Nx Gastrointestinal

GOOD AFTERNOON

METABOLISM BY : JEANETTE C. SY, MD

GASTROINTESTINAL ( DIGESTIVE ) SYSTEM

Every cell of the body needs nourishment. The digestive system with the help of the circulatory system are responsible in delivering these nutrients to the cells.

ANATOMY OF THE DIGESTIVE SYSTEM DIGESTIVE SYSTEM - Consists of a.) DIGESTIVE TRACT - A tube extending from mouth to anus - consists of the oral cavity, pharynx, esophagus, stomach, SI, LI and anus

Digestive System b.) -

Associated organs that secrete fluids into the digestive tract Accessory glands – ex. Salivary glands Liver and pancreas

PERITONEUM - Body wall of the abdominal cavity - 2 layers : a. Visceral peritoneum - covers the organs b. Parietal peritoneum - lines the walls of the abdominal cavity

PERITONITIS - Inflammation of the peritoneal membranes - Can be life threatening

MESENTERIES - Connective tissue sheets which hold the organs inside the abdominal cavity in place - 2 types : 1. Lesser Omentum - connects lesser curvature of the stomach to liver & diaphragm 2. Greater Omentum - connects greater curvature of stomach to the transverse colon

RETROPERITONEAL - “Behind the peritoneum” - Abdominal organs which lie against the abdominal wall but with no mesenteries - Includes : duodenum pancreas ascending / descending colon rectum kidneys adrenal glands urinary bladder

TEETH Children = 20 teeth temporary / milk teeth “primary or deciduous teeth” Adults = 32 teeth permanent “secondary teeth” starts at age 5-7 years

TOOTH DISEASES 1. DENTAL CARIES - “Tooth decay” - Breakdown of enamel ( covers tooth) 5. PERIODONTAL DISEASE - Inflammation and degeneration of the periodontal ligaments, gingiva and bone

Functions of the Digestive System 1. Take in food - Food and water are taken into the body through the mouth

2. Break down the food - Through the process of digestion, the food is broken down from complex molecules to smaller molecules that can be absorbed

1. Absorb digested molecules - The small molecules are absorbed through the walls of the intestine for use in the body

1. Provide nutrients - The process of digestion and absorption provides the body with water, electrolytes, and other nutrients such as vitamins and minerals

1. Eliminate wastes - Undigested materials and waste products are excreted into the digestive tract and eliminated in the feces

DIETARY FIBER -

“CELLULOSE” - indigestible Important to normal digestive function Cellulose provides bulk or fiber in the diet To facilitate movement of material through the digestive tract by providing mass against which the muscular wall of the digestive tract can push

Digestion, Absorption and Transport

DIGESTION - Breakdown of food to molecules that are small enough to be absorbed into the circulation

TYPES : 2. MECHANICAL DIGESTION - Breaks large food particles down into smaller ones

1. CHEMICAL DIGESTION - Involves the breaking of covalent chemical bonds in molecules by the digestive enzymes

ABSORPTION - Begins in the stomach - Mostly occur in duodenum and jejenum and some in ileum

TRANSPORT - 3 WAYS 1. Facilitated diffusion 2. Co-transport 3. Active transport Note : # 2 & 3 require energy to move molecules across the intestinal wall

TRANSPORT MECHANISMS 1. SIMPLE DIFFUSION - Random movement of solute molecules from and area of high solute concentration to an area of low solute concentration

1. -

-

FACILITATED DIFFUSION A passive transport Energy NOT required Occur in any direction Move solutes from an area of high to an area of low concentration Use specific protein carriers molecules “FACILITATED DIFFUSION CARRIERS” Ex. Glucose transport = 4 STEPS :

3. ACTIVE TRANSPORT - Primary active transport - The protein carrier molecule of the cell membrane require energy (ATP) to transport molecules - WITHOUT ATP, THERE IS NO TRANSPORT!

4. COTRANSPORT - Secondary active transport - Require ATP indirectly from transport of Na+ molecules to transport another molecule - Ex. Na+ and glucose cotransport - 4 STEPS :

NUTRITION - Is all about the study of FOOD and how our body uses food as fuel for growth and daily activities - 2 Major Divisions : 1. Macronutrients - big 2. Micronutrients - small

PRINCIPLES OF NUTRITION

NUTRIENTS Are the chemicals taken into the body that provide energy and building blocks for new molecules Divided into 6 Major Classes : 3. Carbohydrates 4. Vitamins 4. Proteins 5. Minerals 5. Lipids 6. Water

I. ENERGY NUTRIENTS MACRONUTRIENTS : - Carbohydrates - Proteins - Fats Note : measured in grams (gm)

MICRONUTRIENTS : - Vitamins - Minerals

Note : measured in milligrams (mg), micrograms (ug) and international units (IU)

MACRONUTRIENTS

CARBOHYDRATES - Consist primarily of starches, cellulose, sucrose and small amounts of fructose (fruit sugar) and lactose (milk sugar) - Extra carbohydrates are converted into fat

PROTEINS - Are chains of amino acids - Are necessary to build tissues of the body like skin, muscles, organs - Can be used as a source of energy (ATP) - Excess are stored as glycogen and fats

LIPIDS / FATS - Include : TAG, phospholipids, steroids and fat-soluble vitamins - Extra fat can be use as fuel for the body or stored as fat

Triglyceride - TAG or triacylglycerol (3 fatty acids bound to glycerol) - Most common type of lipid - Also known as FATS

Types : 2. Saturated Fats - Fatty acids which have only one single bonds between carbons - Solid in room temp - Found in meat, eggs, nuts, dairy products, coconut and palm oil

2. Unsaturated Fats - Monounsaturated or Polyunsaturated - Have one or more double bonds btw carbons - Liquid in room temp - Found in most fish and plant oils

Fats are not soluble in water, thus, they are transported in the blood as lipid-protein complexes or LIPOPROTEINS

TYPES : 2. LOW-DENSITY LIPOPROTEIN (LDL) - “Bad Cholesterol” - Carry cholesterol to the tissues for the use by the cells - Excess are deposited on arterial walls (Atherosclerosis)

1. HIGH-DENSITY LIPOPROTEIN (HDL) - “Good Cholesterol” - Carry cholesterol from the tissues to the liver, where cholesterol is removed from the bloodstream and broken down or excreted in bile - Exercise = can elevate HDL

TRANS FAT - Are unsaturated fatty acids found when vegetable oils are processed and made more solid - Processing is done to promote food freshness and provide quality - Usually found in meat and dairy products - Can also increase LDL blood cholesterol which can lead to heart disease

FOOD

CARBOHYDRATE

MONOSACCHARIDES

LIPID

FATTY ACIDS

MONOGLYCERIDES

PROTEIN

AMINO ACIDS

CARBOHYDRATES Salivary MOUTH

amylase

POLYSACCHARIDES DUODENUM (Pancreas/Liver)

Pancreatic amylase

DISACCHARIDES SMALL INTESTINE Disaccharidases

MONOSACCHARIDES

MONOSACCHARIDES TRANSPORT 3. Monosaccharides are absorbed by COTRANSPORT into the intestinal epithelial cells 5. Monosaccharides move out of intestinal epithelial cells by FACILITATED DIFFUSION 3. They enter the capillaries of the intestinal villi and are carried through the hepatic portal vein to the liver

capillary 2 FD 1 CT

3 2 FD liver

Cell

GLUCOSE - carried from the liver by the circulation - Enters the cell by FACILITATED DIFFUSION - INSULIN facilitates entry of glucose into the cells

DIABETES MELLITUS - Lack of insulin (type 1 DM) or - Absence of normal effect (type 2 DM) - Result : not enough glucose is transported into many cells of the body - Thus : 1. cells do not have enough energy for normal function 2. blood glucose is high 3. large amount of glucose pass into the urine

LIPIDS MOUTH (SALIVARY GLANDS) STOMACH DUODENUM (PANCREAS/LIVER)

Bile Salts (Liver) Lipase (Pancreas)

SMALL INTESTINE

Lipase

FATTY ACIDS and MONOGLYCERIDES

EMULSIFICATION - First step in lipid digestion - Transformation of large lipid droplets into much smaller droplets - Accomplised by BILE SALTS

LIPID TRANSPORT • •

Bile salts surround fatty acids and monoglycerides to form MICELLES Micelles attach to the cell membrane of intestinal epithelial cells, and the FA and monoglycerides pass by SIMPLE DIFFUSION into the intestinal epithelial cells

3. W/in the intestinal epithelial cell, the FA and monoglycerides are converted to TRIGLYCERIDES (TAG); protein coat the TAG to form CHYLOMICRONS, which move out of the intestinal epithelial cells by exocytosis

4. The chylomicrons enter the lacteals (lymphatic capillaries) of the intestinal villi and are carried through the lymphatic system to the general circulation.

- CHYLOMICRONS : 1. are transported to the liver for storage or for use as energy 2. are transported to the adipose tissue where they are stored until an energy source is needed elsewhere in the body

Bile salts + lipids (FA+Monoglycerides) MICELLES simple diffusion intestinal epithelial wall TAG protein coat the TAG CHYLOMICRONS leave epithelial cells by exocytosis and enter Lacteals (lymphatic capillaries) LIVER OR ADIPOSE TISSUES (storage)

PROTEINS MOUTH (SALIVARY GLANDS) STOMACH

Pepsin

Smaller polypeptides

DUODENUM (PANCREAS/LIVER)

Trypsin Chymotrypsin Carboxypeptidase PEPTIDES

SMALL INTESTINE

Peptidases AMINO ACID

Amino acid + Na+ 1 COTRANSPORT INTESTINAL EPITHELIAL CELL 2 ACTIVE TRANSPORT

CAPILLARY

LIVER 3

AMINO ACID TRANSPORT •

• •

Amino acids are absorbed by COTRANSPORT into the intestinal epithelial cells Amino acids move out of the intestinal epithelial cells by ACTIVE TRANSPORT They enter the capillaries of the intestinal villi and are transported to the liver

MICRONUTRIENTS

VITAMINS Types : 2. Water-Soluble Vitamins - Vitamins C and B – complex - Not stored in the body - All are available as dietary supplements

1. FAT-SOLUBLE VITAMINS - Vitamins A, D, E and K - Stored in the liver

MINERALS - Inorganic nutrients essential for normal metabolic functions - Examples : Sodium, Potassium, Chloride, Calcium, Iron, Iodine Magnesium, Phosphate, Zinc

WATER - Approx 9L of water enters the digestive system each day - We ingest about 2L of water and the other 7L is from digestive secretions

Mouth (ingestion 2L) Salivary gland secretions (1L) Gastric secretions (2L) Pacreatic secretions (1.2L) / Bile (0.7L) Small Intestine secretions (2L)

WATER ABSORPTION Small intestine = 92% Large intestine = 6-7% Feces = 1%

II. ENERGY BALANCE METABOLIC RATE - Total amount of energy produced and used by the body per unit of time - Estimated by measuring the amount of OXYGEN used per minute - 1L Oxygen is estimated to produce 4.825 kcal of energy

METABOLIC ENERGY - Used in 3 Ways : 3. For basal metabolism 4. For muscle contraction 5. For assimilation of food

BASAL METABOLIC RATE (BMR) - Is the amount of energy expended at rest - It is the energy needed to keep the resting body functional - Calculated in expended kcal per square meter of body surface per hour - BMR for 70kg male = 38 kcal/m2/hr

What is an adequate diet?

CALORIC REQUIREMENTS • • •

CARBOHYDRATES – 60% PROTEINS - 10% FATS – not more than 30% - 8-10% saturated fats - upto 10% polyunsaturated fats - upto 15% monounsaturated fats

CALORIES PER GRAM 3. Carbohydrates = 4 4. Protein = 4 5. Fats = 9

FOOD GUIDE PYRAMID

Food Guide Pyramid - Suggests : 1. eat different amounts of foods from each basic food group 2. use fats and sugars sparingly 3. choose variety by eating the indicated number of servings per day

Recommended Daily Allowances Are the nutrient intakes that are sufficient to meet the needs of the nearly all the healthy people in the group (97%-98%) Note : RDA’s have been developed for different-aged males and females from infants to adults

FOOD LABEL The Daily Value on food labels are based on a 2000kcal reference diet

THANK YOU