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Our system involves…the intake and
digestion of food, absorption of nutrients, and elimination of solid waste.
What is our system?
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Gastro-Intestinal System
Alexandra Ford, Jenna Volpe, Alexa Mastriano and Alexis
Tomaszewski
Functions of the GI System
Digestion
Produces various chemicals to break down food molecules
Filters out harmful substances
Removes solid waste
What is Digestion?
The chemical breakdown of complex biological molecules into their component parts
The breakdown involves… Lipids – Fatty Acids Proteins – Amino Acids Carbohydrates- Simple Sugars
5 Stages of Digestion
1. Ingestion2. Movement3. Mechanical and Chemical
Digestion4. Absorption5. Elimination
Two Different Types of Digestion….
Mechanical Digestion
Chemical Digestion
What do you think the difference is?
Mechanical Digestion
Changes the physical form of food
EXAMPLES Chewing Tearing Grinding Mashing Mixing
Chemical Digestion
Changes the chemical composition of food with the aid of digestive enzymes
EXAMPLES Carbohydrates Proteins Lipids
GI Tract
Parts of the GI Tract
– Tube within a tube– Direct link/path between organs
Structures• Pharynx• Esophagus• Stomach• Small intestine• Large Intestine• Rectum
Pharynx
Connects the nasal and oral cavities with the larynx and esophagus
There are 3 parts to the pharynx:o nasopharynxo oropharynxo laryngopharynx
Parts of the Pharynx
Nasopharynxo provides a passageway for air when breathing
Oropharynxo passageway for food to move from the mouth,
and for air to move to and from the nasal cavity
Laryngopharynxo provides a passageway to the esophagus
Esophagus
Approximately 10” long
Functions include:
1. Secrete mucus
2. Moves food from the throat to the stomach using muscle movement called peristalsis
If acid from the stomach gets in here that’s heartburn.
Stomach
J-shaped muscular bag that stores the food you eat, breaks it down into tiny pieces.
Mixes food with digestive juices that contain enzymes to break down proteins and lipids.
Acid in the stomach kills bacteria.
Food found in the stomach is called chyme.
Stomach
The stomach is divided into the fundus (upper, rounded
part), body (main portion), and antrum (lower part).
Rugae- the folds in the mucosa lining the stomach.
Gastric Secretions: Thick mucus membrane forms the inner lining of stomach ,
studded with small openings (gastric pits) that are at the ends of gastric glands
-Gastric glands have 3 types of secretory cells; mucous, chief, and parietal
cells
o Chief secrete digestive enzymes
o Parietal release hydrochloric acid
o The digestive enzymes and the hydrochloric acid forms gastric juice.
Small Intestine
Small intestines are roughly 7 meters long
Lining of intestine walls has finger-like projections called villi, to increase surface area.
The villi are covered in microvilli which further increases surface area for absorption.
Small Intestine
Digestion in Small Intestine Produces:
1) disaccharides
2) fatty acids
3) peptidesmonoglycerides
Portions of the Small Intestine:
1) duodenum
2) jejunum
3) ileum
Small Intestine
Nutrients from the food pass into the bloodstream through the small intestine walls.
Absorbs: 80% ingested water Vitamins Minerals Carbohydrates Proteins Lipids
• Secretes digestive enzymes
Large Intestine
About 5 feet long
Accepts what small intestines don’t absorb
Rectum (short term storage which holds feces before it is expelled).
Large Intestine
Functions Bacterial digestion
Ferment carbohydrates Protein breakdown
Absorbs more water Concentrate wastes
Large Intestine
Movement
• Slower than in the small intestine. Peristaltic waves happen 2-3 times a day. Intestinal wall constricts vigorously and forces the intestinal contents toward the rectum.
• Defecation reflex: holding a deep breath and contracting the abdominal wall muscles increases internal abdominal pressure and forces feces into the rectum.
Feces from the Large Intestine
Feces
• Materials that were not absorbed or digested, and water (75%), electrolytes, mucus, and bacteria.
• Odor is from a variety of compounds that bacteria produces.
• Color is from pigments now altered by bacterialß action.
Accessory Organs
Include: Liver, gall bladder, and pancreas
Not part of the path of food, but play a critical role.
Liver
Directly affects digestion by producing bile Bile helps digest
fat filters out toxins
and waste including drugs and alcohol
Liver Functions
Carbohydrate metabolism- helps maintain concentration of blood glucose
Lipid metabolism-oxidizes fatty acids at a high rate, synthesizing lipoproteins, phospholipids, and cholesterol, and converting portions of carbohydrate and protein molecules into fat molecules
Protein metabolism-deaminated amino acids, synthesizing plasma proteins, and converting certain amino acids to other amino acids
Gall Bladder
Stores bile from the liver, releases it into the small intestine.
Fatty diets can cause gallstones
Gall Bladder Functions
Stores bile between meals, reabsorbs water to concentrate bile, and contracts to release bile into small intestine
Functions of Bile Salts
-Aid digestive enzymes
-Break down fat globules into smaller droplets (emulsification)
-Then they mix with water so the fat molecules can be digested more effectively
Pancreas
Produces digestive enzymes to digest fats, carbohydrates and proteins
Regulates blood sugar by producing insulin
Pancreas
Pancreatic Juice- Contains enzymes that digest carbohydrates, fats, nucleic acids, and proteins
Pancreatic amylase -splits molecules of starch or glycogen into double sugars
Pancreatic lipase- breaks triglyceride molecules to fatty acids and glycerol
-Two nucleases, which are enzymes, break down nucleic acid molecules into nucleotides
-Trypsin, chymotrypsin, and carboxypeptidase (protein splitting enzymes) split the bonds between certain amino acids in proteins
Oral Cavity
Mouth
Teeth mechanically break down food into small pieces. Tongue mixes food with saliva (contains amylase, which helps break down starch).
Epiglottis is a flap-like structure at the back of the throat that closes over the trachea preventing food from entering it.
Salivary Glands
2 types of secretory cells:o serous cells: produce a watery fluid that is rich
in proteins and glycoproteins as well as amylase (split starch and glycogen molecules into disaccharides)
o mucous cells: secrete a thick mucus which lubricates the food before it is swallowed
Salivation: occurs when one prepares to eat, and nerve signals activate salivary glands to moisten the mouth
The amount of saliva secreted depends on how appealing the particular food is to the individual
Three Types of Salivary Glands
Salivary Glands
partoids large secrete 25% of saliva (watery) front of ears extending to jaw bone (1 on each
side) drains into mouth near upper teeth
submandibular secrete 70% of saliva (mucus) drains into mouth from under tongue
sublingual smallest secrete 5% of saliva (mucus) drains into floor of mouth
Lips and Cheeks
LIPS sensory receptors and provide information
about food before its in the mouth few differences between lips and skin on
bodyo no sebaceous glands- keep moisturized with
salivao no hair follicles
Cheeks
Does anyone remember the scientific name for cheeks?
-stratified squamous epithelium
-inside of cheek is lined by mucous membrane
Tongue
guides and molds food in the mouth
composed of skeletal muscle fibers (willingly controlled)
mucous membrane protects it from microbes and pathogens
lingual frenulum connects tongue to floor of mouth
perceives taste and texture
over 10,000 taste buds (change with age)
Palate
o forms the roof of the oral cavity and consists of a bony anterior part and a muscular posterior part
o palatine tonsils- two lymphatic tissue masses, located on either side of the pharynxo help protect the body against infection
(respiratory)
Fun Facts
HOW LONG ARE YOUR INTESTINES? At least 25 feet in an adult. Be glad you're not a full-grown horse -- their coiled-up intestines are 89 feet long!
Food drying up and hanging out in the large intestine can last 18 hours to 2 days!
In your lifetime, your digestive system may handle about 50 tons!!
On a sheet of paper, write the name of each colored organ:
Green:
Red:
Pink:
Brown:
Purple:
Green:
Yellow:
How’d you do?
Green: Esophagus
Red: Stomach
Pink: Small Intestine
Brown: Large Intestine
Purple: Liver
Green: Gall Bladder
Yellow: Pancreas