Transcript Digestion - Belle Vernon Area School District

Digestion
Digestion
I. Functions of the digestive system
1. Take in food.
2. Break down food.
3. Absorb digested molecules.
4. Provide nutrients.
5. Eliminate wastes.
Digestive System Video
II. Digestive Structure & Function
A. Organization
1. Alimentary Canal (GI tract).
a. 30 ft
b. Digest food
c. Absorb
nutrients
d. Eliminate
wastes
2. Accessory Organs
a. Located within
or outside the GI
tract.
B. Digestive Processes
1. Ingestion
2. Mechanical Digestion
3. Propulsion
4. Chemical Digestion
5. Absorption
6. Defecation
Review
• State the functions of the digestive system.
• Name & describe the 6 processes of the
digestive system.
III. Features of the Digestive System
A. Peritoneum
1. Parietal –serous membrane that lines
the abdominal pelvic walls.
2. Visceral (serosa) – lines the
organs.
3. Peritoneal cavity – Space
abdominal pelvic cavity.
within the
4. Falciform Ligament supportive
ligament for liver.
5. Mesentery- connective tissue that holds
many abdominal organs in place.
6. Lesser Omentum- mesentery that
connects the lesser curvature of the stomach
to the liver and diaphragm.
7. Greater Omentum (mesentery
proper) – mesentery connecting
the greater curvature of the stomach to
the transverse colon.
8. The greater omentum is usually
long, double fold mesentery that
extends inferiorly and loops back
to the colon creating a cavity
known as the Omental bursa.
9. Greater omentum usually fills
with fat depoists.
10. Retroperitoneal- abdominal
organs that lie behind the
peritoneum.
B. Wall Structure of the Alimentary
Canal
1. Mucosa – Mucus
membrane that lines the
lumen.
2. Submucosa – Loose
connective tissue
(blood & lymph tissues).
3. Muscularis – muscle
(circular & longitudinal
fiber).
4. Serosa – Visceral
peritoneum, outer
covering.
Review
• What is the functions of the mesenteries,
greater & lesser omentum?
• What are the layers of the digestive tract?
IV. Digestive Organs of the
Alimentary Canal.
A. Mouth & Accessory Organs
1. Lips & Checks
2. Palate
3. Tongue – large
muscular organ.
frenulum-attachs
tongue to floor of
mouth.
4. Teeth
a. Deciduous
20 by 2 yrs.
b. Permanent
32 between ,17-25 yrs.
1. Incisors – chisel – cutting
2. Canines – cone shape –
tearing
3. Premolars
4. Molars – broad
& flat - grinding
c. Structure
1. Crown – visible part of the
tooth.
* Enamel – protection,
hardest substance of the
body.
*Cells die shortly after
tooth break through,
incapable of repair.
2. Neck – between two regions.
3. Root – below gums.
4. Dentin – slightly harder than
bone, surrounds pulp cavity.
5. Pulp-Soft connective tissue
(blood & nerve).
Review
• List the functions of the lips, cheeks, &
tongue.
• What are deciduous and permanent teeth?
Name the different kinds of teeth?
• Describe the parts of a tooth. What are
dentin, enamel, & palate?
6. Salivary Glands
a. Saliva – 99.5% water, .5% solutes
1. Liquid medium for dissolving food
particles.
2. Lubrication for swallowing.
3. Enzymes –
Lysozyme –
destroys bacteria.
Salivary Amalyase
– begins chemical
digestion of
carbohydrates.
b. Glands
1. Parotid – Largest in front of ears.
2. Submandibular – floor of
mouth for mucus.
3. Sublingual – under tongue, for
mucus.
c. Digestion in Mouth
1. BEGINS IN THE MOUTH.
2. Mastication – Chewing.
3. Bolus – compact mass of food
& salvia.
B. Pharynx & Esophagus
1. Transports food from the mouth to
the stomach WITHOUT further processing
a. Nasopharynx
b. Oropharynx
c. Laryngopharynx
2. Deglutition
a. Voluntary – bouls moves to the back
of the mouth
b. Pharyngeal- reflex begins with the
evevation of the soft palate, then
pharyngeal muscles contract to
force food through the pharynx.
Epiglottis is tipped posteriorly.
c. Esophageal- swallowing by peristaltic
waves
Review
• What is the function of saliva?
• Name the salivary glands.
• What is the job of the esophagus?
C. Esophagus
1. Muscular tube
2. 10 inches long
3. Collapsed when not propelling food
4. Behind trachea
5. Esophageal hiatus – opening of esophagus
6. Esophageal sphincters
a upper
b. Lower esophageal sphincter – valve
that prevents upward movement.
heartburn – weak & permits
leakage of stomach juices which
irritation to esophagus.
D. Stomach – Mechanical & Chemical Digestion
1. Stomach
a. Pouch – 10 inches long
b. Rugae – deep folds in inner lining
c. Greater Curvature – Convex
d. Lesser Curvature – Concave
e. Four Regions
1. Cardia – Opening that receives food.
2. Fundus – Expanded regions above cardia, temporary holding
regions.
3. Body – Main part.
4. Pylorus – Narrow inferior region
f. Sphincter – Keep content within stomach
1. Cardiac – Esophagus & Stomach
2. Plyorus – Stomach & small intestines
2. Stomach Wall
a. Four basic layers
1. Mucosa
-gastric pits
-gastric glands
Parietal cell – HCL, Intrinsic factor
Chief Cell – Pepsinogen -> pepsin
Mucus Cells – Mucus
-Gastric Juices 2-3 L/day
2. Sub-mucosa
3. Muscularis
Additional layers that mix & churn
4. Serosa
3. Function of Stomach
a. Mechanical Digestion – mixing & churning
b. Chemical Digestion – Gastric juices
1. Chief Cell – Pepsinogen (inactive to prevent it from digestion of own cells)
2. Parietal Cell – HCL which activates pepsinogen to pepsin.
3. Pepsin breaks down nearly all protein.
4. Mucus – Coats to prevent digestion of stomach.
-gastric ulcers
c. Absorption
1. Salts
2. Glucose
3. Alcohol
4. Asprin
5. Lipid Soluble drugs
6. Water
d. Propulsion – Peristalsis
1. Chyme- small food particles & gastric juices.
2. Mixing waves- weak contraction which mixes
food with stomach secretions.
3. Peristalic waves- stronger contractions that
force chyme toward and through the pyloric
sphincter.
e. Intrinsic Factor
Parietal & Chief Cells – aids in Vitamin B12
absorption by small intestines, which is
important in RBC production.
Review
• Describe the parts of the stomach.
• How are the stomach muscles different from
those in the esophagus?
Digestion from the inside
f. Regulation of Stomach Function
1. Beginning of Digestion
-Primary by involuntary control center of the brain &
hormones – Positive Feedback
Brain (hypothalmus)
Cephalic Phase - Smell, think, see, hear
Medulla
Gastric phase -Gastric Glands
Gastirc Juices
Continued Reflex (Stretching of stomach by food)
2. Ending of Digestion
Intestinal phase -Presence of acid in upper small intestine
triggers nerve reflex to stimulate contraction of the pyloric
valve, which prevents more acid from entering
.-Secretin & Cholecystokinin (CCK) intestinal hormones.
Inhibits stomach peristalsis & stimulate
pancreatic enzyme & bile into small intestines.
3. Regulation
a. Controlled by the involuntary brain & hormones
1. Secretnin
-Released into the bloodstream because of the
HCL in the small intestines.
-inhibits the gastric secretion.
-Causes pancreas to release bicabonate ions
to neutralize the pH.
2. CCK
-Release in response to fats & proteins into the
small intestines.
-Cause the pancreas to release pancreatic
juices.
-Digestion to release pancreatic juices.
-Inhibits gastric juices & peristalsis.
4. Small Intestines
A. Structure
1. Longest segment of the GI tract (20 ft).
2. 1 inch in diameter.
3. Three segments
-Duodenum- receives chyme from the
stomach,10 in long.
-Jejunum – 8ft
-Ileum- 12 ft – unites the small & large intestines
- Ileocecal Valve
B. Wall of intestines –
Same four layers with modification - increase Sa
by 600 X’s
circular folds mucosa & submucosa
villi
lacteal – lymphatic vessel
microvilli
Small Intestines
C Layers
1. Mucosa
a. cells
-absorptive – have microvilli, produce digestive
enzymes, absorb digested food.
- goblet – produce mucus.
- endocrine – produce regulatory hormones.
- granular (Paneth’s cell)- help protect from bacterial
infection.
b. glands
Intestinal glands – secretes water & mucus.
Duodenal glands – produce mucus.
2. Submucosa
Bruner’s glands – only in walls of duodenum for neutralizing.
(Payer’s patches) – fights off infection.
3. Muscularis
4. Serosa
C. Function
1. Completes chemical digestion
a. Pancreatic enzymes – pancreatic duct
b. Bile – common bile duct
- peptidases- proteins
- disaccharides- disaccharides into
monosaccharides. (maltose & isomaltose)
2. Absorption – main site of nutrient absorption
(duodenum & jejunum).
3. Propulsion – mix & move contents toward the
large intestines.
Peristaltic contraction- through the intestine.
Segmental contraction – mixing in short segments
a. Diarrhea – too fast
b. Constipation – too slow
Review
• 1. What secretions complete the chemical digestion
of food particles?
• 2. What nutrients can be absorbed by the intestinal
walls?
• 3. How are the layers of the small intestine modified
for their function?
• 4. What are circular folds, villi, & microvilli in the
small intestine? What are their functions?
5. Large Intestines
- Absorption of water
- Process of defecation
A. Structure
1. 5 ft, 3in in diameter
2. 4 segments.
a. CecumReceives material from the ileum.
Short pouch like segment below ileoceal
valve.
Vermoform appendix – appendicitis.
b. Colon- Main absorption site
Ascending
Transverse
Descending
Sigmoid
B. Rectum – Storage of fecal material
C. Anal canal – Opens to the exterior.
Internal sphincter – involuntary- smooth.
External- voluntary - skeletal
D. Wall of intestine
1. Same four layers with modification.
-Mucosa –
Lack villi, has deep folds, large
number of mucus secreting cells to
bind contents together & for easier
defecation.
-Submucosadeep folds
-Muscularis –
three bands
taenai coli form pouches called
– haistra.
-Anal Canal –
Parallel ridges to reduce friction
during defecation.
2. Function
a. Mucosa absorbs much of the remaining water & electrolytes in
chyme.
b. Chyme harden – feces 75% water & 25% indigestible wastes.
c. Color is a result of bile altered by bacteria.
1. Most there than anywhere else in the body.
2. Produces vitamin K
3. metabolism produces gases, CO2, Methane, hydrogen
sulfide.
4. Most of gas is swallowed air.
3. Defecation or Elimination
a. Propulsion (peristalsis of feces through the large intestines (18-24
hrs) for colon.
mass movements- 8-12 hrs , moves contents 20 cm towards
anus.
b. Stores until the rectum is full
c. Once full, nerve receptors in rectal wall stimulate defecation reflex.
parasympathetic reflex
Review
• 1. What are the divisions of the large
intestines?
• 2. What is the function of the large intestines?
• 3. How is chyme converted to feces?
• 4. Describe the defecation reflex.
V. Accessory Organs
A. Pancreas – Wide range of enzymes
1. Structure
a. Head
Body
Tail
b. Acini – exocrine secretory cells.
Pancreatic juices into the pancreatic ducts &
fuses with the common bile duct.
c. Islets of Langerhans – Produces insulin & glucagon
2. Function
a. 1500ml/day
b. Pancreatic Amylase – Carbohydrates
c. Tyspin – Protein
d. Chyotrypsin – Protein
e. Pancreatic Lipase – Lipids
f. Nucleases – breaks down DNA & RNA
Pancreas Video
B. Liver – Largest internal organ of the body at 1.36 Kg.
1. Structure
a. Lobes or sections
1. Right – large
2. Left – small
b. Caudate and quadrate– smaller sub divisions of the
lobes.
c. Porta – gateway to the liver
d. Hepatic artery- oxygen rich blood to the liver
e. Hepatic veins – oxygen poor blood from the liver to the
vena cava.
f. Hepatic portal vein – oxygen poor blood but high in
nutrients to the liver.
g. Lobules-smaller divisions .
h. Portal triads three structures
1. hepatic artery
2. hepatic portal vein
3. hepatic duct
i. Hepatic cords
j. Hepatic sinusoids
k. Hepatocytes
Liver
Liver Lobules
k. (cont.)Hepatocytes – Liver cells arranged in columns around a
central vein.
l. Kupffer cells – Phagocytic cells that remove bacteria from the
blood that came from the digestive tract.
m. Bile Canaliculi- Secrete bile.
n. right hepatic duct
o. cystic duct
p. Common bile duct
q. Duodenal papilla opening in small intestines from the common
bile duct and the pancreatic duct.
2. Function
a. Secretion of Bile, 700 ml/day
-Emulsification of fats.
-Absorption of vitamin A,D,E, & K.
-bilirubin-bile pigments
b. Metabolism of lipids
-Lipoproteins – package of fat for transport & storage.
-HDL’s – transports cholesterol to liver –
beneficial in repair, growth, but tends to
accumulate in the body spaces when not used.
-LDL’s – Transport cholesterol to cells-production of
hormones, harmful-atheroscerosis.
-VLDL’s
c. Stores glycogen, vitamins A, D, B12
d. Detoxifies harmful substances in the blood stream – alcohol.
3. Control of Bile secretion & release
a. Secretin – liver
b. Cholecystokinin – gall bladder
c. 90 % of bile is reabsorbed in the ileum
V. Digestion, Absorption and Transport
A. Carbohydrates
1. cotransport and active transport
B. Lipids
1. simple diffusion
2. Chyle – lymph that contains high amount of
absorbed lipids.
Types of lipoproteins
C. Protein
1. Cotransport
2. Active transport
Digestion Summary
Water & Mineral Absorption
9L goes into the digestive tract
each day.
92% of the water is absorbed by
the small intestine.
7% in the large intestine.
1% leaves the body with feces.
Minerals (Na, K, Ca, Mg, P) are
actively transported.
V. Disease
A. Dysentery
Sever infection of intestinal wall
Cramping & diarrhea
Caused by protozoans, bacteria, &
viruses
Blood or mucus in feces.
B. Hemorrhoids
Enlarge veins lining the anal canal
C. Hiatal Hernia
Protusion of the stomach through the
diaphragm & thoracic cavity.
D. Peptic ulcers
Increased acid secretion & digestive enzymes
the mucosal lining.
Stomach – gastric ulcer
Intestine –intestinal ulcer
Abdominal pain
E. Hepatitis
Inflammation & death of liver tissue
Virus or chemical toxin (alcohol)
Type A – transmitted by food, liquids, & body fluids
Type B – Serum – blood & blood products
Type C
Anorexia – refusal to eat
Malaise – lack of energy
Nausea
Diarrhea
Vomiting
Fever
erodes
F. IBS
G. Typhoid fever – Salmonella typhi
H. Cholera – Vibrio cholerae 12-20 L of fluid/day
I. Tape wormDysentery –
J. Hookworms