GI Anatomy Flashcards
What are aponeuroses?
Sheets of tendon (take place of a tendon in flat muscles, forms the abdominal wall)
Which muscles form the abdominal wall and what is their direction?
Rectus abdominis
Vertical
Name the 3 layers of muscle that lie lateral to the rectus sheath, and give the direction of fibres.
External oblique (diagonally down and in) Internal oblique (diagonally up and in Transversus abdominis (transversely)
From which muscle’s aponeuroses is the inguinal ligament formed?
External oblique (Aponeuroses are sheets of tendon)
Name the 9 anatomical regions of the abdomen.
Central (top to bottom): epigastric, umbilical, hypogastric/suprapubic
Lateral (top to bottom): hypochondrial, lumbar, iliac
What is McBurney’s point?
Usual site of the base of the appendix
What are the contents of the rectus sheath?
Rectus abdominis and pyramidalis muscles.
It is formed by the aponeuroses of the internal & external obliques, and the transversus abdominis muscles.
Which embryological structure forms the ligamentum teres?
Umbilical vein (Ligamentum teres = round ligament of the liver)
Which artery supplies the foregut?
Coeliac trunk
What is the foregut?
Mouth –> duodenum
Which nerves supply the foregut?
Greater Splanchnic Nerve (T5-T9, sympathetic) and vagal trunks (CN 10, para-sympathetic)
What are the four main areas of the stomach?
Cardia (level T11)
Fundus (often gas-filled)
Body
Pylorus
Describe the anatomy and function of the greater omentum.
Hangs from the greater curvature of the stomach, folds back on itself and attaches to the transverse colon.
Contains many lymph nodes and may adhere to inflamed areas.
Therefore minimises spread of intraperitoneal infections.
What is the venous drainage of the stomach?
Right and left gastric veins drain into the hepatic portal vein
Anatomically, what are the 3 parts of the small intestine?
Duodenum, jejunum, ileum
What are the four parts of the duodenum?
Superior, descending, inferior, ascending
- form ‘C’ shape which wraps around the head of the pancreas
- 25cm long
Where do duodenal ulcers most commonly occur and what are the most common causes?
Superior duodenum
Helicobacter pylori infection and long-term NSAIDs
What is the arterial supply of the duodenum?
Gastroduodenal artery (branch of coeliac trunk) Inferior pancreaticoduodenal artery (branch of superior mesenteric) - the change of blood supply marks the change from the embryological foregut to the midgut
What is the arterial supply of the jejunum and ileus?
Superior mesenteric artery (arises from aorta at L1)
How are the vasa recta formed?
Superior mesenteric artery splits into approx. 20 branches.
Branches anastomose to form loops called arcades.
From the arcades long and straight arteries arise called vasa recta.
What are the four anatomical parts of the large intestine?
Ascending, transverse, descending, sigmoid (40cm)
- total length = 150cm
Describe the anatomy of the hepatic and splenic flexures.
Hepatic flexure = where the ascending colon turns 90 degrees to move horizontally and start the transverse colon (occurs when large bowel meets right lobe of liver)
Splenic flexure = where transverse colon turns 90 degrees to move inferiorly and start the descending colon (occurs when large bowel meets the spleen)
Embryologically divide up the colon.
Ascending colon and proximal 2/3 of transverse colon are derived from the midgut.
Distal 1/3 of the transverse colon, descending and sigmoid are derived from the hindgut.
Of the foregut, midgut and hindgut, which does the superior mesenteric artery generally supply?
Midgut-derived structures
Of the foregut, midgut and hindgut, which does the inferior mesenteric artery generally supply?
Hindgut-derived structures
Which nerve plexus supplies sympathetic, parasympathetic and sensory innervation to midgut-derived structures? (ascending colon and proximal 2/3 of transverse colon)
Superior mesenteric plexus
Which nerve plexus supplies sympathetic, parasympathetic and sensory innervation to hindgut-derived structures? (distal 1/3 of the transverse colon, descending and sigmoid)
Inferior mesenteric plexus
- parasympathetic = pelvic splanchnic nerves
- sympathetic = lumbar splanchnic nerves
The superior aspect of the anal canal has the same epithelial lining as the rectum, what is this?
Columnar epithelium
Which line separates the anal canal into upper and lower parts?
Dendate/pectinate line
What is the gut above the dendate line embryologically derived from?
Embryological hindgut
What is the gut below the dendate line embryologically derived from?
Ectoderm of the proctodeum
What epithelium lines the anal canal below the pectinate line?
Non-keratinised stratified squamous epithelium
What is the arterial supply of the anal canal above the dendate line?
Superior rectal artery (branch of inferior mesenteric)
What is the arterial supply of the anal canal below the dendate line?
Inferior rectal artery (branch of internal pudendal artery)
