ch17 lecture - Mr. B's Science Pagemrbssciencepage.weebly.com/uploads/7/9/7/4/7974541/ch17_lectur… · Chapter 17 Lecture Outline See separate PowerPoint slides for all figures and

10/24/2016

1

1Copyright © McGraw-Hill Education. Permission required for reproduction or display.

Chapter 17Lecture Outline

See separate PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes.

Introduction

2

• Main portion of the digestive system is a long tube extending through the body

• The inside of the digestive tube is part of the outside world, not the internal environment

• The pH, electrolyte composition and water volume of the internal environment are carefully regulated, but these change in the digestive tube, according to the food we eat

• Food materials that enter the digestive tube are broken down into their building blocks (sugars, amino acids, nucleotides, fatty acids, glycerol)

• Building blocks are absorbed across the wall of the tube

• Once absorbed, building blocks are used to create the molecules needed by the body

17.1 Overview of the Digestive System

3

Digestion:The mechanical and chemical breakdown of foods into forms that cell

membranes can absorb:

• Mechanical digestion breaks down large particles into smaller ones, but

does not change chemical composition

• Chemical digestion breaks down food particles by changing them into

simpler chemicals

Digestive System:• Organs of the digestive system carry out mechanical & chemical

digestion, as well as ingestion, propulsion, absorption and defecation

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

The digestive system consists of 2 portions:

• Alimentary canal:Consists of organs that extend from the mouth to the anus; the food passageway

• Accessory organs:Consists of organs that empty secretionsinto the alimentary canal; food does notpass through them

Organs of the Digestive System

4

• The alimentary canal is a

muscular tube about 8 m

long

• Passes through the

thoracic & abdominopelvic

cavities

General Characteristics of the Alimentary Canal

5

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

• Mucosa: innermost layer, mucous membrane

• Submucosa: nourishes cells, transports absorbed food molecules

• Muscularis: muscle tissue, moves tube and food materials

• Serosa: outermost layer; serous fluid eliminates friction

Structure of the Wall

6

10/24/2016

2

The wall of the small intestine shows the 4 layers of the wall of the alimentary canal: mucosa, submucosa, muscularis, serosa

Structure of the Wall

7

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

Propelling movements:• Moves materials in one

direction

• Peristalsis: ring of contraction

progresses down tube; propels

food particles down the tract

Movements of the Tube

8

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)

Innervation of the Tube

9

17.2: Mouth

10

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

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

Cheek and Lips

11

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

Tongue

12

10/24/2016

3

Palate: • Forms the roof of the oral

cavity

• Consists of a hard (bony)

anterior part and a soft

(muscular) posterior part

• The uvula extends from

the soft palate

• Palatine tonsils: lymphatic

masses on sides of tongue

• Pharyngeal tonsils (adenoids):

masses of lymphatic tissue

in posterior wall of pharynx

Palate

13

Teeth: • Hardest structures in

the body

• 20 primary (deciduous)

teeth

• 32 secondary

(permanent) teeth

Teeth

14

15 16

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

Prevention:• Brush and floss

• Dental exams and cleanings

• Fluoride treatments

• Sealants

Clinical Application 17.1

17

Mouth Parts and Their Functions

18

10/24/2016

4

17.3: Salivary Glands

19

Salivary glands secrete saliva:

• Moistens food particles and binds them together

• Dissolves food so it can be tasted

• Saliva 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

• Submandibular glands

• Sublingual glands

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

The different pairs of salivary glands have varying proportions of 2 types of secretory cells (serous cells and mucous cells):

• Serous cells produce a watery fluid, containing a digestive enzyme called salivary amylase, which splits starch and glycogen into disaccharides

• Mucous cells secrete mucus, which binds food particles and lubricates food while swallowing

Salivary Secretions

20

3 Major Pairs ofSalivary Glands:

Parotid glands:• Largest in body• Anterior/inferior to ear• Serous glands• Saliva contains amylaseSubmandibular glands:• Serous + mucous glands• Floor of mouthSublingual glands:• Under tongue• Mainly mucous glands

Major Salivary Glands

21


22

Parotid gland Submandibular gland Sublingual gland(serous) (mixed: serous + mucous) (mainly mucous)


23

17.4: Pharynx and Esophagus

24

• The pharynx is a cavity posterior to the mouth

• Pharynx extends from nasal cavity to esophagus

• The esophagus is the tubular organ that extends from the pharynx to the stomach

• Pharynx and esophagus do not help in food digestion

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

10/24/2016

5

The pharynx connects nasal and oral cavities, and can be divided into the following parts:

• Nasopharynx

• Oropharynx

• Laryngopharynx

Structure of the Pharynx

25

Swallowing can be divided into 3 stages:• First stage:

Voluntary stage, in which saliva is mixed with chewed food, forming a bolus

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

• The soft palate and uvula raise, 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

Swallowing Mechanism

26

27

Esophagus:• A muscular food passageway from the pharynx to the stomach (25 cm)

• Penetrates the diaphragm through the esophageal hiatus

• Contains mucous glands in submucosa

• Lower esophageal (cardiac) sphincter regulates food passage into stomach

Esophagus

28

17.5: Stomach

29

Stomach:• J-shaped, pouch-like organ, about 25-30 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

• The stomach contains the following layers of smooth muscle:

• An inner circular layer

• An outer longitudinal layer

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

4 parts of the stomach:

Cardia, fundus, body, and pylorus

Parts of the Stomach

30

10/24/2016

6

Radiograph of the stomach

Parts of the Stomach

31

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

Gastric Secretions

32

Lining of the Stomach

33

Components of Gastric Juice

34

• 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

Regulation of Gastric Secretions

35

Regulation of Gastric Secretions

36

10/24/2016

7

Phases of Gastric Secretion

37

• Gastric enzyme, pepsin, begins breaking down proteins

• Wall of stomach is not well-adapted to absorb digestive products

• The stomach does absorb:

• Some water

• Certain salts

• Certain lipid-soluble drugs

• Some alcohol

Gastric Absorption

38

• 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

Mixing and Emptying Actions

39

• When chyme starts to fill

the duodenum, stretch

receptors initiate the

enterogastric reflex

• This slows stomach

emptying and intestinal

filling

Mixing and Emptying Actions

40

A Common Problem: Heartburn

• Stomachache results from eating a lot of food too quickly

• It 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


41

17.6: Pancreas

42

• The pancreas is an endocrine gland, secreting insulin and glucagon to regulate blood glucose

• Pancreas is also an exocrine gland of the digestive system

• In its exocrine function, it secretes digestive fluid called pancreatic juice

10/24/2016

8

• Pancreatic acinar cells make up most of pancreas, and release pancreaticjuice 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

Structure of the Pancreas

43

The pancreas has a large head, that fits into the curvature of the duodenum. The tail of the pancreas lies against the spleen.

Structure of the Pancreas

44

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

Pancreatic Juice

45

Regulation of Pancreatic Secretion

46

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

Regulation of Pancreatic Secretion

47

17.7: Liver

48

Liver:• Largest internal organ

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

• Reddish-brown organ

• Well-supplied with blood vessels

10/24/2016

9

Liver has 4 lobes:

Right lobe: largest

Left lobe: smaller than right lobe

Quadrate lobe: minor lobe, near gallbladder

Caudate lobe: minor lobe, near inferior vena cava

Liver Structure

49

Liver lobes are divided into hepatic lobules; these are the functional units of the liver. Lobules consist of plates of hepatic cells radiating out from a central vein. Hepatic sinusoids run between plates of cells. 50

Oxygen-poor blood from the digestive tract is transported to the liver through the hepatic portal vein. It mixes with oxygen-rich blood from the hepaticartery. This blood filters through the hepatic sinusoids. Hepatocytes adjust nutrient concentrations, as the nutrients from the digestive tract flow by. Bile produced by hepatocytes leaves the liver through bile ducts. 51

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

Liver Functions

52

Major Functions of the Liver

53

Replacing the Liver

• The liver is required to maintain life

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

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

From Science to Technology 17.1

54

10/24/2016

10

• 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

Composition of Bile

55

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 C accounts for about half of all known cases of hepatitis


56

• Gall bladder is a pear-shaped sac on inferior surface of liver

• It stores and concentrates bile

• Cystic duct from gall bladder joins with the common hepatic duct from liver to form common bile duct

• Bile duct empties into the duodenum, via the hepatopancreatic ampulla

• Hepatopancreatic sphincter regulates release of bile into the duodenum

Gallbladder

57

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

Gallbladder

58

• The hormone CCK,

cholecystokinin,

causes the

gallbladder to

contract, in response

to fats entering the

duodenum. The bile

is then released into

the duodenum.

Regulation of Bile Release

59

Hormones of the Digestive Tract

60

10/24/2016

11

• 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

• Bile salts also enhance absorption of fatty acids and cholesterol by forming micelles

• They help absorb fat-soluble vitamins A, D, E and K

• Almost all bile salts are recycled

Functions of Bile Salts

61

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


62

17.8: Small Intestine

63

• The small intestine is a 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 chyme

• Absorbs products of digestion

• Transports the remaining residue to the large intestine

• Small intestine consists of 3 parts: Duodenum, jejunum, ileum

• 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)

• The jejunum and ileum are suspended by a double-layered fold of peritoneum called a mesentery, which transports blood & 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

Parts of the Small Intestine

64

Parts of the Small Intestine

65

Mesentery & Greater Omentum

66

10/24/2016

12

• 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, a lacteal (lymphatic capillary), 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

Structure of the Small Intestinal Wall

67

Structure of the Small Intestinal Wall

68

Intestinal Epithelium

69

Plicae circulares

70

• In addition to mucous-secreting goblet cells, there are many specialized mucus-secreting glands, Brunner’s glands, that secrete a thick, alkaline mucus in response to certain stimuli

• Intestinal glands secrete a watery fluid, that picks up digestion products, and transports them into villi; contains no 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

Secretions of the Small Intestine

71 72

10/24/2016

13

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

Regulation of Small Intestinal Secretions

73

• Villi increase the surface area for absorption• Small intestine is most important absorbing organ of alimentary canal• Small intestine absorption is so effective that very little absorbable material

reaches the organ’s distal endCarbohydrate 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

Absorption in the Small Intestine

74

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


75

Fat digestion and absorption:

• Fats are emulsified by bile salts

• Fats are digested mainly by enzymes from pancreas and small intestine

• Fats are 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)


76

Fat Absorption

77 78

10/24/2016

14

• 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

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

Movements of the Small Intestine

79

17.9: Large Intestine

80

Large intestine:• Named because diameter is greater than that of small intestine

• 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

Large intestine:

Consists of cecum, colon, rectum, and anal canal:

• Cecum:

- Pouch, forms beginning of large intestine

- Appendix is attached to cecum; contains lymphatic tissue

• Colon:

- Ascending, transverse, descending and sigmoid portions

• Rectum:

Extends from sigmoid colon to anal canal

• Anal canal:

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

- Internal and external anal sphincters guard anus

Parts of the Large Intestine

81

Parts of the Large Intestine

82

Structure of the Large Intestine

83

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

• Wall of large intestine lacks villi and plicae circulares

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

• Bands create pouches called haustra, which help form feces

Structure of the Large Intestinal Wall

84

10/24/2016

15

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, which break down contents such as cellulose,

and produce vitamins K, B12, thiamine

• Forms feces, and carries out defecation

Functions of the Large Intestine

85

• Movements of the large intestine are similar to those of the small intestine

• They are slower and less frequent than those of the small intestine

• Movements:

• Mixing movements

• Peristalsis: 2-3 times/day

• Peristaltic waves produce strong mass movements, which usually follow meals

• The defecation reflex relaxes the internal anal sphincter and then the external anal sphincter

Movements of the Large Intestine

86

• 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

Feces

87

Disorders of the Large IntestineDiverticulosis:Weakening of intestinal wall leads to protrusion of mucous membrane; forms outpouchings that can become inflamed and infected

Inflammatory bowel disease:Group of disorders, including:• Ulcerative colitis: affects mucosa & 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 US• Screening tests include fecal occult blood test and colonoscopy


88

17.10: Life-Span Changes

89

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

ch17 lecture - Mr. B's Science Pagemrbssciencepage.weebly.com/uploads/7/9/7/4/7974541/ch17_lectur… · Chapter 17 Lecture Outline See separate PowerPoint slides for all figures and

Documents