Chapter 1: Nutrition and Digestive System Overview

Nutrition

The science that deals with foods, nutrient composition, eating habits, and the health and disease status of individuals and populations. It includes the social, economic, cultural, and psychological implications of food and eating (RA 10862, 2016).

Health

A state of complete physical, mental, and social well-being, not merely the absence of disease (WHO, 1985).

Nutrients

Chemical substances from food that provide energy, structural materials, and regulatory agents to support growth, maintenance, and repair of the body's tissues (Whitney & Rolfes, 2016).

Foods

Substances derived from plants or animals that provide nutrients and energy necessary for the maintenance of life, growth, and tissue repair (Whitney & Rolfes, 2016).

Essential Nutrients

Nutrients that must be obtained from food because the body cannot synthesize them in sufficient quantities. Approximately 40 nutrients are known to be essential (Whitney & Rolfes, 2016).

Diet

The usual pattern of food and drink intake by a person (FNRI, 2012).

Balanced Diet

Contains all the necessary nutrients and other food substances in the right amounts and proportions to maintain good health (FNRI, 2012).

Nutritional Status

The condition of the body as a result of the intake, absorption, and utilization of food (Whitney & Rolfes, 2005).

Malnutrition

A condition caused by deficient, excessive, or imbalanced intake of energy or nutrients (DeBruyne, Pinna, & Whitney, 2016).

Undernutrition

Insufficient food energy or nutrient intake, leading to increased susceptibility to disease (DeBruyne, Pinna, & Whitney, 2016).

Overnutrition

Excessive consumption of food energy or nutrients, leading to disease (DeBruyne, Pinna, & Whitney, 2016).

Anatomy

The study of the structure of body parts and their relationships to one another (Marieb & Hoehn, 2013).

Physiology

The study of how living organisms function (Widmaier et al., 2019).

Chemical Level

Atoms combine to form molecules, which form organelles—the basic units of cells.

Cellular Level

Cells are the smallest units of life, varying in shape and function.

Tissue Level

Tissues consist of similar cells performing common functions.

Epithelium

Covers surfaces and lines cavities.

Muscle Tissue

Facilitates movement.

Connective Tissue

Supports and protects organs.

Nervous Tissue

Facilitates internal communication via electrical impulses.

Organ Level

An organ is composed of at least two types of tissues that perform specific functions.

Organ System Level

Organs work together to achieve a common function.

Organismal Level

The organism represents the sum total of all levels working together to sustain life.

The Cell

The basic structural and functional unit of life.

Plasma Membrane

A lipid bilayer embedded with proteins that regulate molecule movement and cell communication.

Cytoplasm

Contains organelles suspended in cytosol, a fluid that hosts metabolic activities.

Mitochondria

Generate ATP (energy).

Ribosomes

Synthesize proteins.

Endoplasmic Reticulum (ER)

Involved in protein packaging and lipid synthesis.

Golgi Apparatus

Modifies and packages proteins for secretion.

Peroxisomes

Detoxify harmful substances.

Lysosomes

Digest cellular waste.

Digestive System

Essential for nutrient and water absorption, maintaining body homeostasis, and supporting organ function.

Alimentary Canal (GI Tract)

Continuous tube from mouth to anus, including the esophagus, stomach, small intestine, and large intestine.

Accessory Organs

Teeth, tongue, salivary glands, liver, gallbladder, and pancreas.

Ingestion

The act of eating and swallowing food.

Mastication

Chewing food to increase surface area for enzyme action.

Saliva

Contains enzymes (amylase, lipase) that begin digestion and help taste sensation.

Peristalsis

Rhythmic muscle contractions that move food along the GI tract.

Mouth

Begins mechanical and enzymatic digestion.

Esophagus

Moves food to the stomach.

Stomach

Secretes acids and enzymes to digest proteins; forms chyme.

Small Intestine

Main site of digestion and absorption (duodenum, jejunum, ileum).

Defecation Reflex

Triggered by feces in the rectum, causing urge.

Stomach Action

Strongest muscles churn food into chyme.

Pyloric Sphincter

Regulates chyme passage to the duodenum.

Segmentation

Circular muscle contractions mix chyme in the intestine.

Sphincter Contractions

Open and close to control digestive flow.

Digestive Enzymes

Break down food at various digestion stages.

Hormones in Digestion

Regulate digestive processes for efficiency.

Nutrient Absorption

Occurs mainly in the small intestine.

Simple Diffusion

Water and small lipids cross membranes freely.

Facilitated Diffusion

Requires carrier proteins for nutrient transport.

Active Transport

Nutrients move against gradient using ATP.

Endocytosis

Cells engulf large molecules via vesicles.

Blood Route

Nutrients processed by liver before body distribution.

Lymphatic Route

Large fats enter lymph before blood circulation.

Excretion

Removal of waste from metabolism and digestion.

Types of Wastes

Includes undigested materials, toxins, and by-products.

Organs of Excretion

Lungs, skin, kidneys, and intestines eliminate waste.

Nephron Structure

Functional unit of kidneys for filtration and reabsorption.

Urine Composition

96% water, urea, uric acid, and salts.

Factors Affecting Kidney Function

Hormones, diet, and diuretics influence urine output.

Feces Formation

Water reabsorption in large intestine forms feces.

Composition of Feces

Includes indigestible residues, mucus, bacteria, and water.

Factors Affecting Intestinal Excretion

Water intake, fiber, and stress influence bowel movements.

Digestive Process Summary

Digest, absorb, and excrete through coordinated systems.