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Human Creation and the Fetus Development Process in the Womb


1 Department of Medical Histology and Embryology, Tehran University of Medical Sciences, Tehran, IR Iran
*Corresponding author: Bagher Minaii Zangii, Department of Medical Histology and Embryology, Tehran University of Medical Sciences, Tehran, IR Iran. Tel: +98-2155693520, Fax: +98-2155693522, E-mail: minaezb@sina.tums.ac.ir.
Quran and Medicine. 2014 May; 3(1)
Article Type: Editorial; Received: Feb 24, 2014; Accepted: Feb 24, 2014; epub: May 10, 2014; ppub: May 2014

Keywords: Fetus; Development; Womb

1. Human Creation and Fetus Fate in Uterus


Imam Sadigh (AS) said: Oh Mofazzal, I start my speech with the story of human creation; take heed of that to be successful. First it was planned to cover the fetus in the womb, behind three membranes of darkness: abdomen (pelvic cavity), womb (endometrium), and uterus (amniotic sac), where it is unable to find food or ward off waste and inadmissible. It does not know its interest or loss. Uterine blood (vessels of endometrium) is its food; it is its only food, like water for the plant (1-5).

2. Birth and Child Nutrition


When the creation is complete, its mother feels labor pain, and the severity and difficulty of this pain causes the fetus be thrown out. when he is born (comes out from the tight uterus to the world), his body becomes hard and the skin can adapt to the air, and his eyes can bear the light; and that blood which was his former food, now with new color and smell, flows from his mother’s breasts. It is the most suitable food for the newborn. When a baby is born, he brings out his tongue and turns it around his mouth to ask for food. At this time, he finds mother’s breasts and sucks them as long as his body is fresh, inside is fragile, and organs are soft (6-9).

When he starts crawling, he needs hard and nutritious food to strengthen his body. From every side of his mouth, molar teeth grow so that he can chew the food and make it soft to swallow. This situation will continue until he reaches maturity. At this time if a male, hair grows on his face as a sign and dignity of man to be recognized from women and children; and if a female, her face will be clean from hair to give her beauty and freshness to win men’s heart and make human race viable and sustainable (10-13).

Oh, Mofazzal, Think well about these stages. Is it possible to have all these policies without a wise being? Do you know if he did not receive enough blood in the womb, he would be dry and wither like a plant without water? Do you know if his mother did not feel labor pain when he was complete in the womb, he would be buried alive in the womb, and if he were unable to bear the milk after birth, he would either starve or be fed with unsuitable or harmful food (14-16)? If his teeth did not grow on time, he would be unable to chew and swallow the food and always had to drink milk and his body did not gain the strength for work, and his mother could not take care of her other children because of him?

3. Embryonic Placenta and Membranes


Embryonic membranes include amniotic sac, yolk sac, allantois, and placenta with remarkable tasks such as: protection, nutrition, respiration, and excretion of embryo, and hormone production (17-20).

3.1. Placenta is Composed of Two Parts

1. Embryonic part, derived from chorionic sac

2. Maternal part, derived from endometrium; this part of uterus is called decidua which has three types: capsularis, basalis, paritalis (Figure 1).

Figure 1.
Embryonic Parts
3.2. Placenta Development

Early in the fourth week of embryonic development, a physiological connection is established between mother and embryo. In the eighth week, chorionic villi cover the surface of chorionic sac. Chorionic sac contains segments in which the villi regress. This part of chorionic sac is called smooth chorion. The symmetric segment of smooth chorion is basalis decidua in which villi branch and increase in number; it is called chorionic frondosum (21-24).

1. Embryonic part of the placenta: grows by chorionic surface and connects with maternal blood by the formation of villi (25-28).

2. Maternal part of the placenta: first it is formed by basalis decidua (a part of endometrium located in the depth of embryonic placenta), and because of the activity of basalis decidua, placental septum is formed in it and this septum causes the maternal part of placenta to turn into irregular spaces as cotyledon. Every cotyledon includes two or more villi and their branches. Intervillous spaces are full of blood. Maternal blood enters basalis decidua through spiral arteries, and spreads among the villi of basalis decidua and returns through endometrium veins. Decidua capsularis, a part of endometrium which encapsulates the surface of embryo and its membranes, with the progression of pregnancy connects to the paritalis decidua, and regresses in the 22nd week of the pregnancy because of the decrease of blood in decidua capsularis (29-31) (Figure 2).

Figure 2.
Placenta Parts
3.3. Blood Circulation in Placenta

1. Fetal circulation

2. Maternal circulation

3.4. Fetal Circulation

Venous blood reaches the placenta through fetal umbilical arteries. These umbilical arteries connect to a capillary, venous, arterial system which brings fetal blood close to maternal blood for metabolic and gas exchange between fetal and maternal blood and following that arterial blood enters the embryo through umbilical vein (32-35).

3.5. Maternal Circulation

Blood flows into the intervillous spaces, and gradually enters the maternal circulation. This blood, which comes from 80 to 100 branches of spiral arteries, by passing through cytotrophoblastic pores enters the intervillous spaces, and then the maternal blood reaches the endometrium veins. The blood volume in Intervillous spaces is about 150mL which is renewed every three or four minutes (36-38) (Figures 3 and 4).

Figure 3.
Placenta Circulation
Figure 4.
Fetal Transactions With Maternal Blood
3.6. Placental Membrane or Placental Barrier

This membrane which separates maternal blood from fetal blood includes: syncytiotrophoblastic, cytiotrophoblastic, villi connective tissue, and fetal capillary endothelium. In the late pregnancy, fibrous connective tissue surrounds villi and decreases the placental operation (39-41).

3.7. Placental Function

Placenta has three main functions: 1) metabolism, 2) material handling, and 3) hormone secretion. In metabolism, especially early in the pregnancy, it plays role in the synthesis of glycogen, cholesterol, fatty acids and other items. In material handling, material transfers via one of the following four mechanisms: simple diffusion, facilitated diffusion, active transport, and drinking. Also, red blood cells may exchange between mother and fetus because of placenta rupture or abruption. Active transport of some cells such as maternal leukocytes, Treponema pallidum, or some viruses and bacteria may cause disorders in the fetus. There is no or little transfer of cholesterol and protein hormones from maternal blood to the fetus; immunoglobulins can also pass through the placenta (42, 43).

3.8. Placental Hormones

Human Chorionic Gonadotropin (hCG)

Human Chorionic Somatomammotropin (hCS)

Human Chorionic Glycoprotein (hCG)

Human Chorionic Thyrotropin (hCT)

Human Chorionic Corticotropin (hCACTH)

4. Labor


Labor is facilitated by secretion of oxytocin hormone and adrenal cortex steroids.

Normal Vaginal Delivery consists of three stages:

1) Dilation of the cervix, in which painful uterine contractions are repeated consciously in less than 10 minute intervals. Cervix dilation time for the nulliparous women is about 12 hours.

2) Fetus passing through the cervix and vagina (delivery channel). For nulliparous about 50 minutes, and for multiparous about 20 minutes.

3) Placenta expulsion. Placenta separates from the spongy layer of basalis decidua. Removed placenta excretes in less than 10 minutes.

4.1. Mechanism and Symptoms of Labor

1) Cervix softening

2) Gradual opening of the cervix canal and urethra hole

3) Increasing oxytocin receptors in muscle cells of the uterus

4) Intensification of uterine muscle contractions in response to oxytocin.

4.2. Fetus Presentation inside the Womb

The fetus is presented inside the womb in three types:

1. Cephalic presentation

2. Breech presentation

3. Shoulder presentation

4.3. Umbilical Cord

Umbilical cord is 1-2 cm in diameter and 30-90 cm in length. It is covered by epithelial cells and mucoid connective tissue which contains Wharton’s jelly, and two umbilical arteries and one umbilical vein (44).

4.4. Amino-chorionic Membrane

Amniotic sac wall and smooth chorion form amino-chorionic membrane. This membrane is first connected to the capsularis decidua and then by demolishing capsularis decidua, connects to the paritail decidua. Therefore, in the 22nd week of the pregnancy, this connection forms between amino-chorionic membrane and smooth chorionic. The most common reason for premature labor is the rupture of amniotic sac. The volume of amniotic fluid is around one liter which spews out (45, 46).

4.5. Amnion and Amniotic Fluid

The amount of this liquid gradually increases; 30 mL in the 10th week, 350 mL in the 20th week, and 1000 mL in the 35th week. Amniotic fluid is replaced every three hours. This fluid is replaced through absorption by kidneys and excretion through urine. The low amount of amniotic fluid is called oligohydroaminos, and the high amount of the fluid is called polyhydroamnios (47, 48).

Amniotic fluid is exchanged between fetus and maternal blood circulation, and the fetus swallows 400 mL of amniotic liquid daily. Amniotic fluid contains 99% water; the rest is mineral and organic materials, and epithelial cells. In the late pregnancy the amount of protein in amniotic fluid decreases (9, 23, 26).

Amniotic fluid functions are as follows:

1. Facilitates embryonic development at the external surface.

2. Prevents amniotic membrane sticking to the embryo

3. Prevents fetal injuries by transport of wastes through maternal blood

4. Adjusts fetal body temperature

5. Makes fetus free and float for development of its muscles and bones

6. Prevents strike transmission to fetus

5. Yolk Sac


In the ninth week of pregnancy, the yolk sac is like a compressed pear with the diameter of five millimeters. In the 20th week of pregnancy, the yolk sac shrinks and is invisible (32).

5.1. The Importance and Functions of Yolk Sac

1. In the second and the third weeks of pregnancy transfers nutrients to the embryo

2. From the third to the sixth week of pregnancy is responsible for hematopoiesis

3. Dorsal part of the yolk sac involves in the creation of primary intestine in the fourth week of the pregnancy

4. Primordial germ cells migrate from the dorsal part of the yolk sac to gonads, in the third week of the pregnancy

5.2. Destiny of the Yolk Sac

At the end of the sixth week of the pregnancy, the yolk sac is removed when the midgut is formed. In the tenth week of the pregnancy the yolk sac is between the chorionic cavity and amnion. The yolk sac gradually regresses with approaching the delivery time. If it remains in the ileum wall, it is called Meckel's diverticulum (23-25).

6. Allantois


At the end of the second week of the pregnancy (day 16 of pregnancy) a finger shaped tail is formed from the dorsal part of the yolk sac which is called allantois. At the end of the eighth week of the pregnancy the external part of the allantois regresses. The internal part of the allantois firstly turns into the fibrous cord urachus along with the formation of bladder, and then turns to the median umbilical ligament which continues from the bladder to the umbilicus (17, 22, 30).

Allantois has two important functions:

1. It involves in hematopoiesis, in the third and the fourth weeks of pregnancy

2. Allantois blood veins turn into one umbilical vein and two umbilical arteries (Figure 5)

Figure 5.
Allantois parts and Blood Veins

Acknowledgments

There is no acknowledgment

Footnotes

Financial Disclosure: There is no financial interest.
Funding/Support: The study is self-funded.

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Figure 1.

Embryonic Parts

Figure 2.

Placenta Parts

Figure 3.

Placenta Circulation

Figure 4.

Fetal Transactions With Maternal Blood

Figure 5.

Allantois parts and Blood Veins