Download a) digestive system functions

DIGESTIVE SYSTEM
READING: Chapter 15
1
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)
2
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….
3
B. GENERAL STRUCTURES
(Fig 15.1)
Mouth (salivary glands, tongue, palate, & teeth)  pharynx (throat)  esophagus stomach
4
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)
5
C. CROSS-SECTION (4 layers)
4) Serosa -visceral peritoneum
-outermost layer
-serous membrane
-continuous w/ parietal peritoneum
6
Parietal Peritoneum:
-lines abdominal cavity
-folds in some places
Fig 15.24
7
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
8
D. ORGANS
1) Mouth - cheeks and lips
(Fig 15.5)
9
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 _________________
10
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
11
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
12
Each type of tooth has a special function
13
3) Teeth
-coated with enamel
-bacteria make acid  breaks down enamel  dental caries
(Fig 15.9)
14
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
15
4) Salivary Glands
-all 3 make saliva: -almost 99% H2O
-mucous (function?)
-enzymes = salivary amylase
starch Salivary amylase
maltose
16
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?
17
6) Esophagus -10” tube from pharynx to stomach
-lined with ________________epithelium
-separated from stomach by cardiac sphincter
-sphincter prevents acid reflux
18
• 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
19
20
21
22
23
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…)
24
-3 muscle layers in the stomach
-alternating contractions to churn & mix chyme
25
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
26
27
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)
28
29
30
31
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?
32
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
33
34
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
35
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
36
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 _________
37
9) Pancreas
-next to the stomach & duodenum
-has endocrine functions (hormones) & exocrine (enzymes)
functions
(review anatomy)
38
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?
39
Does the pancreas released enzymes all the time?
Enzyme release is controlled by hormones
made by the duodenum in response to chyme
40
What hormone regulates secretions from
the stomach?
Gastrin
41
Pancreatic secretions are regulated by the hormone
SECRETIN
42
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?)
43
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
44
10)
Large intestine (functions)
-bacteria make vitamin K
-site of water & mineral absorption
-collect undigested material & form feces
-regulation of defecation
45
10)
Large intestine (regulation of defecation)
-anal canal has 2 sphincters: -internal sphincter = smooth muscle
-external sphincter = skeletal muscle
46
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
47
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?
48
Diverticula = a pouch in the wall of an organ
Diverticulitis = if the pouches become inflamed
49
11)
Liver (structure)
-largest internal organ
-4 lobes (left, right, quadrate, caudate)
-2 ligaments (round and coronary)
50
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
51
52
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
53
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 _______________________
54
When is bile released into the duodenum?
-When fatty foods enter the duodenum
NOTE: Does bile digest fat?
55
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?
56
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
57
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…
58
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:
59
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?
60
CCK is a hormones that regulates bile release into duodenum
61
12) “gall stones” or “bile stones”
- Form when bile is too concentrated
62