- 1 Oesophagus
- 2 Stomach
- 3 Spleen
- 4 Small intestine
- 5 Jejunum and ileum
- 6 Vasculature of the jejunum
- 7 Images
This organ is approximately 25cm long and extends from the pharynx to the cardiac portion of the stomach. It begins at the level of the lower border of the cricoid cartilage (CV6) and passes through the diaphragm at TV10. It ends at the level of TV11 in the gastric cardiac orifice. Muscle of the oesophageal wall is striated in the upper 1/3, mixed striated and smooth in the middle 1/3 and smooth in the lower 1/3. The oesophagus is the narrowest part of the GIT and has 4 major constrictions:
- Inferior constrictor muscle:
- at its beginning (CV6), formed by the inferior constrictor of the pharynx
- Aortic arch:
- at the point where it is crossed by the aortic arch, TV4
- Left main bronchus:
- at the left main bronchus, TV5,6
- Oesophageal hiatus
- where it crosses the diaphragm, TV10
These constrictions are important in the passage of instruments down the oesophagus, and also as likely sites of obstruction in the event of oesophageal scarring after swallowing caustic substances.
The oesophagus is divided into 3 parts: cervical, thoracic and abdominal
- A muscular tube
- Hiatus hernia - parts of the stomach go up into the chest; can cause disability: they get reflux from stomach into the oesophagus because the junction has moved up into the chest
- Transmits food from laryngopharynx into the stomach
- Cervical region of oesophagus - from the inferior constrictor of the pharynx down to the level of the first rib
- Thoracic region of oesophagus - runs through the chest
- Abdominal region of oesophagus - after the oesophagus has passed through the diaphragm (at level T10)
- There are several regions where the oesophagus is compressed by outside structures
- Can be important if someone swallows a caustic substance - it is held up at these points in the oesophagus (producing chemical burns to the mucosa of the oesophagus, specifically in this point)
- 1st constriction - due to inferior pharngeal constrictor muscle (CV6)
- 2nd constriction - is at the level of arch of aorta (TV4). This is due to compression from the aorta
- 3rd constriction is caused by the left main bronchus
- Damage at these constrictions produces scar tissue - problems getting food through those points
- 4th constriction is due to the oesophageal hiatus
- The sphincter between the stomach and the oesophagus is not a true sphincter - what really keeps food down is that the abdominal part of the oesophagus is squeezed shut by abdominal pressure. If the cardiooesophageal junction is elevated above the diaphragm, this mechanism no longer works, so you get reflux
- Cardiooesopageal junction aka gastrooesophageal junction
This is the most dilated part of the GIT with a capacity in adult life of about 1500 mL. It has two surfaces (anterior and posterior), two borders or curvatures (greater and lesser curvature), and two openings (cardiac and pyloric).
Several parts are described:
- Cardiac part - with the cardiac orifice situated to the left of the midline behind the 7th costal cartilage, 2.5 cm from its sternal junction at the level of TV11
- Fundus - that part of the stomach above the level of the cardiac orifice, separated from the cardiac part by the cardiac notch or incisure
- Body - being the greater part of the stomach
- Lesser and greater curvatures:
- Lesser curvature (right border) - bearing the attachment of the lesser omentum and the angular incisure at its most dependent part
- greater curvature gives attachment to the greater omentum and gastrosplenic ligament
- Pyloric part:
- The pyloric antrum, to the right of the angular incisure, leading into the narrower and thick walled pyloric canal, with pyloric orifice. The latter is surrounded by the pyloric sphincter, formed of circumferentially arranged smooth muscle. The pyloric orifice is often marked externally by a circular pyloric constriction and often has a prepyloric vein crossing its anterior surface vertically. The pyloric orifice lies about 1.2 cm to the right of the midline in the transpyloric plane (LV1) when the stomach is empty and the patient supine
- Mechanical digestion - churning of ingested food
- Chemical digestion - hydrochloric acid (parietal oxyntic cells)
- Enzymatic digestion - proteolytic pepsin (chief cells)
- At the top we see the cardiooesophageal junction
- The stomach is a large bag, and sometimes the bag is very small, sometimes it is very big (300mL to 3L)
- When it expands, the mucosa stretches out
- A contracted stomach, the mucosa forms ridges (rugae)
- Muscularis externa of the stomach is very thick (powerful muscle wall for contracting/churning food). This is all smooth muscle
- The next part of the gut beyond the stomach is the duodenal cap (leading into the small intestine)
- We divide the stomach into different regions via their notches:
- Cardiac notch
- Angular incisure
- Lesser curvature (to the right of patient), and greater curvate (left side of patient)
- These curvatures have mesenteric attachments (lesser omentum (2 ligs connecting stomach to liver) and greater omentum (large fatty apron hanging in front of every other organ in the abdomen)).
- Rugae are folds of the mucosa that are in a relatively contracted stomach
- Upper part of the stomach is called the fundus, at the level of the cardiac notch (can collect gas, if you percuss the fundus of the stomach you can sometimes hear it).
- Body is beneath the fundus, down to the angular incisure
- Everything to the patient's right of the angular incisure is called the pylorus of the stomach
- We divide the pylorus into:
- Antrum (initial region, quite wide)
- Pyloric canal (a narrow canal)
- Prepyloric vein sits in front of the pyloric sphincter
- Pyloric constriction marks the position of the pyloric sphincer - where the stomach opens into the duodenum
- The initial part of the duodenum is called the duodenal cap
- Clinical importance of relations of the stomach
- Stomach tumours can penetrate these relations
Relations of the anterosuperior surface
- Left costal margin
- Left dome of the diaphragm
- Gastric surface of the spleen
- Left and quadrate lobes of the liver
- Anterior abdominal wall
- Transverse colon
- Liver removed, anterior view
- Immediate anterior relations include the liver (removed), anterior abdominal wall and sometimes the transverse colon (if it's very high)
- Gastric ulcers (acid, bacteria, undigested food) can cause chemical/bacterial peritonitis (greater sac)
Relations of the posteroinferior surface (stomach bed)
- Diaphragm (Lt crus)
- Lt suprarenal gland
- Upper pole of Lt kidney
- Splenic a.
- Anterior pancreatic surface
- Lt colic flexure
- Transverse mesocolon
- Posterior surface of the stomach
- Lesser sac
- Spleen, kidney, diaphragm, pancreas, mesenteric folds (transverse mesocolon)
- Orientation - IVC, diaphragm, abdominal oesophagus, pyloric orifice
- Left suprarenal gland
- Left kidney
- Splenic artery (can bleed to death quickly)
- Splenic vein
- Left colic flexure
- Transverse colon (sometimes; quite mobile, can move in front or behind)
- Duodenum (4th part of duodenum can come up behind the stomach as well)
- Transverse mesocolon
Longitudinal mucosal folds, known as rugae, are seen leading from high in the body to the pyloric antrum and canal.
Muscular layers of teh stomach:
- Unlike other parts of the gut, arranged in 3 layers
- Inner oblique layer
- Middle circular layer
- Outer longitudinal layer
Arterial supply of the stomach
As the stomach is derived from the foregut, it is supplied by branches of the foregut artery, the coeliac a. or trunk. Note the following a's:
- Lt gastric a.
- Br of the coeliac trunk
- Supplying the lesser curvature
- Rt gastric a.
- Br of the common hepatic a.
- Supplying the lesser curvature
- Lt gastro-epiploic a. (or Lt gastro-omental a.)
- Br of the splenic a.
- Supplying the greater curvature
- Rt gastro-epiploic a. (or Rt gastro-omental a.)
- Br of the common hepatic a.
- Supplying the greater curvature
- Short gastric a. (or arteries)
- From the splenic a.
- Supplying the fundus and far left greater curvature
Note: The pyloric shpincter is supplied by the gastric and pyloric a's (rami of the Rt gastric and gastro-epiploic a's).
- The stomach is supplied by a series of arteries which are all branches of the coeliac trunk
- The coeliac trunk provides branches to all the structures derived from the embryonic foregut (see BGDB/Lectures/GIT development
- Arteries are organised along the lesser curvature, and also along the greater curvature
- Left gastric artery (upper part of lesser curvature) - directly from the coeliac trunk
- Right gastric artery (lower part of lesser curvature) - from common hepatic a from coeliac trunk
- Right gastroepiploic a (from gastroduodenal a - supplies upper part of duodenum) - lower part of greater curvature (sometimes used for heart bypass)
- Lt gastroepiploic a (from splenic a) - middle part of greater curvature
- Short gastric a (from splenic a) - upper part of greater curvature
The spleen is situated in the left upper abdomen between the gastric fundus and the diaphragm. Its long axis lies along the 10th rib, its short axis extending from teh 9th to the 11th ribs. its normal dimensions are: 12 cm long, 8 cm wide and 3.5 cm thick and it usually weighs 150 g in adults. Its anterior end usually does not extend anterior to the midaxillary line. The superior border is usually notched (important orientation point).
The spleen has diaphragmatic and visceral surfaces. The diaphragmatic surface is convex and smooth and is related to the abdominal surface of the diaphragm. The visceral surface has 4 impressions:
- Gastric impression: for the fundus and posterior aspect of the stomach
- Renal impression: lowest and posterior impression and separated from the gastric impression by a ridge. It is related to the Lt kidney
- Colic impression: anteriorly and related to the Lt colic flexure
- Pancreatic impression: not always present, situated between the colic impression and lateral part of the hilum.
The spleen is connected to the posterior abdominal wall by the lienorenal ligament (or the splenorenal ligament) and the stomach by the gastrosplenic ligament.
- A lymphoid organ found in the left side of the abdomen. Develops in conjunction with the gut. Has a very close anatomical relation to the gut
- Splenic artery is tortuous, runs along the pancreas out to the spleen, gives some branches to the stomach
- Outer surface is convex, in contact of left dome of diaphragm; inner surface (patient's right) has concave areas related to various organs
- His diagram shows the medial surface of the spleen
Relations of the spleen:
- Gastric impression (fundus)
- Renal impression
- Colic impression (Lt colic flexure)
- Hilum region (splenic arteries and veins; in contact with pancreas)
- In relation to 9th to 11th ribs (if you have a rib fracture, you die due to haemorrhage)
Coeliac trunk angiogram
- Coeliac trunk is an arterial branch from the abdominal aorta
- One of the branches of CT is the tortuous splenic artery
- Artery running to the right is the common hepatic artery, running to supply the liver
This consists of the duodenum, jejunum and ileum.
This is 25-30cm long and except for the 1st part does not possess a mesentery. It extends from the pylorus to the duodenojejunal junction and is arranged in a C-shaped fashion around the pancreas.
The duodenum is divided into 4 parts:
- 1st or superior:
- Extending from the pyloric orifice to the superior duodenal flexure
- It is 2.5 cm long and lies at the level of LV1. This is the only intraperitoneal part.
- 2nd or descending:
- Extending from the superior duodenal flexure to the inferior duodenal flexure.
- It is 8-10 cm long and extends from LV1 to LV3
- 3rd or horizontal:
- Extending to the left from the inferior duodenal flexure at the level of LV3.
- It is 10 cm long
- 4th or ascending:
- Extends upwards (2.5 cm long) to the duodeno-jejunal flexure (at the level of LV2, 2.5 cm to the left of the midline).
The mucosa of the duodenum is thrown into circumferentially arranged folds known as plicae circulares, which serve to increase the surface area to improve absorption.
Two papillae may be seen in the medial wall of the 2nd part:
- The greater duodenal papilla lies 8-10 cm from the pylorus, and has at its summit the opening of the hepatopancreatic ampulla (of Vater). The ampulla receives the bile duct and the main pancreatic duct. The bile duct and hepatopancreatic ampulla are guarded by the sphincter of the hepatopancreatic ampulla.
- The lesser duodenal papilla lies about 6-8 cm distal to the pylorus and has at its summit the opening of the accessory pancreatic duct.
- Duodenum gets its name because it's 12 thumb-breadths long
- Leads on directly from the stomach
- The duodenum is shaped like a C, enclosing the head of the pancreas
- The interior of the duodenum is thrown into permanent folds (unlike the rugae of the stomach, which can expand and flatten). These are the plicae (mucosal folds, valves of ___), which are designed to increase the surface area of the small intestine
- Aorta, IVC, suprarenal glands, kidneys, spleen
- 1st part of duodenum - LV1; take the point halfway between the jugular notch and the pubic symphysis
- 3rd part of the duodenum is at LV3
- Pyloroduodenal junction is where the stomach drains its contents into the duodenum
- Duodenojejunal junction is where the duodenum meets the jejunum
- Parts of the duodenum
The vessel running through the pancreatic notch and going in front of the 3rd part of the duodenum is the superior mesenteric artery (supplies midgut), alongside it is the superior mesenteric vein
- Anterior and posterior inferior pancreaticoduodenal arteries arise from the SMA above the 3rd part of the duodenum and run around to the 2nd part
The duodenojejunal flexure
- Duodenum comes up to the fourth part, to join the jejunum
- There is a distinct bend here
- This bend is maintained by a CT ligament anchoring the flexure to the posterior abdominal wall (can get mesenteric folds and recesses that are important in bowel perforation, where the recess can turn into an abscess)
- Superior and inferior ____ recess
Jejunum and ileum
- Together these are 5-8 m in length. The jejunum has more folds of the mucosa (plicae circulares or valves of Kerkring), more villi and a thicker, more vascular wall than the ileum.
- There are several important distinguishing features between ileum and jejunum:
|Position||Upper left abdomen||Lower right abdomen|
|External feel and appearance||Thick, wide, vascular||Thin, narrow, pale|
|Peyer's patches (aggreg. lymph follicles)||Few||Many|
- Jejunum is where most of the absorption of nutrients occurs
- Plicae are macroscopic features increasing the surface area, occurring in the jejunum and ileum as well. These are 1 of 3 anatomical features to maximise surface area. Others:
- Villi - fingerlike projections (light microscope)
- Microvilli - projections on the surfaces of the cells as well (electron microscope)
This is in addition to the macroscopic structures (plicae) that also increase surface area
- On barium xray, we see fluffy appearance in the small intestine superiorly - this represents the jejunum (the villi make it look fluffy)
- Mucosal folds (fluffiness) is lost towards the end of the small intestine (ileum). The mucosal folds decrease as we go from the jejunum to the ileum
The jejunum and ileum - contrast of walls
- Lots of mucosal folds
- Few Peyer's patches
- Thick walled (rich vascular supply and lots of mucosal folds)
- Many villi
- Very vascular
- Few mucosal folds
- Peyer's patches are little blobs particularly in the ileum - lymphoid aggregates embedded in the wall of the small intestine. Much higher bacterial populations in the ileum than in the jejunum (as we're further through the gut, where nutrients may not have been used, further away from stomach acid).
- Thin walled
- Few villi
- Less vascular
Vasculature of the jejunum
- Very vascular - need a good blood supply to take nutrients from the food and shunt them back to the liver
- Initial branch of the SMA, with many branches going out to the gut
- Have quite long vasa recti (straight vessels)
- Not too much branching archae (?) patterns of branching/combining compared to the ileum
Vasculature of the ileum
- Less vascular
- Fewer vasa recti, and they are shorter
- Lots of archae (?) patterns
Blood supply (from superior mesenteric)
By branches of the superior mesenteric a. (jejunal and ileal brs), which are distributed to the left from the artery as it descends.
- SMA supplies small bowel and the proximal part of the large bowel
- This artery comes out through the pancreatic notch, in front of 3rd part of duodenum (supplies all of small bowel except for first part of duodenum, and a lot of the large bowel, too)
- Jejunal arteries
- Ileal arteries
- Anterior and posterior coecal arteries, and appendicular artery, arising from the ileocolic artery
- We also have the right colic artery, middle colic artery
- The large artery looping around is an anastamotic artery.