Forming an embryo (exam 2) Flashcards
Placentation is the formation of…..
placenta
Placentation is complete by weeks 14-16. As a fully developed organ, (maternal and fetal tissue working together) the placenta provides….
-nutrition
-excretion of wastes and metabolites
-respiration/ventilation
-endocrine function (hormones)
The placenta connects to the conceptus via the umbilical cord that contains ___________________, which carries deoxygenated blood, CO2, and wastes from the fetus, and ___________________ through which nutrients and oxygen are carried from the mother to the fetus
2 umbilical arteries, a single umbilical vein
Note: This is opposite of most veins/arteries!!!!
How does transport across the placenta occur?
-simple diffusion (oxygen, CO2, and other lipid soluble substances
-facilitated diffusion (water soluble glucose)
-active transport (amino acids and iron)
T/F: Maternal and fetal blood do not mix because blood cells cannot move across the placenta
TRUE
Maternal and fetal blood do not mix because blood cells cannot move across the placenta. RBCs are not exchanged, but the ____________________ provide ample SA for the 2-way exchange of substances between maternal and fetal blood
chorionic villi (theres a chorion before the placenta)
The fetal component of the placenta is derived from the _________________ and ____________________________, the maternal component is derived from the ________________________________
trophoblast, extraembryonic mesoderm, uterine endometrium
(by the beginning of the 2nd month, the trophoblast is characterized by a great number of secondary and tertiary villi, which give it a radial appearance)
As the blastocyst implants, it stimulates a response in the uterine endometrium called the….
decidual reaction
The cells of the endometrial stroma accumulate lipids and glycogen and these cells are called….
decidual cells
The endometrial stroma thickens and becomes more highly vascularized. This is called….
decidua
The protruding portion of the embryo (closest to the uterine cavity) is covered by a thin capsule of endometrium called the ___________________. The embedded embryonic pole of the embryo is underlain by a zone of decidua called the ________________, which will participate in forming the mature placenta (maternal side). The remaining area is called the ________________
decidua capularis, decidua basalis, decidua parietalis
As the fetus grows, the decidua capularis is pressed against the decidua parietalis, and in the 5th/6th months, the decidua capularis disintegrates. By this time, the placenta is _______________ and has distinct fetal and maternal surfaces
fully formed
Mesoderm cells travels through the primitive streak and forms the cardiogenic area or primary heart field which then forms 2 tubes under the influence of ________ from endoderm. At the inferior end, each endocardial tube is connected to vitelline veins
VEGF (vascular endothelial growth factor)
What happens during lateral folding for cardiovascular development?
1) 2 endocardial tubes fuse and forms primitive heart tube
2) viteline veins fuse and forms the sinus venous (inflow tract for vein to go into the heart)
3) aortae fuse and forms aortic sac (outflow tract)
4) primitive pericardial cavities fuse around the heart tube amd forms the pericardial cavity
2 endocardial tubes fuse and forms the…..
primitive heart tube
Viteline veins fuse and forms the…
sinus venous (inflow tract of vein into heart)
Aortae fuse and forms the….
aortic sac (outflow tract)
Primitive pericardial cavities fuse around the heart tube and forms the….
pericardial cavity
What happens during craniocaudal folding?
primitive heart is pushed towards the chest and the heart tube reaches the thorax
The heart tube elongates, swells, and forms 5 dilations, from caudal to cranial:
EXAM Q
1) sinus venous (caudal end, this is a major way into heart)
2) atrium
3) ventricle
4) bulbus cordis
5) truncus arteriosus (cranial end)
note: most things form cranially to caudally but the heart tube is opposite!
The sinus venosus develops into….
R/L sinus horns that bring in blood
primitive atrium develops into….
L/R atria
primitive ventricle forms the….
L ventricle
bulbus cordis develops into the….
R ventricle and the outflow tract of both ventricles
(primitive ventricle forms the L ventricle)
trucus arteriosus develops into the…..
aorta and pulmonary trunk
What is septation of the heart?
endocardial cushion develops into the atrioventricular region to divide the heart (atria->ventricle)
What is atrial septation?
formation of 2 septa and 3 holes that separate L and R atria
the 2 septa are called septum primum and septum secundum
Atrial septation involves the formation of 2 septa and 3 holes. What are the 2 septa called?
1) septum primum
2) septum secundum
___________________ forms and extends down towards the fused endocardial cushions to split the atrium into 2 atria. It has holes called the ostium primum and ostium secundum
Septum primum
______________________ has a hole called the foramen ovale (allows blood to go L-R and skip pulmonary circuit since lungs aren’t developed yet). The presence of both the ostium secundum (from septum primum) and foramen ovale allows a right to left shunt to be present in the developing heart
Septum secundum
The ventricular septation separates the ventricles into L and R. The ____________________ of the ventricles has 2 components: one muscular and one membranous. Endocardial cushions also appear within the truncus arteriosus which grow towards each other and form a spiral septum, dividing the outflow tract into L and R sides
interventricular septum
In the fetal circulation, _______________ are required to bypass the liver and nonfunctioning lungs
vascular shunts
To bypass lungs: 2 shunts, firstly the ___________________ between the 2 atria, which is responsible for bypassing the majority of the circulation. Any blood that does not pass through the foramen ovale enters the pulmonary trunk, which is linked to the distal arch of the aorta by the _____________________ (connects to the aorta which goes out to the body)
foramen ovale, ductus arteriosus
To bypass liver: the _________________ shunts a portion of umbilical vein blood flow directly to the IVC. Thus, it allows oxygenated blood from the placenta to bypass the liver.
ductus venous
At birth, circulatory shunts need to close to allow….
the normal adult circulation to be established with foramen ovale and ductus arteriosus
increased pressure in the atrium closes the foramen ovale into a fossa
muscular wall of heart contracts to close the ductus arteriosus after birth
After the 3 germ layers form during gastrulation, the body folding forms the endometrial ________ at the cranial end of the embryo, thereby delineating the inner tube of the tube-within a tube body plan
foregut
On day 22, the foregut produces a ventral evagination called the ______________________, or lung bud, which is the primordium of the lungs
respiratory diverticulum
As the lung bud grows, it remains ensheathed in a covering of splanchopleuric _____________, which will give rise to the lung CT and vasculature and to the CT, cartilage, and muscle within the bronchi
mesoderm
Development of the esophagus, stomach, trachea, and lungs form the ___________ region is tightly linked
foregut
The lengthening lung bud bifurcates into L/R primary bronchial buds, which will give rise to the…
2 lungs
In the 5th week, a 2nd generation of branching produces 3 secondary bronchial buds on the right side and 2 on the left. These are the primordia of the future….
lung lobes
The bronchial buds and their splanchnopleuric sheath continue to grow and bifurcate, gradually filling the….
pleural cavities
by week 16, the 16th round of branching generates _______________ bronchioles, which subsequently divide into 2+ respiratory bronchioles
terminal
by week 26, these respiratory bronchioles have become invested with capillaries and are called…..
terminal sacs or primitive alveoli
The _____________________ is created by the body folding during the 4th week consisting of a blind-ended sac cranial foregut, a blind-ended caudal hindgut, and a midgut open to the yolk sac through the vitelline duct
endometrial gut tube
The gut endoderm forms the lining (epithelium) of the GI tract. The adjacent ______________________ forms the other layers and components of the gut
splanchnic mesoderm
As body folding is completed, there remains a thin layer of splanchnic mesoderm called the ____________________, connecting the gut tube along its entire axial length to the dorsal portion of the abdominal body wall. The dorsal mesentery is a vascular conduit and supplies all of the essential oxygen and nutrients to the developing gut
dorsal mesentery
By the 5th week, the thoracic and abdominal portion of the ___________ is visibly divided into the pharynx, esophagus, stomach, and proximal duodenum. Hepatic, cystic, and dorsal and ventral pancreatic diverticula bud from the caudal duodenum into the ventral mesogastrium and give rise, respectively, to the liver, gallbladder and cystic duct, and pancreas
foregut
What are the derivatives of the foregut (cranial end)?
exam q!!!
-primordial pharynx
-lower respiratory system (lungs)
-esophagus and stomach
-duodenum, proximal to the opening of the bile duct
-liver, biliary apparatus (hepatic ducts, gallbladder, and bile duct), and pancreas
The foregut derivatives, other than the pharynx, lower respiratory tract, and most of the esophagus, are supplied by the _______________, the artery of the foregut
celiac trunk
What are the derivatives of the midgut?
-small intestine, including the duodenum distal to the opening of the bile duct
-cecum, appendix, ascending colon, and right 1/2-2/3 of the transverse colon
What are the derivatives of the midgut supplied by?
the superior mesenteric artery
What are the derivatives of the hindgut?
-left 1/3-1/2 of the transverse colon, descending colon, and the sigmoid colon, rectum, and the superior part of the anal canal
-epithelium of the urinary bladder and most of the urethra
All hindgut derivatives are supplied by the….
inferior mesenteric artery
