LECTURE 11 & 12: ABDOMINAL VISCERA

ABDOMINAL CONTENTS

DIVISION

The location of abdominal viscera is divided into 4 quadrants:

- horizontal line across the umbilicus divides the upper quadrants from the lower quadrants

- vertical line from the ziphisternum through the umbilicus to the pubic symphysis divides the

right quadrants from the left quadrants

OESOPHAGUS

- ~25cm long muscular tube that traverses the neck,

thorax and abdomen

o Transfer of food through peristalsis

- Begins at the cricoid cartilage at C6, and then

descends behind the trachea into the posterior

mediastinum

- Descent into the abdomen is through the

oesophageal hiatus in the diaphragm (T10) which

is made from a sling of the left crus on the right

side

o Diaphragmatic contraction closes the

oesophageal hiatus and blocks the reflux

of gastric contents

- Enters the stomach on the right side

- Oesophagus is lined by stratified squamous epithelium which abruptly changes into gastric

mucosa at the gastro-oesophageal junction

- Oesophagus has natural narrowing points along its entire length with specific vessel supply

o Cervical

Upper oesophageal sphincter (narrowing)

Inferior thyroid artery (arterial)

Brachiocephalic and systemic (venous)

Deep cervical nodes

o Thoracic

Aortic arch and left main bronchus (narrowing)

Oesophagus branches from descending aorta (arterial)

Azygous and systemic (venous)

Mediastinal nodes

o Abdomen

Oesophageal hiatus (narrowing)

Left gastric from aorta (arterial)

Left gastric portal with overlaps from systemic

(venous)

Pre-aortic nodes

HIATUS HERNIA

It is not uncommon for herniation of the stomach to occur at the

oesophageal hiatus:

- Paraosoeosophageal hiatal herniation is one sided (5%)

- Sliding hiatial herniation when a portion of the stomach is pulled upwards

STOMACH

- Located in the LUQ

- J shaped organ

o Less curvature is on the medial side

o Greater curvature on the lateral side

- Two openings

o Cardiac orifice is the point in which the

oesophagus enters (proximal part of lesser

curvature)

o Pyloric orifice is the distal opening

- Fundus is a domed shaped projection above the

stomach

o Full of gas

- Body of the stomach

o Extends from the cardiac notch to the angular

notch in the lesser curvature

- Pyloric antrum is a funnel from the body into the pylorus

(most tubular part of the stomach)

o Pylorus is characterised as a strong muscular tube

that functions as the pyloric sphincter

The lumen travelling through is called the

pyloric canal

- Organ is tether to the under surface of the liver from the

less curvature by a mesentery called the lesser omentum,

the greater curvature of the stomach is anchored in the

posterior abdominal wall by a the greater omentum

- Rugae are internal folds within the stomach which are

most prominent at the pylorus

ARTERIAL BLOOD

- Lesser curvature has a right and left gastric artery which

richly anastomose

- Greater curvature has a right and left gastroepiploic

artery which also richly anastomose

DUODENUM

- First part of the small intestine as a C shaped loop (10

inches in total) that encloses the pancreas

- Only the very first portion of the duodenum connecting

to the stomach is intraperitoneal, whilst the

remainder is retroperitoneal

- Primary function of digestion and absorption

- Duodenum is divided into 4 parts:

o Duodenal cap is the first portion and is

directed upwards and backwards over the

right crus, right psoas major and hilum of

the right kidney (2 inches)

Peptic ulcers will usually occur here

o Vertical descending portion is completely

retroperitoneal (3 inches)

Transverse mesocolon is a landmark

found here that encapsulates the

transverse colon

Choledochoduodenal junction if

found half way down inside

Major duodenal papilla is where the bile

duct pancreatic duct enters

Minor duodenal papilla is the accessory

duct to pancreas

o Horizontal part of the duodenum traverses right psoas to

left psoas (4 inches)

Slightly tethered to left psoas

Found at the level of L3

Root of the mesentery found here which anchors

the jejunum and ileum

o The final portion curves upwards on left psoas and comes

forward

Duodenal-jejunal flexure marks the point the

small intestine becomes intraperitoneal with the

jejunum

JEJUNUM AND ILEUM

- 4-6 metres in length

o 2/5 is jejunum and 3/5 is

ileum with no clear

demarcation

o Jejunum tends to be in

the situated in the LUQ

and is larger in diameter

with thicker walls and

higher degree of folding

o Ileum is in the RLQ

- Completely intraperitoneal and

suspended by mesentery

o Attachment to the

posterior abdominal wall

and 3 part of the

duodenum

o Blood supply from the

aorta feeds the small intestine by entering the mesentery

ARTERIAL BLOOD SUPPLY

- Jejunum is supplied by vasarector which arise from a few arcades (long arterial loops)

- Ileum has an abundance of arcades and much smaller vasarector compared to jejunum

LARGE INTESTINE

- The start of the large intestine is at the ileo-

caecal junction

o Ileo-caecal valve is a smooth muscle

sphincter to this opening

- 1.5 metres in length

o Caecum, ascending colon (right

colic/hepatic flexure), transverse colon

(left colic/splenic flexure), descending

colon, sigmoid colon (s-shaped bend),

and the final centred portion is the

rectum (one continuous longitudinal

muscle)

- Unlike the small intestine which is a single

longitudinal muscle coat, the large intestine

consists of three distinct muscle bands called

tinea

o The short banding gives the large

intestine a stacked appear which is

termed haustra

- The large intestine has characteristic fat tags

called epiploic appendices hanging off it

APPENDIX

- Found projecting off from the caecum at the

point in which the three tinea converge

- The tip of the appendix is variable in length

o 1/5 are found hanging off in the pelvic brim = pelvic appendix

o Most are found tucked behind the large intestine = retrocaecal appendix

LIVER

- Largest solid viscera found tucked up behind the costal

margin

- Fills the RUQ

- The anterior surface is smooth and is called the

diaphragmatic surface

o Its transition into the visceral surface is

demarcated by the sharp inferior border

o Divided into two lobes by a falciform ligament

(double folded peritoneum) that connects the

liver the anterior abdominal wall at the level of

umbilicus

Ligametum teres is an obliterated vein

and runs inferiorly

Remnant of umbilicus vein that

used to receive blood from the

placenta

- From the anterior surface the liver is divided into one

large right lobe and one small left lobe, but both are

functionally identical

- The visceral surface is imprinted by all the structures it

sits on and bears the hilum

o H shaped fissure further divides the liver into a

caudate and quadrate lobe

o Gall bladder also found next to the quadrate

lobe

o IVC is found attached to the liver next to the caudate lobe

o Ligamentum venosum is a remnant of the ductum venosum that drained directly into

the hepatic vein (and then the IVC)

HEPATIC HILUM/PORTA HEPATIS

- Hepatic artery is divided into left and right to supply each functional half of the liver (left of

hilar)

- Hepatic duct divides in half to collect bile products from both halves of the liver (right of hilar)

- Portal vein receives blood from the digestive system(middle of hilar and behind the arteries

ducts)

o The hepatic vein is responsible for draining the viscus directly into the IVC

GALL BLADDER

- Sits a groove on the visceral surface of the liver

- Fundus of the gall bladder it its bottom which narrows to

form the body; further narrowing produces the neck and

continues as a duct (cystic duct) to the common hepatic

duct

- Cystic duct and hepatic duct converge to form the common

bile duct which runs between the pancreas and

duodenum, before joining with the pancreatic duct and

emptying at the major duodenal papilla

o the opening of the papilla is controlled by a

complex sphincter, hepatopancreatic ampulla, that

closes when inactive to allow the accumulation of

bile into the gall bladder

PANCREAS

- organ both exocrine and endocrine functions

- functionally broken up into the head, neck, body and

tail

o head fills the C shaped curve of the duodenum

and has an unicinate process that is a landmark

for the superior mesenteric vessels

o body overlies the DJ flexure but is deep the

pylorus of the stomach

o the tail leads to the hilum of the spleen

- the main pancreatic duct will empty into via the major

duodenal papilla, but the accessory duct will empty at

a more proximal at the minor duodenal papilla to drain

the uncinated process

SPLEEN

- Oval shaped organ about the size of a clenched fist (tend

to atrophy over time) in the LUQ

o The spleen overlies ribs 9-11

- Smooth diaphragmatic surface

o Smooth surface is usually demarcated from the

visceral surface by notches on the margin

- The visceral surfaces bears the impressions of the

stomach and kidneys

o Hilar is found on this side

Splenic artery and splenic vein

Splenic artery follows the superior

border of the pancreas