The Stomach (7) / Liver and Biliary Tree (8) / Pancreas, Small Intestines, Intro to Large Intestine (9)

The stomach

• extends from the esophagus to the duodenum

• expanded portion of the gut

• can hold 2-3 L of food

• part of the upper GI tract

Functions of the stomach

• stores food

• mechanical and chemical digestion and creation of chyme (mixture of food & gastric juices)

• controls the rate and delivery of chyme into duodenum

• secretes intrinsic factor

• helps regulate digestion and appetite

• destroys pathogenic bacteria

Anatomical location of the stomach

Location when supine

• epigastrium

• left hypochondrium

Anterior relations of the stomach

• anterior abdominal wall

• liver

• diaphragm

Posterior relations of the stomach insert image from slife 9

• diaphragm

• lesser sac

• spleen

• splenic artery

• pancreas

• left kidney

• left suprarenal gland

• transverse colon

• transverse mesocolon

O

Omenta

There’s 2 → Lesser omentum and greater omentum

• Double-layered peritoneal folds

• Peritoneum- serous membrane that lines abdominal cavity and organs, important for bringing blood vessels to & fro

• Lesser Omentum extends from lesser curvature of stomach to liver

• Greater Omentum extends from greater curvature of stomach to transverse colon

Label the parts of the stomach slide 11

a. esophagus

b. cardia

c. fundus

d. cardiac notch

e. body

f. pyloric antrum

g. pyloric canal

h. pyloric sphincter

i. duodenum

Gross anatomy of the stomach

• muscular organ

• peristalsis continues in the stomach from middle of stomach towards pylorus

• rugae in mucosa and submucosa allow expansion

• folds flatten when the stomach is distended

Histology of the stomach

• Serosa, Muscularis Externa, Submucosa, Mucosa

• Muscularis externa: longitudinal, circular, and oblique layers. Big movements of the stomach.

• Mucosa

  • simple columnar epithelium

  • muscularis mucosae enables nuanced movement of mucosa

Histological zones of gastric glands

Cardiac

• Branched tubular glands with coiled secretory portions

• Secrete mucous and lysozyme

Pyloric

• Branched tubular glands with coiled secretory portions

• Secrete mucous, lysozyme, and gastrin

Principal

• Branched tubular gastric glands

• Contain a variety of cells that collectively secrete gastric juice

Gastric Glands of Principal Zone

Luminal Surface

• surface mucous cells

Isthmus

• contains most parietal cells (HCl and IF)

Neck

• mucous neck cells

• contains most stem cells

Base

• chief cells (Pepsinogen)

• neuroendocrine cells

Gastric Gland Cells - Surface mucous and mucous neck cells insert image for slide 12

• Forms a viscous barrier to protect against the acidity of gastric juices

Gastric Gland Cells - Parietal cells

• HCl kills microbes and activates pepsinogen

• IF facilitates the absorption of Vitamin B₁₂ in the terminal ileum

Gastric Gland Cells - Chief cells

• Secrete pepsinogen, which breaks down protein in active form

Gastric Gland Cells - Stem cells

• differentiate into adult GI cells

Gastric Gland Cells - Neuroendocrine cells

• Secrete hormones

• Gastrin - stimulates HCl production

• Serotonin - increases peristalsis

• Somatostatin - inhibits local neuroendocrine cells

• Ghrelin - induces hunger

Submucosa of stomach

Dense, irregular connective tissue

Contains: Blood vessels, lymphatic vessels, meissener’s plexus (enteric nervous system)

Serosa of stomach

• The stomach is an intraperitoneal organ therefore the outer layer is a serosa

• Thin layer of connective tissue

• Covered by a simple squamous mesothelium (visceral peritoneum)

Neurovasculature of stomach

Stomach is a foregut structyre

• receives arterial blood supply from the celiac trunk

• lymph drains into the celiac nodes

• receives sympathetic innervation via greater splanchnic nerve and celiac ganglia

Arterial supply of the stomach

• Needs a rich blood supply for churning and secretion of gastric juices

• Has 3 branches: Common Hepatic, Splenic, Left Gastric

• All three supply the stomach

Venous drainage of stomach

• Smaller veins drain into three main veins; Portal vein, Splenic, Superior Mesenteric

• All blood drains directly or indirectly into the portal vein

Lymphatic drainage

• follow similar pattern to arteries, but opposite direction

• Gastric nodes → celiac nodes → intestinal trunk → cysterna chyli →thoracic duct → left internal jugular/subclavian vein

Sympathetic innervation of the stomach

• carries vasomotor fibers to the stomach (smooth muscle)

• carries motor fibers to the pyloric sphincter (skeletal muscle)

• arise from t5- t9 segments of the spinal cord

• fibers pass in greater splanchnic nerve to celiac plexus

Parasympathetic innervation of the stomach

Vagus Nerve (CN X)

• arises from medulla oblongata and passes through the diaphragm

• secretomotor fibers to gastric glands

• motor fibers to gastric muscle

• inhibitory fibers to pyloric sphincter

(you want the stomach to finish the churning before its pushed into small intestine)

• reflex afferent fibers to inhibit ingestion when stomach expands

(so when you’re full you stop eating)

Pain in the stomach

• visceral afferent fibers for pain are carried by the greater splanchnic nerve to the spinal cord

• cause referred pain in dermatomes T5- T9, sensory fibers

• pain perceived in the epigastrium

• ** epigastric pain doesn’t always mean it’s coming from the stomach as pain distribution is quite complex

Functions of the liver

Hematological regulation

• synthesis of plasma proteins — albumin, clotting factors, etc

• removal of toxins, excess hormones, antibodies, etc

Metabolic regulation

• stores glucose (glycogen) , minerals, and vitamins

• regulates circulating levels of triglycerides, fatty acids, and cholesterol

• removes excess amino acids for protein production or storage

Production and secretion of bile

Location of the liver

• right hypochondrium, epigastrium, and left hypochondrium

• lies beneath the diaphragm, moves with it

• covered by the ribs

• moves with respiration and position

Anterior relations of the liver

• anterior abdominal wall

• diaphragm

• lower margins of right lung and pleura (above liver)

• costal margins (ribs 7 to 11)

Posterior relations of liver

• esophagus

• stomach

• right kidney

• duodenum

• some of the diaphragm

• hepatic flexure

• right kidney

• inferior vena cava

• gall bladder

Diaphragmatic surface of the liver insert image from slife 8

• faces diaphragm

• part of the liver covered by diaphragm and anterior body wall, therefore regular and convex surface

• a: falciform ligament

• b: left lobe

• c: right lobe

• d: gall bladder

Visceral surface of the liver insert slide 9

• faces abdominal viscera

• molded by it, therefore irregular concave surface

a. hepatic portal vein

b. caudate lobe

c. bare area

d. hepatic ducts

e. hepatic artery proper

f. quadrate lobe

g. gall bladder

Fissures and Veins/ Arteries of Visceral Surface

a. fissure for ligamentum venosum

b. hepatic portal vein

c. inferior vena cava

d. fissure for ligamentum teres

e. hepatic artery proper

Contents of porta hepatis

• right and left hepatic ducts

• right and left branches of hepatic arteries

• hepatic portal vein

• sympathetic and parasympathetic nerve fibers

• hepatic lymph nodes

** Blood does not leave liver through porta hepatis but instead IVC

Vascular segments of the liver

Portal lobes (aka parts of the liver)

• right = right lobe - LMD

• left = left + quadrate + LMD

• caudate lobe

Further divided into 8 segments

8 segments of the liver insert image from slide 12

a. right lateral division

b. right medial division

c. left medial division

d. left lateral division

e. VII

f. VIII

g. IV

h. IV

i. II

j. VI

k. V

l. III

m. cantlie line

each segment is supplied by a branch of the hepatic artery and hepatic portal vein. drained by a hepatic duct

Falciform ligament

• double fold of peritoneum

• connects anterior and superior surfaces of the liver to the anterior abdominal wall

• between right anatomical surface lobe and left

Ligamentum teres

• remnant of the umbilical vein, before birth it aided in delivering nutrients to the liver

• runs in the free edge of falciform ligament

• aka round ligament of the liver

insert image from slide 14

Ligamentum venosum

• remnant of the ductus venosus

• attached to the portal vein and inferior vena cava

insert image from slide 15

Coronary ligament

• reflection of visceral peritoneum from the posterior surface of the liver onto the diaphragm

• it surrounds the bare area

insert image from slife 16

Bare area of liver

• bare area is in direct contact with the diaphragm

• therefore bare area is not covered by visceral peritoneum

• liver is most invested in peritoneum

insert imagr from slide 17

Identify the missing parts

insert image from slide 18

Left triangular ligament

Right triangular ligament

Identify ligaments

insert image from slide 19

a. hepatoduodenal ligament

free border of the omentum that contains the bile duct, portal vein, and hepatic artery

b. hepatogastric ligament

lesser omentum

Double blood supply to liver (and percentages)

Hepatic arteries ~ 30%

Hepatic portal vein ~ 70%

Hepatic portal vein

• formed by the union of the superior mesenteric vein with the splenic vein

• delivers blood rich in nutrients directly from GI tract, where we absorb nutrients, toxins, water

Portal systemic anastomoses

• minor communications between the portal and systemic systems

• in liver disease HPV, may become constricted

• blood from GI tract can reach the heart through anastomoses

• can lead to varicose veins

• bleeding from esophageal varices may be fatal

  • as you swallow they could bleed and you can choke

Microscopic structure of liver

• liver is composed of units called lobules

• they are in a hexagonal shape

• lobules held together by connective tissue

Histology of liver lobule

a. central vein

b. plates of hepatocytes (liver cells)

c. sinusoids (spaces in between)

d. portal triad/tract

red- hepatic artery

blue - portal vein

green - bile ductule

Flow of blood in the liver

• blood brought to lobule by branches of hepatic artery and portal vein

• passes through sinusoid to central veins: nutrients, oxygen, toxins, etc, picked up by hepatocytes en route

• blood flows from central veins → hepatic veins → inferior vena cava

• insert image from slide 28

Flow of bile in liver

• bile is secreted by hepatocytes into bile canaliculi → interlobular biliary ducts → bile ductule → bile ducts

• bile flows in opposite direction to blood

• insert image from slife 28

What 3 veins drain into IVC to form the venous drainage of the liver?

right hepatic vein, left hepatic vein, intermediate hepatic vein

Lymphatic drainage of the liver

• 1/3 to ½ of the lymph received by the thoracic duct comes from the liver as it has such a rich blood supply

• hepatic lymph nodes are located at the porta hepatis and around the vessels within the lesser omentum

LYMPH DRAINS

hepatic nodes → celiac nodes → intestinal trunk → cisterna chyli and thoracic duct

Autonomic innervation of the liver

sympathetic innervation:

fibers pass in greater splanchnic nerve to celiac plexus → hepatic plexus

parasympathetic innervation: vagus nerve

Bile flow insert image from slide 32

a. liver

b. left hepatic duct

c. right hepatic duct

d. common hepatic duct

e. gall bladder

f. cystic duct

g. bile duct

h. duodenum

i. hepatopancreatic ampulla

j. pancreatic duct

• bile passes down right and left hepatic ducts into common hepatic duct

• common hepatic duct joined by cystic duct to form the bile duct (common bile duct)

• bile duct unites with main pancreatic duct to form hepatopancreatic ampulla

• distal end of ampulla opens into the duodenum at the major duodenal papilla

• sphincter of Oddi surrounds the distal end

Gall bladder

• pear shaped sac

• neck, body, fundus

• function - collect, concentrate, and store bile

• usually holds 30-60 mls of bile

• insert image from slide 34

Anatomical position of gall bladder: location, projections, relations

Location: right hypochondrium

Projects: below inferior margin of liver

Relations:

• Anterior: anterior abdominal wall and liver

• Posterior: duodenum (1st and 2nd parts) and transverse colon

Mucosa, Muscularis, and Outer Layer of Gall Bladder

Mucosa

• many folds, gall bladder is trying to concentrate bile before used in GI tract and that is done by ABSORBING water and the folds allow for more SA → water absorption

• epithelium: simple columnar epithelium with many microvilli

• lamina propria: lots of blood vessels lymphocytes

Muscularis

• longitudinal and oblique fibers

Outer Layer

• mainly serosa but attached to the liver by adventia

Blood supply to the gall bladder comes from ____

the cystic artery, a branch of the right hepatic artery.

Venous drainage of gall bladder

• cystic veins from body and fundus neck drain directly into liver sinusoids

• cystic veins from neck drain directly into liver sinusoids or into hepatic portal vein

Lymphatic drainage of the gall bladder

• Lymph drains to cystic lymph node at the gall bladder neck then to hepatic lymph nodes

• Hepatic nodes → celiac nodes → intestinal trunk → cisterna chyli and thoracic duct

Innervation of gall bladder

• sympathetic innervation: carriers vasomotor fibers

• sympathetic efferents and visceral pain afferents via the greater splanchnic nerve and celiac plexus

• somatic afferents via the phrenic nerve

• parasympathetic innervation: vagus nerve

Anatomical relations of the pancreas

• retroperitoneal

• located in epigastrium and left hypochondrium

• lies transversely across the posterior abdominal wall

• is posterior to the stomach

• lies between duodenum and spleen

Pancreatic functions: exocrine

• tubuloacinar glands containing pyramid shaped acinar cells

• secrete digestive enzymes as pancreatic juice

• secreted into duodenum via intralobular then pancreatic ducts

Pancreatic duct

a. accessory pancreatic duct

b. hepatopancreatic ampulla (ampulla of vater)

c. main pancreatic duct

d. major duodenal papilla

e. minor duodenal papilla

Pancreatic functions: endocrine

• islets of langerhans

• α cells secrete glucagon into blood

• β cells secrete insulin into blood

• δ cells secrete somatostatin into the blood

Pancreatic arterial supply insert image from slide 11

a. celiac trunk

b. common hepatic artery

c. gastroduodenal artery

d. superior pancreaticoduodenal artery posterior

e. superior pancreaticoduodenal artery anterior

f. superior mesentery artery

g. splenic artery

h. greater pancreatic artery

i. inferior pancreaticoduodenal artery

j. aorta

**anastomosis between celiac trunk and SMA

Pancreatic venous drainage

a. hepatic portal vein

b. superior pancreaticoduodenal vein

c. inferior pancreaticoduodenal vein

d. superior mesenteric vein

e. inferior mesenteric vein

f. pancreatic veins

g. splenic vein

Pancreatic innervation

Sympathetic

• abdominopelvic splanchnic nerves and sympathetic chain then celiac plexus and superior mesenteric plexus

• visceral afferent: T6 to T9

• endocrine: cholecystokinin and secretin

Parasympathetic

• vagus nerve then celiac plexus and superior mesenteric plexus

Pancreatic lymphatic drainage

Pancreaticosplenic nodes or pyloric nodes → superior mesenteric nodes or celiac nodes → chysterna chyli and thoracic duct

Duodenum parts. It is mostly retroperitoneal. insert image slide 16

a. intraperitoneal superior part

b. retroperitoneal superior part

c. descending part

d. foregut

e. midgut

f. horizontal (inferior) part

g. ascending part

Duodenum arterial supply image from slide 17

a. celiac trunk

b. common hepatic artery

c. gastroduodenal artery

d/e. superior pancreaticoduodenal artery posterior and anterior

f. superior mesenteric artery

g. aorta

h. inferior pancreaticoduodenal artery (also has anterior and posterior branches)

i. aorta

Duodenum venous drainage image from slide 18

a. splenic vein

b. hepatic portal vein

c. superior pancreaticoduodenal vein

d. inferior pancreaticoduodenal vein

e. superior mesenteric vein

f. inferior mesenteric vein

g. pancreatic veins

Histology of duodenum and specfications

epithelium: simple columnar with goblet cells

Brunner’s glands: submucosal glands that secrete alkaline fluid to neutralize stomach acid and facilitate digestion.

Mesenteries

-A double fold of peritoneum that attaches part of the intestines to the posterior abdominal wall

free mesenteries:

• The mesentery

• mesoappendix

• transverse mesocolon

• sigmoid mesocolon

-the root of the mesentery allows entry and exit of blood and lymph vessels, and nerves

insert image from slide 22

Blood supply to jejunum and ileum

Venous drainage: to superior mesenteric vein and portal system

a. ileocolic artery

b. ileal branch

c. superior mesenteric artery (SMA)

d. jejunal arteries

e. arterial arcades

f. ileal arteries

g. vasa recta (straight arteries)

Innervation of jejunum and ileum

Parasympathetic: posterior vagal trunks

Sympathetic: T8 to T10 then abdominopelvic splanchnic nerves then superior mesenteric ganglion

Visceral afferent: T8 to T10

Histology of jejunum

Plicae circulares: large and tall in jejunum

Few Peyer’s patches

Simple columnar epithelium with goblet cells

Each villus has a core of lamina propria

insert image from 26

Histology of ileum

Plicae circulares: low and sparse in proximal ileum, absent in distal ileum

Many Peyer’s patches

insert image from 28

Villus in jejunum and ileum

• Lamina propria contains extensive capillary network

• This carries nutrients into hepatic portal circulation

• Lacteals transport lipids into lymphatic system

insert image from 29

Lymphatic drainage of ileum and jejunum

venous drainage: to superior mesenteric vein and portal system

a. chyle cistern

b. intestinal lymphatic trunk

c. superior mesenteric lymph nodes

d. superior central lymph nodes

e. mesenteric lymph nodes

f. ileocolic lymph nodes

g. terminal ileum

h. juxta-intestinal lymph nodes

insert image from 30

Large intestine functions

• to absorb water and electrolytes from indigestible intestinal contents

• compact this undigested material for excretion as feces

• reflected in its structure

Structure of the large intestine

A. Taenia Coli

3 thickened bands of longitudinal muscle

B. Semilunar Folds

Folds in between the haustra

C. Haustra

Sacculations of the wall between taenia coli

d. Epiploic Appendages (omental appendices)

Small pouches of fat filled omentum

Which is small / large intestine? Insert image from 33

Small, Large

Crypts of Lieberkuhn insert image from 34

Intestinal glands located in the mucosa of the small intestine, involved in secretion and absorption.

A. Mucous secreting goblet cells, more of them near bases of crypts

B. Absorptive cells, more of them near the lumen

Identify that structure

slide 35 image

Taenia Coli