digestive system PowerPoint

General Characteristics of the Digestive System

Digestion:

• The mechanical and chemical breakdown of foods into forms that cell membranes can absorb:

• Mechanical digestion breaks down large pieces of food into smaller ones, but does not change chemical composition

• Chemical digestion uses enzymes to break down food particles, by changing them into simpler chemicals

Digestive System:

• Organs of the digestive system carry out mechanical and chemical digestion, as well as ingestion, propulsion, absorption, and defecation

• The digestive system consists of the alimentary canal and accessory organs

Organs of the Digestive System

The digestive system consists of 2 portions:

• Alimentary canal:

• The food passageway

• Consists of organs that extend from the mouth to the anus

• Mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anal canal

• Muscular tube, about 8 m long

• Accessory organs:

• Consists of organs that empty secretions into alimentary canal

• Food does not pass through them

• Salivary glands, liver, gallbladder, pancreas

Structure of the Alimentary Canal Wall

Wall of alimentary canal is composed of 4 layers; from innermost to outermost, the layers are:

• Mucosa:

• Innermost layer, mucous membrane

• Folded in some areas, to increase surface area

• Absorbs dietary nutrients, secretes mucus and enzymes

• Submucosa:

• Connective tissue layer

• Nourishes cells, transports absorbed food molecules

• Muscularis (externa):

• Muscle tissue; contains circular and longitudinal layers

• Moves tube and food materials

• Serosa:

• Outermost layer; serous fluid eliminates friction

• Visceral peritoneum of organs within abdominal cavity

Movements of the Alimentary Canal Wall

2 types of movement in the alimentary canal:

• Mixing movements:

• Muscle in small sections contracts rhythmically

• Does not move materials in one direction

• Example: segmentation in small intestine, churning in stomach

• Propelling movements:

• Moves materials in one direction

• Peristalsis: Ring of contraction progresses down tube; propels food particles down the tract in wavelike motion

Innervation of the Alimentary Canal Wall

Branches of the sympathetic and parasympathetic divisions of the autonomic nervous system extensively innervate the alimentary canal:

• Submucosal plexus: Controls secretions

• Myenteric plexus: Controls gastrointestinal motility

Autonomic control of digestive activity:

• Parasympathetic impulses: Increase activities of digestive system (secretion and motility)

• Sympathetic impulses: Inhibit digestive actions (secretion and motility)

Enteroendocrine cells:

• Found in stomach and small intestine

• Secrete hormones to regulate Gl organs and processes

Mouth

The mouth:

• First part of alimentary canal

• Ingests food

• Mastication: Mechanical breakdown of solid particles, mixes them with saliva

• Functions as an organ of speech and sensory reception

• Surrounded by lips, cheeks, tongue, palate

• Includes oral cavity and vestibule

Cheek, Lips, and Tongue

Cheeks:

• Form the lateral walls of the mouth

• Contain muscles for facial expression and chewing

• Have an inner lining of stratified squamous epithelium (moist)

Lips:

• Highly mobile structures that surround the mouth opening

• Sensory receptors judge temperature and texture of food

• Boundary between skin and mucous membrane inside mouth

Tongue:

• Thick, muscular organ that occupies the floor of the mouth, and nearly fills the oral cavity when the mouth is closed

• Lingual frenulum: Connects tongue to floor of mouth

• Papillae: Projections that move food, contain taste buds

• Lingual tonsils: Lymphatic tissue masses on root of tongue

Palate

Palate:

• Forms the roof of the oral cavity

• Consists of an anterior portion, the hard palate, and a posterior portion, the soft palate:

• Hard palate consists of palatine processes of maxillae and palatine bones

• Soft palate consists of muscular arch, ends in uvula

• Palatine tonsils: Lymphatic masses on sides of tongue

• Pharyngeal tonsils (adenoids): Masses of lymphatic tissue in posterior wall of pharynx

Teeth

Teeth:

• Hardest structures in the body

• Not part of skeletal system

• Human dentition is that of omnivore (eating all types of food)

• 20 primary (deciduous) teeth

• 32 secondary (permanent) teeth

• Types of teeth: Central incisors, lateral incisors, canines (cuspids), first premolars (bicuspids), first molars, second molars, third molars

• Break food particles down to smaller pieces, beginning mechanical digestion

• Chewing mixes food with enzymes

• Incisors used for biting, canines for grasping and tearing, molars and premolars for grinding

• Consist of crown and root, which meet at neck

• Enamel covers crown, dentin makes up most of tooth and surrounds pulp cavity

• Periodontal ligament holds root in place, along with cementum

Dental Caries

Dental Caries:

• Cavities within enamel of a tooth

• Formed when sticky foods lodge between teeth or in crevices of molars

• Bacteria on teeth metabolize sugars

• Acidic by-products destroy enamel and dentin

According to the American Dental Association, the following may help prevent dental caries:

• Brush and floss

• Dental exams and cleanings

• Fluoride treatments

• Sealants

Salivary Glands

Salivary glands secrete saliva:

• Moistens food particles and binds them together

• Dissolves food so it can be tasted

• Contains enzymes (begin chemical digestion of carbohydrates) and bicarbonate ions (keep pH favorable for enzyme activity and protect teeth from acidic foods)

• 3 pairs of major salivary glands:

• Parotid glands: Largest; secrete serous saliva with amylase

• Submandibular glands: Floor of mouth; serous + mucous

• Sublingual glands: Under tongue; mainly mucous

• Many minor glands scattered throughout the mucosa of the tongue, palate, and cheeks; keep lining of mouth moist

Salivary Secretions

The different pairs of salivary glands have varying proportions of 2 types of secretory cells:

• Serous cells:

• Produce a watery fluid, containing a digestive enzyme called salivary amylase

• Amylase splits starch and glycogen into disaccharides

• Mucous cells:

• Secrete mucus

• Mucus binds food particles and lubricates food while swallowing

Pharynx and Esophagus

Pharynx and esophagus do not help in food digestion

Both the pharynx and esophagus have muscular walls, which function in swallowing

Pharynx:

• Cavity posterior to the mouth

• Extends from nasal cavity to esophagus

• Parts of pharynx:

• Nasopharynx: Posterior to nasal cavity; air passage; contain openings to auditory tubes

• Oropharynx: Posterior to oral cavity; air and food passage

• Laryngopharynx: Posterior to larynx; passageway to esophagus Esophagus:

• Tubular organ that extends from the pharynx to the stomach

Swallowing Mechanism

Swallowing can be divided into 3 stages:

• First stage:

• Voluntary stage

• Saliva is mixed with chewed food, forming a bolus

• Second stage:
  Starts as food reaches oropharynx, stimulates sensory receptors, and triggers swallowing reflex:

• The soft palate and uvula rises, to protect nasal cavity from food

• The hyoid bone and larynx elevate

• The epiglottis closes off top of the larynx, to protect trachea

• The longitudinal muscles of pharynx contract

• The inferior constrictor muscles relax and the esophagus opens

• Peristaltic waves force food into esophagus

• Third stage:

• Peristalsis transports food in the esophagus to the stomach

Esophagus

Esophagus:

• Muscular food passageway from the pharynx to the stomach (25 cm)

• Penetrates the diaphragm through the esophageal hiatus

• Contains mucous glands in submucosa, which moisten and lubricate lining of inner wall with mucus

• In muscularis, superior ⅓ is skeletal, middle ⅓ is skeletal + smooth, inferior ⅓ is smooth muscle

• Lower esophageal (cardiac) sphincter regulates food passage into stomach, and closes to prevent regurgitation of food

Stomach

Stomach:

• J-shaped, pouch-like organ, about 25 to 30 centimeters long

• Inferior to the diaphragm, in the upper-left portion of the abdominal cavity

• Rugae are folds of mucosa and submucosa that allow for distention

• The stomach:

• Receives food from the esophagus

• Mixes food with gastric juice

• Initiates protein digestion

• Has limited absorption

• Moves food into small intestine

• Contains the following layers of smooth muscle:

• An inner circular layer

• An outer longitudinal layer

• Some portions have third (innermost) layer of oblique fibers

Parts of the Stomach

Portions of the stomach:

• Cardia:

• Region near opening to esophagus

• Contains lower esophageal sphincter

• Fundus:

• Rounded area that rises above cardia

• Temporary food storage, which sometimes contains swallowed air

• Body:

• Main portion

• Lies between fundus and pylorus

• Pylorus:

• Distal portion, closest to small intestine

• Funnel-shaped pyloric antrum narrows to become pyloric canal

• Pyloric sphincter: Circular smooth muscle, controls gastric emptying

Gastric Secretions

Gastric glands contain 3 types of secretory cells, which produce a mixture called gastric juice. Components of gastric juice:

• Pepsinogen: Inactive form of pepsin; secreted by chief cells

• Pepsin: Active enzyme that beaks down proteins into polypeptides; forms from pepsinogen in presence of hydrochloric acid

• Gastric lipase: Fat-splitting enzyme, found in small quantities; action inhibited by low pH

• Hydrochloric acid: Produced by parietal cells; converts pepsinogen into pepsin

• Mucus: Secreted by mucous cells; provides lubrication and protects stomach lining

• Intrinsic factor: Produced by parietal cells; required for absorption of vitamin B12

Regulation of Gastric Secretion

Gastric juice is produced continuously

Rate of production varies, and is under neural and hormonal control

Neural regulation:

• Sympathetic impulses decrease gastric activity

• Parasympathetic impulses increase gastric activity; promote release of histamine, which stimulates gastric secretion

Hormonal regulation:

• Somatostatin: Inhibits hydrochloric acid secretion

• Gastrin: Increases gastric juice secretion

• Cholecystokinin (CCK): Released by small intestine cells when proteins and fat enter the small intestine; decreases gastric motility

Gastric Absorption

Gastric enzyme, pepsin, begins breaking down proteins

Wall of stomach is not well-adapted to absorb digestive

products

Most nutrients are absorbed in small intestine

The stomach absorbs these substances:

• Some water

• Certain salts

• Certain lipid-soluble drugs

• Some alcohol

Mixing and Emptying Actions

• The mixing of food in the stomach with gastric juice produces a semifluid paste called chyme

• Peristaltic waves push chyme toward pylorus of stomach

• Small amount of chyme is transported through pyloric sphincter at a time

• When peristaltic wave reaches distal portion of stomach, contents are pushed backward, resulting in mixing action

• Lower esophageal sphincter prevents backflow of chyme into esophagus

• Rate of emptying depends on consistency of chyme and type of food

• As chyme enters duodenum, accessory organs add secretions to act on chyme

• When chyme starts to fill the duodenum, stretch receptors initiate the enterogastric reflex; this slows stomach emptying and intestinal filling

Vomiting

Vomiting:

• Result of reflex that empties stomach in reverse direction

• Causes include certain drugs, toxins from food, overstretching of stomach, body motion changes, motion sickness associated with inner ears

• Controlled by vomiting center in medulla oblongata

• Motor response involves deep breath, raising of soft palate, closing of nasal cavity and glottis, relaxation of lower esophageal sphincter, contraction of diaphragm and abdominal wall muscles; forces food out through mouth

A Common Problem: Heartburn

• Stomachache results from eating a lot of food too quickly

• Takes up to 20 minutes for hypothalamus to sense full stomach

• Excess fullness leads to abdominal pain and gastric reflux, as stomach contents enter esophagus

• Stomach contents in esophagus cause inflammation, called esophagitis; feels like the pain is derived from the heart, so it is called heartburn

• Antacids can provide some relief

• Prevention: eat small meals, eat slowly, stay upright after eating, and avoid caffeine, nicotine, and alcohol

Pancreas

Pancreas:

• An endocrine gland, secreting insulin and glucagon to regulate blood glucose

• Also an exocrine gland of the digestive system, secreting digestive fluid called pancreatic juice

• Structure of exocrine pancreas:

• Pancreatic acinar cells make up most of pancreas, and release pancreatic juice into tiny ducts which lead to the pancreatic duct

• Pancreatic duct (along with the common bile duct from the liver and gall bladder) empties into the duodenum of the small intestine

• Pancreatic duct and Common bile duct join at dilated tube called the hepatopancreatic ampulla (of Vater)

• Hepatopancreatic sphincter (of Oddi) surrounds ampulla; controls movement of bile and pancreatic juice into duodenum

Pancreatic Juice

Pancreatic juice:

• Contains enzymes that digest carbohydrates, fats, proteins, and nucleic acids

• Components of pancreatic juice:

• Pancreatic amylase: Splits starch and glycogen into disaccharides

• Pancreatic lipase: Breaks down triglycerides

• Trypsin: Digests proteins; released as inactive trypsinogen, which is activated by enterokinase in small intestine

• Chymotrypsin: Digest proteins; released as inactive, activated by trypsin

• Carboxypeptidase: Digests proteins; released as inactive, activated by trypsin

• Nucleases: Digest nucleic acids

• Bicarbonate ions: Make pancreatic juice alkaline; buffer stomach acid

Regulation of Pancreatic Secretion

Hormones that help regulate the release of pancreatic juice:

• Secretin: Stimulates pancreas to release pancreatic juice high in bicarbonate ions

• CCK: Stimulates pancreas to release pancreatic juice high in enzymes

Nervous system regulation: During cephalic and gastric phases, parasympathetic impulses stimulate pancreas to secrete digestive enzymes

Liver and Gallbladder

Liver:

• Largest internal organ

• Located in the upper-right abdominal quadrant, just beneath the diaphragm

• Reddish-brown organ

• Well-supplied with blood vessels

Liver Structure

Liver has 4 lobes:

• Right lobe: Largest lobe

• Left lobe: Smaller than right lobe

• Quadrate lobe: Minor lobe, near gallbladder

• Caudate lobe: Minor lobe, near inferior vena cava

• Lobes consist of lobules, functional units of liver:

• Contain hepatocytes (liver cells) around central vein

• Hepatic sinusoids are channels for blood, between plates of cells

• Hepatic portal vein brings absorbed nutrients to sinusoids

• Hepatic artery brings oxygen-rich blood, which mixes with oxygen-poor blood from portal vein

• Blood flows from sinusoids to central veins, then to hepatic veins

• Bile flows from ductules to hepatic ducts, then to common hepatic duct

Liver Functions

The liver carries on many important activities:

• Produces glycogen from glucose

• Breaks down glycogen into glucose

• Converts non-carbohydrates to glucose

• Oxidizes fatty acids

• Synthesizes lipoproteins, phospholipids, and cholesterol

• Converts excess carbohydrates and proteins into fats

• Deaminates amino acids

• Forms urea

• Synthesizes plasma proteins

• Converts some amino acids to other amino acids

• Stores glycogen, iron, and vitamins A, D, and B12

• Phagocytizes damaged RBCs and foreign substances/antigens

• Removes toxins, such as alcohol and certain drugs from the blood

• Acts as blood reservoir

• Role in digestion is to secrete bile

Replacing the Liver

• The liver is required to maintain life

• Liver is capable of regeneration if 25 to 30% of it is healthy

• If cancer spreads to liver, life can continue only weeks to months

• Donor can donate part of the liver, as regeneration can occur

• There is a shortage of donor livers for transplant

• Extracorporeal liver assist device (ELAD) can temporarily perform blood-cleansing functions of the liver, until donor liver becomes available

• ELAD is "bioartificial," since it contains artificial portion (cartridges) and biological portion (human liver cells)

• Patient's blood plasma is passed through the ELAD, where toxins are removed and liver secretions are added; then plasma is returned to patient

Composition of Bile

Bile is a yellowish-green liquid that hepatic cells continuously secrete

Components of Bile:

Water

• Bile salts:

• Produced from cholesterol

• Emulsify fats

• Only bile component that have a digestive function (act as fat emulsifying agents)

• Bile pigments: Bilirubin and biliverdin, derived from hemoglobin breakdown

• Cholesterol

• Electrolytes

Jaundice:

• Yellowing of skin, eye sclerae, mucous membranes

• Caused by blockage of bile ducts, diseases, such as cirrhosis or hepatitis, or rapid red blood cell destruction

Hepatitis

• Hepatitis is an inflammation of the liver

• Many types, chronic or acute, types vary in severity

• Most common cause of hepatitis is one of several types of viruses

• Some people have symptoms, and some do not (they can still be carriers)

• Some forms are blood-borne

• Some forms are transmitted by contact with food, body fluids, or objects contaminated with feces that contain the virus

• Antibiotics are not effective against viral hepatitis

• Hepatitis A: Transmitted by contact with food or objects contaminated with feces containing the virus

• Hepatitis B: Transmitted by contact with body fluids containing the virus

• Hepatitis C: Transmitted through blood contact; half of all known cases of hepatitis

Gallbladder

Gallbladder:

• Pear-shaped sac

• Found on inferior surface of liver

• Cystic duct, only entry/exit duct, merges with common hepatic duct to form common bile duct

• Stores and concentrates bile

• Releases bile into duodenum of small intestine, via common bile duct at the hepatopancreatic ampulla

• Hepatopancreatic sphincter regulates release of bile into the duodenum

• Gallstones:

• Gallbladder normally concentrates bile salts, bile pigments, cholesterol

• Sometimes cholesterol precipitates and forms solid crystals

• Crystals can enlarge, forming gallstones

• Causes: Excess bile concentration, too much cholesterol secretion by liver, or inflammation of the gallbladder

• Bile release under control of hormone Cholecystokinin, which stimulates contraction of gallbladder

Functions of Bile Salts

Aid digestive enzymes through emulsification:

• Break up of large fat globules into smaller droplets (like soap or detergent)

• Aid in fat digestion by increasing surface area accessible to the enzyme lipase

Enhance absorption of fatty acids and cholesterol by forming micelles

Help absorb fat-soluble vitamins A, D, E, and K Almost all bile salts are recycled

Gallbladder Disease

• Symptoms of gallbladder disease:

• Pain in right upper abdominal quadrant, back and right shoulder

• Perhaps nausea and sweating

• Tests to observe the gallbladder:

• Ultrasonography of gallbladder, or an X-ray called a cholecystogram

• Gallstones can be found in the gallbladder, cystic duct, hepatic ducts, or the common bile duct

• Treatments:

• Cholecystectomy: surgical removal of the gallbladder

• Endoscopy to find stones or remove them from certain areas

Small Intestine

Small Intestine:

• Tubular organ that extends from the pyloric sphincter to the beginning of the large intestine

• Fills most of abdominal cavity

• Receives chyme from stomach, and liver and pancreatic secretions

• Completes digestion of the nutrients in chime

• Absorbs products of digestion

• Transports the remaining residue to the large intestine

Parts of the Small Intestine

Small intestine consists of 3 parts:

• Duodenum: Shortest and most fixed portion of small intestine

• Jejunum: Middle portion, thicker and more active than ileum

• Ileum: Distal portion; contains Peyer's patches (lymph nodules)

Jejunum and ileum are suspended by a double-layered fold of peritoneum called a mesentery, which transports blood and lymphatic vessels and nerves to wall of intestine

A double fold of peritoneum, called the greater omentum, drapes down from stomach, over the large intestine and folds of small intestine

Structure of the Small Intestinal Wall

• Tiny projections of the mucosa, intestinal villi, greatly increase the surface area for absorption of digestive end products

• Each villus consists of simple columnar epithelium with a core of connective tissue, with blood vessels (which absorb most nutrients), a lacteal (lymphatic capillary that absorbs large fats), and nerve fibers

• Free surfaces of epithelial cells contain microvilli, which also increase surface area for absorption

• Intestinal glands/crypts of Lieberkühn are located between bases of villi

• Plicae circulares are circular folds of mucosa, which also increase surface area

Secretions of the Small Intestine

Mucus:

• Secreted by goblet cells

• Also secreted by specialized Brunner's glands, that secrete a thick, alkaline mucus in response to certain stimuli

Watery fluid:

• Secreted by intestinal glands

• Picks up digestion products, and transports them into villi

• Does not contain digestive enzymes

Enzymes in the membranes of the microvilli:

• Peptidases: Break down peptides into amino acids

• Sucrase, maltase, lactase: Break down disaccharides into monosaccharides

• Lipase: Breaks down fats into fatty acids and glycerol

Regulation of Small Intestinal Secretions

Regulation of small intestine secretion occurs by these methods:

• Mucus secretion occurs in response to mechanical stimulation, or presence of irritants such as gastric juice

• Contact with chyme stimulates goblet cells to secrete mucus, and intestinal glands to secrete watery fluid

• Distension of the intestinal wall activates nerve plexuses in the wall of the small intestine

• Distension also stimulates parasympathetic reflexes that trigger the release of intestinal enzymes

Absorption in the Small Intestine 1

Villi increase the surface area for absorption

Small intestine is most important absorbing organ of alimentary canal

Absorption is so effective that very little absorbable material reaches the organ's distal end

Carbohydrate digestion and absorption:

• Salivary and pancreatic amylase break down starch and glycogen into disaccharides

• Intestinal enzymes break down disaccharides into monosaccharides

Monosaccharides are absorbed by facilitated diffusion and active transport, into the blood vessels in villi Protein digestion and absorption:

• Pepsin in the stomach breaks down proteins into polypeptides

• Pancreatic proteases (trypsin, chymotrypsin, etc.) break down proteins and polypeptides into smaller peptides

• Intestinal peptidases break peptides into amino acids

• Amino acids are absorbed by active transport into blood vessels of villi

Absorption in the Small Intestine 2

Fat digestion and absorption:

• Emulsified by bile salts

• Digested mainly by enzymes from pancreas and small intestine

• Digested into glycerol and fatty acids

• Fatty acids and glycerol are absorbed by a process involving several steps; absorbed into blood or lymphatic capillaries (lacteals)

Micelles and chylomicrons:

• Micelles: Loose complexes of fatty acids and bile salts, from which fatty acids can migrate to microvilli and be absorbed

• Fatty acids + glycerol are resynthesized into triglycerides in smooth
  ER

• New triglyceride clusters are encased in protein, forming chylomicrons

• Chylomicrons are absorbed by lacteals

Movements of the Small Intestine

The small intestine carries on the following movements:

• Peristalsis: Wave-like pushing movements that propel chyme in proper direction down the small intestine

• Segmentation: Ring-like contractions that move chyme back and forth (mixing movement)

Parasympathetic impulses stimulate both mixing and peristaltic movements, and sympathetic impulses inhibit them

If small intestine becomes over distended or irritated, a strong peristaltic rush may sweep contents quickly into large intestine, resulting in diarrhea

leocecal sphincter joins ileum of small intestine to cecum of large intestine, and helps regulate flow of chyme

Large Intestine

Large intestine:

• Named because diameter is greater than that of small intestine

• About 1.5 m long

• At distal end, opens to outside of body through the anus

• Absorbs some water and electrolytes

• Reabsorbs and recycles water and digestive secretions

• Forms and stores feces

Parts of the Large Intestine

Large intestine:

• Cecum:

• Pouch, forms beginning of large intestine

• Appendix is attached to cecum; lymph nodules in appendix function in the immune response

• Colon:

• Ascending, transverse, descending and sigmoid portions

• Contains hepatic (right colic) and splenic (left colic) flexures

• Rectum:

• Extends from sigmoid colon to anal canal

• Lies next to sacrum

• Anal canal:

• Last 2.5 to 4 cm of large intestine; opens to outside as anus

• Internal and external anal sphincters guard anus

Structure of the Large Intestinal Wall

• Wall has same 4 layers as other tubular organs of the alimentary canal

• Does not have villi and plicae circulares

• Longitudinal muscle is organized into 3 bands, taeniae coli, that run down entire length of colon

• Muscle bands create pouches called haustra, which help form feces

Functions of the Large Intestine

Large intestine:

• Has little or no digestive function

• Contains tubular glands containing goblet cells; secrete mucus, the only significant secretion of the large intestine

• Absorbs water (about 90% of water that enters it) and electrolytes

• Houses intestinal flora, bacteria which break down contents such as cellulose, and produce vitamins K, B12, thiamine

• Forms feces, and carries out defecation

• Intestinal gas: Mixture of nitrogen, oxygen, methane, carbon dioxide, hydrogen, ammonia, and hydrogen sulfide (causes unpleasant odor)

Movements of the Large Intestine

Movements of the large intestine:

• Similar to those of the small intestine

• Slower and less frequent than those of the small intestine

• Types of movements:

• Mixing movements

• Mass movements: Peristaltic waves, 2 to 3 times/day, which usually follow meals

• Defecation reflex:

• Eliminates feces from body

• Involves holding deep breath, contracting abdominal muscles

• Feces move into rectum

• Peristaltic waves occur in descending colon

• Relaxes internal anal sphincter, and then external anal sphincter

Feces

Feces are composed of materials not digested or absorbed, and also contain:

• Water (~75% of feces)

• Electrolytes

• Mucus

• Bacteria

• Bile pigments, which provide the color, after bacterial alteration The pungent odor is produced by bacterial compounds, including:

• Phenol

• Hydrogen sulfide

• Indole

• Skatole

• Ammonia

Disorders of the Large Intestine

• Diverticulosis:

• Weakening of intestinal wall leads to protrusion of mucous membrane

• Forms outpouchings that can become inflamed and infected

• Inflammatory bowel disease (IBD):

• Group of disorders, including:

• Ulcerative colitis: Affects mucosa and submucosa of large intestine; causes bloody diarrhea, cramps

• Crohn's disease: More serious; affects all layers, and occurs in both small and large intestines; causes diarrhea and pain

• Colorectal cancer:

• Cancer of large intestine or rectum

• Fourth most common cancer in the United States

• Screening tests include fecal occult blood test and colonoscopy

Life-Span Changes

Changes to the digestive system are slow and slight, and eventually include the following:

• Tooth enamel thins; teeth may become sensitive

• Gums may recede

• Teeth may loosen, break, or fall out

• GI tract becomes less efficient

• Slowing peristalsis may lead to heartburn

• Gastric secretion slows

• Constipation may become more frequent

• Nutrient absorption decreases, including fat-soluble vitamins

• Incidence of lactose intolerance increases

• Accessory organs age, but typically not necessarily in ways that affect health