Human Body Systems: Digestive, Respiratory, and Circulatory Systems

Vocabulary flashcards covering the structural hierarchy of the human body and the detailed anatomy, functions, and processes of the digestive, respiratory, and circulatory systems.

Cell

The countless small minimal units that compose the human body, which unite to form tissues.

Tissue

A bodily structure formed when similar cells come together.

Organ

A functional body structure built when different cells and tissues join forces.

Organ System

A functional collective formed when multiple organs team up to work together in the human body.

Digestive System

The organ system comprising the mouth, pharynx, esophagus, stomach, small intestine, large intestine, and rectum that manages swallowing, dissolving, digesting, absorbing, and eliminating undigested food residues.

Mouth

The initial organ of the digestive system where food is mechanically broken down through chewing by the teeth.

Ptyalin

An enzyme secreted by the salivary glands in the mouth that moistens food and initiates digestion.

Pharynx

An organ located in the midsection of the neck between the mouth and esophagus that serves as a shared conduit connecting both the digestive and respiratory systems.

Oesophagus

A lengthy, narrow muscular tube commonly referred to as the food pipe that transports ingested food smoothly from the mouth to the stomach.

Stomach

A J-shaped organ connecting the esophagus and small intestine whose glandular walls produce digestive juices that digest proteins and fats while churning food.

Chyme

A semi-liquid mixture created by the brief churning and mixing of food with digestive juices in the stomach before passing into the small intestine.

Small Intestine

A lengthy tube measuring approximately $3$ to $5\text{ meters}$ in adults that converts nutrients into soluble forms and absorbs the majority of nutrients into the bloodstream.

Duodenum

The uppermost portion of the small intestine.

Jejunum

The middle section of the small intestine whose walls contain tiny hair-like structures designed to improve nutrient absorption.

Ileum

The final section of the small intestine through which half of the nutrients are absorbed before solid residue is passed to the large intestine for eventual excretion.

Respiratory System

The organ network—including the nose, pharynx, larynx, trachea, and lungs—that functions to inhale oxygen from the environment and exhale carbon dioxide from the body.

Nose

The initial respiratory organ that draws in oxygen-rich air, filters dust particles using tiny nostril hairs, and serves as a sensory organ transmitting smell signals to the brain.

Larynx

An organ located between the throat and the trachea, known as the voice box, that guards the respiratory tract, passes warm humidified air, and facilitates speech.

Adam's Apple

The prominent anatomical feature of the larynx that plays a key role in sound modulation.

Trachea

A conduit extending from the throat to the lungs, commonly called the windpipe, lined with cilia and supported by C-shaped cartilage rings.

Cilia

Tiny hair-like structures lining the inside of the trachea that trap dust and foreign particles to ensure only clean air reaches the lungs.

C-shaped Cartilage Rings

Cartilaginous rings encircling the trachea that provide structural support and prevent it from collapsing during inhalation and exhalation.

Bronchi

The two main branches dividing from the trachea into the right and left bronchi that direct air toward the lungs.

Bronchioles

Smaller subdivisions branching off the bronchi that lead directly to the alveoli.

Alveoli

Delicate, tiny air sacs positioned at the apex of the bronchioles where the vital exchange of oxygen and carbon dioxide occurs.

Lungs

Respiratory organs situated inside the thoracic cavity enclosed by ribs, consisting of a right lung with $3$ sections and a slightly smaller left lung with $2$ sections.

Respiration

The vital process of inhaling oxygen, distributing it to cells to produce energy through a chemical reaction with glucose, and expelling the byproduct carbon dioxide.

Acid-Base Balance Regulation

A crucial function of the respiratory system achieved by controlling carbon dioxide levels in the blood.

Circulatory System

The body system comprising the heart, blood, and blood vessels that circulates blood carrying oxygen, water, hormones, salts, and nutrients while removing metabolic waste.