Note on Source: Moore's Clinically Oriented Anatomy is not in the available textbook library. The detailed anatomical descriptions below are drawn directly from Gray's Anatomy for Students (Gray's), which covers the same regional anatomy content as Moore. The frameworks, blood supply details, clinical correlations, and structural descriptions are equivalent. Where noted, content is referenced to Gray's Anatomy for Students.

The Digestive System - Detailed Anatomy

1. Mouth and oral cavity
2. Pharynx
3. Esophagus
4. Stomach
5. Small intestine (duodenum, jejunum, ileum)
6. Large intestine (cecum, appendix, colon, rectum, anal canal)
7. Accessory organs: Liver, Gallbladder, Pancreas

1. Mouth and Oral Cavity

• Teeth - for mechanical breakdown of food
• Tongue - a muscular organ that manipulates food, assists in swallowing, and carries taste receptors (cranial nerve VII, IX, X supply taste)
• Salivary glands - parotid (CN IX), submandibular, and sublingual glands secrete saliva containing salivary amylase, which begins carbohydrate digestion
• Hard and soft palate - form the roof of the mouth; the soft palate elevates during swallowing to close off the nasopharynx

2. Pharynx

• The oropharynx receives the food bolus from the oral cavity
• The laryngopharynx (hypopharynx) lies behind the larynx and connects to the esophagus below
• During swallowing, the epiglottis folds over the laryngeal inlet and the soft palate closes off the nasopharynx, directing the bolus exclusively into the esophagus
• Muscular action: the superior, middle, and inferior pharyngeal constrictors (innervated by the pharyngeal plexus, CN X) create peristaltic waves to propel food downward

3. Esophagus

Structure

• Cervical - behind the trachea and in front of the vertebral column
• Thoracic - passing through the posterior mediastinum, deviating slightly left before the diaphragm
• Abdominal - the short segment after passing through the esophageal hiatus of the diaphragm (at vertebra TX via the right crus)

Abdominal Esophagus

• Anterior vagal trunk - fibers mostly from the left vagus nerve; rotation of the gut during development moves these to the anterior surface
• Posterior vagal trunk - fibers mostly from the right vagus nerve; moves to the posterior surface

• Esophageal branches from the left gastric artery (from the celiac trunk)
• Esophageal branches from the left inferior phrenic artery (from the abdominal aorta)

Narrowings of the esophagus (clinically important)

1. At the cricopharyngeal sphincter (C6) - upper esophageal sphincter
2. Where the aortic arch crosses it (T4)
3. Where the left main bronchus crosses it (T5)
4. At the esophageal hiatus (T10)

Lower Esophageal Sphincter (LES)

4. Stomach

Overview

Regions (4 parts)

1. Cardia - surrounds the opening of the esophagus (cardial orifice) into the stomach
2. Fundus - the dome-shaped region above the level of the cardial orifice; usually contains swallowed air (the "gastric bubble" visible on X-ray)
3. Body - the largest region of the stomach; contains gastric folds (rugae) that expand with filling
4. Pyloric part - the distal end, divided into:
   • Pyloric antrum - wider proximal portion
   • Pyloric canal - narrower distal portion leading to the pyloric sphincter

Pylorus

Curvatures and Attachments

• Greater curvature (left/inferior border): attachment point for the gastrosplenic ligament and the greater omentum
• Lesser curvature (right/superior border): attachment point for the lesser omentum
• Cardiac notch (cardia incisure): superior angle where the esophagus meets the stomach
• Angular incisure: a bend on the lesser curvature marking the transition from body to pyloric antrum

Arterial Supply to the Stomach

• Left gastric artery (from the celiac trunk) - along the lesser curvature
• Right gastric artery (often from the hepatic artery proper) - along the lesser curvature
• Right gastro-omental artery (from the gastroduodenal artery) - along the greater curvature
• Left gastro-omental artery (from the splenic artery) - along the greater curvature
• Short gastric arteries (from the splenic artery) - to the fundus
• Posterior gastric artery (from the splenic artery - variant, not always present)

Venous Drainage

Innervation

• Parasympathetic: vagal trunks (CN X) - increase motility and secretion
• Sympathetic: from T6-T9 via the celiac plexus - decrease motility, cause vasoconstriction

5. Small Intestine

5a. Duodenum

1. Superior part (1st part) - extends from the pyloric orifice to the neck of the gallbladder, at the level of vertebra LI. It passes anteriorly to the bile duct, gastroduodenal artery, portal vein, and IVC. Clinically called the ampulla or duodenal cap - the most common site of duodenal ulcers
2. Descending part (2nd part) - lies just to the right of midline from the neck of the gallbladder to the lower border of vertebra LIII. Crossed anteriorly by the transverse colon; the right kidney is posterior. Contains the:
   • Major duodenal papilla (ampulla of Vater) - common entrance for the bile and main pancreatic ducts (junction of foregut and midgut lies just below this)
   • Minor duodenal papilla - entrance for the accessory pancreatic duct
3. Inferior part (3rd part) - longest section, crossing the IVC, aorta, and vertebral column. Crossed anteriorly by the superior mesenteric artery and vein
4. Ascending part (4th part) - passes upward on/left of the aorta to approximately the upper border of vertebra LII, terminating at the duodenojejunal flexure. This flexure is supported by the suspensory ligament of Treitz (suspensory muscle of the duodenum) - a peritoneal fold containing smooth muscle

• Branches from the gastroduodenal artery (supraduodenal artery, anterior/posterior superior pancreaticoduodenal arteries)
• Anterior/posterior inferior pancreaticoduodenal arteries from the inferior pancreaticoduodenal artery (branch of the superior mesenteric artery)
• First jejunal branch from the superior mesenteric artery

Clinical: Posterior duodenal ulcers erode the gastroduodenal artery or posterior superior pancreaticoduodenal artery, causing torrential hemorrhage. Anterior ulcers perforate into the peritoneal cavity, causing peritonitis and free subdiaphragmatic gas visible on erect chest X-ray. (Gray's Anatomy for Students, p. 374-375)

5b. Jejunum

• Wider diameter and thicker walls than the ileum
• Prominent plicae circulares (circular mucosal folds) that circle the lumen - these greatly increase absorptive surface area and are visible on barium X-ray
• Less prominent arterial arcades (1-2 tiers)
• Longer vasa recta (straight terminal vessels)
• Less mesenteric fat, so mesenteric windows (translucent areas) are visible

5c. Ileum

• Thinner walls
• Fewer and less prominent plicae circulares
• More arterial arcades (3-5 tiers) and shorter vasa recta
• More mesenteric fat (fewer visible windows)
• Contains Peyer's patches (aggregated lymphoid nodules) - important in immune surveillance

Clinical - Meckel's Diverticulum: A Meckel's diverticulum is a remnant of the proximal yolk stalk (vitelline duct) found on the antimesenteric border of the ileum. It occurs in approximately 2% of the population. It may contain ectopic gastric mucosa, leading to ulceration and hemorrhage. The classic "rule of 2s" - 2% prevalence, within 2 feet of the ileocecal valve, 2 cm long, symptomatic in 2% of cases. (Gray's Anatomy for Students, p. 378)

6. Large Intestine

• Taeniae coli - three bands of longitudinal smooth muscle along the wall
• Haustra - sacculations between taeniae
• Omental (epiploic) appendages - fat-filled peritoneal pouches hanging off the wall

6a. Cecum

6b. Appendix (Vermiform Appendix)

Clinical - Appendicitis: Acute appendicitis is an abdominal emergency caused by obstruction (fecalith or lymphoid hyperplasia) leading to bacterial proliferation and wall ischemia. Pain starts as central periumbilical colicky pain (visceral), then migrates to the right iliac fossa after 6-10 hours (somatic, as parietal peritoneum becomes involved). Treatment is appendectomy. (Gray's Anatomy for Students, p. 381-382)

6c. Colon

1. Ascending colon - passes superiorly from the cecum to the right colic (hepatic) flexure, just inferior to the right lobe of the liver. Secondarily retroperitoneal; paracolic gutters lie lateral to it
2. Transverse colon - passes from the right colic flexure to the left colic (splenic) flexure. Intraperitoneal, suspended by the transverse mesocolon. The left colic flexure is higher, more posterior, and more acute than the right; attached to the diaphragm by the phrenocolic ligament
3. Descending colon - passes from the left colic flexure to the sigmoid colon. Secondarily retroperitoneal
4. Sigmoid colon - S-shaped loop passing from the left iliac fossa to the rectum at vertebra SIII. Intraperitoneal, suspended by the sigmoid mesocolon - the most mobile part of the colon and most common site of diverticular disease

• Ascending and transverse colon: branches of the superior mesenteric artery (ileocolic, right colic, middle colic arteries)
• Descending and sigmoid colon: branches of the inferior mesenteric artery (left colic, sigmoid arteries)
• The marginal artery of Drummond is an anastomotic channel running along the mesenteric border connecting SMA and IMA territories

Clinical - Diverticulosis: The sigmoid colon is the most common site for diverticula, which are mucosal herniations through the muscular wall at sites where blood vessels penetrate (points of weakness). Diverticulitis occurs when these become inflamed/infected, causing left lower quadrant pain. (Gray's Anatomy for Students, p. 388)

6d. Rectum

• Superior rectal artery (from the inferior mesenteric artery)
• Middle rectal artery (from the internal iliac artery)
• Inferior rectal artery (from the internal pudendal artery)

6e. Anal Canal

• Pectinate (dentate) line - the line at the base of the anal columns, marking the embryological junction between endoderm (hindgut) and ectoderm. Above = visceral sensation, columnar epithelium, internal hemorrhoids; below = somatic sensation (pain), squamous epithelium, external hemorrhoids

• Internal anal sphincter - smooth muscle (involuntary), extension of the circular layer of the rectal wall; innervated by autonomic nerves
• External anal sphincter - skeletal muscle (voluntary), three parts (subcutaneous, superficial, deep); innervated by the inferior rectal branch of the pudendal nerve (S2, S3)

7. Accessory Digestive Organs

7a. Liver

• Diaphragmatic surface (anterior, superior, posterior) - convex surface fitting against the diaphragm
• Visceral surface (inferior) - bears impressions of adjacent organs (stomach, duodenum, gallbladder, right kidney, right colic flexure, etc.)

• Falciform ligament - attaches the liver to the anterior abdominal wall; contains the ligamentum teres (obliterated umbilical vein) in its free edge
• Hepatogastric ligament - connects liver to stomach (part of lesser omentum)
• Hepatoduodenal ligament - connects liver to duodenum; contains the portal triad (portal vein, hepatic artery proper, common bile duct) in its free edge - the key content of the lesser omentum's free margin
• Coronary and triangular ligaments - attach liver to the diaphragm; between the layers is the bare area (no peritoneal covering)

7b. Gallbladder and Biliary System

• Fundus - rounded end projecting below the liver edge, related to the tip of the 9th costal cartilage
• Body - the main part, resting on the transverse colon and duodenum
• Neck - tapers into the cystic duct; a mucosal spiral fold (spiral fold/valve of Heister) helps regulate bile flow

• Right and left hepatic ducts - drain respective lobes and unite to form the common hepatic duct
• Cystic duct - connects the gallbladder to the common hepatic duct
• Common bile duct (CBD) - formed by the union of the common hepatic and cystic ducts; travels in the hepatoduodenal ligament, passes posterior to the duodenum and through the head of the pancreas, then joins the main pancreatic duct to form the hepatopancreatic ampulla (ampulla of Vater), which opens at the major duodenal papilla in the 2nd part of the duodenum
• Sphincter of Oddi (hepatopancreatic sphincter) - controls flow of bile and pancreatic juice into the duodenum

Clinical - Gallstones: Gallstones passing into the CBD can obstruct the sphincter of the ampulla, blocking bile flow and causing obstructive jaundice. If they obstruct the pancreatic duct outlet as well, gallstone pancreatitis results. ERCP can be used to remove such stones. (Gray's Anatomy for Students, p. 401-403)

7c. Pancreas

1. Head - the widest part, nestled in the C-shaped curve of the duodenum; the uncinate process is a projection from the lower head that extends behind the superior mesenteric vessels
2. Neck - a constricted part anterior to the portal vein and superior mesenteric vessels; the portal vein is formed behind the neck
3. Body - passes to the left across the vertebral column (anterior to the aorta and left kidney); the transpyloric plane (L1) passes through the neck/body junction
4. Tail - the left end, which is intraperitoneal in the splenorenal ligament and contacts the hilum of the spleen

• Main pancreatic duct (duct of Wirsung) - runs through the full length of the gland and joins the CBD at the ampulla of Vater
• Accessory pancreatic duct (duct of Santorini) - drains the upper head; opens separately at the minor duodenal papilla

• Head: anterior/posterior superior pancreaticoduodenal arteries (from the gastroduodenal artery) and anterior/posterior inferior pancreaticoduodenal arteries (from the SMA)
• Body and tail: dorsal pancreatic artery and great pancreatic artery (from the splenic artery); these anastomose via the inferior pancreatic artery

• Alpha cells - glucagon
• Beta cells - insulin (most abundant)
• Delta cells - somatostatin

Clinical - Pancreatic Cancer: Most common in the head and neck. Obstruction of the bile duct produces painless progressive obstructive jaundice (Courvoisier's sign). The "silent killer" because it presents late. Surgical resection (Whipple procedure - pancreaticoduodenectomy) is the only curative option but most tumors have already invaded the portal vein or superior mesenteric vessels at presentation. (Gray's Anatomy for Students, p. 398)

Summary Table: Blood Supply

Summary Table: Peritoneal Relationships