Anatomy Topic 4 Case 4 Flashcards
How long is the small intestine?
- 6 to 7 m
How long is the duodenum?
- 20 to 25 cm
Is the duodenum retroperitoneal or intraperitoneal?
- Retroperitoneal
- Except for the first part which is connected to the liver by the hepatoduodenal ligament
Identify the four parts of the duodenum
- Superior
- Descending
- Inferior
- Ascending
At what vertebral level is the superior part of the duodenum?
- To the right of L1
The superior part of the duodenum passes anteriorly over which structures?
- Bile duct
- Gastroduodenal artery
- Portal vein
- Inferior vena cava
What is the clinical significance of the superior part of the duodenum?
- Ampulla
- The point of the duodenum at which ulcers are most likely to occur
At what vertebral level does the descending part of the duodenum reach?
- To the right of L3
Identify the structure that passes anterior and the structure that passes posterior to the descending part of the duodenum
- Anterior: Transverse colon
- Posterior: Right kidney
Identify two features of the descending part of the duodenum
- Major duodenal papilla
- Minor duodenal papilla
Identify a structure that passes anterior to the inferior part of the duodenum
- Superior mesenteric artery and vein
At what vertebral level does the ascending part of the duodenum reach?
- To left of L2
What is the duodenojejunal flexure? Identify one feature of it
- Point at which duodenum terminates
- Surrounded by a fold of peritoneum containing muscle fibres
- Called the suspensory muscle of duodenum (ligament of Treitz)
Outline the arterial supply to the duodenum
- Gastroduodenal artery (from common hepatic artery)
- Supraduodenal artery (from gastroduodenal artery)
- Anterior + posterior superior pancreaticoduodenal arteries (from gastroduodenal artery)
- Anterior + posterior inferior pancreaticoduodenal arteries (from inferior pancreaticoduodenal artery from superior mesenteric artery)
- First jejunal branch of superior mesenteric artery
Describe the venous drainage of the duodenum
- Superior pancreaticoduodenal veins drain into portal vein
- Inferior pancreaticoduodenal veins drain into superior mesenteric vein
Describe the lymphatic drainage of the duodenum
- Drains upward via pancreaticoduodenal nodes to gastroduodenal nodes into coeliac nodes
- Drains downward via pancreaticoduodenal nodes to superior mesenteric nodes
Outline the innervation of the duodenum
- Sympathetic and parasympathetic innervation from coeliac and superior mesenteric plexuses
Describe features of the jejunum
- Proximal 2/5
- In left upper quadrant
- Fewer arterial arcades
- Longer vasa recta
- Less mesenteric fat
- More prominent plicae circulares
Describe features of the ileum
- Distal 3/5
- In lower right quadrant
- More arterial arcades
- Shorter vasa recta
- More mesenteric fat
- Less prominent plicae circulares
Identify the arterial supply of the jejunum and ileum
- Jejunal and ileal branches of superior mesenteric artery
- Ileum also supplied by ileal branch of ileocolic artery
With regards to Meckel’s diverticulum identify its:
- Pathology
- Epidemiology
- Clinical features
- Treatment
- Remnant of the yolk sac that lies on the antimesenteric border of the ileum
- 2% of patients
- Haemorrhage, diverticulitis, ulceration, obstruction
- Surgical removal laparoscopically
Describe the features of the mucosa of the duodenum
- Long villi interspersed with crypts of Lieberkuhn
- Brunner’s glands open into muscularis mucosae
Describe the features of the mucosa of the ileum
- Transverse folds (plicae circulares) covered with short villi
- Peyer’s patches
How does the distribution of plicae circulares change through the small intestine
- Most prominent in jejunum and proximal ileum
- Absent in proximal duodenum and distal ileum
What type of epithelium lines the crypts of Lieberkuhn?
- Simple columnar epithelium
Identify 5 cell types that line the crypts of Lieberkuhn and their function
- Enterocytes: Absorption
- Goblet cells: Mucus production
- Paneth cells: Defensive function (eosinophilic granules
- Neuroendocrine cells: Motility (hormones)
- Stem cells: Replenish all of the above cells
Identify two features of enterocytes that protect the small intestine from auto-digestion
- Goblet-cell derived mucus
- Glycocalyx
What is responsible for absorption of pancreatic enzymes from small intestine?
- Glycocalyx
Where are lacteals located and what is their role?
- Run through centre of villi
- Drain tiny lymphatic vessels
- Transport absorbed lipid into circulatory system via lymphatic duct
Describe two additional protective mechanisms of the small intestine
- T lymphocytes are scattered among enterocytes
- Plasma cells secrete IgA
How long is the large intestine?
- 1.5 m
Identify four characteristics of the large intestine
- Larger diameter than small intestine
- Peritoneal-covered accumulations of fat (omental appendices)
- Segregation of longitudinal muscle into three narrow bands (taeniae coli)
- Sacculations known as haustrations
In which abdominal region is the cecum located?
- Right iliac fossa
Is the cecum intraperitoneal or retroperitoneal?
- Intraperitoneal
- Because of its mobility not because of its suspension by mesentery
What is the appendix?
- Narrow, hollow, blind-ended tube connected to the cecum
Identify two functions of the mesoappendix
- Suspends appendix form terminal ileum
- Contains appendicular vessels
Identify four possible locations of the appendix
- Retrocecal
- Retrocolic
- Subcecal
- Preileal
- Postileal
Identify the surface projection of the appendix
- One third the distance from the ASIL to the umbilicus
Identify the arterial supply to the cecum and appendix
- Anterior cecal artery
- Posterior cecal artery
- Appendicular artery
- All of which are from the ileocolic artery
- A branch of the superior mesenteric artery
Identify the pathology of appendicitis
- Obstruction from fecalith or enlargement of lymphoid nodules
- Causing proliferation of bacteria
- Resulting in invasion of appendix wall, which becomes damaged by pressure necrosis
Outline the clinical features of appendicitis
- Periumbilical pain that becomes localised to right iliac fossa
- Associated with fever, vomiting and nausea
Outline the investigation and treatment of appendicitis
- Ultrasound scan
- Appendectomy
Identify the parts of the colon
- Ascending colon
- Hepatic flexure
- Transverse colon
- Splenic flexure
- Descending colon
- Sigmoid colon
What are the paracolic gutters?
- Formed between lateral margins of ascending and descending colon and posterolateral abdominal wall
- Through which material can pass through peritoneal cavity
- Which is free of vessels and lymphatics allowing for mobilisation of the ascending and descending colons
To which vertebral level does the sigmoid colon descend to?
- S3
Identify the arterial supply to the ascending colon
- Colic branch from ileocolic artery
- Anterior cecal artery
- Posterior cecal artery
- Right colic artery
- All of which arise from the superior mesenteric artery
Identify the arterial supply to the transverse colon
- Right colic artery (SMA)
- Middle colic artery (MSA)
- Left colic artery (IMA)
Identify the arterial supply to the descending colon
- Left colic artery
- From inferior mesenteric artery
Identify the arterial supply to the sigmoidal colon
- Sigmoid arteries
- From inferior mesenteric artery
How is the perineal flexure (anorectal junction) formeD?
- By action of the puborectalis muscle
- So the anal canal moves in a posterior direction as it passes through the pelvic floor
Identify the three lateral curvatures of the
- Upper and lower curvatures on the right
- Middle curvature on the left
What is the rectal ampulla?
- Expanded lower part of the rectum
What are anal columns / columns of Morgagni?
- Longitudinally oriented folds
- Which are united inferiorly by crescentic folds termed anal valves
What is the pectinate line?
- Circle formed around the anal canal by the anal valves
- Marks position of the anal membrane in the foetus
What is the anal pecten?
- Transition line lined by non-keratinised stratified squamous epithelium.
- Ending inferiorly as the anocutaneous line (white line)
Outline the arterial supply to the rectum and anus
- Superior rectal artery (from inferior mesenteric artery)
- Middle rectal artery (from internal iliac artery)
- Inferior rectal artery (from internal pudendal artery from internal iliac artery)
What is the arterial supply to the hindgut?
- Inferior mesenteric artery
At which vertebral level does the inferior mesenteric artery arise?
- L3
Identify the branches of the inferior mesenteric artery
- Left colic artery
- Sigmoid arteries
- Superior rectal artery
Identify the part of the vascular supply of the hindgut that is vulnerable to ischaemia
- Watershed area between superior mesenteric and inferior mesenteric artery at splenic flexure
Which structures are drained by the inferior mesenteric vein?
- Rectum
- Sigmoid colon
- Descending colon
- Splenic flexure
Outline the course of the inferior mesenteric vein
- Beings as superior rectal vein
- Which receives tributaries from sigmoid veins and left colic vein
- It passes posterior to body of pancreas
- To join splenic vein (though it can join superior mesenteric vein)
What are Peyer’s patches?
- Lymphoid tissue
- Found in the mucosa of the ileum and ileocecal junction
Identify the two cell types of the colon and their arrangement
- Absorptive and goblet cells
- Arranged in closely packed straight tubular glands
- Which extend down to muscularis mucosae
What fills the space between the glands of the large intestine?
- Lamina propria
- Containing blood vessels into which water is absorbed
Outline the defence mechanisms of the colon
- Lamina propria contains collagen, lymphocytes (lymphoid aggregates) and plasma cells
How does the mucosa of the rectum differ to that of the rest of the colon?
- Contains more goblet cells
Identify the epithelial transitions through the rectum and anus
- Columnar (colon and rectum) to stratified squamous epithelia from the anorectal junction
Identify the two haemorrhoidal plexuses of the anus
- Internal plexus in the submucosa above the pectinate line
- External plexus in the submucosa between the anal canal and perianal skin
Which artery supplies the midgut?
- Superior mesenteric artery
At which vertebral level is the superior mesenteric artery located?
- Lower part of L1
What crosses the anterior surface of the superior mesenteric artery?
- Splenic vein
- Neck of pancreas
What crosses the posterior surface of the superior mesenteric artery?
- Left renal vein
- Uncinate process
- Inferior part of duodenum
Identify the branches of the superior mesenteric artery
- Inferior pancreaticoduodenal artery
- Jejunal arteries
- Ileal arteries
- Ileocolic artery
- Right colic artery
- Middle colic artery
What do the jejunal and ileal arteries pass through?
- Mesentery
- Forming arcades as they pass outward to supply the small intestine
What does the middle colic artery pass through?
- Transverse mesocolon where it divides into left and right branches
