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The Digestive System

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on 24 February 2014

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Transcript of The Digestive System

submandibular gland: located under the tongue; The secretion is a mixture of serous and mucous.
Produces 70% of all saliva, even though it is much smaller than the parotid gland.
Priscilla Giang
Sania Luna
Candice Romero
Kristie Sham
AP Bio

The Digestive System
Liver Structure
Variability based on Diet
Esophagus Structure
Structure & Function of Appendix
Structure of Pancreas
Function of Pancreas
Gallbladder Structure
Blood regulation:
Metabolizes toxic substances
Removes/stores iron and vitamins
Produces proteins in blood plasma
Controls cholesterol levels
Stores glucose as glycogen
Breaks down glycogen and releases ammonia as a byproduct
Liver has first access to nutrients from intestinal villi that converge to the hepatic portal vein
Disorders and Diseases
Hepatitis: inflammation, commonly caused by viruses, transmitted via
(A) contaminated food/water
(B) sexual contact/blood transfuions
(C) contact with infected blood
Cancer,Alcohol Damag, Drug Damage --> Cirrhosis: fatty tissue replaced by scar tissue
Largest internal organ, largest gland, self-repairing
Hepatocytes re-enter the cell cycle for regeneration
Can regenerate from 25% of its original mass
Gallbladder Function
Removes water and ions from bile for higher concentration
Sensory receptors in duodenum detects carbohydrate-rich foods
Stimulation of CCK (cholecystokinin) production
Contraction of gallbladder smooth muscle to release bile into small intestine
When not digesting, pancreatic obliary sphincter closes to block bile access to the duodenum
Disorders and Diseases
Cholesterol content of bile can crystallize into gallstones that blocks the passageway to the small intestine
Leads to
indigestion, infection, pain, nausea, vomiting
Jaundice: yellowing of skin when excess bilirubin is deposited into tissue
Liver damage
Both a exocrine(ductal) and endocrine(ductless) gland
Acinar Cells collect into ducts and join the
duct of Wirsung
(pancreatic duct)
Four Main Regions
Acinar tissue produces digestive enzymes for the small intestine
vasoactive intestinal polypeptide (VIP)
relaxes gastrointestinal tract
triggers hormone release from pancreas, gut, hypothalamus
breaks down fat and glycogen
stimulates bile flow
: produced by islets of Langerhans and blocks insulin and glucogon production
Trypsin (protease), Chymotrypsin (protease), pancreatic lipase (breaks down fat), and pancreatic amylase (breaks down starch)
Stomach Functions :

Structural and
functional unit
Hepatic Artery carries oxygen-rich blood to the liver
Hepatic Portal Vein carries nutrients from intestines
Bile Production
: yellow-green alkaline solution that consists of water, bile salts, bile acids, phospholipids, cholesterol, pigments and electrolytes
Bile leaves

and drains into the

What gives bile its color?
: pigment that is derived from heme in red blood cells
Bile is released into the small intestine for

fat emulsification
: breaking up fats to increase surface area, increased exposure to enzyme lipase
Four major Bile Acids
Bile helps the absorption of
lipid-soluble substances
, such as cholesterol, vitamin D, vitamin K, and carotene
Fat Fat Droplets
Fat Droplets + H2O glycerol + 3 fatty acids

bile salts
Lower Esophageal Sphincter (LES):
one way valve connects from esophagus
to the stomach
-The opening of the esophagus into the stomach
(LES) does not tighten enough or opens too often
Chemically and physically broken down = chyme
Hydrochloric Acid:
destroys bacteria and alters pH levels
enzymes that break down ingested food
muscularis externa:
smooth muscle that contracts in wall of stomach
churns food, acid, and enzyme around like a clothing machine
Essential vocab
Bulk Storage
mechanical breakdown of ingested food
breakdown of chemical bonds through enzymes and acids
Production of Intrinsic Factor necessary for absorption of B12
vitamin B12:
gastric juice:
Pancreatis: inflammation
Pancreatic Cancer
Cystic Fibrosis: mucus blocks tubes
Lack of insulin production can lead to Diabetes Mellitus
Type I: Metabolizes fat instead of glucose, increases blood acidity
Type II: Adipose tissue impairs insulin receptors, insulin resistant cells

Diseases & Disorder of Pancreas
intrinsic factor:
a mixture of mucus, HCl, and enyzmes
glycoprotein that binds to vitamin b12 and allow the protein to be absorbed by small intestine
essential nutrients for red blood cells
semifluid mass of partly digested food
mass of food that has been chewed at the point of swallowing
expandable folds located at interior surface of stomach
-Main job is to expand and make room for more food
-contains rugae folds.

Parietal cells:
Chief cells:
Mucus cells:
produces Hydrochloric acids and intrinsic factor
produces pepsin and lipase
produces mucus
The main functions of the pylorus are to prevent intestinal contents from reentering the stomach when the small intestine contracts and to limit the passage of large food particles or undigested material into the intestine.
pyloric sphincter:
opening passage allows food to pass or stay
The Oral Cavity Structure
The presence of food triggers a nervous reflex that causes the salivary glands to deliver saliva through the ducts and into the mouth
saliva helps with the breaking down of the food
three types of salivary glands:
Salivary Glands
the teeth mash up the food
the tongue is composed of striated muscle and an outer layer of mucous; it mixes the chewed food with saliva
salivary amylase
: an enzyme that hydrolizes starch and glycogen
starch + H2O -
salivary amylase
-> maltose
maltose is digested into glucose by maltase, an enzyme produced by the small intestine
maltose + H2O -
-> glucose + glucose
during swallowing, the tongue pushes the food to the back of the throat, into the pharynx
a series of muscle contractions that occur in your digestive tract
Feed me back
sublingual gland
: under the tongue;there are no striated ducts present in the ductal system of these glands.
stomach growling:
: largest gland; situated along the cheek and jawline in front of each ear between the skin and muscle; produce a serous, watery secretion.
Food in stomach = quieter growling
-process of peristalsis turning food into chyme
-hormones stimulated to send nerves to the brain
-time span of 2 hours
-peristalsis starts again
Small Intestine Structure
Function of Small Intestine
Disorders and Diseases
Structure of Large intestine
Function of Large Intestine
Disorders and Diseases
Consists of:


Large Intestine
Absorbs H20, salts and some vitamins

undigested material
until it is
as feces
*Does not produce digestive enzymes

Each part:
- expands to move undigested material into colon
- absorbs remaining H2O
- stores and
regulates elimination of feces

passage for food to travel to the stomach
: a series of wavelike muscle contractions that propel food in one direction
at the end, a muscular ring, the sphincter , opens and shuts to allow food to pass into the stomach
under the control of the enteric nervous system

Consists of 3 segments:
receives bile & pancreatic juice
Finishes the process of chemical digestion
Breaks down food
using enzymes released
from the pancreas and bile from the liver
Absorbs nutrients

A Closer Look
fingerlike projectiles at the walls of the small intestine
increases surface area
of small intestine
absorbs small nutrient molecules

covered by an outer layer of epithelial cells
-each has thousands of microvilli
Microvilli increases surface area of villi
-amino acid and glucose enter the blood vessels of a vilus
- glycerol and fatty acids are joined and packaged as lipoproteins before entering lacteals (lymphatic vessels in the vilus)
Duodenum- largely responsible for the continuous break down process
Jejunum & Ileum
- responsible for the absorption of the nutrients into the bloodstream
Pharynx Structure
a juncture that opens to both the esophagus and trachea
region we call our throat
fibromuscular tube that extends from the base of the skull to the esophagus
The muscular walls of the pharynx are comprised of an outer layer made up of 3 circularly disposed muscles, the constrictors. The constrictors are named the superior, middle and inferior pharyngeal constrictors
submandibular gland
: found under the tongue; The secretion is a mixture of serous and mucous
The oral cavity consists of:
salivary glands
The Oral Cavity's Function
Intestines vary among vertebrates
Are closely related to:
- body size
- level of activity

Several Common Problems
Serious Conditions
- is a weakening of the wall of the large intestine
leading to pouching of the inner membrane. These pouches can become infected requiring antibiotics or surgery. Increasing dietary fiber may help prevent this condition.
Ulcerative Colitis
- an inflammation of the lining of the colo
Irritable bowel syndrome (IBS) -
causes abdominal cramping, bloating, and a change in bowel habits
Pharynx Function
* Contains good bacteria that helps with producing feces
Celiac disease-
an genetic disease in which people can't eat gluten because their immune system will respond by damaging their small intestine.
Lactose Intolerance-
the body lacks the proper enzymes, which usually lie in the lining of the microvilli, that digest lactose
Small Bowl Obstruction
- either a functional or mechanical problem which prevents or slows down the movement of food, is a potentially dangerous condition
Tropical Sprue
- characterized by abnormalities in the lining of the small intestine that may result in increased water loss as well as poor absorption of folic acid and salts
*Has a surface area
the size of a tennis court
Does it have a function?
Storage of good bacteria to replace bacteria purged after chola or dysentery
Koalas have large appendixes
Appendicitis: inflammation as a result of stool or cancer, blockage of appendiceal lumen
Removal of appendix has no adverse affects
Cow stomach
-one stomach with four digestive
the act of swallowing takes place here
it closes off the trachea so that food does not fall into it and choke you
Esophagus Function
Disorders and Diseases
- largest part of cow's stomach
- food is regurgitated and swallowed again and again
-13 to 48 hours

-traps unwanted material
-softens the grass and turns it into cud
-contains folds that breaks down cud and squeezes out
-passes nutrients through bloodstream and sends rest
to the intestines
a muscular tube extending from the pharynx and behind the trachea to the stomach
before the opening to the stomach is an important ring-shaped muscle called the lower esophageal sphincter (LES)
-have to eat grains to digest more easily (monogastric system)
-animals that contain a the process that can breakdown cud and plants to stimulate digestion
-has two extra compartments like the cow (except cow has four)
-monogastric just like humans and pigs
Evolutionary advantages:
the amount and type of teeth found in an organism can show how far the organism adapted
Vomiting :
- stimulation in nervous system (dopamine receptors)
- increased saliva and deep breathing occurs
-relaxation of pyloric sphincter = explosion (brings up content from the gut
-treatment:ice cold water or crushed ice, find the source of the vomiting (what caused it)
very rare and usually happens because acid levels are inconsistent
- bacteria and viruses increase the amount of liquid
secreted in the stomach and makes it flow too quickly
-food remains stagnant in stomach
- if continues, then blood will start
to leak and possibility of vomiting
blood occurs
pyloric stenosis:
narrowing in opening between stomach and the intestines
-severe and uncontrollable vomiting
Barrett's Esophagus: a condition in which cells of the esophagus
esophageal cancer
gastroesophageal reflex disease
acidic stomach contents back up into the esophagus, causing irritation and heartburn
Digestive Tracts
Incomplete vs Complete
Disease and Disorders in the Salivary gland
Single opening (mouth)
Digestive enzymes in tract
Intracellular digestion
Diffusion of nutrients into nearby cells
Diseases and Disorders in the Pharynx
Mouth & Anus: opening for food entrance and waste exit
Extracellular digestion in intestines
Increased surface area of digestive tract
Continuous vs Discontinuous
Aquatic animals
Continuous water passage & nutrient collection
Temporary food storage
Less feeding time
Example: Baleen Whale
Adaptations to specific diets
Larger meals
Rapid consumption, gradual digestion
Long term energy storage
Specialization of organs
Increase in Surface Area = Increase in Substrates = Increase in enzymatic reactions
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