Levels of Biological Organization and the Human Digestive System

Flashcards covering the hierarchy of biological organization and the detailed structure and processes of the human digestive system, including mechanical and chemical digestion.

Levels of Biological Organization

A hierarchy extending from atoms to the biosphere, categorized into subcellular (nonliving) levels and cellular (living) levels.

Alimentary Canal

A digestive tract approximately $7-9\,m$ long, extending from the mouth to the anus, through which food passes during digestion.

Accessory Organs

Glands that provide enzymes and substances essential for digestion, joined to the alimentary canal by small tubes called ducts.

Ducts

Small tubes used to join accessory organs to the alimentary canal.

Gland

An organ which releases a fluid.

Ingestion

The first step of the digestive process, involving taking food into the body by the mouth.

Digestion

The process of breaking food down into smaller components, categorized as either mechanical or chemical.

Absorption

The process where broken down food particles leave the digestive tract and move to the blood transport system; $80\%$ occurs in the small intestine.

Egestion

The removal of solid waste materials from the body that were not absorbed.

Mechanical Digestion

The physical breakdown of food into smaller parts without chemical change, primarily involving the mouth and stomach churning.

Chemical Digestion

The breakdown of food into particles small enough to be absorbed into the bloodstream using enzymes and digestive juices.

Enzyme

A protein that speeds up the rate of a biological reaction without being used up in the reaction.

Incisors

Human teeth ($8$ in adults) used for the function of biting.

Canines

Human teeth ($4$ in adults) used for the function of tearing.

Premolars

Human teeth ($8$ in adults) used for grinding and chewing.

Molars

Human teeth ($12$ in adults) used for grinding and chewing.

Saliva

A fluid made of $98\%$ water, $1\%$ mucus, and $1\%$ enzymes released by the sublingual, submandibular, and parotid glands.

Amylase

An enzyme in saliva that digests starch ($\text{starch} \rightarrow \text{maltose} + \text{maltose}$).

Maltase

An enzyme in saliva that digests maltose ($\text{maltose} \rightarrow \text{glucose} + \text{glucose}$).

Lingual Lipase

An enzyme produced by Von Ebner serous glands at the back of the tongue that digests lipids.

Bolus

A soft mass of food molded and smoothed by the tongue to facilitate swallowing.

Peristalsis

The involuntary process of muscle contractions that move food down the esophagus and through the digestive tract.

Esophageal Sphincter

A muscle that relaxes during swallowing to allow food to enter the esophagus and contracts when not swallowing.

Epiglottis

A structure that closes over the trachea during swallowing to prevent food from entering the windpipe.

Rugae

Long ridges in the inner muscle layer of the stomach that allow it to expand and increase surface area.

Pyloric Glands

Glands in the stomach that make mucus to line and protect the organ.

Gastric Glands

Glands in the stomach that produce and release gastric juice consisting of hydrochloric acid and enzymes.

Gastrin

A hormone that stimulates the release of hydrochloric acid ($\text{HCl}$) from gastric cells.

Cardiac Sphincter

A circular muscle at the top end of the stomach that prevents acidic gastric juice from entering the esophagus.

Pyloric Sphincter

A circular muscle at the bottom end of the stomach that controls the movement of stomach juice into the small intestine.

Chyme

The semi-liquid state of food as it leaves the stomach.

Gastric Juice

A mixture of mucus, acid, and digestive enzymes with a pH range of $2-3$.

Pepsin

The active form of pepsinogen, converted by hydrochloric acid, which breaks down proteins into smaller peptides.

Gastric Lipase

A stomach enzyme that digests short and medium length fatty acids.