GIS02 Innervation blood supply and lymphatic drainage of the GI tract Flashcards
Arterial supply of GI tract
3 major arteries (ALL originate from ***Abdominal aorta):
- Celiac trunk (supply **foregut)
- lower esophagus
- stomach
- **duodenum (up to proximal half of descending duodenum) - Superior mesenteric artery (supply **midgut)
- rest of duodenum
- jejunum
- ileum
- ascending colon
- cecum (with appendix)
- **proximal 2/3 of transverse colon - Inferior mesenteric artery (supply ***hindgut)
- rest of transverse colon
- descending colon
- sigmoid colon
- most of rectum
Abdominal aorta
- Starts at aortic hiatus (T12)
- Ends as bifurcation (left/right common iliac arteries) at L4
- Branches:
- Anterior (unpaired)
- Celiac trunk
- -> **Left gastric artery (stomach, adjacent esphagus)
- -> **Splenic artery (spleen, stomach, pancreas)
- -> ***Common hepatic artery (liver, stomach, pancreas, gallbladder, duodenum)
- Superior mesenteric artery (pancreas, small intestine, appendix, ***2/3 large intestine)
- Inferior mesenteric artery (***last 1/3 of large intestine)
- Lateral (paired)
- Inferior phrenic arteries (diaphragm, inferior esophagus)
- Adrenal arteries (adrenal glands)
- Renal arteries (kidney)
- Gonadal arteries (testes, ovaries) - Posterior (paired)
- 4 pairs of Lumbar arteries (vertebrae, spinal cord, abdominal wall, lumbar region)
***Celiac trunk, Superior and Inferior mesenteric artery (Many anastomoses to form a circuit)
Celiac trunk
- -> L gastric artery (anastomose with R gastric artery)
- -> Common hepatic artery –> R gastric artery + Hepatic artery proper (L/R) + Gastroduodenal artery
- -> Splenic artery –> L /R gastroepiploic artery (anastomose with hepatic artery proper)
Superior + Inferior mesenteric arteries
- -> R colic artery (superior) –> Ileocolic artery + Intestinal arteries
- -> L colic artery (inferior) –> Sigmoidal arteries –> Superior rectal artery
- -> Middle colic artery (anastomose between L colic artery, R colic artery)
Blood supply of abdominal wall
Posterior abdominal wall:
4 pairs of Lumbar arteries
Anterior abdominal wall:
**Superior + **Inferior epigastric artery
- ***Internal thoracic artery –> Superior epigastric artery (form anastomoses with Inferior epigastric artery ) + Musculophrenic artery
- Common iliac artery –> ***External iliac artery (+ Internal iliac artery) –> Inferior epigastric artery (兜底返上去)
Venous drainage:
Hepatic portal vein
Common pathway for transport of venous blood from abdominal viscera
- **2 main contributors:
1. Splenic vein (from Inferior mesenteric vein)
2. Superior mesenteric vein
Splenic vein + Superior mesenteric vein –> Hepatic portal vein –> Hepatic vein –> IVC
Portal system
Connection between 2 capillary network
GI tract, Spleen, Pancreas capillary –> Hepatic Portal vein –> Liver capillary network –> Hepatic vein
Collateral channels
Can drain into portal vein + system circulation (places where anastomosis between portal and systemic circulation)
—> ***Portosystemic anastomoses
1. Gastroesophageal junction
2. Around anus
3. Anterior abdominal wall around umbilius
Elevated pressure in portal vein (cannot go through liver) (血谷翻轉頭):
—> Venous enlargement (varices) around sites of portosystemic anastomoses
—> 1. Esophageal varices
—> 2. Haemorrhoids
—> 3. Caput medusae
Clinical significance: GI haemorrhage
Lymphatic drainage
- Follow neurovascular bundles throughout body
- Clusters of lymph nodes: monitoring immune system (found along course of lymphatics)
***Intestinal trunks + Left lumbar trunk –> Cisterna chyli –> Thoracic duct
Central lymph nodes in abdomen named according to associated artery:
- Celiac nodes
- Superior mesenteric nodes
Main ganglia and plexuses
GI tract (smooth) supplied by Autonomic NS Parasympathetic + Sympathetic
- ***Celiac plexus (with Celiac ganglia)
- Hepatic plexus –> liver, gallbladder
- Gastric plexus –> stomach
- Splenic plexus –> spleen
- Pancreatic plexus –> pancreas, duodenum - Aortic plexus
- **Superior mesenteric plexus (with Superior mesenteric ganglion)
- Suprarenal / Renal plexus
- Testicular / Ovarian plexus
- **Inferior mesenteric plexus (with Inferior mesenteric ganglion) - ***Superior hypogastric plexus
- ***Inferior hypogastric plexus
- ***Sympathetic trunk
- Paravertebral ganglia (lumbar ganglia)
- Sacral ganglia
- Coccygeal ganglia
***Sympathetic innervation
- 1st cell body: in CNS (spinal cord T1-L2)
- 2nd cell body: in peripheral ganglia
4 main ganglia (Prevertebral):
- Celiac
- Aorticorenal
- Superior mesenteric
- Inferior mesenteric
Sequence:
Preganglionic sympathetic neurons
–> Prevertebral ganglia/plexus
–> Associated organs
Functions:
- ↓ motility, peristalsis
- ↑ sphincter muscle contraction
- ↓ absorption
- ↓ glandular secretion
- Vasoconstriction
Greater, Lesser, Least splanchnic nerve:
Thoracic splanchnic nerve
- ***Greater splanchnic nerve:
T5-T9
–> Celiac + Superior mesenteric ganglia/plexuses (i.e. Prevertebral plexus)
–> Foregut + associated organs - ***Lesser splanchnic nerve:
T10-T11
–> Celiac + Superior mesenteric ganglia/plexuses (i.e. Prevertebral plexus)
–> Midgut - Least splanchnic nerve:
T12
–> Aorticorenal + Inferior mesenteric ganglia/plexuses (i.e. Prevertebral plexus)
–> Kidneys + Adrenal gland - ***Lumbar splanchnic nerve:
L1-L2
–> Inferior mesenteric + Inferior hypogastric ganglia/plexuses (i.e. Prevertebral plexus)
–> Hindgut - ***Sacral splanchnic nerve
***Parasympathetic innervation
- Ganglia in the organs
Sequence:
Preganglionic parasympathetic neurons
–> Prevertebral plexus
–> Associated organs
Functions:
- ↑ motility, peristalsis
- Relax sphincter muscles but ***↑ smooth muscle contraction
- ↑ absorption
- ↑ glandular secretion
Vagus splanchnic nerve (CN X)
Medulla
–> Prevertebral plexus
–> Foregut + Midgut
Pelvic splanchnic nerve
S2-S4
–> Inferior hypogastric plexus (Prevertebral plexus)
–> Hindgut + Pelvic + Perineal organs
Prevertebral ganglia
Prevertebral ganglia: Sympathetic
Enteric nervous system
One of divisions of Autonomic NS:
(the other: PNS, SNS)
- Myenteric plexus
- primarily involved in initiation and control of smooth muscle motor pattern e.g. peristalsis
- have ***both Parasympathetic (with ganglions) and Sympathetic input - Submucosal plexus (**Secretomotor)
- coordinates reflexes e.g. secretion, absorption
- coordinates motor control of smooth muscle
- **only Parasympathetic innervation
Autonomic reflex and referred pain
Sensory pathway: afferent fibres from gut --> goes through sympathetic splanchnic nerves --> ganglion of sympathetic trunk --> ***white ramus communicans --> ***spinal nerves --> ***Dorsal root ganglion --> dorsal root --> according level in spinal cord
Brain mixes up afferent signals with those in Dermatome
–> referred pain felt on skin
Efferent pathway: Efferent fibres from ***Lateral horn --> ***Ventral root --> spinal nerves --> white ramus communicans --> ganglion of sympathetic trunk --> sympathetic splanchnic nerves
***Summary
Foregut: - ***distal esophagus, stomach, duodenum (up to ***major duodenal papilla), ***pancreas, ***liver, ***gallbladder Blood: - Celiac trunk + ***Portal vein Lymph: - Celiac nodes surrounding celiac trunk SNS: - Greater splanchnic nerve (T5-T9) PNS: - Vagus nerve
Midgut: - duodenum, jejunum, ileum, cecum, ascending colon, ***proximal transverse colon Blood: - Superior mesenteric arteries + veins Lymph: - Superior mesenteric nodes surrounding Superior mesenteric artery SNS: - Lesser splanchnic nerves (T10-T11) PNS: - Vagus nerve
Hindgut: - ***distal transverse colon, descending colon, sigmoid colon, proximal rectum Blood: - Inferior mesenteric artery + vein Lymph: - Inferior mesenteric nodes surrounding Inferior mesenteric artery SNS: - Lumbar + Sacral splanchnic nerve PNS: - Pelvic splanchnic nerve (S2-S4)
