Midgut and Hindgut Flashcards
What does the midgut and hindgut include?
Intestines (minus duodenum) and rectum/anus
Is the jejunum intraperitoneal or retroperitoneal?
Intraperitoneal
Is the ileum intraperitoneal or retroperitoneal?
Intraperitoneal
Where will you find plica circulae the most abundant?
(mucosal folds) Jejunum
What is the blood supply to the jejunum?
Long vasa recta from arterial arcades off the SMA (superior mesenteric artery)
What is the blood supply to the ileum?
Short vasa recta from arterial arcades off the SMA (superior mesenteric artery)
What are arterial arcades?
Anastomoses - so when the intestines are twisted, there will still be blood delivered
Where does the colon begin?
Ileocecal junction
What are the retroperitoneal organs?
SADPUCKER
- Suprarenal glands
- Aorta
- Duodenum (parts 2-4)
- Pancreas
- Ureters
- Colon (ascending and descending)
- Kidneys
- Esophagus
- Rectum
What parts of the colon are intraperitoneal?
Cecum, transverse colon, sigmoid colon
What suspends the appendix, transverse colon and sigmoid colon?
Mesoappendix
Transverse mesocolon
Sigmoid mesocolon
Appendix is a part of what system?
Immune system
What are the 2 anal sphincters?
Internal - smooth muscle
External - skeletal muscle
What organs does the superior mesenteric artery supply?
Pancreas Duodenum Small intestines (jejunum and ileum) Cecum Ascending and Transverse colon
At what level does the SMA come off the aorta?
L1
What are the main SMA branches?
Jejunal and ileal branches Inferior pancreaticduodenal Middle colic Right colic Ileocolic
What organs does the inferior mesenteric artery supply?
Descending and sigmoid colon
Superior rectum
At what level does the IMA come off the aorta?
L3
What are the main IMA branches?
Left colic
Sigmoidal
Superior rectal
What artery is created between a major anastomosis between the SMA and IMA?
Marginal artery
What can the marginal artery help prevent?
Intestinal ischemia due to obstruction
What is the 3 main blood supplies to the rectum?
Superior rectal
Middle rectal
Inferior rectal
Describe the overall course of the sympathetics in the midgut/hindgut?
Nerves bypass the sympathetic chain and the presynaptic nerves synapse at ganglia
What are the sympathetic nerves for the midgut/hindgut?
Greater, lesser, least thoracic splanchic
Lumbar splanchics
Sacral splanchics
Levels of Greater thoracic splanchic nerve
T5-T9
Where does the Greater thoracic splanchic nerve synapse?
Celiac ganglia
Levels of the Lesser thoracic splanchic nerve
T10-T11
Where does the lesser thoracic splanchic nerve synapse?
Superior mesenteric ganglia
Levels of the least thoracic splanchic nerve
T12
Where does the least thoracic splanchic nerve synapse?
Aorticorenal ganglia
Levels of the lumbar splanchic nerves
L1-L5
What are the 3 places the lumbar splanchic nerves synapse?
Superior mesenteric ganglia
Inferior mesenteric ganglia
Hypogastric ganglia
Levels of the sacral splanchic nerves
S1-S5
Where do the sacral splanchic nerves synapse?
Hypogastric ganglia
What are the ganglia options for sympathetics to synapse at for midgut/hindgut innervation?
Celiac Superior mesenteric Aorticorenal Inferior mesenteric Hypogastric
What are the nerves for the parasympathetic innervation of the midgut/hindgut?
Vagus N.
Pelvic splanchic nerve
What are the levels of the pelvic splanchic nerves
S2-S4
Describe the course of the pelvic splanchic nerves
- Carry pre-synaptic axons from sacral levels to join the hypogastric plexus
- Then they travel to organs
- Synapse on to post-synaptic neurons WITHIN the organ
What organs are innervated by the pelvic splanchic nerves (parasympathetics)?
Descending colon
Sigmoid colon
Rectum
Anal canal
Somatic afferent pathway is pain due to?
Irritation of the parietal peritoneum
Describe the somatic afferent pathway
The brain interprets the pain as though irritation occurred in the skin of the region supplied by the same sensory ganglia and spinal cord segments as that region of affected peritoneum
Is the somatic afferent pathway well localized?
YES
Visceral afferent pathway is pain due to?
The organ itself
Describe the visceral afferent pathway
Pain from the organ itself is sent to splanchic nerves that will take it to the spinal cord
Is the visceral afferent pathway well localized?
NO