Physiology Lecture 4 - Digestion and Absorption

These flashcards cover key concepts from the lecture on digestion and absorption, focusing on physiological processes and mechanisms involved.

What is digestion defined as in the context of physiology?

The breaking down of complex molecules into simple molecules.

What is the primary function of absorption in the digestive system?

Transporting simple molecules across the intestinal epithelium.

What structures increase the surface area of the small intestine?

Plicae circulares, crypts, villi, and microvilli.

What is the glycocalyx and its significance in the intestinal absorption process?

A jelly-like layer of glycoproteins on enterocytes that helps with nutrient absorption.

What role do goblet cells play in the small intestine?

They contribute a mucous coating to the glycocalyx.

What are tight junctions in enterocytes and describe their permeability?

They form a band near the apical membrane, are permeable to water and electrolytes, but impermeable to organic molecules.

What initiates physical digestion in the human body?

Mastication (chewing).

What is hydrolysis in the context of chemical digestion?

The splitting of chemical bonds by the insertion of water.

What enzyme secreted by the pancreas is responsible for breaking down starch?

α-amylase.

Differentiate between the three types of carbohydrates digested in the human body.

Fibers (indigestible), sugars (simple and complex), and starch (glucose polymers).

What happens to starch during the luminal phase of carbohydrate digestion?

Starches are digested to long oligosaccharides such as dextrins.

What are the major proteolytic enzymes involved in protein digestion?

Pepsinogen and trypsinogen.

What is the function of co-lipase during lipid digestion?

Clears a path through bile products, allowing lipase to hydrolyse triglycerides.

What are micelles and their role in lipid absorption?

Small, water-soluble aggregates formed from fatty acids and monoglycerides that facilitate their absorption in the intestine.

Explain the difference between active and secondary active transport in enterocytes.

Active transport requires ATP to move ions against their gradient, while secondary active transport uses the electrochemical gradient established by active transport to move other molecules.

What mechanism is used by enterocytes to absorb glucose and galactose?

Sodium co-transport.

Describe how fats are absorbed in enterocytes.

Fatty acids and monoglycerides diffuse into enterocytes due to their lipid solubility and are then packaged into chylomicrons.

How is bicarbonate absorbed in the intestinal lumen?

Through the action of carbonic anhydrase and sodium exchange mechanisms in enterocytes.

What is the primary mechanism for sodium absorption in the intestines?

Via sodium co-transport proteins, sodium/hydrogen exchangers, and simple diffusion through ion channels.

Identify the physiological consequences of impaired potassium absorption during diarrhea.

Impairment can disrupt the potassium concentration gradient, affecting homeostasis.

What is the function of crypt cells in water secretion?

They increase intracellular sodium and chloride, causing water to follow into the lumen osmotically.

What is the significance of chylomicrons in lipid absorption?

They transport absorbed dietary fats through the lymphatic system before entering the bloodstream.

What occurs during diarrhea with respect to secretion and absorption?

A mismatch occurs, leading to excessive secretion or decreased absorption, resulting in increased osmotic pressure.