The-Human-Digestive-System

Overview of the Digestive System

  • The Digestive System processes food, preparing it for cellular use across the body.

Digestion Process

  • Definition: Digestion refers to the chemical breakdown of complex biological molecules into simpler components.

    • Lipids break down into fatty acids

    • Proteins break down into amino acids

    • Carbohydrates break down into simple sugars - Lipids turn into fatty acids, which are like tiny energy pieces for our bodies. - Proteins break into amino acids, the little building blocks that help us grow. - Carbohydrates change into simple sugars, giving us quick energy to play and run around.

Functions of the Digestive System

  • Produces digestive chemicals to break down food.

  • Filters out harmful substances.

  • Eliminates solid waste from the body.

Types of Digestion

Mechanical Digestion

  • Involves the physical alteration of food to prepare it for chemical digestion:

    • Activities include chewing, tearing, grinding, mashing, and mixing food.

Chemical Digestion

  • Involves chemical changes facilitated by digestive enzymes that break down food into absorbable molecules:

    • Carbohydrates (into sugars)

    • Proteins (into amino acids)

    • Lipids (into fatty acids)

    • Digestive enzymes are specialized proteins essential for this breakdown.

Phases of Digestion

  1. Ingestion: Taking in food.

  2. Movement: Transportation of food through the digestive tract.

  3. Digestion: Breakdown of food.

  4. Absorption: Nutrients are absorbed into the body.

The Digestive Tract

  • Described as a long muscular tube that spans from the mouth to the anus.

  • Key Parts:

    • Mouth

    • Pharynx

    • Esophagus

    • Stomach

    • Small Intestine

    • Large Intestine

Accessory Digestive Organs

  • Include organs that assist in digestion but are not part of the digestive tract:

    • Teeth

    • Tongue

    • Salivary glands

    • Liver

    • Gall bladder

    • Pancreas

Functions of the Mouth

  • Functions: The mouth serves multiple roles in digestion:

    • Entry point for food.

    • Facilitates tasting and mechanical breakdown.

    • Salivary glands secrete saliva (containing amylase) for initial starch digestion.

Anatomy of the Mouth

  • Teeth: Function to cut, tear, crush, and grind food.

  • Salivary Glands: Exhibit three types:

    • Parotid: beneath the cheeks

    • Submaxillary: below the jaw

    • Sublingual: below the tongue

  • Tongue: Mixes food, forming a bolus that is pushed down the throat.

Swallowing Mechanism

  • A coordinated effort involving the tongue, soft palate, pharynx, and esophagus:

    • Phases of swallowing:

      • Tongue pushes food into the pharynx (voluntary phase)

      • Tongue blocks the mouth

      • Soft palate closes off the nasal passage

      • Larynx rises; epiglottis closes trachea opening.

The Esophagus

  • A straight muscular tube connecting the mouth to the stomach:

    • Length: approximately 10 inches (25cm).

    • Food takes about 4-8 seconds to reach the stomach.

    • Peristalsis: Smooth muscle contractions propelling food downwards.

    • Cardiac Sphincter: Allows food entry into the stomach.

Anatomy and Function of the Stomach

  • Description: J-shaped muscular sac with rugae (inner folds for increasing surface area).

    • Role:

      • Mixes food with gastric juices (hydrochloric acid and enzymes).

      • HCL aids in food breakdown and bactericidal action.

    • Key Enzyme: Pepsin converts proteins into peptides.

    • Mucus protects stomach lining and aids in lubrication.

    • Transforms bolus into chyme after approximately 4 hours. The stomach is a J-shaped pouch that helps digest food. It mixes food with juices and acids to break it down, and a special helper called pepsin changes proteins into smaller pieces. Mucus protects the stomach walls, and after about 4 hours, the food turns into a chunky mixture called chyme, ready to move to the next part of digestion.

The Small Intestine

  • A long (20 ft) tube below the stomach, comprising three parts:

    The small intestine is made up of three parts: the duodenum, jejunum, and ileum. The main purpose of the small intestine is to digest food and absorb nutrients.

    • Duodenum (10 in): This is where digestive juices from the pancreas and liver mix with food to help break it down.

    • Jejunum (8 ft): This part absorbs nutrients into the blood from the digested food.

    • Ileum (12 ft): This is the last part where remaining nutrients are absorbed before the food moves on to the large intestine.

  • Main site for digestion and nutrient absorption:

    • Takes 4-8 hours for food processing.

    • Mucosa secretes enzymes and absorbs nutrients into the blood.

Villi and Microvilli

  • Villi: Fingerlike projections that increase the surface area for absorption.

  • Microvilli: Tiny projections on villi enhancing absorption capacity.

The Large Intestine (Colon)

  • Description: Larger diameter but shorter (about 5 ft).

    • Role in water absorption from digested food, solidifying waste within 10-12 hours.

  • Waste is stored in the rectum before excretion as feces.

Accessory Organs’ Functions

Liver

  • Functions as the body's largest gland:

    • Stores vitamins A, D, E, K, and sugar/glycogen.

    • Produces and secretes bile via ducts to gall bladder.

Gall Bladder

  • Stores bile until needed for digestion:

    • Bile is essential for emulsifying fats to aid in digestion, but is not an enzyme.

Pancreas

  • Produces digestive juice containing key enzymes for carbohydrates, fats, and proteins digesting:

    • Juices secreted into the duodenum.

Path of Digestion

  1. Mouth

  2. Pharynx

  3. Esophagus

  4. Stomach

  5. Small Intestine

  6. Large Intestine

  7. Anus

The Excretory System

  • Aims to eliminate wastes and unnecessary substances from the body.

Types of Wastes

  • Solid Waste: Removed via the digestive system as feces.

  • Metabolic Waste: Byproducts from metabolic processes:

    • Examples: Water, carbon dioxide, salts, urea.

Waste Removal Processes

  • Egestion: Elimination of digestive waste.

  • Excretion: Removal of metabolic waste.

Organs of Excretion

Skin

  • Facilitates diffusion of water, salts, and urea via sweat glands.

Lungs

  • Excrete waste from respiration primarily through carbon dioxide and water vapor.

Liver (again)

  • Integral to the digestive and excretory systems, processing amino acids to form urea for urine.

Kidneys

  • Major organs for excretion, filtering blood to produce urine containing wastes.

Urinary System

  • Comprised of organs facilitating urine excretion:

    • Ureter: Transports urine to the bladder.

    • Urinary Bladder: Stores urine.

    • Urethra: Excretes urine from the body.

Assignment

  • Research and create a table on different digestive enzymes, following the provided format including:

    • Enzymes

    • Substrates

    • Products

    • Digestive Gland (or origin of the enzyme).