Chapter 5 - Small Intestines Flashcards
Extent and length of SI
From pylorus to ileoceacal junction
6m long
Longer in males
Divisions of SI
- Upper fixed duodenum
- Lower mobile tube
- upper 2/5 - jejunum
- lower 3/5 - ileum
Large surface area of SI by
- Length
- Circular mucous folds
- Villi
- Microvilli
Circular mucous folds of SI
- called plicae circulares or valves of Kerckring
- form complete or incomplete circles
- folds are permanent
- begin in 2nd part of duodenum
- become large and closely set below level of duodenal papilla and through jejunum
- diminish in size and no. in distal jejunum and proximal ileum
- absent in distal ileum
Facilitate absorption by slowing down passage of contents
Intestinal villi
- finger like projections of mucous membrane
- large and many in duodenum and jejunum
- small and few in ileum
- inc. surface area by 8 times
- villi covered by absorptive columnar cells
- Columnar cells have microvilli
Intestinal glands of SI
- tubular glands
- on mucous membranes of jejunum and ileum
- open by circular apertures between villi
- epithelial cells in crypts show high mitotic activity
- proliferated cells move to surface and shed from tips of villi
- complete epithelial lining of villi replaced every 2-4 days
Brunners glands in submucosa - compound tubuloacinar glands - secrete mucous
Lymphatic follicles of SI
2 types - solitary and aggregated
-Solitary - 1-2mm in dia
-Aggregated - Peyers patches - 2-10cm - max in ileum
Both are numerous at puberty, diminish later
Peyers patches ulcerated in typhoid fever
Arterial supply of SI
Jejunum and ileum - jejunal and ileal branches of superior mesenteric A
Nerve supply of SI
Symp - T9-T11
Parasymp - Vagus
Both pass through coeliac and superior mesenteric plexuses
- Myenteric plexus and submucosal plexus has parasymp. ganglia
- Symp. nerves are motor to sphincters and muscularis mucosae and inhibitory to peristalsis
- Parasymp. stimulate peristalsis and inhibit sphincters
Location of duodenum
Shortest, Widest, Most fixed part of SI
- from pylorus to duodenojejunal flexure
- curves around head of pancreas to form C
- above level of umbilicus
- opp L1, L2, L3 vertebrae
Parts of duodenum
- Superior - 2in.
- Descending - 3in.
- Horizontal - 4in.
- Ascending - 1in.
Location of 1st part of duodenum
- Starts at pylorus
- passes back, up, right to meet 2nd part
Peritoneal relations of 1st part of duodenum
Proximal 2.5cm
- movable
- attached to greater omentum above, lesser omentum below
Distal 2.5cm
- fixed
- retroperitoneal. peritoneum only on anterior side
Visceral relations of 1st part of duodenum
Ant: Quadrate lobe of liver, Gallbladder
Post: Gastroduodenal A, Bile duct, Portal V
Sup: Epiploic foramen
Inf: Pancreas
Location of 2nd part of duodenum
- starts at superior duodenal flexure
- passes down
- reaches L3
- curves to left at inf. duodenal flexure
Peritoneal relations of 2nd part of duodenum
Retroperitoneal and fixed
Anterior relations of 2nd part of duodenum
- Liver
- Transverse colon
- Transverse mesocolon
- SI
Posterior relations of 2nd part of duodenum
- Right kidney
- Right renal vessels
- Right edge of IVC
- Right psoas major
Medial relations of 2nd part of duodenum
- Pancreas head
2. Bile duct
Lateral relations of 2nd part of duodenum
Right colic flexure
Features of interior of 2nd part of duodenum
- Major duodenal papilla: hepatopancreatic ampulla opens at summit of papilla
- Minor duodenal papilla: opening of accessory pancreatic duct
- Below major duodenal papilla, longitudinal fold called plica longitudinalis is seen
Course of 3rd part of duodenum
- from inf. duodenal flexure
- passes horizontally in front of IVC
- joins 4th part in front of abdominal aorta
Peritoneal relations of 3rd part of duodenum
Retroperitoneal and fixed
Crossed by superior mesenteric vessels in median plane
Anterior relations of 3rd part of duodenum
- Superior mesenteric vessels
2. Root of mesentery
Posterior relations of 3rd part of duodenum
- Right ureter
- Right psoas major
- Right testicular/ovarian vessels
- IVC
- Abdominal aorta
Superior relations of 3rd part of duodenum
- Head of pancreas
2. Uncinate process
Inferior relations of 3rd part of duodenum
Jejunum
Course of 4th part of duodenum
Runs up till L2
Turns forward becomes cont. with jejunum at duodenojejunal flexure
Peritoneal relations of 4th part of duodenum
Retroperitoneal
Terminal part is mobile
Anterior relations of 4th part of duodenum
- Transverse colon
- Transverse mesocolon
- Lesser sac
- Stomach
Posterior relations of 4th part of duodenum
- Left sympathetic chain
- Left renal A
- Left gonadal A
- Inf. mesenteric V
Side relations of 4th part of duodenum
Right: Root of mesentery
Left: Left kidney and ureter
Sup: Body of pancreas
Suspensory Ligament of Duodenum
Ligament of Treitz
- fibromuscular band
- suspends and supports duodenojejunal flexure
- arises from right crus of diaphragm
- attaches to post. surface of duodenojejunal flexure and part 3 and 4 of duodenum
Made of:
- Striped muscles in upper part
- Elastic M in middle
- Smooth M in lower
Its contraction inc. angle to DDJ flexure
Arterial supply of duodenum
Upto opening of bile duct - from foregut - superior pancreaticoduodenal A
After opening - from midgut - inferior pancreaticoduodenal A
1st part addiotionally from:
1. Right gastric A
2. Supraduodenal A of Wilkie
3. Gastroduodenal A
4. b. of Right gastroepiploic A
Venous drainage of duodenum
Drain into:
Splenic
Superior mesenteric
Portal V
Lymphatic drainage of duodenum
Pancreaticoduodenal nodes
Hepatic nodes
Coeliac nodes
Nerve supply of duodenum
Sympathetic - T9-T10
Parasymp - Vagus through Coeliac plexus
Blood supply of jejunum and ileum
Superior mesenteric A and V
Nerve Supply of jejunum and ileum
Sym - T9-T11
Parasym - Vagus
Things that differentiate jejunum from ileum
Jejunum has:
- Thicker, more vascular walls
- Wider lumen
- Lesser fat in mesentery
- Longer and fewer vasa recta
- Large, closely set circular mucosal folds
- More abundant villi
- Fewer lymph follicles
Meckel’s diverticulum
- Persistant proximal part of vitellointestinal duct.
- Normally disappears during 6th wk of IUL
- 2in long
- Situated close to ileocaecal valve, attached to antimesenteric border of ileum
- Apex may be free or attached to other structures
