GI Tract

How long is the digestive tract?

Approx. 8m long

What is the digestive tract also called?

Alimentary tract

What is the gastrointestinal tract?

The part of the digestive system below the diaphragm

What are the main parts of the digestive system?

• Mouth

• Pharynx

• Esophagus

• Stomach

• Small & large intestines

• Digestive glands

What does the esophagus do?

Transports food from the pharynx to the stomach

Why does the cardiac orifice remain closed?

To prevent gastric acid from moving into the esophagus

What type of organ is the stomach?

• Large

• Smooth muscle

• Contains rugae

What are the two surfaces of the stomach?

Greater & lesser curvatures

What supports the stomach?

Ligaments attached to its curvatures

What are the three parts of the stomach?

• Fundus

• Body

• Pylorus

What connects the stomach to the proximal duodenum?

The pyloric canal

What controls the pyloric canal?

The pyloric sphincter

How long is the small intestine?

5 m

What is the diameter of the small intestine?

4 cm

What are the three parts of the small intestine?

• Duodenum

• Jejunum

• Ileum

What is the mesentery?

A parietal peritoneal projection attaching the small intestine to the posterior abdominal wall

What shape is the duodenum?

C-shaped

How many segments does the duodenum have?

4

What is the first segment of the duodenum?

Superior segment, or duodenal bulb

Is the first segment of the duodenum peritoneal or retroperitoneal?

Peritoneal

Where does the first segment of the duodenum begin and end?

From the pylorus to the neck of the gallbladder

What is the second segment of the duodenum?

Descending

Is the second segment of the duodenum peritoneal or retroperitoneal?

Retroperitoneal

What is the third segment of the duodenum?

Transverse

Is the third segment of the duodenum peritoneal or retroperitoneal?

Retroperitoneal

What is the fourth segment of the duodenum?

Ascending

Is the fourth segment of the duodenum peritoneal or retroperitoneal?

Retroperitoneal

What holds the fourth duodenal segment in place?

The ligament of Treitz

What is the jejunum?

The second segment of the small intestine

What structures in the jejunum help with food absorption?

Valvulae conniventes

What is the ileum?

The lower segment of the small intestine

What does the ileocecal orifice do?

Join the ileum to the large intestine & prevents retrograde food flow

How does the large intestine compare with the small intestine in diameter and length?

It’s larger in diameter & shorter in length

What are the 5 parts of the large intestine?

• Vermiform appendix

• Cecum

• Ascending, Transverse, Descending

• Rectum

• Anus

What gives the large intestine its segmented appearance?

Hasutra

What arteries supply the esophagus?

• Inferior thyroid artery

• Descending thoracic aorta

• Gastric branch of celiac axis

Where may varices arise in the esophagus?

From gastroesophageal arteries

What arteries supply the stomach?

• Right & left gastric arteries

• Hepatic artery

• Splenic artery

What supplies the duodenum?

Branches of the celiac axis

What supplies the small intestine?

SMA

Which arteries supply the large intestine?

• Celiac axis

• SMA

• IMA

What is the largest endocrine organ in the body?

The GI tract

What are the two primary functions of the GI tract?

Digestion & absorption

What does the esophagus transport?

Macerated (chewed) food from the mouth to the stomach

How do the stomach's rugae help digestion?

They allow the stomach to stretch for food intake

What is the function of the stomach's three smooth muscle layers?

Churn food & mix it with digestive juices/enzymes

What moves chyme toward the pylorus and into the small intestine?

Peristalsis

What is the function of villi in the small intestine?

Increase surface area for digestion & absorption

Where does most digestion occur?

In the duodenum

What do bile and pancreatic enzymes do in the duodenum?

Break down food particles for absorption

Where do absorbed nutrient molecules go?

Into the blood & lymph systems

What do the large intestines do with undigested chyme?

Process it into stool

Where are sodium and water reabsorbed?

In the cecum

What are common signs and symptoms of GI problems?

• Nausea

• Vomiting

• Diarrhea

*Fever & abdominal pain can occur

How many layers does the bowel have?

5

Which bowel layers are echogenic?

The odd-numbered layers: 1, 3, & 5

Which bowel layers are hypoechoic?

The even-numbered layers: 2 & 4

What is the first bowel layer?

Mucosa

What does the mucosa contact?

The intraluminal contents

What is the second bowel layer?

Submucosa

What does the submucosa contain?

Blood vessels & lymph channels

What is the third bowel layer?

Muscularis

What fibers does the muscularis contain?

Circular & longitudinal bands of fibers

What is the fourth bowel layer?

Serosa

What is the serosa made of?

Thin layers of connective tissue

What is the fifth bowel layer?

Mesothelium

What does the mesothelium cover?

Intraperitoneal bowel loops

What does GEJ stand for?

Gastroesophageal junction

How does the GEJ appear sonographically?

As a bulls-eye or target

Where is the GEJ located relative to the aorta?

Anterior

Where is the GEJ located relative to the left liver lobe?

Posterior

Can the small intestine usually be seen with sonography?

No

How do the valvulae conniventes appear sonographically?

Linear echogenic densities

• Spaced 3–5 mm apart

What is the sonographic appearance of the valvulae conniventes called?

Keyboard sign

What is the normal wall thickness of the ileum?

< 3 mm

How does the ileum's wall appear?

Smooth-walled

What is the vermiform appendix?

A remnant of the apex of the cecum

Where can the appendix lie superiorly?

Behind the cecum

Where can the appendix lie medially?

Behind the ileum and mesentery

Where can the appendix lie in the pelvis?

Downward & medially into the true pelvis

Under which landmark is the appendix located?

McBurney's point

How is McBurney's point located?

• Draw a line from the right anterosuperior iliac spine to the umbilicus

• Midpoint = root of appendix

What is the normal colon wall thickness?

4 mm

What five layers are listed for the colon?

• Two mucosal

• Submucosa

• Muscularis propria

• Subserosal fatty tissue