Nutrition: The Human Digestive System

Flashcards for reviewing the human digestive system, covering nutrition, digestion, absorption, and the alimentary canal.

What is nutrition?

The process by which living organisms take in substances from their environment to build/repair cells or provide energy.

Why is nutrition important for organisms?

For growth, development, repair, reproduction, and obtaining energy to carry out processes.

Define digestion.

The breakdown of large nutrient molecules into smaller ones for absorption into the bloodstream.

What is the alimentary canal?

A long tube through which food passes, from ingestion to egestion.

Define absorption in the context of digestion.

The uptake of nutrients from the alimentary canal into the bloodstream.

What is ingestion?

Taking food into the mouth.

Define egestion.

The removal of undigested food in the form of feces through the anus.

What is excretion?

The removal of metabolic wastes from an organism.

What are enzymes?

Proteins that catalyze metabolic reactions.

Why is digestion important?

It makes nutrients easier to absorb into the bloodstream.

Give examples of food components that do not need to be digested.

Simple sugars, water, vitamins, and minerals.

What is mechanical digestion?

The breakup of large pieces of food into smaller ones, increasing their surface area (e.g., chewing).

What is chemical digestion?

The breakdown of large food molecules into smaller ones by the action of enzymes.

What is peristalsis?

The contraction and relaxation of muscles in the walls of the alimentary canal to move food along.

What is the role of sphincter muscles in the alimentary canal?

To completely close the tube in certain places to keep the food in one part of the alimentary canal.

What is the function of mucus within the alimentary canal?

To lubricate the alimentary canal, aiding the movement of food.

What is the role of saliva in the mouth?

To dissolve substances, bind chewed food together forming a bolus, lubricate it, and begin the digestion of starch via amylase.

What is the epiglottis?

A piece of cartilage that covers the entrance of the trachea to prevent food from entering the lungs when swallowing.

What is chyme?

The mixture of food, enzymes, and mucus produced in the stomach.

What do goblet cells in the stomach secrete?

Mucus.

What is the function of hydrochloric acid in the stomach?

To kill any bacteria in the food.

What is the function of pepsin?

A protease that begins the digestion of proteins into polypeptides. It works best in acidic conditions.

What is the function of rennin?

An enzyme produced ONLY in the stomach of young mammals, it causes the milk they get from their mothers to clot so the milk proteins can be broken down by pepsin.

Name the three parts of the small intestine.

Duodenum, jejunum, and ileum.

Where are the enzymes secreted into the duodenum made?

Pancreas.

Name three enzymes found in pancreatic juice and their function.

Amylase (breaks down starch to maltose), Trypsin (breaks down proteins to polypeptides), and Lipase (breaks down lipids to fatty acids and glycerol).

What is the function of sodium hydrogencarbonate in the pancreatic juice?

To create a suitable environment for the enzymes amylase, trypsin, and lipase to work by partially neutralizing the chyme.

Where is bile produced and stored?

Produced in the liver and stored in the gall bladder.

What is emulsification?

Breaking up large drops of fat into small ones. This makes it easier for lipase to digest them.

Name the carbohydrases and their functions found in the small intestine.

Maltase (breaks down maltose to glucose), Sucrase (breaks down sucrose to glucose and fructose), Lactase (breaks down lactose to glucose and galactose).

What enzyme completes the breakdown of fats to fatty acids and glycerol in the small intestine?

Lipase.

What are villi?

Millions of tiny projections that covers the inner walls of the small intestine.

How is the small intestine adapted for absorption?

Long length, villi and microvilli (increases surface area), blood capillaries (absorb monosaccharides, amino acids, water, minerals, and vitamins), lacteals (absorb lipids), and thin walls (one cell thick).

What is the function of the large intestine?

Absorption of water and salts and the temporary storage of undigested food as faeces.

What is the role of the rectum?

Temporarily stores undigested food.

What are the three functions of liver?

Process some of the nutrients before they go any further, some are broken down, some are converted into other substances and some stored.

Where are the nutrients take to after absorption into the blood?

To the liver via the hepatic portal vein.