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12. Extraembryonic Membranes
Developmental Anatomy Test II
Terms in this set (21)
Placenta, inner cell mass
All extraembryonic membranes except for the _ come from the _.
"Bag of waters". Thin sac surrounding the conceptus proper. Formed from the inner cell mass/somatopleure. Very thin. Single layer of ectoderm along inside. Lined superficially with mesoderm. Filled with amniotic fluid. Expands as embryo grows.
Buffers force on embryo. Accommodates growth (expands). Allows freedom of movement (aids muscle development). Prevents amnion from sticking to embryo/fetus (decreases tearing). Maintains body temp (water of fluid absorbs heat before temp changes).
Connects embryo proper to chorion. Source: extraembryonic mesoderm. Starts out relatively short, widens/lengthens to become umbilical cord.
Ventral evagination of the hind gut. Source: endoderm. Extends into body stalk. Provides blood vessels of umbilical cord. Forms urinary bladder. Makes blood for embryo (humans). Stores nitrogenous waste/functions in respiration (reptiles/birds).
Allantois, umbilical arteries, urachus, median umbilical ligament
Developmental steps of allantois. (4)
Blood vessels taking blood to placenta.
Fibrous cord attaching to umbilicus to top of urinary bladder.
Median Umbilical Ligament
Urachus in the adult.
Where urine is stored before being released. Formed from the allantois.
Tube that transports blood between placenta and conceptus proper. Source: body stalk + endoderm + allantois.
1 part of umbilical cord. Blood vessels that take blood away from conceptus proper.
1 part of umbilical cord. Blood vessels that brings blood to conceptus proper.
Yolk Sac/Umbilical Vesicle
Starts as an opening at the midgut. Source: hypoblast. Makes blood for embryo. Provides primordial germ cells. Stores yolk and provides nutrients in birds/reptiles.
Exchange organ between maternal and fetal circulation. Chorion and decidua.
Fetal part of the placenta. Forms from trophoblast. Chorionic villi allow exchanges between fetal and maternal blood.
Maternal part of placenta. Forms from the endometrium. Provides an area safe from the mother's immune system.
1 function of the placenta. O2and nutrient exchange. Travels from maternal blood to fetal blood. Umbilical veins receive O2 and nutrients. CO2 and waste exchange. Travels from fetal blood to maternal blood. Umbilical arteries are emptied of wastes/CO2.
Protective proteins made by immune system. Maternal antibodies cross placenta to protect the fetus.
Endometrial changes due to implantation. Proves an area safe from the mother's immune system.
Extensions of chorion where exchanges occur between fetal and maternal blood. Facilitate gas and nutrient exchange. Branching shape (high surface area for exchanges). Bring fetal and maternal blood close together (contain fetal blood vessels and surrounded by maternal blood vessels). Close proximity facilitates exchanges without directly mixing blood.
THIS SET IS OFTEN IN FOLDERS WITH...
8. Fertility Control
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