placentation

• What is the process of embryo implantation?

  It involves direct interaction of the blastocyst with the lumenal epithelium of the uterus.

  
• How can implantation types be categorized?

  They can be categorized as central, eccentric, or interstitial.
• What characterizes superficial implantation?

  The embryo remains within the uterine cavity.
• What occurs during eccentric implantation?


  The embryo partially embeds into the uterine tissues.
• What is interstitial implantation?

  It entails the embryo penetrating deep into the uterus and becoming fully engulfed in the endometrial tissue.

  
• What is the function of the yolk sac?

  It provides the developing embryo with nutrition via vitelline circulation.

  
• What is vitelline circulation?


  It is the circulation between the yolk sac and the embryo.

  
• What tissues form the yolk sac?

  The yolk sac is formed from hypoblast endoderm and extraembryonic mesoderm.
• What is the splanchnopleura in a vertebrate embryo?


  It is the layer of tissue comprising the endoderm and the inner layer of mesoderm.
• What are the types of implantation and their associated species?

  • Central implantation: Carnivores, Ungulates
  • Eccentric implantation: Rodents (mouse, rat)
  • Interstitial implantation: Primates, Humans, Guinea Pigs
• What is the function of the amnion in poultry?

  The amnion protects the embryo from physical shocks and injury.
• What is the chorion in mammals, birds, and reptiles?

  It is the outermost fetal membrane around the embryo.

  
• What functions does the chorion-allantoic membrane perform?

  It acts as a respiratory organ providing oxygen to the embryo.

  
• What tissues compose the amnion and chorion in mammals?

  The amnion is composed of ectoderm and somatopleure; the chorion has an outer trophoblast and inner somatic mesoderm.

  
• What is the role of the allantois in mammals?

  It is the embryonic precursor of the umbilical cord and stores urinary waste.

  
• How does the allantois function in poultry?

  It serves as a respiratory organ and a reservoir for excreta.
• What is the function of the chorioallantoic placenta in mammals?

  It functions in the synthesis, transport, and metabolism of hormones during pregnancy.
• What are the stages of twin formation in relation to extraembryonic membranes?

  (A) Before trophoblast formation

  (B) After trophoblast formation but before amnios formation

  (C) After amnios formation
• What is the composition of the placenta during pregnancy?

  It is composed of uterine/maternal placenta and fetal placenta.
• What is the difference between chorioallantoic and choriovitelline placenta?

  Chorioallantoic placenta is formed by the fusion of chorion and allantois, while choriovitelline placenta is formed by the fusion of yolk sac and chorion.
• What are the types of placentas based on morphology?

  1. Complete diffuse
  2. Incomplete diffuse
  3. Cotyledonary/Multiplex
  4. Zonary
  5. Discoid

  
• What characterizes a complete diffuse placenta?

  It has a homogeneous distribution of villi with no smooth chorion.
• What is a cotyledonary placenta?

  It has villi concentrated at the cotyledon, forming placentomes with caruncles.

  
• What is a zonary placenta?

  It has villi concentrated in a central band with the rest being smooth chorion.

  
• What is a discoid placenta?

  It has villi concentrated in a discoid zone.

  
• What is the histological classification of placenta based on?

  • Degree of penetration of chorionic villi into the uterine endometrium
  • Number of tissue layers separating maternal and fetal blood circulation

  
• What are the layers that substances must pass through to reach the fetus?

  Endothelium, connective tissue, endometrium, chorion epithelium, connective tissue, endothelium.

  
• What is the difference between deciduate and adeciduate placentas?

  Deciduate placentas cause hemorrhage due to deep fetomaternal interdigitations, while adeciduate placentas separate easily at birth without hemorrhage.
• What are the types of placentas based on histological classification?

  1. Epitheliochorial
  2. Syndesmochorial
  3. Endotheliochorial
  4. Haemochorial

  
• What characterizes an epitheliochorial placenta?

  It has no uterine degradation during implantation and consists of 6 layers.
• What is a haemochorial placenta?

  It has blood in contact with the chorion and consists of less than 4 layers.

  
• What is the role of the placental barrier?

  It protects the fetus from harmful substances in maternal blood while allowing nutrient and oxygen transfer.
• What is the function of the chorionic sac and umbilical cord?

  The chorionic sac contains everything the chorion holds except the embryo, while the umbilical cord connects mother and fetus for nutrient exchange.

  
• What are the characteristics of the equine placenta?

  • Omphaloplacenta at the beginning, then allantoplacenta
  • Complete diffuse placenta with many villi
  • Epitheliochorial placenta
  • Adeciduate placenta
  • 11 months gestation

  
• What are the characteristics of the carnivore placenta?

  • Omphaloplacenta then allantoplacenta
  • Each fetus has individual appendages
  • Zonary placenta with marginal hematoma
  • Endotheliochorial placenta
  • 60 days of gestation
• What are the characteristics of the ruminant placenta?

  • Allantoplacenta
  • Cotyledonary placenta
  • Epitheliochorial/Syndesmochorial placenta
  • Adeciduate placenta
  • Cow = 9 months gestation, Sheep = 5 months gestation

  
• What are the characteristics of the pig placenta?

  • Many fetuses in one litter
  • Omphaloplacenta
  • Incomplete diffuse placenta
  • Epitheliochorial placenta
  • Adeciduate placenta
  • Gestation = 3 months 3 weeks 3 days

  
• What occurs during the fetal period?

  It involves growth, consolidation, and maturation of organs and tissues.
• What are the changes that occur at birth?

  Changes include cardiorespiratory adjustments, thermoregulation, and immunological changes.
• What is cellular differentiation?

  It is the process by which a less specialized cell becomes a more specialized cell type.