GIT Anatomy Flashcards
What makes up the foregut?
Distal 3rd of esophagus to the 2nd part of the duodenum at the entrance of the bile duct (Major duodenal papilla - where ampulla of vater opens through)
What makes up the midgut?
2nd part of the duodenum to proximal 2/3rd transverse colon
What makes up the hindgut?
Distal 1/3rd of transverse colon to the rectum
What are the 9 regions of the abdomen?
R & L hypochondrium, epigastric
R &L flank, umbilical
R & L groin, pubic (hypogastric)
What are the planes?
Transpyloric L1
Subcostal L3
Intertubercular L5
Abdominal wall fascia from surface to deep?
- Skin
- Superficial fascia
1. Camper fascia
2. Scarpa fascia - Investing fascia
1. Superficial > External oblique muscle
2. Intermediate > Internal oblique muscle
3. Deep > Transverse abdominis muscle - [Deep] Transversalis fascia
- Extraperitoneal fat
- Parietal peritoneum
Above umbilicus of rectus sheath?
- Internal oblique aponeurosis split and encloses the rectus abdominis
- External oblique aponeurosis is in front RA
- Transversus abdominis behind RA
Below umbilicus of rectus sheath
all 3 layers anterior to rectus muscle
Arcuate line?
- Anterior wall is complete
- Posterior wall is incomplete. Stops short below umbilicus at arcuate line
- Below arcuate line, rectus abdominis in contact with transversalis fascia
- Arcuate line demarcates the transition between Posterior wall cover superior 3 quarters of rectus abdominis & transversalis fascia cover inferior quarter
How is conjoint tendon formed?
Lowest fibres of internal oblique and transverse abdominis join to form the Conjoint tendon
How is superficial inguinal ring formed?
Aponeurosis of external oblique fuses medially with rectus sheath to form superficial inguinal ring (hole in EOA)
How is inguinal ligament formed?
Lower external oblique aponeurotic edge curls under to form inguinal ligament
Where does neurovascular plane lie?
between internal oblique & transversus abdominis
Arterial supply of rectus abdominis?
- 2 vessels enter rectus sheath & anastomose → possible by-pass to abdominal aorta
- Superior epigastric* (from internal mammary thoracic)
- Inferior epigastric* (from external iliac)
- These arteries are posterior to rectus abdominis, but within rectus sheath
Dermatomes?
- T7-T9 – epigastrium
- T10 – umbilicus
- T11-12 – inferior to the umbilicus
- L1 (IlioHypogastric N, IlioInguinal N) – inguinal & pubis
Whats the inguinal canal?
Groin between ASIS (anterior superior iliac spine) & pubic tubercle
from Deep Inguinal Ring to Superficial Inguinal Ring
DIR vs SIR?
DIR : hole in transversalis fascia
SIR : hole in EOA
Difference in contents in inguinal canal between male & female?
Male : spermatic cord
Female : round ligament
4 walls of inguinal canal - 2 MALT
- [Roof]
2Muscles:Transversus abdominis,internal oblique - [Anterior wall]
2Aponeuroses:Internal obliqueaponeurosis,external obliqueaponeurosis
3.[Floor]
2Ligaments:Inguinalligament,lacunarligament - [Posterior wall]
2Tendon:Conjoint tendon medially,Transversalisfascia laterally
Mid-inguinal point VS Mid-point of inguinal ligament?
Mid-inguinal : half-way between ASIS & pubic symphysis
- Femoral artery in groin
Mid-point : between ASIS & pubic tubercle
- DIR
- indirect inguinal hernias
4 types of hernias?
- Reducible → sac returns to containing cavity
- Irreducible → can’t be returned to containing cavity
- Obstructed → contains blocked bowel
- Strangulated → contents with a compromised blood supply → possible gangrene
Factors that prevent occurrence of hernia?
- Oblique passage
- Posterior wall (immediately behind the superficial inguinal ring) is reinforced by the conjoint tendon
- When intra-abdominal pressure is increased on coughing and straining, the roof compresses the contents of the canal against the floor, so that the canal is completely closed (contents cannot be herniated!)
Direct vs indirect (inguinal) hernia?
Landmark to differentiate : Inferior epigastric artery
medial to IEA - direct
lateral to IEA - indirect
inguinal vs femoral hernia?
femoral : below & lateral to public tubercle.
VS inguinal : above & medial
Branches of abdominal aorta
Celiac trunk T12
SMA L1
IMA L3
Branches of celiac trunk
- Left gastric
- Common hepatic -> right gastro-omental, right gastric, superior pancreaticoduodenal
- Splenic -> left gastro-omental, short gastric
Portal-Systemic anastomoses [PSA] (4 sites)
A. Lower esophagus
- Left gastric (P)
- Esophageal (S)
B. Rectum
- Superior rectal (P)
- Inferior rectal (S)
C. Umbilicus
- Paraumbilical (P)
- Epigastric -> Ext. iliac (S)
D. Posterior abdominal wall
- Visceral (P)
- Retroperitoneal (S)
Peritoneum of males vs females
Males : completely closed
Females : incompletely closed - potential pathway for infection
Where is the lesser & greater omentum?
L : between liver & lesser curvature of stomach
G : between greater curvature & tranverse colon
Where does portal triad run?
Portal triad : portal vein, hepatic artery, bile duct
Near free edge of lesser omentum
2 ligaments of lesser omentum? & greater?
L :
Hepatogastric
Hepatoduodenal
G;
Gastrophrenic
Gastrosplenic
Whats omental foramen?
Lesser sac & greater sac communicate through omental foramen
How is greater sac divided?
Divided by Transverse mesocolon into :
1. Supracolic compartment (Above TM)
- Liver, Stomach, Pancreas, Spleen
- Infracolic compartment (Below TM)
- Small intestines, Colon
Boundaries of lesser sac? (omental bursa)
- anterior : stomach & lesser omentum
- superior : diaphragm
- inferior : layers of greater omentum
- left margin formed by spleen
Boundaries of omental foramen / foramen of Winslow
- Anterior: bile duct, hepatic artery & portal vein [portal triad]
- Posterior: IVC & diaphragm
- Superior: caudate lobe of the liver
- Inferior: first part of the duodenum
What organs are INTRAperitoneal?
Stomach
Liver
Spleen
Pancreas (tail)
Duodenum (1st part)
Ileum, Jejunum
Colon (cecum, transverse, sigmoid)
What organs are RETROperitoneal
Duodenum (2nd-4th part)
Pancreas (head, body, neck)
Colon (ascending, descending)
Kidneys, great vessels, oesophagus, rectum
2 orifices of stomach?
Cardiac (gastroesophageal junction)
Pyloric (gastroduodenal junctin)
Impt posterior relations of stomach from superior to inferior?
- Spleen
- Left suprarenal gland
- Splenic artery
- Pancreas
- Tr colon
- Kidney
Arterial supply of stomach?
Lesser curvature
- Left gastric & right gastric (common hepatic) anastomoses
Greater curvature
- Right gastro-omental (common hepatic) & Left gastro-omental (splenic) anastomoses
Fundus & upper part of greater curvature
- Short gastric (splenic)
Sympathetic innervation of stomach?
from t5-t9 spinal segments
Recesses & surfaces of liver?
Subphrenic recess, hepatorenal recess
Diaphragmatic & visceral surface
3 Ligaments of liver & attachment
- Falciform ligament → anterior abdominal wall
- Hepatogastric ligament → stomach
- Coronary ligament → Diaphragm
Anatomical vs functional lobes of liver
Anatomical
- divided by falciform ligament
- Right anatomical lobe : Quadrate lobe + Caudate lobe
Functional
- divided by fossae for gall bladder & IVC
- Left functional lobe : Quadrate lobe + Caudate lobe
Where can gallbladder be palpated
Tip of right 9th costal cartilage (around L1)
How is neck of gallbladder connected to common BD?
Cystic duct connects the neck to the common bile duct
Arterial supply of gallbladder?
Cystic artery (right hepatic from common hepatic)
Where is gallbladder referred pain?
- Right phrenic nerve irritated
- Local pain in right hypochondriac area
- Referred pain → Right shoulder / neck
- C3-C5 dermatomes
- EG biliary colic
What makes the bile duct?
- R + L hepatic ducts → common hepatic duct
- common hepatic duct + cystic duct → bile duct
Ampulla of vater?
- BD joins with main pancreatic duct → open into the ampulla of vater in the duodenal wall
- Ampulla of vater opens into the duodenum through major duodenal papilla
Sphincter of Oddi
Ampulla of vater, bile & pancreatic ducts are surrounded by circular muscle → sphincter of Oddi
By parasympathetic innervation
Relations of spleen?
- Anterior : stomach
-
Posterior : T9-11 & Left diaphragm
- Fracture of T9-11 ribs may rupture spleen / sudden increase in intra-abdominal pressure too → Severe intraperitoneal haemorrhage
- Inferior : Left colic flexure
- Medial : Left kidney
- Hilum : (in contact with) Tail of pancreas
Ligaments of spleen & attachments?
- Gastrosplenic ligament → Greater curvature of stomach
- Splenorenal ligament → Left kidney
Where does pancreatic duct open into?
- Main pancreatic duct → ampulla of vater
- Accessory pancreatic duct → duodenum
Relations of pancreas?
-
Head
- attached to descending part of duodenum
- posterior : common bile duct
- tumour in head least likely to compress spleen
-
Neck
- posterior : superior mesentric vessels & splenic vein
- tumour in neck most likely to obstruct portal vein
-
Body
- floor of omental bursa
- anterior : stomach
- posterior : left kidney
-
Tail
- hilum of spleen
-
Uncinate process
- anterior : superior mesentric vessels
Arterial supply of pancreas?
Head :
- Superior / Inferior pancreatico duodenal arteries from gastroduodenal (common hepatic) & SMA respectively
-> Anastomoses
Neck, Body, Tail
- Splenic
Venous drainage of pancreas?
Splenic & portal vein
Referred pain of duodenal ulcer?
if Anterior → Peritonitis (erosion of peritoneum)
Right shoulder (referred) pain if fluid leak into peritoneal cavity & touch diaphragm as phrenic nerve (C3-C5) is irritated
Jejunum vs Ileum
Ileum
1. Thinner walls
2. Longer
3. Prominent arterial arcades
4. Shorter vasa recta
5. Terminal : no plicae circulares
6. Have Peyer’s patches
Arterial supply of jejunum & ileum?
SMA - jejunal arteries & ileal arteries
Terminal ileum : ileocolic artery
Innervation of small intestines?
Sympathetic : greater splanchnic
Parasympathetic : Vagus
Main features of colon?
- Omental appendices
- Omental tenia coli
- Haustra
Innervation of appendix?
Early
- Visceral (diffuse) pain → referred to T10 dermatome (umbilicus)
- sensory fibres accompany sympathetic nerve fibres & reach T10 spinal sensory ganglia
Late
- Sharp pain in right inguinal region
- Swelling of appendix → Touch parietal peritoneum → L1 spinal nerve irritated
- Somatic sensory which supply skin to inguinal region
Innervation of colon
- ascending : right colic (SMA)
- transverse : middle colic (SMA), left colic (IMA)
- descending : left colic (IMA)
- sigmoid : sigmoid (IMA)
anastomosis between right & middle colic. then middle & left colic
Whats the cisterna chyli
- All lymph drains into the cisterna chyli
- cc : an elongated lymphatic sac located in front of the L1 & L2 bodies (transpyloric plane ish)
- Thoracic duct commences from cc
What’s anorectal flexure?
Impt for fecal continence & is maintained during the resting state by the tonus of the puborectalis muscle
+ its active contraction during peristaltic contractions if defecation is not to occur
What’s ampulla of rectum for?
Dilated terminal part, the ampulla of the rectum, supports and retains the fecal mass before it’s expelled during defecation
Arterial supply of rectum?
- Superior rectal artery (from IMA) → proximal part of the rectum
- R & L middle rectal arteries [from the inferior vesical (male) or uterine (female) arteries] → middle & inferior parts of the rectum
- Inferior rectal arteries [from the internal pudendal arteries] → anorectal junction & anal canal
Innervation of rectum
- Rectum above the pelvic pain line : visceral afferent fibers follow the sympathetic fibers to the L1–L2 spinal sensory ganglia
- Sympathetic : lumbar spinal cord, via lumbar splanchnic nerves (L1 – L2)
- Rectum below the pelvic pain line : visceral afferent fibers follow the parasympathetic fibers retrogradely to the S2–S4 spinal sensory ganglia
- Parasympathetic : sacral spinal cord, via the pelvic splanchnic nerves (S2–S4)
Pectinate line ( impt in surgery)
Superior : visceral afferent nerves
- painless
Inferior : somatic sensory
- sensitive
- explains pain after rubber band ligation (treatment for internal hemorrhoids)
Internal vs external hemorrhoids
Internal ->
- inside rectum, above pectinate line.
- bleeding (bright red) but painless
- feeling of incomplete evacuation
External ->
- under skin around anus
- could develop blood clots -> severe pain & swelling
