Digestive System and Food Crisis Lecture Notes

These flashcards cover the primary organs and processes of the human digestive system, as well as statistics and causes regarding the food crisis in the Philippines.

Define chemical digestion.

The breakdown of complex molecules such as proteins, starch, and fats into simple soluble molecules by digestive enzymes through hydrolytic reactions.

What are catalysts in the context of digestion?

Substances that speed up the rate of chemical reactions without being changed or used up in the process; digestive enzymes act as these.

What is the difference between the digestive tract and accessory organs?

The digestive tract (alimentary canal) is the muscular passageway food passes through directly (mouth to anus), while accessory organs (salivary glands, liver, gallbladder, pancreas) release substances like enzymes or hormones into the tract to help breakdown food.

What enzyme is found in saliva and what is its specific function?

Salivary amylase; it initiates the breakdown of starch into sugar.

What is a bolus?

A ball of food shaped by the tongue and mixed with saliva for swallowing.

How many milk teeth and permanent teeth do humans typically develop?

Humans develop $20$ milk teeth and $32$ permanent teeth.

Identify the functions of the four types of human teeth.

Incisors: cutting and biting; Canines: tearing; Molars/Premolars: grinding.

What is the function of the epiglottis?

A leaf-shaped cartilage that covers the opening of the larynx during swallowing to prevent food from entering the respiratory tract/trachea.

How long is the esophagus and how does it move food?

It is about $25\,cm$ ($10\,inches$) long and moves food via peristalsis, which consists of rhythmic wavelike contractions of longitudinal and circular muscles.

What are rugae?

Folds in the lining of the stomach that are visible when the stomach is empty.

What are the two sphincters located in the stomach?

The Cardiac sphincter (lower esophageal sphincter) which separates the esophagus from the stomach, and the Pyloric sphincter which lies between the stomach and small intestine.

What are the components and functions of gastric juice?

Strong hydrochloric acid ($HCl$) which softens tissues and kills germs, and Pepsin (activated from pepsinogen) which digests proteins.

What is chyme?

The mixture of gastric juice and food that leaves the stomach to enter the small intestine.

List the three main regions of the small intestine.

Duodenum, Jejunum, and Ileum.

How do villi and microvilli assist in digestion?

They increase the total surface area of the small intestine, facilitating the absorption of nutrients.

Into what simple molecules are carbohydrates, fats, and proteins broken down during digestion?

Carbohydrates are broken down into simple sugars; Fats into fatty acids and glycerol; Proteins into amino acids.

What are the primary functions of the large intestine?

To absorb water and mineral salts from undigested food material and to form/store feces.

What is the function of the ileocecal valve?

It is located between the ileum and the cecum to prevent food from traveling backward into the small intestine.

Define defecation (egestion).

The process where solid waste material (feces) is eliminated from the body through the anus.

What are the three pairs of salivary glands?

Parotid glands, Submandibular (submaxillary) glands, and Sublingual glands.

What is the main digestive function of the liver?

The production of bile, which helps break down large fat particles through emulsification.

What three substances does the pancreas secrete to aid digestion?

Pancreatic juice (digests all food types), Sodium bicarbonate (neutralizes chyme), and Insulin (regulates sugar metabolism).