NUSC 1165 Exam 2

Organization of life

Food and fluid that is eaten must be broken down into smaller components and absorbed to be useful.

Atoms

Cannot be broken down

Molecules

Formed from atoms held together by chemical bonds.

Cell

Formed from molecules

Tissue

Groups of similar cells form tissues.

Organ

Perform specialized functions

Organ System

Group of organs that work together.

Organism

Functioning organ systems

The Digestive System

• Ingestion and digestion of food.

• Facilitates the movement of nutrients into the body.

• Responsible for eliminating unabsorbed water.

The Nervous System

• Send nerve signals to help control the passage of food throughout the digestive tract.

The Endocrine System

• Produces hormones to regulate food intake and the function of digestive organs.

The Cardiovascular System

• After absorption, cardiovascular system transports nutrients to individual cells.

The Urinary System

• Responsible for the elimination of fluids.

The Respiratory System

• Responsible for removing carbon dioxide (CO2) from the body.

Integumentary System (Skin)

• Removes water and minerals through the skin.

Ingestion

Taking in food into the body.

Digestion

• Breaking food into components small enough so it can be absorbed into the body.

Energy-yielding nutrients

• Carbohydrate

• Protein

• Fats

Strach

Glucose

Protein

Amino acids

Triglycerides

Fatty acids + Glyceral

Absorption

• The process of taking substances directly into the body.

Gastrointestinal Tract

• Site of digestion and absorption

• Direct contact with nutrients

Accessory Organs

• Produce substances that assist in digestion.

Transit Time

• Time it takes for food to pass through the digestive tract.

• Healthy Adult: 24-72 hours

Small intestine

• Main site for digestion and absorption

Large Intestine

• Processes nutrient waste.

Excretion

• Elimination of products from the body

Digestive Secretions

• Mucus

• Enzymes

Mucus

• Viscous fluid secreted by the glands of the GI tract

• Responsible for lubricating and protecting the digestive tract from harsh environments.

Enzymes

• Protein molecules that speed up the rate of chemical reactions without undergoing any change.

• Assist with breaking down carbohydrate, protein, an fats into smaller components.

Examples of Enzymes

Starch Digestion to Glucose

Strach - (Amylase) - Individual Glucose Molecules

Protein Digestion to Amino Acids

Protein Strand - (Pepsin, Trypsin, Chymotrypsin) - Individual Amino Acids

Triglyceride Digestion to Fatty Acids and Glycerol

Triglyceride - (Lipase) - Fatty Acids + Glycerol

Regulation of the Digestive Tract (Nerve Signals)

• Stimulated by the thought, sight, smell, and presence of food.

• Causes muscle contractions that churn, mix, and propel food through the gut.

• Stimulate or inhibit gastric secretions.

• Coordinate digestive activity with other functions

Regulation of the Gastrointestinal Tract

• Chemical messengers produced in an organ that is released into the blood and generates a response at other locations within the body.

• Helps to prepare different areas of the gut for the arrival of food.

• Regulates nutrient digestion and the rate of food moving through the system.

• Example: Gastrin is activated when food enters the digestive tract.

The Head

• Site of Cephalic Response

• Involves signals from the nervous system

• The sights, sounds, and smells of food prepare the digestive system to process the food components.

The Mouth

• Entry point of food in the digestive tract.

• Mechanical processing of food

• Chemical processing of food

Mechanical Processing of Food

• Chewing food helps to form a bolus

Chemical Processing of Food

• Saliva is produced in the salivary glands.

• Moistens of food, cleanses mouth, protects teeth, and lubricates the upper digestive tract.

• Two enzymes are present in saliva.

Enzymes Present in Saliva

• Lysozyme

• Salivary amylase

Lysozyme

• Blacks bacterial growth that contributes to tooth decay.

Salivary amylase

• Starts starch breakdown in the mouth.

Pharynx

• Funnel-shaped opening

• Responsible for swallowing the food contents.

• Epiglottis

• Only digestive system organ shared by both the digestive and respiratory systems.

Heimlich Maneuver

• Food stuck in the air passages leading to the lungs.

• Chocking potential

• An individual applies pressure below the diaphragm to dislodge the food.

Epiglottis

• Blocks air passages to the lungs as the food moves down the digestive tract.

Esophagus

• Connects the pharynx to the stomach

• Peristalsis

• Sphincter

Peristalsis

• Muscular contractions that moves the food down the esophagus.

Sphincter

• Regulates the passage of food to the stomach.

Stomach

• Temporary storage site for food.

• Production of hydrochloric acid.

• Produces Chyme

Chyme

• Comprised of bolus and hydrochloric acid.

• Remains in the stomach for 2-6 hours.

The Stomach Secretions

• Hydrochloric Acid

• Pepsinogen Production

• Pepsin

Hydrochloric Acid

• Acidifies food contents

• Destroys harmful bacteria

Pepsinogen Production

• Precursor to the enzyme pepsin.

Pepsin

• Activated by hydrochloric acid

• Inactivates salivary amylase

Activation of Pepsin

Pepsinogen → Hydrochloric Acid (HCI) → Pepsin → Protein → Shorter Polypeptides

Regulation of Motility and Secretion

• Thought, smell, sight, taste of food stimulates nerve signals in the brain, increases stomach motility.

• Food enters the stomach and further nerve stimulation occurs.

• Distention occurs in the small intestine, hormones and nerve signals stimulated that decrease gastric secretion and movement.

Small Intestine: Villi

• Fingerlike projections

• Participate in digestion and absorption of nutrients

Small Intestine: Microvilli

• Covers the villi

• Increases the surface area of the small intestine

• Contains digestive enzymes

Small Intestine: Capillaries

• Vessel located in the villi

• Transports amino acids, sugars, and water-soluble nutrients

Small Intestine: Lacteals

• Small lymphatic vessels in the small intestine

• Vessels that handle the transport of lipid digestion products

Muscular Contractions in the Small Intestine

• Peristalsis

• Segmentation

Peristalsis

• Vertical muscular contraction

• Move food along the small intestine

Segmentation

• Horizontal muscular contractions within the small intestine.

Enzymes and Secretions in the Small intestines

• Small intestine Cells

• Pancreas

• Liver

• Gallbladder

Small intestine Cells

• Produces intestinal juices to aid in absorption

Pancreas

• Produces bicarbonate ions to neutralize acids

Liver

Produces bile, a detergent that digests fat

Gallbladder

• Stores bile

Carbohydrate breakdown in the small intestine

Step 1: Action of Pancreatic Amylase

• Breaks apart starch into smaller carbohydrates (double sugars and short glucose chains)

Step 2:

• Enzyme action to break apart double sugars and short glucose chains

Step 3:

• End products of carbohydrate digestion are simple sugars

• They travel through the blood vessel to enter the body

Protein Breakdown in the Small Intestine

Step 1: Action of Trypsin and Chymotrypsin

• Trypsin and Chymotrypsin breakdown polypeptides to amino acids and short amino acid chains

Step 2:

• Trypsin and Chymotrypsin continue to break down the short amino acid and chains into individual amino acids

Step 3:

• Amino acids are the end products of protein digestion

• Amino acids are transported to the body through the blood vessel

Lipid Digestion in the Small Intestine

Step 1:

• Fate digestion products are incorporated into a large lipid droplet call a micelle

Step 2:

• Triglycerides in the lipid droplets are broken down by lipase enzymes

Step 3: Absorption of fats

• Short chain fats are absorbed through the blood vessel

• Long chain fats are packaged into a lipid transport particle and enter the lymph vessel to enter the body.

Water-soluble nutrients

• Absorbed through the blood vessel

• Sugar, amino acids, vitamin C + B

Lipids and fat-soluble nutrients

• Absorbed through the lymph vessels

• Vitamins A, D, E, and K

How are Nutrients Absorbed?

• Simple Diffusion

• Osmosis

• Facilitated Diffusion

• Active Transport

Simple Diffusion

• Movement of molecules into the small intestinal cell from a high concentration gradient to a low concentration gradient.

• Does not require a carrier protein and energy in order to proceed.

Osmosis

• Movement of water from a low concentration of nutrients to a high concentration of nutrients inside of the intestinal cell.

• Does not require energy and a protein carrier.

Facilitated Diffusion

• Movement of molecules from a high to low concentration inside of the intestinal cell.

• Requires a protein carrier

• Does not require energy

Active Transport

• Movement of molecules from a low to high concentration inside of the cell.

• Requires a protein carrier

• Requires energy

Large Intestine

• Comprised of the colon and the rectum

• Does not participate directly in digestion

• Involved in absorbing water, vitamins, and minerals

• Compacts unabsorbed substances into the feces

Large Intestine Long Transit Time

• Up to 24 Hours

Healthy Bacteria is needed for:

• Optimal gastrointestinal tract function

• Maintaining immune function and overall health

Unhealthy mircobiota contributes to:

• Inflammatory intestinal diseases (Crohn’s Disease)

• Chronic diseases (Obesity, Diabetes)

Functions of the Intestinal Microbiota

• Protection

• Immune System Maturation

• Metabolism

Intestinal Microbiota: Protection

• Maintenance of the intestinal mucosa layer and serves as a barrier.

• Modulate inflammation in the digestive tract.

• Prevent growth of disease-causing bacteria.

Intestinal Microbiota: Immune System Maturation

• Allows for the immune system to tolerate harmless bacteria and respond to harmful bacteria.

Intestinal microbiota: Metabolism

• Regulating energy intake, expenditure, and storage.

• Regulates glucose homeostasis

Probiotics

• Products containing live bacteria

• Common sources: Yogurt and Tablets

• Resides temporarily in the colon

• Healthy benefits

Prebiotics

• Food supply to stimulate bacterial growth and activity

• Typically passes undigested into the colon

• Dietary sources include: Bananas, onions, garlic, and artichokes.

Antigen

• Foreign substance, such as a protein.

• Stimulates as immune response when introduced into the body.

Antibody

• Protein produced by immune system cells.

• Destroys or inactivates foreign substances in the body

• Example: lymphocytes

Lymphocyte

• Targets Specific invaders directly

• Makes antibodies to destroy antigens

Phagocyte

• Targets invaders by engulfing and destroying it.

Peyer’s Patches

• Immune system cells located in the digestive tract.

• Small intestine

• Cells prevent harmful organisms or materials present in the digestive tract from making us sick.

Allergen Reaction of the Immune System

• 1st Time: Protein is absorbed intact, stimulates the immune system

• 2nd Time: The immune system recognizes the protein - allergic reaction

• Common symptoms: Hives and breathing difficulties

What is Gluten?

• A matrix formed by the proteins gliadin and glutenin.

Heartburn

• Also known as gastroesophageal reflux disease (GERD)

• Stomach acid leaking upward into the esophagus

• Symptoms: Burning sensation in the throat

• Attributed to overeating, anxiety, stress, pregnancy, disease processes.

Peptic Ulcers

• Open sores that develop on the esophageal lining.

• Erosion of the stomach or esophageal wall.

• Causes: Helicobacter pylori, use of aspirin or ibuprofen.

Alternative Feeding Methods

• Enteral nutrition

• Total parenteral nutrition (TPN)