Comprehensive Study Guide to Abdominal Anatomy and Gastrointestinal Physiology

Course Introduction and Semester Schedule

• Course Context: Part 3.3, Cardiovascular System (Note: The content focuses primarily on the Abdominal/Gastrointestinal system within this module). Led by B.O Rump, MD PhD.

• Key Reference Texts:

  • Life: The Science of Biology (D. Sadava, et al.), Chapter 49.

  • Gray's Anatomy for Students, Chapter 4 (Abdomen).

  • Acland's Video Atlas of Human Anatomy.

Weekly Schedule (Weeks 9–15)

• Week 9, Session 2 (Thursday): Introduction to Abdomen, Peritoneum, and Stomach Function. Start using Acland's Video Atlas ($5.2.15$).

• Week 10: No classes on Monday ($6/4/26$). Thursday focuses on Introduction, Peritoneum, and Stomach Anatomy ($5.2.1$).

• Week 11, Session 1 (Monday, 13/4/2026): Small Intestine and Development. Acland videos up to $5.2.5$ (Omentum development) and $5.2.6$ (Duodenum). Pre-class open-book Moodle quiz required.

• Week 11, Session 2 (Thursday): Anal Canal (up to $5.2.14$) and Gray's Chapter 4.

• Week 13, Session 1 (Monday, 27/4/26): Accessory Organs and Vascular Supply. Acland videos $5.2.22$ (Review of liver, pancreas, spleen) and $5.2.16$ to $5.2.21$ (Spleen).

• Week 13, Session 2 (Thursday): Student pitches on intersex presentations; preparation for Dissection Room and Anatomical Museum visit.

• Catch-up Week: Wednesday ($6/5/2026$) features the Guided Anatomy Practical in the Dissection Room and Museum.

• Week 14, Session 1 (Monday, 11/5/2026): Debriefing and group discussion regarding encounters with human remains.

• Week 14, Session 2 (Thursday): Optional individual debriefing session; reflection report on dissection room visit due pre-class.

• Week 15, Session 1 (Monday, 18/5/2026): Assessment 3.

• Week 15, Session 2 (Thursday): Last day of semester; presence is mandatory.

Student Learning Outcomes (Part 4: Abdomen)

1. Surface Projections and Regions

• Demonstrate surface projections of abdominal organs onto the four quadrants and the nine descriptive regions of the abdomen.

• Precisely locate the liver, gallbladder, pancreas, spleen, kidneys, stomach, duodenum, jejunum, and ileum via surface projection.

• Describe the caecum and appendix.

2. Peritoneum and Mesenteries

• Understand the organization and clinical significance of the parietal and visceral peritoneum.

• Identification of the greater and lesser sacs, mesenteries, and peritoneal ‘ligaments.’

• Explain the clinical significance of the attachments of the ascending and descending colon to the posterior abdominal wall.

3. Functional Anatomy and Innervation

• Analyze the functional anatomy of small and large bowel mesenteries.

• Understand the role of the visceral peritoneum in referred pain, including the specific nerve supply of both parietal and visceral layers.

4. Vascular System

• Describe the origins, courses, and major branches of the abdominal aorta.

• Discuss the clinical significance of abdominal blood supply, specifically in the context of abdominal aneurysm repair.

• Describe the origin and course of the inferior vena cava (IVC) and its major tributaries.

Digestive Tract Overview and Energy Consumption

• The Disassembly Line: The vertebrate gastrointestinal system functions as a disassembly line to break down food into usable materials for energy and biosynthesis.

• Anatomical components of the system:

  • Mouth, Teeth, Tongue.

  • Salivary glands: Parotid, Sublingual, and Submandibular.

  • Esophagus and Diaphragm.

  • Stomach and Pancreas.

  • Liver and Gallbladder.

  • Small Intestine: Duodenum, Jejunum, Ileum.

  • Large Intestine (Colon): Ascending, Transverse, Descending colon, Rectum, and Anus.

  • Appendix.

Energy Expenditure (Food vs. Activity)

• 6 oz Low-fat Strawberry Yogurt ($130\,Calories$): Requires $90\,min$ of resting, $26\,min$ of walking, or $13\,min$ of jogging to burn.

• Turkey Sandwich (White meat, $215\,Calories$): Requires $144\,min$ of resting, $43\,min$ of walking, or $22\,min$ of jogging.

• 1/4 pound Fast-food Cheeseburger ($530\,Calories$): Requires $354\,min$ of resting, $106\,min$ of walking, or $54\,min$ of jogging.

• 10" Deep-dish Cheese Pizza ($1,300\,Calories$): Requires $864\,min$ of resting ($14.4\,hours$), $258\,min$ of walking, or $132\,min$ of jogging.

Undernutrition and Energy Reserves

• Global Survival: A person of average body weight can survive approximately $4$ to $5\,weeks$ without food due to fat reserves.

• Energy Depletion Sequence:

  • Carbohydrates: These reserves are the first to go, typically depleted after only a single day without food intake.

  • Fat: The major energy reserve ($10–12\,kg$ in typical storage).

  • Protein: Once body fat is exhausted, protein is lost at an accelerating rate, leading to serious physiological consequences.

Essential Nutrients for Biosynthesis

1. Amino Acids

• Humans can synthesize some carbon skeletons for amino acids, but 8 essential amino acids must be obtained through diet.

• The 8 essential amino acids for adults: Tryptophan, Methionine, Valine, Threonine, Phenylalanine, Leucine, Isoleucine, and Lysine.

• Dietary Sources: Grains (e.g., corn) and Legumes (e.g., beans) are complementary; together they provide all 8 essential amino acids for those on vegetarian diets.

2. Fatty Acids

• Linoleic acid is an essential fatty acid required to synthesize other unsaturated fatty acids, including membrane phospholipids and signaling molecules.

3. Minerals

• Macronutrients: Elements required in large amounts (e.g., Calcium).

• Micronutrients: Elements required in tiny amounts (e.g., Iron).

• Common Deficiency: Iron deficiency leads to anemia, which is the most common mineral deficiency globally.

4. Vitamins

• Vitamins are carbon compounds required for growth and metabolism that the body cannot synthesize (mostly acting as coenzymes).

• Humans require 13 vitamins.

• Water-soluble vitamins: Excess is eliminated via urine (e.g., Vitamin C).

• Fat-soluble vitamins: Can accumulate to toxic levels in the liver and body fat (e.g., Vitamin A, D, E, K).

• Vitamin D (Calciferol): Often considered a hormone because the body can synthesize it when UV light hits the skin, converting certain lipids into the vitamin. It is essential for calcium absorption.

Anatomy and Physiology of the Gut

The Interior "Outside"

• The gut is a tube where the lumen is considered an external environment (‘an outside inside the body’).

• Microbiota: The population of microorganisms (mostly bacteria) colonizing the gut.

• Microbiome: The cumulative genomes of these microorganisms.

• Function of Microbiota: They obtain nutrition from passing food and contribute to host digestion, specifically producing Vitamin K (crucial for blood clotting and bone support) and Vitamin B7 (Biotin).

Maximizing Surface Area for Absorption

• The small intestine uses structural hierarchies to increase absorptive area:

  1. Sheer length of the tubular intestine.

  2. Intestinal folds of the lining.

  3. Villi: Fingerlike projections on the folds.

  4. Microvilli: Microscopic projections covering the epithelial cells of the villi, creating a ‘brush border.’

Gut Protection: Immune Defense

• Because the gut contains dangerous acid, enzymes, and bacteria, it is protected by:

  1. Mucosal lining.

  2. Peyer's Patches (Gut-associated lymphoid tissue / GALT): Aggregated lymphoid nodules containing macrophages, dendritic cells, B-lymphocytes, and T-lymphocytes.

• Peyer's Patches Distribution: Found throughout the GI tract but highly concentrated in the distal ileum. Approximately $46\%$ of Peyer's patches are concentrated in the distal $25\,cm$ of the human ileum.

Digestion and Absorption Processes

Digestion (Hydrolysis)

• Digestion is the chemical disassembling of large polymer molecules into particles small enough to cross cell membranes.

• Proteins: Broken down into amino acids, dipeptides, and tripeptides.

• Carbohydrates: Broken down into monosaccharides (Glucose, Fructose, Galactose).

• Triglycerides: Broken down into free fatty acids and monoglycerides.

• Nucleic Acids (DNA/RNA): Pancreatic enzymes break them into nucleotides; brush border enzymes then break those into free bases, pentose sugars, and phosphate ions.

Absorption Pathways

• Carbohydrates and Proteins: Absorbed via active transport; they enter blood capillaries and are transported to the liver via the hepatic portal vein.

• Triglycerides:

  • Enter cells of the small intestine via diffusion.

  • Reconstituted into triglycerides inside the cell.

  • Combined with phospholipids, cholesterol, and protein to form water-soluble chylomicrons.

  • Chylomicrons enter lymphatic vessels (lacteals) and travel via the thoracic duct to reach the bloodstream.

Anatomical Resource: Acland’s Video Atlas

• Specimen Quality: Uses bodies bequeathed to the University of Louisville. Specimens are either un-embalmed or preserved with a mild technique to maintain the natural color and texture of living tissue.

• Relevant Volumes for this course:

  • Volume 3: The Trunk.

  • Volume 5: The Internal Organs (Includes Introduction to abdominal organs $5.2.1$, Peritoneum $5.2.2$, Stomach $5.2.3$, Greater/Lesser Omentum $5.2.4$, Duodenum $5.2.6$, Biliary system $5.2.20$, Spleen $5.2.21$, and Arteries/Celiac trunk $5.2.23$).