Lecture 2: Alimentary Structures Flashcards
What are alimentary structures?
Structures that relate to NOURISHMENT or SUSTENANCE
What are the only places that are ectodermly derived in the GI tube?
Oral cavity
Inferior 1/3 of the anal canal (below the pectinate line)
What do the regions of the gut tube (foregut, midgut, hindgut) have that serves to distinguish them from one another?
- Arterial blood supply
- Innervation
- Relationships to mesentery
Where does the bile duct enter the duodenum?
At the separation between foregut and midgut
How do you separate regions of gut tube?
Foregut is the point of entry of bile duct into duodenum
Midgut to hindgut is proximal 2/3 and distal 1/3 of transverse colon
Is the spleen part of gut tube?
No because it is mesoderm derived
What is in the foregut?
Celiac trunk 1. Esophagus, 2. stomach 3. duodenum (1st and 2nd parts) 4. liver 5. pancreas 6. biliary apparatus 7. gall bladder Below are derivatives of gut tube but not part of GI tract per se 8. Pharyngeal pouches 9. Lungs 10. Thyroid
What innervates the foregut?
- Parasympathetic = Vagus nerve
2. Sympathetic = T5-T9
What innervates the midgut?
- Parasympathetic = vagus nerve
2. Sympathetic = T10-T12
What innervates the hindgut?
- Parasympathetic = Pelvic (splanchnic) nerves (S2-4)
2. Sympathetic = L1-L3
What is the purpose of enteric ganglia?
Ganglia located within the walls of the gut tube
Goal in life of sympathetics are to synapse here
What is the significance of the sympathetic innervation of the gut tube?
Visceral pain will be referred to the T1-L3 dermatomes
Pain from abdominal viscera is carried back to the CNS by sympathetic nerves and is referred to dermatomes of the body wall that match the sympathetic innervation
Pain is POORLY LOCALIZED
Where is pain of the umbilicus referred to?
Small intestine
What is the referred pain to appendix?
T10
McBurney’s point
What is secondarily retroperitoneal?
- pancreas
- duodenum
- ascending colon
- descending colon
Significant for imaging
What are some synonyms for ventral mesentery remnant?
Omentum
Where does esophagus begin?
C6
Cervical Constriction
Cricopharyngeus muscle
Narrowing of the esophagus
Where is the level of the thoracic constriction of the diaphragm?
T4
There the bronchus bifurcates
Where aortic arch is
Where is the level of diaphragmatic constriction?
T10
Caused by lower sphincter
Where are the three significant constrictions /narrowings of the esophagus?
- Cervical
- Thoracic
- aortic arch
- left atrium/left mainstem bronchus
- Diphragmatic
What is the muscle makeup of the esophagus?
- Upper 5% = voluntary skeletal muscle
- Middle 45%
- mixture of skeletal and mostly SMOOTH
- Distal 50%
- involuntary smooth muscle
What innervates all the muscles of the esophagus?
Smooth and skeletal all by the vagus nerve
What is the role of the stomach?
Food blender
Food reservoir
Holds 2-3 L of food
What are the glandular regions of the stomach?
- cardiac
- fundus
- ANTRUM (pylorus?)
HISTOLOGICAL
What are the anatomic divisions?
- Cardiac
- fundus
- body
- pylorus
What is important about epiploic foramen?
It is where the vasculature and lymphatics pass through
What are the muscle layers in the stomach?
- Outer longitudinal
- Middle circular
- Innermost oblique
What are the rugae?
Folds in the stomach
What is the Z line?
The line separating esophagus to stomach
Juncture where epithelial change is evident (from esophagus to stomach)
T11
What is the squamo-colunar junction of esophagus?
Right above the Zline
Site of physiologic inferior esophageal sphincter
What will be found in the omental bursa (lesser sac)?
Pancreas and duodenum
What are the three branches of the celiac trunk?
- common hepatic artery
- splenic artery
- left gastric artery
What is the portal triad?
- common bile duct
- common hepatic artery
- portal vein
What supplies the lesser curvature of the stomach?
- left gastric artery (from celica trunk
- right gastric artery from hepatic artery?
Dual blood supply
What supplies the greater curvature of the stomach?
- Right gastroepiploic artery (gastroduodenal artery))
- Left gastroepiploic artery (splenic artery)
- Short gastric artery
Dual blood supply
Where does the left vagus nerve end up?
Anterior vagal trunk
Where does right vagus nerve end up?
Posterior vagal trunk
Where do the bile and pancreatic secretions drain into?
The 2nd part of the duodenal at the MAJOR DUODENAL PAPILLA (Vater?)
What are the key characteristics of the jejunum?
It is much more rugged and has much more curves
What are the key characteristics of the ileum?
Smoother
Peyer’s patches
What is the blood supply of jejunum?
- simple arcades
2. Long vasa recta
What is the blood supply of the ileum?
- Complex arcades
2. Short vasa recta
What are the key characteristics of the colon?
- Taenia coli (the longitudinal strip of muscle in the colon)
- Haustra (which are the bumps you see in the colon)
- Fat droplets that are seen around colon
What are the divisions of the SMA?
- ileocolic artery
- Right colic artery
- Middle colic artery
All have ascending and descending branches
What are the marginal arteries?
The ascending and descending branches of the 3 main divisions of the SMA
What are the divisions of the IMA?
- Left colic artery
- Sigmoid arteries
- Superior rectal artery
Where are the marginal arteries the weakest?
At the 2/3 junction of transverse junction
