Exam #4: Abdominal Cavity Embryology Flashcards
Ectoderm
- Integument
- Nervous System
- Proctodeum
- Stomoteum
What is the proctodeum?
Primary lining of the anus
What is the stomodeum?
Secondary lining of the mouth
Mesoderm
- Muscles
- Muscle walls
- Connective tissue
- Bones
Endoderm
- Lining of the gut
- Gut derived organs
When does the embryo form a primitive gut tube?
4 weeks
What is the primitive gut tube connected to?
Yolk Sac
What is the yolk sac? What are the functions of the early yolk sac?
- Yolk sac provides the fetus with nourishment prior to implantation (2-3weeks)
- Hematopoesis prior to development of the liver
What connects the primitive gut tube to the yolk sac?
Yolk stalk or omphalocentric duct (future umbilical cord)
Describe the contents of the foregut.
Stomodeum–>Proximal 1/3 of the duodenum
- Celiac Trunk
- Pharyngeal pouches
Describe the contents of the midgut.
Distal 2/3 of duodenum–> proximal 2/3 of colon
- Superior mesenteric artery (SMA)
- Yolk stalk
Describe the contents of the hindgut.
Distal 1/3 of colon–>proctodeum
- Inferior mesenteric artery
- Allantois (waste sac)
What is recanalization?
Hollowing out of the primitive gut tube
What can an error in recanalization produce?
Stenosis (narrowing) or atresia (complete blockage)
What is a mesentery?
- Double layer of peritoneum formed by splanchnic mesoderm
- Functions to connect organs to the body wall
What are the three remnants of the ventral mesentery?
1) Lesser Omentum
2) Falciform Ligament
3) Coronary Ligament
Lesser Omentum
Sheet of mesentery from the liver to the stomach & duodenum
Falciform Ligament
Attaches the liver to the ventral body wall
Coronary Ligament
Attaches the liver to the diaphragm
What is the definition of intraperitoneal & what organs are intraperitoneal?
Organs suspended in the mesentery
- Stomach
- Spleen
- Transverse Colon
What is the definition of primarily retroperitoneal & what organs are primarily retroperitoneal?
Organs that have always been external to the peritoneum
- Esophagus
- Rectum
- Anal canal
- Kidneys
What is the definition of secondarily retroperitoneal & what organs are secondarily retroperitoneal?
Organs initially develop in the mesentery but end behind the mesentery after folding & rotation
- Distal 2/3 of the duodenum
- Ascending & descending colon
What is the mnemonic for all of the retroperitoneal organs?
SADPUCKER
Suprarenal glands Aorta (& Vena Cava) Duodenum (Distal 2/3) Pancreas Ureters Colon (Ascending & Descending) Kidneys Esophagus Rectum
List the organs of the foregut.
- Pharynx
- Esophagus
- Stomach
- Proximal 1/3 of the duodenum
Outpocketings
- Pharyngeal pouches
- Lower respiratory system
- Liver
- Pancreas
- Gallbladder
Describe the development of the esophagus.
Tracheal-esophageal fold splits into two tubes, the esophagus & trachea
Esophageal atresia
Complete blockage of the esophagus
Polyhydramnios
Abnormal build up of amniotic fluid; an indication of esophageal atresia
- Fetus “drinks” amniotic fluid
- Esophageal atresia= unable to “drink” & increase in amniotic fluid that is not being recycled
Describe the development of the stomach.
- Dorsal border grows faster than the ventral border–>greater & lesser curvatures
- Rotates 90 degrees CLOCKWISE along the longitudinal axis
- Lesser curvature moves right
- Greater curvature moves left
Describe the location of the right & left vagus nerves in relation to the stomach.
Vagus nerves run alongside the stomach
- Right vagus ends on the dorsal surface
- Left vagus ends on the ventral surface
Describe the development of the pancreas.
Pancreas forms from two buds; dorsal &ventral
- Dorsal bud elongates as the ventral remains same
- Fuse together b/c of stomach rotation
What is an annular pancreas?
When there are two ventral pancreatic buds that form & fuse around the gut tube–>strangulation of the intestines
What is special about the embryology of the spleen?
It is NOT an endodermal derivative; rather, it is a mesoderm derivative (outpocketing of the dorsal mesentery)
List the organs of the midgut.
- Distal 2/3 of the duodenum
- Cecum
- Appendix
- Ascending colon
- Proximal 2/3 of the transverse colon (to left colic flexure)
Describe the development of the midgut.
Midgut rotates COUNTER-clockwise around the SMA
- Elongates & forms as U-shape w/ SMA as axis & Yolk stalk as apex
- End of rotation cecum descending into right lower quadrant
- Causes secondarily retroperitoneal configuration
Non-rotation
- Intestine does NOT rotate as it re-enter the abdomen
- Causes duodenal obstruction
- Can lead to midgut volvulus i.e. catastrophic twisting of the midgut
Reversed Rotation
Midgut rotates CLOCKWISE instead of COUNTER-CLOCKWISE
Subhepatic Cecum & Appendix
Cecum adheres to the inferior surface of the liver
List the organs of the hindgut.
- Distal 1/3 of the transverse colon
- Descending colon
- Sigmoid colon
- Rectum
- Anal canal
Outgrowths
- Urinary bladder
- Urethra
Urorectal Septum
- Divides the allantois & yolk sac
- Separates cloaca into urogenital membrane & anal membrane
What is the significance of the pectinate line?
Above= endoderm w/ pressure & stretch receptors Below= ectoderm w/ pain receptors
