Transcript The Digestive System

The Digestive System
Chapter
16
Introduction to the
Digestive System:
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Also known as the gastrointestinal tract
(GIT) or gut.
Consists of a long tubular system
(alimentary canal). The size and shape
changes along the way.
Lined by a thin epithelium
Tubular structures include: the oral
cavity, pharynx, esophagus, stomach,
S.intestine and L. intestine
Histology of the tubular
digestive system:
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4 major layers or tunics (from the inside
out):
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Mucosa: (innermost) mucous membrane
attached to thin visceral muscle
Submucosa: loose connective tissue
binds the mucosa to muscularis
Muscularis: skeletal and smooth muscle
Serosa (outermost): connective &
epithelial tissue. Also known as visceral
peritoneum (covers & binds organs to
one another) extends to mesentery.
Introduction to the
Digestive System:
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Accessory structures are also
included in this system:
Teeth
 Tongue
 Salivary glands
 Liver
 Gallbladder
 Pancreas
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Terms used to refer to
different organs:
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Oral: mouth
Gastric: stomach
Enteric: small intestine
Colonic: large intestine
Hepatic: liver
Used to describe diseases ( e.g.
gastroenteritis = vomiting & diarrhea
involving stomach & intestines)
Function of the Digestive
System:
Ingestion and peristalsis: Take in
food & water and move it along
 Digestion: breakdown the food into
smaller pieces
 Absorption: uptake of the small
molecules resulting from digestion
from the epithelial cells to blood or
lymph
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Function of the Digestive
System:
Provide nutrients: process of
digestion & absorption provides
water , electrolytes, vitamins,
minerals ( esp. Ca, Fe, Ph)
 Defecation: eliminate wastes,
indigestible (fiber) that cannot be
absorbed are excreted in the feces.
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Oral cavity (buccal):
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Involved in mastication (chewing process)
Lips and cheeks : keep food between
upper and lower teeth, assist in speech
Hard palate: anterior part of roof of the
mouth
Soft palate: posterior part
Lips: orbicularis oris, covered internally
by mucosa & externally by stratified,
squamous epithelium (thin, red peeks
through)
Oral cavity (buccal):
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Cheeks: form lateral walls, buccinator
muscle
Tongue: covered in bumps or papillae
(friction & taste buds) -attachment to
floor of mouth by the frenulum:
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Attached & supported by hyoid bone
Moves food in mouth-collects into BOLUS
Holds food in place
Aids in swallowing
Sensory (taste)
speech
Oral cavity (buccal):
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Uvula: Made of muscle & connective
tissue covered in mucus membrane
Latin word for “grape”
 Last step in fusion of soft palate
 Can be divided like an upside down “Y”
 Aids in swallowing & speech (gutteral
sounds)
 Prevents food from backing up into
nasal area
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Teeth:
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Dentes collectively called “dentition”
20 deciduous teeth in childhood (start at
6 mo. – 30 mo.)
32 “permanent” in the mandible & maxilla
(6 – 25 years)
Divided into quadrants:
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R upper
L upper
R lower
L lower
Each quadrant:
One central incisor
 One lateral incisor
 One canine
 1st premolar
 2nd premolar
 2 molars
 3rd molar is “wisdom” tooth
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Teeth:
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4 types
Incisors (front): biting
 Cuspids or Canines (behind incisors):
tearing
 Bicuspids or premolars ( behind
cuspids): crushing
 Molars: (behind bicuspids): crushing
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Deciduous
>>>
Permanent
<<<<
Tooth anatomy:
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Crown: above gumline
Neck: constriction between crown & root
Root: below gumline (anchor) 1-3
projections into alveolar bone
Enamel: hard, protective outer covering
of the crown (protects from acids & wear)
Dentin: firm, main structure of the tooth
Pulp: arteries, veins and nerves of tooth
Tooth anatomy:
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Apical foramen: where the blood vessels
& nerves enter the tooth to become part
of the pulp
Cementum: covers the dentin which
attaches the root to the periodontal
ligament.
Joint between tooth & bone = gomphosis
Gingiva (gum) covers bone
Gingiva sulcus : space between gum &
tooth (flossing!)
Salivary glands:
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Located outside the oral cavity but have
ducts (tubes) leading into cavity.
2 pairs under jaw- submandibular and
sublingual (below tongue)
1 pair on side of face near ears- Parotid
(serous gland)
Mumps: viral inflammation of Parotid, if
testicles become inflamed, sterility could
occur. MMR vaccine protects.
Saliva:
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1 ½ Qts of saliva/day
>99% water
Moistens food –makes it easier to break
up and swallow
Serous secretion is watery (parotid)
increases with parasympathetic
stimulation
Sympathetic stimulation results in
decrease of volume and increased mucus
( thick & sticky)
Swallowing:
Considered a REFLEX – automatic,
preprogrammed response to a
stimulus
 Assists in the movement of the food
materials into the stomach
 Peristaltic contractions move the
material down the esophagus to the
stomach.
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Esophagus:
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A tube which leads from the pharynx to
the stomach
Contains glands which produce mucus for
lubrication of the passage
Passes through a small hole in the
diaphragm – usually fits tightly (if too
large, a hiatal hernia may result
Peristalsis – movement of materials into
the esophagus from the stomach
“heartburn” (section posterior to heart)
The Stomach:
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A bag-like structure which attaches to the
esophagus at one end and the small
intestine at the other.
To be sure food moves in the right
direction, numerous sphinters are
present:
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gastroesophogeal/cardiac sphincter:
junction between stomach and
esophagus
Pyloric sphincter: junction between the
stomach and the small intestine
The Stomach:
Inside, large folds (rugae) are
present – allow stretching without
damaging the wall of the organ.
 Fundus : expanding storage area
 Body : storage /digestion area
 Pylorus : digestion/dispensing area
 Muscularis – longitudinal, circular &
oblique (churning)
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Glands & cells of the
Stomach:
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Gastric submucosal glands and the lining
epithelium produce large amounts of
mucus which creates protection on inner
surface (prevents damage from HCl/enz)
Chief (peptic) cells: pepsinogen converted
to pepsin when activated HCl is there (pH
must be right) – breaks down protein.
Pariietal cells: produces intrinsic factor
which is necessary for the absorption of
Vit. B12 ( RBC production) and DNA
(low pH for pepsin and breakdown of food
within the chyme)
Lack of B12 can result in Pernicious anemia –
note size compared to the lymphocyte
Absorption and ulcers:
Very little absorption in the stomach
(mucus layer interferes)
 Materials must be both fat & water
soluble to be absorbed:
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Aspirin & ethyl alcohol
 Ulcers: erosions of the mucosal lining
exposing the underlying layers to HCl
and enzymes – duodenum common
 MANY DUE TO Helicobactor pylori
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Small Intestine: 21’ long!
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Composed of 3 sections:
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Duodenum : attached to stomach (10”)
Jejunum : middle
Ileum :attached to colon
Microscopic anatomy: increases digestive
and absorptive surface area
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Plica circularis – small ridges/folds of the
inner lining
Villi – finger-like projections which
extend out of the mucosal surface (blood
capillaries and lacteals) looks like shag
carpet.
Small Intestine:
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Microvilli –folds of the mucosal epithelial
• Contains some membrane-bound enzymes and
are the sites of nutrient absorption
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Enteric lining is replaced every 5 days –
this keeps microbes from clinging
Intestinal motility: 3-5 hours
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Segmentation – contraction of circular
layer of muscles – mixing motion
(contact with enzymes & mucosa)
Peristalsis – moves chyme longitudinally
down to next segment or into colon
Note mesentary (cat)
See the lymphatic system?
Large Intestine: Consists of
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Transverse colon-across abdomen
Ascending colon-right side of abdomen
Descending colon- left side of abdomen
Cecum -pouch
Ileocecal valve- between ileum & cecum
Appendix - closed end of cecum
Sigmoid colon- last part of colon, joins
Rectum
Anal spincter
5 feet in length & ave. 2 ½ in. in diameter
Microscopic anatomy of the
Large Intestine:
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Taenia coli: 3 bands of smooth muscle
derived from the longitudinal layer of the
muscularis
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Leaves colonic wall thin
“gathers” up the colon
Haustra: wrinkles/pouches which form as
a result of the contraction of the taenia
coli
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Increases surface area for absorption,
primarily WATER
Functions of the colon:
Reabsorption of water from the
chyme
 Some vitamin(Vit B & K) and
mineral ( esp. NaCl) absorption
 Bacterial synthesis of B and K
vitamins
 Storage and elimination of feces:
mostly rectum
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Colonic motility:
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Normally 18-24 hours are required for
material to pass through
Peristalsis (wavelike) contractions occur
slowly
Mass peristalsis or movement – strong,
rapid contractions of the colon which
moves feces (undigestible materials)into
the rectum – occurs several times a
day(esp. after a meal – gastro-colonic
reflex)
Defecation:
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Spinal reflex which empties the rectum:
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Pressure increases in the rectum,
initiates the defecation reflex which will
cause contraction of the rectum to push
feces out of the body.
Voluntary control can occur because the
external sphincter is composed of skeletal
muscle which can be voluntarily tightened
Liver and Gallbladder:
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An organ that fill most of the upper
abdomen – 2 lobes, right is larger
Hepatic, cystic and bile ducts transport
bile to intestine or gallbladder
Capable of regeneration
Each tiny section is capable of doing all of
the functions of the liver on a smaller
scale.
Functions of the liver:
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Stores glucose, lipids and vitamins (esp.
A,D, E, K and B12) and some minerals
such as iron & copper
Regulates blood composition -keeps
levels of nutrients at an adequate level
for body cells
Removes cell debris, pathogens,
hormones, antibodies, toxins, and drugs
and converts them into less toxic
materials for excretion by the kidneys or
in the bile.
Functions of the liver:
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Manufactures the anticoagulant heparin
and most of the blood proteins (clotting
factors)
Can convert some amino acids into other
varieties needed by the body.
Converts ammonia (a harmful waste
product of protein digestion) to urea (less
harmful) & is excreted by the kidneys.
Produces bile which breaks down fats
Kupffer’s cells eat bacteria & old WBC &
RBC’s (if not, bilirubin accumulates)
Gallbladder:
Stores and concentrates the bile
while it is not needed in the
intestine.
 Choleliths: gallstones – caused by
precipitation of cholesterol when the
concentration of some bile
components is abnormal.
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Blood flow:
Normally blood goes from heart to a
body organ and back to the heart.
 In the digestive system, blood flows
through the PORTAL VEIN to the
liver BEFORE going back to the
heart – the liver has a chance to
stabilize levels of nutrients (some
stored)
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Pancreas:
A soft, oblong gland about 6 inches
long and 1 inch thick
 Found beneath the great curvature
of the stomach
 Connected by the common bile duct
to the duodenum of the S.I.
 Composed of 2 lobes – the one
inferior to the stomach is larger
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Microscopic anatomy of the
Pancreas:
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Endocrine portion:
Islets of Langerhans – rely on blood to
transport their secretions (hormones)
 Alpha cells make glucagon
 Beta cells make insulin
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Exocrine portion:
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Acini cells release a mixture of
secretions:
Microscopic anatomy of the
Pancreas:
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Pancreatic juices/enzymes:
Protease – completes protein
breakdown left undone by pepsin
 lipase – breaks down lipids
 Carbohydrase – completes breakdown
of carbohydrates (pancreatic amylase)
 Ribonuclease/deoxyribonuclease –
breaks RNA and DNA into their
component nucleotides for absorption.
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Microscopic anatomy of the
Pancreas:
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Other important secretions:
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Bicarbonate HCO3
• Neutralizes gastric acid
• Creates pH 7.0 enteric environment
allowing enzymes to work best
Control of the digestive
system:
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Primarily controlled by the
parasympathetic nervous system (vagus
nerve).
Hormones can keep an ideal balance for
digestion:
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Stomach:
• Gastrin: increases motility and secretions –
speeds up movements to help mix food with
increased secretions.
Control of the digestive
system:
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Duodenum:
• Secretin: helps keep proper pH in the small
intestine. ( e.g. pH too low, secretin will be
released, pancreas makes more bicarbonate,
less acidic).
• Cholecystokinin: causes contraction of the
gallbladder& stimulates bile production.
Stimulates enzymes of pancreas.
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Histamines – sometimes released into
the tissues of the digestive system when
there is an infection, inflammation or
allergic reaction.
• This results in increased acid production by the
stomach.
• Pepsid-AC and Tagamet are actually antihistamines
Disorders:
Vomiting (emesis): forceful
expulsion of the gastric contents –
occurs because of a reverse
peristalsis that starts at the pylorus.
 Gastric reflux (GERD): “heartburn”
usually result of excessive gastric
motility, hiatal hernia, weak
sphincter, or excessive acid
production of the stomach
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Disorders:
Pyloric stenosis: defect in pyloric
valve – will not allow food to pass
into duodenum (often requires
surgery)
 Diarrhea: excess water in the feces
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Intestinal irritant ( microbe or toxin) or
injury to lining (cancer or infiltrate)
 Unabsorbed molecules (lactose or
laxatives)
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Disorders:
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S. Intestine has too much chyme passed
on to the colon and it is unable to deal
with it.
If caused by L. Intestine, there is a
proper amount of chyme, but unable to
deal with it, partially formed
Constipation: excessive distension of the
rectum & colon due to buildup
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Caused by decreased motility from
nerve/muscle damage, stress,
pregnancy, diet
Inflammatory disorders:
Gastritis
 Enteritis
 Hepatitis
 Pancreatitis
 Colitis
 Appendicitis
 Peritonitis
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Print materials: Mini Poster
My Plate
Contributing Factors to
Overweight/Obesity
computers
Junk
food
Behavioral
Factors
Portion
sizes
Video
games
t.v.
child
Fast
food
genetics
Pop
machines
Family
influence
Lack of
P.A.
Meals
Away from
home
Our kids are being bombarded with all
of these factors that promote a
sedentary, calorie laden lifestyle.
Look at what’s happened
over the last 50 years…
Obesity Trends in Children and
Adolescents
Ogden, et al. JAMA 2002;288;1728-1732
1960’s
2-5
year
olds
6-11
year
olds
12-19
year
19881994
19992000
7.2%
10.4%
4%
11.3%
15.3%
5%
10.5%
15.5%
Unfortunately, our
kids are just
following our lead.
Have you
noticed
your
pants
getting
You’re not alone.
tighter?
Obesity Trends* Among U.S. Adults
BRFSS, 1991-2002
(*BMI ≥30, or ~ 30 lbs overweight for 5’ 4” woman)
1991
1995
2002
No Data
<10%
10%–14%
15%–19%
20%–24%
≥25%
Obesity Trends* Among U.S. Adults
BRFSS, 1985
(*BMI ≥30, or ~ 30 lbs overweight for 5’ 4” woman)
No Data
<10%
10%–14%
Obesity Trends* Among U.S. Adults
BRFSS, 1988
(*BMI ≥30, or ~ 30 lbs overweight for 5’ 4” woman)
No Data
<10%
10%–14%
Obesity Trends* Among U.S. Adults
BRFSS, 1989
(*BMI ≥30, or ~ 30 lbs overweight for 5’ 4” woman)
No Data
<10%
10%–14%
Obesity Trends* Among U.S. Adults
BRFSS, 1992
(*BMI ≥30, or ~ 30 lbs overweight for 5’ 4” woman)
No Data
<10%
10%–14%
15%–19%
Obesity Trends* Among U.S. Adults
BRFSS, 1993
(*BMI ≥30, or ~ 30 lbs overweight for 5’ 4” woman)
No Data
<10%
10%–14%
15%–19%
Obesity Trends* Among U.S. Adults
BRFSS, 1995
(*BMI ≥30, or ~ 30 lbs overweight for 5’ 4” woman)
No Data
<10%
10%–14%
15%–19%
Obesity Trends* Among U.S. Adults
BRFSS, 1998
(*BMI ≥30, or ~ 30 lbs overweight for 5’ 4” woman)
No Data
<10%
10%–14%
15%–19%
≥20
Obesity Trends* Among U.S. Adults
BRFSS, 1999
(*BMI ≥30, or ~ 30 lbs overweight for 5’ 4” woman)
No Data
<10%
10%–14%
15%–19%
≥20
Obesity Trends* Among U.S. Adults
BRFSS, 2001
(*BMI ≥30, or ~ 30 lbs overweight for 5’ 4” woman)
No Data
<10%
10%–14%
15%–19%
20%–24%
≥25%
Obesity Trends* Among U.S. Adults
BRFSS, 2002
(*BMI 30, or ~ 30 lbs overweight for 5’4” person)
(*BMI ≥30, or ~ 30 lbs overweight for 5’ 4” woman)
No Data
<10%
10%–14%
15%–19%
20%–24%
Source: Behavioral Risk Factor Surveillance System, CDC
≥25%
Obesity Trends* Among U.S. Adults
BRFSS, 2005 (*BMI ≥30, or ~ 30 lbs. overweight for 5’ 4” person)
No Data
<10%
10%–14%
15%–19%
20%–24%
25%–29%
≥30%
Obesity Trends* Among U.S. Adults
BRFSS, 2010 (*BMI ≥30, or ~ 30 lbs. overweight for 5’ 4” person)
No Data
<10%
10%–14%
15%–19%
20%–24%
25%–29%
≥30%
Health Implications
Short Term
 Hypertension
 Abnormal glucose
metabolism
 Accelerated growth
 Orthopedic problems
 Sleep apnea
 Psychosocial problems
 Asthma
Long Term
 Increased risk for
CVD
 Increased risk for
some cancers
 Increased health care
costs
 Psychosocial issues
 Lead to being an
obese adult
Do Overweight kids make
obese adults?
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If a child is overweight at 6 years of
life, the likelihood that he or she will
be obese as an adult is greater than
50%
NEJM
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Source: Whitaker RC et at. (1997)
If an adolescent is obese, then he or
she has a 70% chance of remaining
obese
Source; Epstein LH et al. (1985)
AJCN