The Digestive System Marki, Anastasia, and Pritch

What’s The Point? Breaks down food in order to gain three essential things: chemical energy, organic molecules and essential nutrients

Chemical Energy Energy that is in the form of molecular bonds created during photosynthesis Chemical energy in the form of starches is used in cellular respiration to create ATP

Organic Molecules Organic molecules are used as building blocks within the organism

Essential Nutrients Four different types: amino acids fatty acids vitamins minerals

Amino Acids Eight essential to humans and a ninth one Histidine is needed by babies Complete proteins such as meat have all eight Incomplete proteins such as corn or beans do not have all eight unless eaten together

Beans and other legumes Corn (maize) and other grains Lysine Essential amino acids for adults Tryptophan Isoleucine Leucine Phenylalanine Threonine Valine Methionine

Fatty Acids Few that animals cannot synthesize themselves: linoleic acid is necessary to make membrane phospholipids

Vitamins Organic molecules that perform various functions but cannot be synthesized within the body Vitamin B2 is FAD+ Water soluble are B and C, work as coenzymes Fat soluble A, K, and D work as building blocks

Minerals Inorganic elements Calcium and phosphorus used in building bones Iodine in hormones

Nourishment Under-nourishment- body does not have enough chemical energy Mal-nourishment- body does not have enough of a specific essential nutrient

Steps of Eating IngestionDigestion Absorption Elimination Undigested material Chemical digestion (enzymatic hydrolysis) Nutrient molecules enter body cells Small molecules Mechanical digestion Food Pieces of food

Types of Digestive Compartments Intracellular digestion versus extracellular digestion

Intracellular Digestion By phago or pino cytosis, food is ingested by cells and made into food vacuoles where they can be digested Occurs in sponges (filter feeders) and single-celled organisms

Extracellular Digestion Gastrovascular cavity: only a mouth Alimentary canal: mouth and anus

Fig Cecum Anus Ascending portion of large intestine Gall- bladder Small intestine Large intestine Small intestine Rectum Pancreas Liver Salivary glands Tongue Oral cavity Pharynx Esophagus Sphincter Stomach Sphincter Duodenum of small intestine Appendix Liver Pancreas Small intestine Large intestine Rectum Stomach Gall- bladder A schematic diagram of the human digestive system Esophagus Salivary glands Mouth Humans have extracellular digestion and an alimentary canal

Cnidaria- exhibit a gastrovascular cavity

Main Organs

Layers of Tissue

Linear Path Anus Liver Pancreas Small intestine Large intestine Rectum Stomach Gall- bladder A schematic diagram of the human digestive system Esophagus Salivary glands Mouth

Whole Body

Ingestion Mouth Salivary glands that secrete saliva Amylase hydrolyzes starch and glycogen Muchin lubricates mouth and food to avoid abrasion Buffer neutralizes acids Tongue regulates what goes into mouth by taste Bolus, a ball of food, is created and shoved back to the pharynx Pharynx: (fork between trachea and esophagus) epiglottis covers glottis opening to trachea

Pharynx

Ingestion Esophagus: muscles lining it Peristalsis- wave-like contractions that push food down in 5-10 seconds Sphincter- muscular rings in the esophagus that close off parts of the alimentary canal

Stomach

Digestion Stomach: Gastric Juice : HCL + pepsin Chyme: gastric juice + food Mucus Muscle

Digestion Small intestine (duodenum) - secretions from pancreas and gall bladder

Blood Sugar Homeostasis Homeostasis: 90 mg glucose/ 100 mL blood Stimulus: Blood glucose level rises after eating. Stimulus: Blood glucose level drops below set point.

Cecum Small intestine HerbivoreCarnivore Colon (large intestine) Stomach Small intestine

Large Intestine 90% water is recollected Includes the colon

Linear Flow Total Bloodstream Veins to heart Lymphatic system Small intestine Esophagus Stomach Lipids Mouth Hepatic portal vein Absorbed food (except lipids) Absorbed water Secretions from the gastric glands of the stomach Secretions from the pancreas and the liver Liver Rectum Anus Large intestine

Final Table Oral cavity, pharynx, esophagus Stomach Lumen of small intes- tine Epithelium of small intestine (brush border) Carbohydrate digestion Polysaccharides Smaller polysaccharides, maltose Polysaccharides Maltose and other disaccharides Disaccharides Protein digestionNucleic acid digestionFat digestion Proteins Small polypeptides Pepsin Pancreatic amylases Salivary amylase Disaccharidases Monosaccharides Small peptides Amino acids Polypeptides Smaller polypeptides Pancreatic trypsin and chymotrypsin Pancreatic carboxypeptidase Dipeptidases, carboxypeptidase, and aminopeptidase DNA, RNA Pancreatic nucleases Fat globules Nucleotides Fat droplets Nucleosides Nitrogenous bases, sugars, phosphates Nucleotidases Nucleosidases and phosphatases Glycerol, fatty acids, monoglycerides Bile salts Pancreatic lipase (starch, glycogen)(sucrose, lactose)

Diseases Crohn’s Disease Acid Reflux Disease Celiac Disease

Crohn’s Disease an inflammatory autoimmune disease Symptoms: primarily abdominal pain, diarrhea (usually with blood), vomiting or weight loss The immune system attacking the gastrointestinal tract and producing inflammation in the gastrointestinal tract No cure, but stem cell research is promising medication to control symptoms, maintain remission and prevent relapses

Crohn’s Disease Affects the ileum and the large intestine or both most commonly Structuring: narrowing of the bowel which can lead to bowel obstruction or changes in the caliber of feces Penetrating: creates abnormal passageways between the bowel and other structures like the skin Inflammatory: inflammation without causing strictures or fistula

Celiac Disease an autoimmune disorder of the small intestine that occurs in genetically predisposed people. Symptoms: chronic diarrhea, failure to thrive in children, fatigue. There are asymptomatic cases Treatment: a gluten free diet

Acid Reflux Acid is regurgitated and burns the esophagus Symptoms: Heartburn, Nausea, Chronic Salivation, Damage to esophagus Treatments are usually lifestyle (foods, positional therapy) changes along with medications and possibly surgery

Acid Reflux Reflux esophagitis Esophageal strictures Barrett's esophagus Esophageal adenocarcinoma—a rare form of cancer.

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