Bio 46 Digestive System Nutrition PDF

Digestive System - Nutrition Nutrient – any substance taken in by an organism that is needed for survival, growth, development, tissue repair, or reproduction Nutrition – process of consuming and using food and nutrients Animals receive nutrients by consuming food Food processing in...

Digestive System - Nutrition Nutrient – any substance taken in by an organism that is needed for survival, growth, development, tissue repair, or reproduction Nutrition – process of consuming and using food and nutrients Animals receive nutrients by consuming food Food processing in animals Occurs in four phases Ingestion – food is taken into the body and moves into a digestive cavity (usually called the alimentary canal) Digestion – Food is broken down into smaller molecules Absorption – ions, water, and small molecules diffuse or are transported into the circulatory system Egestion – undigested materials and other wastes are passed from the body Animal Nutrition Five categories of organic nutrients Carbohydrates Proteins WHY? To provide energy – for synthesis of ATP Lipids To make new molecules Nucleic acids Vitamins Inorganic nutrients Water Minerals  Table 46.1 Table 46.1 Major Organic Nutrients in Animals Symptoms of deficiency Class of nutrient Dietary sources Functions in vertebrates in humans Carbohydrates All major food sources, Energy source; component Muscle weakness; weight especially starchy plants of some proteins; source of loss carbon Proteins All major food sources, Provide amino acids to make Weight loss; muscle loss; especially meat, new proteins; build muscle; weakness; weakened legumes, cereals, roots some amino acids used as immune system; increased energy source likelihood of infections Lipids All major food sources, Major component of cell Hair loss; dry skin; weight especially fatty meats, membranes; energy source; loss; hormonal and dairy products, plant oils thermal insulator; building reproductive disorders blocks of some hormones Nucleic acids All major food sources Provide sugars, bases, and None; components of phosphates that can be nucleic acids can be used to make DNA, RNA, synthesized by cells from and ATP amino acids and sugars Dietary categories Different animal physiologies can have different nutritional demands Herbivores – eat only plants Digestive systems contain microorganisms that help digest cellulose Carnivores – consume animal flesh or fluids Omnivores – eat both plant and animal material Essential nutrients Certain compounds cannot be synthesized from any ingested or stored precursor molecule – so they must be obtained in diet – called essential nutrients Four groups Essential amino acids Essential fatty acids Vitamins Minerals Essential amino acids (20) 9 amino acids are required by many animals, including humans that cannot be synthesized by animal’s cells Isoleucine, leucine, lysine, methionine, phenylalanine, histidine, threonine, tryptophan, and valine 11 amino acids that also make up proteins All 20 amino acids can be obtained from meat ???? Most plants do not contain every essential amino acid in sufficient quantity …???  Essential fatty acids Certain unsaturated fatty acids that cannot be synthesized by animal cells Unsaturated fatty acids found primarily in plants Strict carnivores obtain them from fish or adipose tissue of birds and mammals Vitamins Important organic nutrients that serve as coenzymes Water-soluble vitamins (like vitamin C) are not stored Fat-soluble vitamins (like vitamin A) are stored in adipose tissue  Table 46.2 (1) Table 46.2 Vitamins Required by Animals* Class of Dietary sources Functions in vertebrates Symptoms of deficiency in nutrient humans Water-soluble vitamins Biotin Liver; legumes; soybeans; eggs; Coenzyme for gluconeogenesis and fatty Skin rash; nausea; loss of appetite; nuts; mushrooms; some green acid and amino acid metabolism mental disorders (depression or vegetables hallucinations) Folic acid Green vegetables; nuts; legumes; Coenzyme required for synthesis Anemia (a lower than normal number whole grains; organ meats of nucleic acids of erythrocytes in the blood); (especially liver, kidney, heart) depression; birth defects Niacin Legumes; nuts; milk; eggs; meat Involved in many oxidation-reduction Skin rashes; diarrhea; mental reactions confusion; memory loss Pantothenic acid Nearly all foods Part of coenzyme A, which is involved in Burning sensation in hands and feet; numerous synthetic reactions, including gastrointestinal symptoms; formation of cholesterol depression Vitamin B1 Meats; legumes; whole grains Coenzyme involved in metabolism of sugars Beriberi (muscular weakness, (thiamine) and some amino acids anemia, heart problems, loss of weight) Vitamin B2 Dairy foods; meats; organ meats; Respiratory coenzyme; required for Seborrhea (excessive oil secretion (riboflavin) cereals; some vegetables metabolism of fats, carbohydrates, and from skin glands resulting in skin proteins lesions) Vitamin B6 Meats; liver; fish; nuts; whole grains; Coenzyme for over 100 enzymes that Seborrhea; nerve disorders; (pyridoxine) legumes participate in amino acid metabolism, lipid depression; confusion; muscle metabolism, and heme synthesis spasms  Table 46.2 (2) Table 46.2 Vitamins Required by Animals* Class of Dietary sources Functions in vertebrates Symptoms of deficiency in humans nutrient Water-soluble vitamins Vitamin B12 Meats; liver; eggs; some shellfish; dairy Required for erythrocyte formation Anemia; nervous system disorders foods leading to sensory problems; balance and gait problems; loss of bladder and bowel control Vitamin C Citrus fruits; green vegetables; Antioxidant and free-radical scavenger; aids in Scurvy (connective tissue disease (ascorbic acid) tomatoes; potatoes iron absorption; helps maintain healthy associated with skin lesions, connective tissue and gums weakness, poor wound healing, tooth decay); bleeding gums Fat-soluble vitamins Vitamin A Liver; green and yellow vegetables; Component of visual pigments; regulatory Night blindness due to loss (retinol) small amounts in some fruits molecule affecting transcription; important for of visual ability; skin lesions; impaired reproduction and immunity immunity Vitamin D Fish oils; fish; egg yolk; liver; Required for calcium and phosphorus Rickets (weakened, deformed bones) synthesized in skin via sunlight absorption from intestine; bone growth in children; osteomalacia (weak bones) in adults Vitamin E Meats; vegetable oils; grains; nuts; Antioxidant; inhibits prostaglandin synthesis Visual disturbances; possibly skeletal seeds; small amounts in some fruits and muscle atrophy; peripheral nerve vegetables disorders Vitamin K Legumes; green vegetables; some Component of blood clotting Reduced blood clotting ability fruits; some vegetable oils (olive oil, mechanism soybean oil); liver; synthesized by bacteria in the large intestine *Not all animals require each of these vitamins. Many mammals, for example, can synthesize vitamin C. Minerals Inorganic ions Various functions Cofactors or constituents of enzymes and other proteins Bone, muscle, nervous system function Contribute to changes in electrical differences across plasma membranes Many required in only trace amounts Less than 1 milligram/day  Table 46.3 (1) Table 46.3 Minerals Required by Animals Mineral Dietary sources Functions in vertebrates Symptoms of deficiency in humans Calcium (Ca) Dairy products; cereals; Bone and tooth formation; exocytosis of Muscular disorders; loss of bone; legumes; whole grains; green stored secretions in nerves and other reduced growth in children leafy vegetables; bones (eaten cells; muscle contraction; blood clotting by some animals) Chlorine (Cl) Meats; dairy foods; blood; Participates in electrical, acid-base, and Muscular and nerve disorders natural deposits of salt osmotic balance across cell membranes, notably those of neurons and heart cells Chromium (Cr) Liver; seafood; some nuts; Required for proper glucose metabolism, Disorders of lipid and glucose meats; mushrooms; some possibly by aiding the action of the balance in blood vegetables hormone insulin Copper (Cu) Fish; shellfish; nuts; legumes; Required for hemoglobin production and Anemia; bone changes liver and other organ meats melanin synthesis; required for connective tissue formation; serves as oxygen-binding component in some invertebrates Iodine (I) Seaweed; seafood; milk; iodized Required for formation of thyroid Inability to make thyroid hormones, salt hormones resulting in enlarged thyroid gland Iron (Fe) Liver and other organs; some Oxygen-binding component of Anemia meats; eggs; legumes; leafy hemoglobin; cofactor for some enzymes green vegetables Magnesium Hay; grasses; whole grains; Cofactor for many enzymes that use ATP Changes in nervous system (Mg) green leafy vegetables as a substrate function  Table 46.3 (2) Table 46.3 Minerals Required by Animals Mineral Dietary sources Functions in vertebrates Symptoms of deficiency in humans Manganese Nuts; whole grains; legumes; Cofactors for many enzymes Poor growth; abnormal skeletal (Mn) and vegetables; liver formation; nervous system disorders molybdenum (convulsions) (Mo) Phosphorus (P) Dairy foods; grains; legumes; nuts; Bone and tooth formation; component of Bone loss; muscle weakness meats DNA. RNA, and ATP Potassium (K) Meats; fruits; vegetables; dairy Participates in electrical, acid-base, and Muscle weakness; serious heart foods; grains osmotic balance across cell membranes, irregularities; Gl symptoms notably those of neurons and heart cells Selenium (Se) Seafood; eggs; chicken; soybeans; Antioxidant; cofactor for some enzymes Keshan disease (damage to and grains loss of heart muscle) Sulfur (S) Proteins from any source Component of two amino acids (methionine Inability to synthesize many proteins and cysteine) Sodium (Na) Many fruits; vegetables; meats; table Participates in electrical, acid-base, and Muscle cramps; changes in nerve salt osmotic balance across cell membranes, activities notably those of neurons and heart cells Zinc (Zn) Widely found in meats; fish; shellfish Many functions related to tissue repair; Stunted growth; loss of certain (oysters); grains sperm development; cofactor for many sensations like taste; impaired metabolic enzymes; required for certain immune function; skin lesions transcription factors to bind to DNA Types of Digestion Intracellular digestion (Only in simple invertebrates (e.g., sponges) ---- phagocytosis to bring food particles directly into a cell Cannot meet metabolic demands of active animal for long No mechanism for storing food Extracellular digestion (Occurs in most animals) Takes place in a cavity to protects interior of cells from hydrolytic enzymes Allows consumption of large food items Food enters digestive cavity, is slowly digested, then nutrients absorbed over a long period of time Alimentary canal Single elongated tube with an opening at both ends Contains smooth muscle Lined by epithelial cells Synthesize and secrete digestive enzymes Secrete hormones Transport digested material Several specialized regions Different environments for different processes Storage area Types of absorption Nutrients must be absorbed by the epithelial cells lining alimentary canal Three ways: Simple diffusion Facilitated diffusion Active transport Alimentary canal cells use some nutrients for their own needs but most are transported into blood for the rest of the body Alimentary canal or gastrointestinal (GI) tract mouth, pharynx, esophagus, stomach, intestines and anus + salivary glands, liver, gallbladder, and pancreas Functional regions of the alimentary canal Anterior end functions primarily in ingestion Mouth, pharynx (throat), and esophagus Middle portion functions : storage and initial digestion digestive organs (stomach) Upper part of small intestine and associated organs (liver, gallbladder, pancreas) Posterior part functions in final digestion, absorption, and elimination Remainder of small intestine and large intestine Undigested material defecated through opening (anus or cloaca) Structure of the GI tract Lumen lined by epithelial and glandular cells Secretory cells release a protective layer of mucus Other cells release hormones Glands release acid, enzymes, water, and ions Epithelial cells : surrounded by layers of smooth muscles, neurons, connective tissue, and blood vessels Neurons activated by sight and smell of food, presence of food in tract Mouth Presence of food stimulates salivary glands Saliva contains proteins, mucus, and antibacterial agents Functions of saliva Moisten and lubricate food to facilitate swallowing Dissolve food particles to facilitate taste Kill ingested bacteria Initiate digestion of carbohydrates with amylase Pharynx and esophagus Do not contribute to digestion or absorption Continues in esophagus by involuntary Swallowing begins in pharynx as peristalsis voluntary action The stomach Saclike organ: storing food Muscles helps break up food Partially digests proteins Regulates rate of emptying into small intestine Glands secrete Hydrochloric acid – kills microbes, dissolves particulate matter Pepsinogen – converted to pepsin to begin protein digestion Epithelium coated with alkaline mucus Action of stomach reduces food to chime - solution that contains water, ions, protein fragments, nucleic acids, carbohydrates, fat droplets, other small molecules Small intestine Most %food is digested (hydrolytic enzymes) Most food, water and minerals are absorbed Absorption accomplished in epithelial cells and then enter blood Mucosal infoldings : villi (finger like projections) Increase surface area 600-fold, thus more likelihood of food particle encountering digestive enzyme and being absorbed Produces GLP-1 (glucagon like peptide) GLP-1 roles Triggering insulin release from your pancreas: Insulin is an essential hormone that allows your body to use the food you eat for energy. It lowers the amount of glucose (sugar) in your blood. If you don’t have enough insulin, your blood sugar increases, leading to diabetes. Blocking glucagon secretion: Glucagon is a hormone your body uses to raise your blood sugar levels when necessary. So, GLP-1 prevents more glucose from going into your bloodstream. Slowing stomach emptying: Slower digestion means that your body releases less glucose (sugar) from the food you eat into your bloodstream. Increasing how full you feel after eating (satiety): GLP-1 affects areas of your brain that processes hunger and satiety. https://my.clevelandclinic.org/health/treatments/13901-glp-1-agonists 24 Villi structure Each villus has a Capillary – nutrients other than fat absorbed into blood Lacteal (part of lymphatic system) – allows for larger fat particles to enter, eventually dumped into blood Accessory organs Secrete substances into the duodenum – first part of intestine Bile contains bicarbonate ions (neutralize acids), cholesterol, phospholipids, organic wastes, and bile salts (break up fat droplets to increase their surface area) Large intestine Size varies among vertebrates Function: store and concentrate fecal matter and absorb remaining ions and water Defecation: feces are expelled through the anus as a result of muscular contraction and relaxation Bacteria produce vitamins and gas (flatus) Mechanisms of Digestion and Absorption in Vertebrates Carbohydrates: most are polysaccharides (starch and cellulose from plants and glycogen from animals), some monosaccharides and disaccharides Digestion Some polysaccharide digestion occurs in mouth, but most takes place in small intestine by pancreatic amylase, producing maltose Maltose and other disaccharides are broken down by enzymes on brush border of small intestine Monosaccharides transported across intestinal epithelium into the blood Proteins Broken down to polypeptide fragments by pepsin in the stomach and by proteases such as trypsin in small intestine Pancreas secretes enzymes as inactive precursors, and get activated in the small intestine Small intestine enzymes complete digestion of proteins into amino acids Transported into intestinal cells and into blood stream Lipids Most lipids ingested as triglycerides Digestion occurs almost entirely in small intestine Major digestive enzyme, lipase, secreted by pancreas Triglyceride -> 2 free fatty acids + 1 monoglyceride How? Process ===Emulsification Increases surface area, providing greater exposure to lipase Muscular contractions break up large droplets Phospholipids and bile salts prevent small lipid droplets from coalescing Lipids: Formation of micelles and chylomicrons Bile salts and phospholipids help form micelles, allowing lipids to diffuse into intestinal cells Triglycerides reform inside Smooth Endoplasmic Reticulum of m intestinal cells Aggregate into chylomicrons Released by exocytosis to pass into lacteals Fluid from lacteals eventually empties into blood circulation Figure 46.10 Access the text alternative for slide images. Vitamins, minerals and water Do not require digestion Absorbed in complete form Water-soluble vitamins absorbed by diffusion or active transport Fat-soluble vitamins (A,D,E, and K) follow pathway for lipid absorption Small amounts of water absorbed through stomach but most from small intestine Neural and Endocrine Control of Digestion Nervous system effects Local control of muscular and glandular activity by neurons in alimentary canal Signals up and down canal move digestion along Long-distance regulation by the brain Response to stimuli such as stress or sight and smell of food Hormones Secreted mainly by cells scattered throughout the epithelium of stomach and small intestine Gastrin released in response to presence of food in the stomach Stimulates smooth muscle contraction in stomach Pancreas and gallbladder stimulated by cholecystokinin (C CK) and secretin Stimulate secretion of digestive enzymes and bicarbonate ions Figure 46.11 Impact on Public Health Diarrhea Over 2 billion cases worldwide each year. Typically caused by infection, but many other causes Cholera caused by Vibrio cholerae from ingesting contaminated food or water Concern is loss of nutrients and water = dehydration Norovirus is responsible for nearly 1 million pediatric medical care visits annually (0.04% of children less than 5 ys in the USA) Heartburn (acid reflux) 1 in 4 in the U.S. suffer Caused by stomach acid rising into esophagus Many contributing factors Ulcers Erosion of alimentary canal Most common in lower esophagus, stomach, and small intestine Usually less than 1 inch wide If untreated, contents of lumen may leak into body cavity Almost 6% of Americans—or 14.8 million people—are diagnosed with peptic ulcers each year, according to a 2018 National Health Interview Survey conducted by the Centers for Disease Control and Prevention (CDC).  Obesity A person whose weight is higher than what is considered to be a normal weight for a given height is described as being overweight or having obesity. New CDC population data from 2023 show that in 23 states more than one in three adults (35%) has obesity. Fast Facts Data from the National Health and Nutrition Examination Survey (NHANES) -- NHI Nearly 1 in 3 adults (30.7%) are overweight. More than 2 in 5 adults (42.4%) have obesity. About 1 in 11 adults (9.2%) have severe obesity. About 1 in 6 children and adolescents ages 2 to 19 (16.1%) are overweight. Almost 1 in 5 children and adolescents ages 2 to 19 (19.3%) have obesity. About 1 in 16 children and adolescents ages 2 to 19 (6.1%) have severe obesity. 38 Ozempic Other names for this medication class include: Glucagon-like peptide-1 agonists. GLP-1 receptor agonists. Incretin mimetics. GLP-1 analogs. GLP-1 agonist medications work by mimicking this hormone. An agonist is a manufactured substance that attaches to a cell receptor and causes the same action as the naturally occurring substance. GLP-1 medications bind to GLP receptors to trigger the effects (or roles) of the GLP-1 hormone. The higher the dose of the GLP-1 agonist, the more extreme the effects. The satiety effect of GLP1-agonists reduces your food intake, appetite and hunger, thus resulting in weight loss. 39