Digestive System Overview

The Digestive System

• Digestion starts in the mouth with chewing and salivary amylase action.
• The esophagus is a long tube facilitating food movement to the stomach via peristalsis.
• The lower esophageal sphincter prevents food from re-entering the esophagus.
• The stomach is a sac-like organ that mixes food and secretes acids and enzymes to aid breakdown.
• Chyme is the partially digested food leaving the stomach in a liquid or paste form.
• The small intestine, over 20 feet long, is where nutrient absorption occurs, assisted by bile and enzymes.
• The small intestine consists of three parts: duodenum, jejunum, and ileum.
• The duodenum continues food breakdown, while the jejunum and ileum absorb nutrients into the bloodstream.

Important Organs in Digestion

• Pancreas: Secretes enzymes into the small intestine to break down proteins, fats, and carbohydrates.
• Liver: Produces bile for fat digestion and purifies blood from the small intestine.
• Gallbladder: Stores bile produced by the liver and releases it into the small intestine during meals.

Digestive Enzymes

• Amylase: Breaks down carbohydrates.
• Lipase: Breaks down fats.
• Proteases: Breaks down proteins.

Large Intestine

• A 5-6 foot tube connecting the caecum to the rectum.
• Converts liquid waste to solid stool through peristaltic movement.
• Comprises five parts: caecum, ascending colon, transverse colon, descending colon, and sigmoid colon.

Rectum and Anus

• The rectum stores solid waste before excretion through the anus.
• The anus has specialized upper lining and pelvic floor muscles to control stool elimination.
• The anal sphincter regulates the elimination process.

Cells and Their Composition

• Cells are the basic structural and functional units of life, essential for nutrient intake and energy conversion.
• Cell Membrane: Semi-permeable layer enabling substance entry and hormone reception.
• Cytoplasm: Watery solution containing minerals and organic molecules.
• Organelles: Include endoplasmic reticulum (transport), ribosomes (protein synthesis), Golgi apparatus (carbohydrate synthesis), mitochondria (energy production), lysosomes (digestion), and centrioles (cell division).

Amino Acids

• Essential amino acids must be obtained from the diet; examples include leucine and lysine.
• Non-essential amino acids are synthesized by the body; examples include glutamic acid and glycine.
• Functions of amino acids include building and protecting tissues, repairing damage, and oxygen transport.

Functions of Protein

• Repairs worn-out tissues and builds new ones.
• Serves as a source of energy and contributes to body fluids.
• Maintains fluid and pH balance and signals cellular functions.
• Acts as structural components and transports substances throughout the body.

Protein Sources

• Include meat, poultry, fish, dairy products, grains, legumes, and vegetables.

Protein-Energy Malnutrition (PEM)

• A condition due to insufficient protein or energy intake, with two forms: marasmus and kwashiorkor.

Fats and Lipids

• Fats contain 9 calories per gram and should comprise 15-25% of daily intake.
• Lipids are insoluble in water and include fats, oils, and waxes.

Types of Fatty Acids

• Saturated Fats: Raise cholesterol levels; sources include butter and meat.
• Monounsaturated Fats: Lower "bad" cholesterol; sources include vegetable oils.
• Polyunsaturated Fats: Include omega-3 (beneficial for heart health) and omega-6 (lowers cholesterol).

Functions of Fats

• Protects vital organs, facilitates vitamin absorption, contributes to dietary flavor, and insulates the body.

Cholesterol

• An essential component of cell membranes and needed for hormone synthesis, not to exceed 300mg/day to avoid heart disease.

Dietary Sources of Cholesterol

• Richest: Egg yolk, fish roes; moderate: meat fats, dairy; poor: lean meats and skimmed milk; cholesterol-free: vegetables and fruits.

Lipoproteins

• Low-Density Lipoprotein (LDL): Known as "bad cholesterol," contributes to arterial blockage.
• High-Density Lipoprotein (HDL): Known as "good cholesterol," helps remove excess cholesterol from arteries.

Vitamins

• Essential for growth and health; classified into fat-soluble (A, D, E, K) and water-soluble (B, C).
• Vitamin deficiencies can lead to various health issues.

Fat-Soluble Vitamins

• Absorbed with fat, stored in the body, and deficiencies develop slowly; examples include Vitamin A (retinol) important for vision and tissue health.

Importance of Daily Intake

• Daily recommended doses for Vitamin A: Male - 1,000 micrograms; Female - 800 micrograms.
• Deficiencies in vitamins can lead to health problems like night blindness and reduced immunity.

Test your knowledge on the digestive system, focusing on the mouth and esophagus. This quiz will cover the beginning of the digestive process, including how food is broken down and the role of peristalsis. Stay informed about the key functions and components of digestion.