction of the atria pushed into both ventricles, whence it is propelled into the aorta and pulmonary arteries, which transport it through the entire body. 9. The arteries that supply blood to the head and arms. 10. The veins that transport it back to the heart again. 11. The liver. 12. The portal vein carries blood back from the abdominal entrails. 13. The gallbladder. 14. The spleen. 15. The kidneys. 16. The adrenal glands. 17. The bladder. 18. The uterus and ovaries. 19. The rectum. The first developments of the human embryo's external shape. 195. A child, a few days before its birth. Chest and abdominal cavity are opened up. 1. The thymus, which will eventually vanish completely. 2. The heart. 3. The pericardium. 4. The lungs. 5. The diaphragm. 6. The liver, which in a child is relatively larger than in an adult. 7. The umbilical vein. 8. The two umbilical arteries. 9. The bladder. 10. The stomach. 11. The small intestine. 12. The large intestine.
The first developments of the embryo's external form
196. An embryo of the third week, 0.75 cm long. Four visceral loops with their open ridges. The vertebral disks, heart and liver can be seen through the outer covering layers. The extremities exist as stumps, the coccyx sticks out prominently as a tail. 9-fold magnification. 197. A five-inch long embryo of the fifth week. The developments of the frontal section of the head-end are not clearly visible because of the embryo's position. The extremities display first developments of the bends of elbows and knees. Magnified 9-fold. 198. A six-inch long embryo of the sixth week. The anterior part of the imperfectly closed visceral ridge has developed into the external orifice of the ear. Elbows and knees have become more apparent. The skin starts to develop into fingers. Magnified 8-fold. 199. A seven-inch long embryo of the seventh week. The outer ear is present in the shape of a bulge surrounding the auricular orifice. The segments of the limbs have separated. Fingers are recognizable, but not yet divided; toes are starting to be detectable. 8-fold magnification. 200. A nine and a half-inch long embryo of the eighth week. The ear is still erect and shows the auricle in development. The fold of the eyelid becomes recognizable. The child's sex is as yet undetermined. Magnification 9-fold.
The development of the external shape of the human face
201. The head of an embryo of the third week with the four visceral loops, at the entry into the visceral cavity and the first signs of the maxillae. Magnified 20-fold. 202. The head of an embryo, showing formation of the mandible, fundamental development of the ear, and closure of the third visceral ridge. 11-fold magnification. 203. The head of an embryo of the fifth week, showing central and lateral frontal processes and nostrils, and closure of the second visceral ridge. 11-fold magnification. (14)