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The Digestive System

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Megan Hernke

on 23 March 2015

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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.
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 Damage, 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 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(secretes pancreatic juices) and endocrine(secretes hormone into blood) gland
Acinar Cells collect into ducts and join the 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 and hypothalamus
breaks down fat and glycogen
stimulates bile flow
Pancreatic juices - contain enzymes to digest all three major kinds of food
Trypsin (protease) - breaks down protein, 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
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
Cardiac Region
Cardiac Sphincter :
one way valve connects from esophagus
to the stomach
-The opening of the esophagus into the stomach
acid from the stomach goes into the esophagus
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
Pepsin (enzyme) begins breaking down proteins into peptides
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
a mixture of mucus, HCl, and enyzmes
semi-fluid 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 mucus; it mixes the chewed food with saliva
salivary amylase
: an enzyme that begins the digestion of polysaccharides (starches) into maltose (disaccharide)
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; smallest of the salivary glands, secretes mainly mucus.
stomach growling:
: largest gland; situated along the cheek and jawline in front of each ear between the skin of the cheek and the masseter muscle; produces a serous, watery secretion rich in amylase.
Food in stomach = quieter growling
-process of peristalsis turning food into chyme
-hormones stimulated to send nerves to the brain
-time span of 2-4 hours
-peristalsis starts again churning the contents
Small Intestine Structure
Function of Small Intestine
Disorders and Diseases
Structure of Large intestine*
Function of Large Intestine
Disorders and Diseases
Consists of:
Ascending, Transverse, Descending, Sigmoid


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
Villi (villus)
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 villus
- glycerol and fatty acids are joined and packaged as lipoproteins before entering lacteals (lymphatic vessels in the villa that serve to absorb fat)
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 on the floor of the mouth on the inside surface of the jaw; the secretion is a mixture of serous and mucus
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 colon
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
- caused by inflammation of, and damage to the small intestine due to having too much of certain types of bacteria in the intestines.
*Has a surface area
the size of a tennis court
Does it have a function?
Storage of good bacteria to replace bacteria purged after cholera or dysentery
: inflammation as a result of stool or cancer, blockage of appendiceal lumen
Removal of appendix has no adverse affects
the act of swallowing takes place here
: closes off the trachea so that food does not go to the lungs
Esophagus Function
Disorders and Diseases
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 cardiac sphincter
-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)
sometimes caused by Helicobacter pylori infection or diet
- bacteria and viruses increase the amount of liquid
secreted in the stomach and makes it flow too quickly
-Gastritis is an inflammation,
irritation, or erosion of the lining of the stomach. It can occur suddenly
(acute) or gradually (chronic)
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 resemble the intestine
esophageal cancer
gastroesophageal reflex disease
acidic stomach contents back up into the esophagus, causing irritation and heartburn
Disease and Disorders in the Salivary gland
Increase in Surface Area = Increase in Substrates = Increase in enzymatic reactions
Why do we burp??
Sometimes the stomach becomes filled
with swallowed air.
Cardiac Orifice :
the trumpet-shaped opening of the esophagus into the stomach
Full transcript