Download CHAPTER 17: DIGESTIVE SYSTEM

UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
LEARNING OUTCOMES:
17.1
17.2
17.3
Introduction
1.
Describe the general functions of the digestive system.
2.
Name the major organs of the digestive system.
General Characteristics of the Alimentary Canal
3.
Describe the structure of the wall of the alimentary canal.
4.
Explain how the contents of the alimentary canal are mixed and moved.
Mouth
5.
Describe the functions of the structures associated with the mouth.
6.
Describe how different types of teeth are adapted for different functions, and list
the parts of a tooth.
17.4 - 17.10. Salivary Glands – Large Intestine
7.
Locate each of the organs and glands; then describe the general function of each.
8.
Identify the function of each enzyme secreted by the digestive organs and glands.
9.
Describe how digestive secretions are regulated.
10.
Explain control of movement of material through the alimentary canal.
11.
Describe the mechanisms of swallowing, vomiting, and defecating.
12.
Explain how the products of digestion are absorbed.
17.11 Life-Span Changes
13.
Describe aging-related changes in the digestive system.
17-1
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
17.1
INTRODUCTION
A.
Definition:
Digestion
The process by which food substances are changed into forms that can be
absorbed through cell membranes.
B.
Digestive Processes:
1.
2.
3.
4.
5.
C.
Ingestion = taking food into the mouth.
Movement of Food = the passage of food along the gastrointestinal (GI)
tract.
Digestion = the breakdown of food by chemical and mechanical means.
Absorption = the passage of digested food from GI tract into bloodstream
(and lymph) for distribution to cells.
Defecation = the elimination of undigested material from GI tract.
Digestive Organs
See Fig 17.1, page 650.
1.
Two categories:
a.
Alimentary canal (GI Tract), which extends from mouth to anus.
o
Organs include: See Fig 17.2, page 651.
1.
2.
3.
4.
5.
6.
b.
mouth
pharynx
esophagus
stomach
small intestine
large intestine
Accessory organs release secretions into the alimentary canal that
help digest food:
o
Organs include:
1.
salivary glands
2.
liver
3.
gallbladder
4.
pancreas
17-2
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
17.2
GENERAL CHARACTERISTICS OF THE ALIMENTARY CANAL
A.
Structure of the Wall
There are Four Distinct Layers of the wall.
See Fig 17.3 and Table 17.1, page 652.
1.
Mucosa = innermost (surrounds lumen)
a.
b.
c.
d.
composed of epithelium + CT (areolar) and small amounts of
smooth muscle
Epithelium extends into lumen = villi (increases surface area).
contains many glands that secrete mucus (lubrication & protection
from harmful action of digestive enzymes)
functions:
o
o
o
2.
Submucosa = beneath mucosa
a.
b.
composed of areolar CT, blood vessels, lymph vessels, and nerves
functions:
o
o
3.
nourishment of mucosa
carrying absorbed nutrients away
Muscularis = two layers of muscle
a.
b.
c.
4.
protection
secretion
absorption (of nutrients)
circular muscle layer around submucosa
longitudinal layer around circular layer
function: movements of food through canal (mixing & peristalsis)
Serosa = outermost layer
a.
visceral peritoneum
b.
functions:
o
lubrication
o
free movement of canal in abdominal cavity
c.
Intestinal peritoneal extensions = mesentery.
o
suspend the length of the intestine within abdominal cavity
17-3
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
17.2
GENERAL CHARACTERISTICS OF THE ALIMENTARY CANAL
B.
Movements of the Tube
See Figure 17.4, page 653.
1.
Mixing: (mechanical digestion)
a.
b.
c.
2.
food + digestive juices + mucus
circular muscle layer
segmentation occurs in small intestine
Peristalsis:
a.
b.
c.
d.
accomplished by movements of longitudinal muscle layer
propelling action
As food passes, one section of tube relaxes (receptive relaxation),
opening next section and food moves on.
Sphincter Muscles play an important role in movements
throughout the GI tract also.
1.
2.
C.
Definition: Sphincter = a strong circular muscle which
prevents regurgitation of food.
Locations: between (regions) organs of digestive tract.
a.
esophagus and stomach
o gastroesophageal sphincter
b.
stomach and small intestine
o pyloric sphincter
c.
small and large intestine
o ileocecal valve
d.
large intestine to outside
o internal anal sphincter
o external anal sphincter
Innervation of the Tube
1.
Autonomic Nervous System
a.
Parasympathetic – activates digestion
b.
Sympathetic – slows digestion
2.
Post-ganglionic networks
a.
Submucosal plexus controls secretions.
b.
Myenteric plexus controls peristalsis.
17-4
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
17.3
MOUTH
A.
Introduction:
1.
2.
B.
The terms oral cavity and buccal cavity refer to the mouth.
The mouth is adapted to receive food and start mechanical and chemical
digestion by chewing and mixing food with saliva.
The mouth is surrounded by cheeks, lips, tongue and palate:
1.
Cheeks and Lips
a.
b.
c.
2.
Tongue
a.
b.
c.
d.
e.
3.
Cheeks form the lateral walls of mouth.
Lips surround the opening of mouth; important in monitoring food
temperature.
See Fig 17.5, page 653.
muscular (skeletal) organ on floor of mouth
important in mixing food (mechanical digestion) and swallowing
contains many bumps called papillae, which house taste buds
posterior root contains lymphatic tissue called the lingual tonsil
See Figure 17.6, page 654.
Palate = roof of mouth.
a.
b.
c.
d.
Anterior portion = hard palate.
Posterior portion = soft palate.
Median extension of soft palate = uvula.
tonsils:
1.
Palatine tonsils = masses of lymphatic tissue lateral to
palate.
*
Tonsillitis = inflammation of palatine tonsils. See
box on page 654.
2.
e.
D.
Pharyngeal tonsils = adenoids lymphatic tissue on
posterior pharynx
See Figure 17.5, page 653, and Fig 17.7, page 655.
composed of 2 chambers:
a.
b.
Oral cavity proper = chamber that extends from teeth/gums to
pharynx.
Vestibule = narrow space between teeth, cheeks and lips.
17-5
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
17.3
MOUTH
E.
Teeth:
1.
2.
3.
two sets of dentitions: See Fig 17.8, page 655, and Fig 17.9 and
Table 17.2, page 656.
a.
deciduous teeth
1. number 20
2. erupt from 6 - 32 months
3. lost between 6 - 12 years
b.
permanent (secondary) teeth
1.
number 32
2.
erupt from 6 yrs - adulthood
3.
See Fig 17.9, page 656.
function: to break food into smaller pieces. (mechanical digestion)
a.
increasing surface area of food
b.
increasing effectiveness of digestive enzymes
4 types with different functions:
See Fig 17.9, page 656.
a.
Incisors = front teeth.

break food into bite-size pieces
b.
Cuspids = canine (eye) teeth.

grasps and tears food
c.
Bicuspids = grinding food particles.
d.
Molars = grinding food particles.
See box on page 658 re: stem cells and replacement teeth.
4.
Tooth Structure:
Teeth are located in alveolar processes of maxilla and mandible. See Fig
17.10, page 656.
a.
b.
c.
d.
Crown = exposed area of tooth.
Root = area below gum (gingiva).
Enamel =covering on crown Ca2+ salts hardest substance in body.
Dentin = bulk of tooth.
*
See Clinical Application 17.1, page 657 re: Dental Caries.
*
See Table 17.3, page 657, Parts of the Mouth.
17-6
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
17.4
SALIVARY GLANDS
A.
B.
Introduction:
1.
Salivary glands secrete saliva.
2.
Saliva binds food together and begins chemical
polysaccharides by the enzyme salivary amylase.
digestion
of
Major Salivary Glands
1.
parotid = largest lies over masseter, mostly serous cells
2.
submandibular = floor of mouth lateral, mix of serous and mucous cells
3.
sublingual = floor of mouth, medial, mostly mucous cells
See Figure 17.11, page 659 and Table 17.4, page 658.
C.
Salivary Secretion Composition:
1.
Each salivary gland is composed of 2 types of cells:
a.
Mucous cells secrete mucus
b.
Serous cells secrete watery substance containing the enzyme
salivary amylase.
See Fig 17.12, page 659.
D.
Salivary Secretion Functions:
1.
provide lubrication
2.
bind food together
3.
begin chemical digestion of carbohydrates
Enzyme = salivary amylase breaks polysaccharides into disaccharides.
a.
b.
starch  disaccharides
glycogen  disaccharides
17-7
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
17.5
PHARYNX AND ESOPHAGUS
A.
PHARYNX
1.
2.
3.
throat
passageway of food into esophagus (and air into larynx/trachea)
Structure of the Pharynx: See Fig 17.7, page 655.
nasopharynx – superior to soft palate, posterior to nasal cavity
oropharynx – posterior to mouth down to epiglottis
laryngopharynx – inferior to oropharynx from epiglottis to cricoid
cartilage
Muscles of the Pharynx Wall:
See Fig 17.13, page 640.
Swallowing Mechanism (deglutition): 3 stages
See Figure 17.14, page 661.
A.
B.
C.
4.
5.
a.
Stage 1 (voluntary): Chew food & mix with saliva into bolus at
back of pharynx.
b.
Stage 2 (involuntary): Swallowing reflex triggered,
c.
B.
o
Epiglottis closes over larynx (no breathing).
o
Muscles in lower pharynx relax.
o
Esophagus opens and food moves in.
Stage 3 (involuntary) Esophagus brings bolus to stomach by
peristalsis.
ESOPHAGUS
See Fig 17.15 and Fig 17.16, page 662.
1.
passageway for food from pharynx to stomach
2.
Location: mediastinum behind trachea goes through diaphragm at
esophageal hiatus
a.
See box on page 662 re: Hiatal hernia.
3.
many mucous glands
4.
Movement of food:
A.
gravity
b.
Peristaltic waves from esophagus meet
sphincter muscle (cardiac sphincter).
c.
Gastro esophageal sphincter muscle relaxes.
d.
Food moves into stomach all at once.
gastroesophageal
17-8
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
17.6
STOMACH: See Fig 17.18, page 663.
A.
B.
Introduction:
1.
The term gastric refers to the stomach.
2.
The stomach functions to mix bolus into chyme and begin the chemical
breakdown of proteins.
Structure of Stomach:
1.
Description = J-shaped, pouch-like organ.
2.
contains extra oblique layer in muscularis
3.
Location = under diaphragm left side.
4.
Capacity = 1 liter.
5.
Parts of the Stomach:
a.
b.
c.
d.
6.
cardiac region - around esophagus
fundic region - large ballooned area
body – main portion
pyloric region - near duodenum
o
The pyloric region narrows into pyloric canal.
o
The pyloric sphincter muscle lies between pylorus &
duodenum.
d.
greater curvature
e.
lesser curvature
f.
body
Mucosal Structure
a.
Note the macroscopic rugae (mucosal folds) in Fig 17.17b, page
663.
b.
Microscopically, these rugae are formed by:
See Fig 17.19, page 664.
o
Gastric villi that project into the lumen which result in the
formation of…
o
Gastric pits that are located between the gastric villi.
1.
Gastric glands are located along these gastric pits.
a.
C.
Gastric juice is secreted by these gastric
glands.
Functions of Stomach:
1.
mechanical digestion – churning
2.
chemical digestion of proteins – gastric juice
17-9
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
17.6
STOMACH
D.
Gastric Secretions (Juice): See Table 17.5, page 665.
1.
composed of:
a.
mucus
○
Function: lubrication, protection of mucosa from digestion
b.
digestive enzyme pepsin
○
Function: protein digestion (into peptides)
c.
hydrochloric acid (HCl)
○
Functions:
1.
denatures proteins
2.
kills microbes in food
d.
intrinsic factor
○
Function: aids absorption of Vitamin B12 needed for
erythropoiesis
e.
gastrin
Function: regulatory hormone
2.
Four types of gastric cells in Gastric Glands:
a.
b.
c.
d.
E.
Mucous cells secrete mucus.
Chief cells secrete pepsin.
Parietal cells secrete HCl & intrinsic factor.
G-cells secrete gastrin.
Regulation of Gastric Secretions: See Fig 17.20, page 665 and
Table 17.6, page 666.
1.
Neural
a.
parasympathetic – increases gastric secretion
b.
sympathetic – decreases gastric secretion
2.
Hormonal
a.
Gastrin – increases gastric secretion
b.
Somatostatin – decrease acid secretion from parietal cells
c.
Cholecystokinin – decreases gastric motility
17-10
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
17.6
STOMACH
E.
Regulation of Gastric Secretions:
3.
Three phases of Gastric Secretion
a.
Cephalic Phase (30-50% of control)
○
increased parasympathetic due to sight, taste, smell, and
thought of food
b.
Gastric Phase (40-50% of control)
○
Stretch of stomach wall increases gastrin secretion, which
increases gastric secretions.
○
pH changes alter gastrin release.

Food enters stomach, increasing pH.

The reflexive increase in gastrin lowers pH.

When pH lowers to 1.5 gastrin release
ceases.
○
HCl released from parietal cells comes from blood.

Blood pH needs to maintain 7.4.

Parietal cells release bicarbonate to blood.

This is called the alkaline tide.
c.
Intestinal Phase (5% of control)
○
Initially releases intestinal gastrin which increases gastric
secretions.
○
As duodenum fills, a sympathetic reflex inhibits gastric
release.
○
Proteins and fats in duodenum stimulate cholecystokinin
release which decreases gastric motility.
F.
Gastric Absorption = Minimal (5%); includes some salts, water, lipid-soluble
drugs, and alcohol
G.
Mixing and Emptying Actions
See Fig 17.21, page 667, and Fig 17.22, page 668.
1.
Mixing of bolus of food + gastric juice = chyme.
2.
Peristaltic waves of stomach push chyme toward pyloric sphincter; it
relaxes and food moves into duodenum a little at a time!!!
○
See box on page 664 re: hypertrophic pyloric stenosis.
3.
Enterogastric reflex – ensures stomach slows down as duodenum fills.
4.
Vomiting may occur to quickly remove toxins.
*
*
See Clinical Application 7.2, A Common Problem: Stomachache, page 667.
See box on page 665 re: Helicobacter pylori and gastritis and peptic ulcers.
17-11
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
17.7
PANCREAS
A.
Location:
B.
Inferior to stomach; retroperitoneal
See Fig 17.23, page 669.
Structure of the Pancreas
1.
Shrimp–like with head in concave curve of duodenum; Tail extends to the
left to the spleen.
2.
Endocrine cells (alpha and beta cells of Islets of Langerhans) produce
hormones glucagon and insulin, respectively. See Chapter 13.
3.
Most cells make up pancreatic acini, which produce pancreatic juice.
a.
4.
C.
Secretes pancreatic juice into a pancreatic duct; Pancreatic duct
leads to duodenum (small intestine).
Pancreatic duct joins bile duct at the Hepatopancreatic ampulla (ampulla
of Vater) before passing through the Hepatopancreatic sphincter
(sphincter of Oddi) to enter duodenum.
Pancreatic Juice:
Pancreatic juice contains four classes of enzymes that break down the four
ingested organic macromolecules.
1.
Carbohydrates (Starch and Glycogen)
a.
2.
Fats/Triglycerides
a.
3.
*
Proteinases, trypsin, chymotrypsin, and carboxypeptidase
proteins → peptides
o
These enzymes are stored and released as inactive form in
zymogen granules.
o
Trypsinogen is activated to trypsin by enterokinase.
o
Trypsin then activates chymotrypsin and carboxypeptidase.
Nucleic Acids
a.
*
pancreatic lipase → 2 fatty acids + monoglyceride
Proteins
a.
4.
pancreatic amylase → disaccharides
nucleases
nucleotides
Note bicarbonate ions are also released to neutralize acidic chyme entering
from the stomach.
See box on page 668 re: acute pancreatitis.
17-12
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
17.7
PANCREAS
D.
Regulation of Pancreatic Secretions: See Fig 17.24, page 670.
1.
2.
Hormones secretin and cholecystokinin regulate pancreatic secretions.
Secretin Activation:
a.
b.
c.
3.
Cholecystokinin Activation:
a.
b.
c.
17.8
When duodenum fills with acidic chyme,
secretin is released from the intestinal wall.
Secretin stimulates the release of bicarbonate rich pancreatic
juice into duodenum.
Once acid is neutralized,
proteins and fats signal cholecystokinin release from the intestinal
wall.
CCK stimulates the release of enzyme rich pancreatic juice into
the duodenum.
LIVER
A.
Introduction: The term hepatic refers to the liver. The liver has many
functions; however its digestive function is emulsification of fats.
B.
Location/Description:
See Fig 17.25, page 670 and Fig 17.26, page 671.
1.
below diaphragm
2.
right side
3.
largest internal organ
C.
Liver Structure:
1.
4 lobes:
a.
b.
c.
Fig 17.26, page 671.
large right & small left
quadrate and caudate lobe in posterior region
each lobe is made up of:
o
Hepatic lobules = functional unit of the liver.
See Fig 17.27, page 671.
1.
hexagon shaped around a central vein
2.
contains hepatocytes which provide most functions
3.
also contains Kupffer’s cells (macrophages)
See Fig 17.28, page 672.
a.
remove and destroy:

microbes

foreign matter

worn platelets and erythrocytes
17-13
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
17.8
LIVER
D.
E.
Liver Functions:
1.
2.
3.
4.
5.
metabolism of monosaccharides, lipoproteins, and amino acids
storage (glycogen, Vitamin A, B12, D, iron)
filtering of blood (worn blood cells and debris)
destruction of toxic chemicals (alcohol and drugs)
production/secretion of bile
*
See Table 17.7, page 673 for more specifics on liver functions.
Blood Supply to Liver: See Figure 17.28, page 672.
1.
2.
3.
from 2 sources:
a.
hepatic artery supplies oxygenated blood
b.
hepatic portal vein supplies deoxygenated blood filled with:
○
newly absorbed nutrients from small intestine
○
toxins from stomach
○
worn blood cells from spleen
Blood enters the liver sinusoids where hepatocytes remove the following:
a.
oxygen
b.
nutrients (stored or used to make new materials)
c.
poisons (detoxified)
d.
worn cells and debris (phagocytosis).
Blood leaving the liver cells (deoxygenated plus liver secretions) drains
into central veins, which come together and leave the liver as the hepatic
vein.
17-14
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
17.8
LIVER
E.
Blood Supply to Liver: See Figure 17.28, page 672.
4.
Overall scheme of Liver Blood Flow:
Hepatic Artery
(Oxygenated Blood)
from aorta)
Hepatic Portal Vein
(Deoxygenated Blood with
newly absorbed nutrients
from small intestine, etc.)
Liver Sinusoids
(Exchange)
Central Vein of Hepatic Lobule
Hepatic Vein
Inferior Vena Cava
F.
Composition of Bile
Bile is composed of:
1.
2.
3.
4.
bile salts (digestive function)
bile pigments (biliverdin and bilirubin)
a.
breakdown products of hemoglobin
cholesterol
electrolytes
*
See box on page 672 re: hepatic coma.
*
See from Science to Technology 17.1, page 673, Replacing the Liver.
*
See Clinical Application 17.3, page 674, Hepatitis.
*
See box on page 673 re: jaundice.
17-15
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
17.8
LIVER
G.
Gall Bladder
See Fig 17.26, page 671, and Fig 17.29, page 674.
1.
stores bile between meals
2.
Location:
3.
Bile can flow to small intestine by either of 2 routes:
the liver or gall bladder (see below)
4.
Bile secretion, storage, flow:
underside of liver, connected via cystic duct
From liver:
From Gall Bladder:
Common Hepatic duct
Cystic Duct
COMMON *
BILE DUCT
Duodenum
*
*
5.
Hepatopancreatic sphincter muscle usually keeps common bile
duct closed.
See Clinical Application 17.4, page 675, Gallbladder Disease.
Regulation of Bile Release
See Fig 17.30, page 675.
a.
Hormone = CHOLECYSTOKININ (CCK)
b.
When small intestine fills with fatty chyme:
o
o
o
o
c.
cholecystokinin is released into blood.
CCK stimulates walls of gallbladder to contract.
Bile passes down into cystic duct and common bile duct.
Hepatopancreatic sphincter in common bile duct opens and
bile is deposited into duodenum.
Functions of Bile Salts:
Emulsification of fat molecules!
o
Emulsification = breaking up of fat globules into small
droplets (increases surface area and increases effectiveness
of lipases).
o
Bile is released into duodenum to emulsify fat.
o
Bile also aids in absorption of fats and fat-soluble vitamins.
17-16
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
17.9
SMALL INTESTINE
A.
Parts of Small Intestine:
1.
2.
3.
duodenum - nearest stomach
jejunum - mid-region
ileum - near large intestine.
a.
b.
c.
B.
C.
See Fig 17.31, page 676.
The distal end of the ileum narrows to form the ileocecal valve
(sphincter muscle between small & large intestine).
Jejunum and ilium are attached to the posterior abdominal wall by
folds in peritoneum called mesentery.
See Figure 17.33, page 677.
Functions of Small Intestine
1.
Major site of chemical digestion (duodenum)
a.
bile deposition
b.
pancreatic juice deposition
c.
small intestinal digestive enzymes
2.
Secretions
a.
mucus
b.
digestive enzymes
3.
Major site of ABSORPTION of Nutrients
a.
about 90% of all
b.
through the proximal mucosa
Structure of the Small Intestine Wall
See Fig 17.35 and Fig 17.36, page 678.
1.
Intestinal villi project into lumen (increasing surface area).
2.
Each villus is composed of simple columnar epithelium, with microvilli
(further increasing surface area; See Figure 17.37, page 679) and
connective tissue with many blood & lymphatic vessels (lacteals).
3.
Absorbed nutrients are carried away by blood & lacteals.
4.
Intestinal glands are located between villi and further increase surface
area (SA).
5.
Submucosal folds called plicae circulares also further increase SA; See
Figure 17.38, page 679.
6.
*
Muscularis and serosa are typical.
See box on page 678 re: small intestine muscosal turnover.
17-17
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
17.9
SMALL INTESTINE
D.
Secretions of Small Intestine
1.
2.
mucus (from Brunner’s glands in submucosa and goblet cells)
digestive enzymes:
a. peptidases
peptides
amino acids
b. sucrase, maltase, lactase
disaccharides
monosaccharides
*
See box on page 680 re: lactose intolerance.
c. intestinal lipases
triglycerides
*
3 fatty acids + glycerol
See Table 17.9, page 680 for Summary of Major Digestive Enzymes.
E.
Regulation of Small Intestinal Secretions
1.
Mechanical and chemical stimulation of duodenal wall by entering chyme
regulates intestinal secretions.
F.
Absorption in Small Intestine (90% of total) Fig 17.42, page 682.
1.
Intestinal villi and microvilli (See Fig 17.37, page 679) increase absorptive
surface area.
2.
Simplest forms of ingested food molecules are absorbed into the intestinal
mucosa:
a. monosaccharides
1.
by facilitated diffusion or active transport
2.
carried away by submucosal blood capillaries
b. amino acids
1.
active transport
2.
carried away by blood capillaries
c. fatty acids
1.
by simple diffusion into intestinal mucosa
2.
Fatty acids are used to synthesize endoplasmic
reticulum “ER”.
2.
Once in mucosal cells’ ER, the fats collect in
clusters encased in protein to form chylomicrons
(lipoproteins).
3.
Chylomicrons are absorbed by lacteals (lymphatic
capillaries) into the lymphatic system.
d. Ions and water are also absorbed.
*
See box on page 682 re: Malabsorption.
17-18
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
17.9
SMALL INTESTINE
G.
Movements of the Small Intestine
1.
mixing of chyme + intestinal juices by segmentation (mechanical
digestion)
2.
Peristaltic waves push residual chyme toward ileocecal sphincter; It
relaxes, moving food into large intestine.
*
Irritation or over distension may cause peristaltic rush which is
rapid emptying of small intestine resulting in diarrhea.
17.10 LARGE INTESTINE
A.
Parts of Large Intestine: See Fig 17.43, page 684.
1.
2.
3.
4.
B.
Colon is divided into four (4) portions:
1.
2.
3.
4.
C.
ascending colon - from cecum to liver (right)
transverse colon - runs across top of abdomen
descending colon - from spleen downward (left)
sigmoid colon - S-shaped portion, which becomes rectum
Structure of the Large Intestinal Wall
1.
2.
3.
4.
5.
D.
cecum - nearest ileum of small intestine; Appendix is a blind pouch in this
region.
*
See box on page 683 re: appendicitis.
colon - majority of length
rectum - distal region of colon
*
See box on page 683 re: hemorrhoids.
anal canal - narrowing of rectum and opening to outside
relatively same as typical wall; See page 652.
lacks villi
Longitudinal muscularis layer forms 3 bands called teniae coli.
Pouches or haustra develop due to the tension of the teniae coli.
Serosa may have fatty extensions called epiploic appendages.
Functions of Large Intestine:
1.
2.
3.
4.
Secretion = mucus.
Absorption = water & electrolytes.
Storage = feces.
Minimal digestion by intestinal flora (bacteria) which digest substances
humans cannot digest.
17-19
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
17.10 LARGE INTESTINE
E.
Movements of the Large Intestine:
1.
mass movements only 2-3 times a day
a.
F.
Control of Anal Sphincter Muscles:
1.
G.
Peristaltic waves of large intestine move residual chyme toward
anal sphincter muscles.
both voluntary & involuntary nervous control
Feces:
1.
undigested & unabsorbed material
2.
color due to bile pigments
3.
odor due to intestinal bacteria and bacterial products formed in digestion
4.
75% water
*
See box on page 686 explaining sources of intestinal gas.
H.
Defecation = emptying of rectum.
*
See box on page 686 re: Hirschsprung Disease.
*
See Clinical Application 17.5 page 687, Disorders of the Large Intestine.
17-20
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
DIGESTIVE SYSTEM SUMMARY TABLE I (keyed at the end of this outline)
NAME OF
DIGESTIVE
ORGAN
ALIMENTARY
CANAL OR
ACCESSORY?
DESCRIPTION OF
STRUCTURE
SECRETIONS
DIGESTIVE
FUNCTION
HORMONAL
CONTROL OF
SECRETIONS?
17-21
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
DIGESTIVE SYSTEM SUMMARY TABLE I (CONTINUED)
NAME OF
DIGESTIVE
ORGAN
ALIMENTARY
CANAL OR
ACCESSORY?
DESCRIPTION OF
STRUCTURE
SECRETIONS
DIGESTIVE
FUNCTION
HORMONAL
CONTROL OF
SECRETIONS?
17-22
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
DIGESTIVE SYSTEM SUMMARY TABLE I (CONTINUED)
NAME OF
DIGESTIVE
ORGAN
ALIMENTARY
CANAL OR
ACCESSORY?
DESCRIPTION OF
STRUCTURE
SECRETIONS
DIGESTIVE
FUNCTION
HORMONAL
CONTROL OF
SECRETIONS?
17-23
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
DIGESTIVE SYSTEM SUMMARY TABLE I (CONTINUED)
NAME OF
DIGESTIVE
ORGAN
ALIMENTARY
CANAL OR
ACCESSORY?
DESCRIPTION OF
STRUCTURE
SECRETIONS
DIGESTIVE
FUNCTION
HORMONAL
CONTROL OF
SECRETIONS?
17-24
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
DIGESTIVE SYSTEM SUMMARY TABLE II (Keyed at the end of this outline)
MACROMOLECULE
INGESTED
SITE OF
DIGESTION
DIGESTIVE
ENZYME(S)
ENDPRODUCT(S)
SITE AND
MODE OF
ABSORPTION
ABSORBED
INTO BLOOD
OR LYMPH
REGULATION
17-25
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
17.11 LIFE SPAN CHANGES
A.
Mouth changes that occur with age reduce chewing ability.
1.
Enamel thins increasing sensitivity to hot and cold.
2.
Gums recede.
3.
Teeth loosen.
B.
Slowing peristalsis causes:
1.
heartburn
2.
constipation
C.
Absorption of nutrients decreases with age.
OTHER INTERESTING TOPICS:
A.
B.
C.
The Gut Microbiome. See Introduction on page 649.
GI Camera. See box on page 651.
Cheek cells used to provide DNA for genetic testing. See box on page 654.
INNERCONNECTIONS OF THE DIGESTIVE SYSTEM - See page 689.
CHAPTER SUMMARY – see pages 688, 690-692.
CHAPTER ASSESSMENTS – see pages 692-693.
INTEGRATIVE ASSESSMENTS/ CRITICAL THINKING – see page 693.
17-26
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
DIGESTIVE SYSTEM SUMMARY TABLE I:
NAME OF
DIGESTIVE
ORGAN
MOUTH
SALIVARY
GLANDS
PHARYNX
ALIMENTARY
CANAL OR
ACCESSORY?
ALIMENTARY
CANAL
ACCESSORY
ALIMENTARY
CANAL
DESCRIPTION OF
STRUCTURE
SEE OUTLINE
SEE OUTLINE
SEE OUTLINE
SECRETIONS
MUCUS
SALIVA WITH
AMYLASE
MUCUS
DIGESTIVE
FUNCTION
MECHANICAL
BREAKDOWN OF
STARCH AND
GLYCOGEN TO
DISACCHARIDES
NONE
HORMONAL
CONTROL OF
SECRETIONS?
N/A
N/A
N/A
17-27
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
DIGESTIVE SYSTEM SUMMARY TABLE I:
NAME OF
DIGESTIVE
ORGAN
ESOPHAGUS
STOMACH
(GASTRIC)
LIVER
ALIMENTARY
CANAL OR
ACCESSORY?
ALIMENTARY
CANAL
ALIMENTARY
CANAL
ACCESSORY
DESCRIPTION OF
STRUCTURE
SEE OUTLINE
SEE OUTLINE
SEE OUTLINE
MUCUS
PEPSIN
SECRETIONS
MUCUS
HYDROCHLORIC
ACID
BILE
INTRINSIC
FACTOR
GASTRIN
DIGESTIVE
FUNCTION
NONE
PEPSIN BREAKS
PROTEINS INTO
PEPTIDES
EMULSIFICATION OF FATS
HCl DENATURES
THE PROTEINS
HORMONAL
CONTROL OF
SECRETIONS?
N/A
GASTRIN
SECRETED BY GCELLS
PROMOTES
RELEASE OF
GASTRIC JUICE,
ETC.
CHOLECYTOKININ (CCK)
OPENS COMMON
BILE DUCT
WHEN FATTY
CHYME FILLS
DUODENUM
17-28
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
DIGESTIVE SYSTEM SUMMARY TABLE I:
NAME OF
DIGESTIVE
ORGAN
GALL BLADDER
PANCREAS
SMALL
INTESTINE
ALIMENTARY
CANAL OR
ACCESSORY?
ACCESSORY
ACCESSORY
ALIMENTARY
CANAL
DESCRIPTION OF
STRUCTURE
SEE OUTLINE
SEE OUTLINE
SEE OUTLINE
AMYLASE
PEPTIDASES
PROTEASES
(PROTEINASES)
SUCRASE,
MALTASE,
LACTASE
SECRETIONS
STORED BILE
PRODUCED IN
LIVER
LIPASES
NUCLEASES
DIGESTIVE
FUNCTION
HORMONAL
CONTROL OF
SECRETIONS?
EMULSIFICATION OF FATS
CCK CAUSES
CONRTACTION OF
GALLBALLDER AND
OPENS COMMON
BILE DUCT WHEN
FATTY CHYME
FILLS DUODENUM
LIPASES
AMYLASE:
STARCH AND
GLYCOGEN TO
DISACCHS.
PROTEASES:
PROTEINS TO
PEPTIDES.
LIPASES:
TRIGLYCERIDES
TO FATTY ACIDS
& MONOGLYCERIDES.
NUCLEASES:
NUCLEIC ACIDS
TO
NUCLEOTIDES.
PEPTIDASES:
PEPTIDES TO
AMINO ACIDS.
SUCRASE,
MALTASE,
LACTASE:
DISACCHARIDES
TO MONOSACCHARIDES.
LIPASES: TG TO
FATTY ACIDS
AND GLYCEROL.
SECRETIN
CAUSES
PANCREATIC
JUICE TO BE
DEPOSITED INTO
DUODENUM
N/A
17-29
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
DIGESTIVE SYSTEM SUMMARY TABLE I
NAME OF
DIGESTIVE
ORGAN
LARGE
INTESTINE
ALIMENTARY
CANAL OR
ACCESSORY?
ALIMENTARY
CANAL
DESCRIPTION OF
STRUCTURE
SEE OUTLINE
SECRETIONS
MUCUS
DIGESTIVE
FUNCTION
REABSORPTION
OF WATER AND
ELECTROLYTES
FROM CHYME
HORMONAL
CONTROL OF
SECRETIONS?
N/A
17-30
UNIT 5 - CHAPTER 17: DIGESTIVE SYSTEM
DIGESTIVE SYSTEM SUMMARY TABLE II
MACROMOLECULE
INGESTED
CARBOHYDRATES
PROTEINS
FATS (TRIGLYCERIDES
OR TG)
NUCLEIC
ACIDS
SITE OF
DIGESTION
1.MOUTH
2.DUODENUM
3.DUODENUM
1.STOMACH
2.DUODENUM
3.DUODENUM
1. DUODENUM
2. DUODENUM
DUODENUM
DIGESTIVE
ENZYME(S)
1. SALIVARY
AMYLASE
2. PANC.
AMYLASE
3. SUCRASE,
LACTASE,
MALTASE
1.PEPSIN
*HCl
2.
PANCREATIC
PROTEASES
3.
PEPTIDASES
1.
PANCREATIC
LIPASES
*BILE
2. DUODENAL
LIPASES *BILE
PANCREATIC
NUCLEASES
END-PRODUCT
(S)
1 & 2.
STARCH AND
GLYCOGEN
TO DISACCHARIDES
HCl
DENATURES
PROTEINS
1 & 2.
PROTEINS TO
PEPTIDES
3. PEPTIDES
TO AMINO
ACIDS
BILE
EMULSIFIES
TG’S.
PANCREATIC
LIPASES
BREAK TG’S
INTO FATTY
ACIDS &
MONOGLYCERIDES;
DUODENAL
LIPASES
BREAK TG’S
INTO FATTY
ACIDS &
GLYCEROL
NUCLEOTIDES
3. DISACCHARIDES TO
MONOSACCHARIDES
SITE AND MODE
OF ABSORP-TION
DISTAL SM.
INTESTINE
FACILITATED
DIFFUSION
DISTAL SM.
INTESTINE
ACTIVE
TRANSPORT
DISTAL SM.
INTESTINE
SIMPLE
DIFFUSION
DISTAL SM.
INTESTINE
ABSORBED INTO
BLOOD OR
LYMPH
BLOOD
BLOOD
LYMPH BY
LACTEAL
BLOOD
REGULATION
SECRETIN
FOR PANC.
AMYLASE
GASTRIN
FOR PEPSIN
CCK FOR BILE
SECRETIN FOR
PANC. LIPASES
SECRETIN
FOR PANC.
NUCLEASES
17-31