Digestion and Metabolism 1

Flashcards covering the major organs, histology, processes, and accessory organs of the digestive system, including specific enzymes, secretions, and adaptations for digestion and absorption.

What are the four fundamental tissue layers of the alimentary canal?

Mucosa, Submucosa, Muscularis, and Serosa.

What are the six fundamental activities of the digestive system?

Ingestion, Propulsion, Mechanical Digestion, Chemical Digestion, Absorption, and Defecation.

What is ingestion?

The entry of food into the alimentary canal.

What is propulsion?

The movement of food/chyme via alternating waves of contraction and relaxation, including peristalsis, gastric emptying, and mass movement.

What is mechanical digestion?

The physical breakdown of food through processes like chewing (mastication), gastric mixing, and segmentation (back and forth movement).

What is chemical digestion?

The breakdown of food by enzymes, primarily in the small intestines.

What is absorption?

The movement of digested nutrients from the alimentary canal into the blood.

What is defecation?

The elimination of feces from the body.

What digestive processes occur in the mouth?

Ingestion, propulsion (swallowing), mechanical digestion (mastication), and chemical digestion.

What accessory organs are found within the mouth?

Salivary glands.

What are the functions of salivary amylase?

Produced by salivary glands, it breaks down starch/glycogen. It works in the mouth, pharynx, and esophagus, and is inactivated in the stomach.

What is the function of lingual lipase?

Produced by the tongue, it breaks down lipids. It is inactive in the mouth and esophagus but becomes active in the stomach.

What is the function of the Upper Esophageal Sphincter (UES)?

It controls the movement of food into the esophagus and controls the passage of both food and air.

What is the function of the Lower Esophageal Sphincter (LES)?

It prevents gastric juices from entering the esophagus.

Describe the muscle composition of the esophagus.

The upper 1/3 is skeletal muscle (voluntary), the middle 1/3 contains both skeletal and smooth muscle, and the lower 1/3 is smooth muscle only (involuntary).

What digestive processes occur in the stomach?

Propulsion, mechanical digestion, and chemical digestion.

What are the three major anatomical regions of the stomach?

The Fundus (top part), the Body (most of the stomach), and the Pylorus (final segment).

What is the function of rugae in the stomach?

Folds that allow the stomach to expand.

What is the function of the pyloric sphincter?

It controls the passage of food from the stomach into the small intestine.

What do parietal cells secrete and what are their functions?

Parietal cells secrete HCl (to kill microorganisms) and intrinsic factor (to absorb vitamin B12).

What do chief cells secrete?

Chief cells secrete pepsinogen, the inactive form of pepsin, which digests protein.

What digestive processes occur in the small intestines?

Propulsion, mechanical digestion, chemical digestion, and absorption (of most nutrients).

What are the three regions of the small intestine?

The Duodenum, Jejunum, and Ileum.

What three main adaptations of the small intestine wall increase its absorptive capacity?

Circular folds, villi, and microvilli.

What is the main function of the large intestines?

To finish nutrient absorption, absorb H2O, and form and eliminate feces.

What digestive processes occur in the large intestines?

Propulsion, mechanical digestion, absorption, and defecation.

What is the Internal anal sphincter composed of and is its action voluntary or involuntary?

It is composed of smooth muscle and its action is involuntary.

What is the External anal sphincter composed of and is its action voluntary or involuntary?

It is composed of skeletal muscle and its action is voluntary.

List some functions and secretions of the liver.

The liver synthesizes bile, removes old RBCs, processes nutrients (glucose to glycogen after meals, glycogen to glucose between meals), secretes hormones and plasma proteins, and eliminates waste.

What are bile salts synthesized from?

Cholesterol.

What type of molecule are bile salts?

Amphipathic molecules.

What is the function of bile salts in digestion?

They emulsify fat, turning large fat globules into tiny fat droplets surrounded by H2O to increase surface area for lipid digestion (bile does NOT digest lipids, it only aids in digestion).

What are the key components of pancreatic juice?

Zymogens (inactive proteases), bicarbonate buffer juice, co-lipase, and enzymes (pancreatic lipase, amylase).

What is the function of bicarbonate buffer juice in pancreatic juice?

It helps buffer stomach HCl acid.

What are zymogens?

Inactive storage forms of proteases produced by exocrine acinar cells of the pancreas.

Name some pancreatic zymogens.

Trypsinogen, chymotrypsinogen, and procarboxypeptidase.

Trace the pathway of pancreatic zymogens from acinar cells to the small intestine.

Acinar cells → Pancreatic duct → Ampulla of Vater → Sphincter of Oddi → Duodenum (small intestine).

Describe the process of zymogen synthesis and packaging within a pancreatic acinar cell.

DNA transcribes mRNA, mRNA is translated by ribosomes on the RER, RER performs peptide modification, peptides travel to the Golgi apparatus, and then are packaged into vesicles.