Nutrition and Digestion 2023 PDF

Nutrition and Digestion Dr.A Zokari 2023 1  Nutrition is defined as the science of food and its relation to health.  What is nutrition and why is important? Eating a regular balanced diet and good nutrition helps fuel your body and maintain your...

Nutrition and Digestion Dr.A Zokari 2023 1  Nutrition is defined as the science of food and its relation to health.  What is nutrition and why is important? Eating a regular balanced diet and good nutrition helps fuel your body and maintain your brain ,muscles, bone nerves, skin, blood circulation and immune system.  And it is critical part of health and development.better nutrition is related to infant ,child and maternal health, stronger immune system and low risk diseases.  The term Nutrient is used for specific dietary constituents such as proteins, Fat, carbohydrates, vitamins and minerals.  These nutrients serve : a) As structural building blocks. b) Provide energy. c) Proceed chemical reactions in the body. dr. zokari 2 There are more than 40 kinds of nutrients in food but generally can be divided Into 7 major groups? Carbohydrates, proteins, fats, vitamins, minerals, dietary fiber and water. A healthy diet prevents malnutrition and protects from disease ,diabetes Cancer and stroke. Today , many people diets consist of more saturated fat, trans fats, sugar More sodium, than fruits, vegetable and dietary fiber. your body reflects what you put in it. Water is probably the most important essential nutrients that a person Needs. Every cell requires water to function. Any slight dehydration cause headache or any………… Water is also a macronutrient in the sense that the body needs in large Amount it dose not contain carbon or yield energy. Dr.zokari 3  Nutrients  Nutrients are organic and inorganic complexes in the food.  There are about 40 or more different nutrients normally supplied through the foods.  Nutrients may be divided into : 1)Macronutrients : These are proteins, fats and carbohydrates. They form the main bulk of food 2)Micronutrients : These are vitamins and minerals. They are called micronutrients because they are required in small amounts 4  PROTEINS  Proteins represent about 20 per cent of the body weight  Proteins are made up of smaller units, called amino acids.  20 amino acids are needed by the human body.  9 of these amino acids are called "essential" because the body cannot synthesize them in sufficient amounts , and therefore, they must be obtained from dietary proteins.  The rest are called non-essential amino acids, can be synthesized by the body  Both essential and non-essential amino acids are needed for synthesis of tissue proteins  Derived from Greek proteios meaning (of the first rank)due to important of this group of molecules. 5  Protein function large ,complex molecules that play many critical roles in the body  Proteins are needed by the body for  required for structure function regulation of the body tissues a) Body building specially in young child and infants b) Repair and maintenance of body tissues c) Maintenance of osmotic pressure d) Synthesis of certain substances like antibodies, enzymes, hemoglobin, hormones and clotting factors. 6  Sources of protein:(carbon,hydrogen,oxygen ,nitrogen)  Humans obtain protein from two main dietary sources: a) Animal sources: Proteins of animal origin are found in milk, meat, eggs, cheese and fish. These proteins contain all the essential amino acids in adequate amounts. b) Vegetable sources : Vegetable proteins are found in cereals, beans, nuts. They are poor in essential amino acids Best time of day to eat protein is morning ex. Egg beans, ….. 7  FATS  In normal human subjects, adipose tissue constitutes between 10 to 15 per cent of body weight.  Fatty acids are the building units of fat  Fats and oils are stored concentrated sources of energy.  Essential fatty acids are those that cannot be synthesized by humans. They can be derived only from food. 8 Fatty acids are divided into: a) Saturated fatty acids: found in animal fats(lack of double bonds And solid at room temperature (exception: coconut and palm oils are plants but have saturated FA) Bad may raise your cholesterol levels. LDL and HDL cholestrol b) Unsaturated fatty acids: found in vegetable oils (double bonds,liquid) good for health found in avocados (exception: fish oil although animal but contain unsaturated fat) 9  Functions of fats 1) Source of energy 2) Transport of fat-soluble vitamins through cell membrane 3) Support and protect viscera such as heart, kidney and intestine 4) Fat under the skin provides insulation against cold. 5) Precursors for hormones e.g steroids and prostaglandins 6) Maintains structural integrity of the cell membrane 10  CARBOHYDRATES  Carbohydrate is the main source of energy  Carbohydrates stored in the muscles and liver as glycogen  There are three main sources of carbohydrates: starches, sugar and cellulose. 1) Starch: is found in abundance in cereals (rice, wheat..etc) 2)Sugars: free sugars: monosaccharides(glucose, fructose,galactose) and disaccharides (sucrose, lactose and maltose). 3)Cellulose: is the indigestible part of carbohydrate with almost no nutritive value, it contributes to dietary fiber.  Fibers are found in foods of plant origin.  The fibers slow the absorption of sugars  Fibers also help in bulking and softening stool and decrease cholesterol absorption 11 Carbohydrates are composed of carbon, hydrogen and oxygen. Carbohydrates are group of organic compounds Oxygen and hydrogen In carbohydrates is same as in water 2:1 It typically breaks down in the animal body to release energy. Carboydrates gives energy and storge also energy. 12  Dietary fiber is made up of indigestible parts or compounds of plants Which pass relatively unchanged through our stomach and intestine. Fibers is mainly fibers. The main role of fibers is to keep the digestive system healthy. Vitamins are a group of substances that are needed for normal cell function, Grwoth, and development. There are 13 essential vitamins. This means that these vitamins are required for body to work properly. Vitamins and mineral are essential for body functions such as helping to Fight infection, wound healing, making our bones strong and regulating hormones. Vitamins and minerals can cause toxicity if consumed in large amounts. 13 Vitamins are organic substances means they are made by plants or animals Mineral are inorganic elements that come from soil and water. Your body needs large amounts of some minerals, such as calicum to grow and stay healthy Vitamins are classified into groups, based on their solubility. The fat soluble (A, D, E, K.)/ Water soluble are (B VITAMINS, VITAMINS C AND FOLATE. Vitamin A is important for normal vision ,immune system, reproduction And growth and development. Also vit A helps your heart lungs and other organs work properly. Vit E is antioxidant prevent our cell from dying especialy our skin cells. 14 The Digestion 15  The Digestive System  The Digestive system, also called the gut or gastrointestinal tract (GIT) tract, composed of long tube begins by the mouth and ends by the anus.  The accessory organs (salivary glands, liver, gallbladder, and pancreas) are not part of the GI but secrete substances into it via connecting ducts.  Digestive enzymes are secreted into the gut by glands located in the GI tract or by the accessory organs  Digestion: is the breakdown of food by mechanical and chemical processes converting It to small soluble molecules usable by cells. 16 17  The Mouth  The mouth or the oral cavity includes: lips, teeth, tongue, palate and muscles of mastication in the cheeks.  The food is digested in the mouth mechanically and chemically.  Mechanical digestion is by: - Teeth which tear and grind food to break it into small pieces. - The tongue and lips move the food and role it from side to side mix it with saliva to make soft and easy to swallow - The palate (hard and soft parts) and uvula help in swallowing  Chemical digestion: - Very little, some carbohydrates are digested by enzyme in the saliva (salivary amylase) (by lingual glands) 18  The Salivary Glands  Salivary glands are 3 pairs of exocrine glands secrete saliva to the mouth by ducts  Salivary glands are: parotid, sublingual and submandibular  Saliva contains: - 99.5% water and 0.5% electrolytes( K+ , Na+ and bicarbonate) - Enzyme ptyalin (an α amylase enzyme) - Mucus secretion for lubrication and protection - Antibacterial substances for protection. 19 20  The Pharynx  Is a region between the mouth and the esophagus  Consists of nasopharynx, oropharynx and laryngopharynx.  It is a common passage between the digestive and respiratory system  During swallowing the food: - The tongue move back pushing the bolus towards the pharynx - The soft palate and uvula moves up closing the nasopharynx - The trachea moves upward and the epiglottis close the opening of larynx - Then food enters the esophagus  Secretion in the pharynx is limited to mucus from goblet cells. 21 22  Esophagus  Is a muscular tube lying posterior to the trachea.  It lays between the pharynx and stomach  Rhythmic contractions of esophagus called peristalsis, push the food toward the stomach. It takes less than 10 sec.  It secretes a mucus by its glands.  No digestion or absorption occurs here  Has two sphincters: upper and lower esophageal sphincters. - The upper sphincter prevents return of food to the mouth - The lower one prevents the acidic contents of stomach from returning to the esophagus and causing (heartburn). 23 24  The Stomach  A hollow, J-shaped organ that can be store as much as 1.5 liters of food for four to six hours.  It connects with esophagus in one end and the small intestine at the other end  Composed of upper fundus, the body and antrum (pylorus).  Internally, the wall has long folds called Rugae.  These folds have millions of gastric pits that connect with the gastric glands deep in the mucosa. 25  Secretion and Digestion in the Stomach  Mechanical digestion: by the movement of gastric muscles.(circular,longitudinal and oblique) The food is broken more and mixed with gastric juice  Chemical digestion by: 1) Mucus secreted from specialized cells. Protects the stomach wall from stomach acid (HCL) (no goblet cell in stomach). 2) Parietal cells secret: HCl to destroy the toxins in food as bacteria and denature the complex proteins and activate pepsinogen to pepsin enzyme, and lowers the pH - Parietal cells also secretes intrinsic factor which help in the absorption of vit. B12 in the ileum 26 3) Chief cells secret pepsinogen (inactive enzyme), the active pepsin coverts protein to small peptides. 4) Pyloric glands secretes hormone gastrin which regulates acid secretion  The food in the stomach finally become semi liquid (chyme)  Absorption is very little: e.g some water, alcohol and aspirin 27  Stomach Functions 1) Food storage 2) Convert the food into semi liquid chyme. 3) Delivers the chyme to the small intestine in small amounts 4) Digests proteins to peptides by pepsin 5) Help in vitamin B12 absorption by secreting internsic factor 6) HCL kills most of the bacteria that enter with food. 28  Small Intestine  Its length about 6m.  Completes digestion and absorption of nutrients  Is divided into 3 segments: duodenum, jejunum and ileum.  Its wall contains fingerlike projections called villi.  Villi are covered with simple columnar epithelium  Between the epithelial cells are mucous-secreting goblet cells.  Each villus contains a central lymphatic vessel called lacteal which is surrounded by blood capillaries.  All nutrients are absorbed into the blood capillaries, but fatty acids are absorbed to the lacteal. 29 30  Small intestine  On the surface of the villi are small finger like projections called microvilli  Microvilli are folding of the cell membrane of the villi.  The microvilli produce a brush border on the edges of the columnar epithelium  Brush border contains serves to increase surface area of absorption.  The brush border (cell membrane) contain digestive enzymes, the chyme in the lumen exposed to these enzymes  Brush border enzymes hydrolyze disaccharides, polypeptides … etc. into smaller molecules. 31  The Duodenum  The first part of the small intestine (12 cm long)  The acidic chyme from stomach stimulates the duodenum cells to secret hormones : secretin & cholecystokinin (CCK)  These hormones stimulate the pancreas and the gall bladder to release their juices respectively.  The chyme is mixed with bicarbonates (from bile and pancreas) which neutralize the chyme , thus activating the enzymes  There are 3 secretions in the duodenum: a) Pancreatic juice b) Bile from the liver c) Intestinal juice. 32 33  Digestion in the duodenum Pancreatic juice: Contains sodium bicarbonate and the enzymes: 1)Pancreatic amylase: digest starch into disaccharide (maltose) 2) Trypsin and chemotypsin: digest protein into small peptides 3) Lipase digest the fat into fatty acids + glycerol Bile salts: synthesized in the liver cells and stored in the gall bladder In order to concentrate the bile pigment. Bile salts break the fat into fat droplets (small particles) by emulsification Intestinal juice: are the brush border enzymes: 1) Digest maltose by enzyme maltase into 2 glucose 2) Digest lactose by enzyme lactase into glucose + galactose 3) Digest sucrose by enzyme sucrase into glucose + fructose 34  Absorption of nutrients  The amino acids, monosaccharides and most vitamins and minerals are absorbed in the jejunum.  Bile salts, vit. B12 , electrolytes, and water are absorbed in the ileum  Around 8-10 liters of fluid are absorbed in the small intestine /day. 35  Role of the Bile  The liver hepatocytes produce bile which is stored in gallbladder.  Composition of bile: Bile is yellow-green, alkaline solution containing bile salts, cholesterol, bile pigments, fatty acids, phospholipids and electrolytes.  Functions: 1) Emulsify fat in which the large fat are converted to fat droplets that help the pancreatic lipase to digest fat. 2) Facilitate fat and cholesterol absorption: digestion products (fatty acids and glycerol) form micelles with bile salts. the micelles carry the fat to the brush border where it inters into the cell but the micelles go back to the lumen 36  In the intestinal cell the fat products form the chylomicron  Chylomicrons are absorbed from cells to lacteal.  They circulate through lymphatic vessels and finally return to the blood  In the blood, the triglyceride removed from chylomicrons by the enzyme lipoprotein lipase which is attached to the lining of blood vessels.  This enzyme digests TG again to fatty acids and monoglycerol for use by the cell.  The remaining particles as cholesterol are taken up by the liver to be metabolized. 37  The large intestine  Consists of cecum, colon (ascending, transverse and descending and sigmoid parts), rectum and the anus.  It is shorter and wider than small intestine.  The cecum ends by the appendix 38  Absorbs most water, and electrolytes from the chyme.  Absorbs vitamins K, and B which are produced by the bacteria.  Bacteria ferment undigested materials and give color and odor of the feces.  The colon secrets mucus which holds the fecal matter together 39 What is the function of gastrin and secretine? Secretin also inhibits the secretion of gastrin. Which triggers the initial release of the hydrochoride acid Into the stomch ,and delays gastric empting. 40  What dose secretin cause the release of? Secretin functions as a type of fireman: it release in response to acid in the small Intistine,and stimulates the pancreas and bile ducts to Release a flood of bicarbonate base which neutralized The acid What is the differences between secretin and cholecystokinin is that the secretin is produced by s-cell in Duodenum and jejenum while cholecystokinin secreted by I cell In duodenum ( all from cells of duodenum) 41  Secretin inhibits the secretion of gastrin which triggers the initial Release of HCLinto stomach and delays gastric emptying Secretin stimulates the flow of bile from the liver to the gall bladder. CCK stimulates the gall bladder to contract causing bile to be Secrted into the duodenum dr. Ahmed Zokari 2023-2024 42