LOWER GIT ANATOMY - · PDF fileLOWER GIT ANATOMY Assoc Prof Dinesh ... Nerve Supply of the Stomach Erratum © Copyright National University of Singapore. ... Blood Supply of the Pancreas

© Copyright National University of Singapore. All Rights Reserved.

LOWER GIT ANATOMY

Assoc Prof Dinesh Kumar Srinivasan

MBBS, MS, PhD (NUS), Fellow (USA)

Co-Chair, Integrated Lead Educators

Department of Anatomy

Yong Loo Lin School of Medicine, NUS

2nd Nov 2017 @ 8.30 - MD1 LT37


• Sympathetic nerve fibres

(preganglionic) pass through

the greater splanchnic

nerves and terminate in the

celiac ganglion

• Postganglionic sympathetic

nerves supply the stomach

• Stomach is supplied by the

sensory (pain) fibres which

accompany the sympathetic

nerve fibres and reach the

T5-T9 spinal sensory

ganglia

• Visceral referred pain from

gastric ulcer is referred to

the epigastric region

Nerve Supply of the Stomach

Erratum


OBJECTIVES

• To describe the location of peritoneal spaces, and understand their

clinical significance

• To describe the location, structural features, vascular supply and

innervation of the pancreas, small and large intestines

• To understand the relations of each of these organs with neighbouring

structures

• To appreciate the anatomical basis of these organs for clinical

examination, surgical operation and patient management

• To name the main branches/tributaries of the abdominal aorta and

inferior vena cava, and know their location and course


• The peritoneal cavity is a POTENTIAL space within the layer of

peritoneum.

Peritoneal Cavity


Lesser Sac (Omental Bursa)

• Lies posterior to the

stomach and the lesser

omentum

• Superiorly bounded by the

diaphragm

• Inferiorly bounded by the

layers of greater omentum

• Communicates with the

greater sac through the

omental foramen

• Its left margin is formed by

the spleen

Stomach

Greater Omentum

Peritoneal Cavity


View from below

leftright

View from above

left right

Peritoneal Reflections


Transverse mesocolon

Greater sac

Peritoneal cavity in sagittal section showing the arrangement of the lesser

sac (light blue) and the greater sac (light pink).

Greater Sac: main part of

the peritoneal cavity

– Transverse mesocolon

divides the greater sac

into:

• Supracolic

compartment

(stomach, liver and

spleen)

• Infracolic

compartment (small

intestine and colon)

Peritoneal Cavity


Peritoneal Compartments


Posterior abdominal wall (anterior view)

Supracoliccompartment

InfracolicCompartment(Right & Left)

Rt. paracolicgutter Lt. paracolic

gutter

Mesentery of transverse colon

Mesentery of small intestine



Paracolic gutters lie on the

lateral sides of the

ascending and descending

colons

Right paracolic gutter

communicates with right

subhepatic space

Left paracolic gutter is

separated from the

diaphragm by the

phrenicocolic ligament



Pancreas

Pancreas

• Retroperitoneal

• Lies between the duodenum

(on the right) and spleen (on

the left)

• Divided into:

• Head, neck, body, tail and

uncinated process

• The root of the transverse

mesocolon lies along its

anterior margin


Tail

Components

• Head, neck, body, tail

• Uncinate process

Ducts

• Main pancreatic duct

opens into the ampulla

of vater. Accessory

pancreatic duct opens

into the duodenum.

Functions

• The pancreas produces

an exocrine secretion

that enters the

duodenum and

endocrine secretions

that enter the blood

Body

Body

Head

Main duct

Accessory duct

Uncinate process

Neck

Pancreas


Relations

Head of pancreas:

attached to the descending part

of the duodenum; common bile

duct lies posteriorly

Neck of pancreas:

to superior mesenteric vessels

posteriorly

Body of pancreas:

forms the floor of the omental

bursa

stomach anteriorly

left kidney posteriorly

Tail of pancreas:

related to the hilum of the

spleen

Stomach

Spleen

Pancreas

Duodenum

(L) Kidney

CommonBile duct

Pancreas


Splenic artery

Anterior superior

Pancreatico

duodenal artery

Anterior inferior

Pancreatico

duodenal artery

Superior Mesenteric artery

Supplied by the:

Head:

Branches of the

gastroduodenal and

superior mesenteric

arteries via

• Superior pancreatico

duodenal arteries

• Inferior pancreatico

duodenal arteries

Neck, Body, Tail:

Branches of splenic artery

Blood Supply of the Pancreas


Venous Drainage

Splenic vein and Portal vein

Nerve Supply

Sympathetics

Decrease pancreatic

secretion.

Parasympathetics

Increase pancreatic

secretion.

Blood Supply & Innervation of Pancreas


CD

Portal-Systemic Anastomoses

• Important sites of PSA

are lower oesophagus

(A), rectum (B), umbilicus

(C), and posterior

abdominal wall (D)

• Haemorrhage is common

from the first two sites –

A, B

• Liver or portal obstruction

causes these veins to

dilate widely, possibly

leading to severe venous

haemorrhage from

oesophagus or rectum

Alcoholic liver cirrhosis caused by

destruction of hepatocytes leads to portal

hypertension. Cirrhosis may be treated

by anastomosing the portal and systemic

venous systems


Clinical Anatomy

1. Pancreatitis - inflammation of pancreas which is

associated with alcoholism

2. Cancer of head of pancreas can obstruct common bile

duct giving rise to obstructive jaundice

Duodenum

Common bile duct

lies behind head of

pancreas. Hence a

cancerous mass in

the head of

pancreas can

compress the

common bile duct.

Head of pancreas

Pancreas


Small intestine

• Extends from the pylorus of the

stomach to the ileocecal

junction

• Major part of digestion and

absorption takes place in the

small intestine

• Divided into:

• Duodenum

• Jejunum

• Ileum

Small Intestine


• 10 inches long; divided into 4 parts

• FIRST part of duodenum = DUODENAL CAP

• Most duodenal ulcers occur here

• SECOND part of duodenum contains entrance for common bile duct – MAJOR DUODENAL

PAPILLA

• Most of the duodenum is RETROPERITONEAL.

1

2

34

Gastroduodenaljunction Duodenojejunal

junction

Duodenum


1

2

3

4

Duodenum:

1. 5 cm long, L1 level

2. 7-10 cm, rt of L1-L3

3. 6-8 cm, crosses L3

4. 5 cm, to L2

Duodenum


Supplied by the branches of celiac

trunk and superior mesenteric

artery

Superior pancreatico duodenal

artery (indirectly from celiac):

supplies the part above the entry of

bile duct

Inferior pancreatico duodenal artery

(a direct branch of SMA): supplies

the part distal to the entry of bile duct

Both superior and inferior pancreatico

duodenal arteries anastomose

Duodenal veins drain into the portal

vein

Innervated by the

sympathetic nerves from the celiac

and superior mesenteric plexus and

parasympatheric (vagus)

Neurovasculature of the Duodenum


Duodenal ulcer:

• Occurs commonly in superior part of the duodenum either anteriorly

or posteriorly

• Anterior duodenal ulcer erodes peritoneum causing peritonitis

• Posterior duodenal ulcer erodes either gastroduodenal artery or

posterior superior pancreaticoduodenal artery causing hemorrhage

(fatal in some cases)

Duodenum


Jejunum and Ileum

Anterior view

• Jejunum and ileum

forms the rest of the

small intestine

• Duodeno jejunal

junction to ileocaecal

junction

• Length 20 feet

approximately. Upper

2/5 jejunum rest ileum.

• Entirely intraperitoneal

• Jejunal loops - LUQ.

• Ileal loops – RLQ.


• Fan shaped mesentry

with long free edge

and a short root (red

line)

• Mucosa – circular

folds plicae circulares

• Peyer’s patches

(lymphoid tissue)

frequent in terminal

ileum.

Root of mesentery

Mucosa

Jejunum and Ileum Morphology


• Proximal two-fifths

• Wide-bored & thick-walled. Closely

arranged plicae inside.

• Less prominent ARTERIAL

ARCADES

• Longer VASA RECTA

• Distal three-fifths

• Smaller in diameter & thinner

walls

• Prominent ARTERIAL

ARCADES

• Shorter VASA RECTA

Vasa recta

Arterial arcades

Jejunum vs Ileum


Portal vein

SMV

Splenic vein

IMV

• Arterial supply from the

superior mesenteric artery

(SMA)

• Superior mesenteric vein

(SMV) drains the venous

blood from the jejunum and

ileum into portal vein

• SMV joins with splenic vein

to form the portal vein

Jejunum and Ileum


• The small intestine is supplied by

autonomic (sympathetic and

parasympathetic) and sensory

fibers in the celiac and superior

mesenteric plexuses.

• Sympathetic fibres (greater

splanchnic):

• reduce bowel motility

• reduce intestinal secretions

• cause vasoconstriction

• Parasympathetic nerve fibres

(vagus):

• increase bowel motility

• stimulate intestinal secretions

• cause vasodilation

• The sensory fibers are sensitive

to distension and nociceptive pain

Nerve Supply to Small Intestine


• Lymphatic vessels from

the walls of jejunum and

ileum drain into

mesenteric lymph

nodes (found between

the layers of

mesentery).

• Efferent lymphatic

vessels from the

mesenteric nodes drain

to the superior

mesenteric nodes

(found around the origin

of SMA)

Lymphatics Vessels of Jejunum and Ileum


• Extends from ileum to anus

• Caecum, appendix,

ascending, transverse,

descending, and sigmoid

colon, rectum and anal

canal.

• Taenia coli, Haustra,

appendices epiploicae

(fatty tags) are main

features

• Iliocaecal valve – folds of

mucosa- not effective.

• Physiological sphincter at

terminal ileum

• Appendix (3- 5”) with its

short mesentery

(mesoappendix).

The Large Intestine

Visceral pain from

appendix is referred to

T10 dermatome

(umbilicus)


• Lies below the

junction of the ileum

and large intestine in

the right iliac fossa

• has 3 bands of teniae

coli

• has no mesentery

Cecum


• Lies in the RLQ

• Forms right colic flexure

(arrow)

• Supplied by right colic

branches of SMA

• Innervated by vagus and

sympathetic

Ascending Colon


• Occupies the umbilical region

• Extends from right to left colic flexures (arrows)

• Suspended by the transverse mesocolon

• Supplied by middle colic artery (from SMA) and left colic artery (from IMA)

• Innervation: • proximal 2/3rd: by

parasympathetic vagusand sympathetic;

• distal 1/3rd: by parasympathetic pelvic splanchnic and sympathetic

Mesocolon

Transverse Colon


• Retroperitoneal

• Begins at splenic

flexure to end at the

pelvic brim

• Supplied by left colic

branches of inferior

mesenteric artery

(IMA)

• Parasympathetic

innervation by pelvic

splanchnic nerve

Descending Colon


• Links the descending colon with rectum

• Suspended by a mesentery (sigmoid mesocolon)

• Supplied by the sigmoid branches of IMA

• Innervated by the lumbar part of the sympathetic trunk and pelvic parasympathetic (inferior hypogastric plexus)

Sigmoid Colon


3 UNPAIRED arteries arising from the anterior of the AORTA

COELIAC TRUNK = FOREGUT + liver, pancreas and spleen

SUPERIOR MESENTERIC ARTERY (SMA) = MIDGUT

INFERIOR MESENTERIC ARTERY (IMA) = HINDGUT


Branches of Superior Mesenteric Artery

Middle colic artery

ileocolic artery

Right colic artery

Jejunal arteries

Ileal arteries


Branches of Inferior Mesenteric Artery

• The junction of the mid- and

hindgut is near the left

(splenic) flexure of the colon.

• There is a change from

superior to inferior

mesenteric artery supply at

this level, but with

anastomoses between them.

Left colic artery

Sigmoid arteries

Superior rectal artery


• The lymphatic drainage of the

bowel follows the arterial

supply, not the venous

drainage.

• The lymph nodes are grouped

around the abdominal aorta

• All lymph drains into the

cisterna chyli.

• Cisterna chyli is an

elongated lymphatic sac

located in front of the L1 & L2

bodies

• The thoracic duct

commences from the cisterna

chyli

LymphaticsCoeliac nodes

Superior mesenteric nodes

inferior mesenteric nodes

Cisterna chyli

Thoracic duct


Innervation of the gut

• Abdominal viscera supplied by AUTONOMIC nervous system.

• Sensory fibres most important

• Sympathetic sensory (mediate PAIN):

– THORACIC SPLANCHNIC (T5-T12)

– LUMBAR SPLANCHNIC (L1+L2)

• Parasympathetic sensory (regulate reflex gut function):

– VAGUS NERVE

– PELVIC SPLANCHNIC NERVES (S2-S4)


Thoracic Splanchnic Ns.

(T5-T12)

• Greater Splanchnic N.

(T5-T9)

• Lesser Splanchnic N.

(T10-T11)

• Least Splanchnic N.

(T12)

Thoracic splanchnic N. (T5-T12) - Sympathetic

Lumbar Splanchnic N. (L1, L2) - Sympathetic

Sacral Splanchnic N. Sympathetic

The autonomic nerves

are routed via plexuses

along the abdominal

aorta and its branches.

Pelvic Splanchnic N. (S2-S4) - Parasympathetic


Innervation: the sensory fibres

are most important.

In the viscera:

Sensory fibres running with the

sympathetic mediate pain

Sensory fibres running with the

parasympathetic (vagus or

sacral) are involved in reflex

regulation of gut function

Autonomic Control of the Gut

Sympathetic

Parasympathetic(via vagus/pelvic S2-4)


Para-sympathetic from vagusand sympathetic (T10-12) from Superior Mesentericplexus


• Begins at the aortic hiatus in the diaphragm at T12 and ends by dividing into the right and left common iliac arteries at L4

• Common iliac artery divides into external and internal iliac arteries

• On its right side lie the IVC, cisterna chyli and azygos vein

• On its left side lies the left sympathetic trunk

Abdominal Aorta


• Formed by the

union of common

iliac veins at L5

• Ascends on the

right side of the

aorta, passes thru

the caval foramen

(T8) and drains into

right atrium

• Tributaries:

Inferior Vena Cava


1. Subcostal (T12)

2. Iliohypogastric (L1)

3. Ilioinguinal (L1)

4. Genitofemoral (L1,2)

5. Lateral Femoral Cutaneous

(L2,3)

6. Femoral (L2-L4)

7. Lumbar Sympathetic Ganglia

Somatic & Autonomic Nerves


1. Celiac plexus

2. Superior mesenteric plexus

3. Inferior mesenteric plexus

4. Renal plexus

Components:

• pre- and post-ganglionic

sympathetic fibres

• visceral sensory

• pre-ganglionic

parasympathetic fibres

Aortic Plexus

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LOWER GIT ANATOMY - · PDF fileLOWER GIT ANATOMY Assoc Prof Dinesh ... Nerve Supply of the Stomach Erratum © Copyright National University of Singapore. ... Blood Supply of the Pancreas