Development of VILLI Week 2 to week 3

Development of villi

• Week 2 to week 3

• Primary villi: cytotrophoblast+syncytiotrophoblast

• Secondary villi: extraembryonic mesoderm enter the

• primary villi

• Tertiary villi: extraembryonic mesoderm =>CT+BV

Amnion - Fluid

• Functions

• Mechanically cushion
• Protect from fetus adhesion
• Movement
• Maintain Temp

• Abnormalities

• 1) too much (polyhydramnios)
• >2000 ml
• Abnormal digestive system or CNS
• - esophageal atresia
• - anencephaly
• 2) too little (oligohydramnios)
• <500 ml
• Abnormal urinary system
• - poor development of kidney
• - urethra atresia

Yolk sac and Allantois

• Yolk sac

• Primitive Gut
• 3rd week, Germ Cells
• 3rd to 6th week,
• Blood island

• Allantois

• Caudal extension of hindgut
• Allantoic A pairs
• Allantoic V pairs

Umbilical Cord

• Folding – a purse string closure

• Amnion membrane covered
• Cord: mucous CT, 3 vessels,yolk sac ,allantois
• At birth, 50-60 cm, 2cm diameter
• Long – knots
• Short – placenta detachment

Placenta - Overview

• Functions as:

• Lungs, GI tract, Liver, Kidneys, Endocrine

• Placenta proper:

• Chorion frondosum (fetus)+ Decidua basalis (mother)

Anatomy of the Placenta

• Fetal – Chorion

• Chorion Frondosum
• Chorion Laeva

• Maternal – Decidua

• Decidua Basalis
• Decidua Capsularis
• Decidua Parietalis

Anatomy of the Placenta

• At birth 500 g

• 15-25 cm Diameter

• 3 cm thick

• Anchoring villi

• Decidual septa  15-20 Cotyledons

Placental-Fetal Circulation

• Fetus:

• umbilical A carries O2/nutrient depleted blood to cap. of chorion , exchange with maternal blood of the intervillous spaceumbilical V

• Mother:

• spiral A intervillous space uterine V

Placental Function

• 1.Exchange of Metabolites: nutrients antibody, waste

• 2.Defense barrier

• 3.hormone production

• human chorionic gonadotropin (HCG)

• Begin: end of 2nd week

• Highest: 2nd month

• Estrogen and progesterone

• Placental lactogen

Twins

• Two types:

• One zygote (monozygotic)
• Two (or more) zygotes (dizygotic)
• 2 (or more) oocytes
• Non Identical

Twins - Monozygotic

• Zygote split

• 2-4 cell
• 2 amn, 2 chorion
• Blastocyst
• 2 amn, 1 chorion
• (most common)
• Bilaminar germ disc
• 1 amn, 1 chorion
• (rarely happen)
• Incomplete splitting
• Conjoined twins

Conjoined Twins