Download a) digestive system functions

DIGESTIVE SYSTEM
READING: Chapter 15
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A) DIGESTIVE SYSTEM FUNCTIONS
1) Digestion = break food down into components for absorption:
a) CHO’S 
simple sugars
b) Protein 
amino acids
c) Fats 
fatty acids and glycerol
2) Absorption of nutrients (into blood & lymph)
3) Temporary storage & elimination of wastes
4) Vitamin production in colon (bacteria)
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B. GENERAL STRUCTURE
1) Alimentary Canal = the whole tube = approx. 30 ft. or 9 m long
2) Accessory structures that secrete into AC: salivary glands,
pancreas, gallbladder, liver….
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B. GENERAL STRUCTURES
(Fig 15.1)
Mouth (salivary glands, tongue, palate, & teeth)  pharynx (throat)  esophagus stomach
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small intestine (duodenum, jejunum, ileum) large intestineanus
C. CROSS-SECTION of intestine(4 layers)
1) Mucosa
-at lumen surface
-produces mucous & absorbs nutrients...
2) submucosa -CT w/ lots of blood vessels (carry nutrients away)
3) muscularis mucosa -2 layers of smooth muscle: *inner circular
*outer longitudinal
-important for peristalsis
(Fig 15.3)
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C. CROSS-SECTION (4 layers)
4) Serosa -visceral peritoneum
-outermost layer
-serous membrane
-continuous w/ parietal peritoneum
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Parietal Peritoneum:
-lines abdominal cavity
-folds in some places
Fig 15.24
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Folds in parietal peritoneum:
a) lessor omentum -attaches to lessor curvature of stomach & liver
b) greater omentum -from greater curvature of stomach
-lies over the intestines (like an apron)
c) mesentary -anchors small intestines & prevents twisting
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D. ORGANS
1) Mouth - cheeks and lips
(Fig 15.5)
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2) Tongue -muscular organ important for taste, chewing,
swallowing, and speech
-why are taste buds important?
-attached at front by frenulum (to floor of mouth)
-attached at the back by _________________
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3) Teeth - mechanical breakdown of food
a) “baby teeth” = deciduous teeth or primary teeth
-appear ~ 6 months and fall out ~ 6 years
-dental formula = 2-1-2
2 incisors
1 canine (cuspid)
2 molars
total = 20 teeth
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3) Teeth
b)
permanent (secondary) teeth
-adult dental formula = 2-1-2-3
2 incisors
1 canine (cuspid)
2 premolars (bicuspid)
3 molars
total = 32 teeth
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Each type of tooth has a special function
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3) Teeth
-coated with enamel
-bacteria make acid  breaks down enamel  dental caries
(Fig 15.9)
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4) Salivary Glands (3 pairs in mouth)
1) parotid
-biggest
-near masseter muscle
-saliva  ducts  mouth…what type of gland?
2) submandibular gland
3) sublingual
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4) Salivary Glands
-all 3 make saliva: -almost 99% H2O
-mucous (function?)
-enzymes = salivary amylase
starch Salivary amylase
maltose
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5) Pharynx -the throat
-common chamber for digestion & respiration
-bolus moves into pharynx when we swallow
-can be divided into 3 regions…do you remember?
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6) Esophagus -10” tube from pharynx to stomach
-lined with ________________epithelium
-separated from stomach by cardiac sphincter
-sphincter prevents acid reflux
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• Swallowing is subconscious & conscious
Bolus moves to back of pharynx
Bolus touches sensory receptors
Swallowing center in medulla oblongata is activated
Soft palate closes nasopharynx
Larynx moves up & presses epiglottis blocks trachea
Vocal cords close
Peristaltic wave begins to stomach
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7) Stomach -“J” shaped organ, ~ size of a big sausage (empty)
-rugae = folds (why are these folds important?)
-storage sack for food
-very little absorption here (exceptions…)
-cardiac sphincter at top (function…)
-pyloric sphincter at bottom (function…)
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-3 muscle layers in the stomach
-alternating contractions to churn & mix chyme
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Stomach Secretions
1) pepsin = enzyme that breaks down proteins to polypeptides
2) HCl = -creates an acidic environment (pH = 2.5)
-pepsin works really well in an acidic environment
-provides protection against pathogens
3) mucous - why is this important?
4) gastrin -hormone released when we see, smell, taste food
-stimulates production of ______ & __________
-when stomach is emptied, gastrin production _____
5) CHYME = milky paste = secretions + food
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ULCERS
-If mucous doesn’t protect stomach from pepsin & HCl
-Major cause = bacterium (Helicobacter pylori)
-Other contributing factors: -smoking
-alcohol
-stress
Bleeding Ulcer = sub-mucosa has been invaded
Perforated Ulcer = acid eaten all the way through (very serious, deadly)
Duodenal Ulcer = in duodenum (common b/c no acid protection)
-Treated with pharmaceuticals (surgery = rare)
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8) Small Intestine (3 portions)
Function = digestion & absorption of nutrients
1) Duodenum -first curve under stomach, about 12 inches long
2) Jejunum -middle portion, ~ 8 ft. long
3) Ileum -end potion, ~ 12 ft. long
-ileocecal valve (flap-like) guards exit to lg. Intestine
-severe vomiting = void contents of stomach & sml.
intestine only
What structure prevents twisting?
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Small intestine wall is modified to increase surface area:
1) Plicae circulares = large folds
2) villi = small finger-like projections
3) microvilli = brush border on the villi
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Nutrients Absorbed In Small Intestine
-primary site for absorption:
-simple sugars & AA’s by active transport into blood capillaries
-fatty acids & glycerol by diffusion into lacteals
-fat soluble vitamins (ADEK) follow fats
-water absorbed by osmosis
-water soluble vitamins move with water
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Digestive Processes in Small Intestine
(some enzymes are made here)
Starch is broken down into maltose by what enzyme? Where?
maltase
Maltose
glucose + glucose
sucrase
Sucrose
glucose + fructose
lactase
Lactose
glucose + galactose
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More Digestive Processes in Small Intestine
pepsin
Protein
polypeptides
trypsin
Polypeptides
dipeptides
aminopeptidase
Dipeptides
amino acids
But, most of the digestive enzymes come from the _________
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9) Pancreas
-next to the stomach & duodenum
-has endocrine functions (hormones) & exocrine (enzymes)
functions
(review anatomy)
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9) Substances made by the pancreas: (4 enzymes)
a) pancreatic amylase:
breaks down starch  maltose
b) pancreatic lipase: breaks down fats  fatty acids + glycerol
c) trypsin & chymotrypsin: break down polypeptides  dipeptides
d) sodium bicarbonate (baking soda): neutralizes HCl
-Where does HCl come from?
-If there isn’t enough sodium bicarbonate what might happen?
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Does the pancreas released enzymes all the time?
Enzyme release is controlled by hormones
made by the duodenum in response to chyme
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What hormone regulates secretions from
the stomach?
Gastrin
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Pancreatic secretions are regulated by the hormone
SECRETIN
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10) Large Intestine
cecum  ascending c  transverse c  descending c  sigmoid c  rectum  anus
Appendix attached to cecum:
-lymph tissue
-inflammation = appendicitis
-removed surgically (why?)
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10) Large Intestine (structure)
-unique muscularis mucosa: -circular layer = complete
-longitudinal layer = incomplete haustra
-NO villi in colon
-lots of mucus producing goblet cells (why?)
-movement = “rolling”, occasional
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10)
Large intestine (functions)
-bacteria make vitamin K
-site of water & mineral absorption
-collect undigested material & form feces
-regulation of defecation
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10)
Large intestine (regulation of defecation)
-anal canal has 2 sphincters: -internal sphincter = smooth muscle
-external sphincter = skeletal muscle
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10)
Large intestine (regulation of defecation)
-2 sphincters:
1.
2.
3.
4.
5.
-internal sphincter = smooth muscle
-external sphincter = skeletal muscle
When colon is full, contractions start
Reflexes from spinal cord  relaxation of internal sphincter
IF it’s an appropriate time, you relax external sphincter
IF it’s NOT an appropriate time, contraction of external sphincter
NOTE: potty training needed to learn step 4…usually at age 2-3
IF feces stay in colon  more water absorbed  constipation
IF feces passes quickly  water isn’t absorbed  diarrhea
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Flatulence
- Bacteria feed on undigested foods in colon
- “flatus” = the gas produced by these bacteria
- What are some foods that humans don’t digest very well?
- Why is it important to include these foods in your diet?
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Diverticula = a pouch in the wall of an organ
Diverticulitis = if the pouches become inflamed
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11)
Liver (structure)
-largest internal organ
-4 lobes (left, right, quadrate, caudate)
-2 ligaments (round and coronary)
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Hepatic Portal Circulation (review from cardio lec.)
- blood from the capillaries in the intestines  LIVER
Capillaries of intestines
Venules  Veins
Hepatic Portal Vein
Venules  Capillaries in liver (toxins & nutrients removed)
Venules  Veins  Central Vein  Inferior Vena Cava
Heart
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11) Liver (structure)
Each lobe is made up of many tiny “lobules”
-hepatic triad (branch of hepatic portal vein, branch of hepatic artery, bile duct)
-sinusoids (vascular channels leading to central vein, lined w/ macrophages)
-central vein (leads to inferior vena cave)
-bile canals  bile ducts  hepatic duct  common bile duct
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11) Liver (functions)
a) Production & Secretion of Bile
-Bile contains the waste product = bilirubin (yellow-green)
When is bilirubin made?
-Bilirubin is usually removed from blood  bile
What condition develops if bilirubin accumulates in tissues?
-Where does bile go once it’s made?
Stored in the __________________________
Released into the _______________________
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When is bile released into the duodenum?
-When fatty foods enter the duodenum
NOTE: Does bile digest fat?
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Why are feces brown?
Biliruben (green/yellow)  Duodenum (part of bile) Move through sml. intestine 
Colon (bacteria change color of biliruben from green to brown)  Determines what?
Why do infants have yellow to green feces?
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11) Liver (other functions…see Table 15.3)
b) CHO metabolism: -stores glucose as glycogen
-breaks down glycogen to glucose
c) Lipid metabolism: -makes phospholipids & cholesterol
-converts CHO and protein to fats
d) Protein metabolism:
-makes some proteins
-forms urea
e) Filters blood: -destroys old red blood cells (making bilirubin)
f) Storage:
-vitamins A, D, and B12, glycogen, iron
g) Detoxification:
-removes toxins from blood
-chelates heavy metals
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11)
Cirrhosis of the Liver
-occurs when the liver can’t replace damaged tissue fast enough
-healthy liver tissue is destroyed and replaced with CT
-liver becomes enlarged (CT & cell division = hyperplasia)
-due to alcohol, viruses, heavy metals, drugs, etc…
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11)
Hepatitis
-inflammation of the liver
-usually viral
-5% of hepatitis carriers develop liver cancer
Hepatitis A: -oral/fecal transmission
-generally acute
Hepatitis B: -contaminated body fluids
Hepatitis C: -blood and fetal transmission
-responsible for 50% of all hepatitis cases
-chronic symptoms in 60% of all sufferers
Hepatitis D:
Hepatitis E:
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12)
Gall bladder
-storage site for bile made in the liver
-bile in gall bladder  cystic duct common bile duct  duodenum
-when does the gall bladder contract?
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CCK is a hormones that regulates bile release into duodenum
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12) “gall stones” or “bile stones”
- Form when bile is too concentrated
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