Block 3 Study Guide

What are the superior 3 regions of the abdomen?

Right Hypochondriac Region

Epigastic Region

Left Hypochondriac Region

What are the 3 middle quadrants of the abdomen?

Right Lumbar Region

Umbilical Region

Left Lumbar Region

What are the 3 inferior quadrants of the abdomen?

Right Iliac Region

Hypogastric Region

Left Iliac Region

What are the muscles found in the lateral muscle group?

External Abdominal Oblique

Internal Abdominal Oblique

Transverse Abdominis

(superficial → deep)

What are the muscles found in the medial muscle group?

Rectus Abdominis and Pyramidalis

What is the innervation of the lateral and medial muscle groups?

The 6 lower intercostal nerves and L1

What is the origin of the inguinal ligament?

External Abdominal Oblique muscle, SPECIFICALLY the lowest potion of the aponeurosis

What is the innervation of the cremaster muscle?

The genital branch of the genitofemoral nerve

What is the origin of the cremaster muscle?

Lowest and most caudal part of the Internal Abdominal Oblique muscle

Clinical Significance of the Cremaster Muscle

No pathology

Can palpate region to test for trauma to the testes or testicular torsion

Sensory → Femoral branch of the Genitofemoral nerve (Afferent Limb)

Motor → Genital branch of the Genitofemoral nerve to the Cremaster muscle (Efferent Limb)

What is the location of the rectus sheath?

Surrounding the rectus abdominis both anteriorly and posteriorly

External Abdominal Oblique goes anteriorly

Internal Abdominal Oblique and Transverse Abdominis goes posteriorly

What are the contents of the rectus sheath?

Rectus Abdominis muscle, Inferior and Superior Epigastric Vessels, and Intercostal nerves (the 5 lower ones, including the subcostal nerve)

Importance of the rectus sheath

holds up the major abdominal structures

What are the contents of the inguinal canal?

Males → Spermatic Cord

Females → Round Ligament of the Uterus Lymphatics

What is the location of the inguinal canal?

Deep inguinal ring is the internal opening and is a gap in the fascia transveralis

Superficial inguinal ring is a gap in aponeurosis of the external abdominal oblique muscle

Clinical Significance of Cryptorchidism

When the testes fail to descend

Human testes are very temperature sensitive as they’re typically held 5-7 degrees C colder than the body. If the testes are left in the body, the tissue could become corrupted and turn into cancer. This is taken care of quickly at the time of birth

Clinical Significance of hydrocele of the cord

Process Vaginalis fails to close after testes have descended, causing fluid to form around the spermatic cord

What are the contents of the spermatic cord?

Ductus (vas) Deferens

Testicular Artery, Artery of the Ductus Deferens, and Cremaster Artery

Pampiniform Plexus

Autonomic Nerve Fibers

Genital branch of the Genitofemoral Nerve

Lymphatics

Cremaster Muscle

Direct Inguinal Hernia

You can palpate the mass and it’s super soft (it’s a loop of intestine), it can also be pushed in. Generally does not require surgery. Patient may be able to go on bed rest or put into a binding (brace), which can cause it to heal on its own. A doctor might want to do surgery though, depending on the patient, they may be put into a mesh

Unique characteristics of a Direct Inguinal Hernia

Medial to epigastric vessels don’t pass through the inguinal canal (parallels spermatic cord)

Low risk of strangulation/infarction

Almost always acquired

Middle age (greater than 40 y/o)

Smaller in size

Occurs within Hesselbach’s Triangle

Generally does not need surgery

Indirect Inguinal Hernia

Comes through the abdominal wall inside the spermatic cord, so surgery is required to pull the loop of intestine back out and let it free into the abdominal cavity

Unique characteristics of the Indirect Inguinal Hernia

Lateral to epigastric vessels

Passes through the inguinal canal (inside spermatic canal)

High risk of strangulation/infarction

Congenital and Acquired

In younger people

Bigger in size

Always requires surgery

What organs are characterized as intraperitoneal?

Stomach

Small Intestine (Jejenum, Ileium, Part of the superior part of Duodenum)

Liver
Gallbladder

Cecum with Vermiform Appendix (portions of variable size may be retropertioneal)

Large Intestine (Transverse and Sigmoid Colons)

What does it mean for an organ to be intraperitoneal?

They have a mesentery and are completed covered by the peritoneum

What does it mean for organs to be retroperitoneal?

They have no mesentery or lost it during development

What organs are categorized as retroperitoneal?

Kidneys

Suprarenal Glands

Uterine Cervix

Duodenum (Descending, Horizontal, and Ascending)

Pancreas

Ascending and Descending Colon

Rectum (upper 2/3)

Clinical Significance of the Lesser Sac

Lies posterior to the stomach and you can get entrance into it by the epiploic foramen. The site of internal herniation and strangulation of part of the intestine into the leser sac. Surgery should be done from the other side (into the sac), not touching the porta hepatis. The cystic artery of the gallbladder can be reached through this foramen

Clinical Significance of Peritoneal Spaces and Compartments

Can get an increase in fluid in the abdomen, post-op, we can see it’s just a consequence or a side effect of inhaled anesthetic, we can get an increase in serous fluid production in the abdomen. Not a big deal, but it can sit in the subphrenic space and cause it to be irritated. In a patient in the elderly population, this can lead to development respiratory problems in a post-op environment. Up and moving helps prevent this. Adhesions form, move the fluid around and it can become an irritant.

Peritonitis, Ascites, Paracentesis

What is the importance of the Greater Omentum

1. Prevents the visceral peritoneum to adhere to the parietal peritoneum

2. Has considerable mobility and moves by peristaltic movements of the viscera

3. Contains fat and lymphocytes and other cells to protect against infection or inflammatory conditions in the abdominal cavity

   1. AKA the abdominal policeman

4. Moves towards the inflamed or infected area (for example: Appendicitis)

5. Protects abdominal organs against injury and acts as an insulator against loss of body heat

Peritonitis

The inflammation (alongside pain) of the peritoneum following an abdominal injury

Example: Stab wound or a perforated appendicitis

Ascites

Abnormal accumulation of fluid in the abdominal cavity, commonly seen in liver cirrhosis

Paracentesis

Puncturing the peritoneal cavity to aspirate fluids

Structures/Organs found in the Foregut

Esophagus and stomach down to the 2nd part of the duodenum, including the liver, biliary system, gallbladder, and pancrease

Structures/Organs found in the Midgut

Starts from the lower half of the 2nd part of the duodenum and jejunum, ileum, colon (cecum, ascending, and the right 2/3 of the transverse colon)

Structures/Organs found in the Hindgut

Left half of the transverse colon, descending colon, sigmoid colon, rectum, and the upper part of the anal cavity

Blood Supply of the Foregut

Celiac Trunk

Blood Supply of the Midgut

Superior Mesenteric Artery

Innervation of the Foregut and Midgut

Parasympathetic → Vagus Nerve

Sympathetic → T5-L2

Blood Supply of the Hindgut

Inferior Mesenteric Artery

Innervation of the Hindgut

Parasympathetic → Pelvic Splanchnic Nerves (S2-S4)

Sympathetic → T5-L2

Blood Supply of the Esophagus

Upper part (cervical portion): by the inferior thyroid artery

Lower part includes: abdominal portion, left gastric artery (from celiac artery) and inferior phrenic artery (from abdominal aorta)

Venous Drainage of the Esophagus

Inferior thyroid vein, azygos, hemiazygos, and gastric veins

Gastric veins drain into the portal vein; therefore, this is a link between portal and the systemic circulation (portocaval anastomosis)

This results in ESOPHAGEAL VARICES in liver cirrhosis

Clinical Significance of Esophageal Varices

When the liver is compromised, blood gets congested because of huge fibroids in the liver. It prevents blood from flowing, so it backs up into the portal vein, which results in portal hypertension. Portal vein is pushed and gaped open, making blood plasma and formed elements get pushed into the abdominal cavity (ascites), making all other veins dilated. If the stomach drains into the portal vein, blood will back up into its veins, congesting it. In the areas with portocanal anastomosis, if blood backs up, blood will go into the lower esophagus because it’s being backed into the gastral vein. However, you can “flip the switch” and have the blood drain into the caval system instead

What is the histology of the esophagus

1. Mucosa

2. Submucosa

3. Tunica Muscularis

4. Adventitia/Serosa

Mucosa

Always lined with epithelial cells, has a layer of connective tissue containing capillaries and a thin layer of smooth muscle

Submucosa

Connective tissue containing blood vessels, lymphatics, and nerve fibers

Muscularis Externa

2 layers of smooth muscle: the circular layer squeezes the tube and the longitudinal layer shortens it

Serosa/Adventitia

Connective tissue that binds the structure to surrounding structures

What type of epithelium lines the oral cavity to the esophagus?

Stratified non-keratinized squamous epithelium

What type of epithelium lines the stomach to the upper anal canal?

Simple columnar

What type of epithelium lines below the prectinate line?

Stratified non-keratinized squamous epithelium

Clinical Significance of Zenker’s Diverticulum

Upper esophagus, dysphagia, and halitosis

Complications include ulceration, bleeding, inflammation

Surgery

Food can get trapped in here

What is diverticulum of the esophagus?

All 3 wall layers protruding to form little pouches

Clinical Significance of Aschalasia

AKA Cardiospasm

Retrosternal pain, neuromotor disorder of the lower esophageal sphincter (LES), decreased cells in the mycentric plexus (analogous to Hirschsprung’s Disease), dysphagia for solids and liquids, dilated proximal esophagus and aperistalsis, and increased LES pressure.

Treated case by case: If LES closes but can be opened, go to a hospital for mechanical assistance. If LES can’t be opened, soft foods, liquid diet, feeding tube. If stimulation can be attempted, it is due to a stroke or trauma, do physical therapy

Clinical Significance of Barret’s Esophagus

Columnar cell metaplasia of the squamous epithelium due to acid injury. Caused by chemical burns. Lower Esophageal Sphincter isn’t closing as it should. Can cause damage/erosion to tissue, chronic inflammation, etc

Importance of stomach rugae

Expands the stomach

Importance of the oblique muscle layer of the stomach

Allows for churning of the stomach

What are the gastric pits

Shallow part of the gastric mucosa. All you’ll see are mucus cells, the same simple columnar epithelium

What are gastric glands?

Deep part of the gastric mucosa. Cells become more specialized

What three types of cells would you find in the gastric glands within the body and fundus of the stomach?

1. Mucoid

2. Chief

3. Parietal

Mucoid Cells

Secretes mucus to protect the gastric mucosa

Chief Cells

Synthesizes and secretes pepsinogen, a protein splitting enzyme activated by HCl of the stomach into pepsin

Parietal Cells

Synthesizes and secretes HCl and intrinsic factor for B12 absorption in the ileum

What enteroendocrine cell would you find within the gastric glands in the pyloric antrum?

G Cells

G Cells

ONLY LOCATED IN THE PYLORUS AND PYLORIC ANTRUM

Secretes gastrin, a hormone that targets parietal cells and it stimulates them to secrete even more acid and mitotic growth

Blood supply of the stomach

1. Left Gastric Artery

2. Common Hepatic Artery branches to the Right Gastric Artery

3. Common Hepatic Artery branches to the Gastroduodenal Artery branches to the Right Gastroepiploic Artery

4. Splenic Artery branches to the Short Gastric Artery and the Left Gastroepiploic Artery

Venous Drainage of the stomach

Via Portal Vein directly (Left and Right Gastric Vein) or indirectly through the Splenic Vein (the Left Gastroepiploic Vein and Short Gastric Vein).

The Right Gastroepiploic Vein goes to the Superior Mesenteric Vein

Innervation of the Stomach

Parasympathetic → Vagus Nerve

Sympathetic →

1. Mostly coming from SPLACHNIC NERVES (innervating organs S2-S4), also from upper lumbar, which synapse in the celiac ganglion.

2. Postganglionic fibers innervate the _____ to inhibit peristalsis and gastric secretion, and cause pyloric contractions. Also conveys pain

Clinical Significance of Gastric Ulcers

No Acid, No Ulcer.

Due to defective mucosal barrier, including the same causes of gastritis, most common on the lesser curvurature. Has a pain which increases when eating

Clinical Significance of Vagotomy

Used for treating gastric ulcers that are not responding to drugs. Perforation of gastric ulcers is common but if a posterior Gastric Ulcer perforates, it can involve the pancreas resulting in returned pain to the back. Erosion of the splenic artery results in hemorrhage into the peritoneal cavity. ELIMINATES THE NEURAL STIMULATION OF GASTRIC SECRETION. THE PROCECURE IS KNOWN TO HAVE COMPLICATIONS WITH GASTRIC EMPTYING

Clinical Significance of Hemigastrectomy

Part of the stomach gets removed. Could potentially perform a pylorectomy: removes G cells (that secretes gastrin). Controls acid secretion.

How are Gastric Ulcers, Vagotomy, and Hemigastrectomy connected?

Vagotomy and Hemigastrectomy can treat Gastric Ulcers

Clinical Significance of Sliding Hiatal Hernias

When abdominal part of the esophagus and cardia and even part of the fundus slide up through the esophageal hiatus. REGURGITATION AND HEART BURN. Puts pressure on the lower esophageal sphincter and pushes it open

Clinical Significance of Paraesophageal Hiatal Hernias

Cardia doesn’t move but part of the fundus and peritoneum passes through the esophageal hiatus. USUALLY NO REGURGITATION

Treatment for Sliding and Paraesophagel Hiatal Hernias

1. Surgery

   1. Reinforces barrier to reflux that the Left Esophageal Valve normally provides. In most cases, the operation performed to correct is called “fundoplication” → the upper portion of the stomach (fundus) is wrapped (plicated) around the lower portion of the esophagus and anchored securely below the diaphragm

2. Radiofrequency

   1. Using an endoscope supplied by electrodes. Radiofrequency energy causes tiny burns at the G-E junction that heal and form scar tissue that actually tightens the weak valve

Clinical Signficance of Hypertrophic Pyloric Stenosis

Progressive hypertrophy of circular muscles in pyloric sphincter, causing a narrowing pyloric lumen which may obstruct food passage. This may happen in infant males (1st child usually), which is associated with projectile, NONBILIOUS VOMITING after feeding. Palpation reveals a small knot (olive sized mass) at the Right Costal Margin.

Treatment includes longitudinal pyloromyotomy, leaving the mucosa intact

Function of the Duodenum

1. Regulates stomach and gallbladder emptying in response to acidic chyme

2. Secretes secretin due to increased acid and fatty acids in its lumen

   1. Secretin inhibit the gastric acid secretion

3. Secretes cholecystokinin (CkH) in response to fatty chyme which induces gallbladder contraction

4. Secretes the Enterogastrone that inhibits stomach peristalsis

First Part of the Duodenum

Superior Duodenum

5 cm long, between T12-L1

Anterior to Portal Vein and Common Bile Duct

Duodenal cap: site of ulcers

Second Part of the Duodenum

Descending Duodenum

WHERE EVERYTHING HAPPENS!

7.5 cm long until lower level L3

Contains the MAJOR DUODENAL PAPILLA, a common opening for the Common Bile Duct and the main opening (aka Hepatopancreatic AMPULLA OF VATER).

The MINOR DUODENAL PAPILLA, superior to the major opening, is an opening of the accessory pancreatic duct

Third Part of the Duodenum

Horizontal Duodenum

10 cm at L3 level

Anterior to the IVC and abdominal aorta

Crossed by the superior mesenteric artery and vein anteriorly

Fourth Part of the Duodenum

Ascending Duodenum

2.5 cm

Travels across the midline to the duodenojejunal flexure at L1-L2

The beginning of the 1st part and part of the 4th part are covered by the peritoneum (have some mobility), while the rest of the duodenum isn’t mobile

Function and Innervation of the Submucosal Plexus of Meissner

Parasympathetic

Secretomotor function that produces mucus for lubrication and facilitates molecule movement

Function and Innervation of the Myenteric Plexus of Auerbach

Parasympathetic

Peristaltic movement of smooth muscle

Function of Jejunum and Ileum

Absorption of the digested food

(Folate in Jejunum, B12 in Ileum)

ONLY ESSENTIAL AREA IN THE GI TRACT THAT’S ESSENTIAL FOR LIFE

Unique Characteristics of the Jejunum

1. Lies mostly in upper quadrant

2. More vascular

3. Red color

4. Thick wall

5. Long vasa recta

6. Less arcades

7. Less fat

8. Window in mesentery

9. No or very few Peyer’s patches

10. Large and many circular folds (plica circulare)

Unique Characteristics of the Ileum

1. Lies mostly in lower quadrant

2. Less vascular

3. Pink color

4. Thin wall

5. Short vasa recta

6. More arcades

7. More fat

8. No window in mesentery

9. Many Peyer’s patches

10. Low and fewer circular folds (plica circulare)

Blood Supply of the Small Intestine

Arteries: Branches of the Superior Mesenteric Artery

Venous Drainage of the Small Intestine

Veins: Superior Mesenteric Veins into the Portal Veins

Innervation of the Small Intestine

Sympathetic → Splanchnic Nerves (Inhibition of peristalsis and contraction of the ileocecal sphincter and vasoconstriction of vessels)

Parasympathetic → Vagus Nerve (causes peristalsis and glandular secretion)

Clinical Significance of Meckel’s Diverticulum

An ileal out-pocketing typically located within 50-75 cm (40 in newborns) of the ileocecal valve. this is a congenital anomaly resulting from persistence of the vitelline (omphalomesenteric) duct. It might be free (74%) or attached by a chord to the umbilicus. May mimic pain of appendicitis. About ½ of them cause ulceration, inflammation, and GI bleeding because of the presence of ectopic acid-secreting gastric epithelium; pancreatic tissue may also be present there.

Rule of 2s: Occurs in about 2% of children, 2 feet from the ileocecal valve, containing 2 types of ectopic mucosa (gastric and pancreatic), usually occurs at 2 years old

Treatment → Remove and repair

Location of Vermiform Appendix

On the posteromedial below the ileocecal junction

Function of the Vermiform Appendix

Shrinks in length and diameter as we age. has a very high concentration of E. coli. If a human faces an “insult” to their large intestine (diarrhea, stress, diets, infections, food poisoning, etc.), a lot of the E. coli is lost. But it can be easily replaced due to storage of E. coli in the appendix. Gut microbiome is so important → byproduct of E. coli is vitamin K (important for clotting factors). Unsure of true function though

Clinical Significance of an Appendicitis

May be occluded by a fecalith or inflammation and edema of the lymphatic tissue leading to acute and chronic appendicitis. Pain is pre-umbilical at T10 (dermatome) and sympathetic. Appendectomy using the McBurney’s point between the umbilicus and Right Anterior Superior Iliac Spine (junction between Right 1/3 and Mid 1/3). the iliohypogastric nerve should be saved, if not, muscle weakness can occur and direct inguinal hernia.

Early stages lead to Appendiceal Distention, which is the irritation of the lining of abdominal and pelvic cavities, which lead to perforation

Venous Drainage of the Colon

NOT RECTUM, but colic veins → superior mesenteric veins to the portal veins

Blood Supply of the Colon

Branches of the superior and inferior mesenteric arteries

the MARGINAL ARTERY OF DRUMMOND is an anastomosis of the superior and inferior mesenteric arteries. it’s an important anastomosis if a portion of the arteries are bleeding

Clinical Significance of the Pectinate Line of the Anal Cavity

Separation of the upper and lower anal canal

The inferior comb shaped limit of the anal valves. When fecal matter reaches this point, it gives the body the urge to use the bathroom

Blood Supply of the Rectum and Anus

1. Superior Rectal Artery

   1. Final branch of the inferior mesenteric artery supplies the superior rectum

2. Middle Rectal Artery

   1. From internal ilia artery supplies the middle

3. Inferior Rectal Artery

   1. A branch of the internal pudendal artery which is also coming from the internal iliac artery that supplies the lower part of the rectum

Venous Drainage of the Rectum and Anus

Superior → inferior mesenteric vein then into the portal vein

Middle/Inferior → internal iliac vein (portocaval anastomosis)

Innervation of the Rectum and Anus

Sympathetic → Lumbar part of trunk through superior hypogastric plexus

Parasympathetic → S2-S4, pelvic splanchnic nerve

Clinical Significance of the Portocaval Anastomosis

Only significant in patients with cirrhosis of the liver. When we have a compromised liver, we force blood into the caval system by putting it into the azygos vein. the blood gets pushed lower into the rectum and drained through the caval system, causing internal hemorrhoids