Internal Systems

Internal Systems The Digestive System

Learning Goals Specifically for the DIGESTIVE system: Students will: • Be able to explain the anatomy of the digestive system and the importance of digestion in providing nutrients needed for energy and growth • Begin to understand the relationship between the digestive system and the circulatory and respiration system • Be able to describe disorders relating to the digestive system

Organ and Organ Systems ORGAN Groups of different tissues specialized to carry out particular functions ORGAN SYSTEMS Group of organs that have related functions (ex) digestive, circulatory, respiratory, muscular, skeletal, endocrine, lymphatic, urinary, reproductive, nervous

Where do these fit in to MultiCellular Organisms Cells Tissues Organs Organ Systems Organisms

Monitoring Organs X-Rays (electromagnetic waves) • Bismuth (non toxic, opaque to x rays) CT Scan (Computerized axial tomography) • Much more complex: collection of images assembled to create cross sectional views Nuclear Imaging • Measures radiation emitted by the body and provides info about the FUNCTION of the organ as opposed to its structure NMR: Nuclear Magnetic Resonance • Shows structure and function of the organ • Subcategory: MRI

Animals Vs Plants Plants • Autotrophs • Nourish themselves using inorganic material Animals • Heterotrophs • Organisms that rely on organic molecules manufactured by other living things

Digestion across Different Organisms Single celled organisms • Digestion occurs in the vacuoles (protozoa), or by phagocytosis (amoeba) • Hydrolytic enzymes (use water to break down molecules) Simple Multi-cellular Organisms • Gastrovacular cavity: holds and digests food, emits waste Complex Organisms • Alimentary Canal (GI Tract) • Humans are about 6.9-9.0m in length

Components & Organs TWO COMPONENTS Gastrointestinal Tract (GI) Accessory Structures (Organs) • Mouth (Oral Cavity) • Pharynx • Esophagus • Stomach • Pancreas • Salivary glands • Small intestine • Liver • Large intestine • Gallbladder • Rectum • Anus • Appendix

The Four components of Digestion • INGESTION The taking in of nutrients • DIGESTION The breakdown of complex organic molecules into smaller components by enzymes • ABSORPTION The transport of digested nutrients to the tissues of the body • EGESTION The removal of waste food materials from the body

Enzymes What influences the rate at which digestive function enzymes? Temperature - In general as temperature increases, so does enzyme activity! BUT…this isn’t necessarily true for digestive enzymes • For most human enzymes (digestive), efficiency peaks at about 37 degrees Celsius pH Levels -Different enzymes function differently and more efficiently at different pH levels -Pepsin (low pH) -Amylase (Neutral pH) -Trypsin (High pH)

INGESTION 1. MOUTH (Oral Cavity) • Chemical and Mechanical Digestion Teeth • 8 Chisel shaped teeth called incisors used for CUTTING • 4 Canine teeth designed for tearing • 8 Pre-Molars for grinding • 12 Molars for crushing food **Each tooth has two divisions: The root and the crown** • Enamel crown is the hardest substance in the body • Dentin is part of the root structure and encases the pulp cavity, which contains nerves and blood vessels

INGESTION Saliva • Produced by the salivary glands, which contains the enzyme: Amylase: breaks down starches (complex carbohydrates) to simpler carbohydrates • Lubricates food for swallowing • Dissolves food particles and makes it possible to taste! 3 Sets of Glands: Parotid (largest), sublingual (smallest), and submaxillary Uvula: prevents food from entering pharynx

INGESTION 2. ESOPHAGUS • Pathway for food from mouth to stomach • The Bolus of food stretches the walls of the esophagus Peristalsis: rhythmic, wavelike contraction of smooth muscle that moves along the gastrointestinal tract

INGESTION Epiglottis: Prevents food from entering the trachea (respiratory system) by covering the glottis Regurgitation: movement of food back of your esophagus to your mouth

DIGESTION 3. THE STOMACH -The site of food storage and initial protein digestion (muscular and J-shaped) Entrance in and out of the stomach is regulated by SPHINCTERS (Act like draw strings on a bag)

DIGESTION • What Goes on in the Stomach??? - 3 layers of muscle work to break up food with the presence of gastric juices to form CHYME Gastric Juices • Mucus: protective layer • HCl (Hydrochloric Acid): kills harmful substances and converts pepsinogen to its active form pepsin • Pepsin: Protein digesting enzyme Ulcers: H-pylori bacteria

DIGESTION/ABSORPTION 4. SMALL INTESTINE • The small intestine is only 2.5cm in diameter but 7 meters in length! • The small intestine contains several permanent folds to increase surface area • As well, each of these folds contains villi which even further increase surface area and secrete juices!

DIGESTION/ABSORPTION Three Parts to the Small Intestine • Duodenum: 25 to 30 cm in length and is where the majority of digestion takes place (Widest) • Jejunum: 2.5m long, contains more folds than duodenum and breaks down remaining carbs and proteins • Ileum: 3m long, fewer and smaller villi and continue digestion and move food onto large intestine

PANCREAS • When food moves from the stomach to the small intestine, it is soaked in HCl and Pepsin • This it triggers a reaction! Acid causes Prosecretin (Inactive)→Secretin (Active) • Secretin is then absorbed into the bloodstream and carried by the circulatory system to the pancreas • Here, secretin acts as a chemical messenger, stimulating the release of pancreatic fluids (Bicarbonate Ions) • These ions released by the pancreas are then absorbed back into the duodenum and work to neutralize the HCl from the stomach

PANCREAS CONT’D • The pancreas also releases enzymes that promote the breakdown of three major components of food (proteins, carbs, and lipids) 1: Trypsinogen: released from liver, converted to trypsin when it reaches the S.intestine (by enterokinase) 2:Trypsin: Acts on partially digested proteins (long chain polypeptides → Shorter-chain polypeptides) 3:Erepsin: Shorter chain polypeptides→ Individual amino acids (from pancreas & S.Intestine)

THE LIVER & GALLBLADDER • The largest organ of the digestive system • The liver continually produces a fluid called bile that contains BILE SALTS (speed up fat digestion) • When the stomach is empty, bile is stored and concentrated in the gallbladder

THE LIVER & GALLBLADDER CONT’D Fats in the small intestine: • The hormone cholecystokinin (CCK) is released and carried in the blood to the gallbladder to trigger the release of bile salts • Once in the S.Intestine, bile salts break down the large fat globules to smaller droplets ***This is considered to be a mechanical digestion*** - This allows for faster absorption into the blood stream

4 Major Functions of the Liver • Synthesis: produce bile salts, stored in the gallbladder/manufactures blood protein • Breakdown: removes toxic nitrogen group from amino acids forming urea • Storage: glucose ↔ glycogen to maintain sugar levels • Detoxification: removes harmful compounds (alcohol)

ABSORPTION 5. LARGE INTESTINE • Only 1.5m long but the diameter is much larger (7.6cm) Components • Cecum: blind end which leads to the appendix • Colon: area where water and minerals are absorbed and bacteria break down what is left • Rectum: accepts feces and passes it along to the anal canal (last 20 cm of large intestine) • Anus: feces pass out of the body (controlled by sphincters)

EGESTION • Waste is expelled out of the body through the anus This concludes the process of digestion!

How Long Does It Take To Digest Food?? Approximately 24 to 72 hours depending on: • Food Ingested • Metabolic Rate

What Happens When We Eat a Meal? Homeostasis: describes the body’s ability to adjust to internal and external fluctuating environments! • The system of active balance requires constant monitoring and feedback The Human Body • 37 degrees celsius • 0.1% blood sugar • pH of 7.35

Homeostasis The thermostat analogy

Homeostasis and Digestion • The homeostatic controls over the digestive system act BEFORE food is absorbed • Seeing, smelling, and tasting all contribute to the release of gastric juices SECRETIN: released when foods travel from the stomach to the Small Intestine! GASTRIN: another hormone produced when partially digested proteins are present in the stomach! (homesostasis)

Speed of Food Digestion Large Meal: • A large meal will activate receptors , causing forceful contractions and faster emptying Meal High in Fat: - The small intestine will secrete a digestive hormone (enterogasterone) that slows peristaltic movements, allowing time for fat digestion and absorption!

Food Energy • We as humans are constantly using energy! How do we measure food energy • In canada, we use joules (j) or kilojoules (kj) • 1 Calorie = 4.18 J Basal Metabolic Rate (BMR) • The lowest energy needed to keep you alive, even in a relaxed state • Average Teenager: 9.5-12 kJ per day!

Metabolism • Is the sum of all chemical reactions that occur in the body Rank the activities by the amount of kJ/kg/h • Cooking • Playing piano • Sitting • Bowling • Sleeping • Singing • Badminton • Playing cards • Standing • Competitive cross country skiing • Running

Nutrients Amino Acids (20 total): we can synthesize ten in our body Fats: often get a bad name • absorb vitamins, insulate, protect delicate organs, protect nerves, cell membrane Vitamins: organic molecules that help change food into energy • Two kinds • Water soluble (cannot be stored) & Fat soluble (can be stored)

Nutrients Cont’d Minerals: elements that help change food into energy Antioxidants: lessen the danger of oxygen-free radicals • Free Radicals – created by exposure to sunlight, Xrays, ozone, tobacco smoke, etc. • Name some foods high in antioxidants?

Digestive Disorders Activity - Complete the digestive disorder worksheet!

Digestive Disorders Symptoms • Bleeding • Bloating • Constipation • Diarrhea • Heartburn • Incontinence • Nausea and vomiting • Pain in the belly • Swallowing problems • Weight gain or loss

Internal Systems