Unit 8-The Digestive System and Nutrition

Mechanical digestion begins in the _____, and chemical digestion begins in the _____.

Mouth; mouth. The teeth and tongue begin the process of mechanical digestion of ingested food, and digestive enzymes in saliva begin the process of chemical digestion. Both occur in the mouth.

The tongue functions to _____.

Position food for chewing and swallowing. The tongue manipulates food so that it is crushed and ground by teeth, mixed with saliva, and easily swallowed. It also positions the food in the back of the mouth for swallowing.

When planning a healthy diet, what should your plate consist of?

-1/2 plate fruit + veg -1/4 plate grains + proteins -3 fat free or 1% fat sources of dairy per day

How many people with serious eating disorders die without treatment? with treatment?

-up to 20% without treatment -2-3% with treatment

What are the 3 regions of the small intestine? What are their functions?

1. Duodenum 2. Jejunum 3. Ileum Functions are chemical digestion and absorption

What is the primary role of the large intestine in digestion?

Absorbs ions, water, and vitamins to maintain homeostasis. The large intestine absorbs water, vitamins, and ions. It also adjusts the consistency of the feces.

19. What does BMR stand for?

Basal Metabolic Rate. The basal metabolic rate (BMR) is the minimal energy needed to keep an awake, resting person alive.

Blood flows from the small intestine to the liver through the _____, then from the liver to the inferior vena cava through the _____.

Hepatic portal vein; hepatic vein. Blood leaves the small intestine in veins that drain into the hepatic portal vein, which leads to the liver. Blood leaves the liver through the hepatic vein, which drains into the inferior vena cava.

What are the salivary glands and how are they involved in chemical digestion?

There are 3 salivary glands: 1. Sublingual (below tongue) 2. Submandibular (below jaw) 3. Parotid (in front of ears) -they release saliva into mouth -water moistens food -mucous binds food -enzyme, salivary amylase begins chemical digestion of starch

Which intake of fats should be avoided or limited?

Trans, saturated and polysaturated fat. We should reduce the amount of saturated fat (fat that is solid at room temperature) and trans fats in our diet in favor of unsaturated fats or oils (fats that are liquid at room temperature) and omega-3 and omega-6 fats.

What are the fingerlike projections along the surface of the small intestine called?

Villi. Covering the entire lining surface of the small intestine are tiny projections called villi.

Which of these are the digestive activities of the liver? a. Producing bile b. Regulating blood glucose levels c. Packaging lipids with proteins to form lipoproteins, which aid transport in the blood d. Removing poisonous substances e. All of these are digestive activities of the liver.

e. All of these are digestive activities of the liver. The liver is the largest internal organ with multiple functions, including many within the digestive system. Once the liver adjusts the composition of blood, the blood is returned to the general circulation.

What are minerals?

inorganic substances required for body processes

What is the pathway of the GI system?

mouth, pharynx, esophagus, stomach, small intestine and large intestine

What occurs in chemical digestion?

occurs in small intestine -carbs, fats, proteins, nucleic acids broken down into simplest forms -by enzymes of pancreas and small intestine -aided by bile from liver, stored in gallbladder and released into small intestine -aids in digestion and absorption of fats (bile)

What occurs in absorption?

occurs in small intestine -surface area of small intestine increased by pleated lining, villi and microvilli -each villus has network of capillaries and a lymphatic vessel (lacteal) -capillaries carry away absorbed products of protein and carbohydrate digestion (also ions and water) -lacteal carries away absorbed products of fat digestion in form of chylomicrons (protein coated products of fat digestion, soluble in water)

Describe carbohydrates

-4 calories per gram -complex > simple (complex contain more nutrients) -primary function is to provide energy -fiber is a type of carb that cant be broken down but helps lower LDL

Describe lipids.

-9 calories per gram -fats, oils, cholesterol -saturated and trans fat should be reduced in diet -should favour unsaturated fats, omega 3 and omega 6 fats -elevated blood cholesterol levels increases risk of cardiovascular disease

What is the function of the liver? What are 2 disorders?

-accessory organ -largest internal organ -nutrient laden blood from capillaries in villi of small intestine travel through hepatic portal vein to the liver -portal system = vien linking 2 capillary beds (hepatic portal system links capillary beds of villi in small intestine with capillary beds in liver) Involved in digestion: -produces bile -regulates blood glucose levels -packages lipids with proteins to form lipoproteins which aid transport in blood -removes poisonous substances -once liver adjusts composition of blood, it is returned to general circulation Disorders: 1. Cirrhosis -fat and scar tissue on liver -may be due to alcohol 2. Hepatitis -liver inflammation -liver stops filtering bilirubin from blood -results in jaundice -due to virus A, B, C, D, E or G

What is the function of the pancreas?

-accessory organ -makes pancreatic juices -contains many digestive enzymes (trypsin, amylase, lipase) -contains bicarbonate ions, important in neutralizing the acid in chyme -drains from pancreas into pancreatic duct which fuses with the common bile duct before entering the small intestine

What is the structure and functions of the gallbladder? What is an issue that can arise?

-accessory organ Structure: -muscular -pear shaped sac Function: -stores -modifies and concentrates bile produced by the liver Disorder: -gallstones -cholesterol and other substances build up around a particle -can be surgically removed

What is bulimia nervosa?

-binge eating huge amount of foods (up to 20,000 calories) -then purging via vomitting, laxitives, diuretics, exercise, enemas -due to psychological, social and physiological factors (anxious depression seems to be root) -leads to esophagus injuries, tooth decay and gum disease due to vomiting, dehydration, constipation and lyte imbalance

Describe proteins

-chains of amino acids -4 calories per gram -9/20 essential -complete protein = has all essential AAs -incomplete protein = lack 1 or more essential AAs -complementary proteins = combinations of incomplete proteins that supply all essential AAs together

How do teeth mechanically digest food?

-incisors clip and slice -canines puncture and tear -molars and pre molars crush

What is the Dietary Guidelines Advisory Committe (DGAG)?

-makes evidence based recommendations to federal government before guidelines released -focuses on whole foods, not nutrients -eat less red meat, more seafood and plant based proteins -sugar (not fat) is the major nutrient of concern -no calorie counting, should portion control

What is the structure and function of the large intestine?

-materials not absorbed by small intestine move to large intestine Structure (4 regions): -cecum -colon -rectum -anal canal Function: -absorbs most of the water remaining in the indigestible food residue -stores and eliminates feces

What is a persons basal metabolic rate (BMR)?

-minimal energy to keep awake person alive -60-70% of body's energy needs -depends on sex (males higher), muscles (require more energy) and age (metabolic rate decreases) -sum of BMR + # calories used in activity is amount of calories that should be consumed daily -do at least 2.5 hours of moderate physical activity per week

How is the stomach protected from gastric juice?

-mucous -pepsin (produced in inactive form) -neural and hormonal mechanisms that time gastric juice release to coincide with food entering stomach (food absorbs and dilutes gastric juice) -stomach lining replaced rapidly

How is the esophagus involved in digestion?

-muscular tube -transports food from pharynx to stomach -moved via peristalsis (rhythmic smooth muscle contractions) -no role in chemical or mechanical digestion

What are vitamins?

-needed in very small amounts -enzymes or co-enzymes -water soluble: C, B -fat soluble: A,D,E,K

Why do digestive secretions need to be controlled by both the nervous system and hormones?

-nervous system provides quick, anticipatory responses -hormones provide more timely processes examples: 1. saliva in mouth -anticipatory -neural control (food doesnt spend long in mouth) 2. gastric juice -neural control when stimulated by action of chewing -hormonal control (gastrin) when stomach distended 3. enzyme release from small intestine, pancreas and bile from gallbladder -triggered by neural -hormones released by small intestine also play a role

What is the colon? What are 4 disorders that can arise?

-part of large intestine Structure: -ascending (right) -transverse (top) -descending (left) Function: -absorbs water and ions -contains bacteria that produce vitamins -material left in large intestine after passing through colon called feces -feces pushed from large intestine into rectum which initiates the defecation reflex -feces move into anal canal -both internal sphincter (involuntary control) and external sphincter (voluntary control) must relax for defecation Disorders: 1. Diarrhea -material passes through colon too fast -not enough water absorbed 2. Constipation -material passes too slow -too much water absorbed 3. Diverticulitis -pouches (diverticula) in intestinal wall become infected and inflammed -diverticulosis = pouches form but no inflammation 4. colorectal cancer -begins with polyp that turns cancerous -detected via sigmoidoscopy (first 3rd of colon examined) or colonoscopy

What is the cecum? What is a disorder that can arise?

-part of large intestine -pouch at junction of small and large intestine -appendix extends from cecum (no digestive function, may have immune function) Disorder: -appendicitis -caused by blockage of appendix by stool, food or tumour -allows bacteria to multiply -antibiotics or surgery

How is the pharynx involved in digestion?

-passageway shared by respiratory and digestive systems involved in swallowing: -voluntary swallowing, tongue pushed bolus into pharynx -involuntary swallowing, reflex to prevent food from entering airway (soft palate prevents food from entering nasal cavities; larynx moves up and causes epiglottis to cover glottis)

How is the tongue involved in digestion?

-role in taste and food manipulation -large skeletal muscle -movement important in speech, food manipulation and forming bolus (soft mass of food that can be swallowed) -tastebuds to monitor food quality

What are the accessory glands/organs of the digestive tract?

-salivary glands -pancreas -liver -gallbladder

What is anorexia nervosa?

-self starvation -body weight <85% of normal weight chart

What is water important for in the body?

-transporting materials -lubricating and cushioning organs -temperature regulation -medium for chemical reactions

What are the 3 accessory organs in the digestive system?

1. Pancreas 2. Liver 3. Gallbladder

What do gastric glands of the stomach secrete?

1. hydrochloric acid (HCl) -kills bacteria -breaks down connective tissue of meat -activates pepsinogen to pepsin (digests protein) 2. Intrinsic factor -protein necessary for B12 absorption in small intestine

What are the 4 layers making up the walls of the GI tract?

1. mucosa -innermost, moist, mucous secreting 2. submucosa -connective tissue -has nerves, blood, lymph 3. muscularis -double layer of smooth muscle -except in stomach (3 layers) 4. serosa -outermost layer -epithelia tissue supported by connective tissue

Digestion of starch begins in the mouth with what enzyme?

Amylase. Salivary amylase is secreted in the saliva and begins starch digestion. Pepsin digests proteins in the stomach. Lipase acts on fats in the small intestine. Bicarbonate is not an enzyme; it functions as a buffer to neutralize the acidity of the chyme leaving the stomach.

Which of the following hormones functions to stimulate the release of digestive enzymes from the pancreas?

Cholecystokinin. Cholecystokinin causes the pancreas to secrete digestive enzymes and stimulates the gallbladder to release bile.

The primary function of the small intestine is to _____.

Digest and absorb nutrients. The small intestine is the primary site of food digestion and nutrient absorption.

After leaving the stomach, chyme enters the _____.

Duodenum. The duodenum is the first region of the small intestine. Chyme passes from the stomach into the duodenum, and then to the jejunum and ileum. The ileum is the last section of small intestine and empties into the cecum of the large intestine.

Peristalsis is _____.

Food moving along the esophagus and other regions of the GI tract. Food is moved through regions of the GI tract by rhythmic waves of smooth muscle contraction; this process plays no role in mechanical or chemical digestion.

The substance present in stomach secretions that does the most damage in heartburn is _____.

HCl. HCl has a very low pH, which burns the esophagus during reflux.

Without bile, one would be unable to digest _____, completely.

Lipids, found in butter and fried foods. Bile emulsifies fat, aiding in its complete digestion.

What are the complexes of glycerol, fatty acids, and bile salts formed in the lumen of the small intestine called?

Micelles. The products of fat digestion, glycerol, and fatty acids combine with bile salts to form micelles. When a micelle contacts an epithelial cell of a villus, the glycerol and fatty acids diffuse into the cell. The epithelial cell reassembles them into triglycerides, and then packages the fats into chylomicrons for transport.

What is the correct order of the organs that food passes through in the digestive system?

Mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus

Name three eating disorders.

Obesity, anorexia and bulimia. Obesity is an eating disorder with excessive food intake. Anorexia nervosa is an eating disorder that is a form of self-starvation, and bulimia is a disorder in which a person consumes a huge amount of food and then purges it from the body.

Chemical digestion of proteins is confined to which combination of organs in the digestive system?

Stomach and small intestine. Protein digestion begins in the stomach and is completed in the small intestine.

The primary function of the stomach is to _____.

Store and digest food. The stomach functions to store food, liquefy food, and initiate chemical digestion of proteins. It does not absorb food or digest fats.

What is the structure and function of the mouth (oral cavity)?

Structure -hard palate on roof of mouth towards front, reinforced with bone -soft palate on roof of mouth towards back, muscle only (prevents food from entering nasal cavities during swallowing) Functions: -begins mechanical digestion -begins chemical digestion -monitors food quality -prepares food for swallowing via moistening and manipulating (helped by teeth, salivary glands and tongue)

What is the structure and function of the stomach?

Structure: -J shaped expandable sac -band of circular muscle, sphincter, guards opening at each end (if sphincter into stomach weak = GERD) -Wall has 3 layers: 1. longitudinal 2. circular 3. oblique Function: -stores food and regulates release to small intestine -liquefies food to form CHYME -begins chemical digestion of proteins via secretion of gastric glands

What are the structure (including layers) and function of teeth? What are two issues that can develop?

Structure: -crown = above gum -root = below gum Layers: -pulp (innermost, has blood vessels and teeth) -dentin (hard, bone like) -enamel (non living, covers crown) Issues: 1. tooth decay -bacteria digest trapped foot and produce acid -acid erodes enamel, causes cavity -plaque (invisible layer of bacteria, mucous and food) promotes tooth decay 2. Gingivitis -inflammation of gums -can develop into periodontitis (inflammation of soft tissues and tooth; tooth may become loose)