1. المحاضرة الثالثة

2. The placenta is a discoid, organ which connects the fetus with the uterine wall of the mother. It is a site of nutrient and gas exchange between the fetus and mother. Umbilical cord is attached to its center. It develops By the end of the third month and it has two components: fetal part formed of Chorionic villi & maternal part formed by decidua basalis. Its Weight at full term is about 500 – 600 gms

3. Surfaces: It has 2 surfaces: 1- fetal surface: which is smooth because it is covered by an amniotic membrane. The umbilical cord is attached centrally to this surface. 2- maternal surface: which is rough, reddish and is characterized by presence of 15- 20 lobules or cotyledons

4. Full-term placenta

5. Fetal part: Chorionic villi They are numerous finger like processes called villi. There is a space between villi called intervillous space and is filled with maternal blood. Placental circulation: Maternal blood in the intervillous space- Foetal Blood in the villi of the Placenta

6. Placental barrier: -These are layers separating the fetal blood in the villi from maternal blood in the intervillous space. -They prevent mixing of fetal and maternal blood but they allow passage of certain substances throw it.

7. Functions Of The Placenta 1.Exchange of gases O2 and CO2 (Respiratory). 2.Exchange of Nutrients and Electrolytes such as, water, carbohydrates, proteins, lipids, and vitamins (Nutrition). 3.Excretion of waste products as urea and uric acid (kidney). 4.Transmission of Maternal antibodies resulting in passive immunity of the fetus (Protective).

8.  Estrogen (for uterine growth and development of the mammary gland).  HCG (maintains the corpus luteum so prevents other ovulations and prevents menses during pregnancy. It is excreted by mother in the urine early in pregnancy, their presence is used as an indicator of pregnancy (pregnancy test). 5- Hormone Production (Endocrine) as:  Progesterone (to maintain pregnancy).

9.  Relaxin hormone to soften the uterine ligaments to help delivery.  Somatomammotropin leads to development of mammary glands.

10. 6- Functions of placental barrier: 1.It prevents most organisms from passing to the fetus, so it acts as a protective mechanism but, many viruses such as German measles and poliomylitis virus traverse the placenta. These viruses may result in congenital malformations. 2.Most of the drugs in addition to cocaine, heroin cross the placenta and cause serious damage.

11. Abnormalities of placenta 1- According to site: Placenta Praevia the placenta is attached to the lower uterine segment (due to low level of implantation of the blastocyst). It causes severe antepartum haemorrhage. There are three types:

13. 2- Abnormalities according to number: 1- Double placenta (bilobed or bidiscoid placenta). 2- Triple placenta (trilobed). 3- Accessory placenta (accessory one or more lobes). It may cause severe postpartum hemorrhage if the accessory lobe is retained in the uterus after labor.

14. Umbilical Cord Length: about 50 cm Diameter: 1-2 cm Contains two arteries and one vein, surrounded by mucoid connective tissue (Wharton jelly)

15. Abnormalities of the umbilical cord  very short cord - 20-30 cm - it brings problems during delivery  very long cord - 80-90 cm - it tends to entwine around the neck or extremity of the fetus  true knots - occur in about 1% of pregnancies, they form during labor as a result the fetus passing through a loop of the cord - it causes of fetal anoxia

16. The Amniotic Fluid It is clear and watery. The source of the fluid still remains unsettled. It may be fetal, maternal or both. Functions of the amniotic fluid 1- protection of the embryo against shock, blows or pressure. 2- maintaining a uniform pressure for the proper growth and differentiation of the delicate tissues of the embryo. 3- It allows fetal movements and maintains a constant environmental temperature.

17. Abnormalities of the Amniotic fluid 1.Polyhydramnios This is a condition when the volume of the amniotic fluid exceeds two liters. 2.Oligohydramnios: In this condition the fluid is scanty in amount.