Gastrointestinal System 2 - Anatomy, Physiology, and Nutrition

Vocabulary practice flashcards covering accessory digestive organs (liver, gallbladder, pancreas), chemical and mechanical digestion, lipid transport and metabolism, intestinal absorption, and eating regulation from Human Anatomy and Physiology 2.

Falciform ligament

A peritoneal fold that separates the right and left lobes of the liver and suspends the liver from the diaphragm.

Glycogenesis

The metabolic process of converting glucose into glycogen for storage in the liver and skeletal muscles.

Glycogenolysis

The metabolic breakdown of stored glycogen into glucose to be used as fuel.

Gluconeogenesis

The synthesis of glucose from non-carbohydrate precursors, such as amino acids and glycerol, to maintain blood glucose levels.

Kupffer cells

Stellate macrophages located within the sinusoidal walls of the liver that remove debris and perform phagocytosis.

Liver lobules

Hexagonal structural and functional units of the liver consisting of plates of hepatocytes surrounding a central vein.

Hepatocytes

Liver cells arranged in plates that filter and process nutrient-rich blood, synthesize plasma proteins, and produce bile.

Portal triad

A structure located at each corner of a liver lobule containing a branch of the hepatic artery (oxygen-rich blood), a branch of the hepatic portal vein (nutrient-rich blood), and a bile duct.

Liver sinusoids

Fenestrated capillaries where oxygen-rich blood from the hepatic artery and nutrient-rich blood from the hepatic portal vein mix before draining into the central vein.

Gallbladder

A pear-shaped muscular sac located underneath the right lobe of the liver that stores and concentrates bile.

Bile

A yellow-green alkaline fluid ($\text{pH } 7.6\text{--}8.6$; $800\text{--}1{,}000\text{ mL/day}$) produced by the liver containing water, ions, bile acids, cholesterol, lecithin, and conjugated bilirubin, functioning as a detergent-like fat emulsifier.

Enterohepatic circulation

The physiological recycling process in which $80\%$ of bile acids are reabsorbed in the terminal ileum, returned to the liver via the hepatic portal vein, and re-secreted into the bile.

Stercobilin

A brown pigment produced in the large intestine by bacterial breakdown of bilirubin that gives faeces its characteristic colour.

Hepatopancreatic ampulla

The dilated chamber formed by the union of the common bile duct and the main pancreatic duct that empties digestive secretions into the duodenum at the major duodenal papilla.

Pancreatic juice

An alkaline secretion ($1.2\text{--}1.5\text{ L/day}$) produced by pancreatic acinar and duct cells containing bicarbonate ($\text{HCO}_3^-$) and digestive enzymes that neutralises acidic gastric chyme.

Pancreatic islets

Endocrine clusters within the pancreas that synthesize and secrete glucagon and insulin directly into the bloodstream to control blood glucose levels.

Cholecystokinin (CCK)

A hormone secreted by duodenal enteroendocrine cells that stimulates the release of enzyme-rich pancreatic juice, induces gallbladder contraction, and relaxes the hepatopancreatic sphincter.

Secretin

A hormone released by duodenal enteroendocrine cells in response to acidic chyme that stimulates bicarbonate-rich ($\text{HCO}_3^-$) pancreatic secretion and accelerates liver bile production.

Hydrolysis

A chemical enzymatic reaction in which a water molecule is added to break covalent bonds in complex food molecules.

Micelles

Spherical clusters of fatty acids, monoglycerides, lecithin, and bile salts that transport water-insoluble lipids across the aqueous lumen to the intestinal mucosa for absorption.

Chylomicrons

Water-soluble lipoprotein complexes assembled in enterocytes by packaging resynthesized triglycerides ($90\%$) and cholesterol with a protein coat ($2\%$) before exocytosis into lymphatic lacteals.

Very low-density lipoproteins (VLDL)

Lipoproteins produced by the liver containing $55\%$ triglycerides and $20\%$ cholesterol that transport triglycerides to peripheral tissues.

Low-density lipoproteins (LDL)

Cholesterol-rich lipoprotein particles ($53\%$ cholesterol) derived from VLDL breakdown that carry cholesterol to body cells; commonly referred to as "bad lipoproteins".

High-density lipoproteins (HDL)

Protein-rich lipoprotein particles ($50\%$ protein) that harvest excess cholesterol from peripheral tissues and transport it back to the liver for excretion; commonly referred to as "good lipoproteins".

Absorptive state

The metabolic period lasting approximately $4\text{ hours}$ following a meal, during which ingested nutrients enter the blood, insulin predominates, and excess glucose and amino acids are stored as glycogen, fat, and proteins.

Post-absorptive state

The metabolic period when gastrointestinal absorption is complete, during which glucagon, adrenaline, and cortisol maintain blood glucose via hepatic glycogenolysis and gluconeogenesis while peripheral tissues oxidize fatty acids.

Teniae coli

Three ribbons of longitudinal smooth muscle that run along the external surface of the large intestine, causing its wall to pucker.

Haustra

Pocket-like sacs or pouches in the colon wall formed by tonic contractions of the teniae coli.

Epiploic appendages

Small, fat-filled sacs of visceral peritoneum that hang from the outer wall of the large intestine along the teniae coli.

Internal anal sphincter

An involuntary ring of smooth muscle in the anal canal that relaxes in response to parasympathetic sacral cord signaling during the defaecation reflex.

External anal sphincter

A voluntary ring of skeletal muscle surrounding the anal canal that can be consciously contracted to postpone defaecation.

Leptin

An "energy expenditure hormone" secreted by adipose tissue in proportion to body fat mass that acts on the hypothalamus to suppress appetite stimulants and upregulate appetite suppressants.

Hunger

The physiological drive to consume food, triggered by decreased circulating nutrient levels and regulated by the hypothalamus.

Appetite

The psychological desire to eat that is independent of metabolic nutritional need, influenced by habits, emotional state, and sensory cues.