Gastrointestinal SystemImari Attaway, Olivia DiCapua Riley Dinneen, Stephanie Tyrrell
GI Tract: Mouth
Salivary glands
Pharynx and Esophagus
Stomach
Pancreas
Liver
Small intestine
Large intestine
GI System
Digestive system
Mechanical and chemical breakdown of food into smaller components that allow it to be absorbed into the blood stream.
Mouth
Two types of digestion: 1. Chemical 2. Mechanical
Mechanical=Chewing and swallowing
Chemical=Salivary Glands
Salivary Glands
Located under tongue and near lower jaw
Once mouth is chewing salvia gets released from glands and begins breaking down food.
Moistens food
Enzymes
Amylase: A digestive enzyme in the saliva that breaks down carbohydrates.
PharynxConnects nasal and oral cavities with the larynx and esophagus.
Aides in swallowing.
3 structures:
1. Nasopharynx
2. Oropharynx
3. Larynopharynx
Esophagus25 centimeter long passageway for food. Pharynx --> stomach.
Along the esophagus are mucus glands which moisten passageway. (food goes smoothly)
Lower esophageal sphincter: area above where esophagus meets stomach. Contains smooth muscle fibers which can contract to close the entrance of the stomach and prevent food from going back into esophagus.
Stomach
A j-shaped pouch-like organ
Hangs inferior to the diaphragm in upper left portion of abdominal cavity.
capacity=1liter+
Receives food from esophagus>mixes with gastric juice>initiates digestion>carries on absorption>moves into small intestine
Parts of Stomach
Divided into 4 regions:
cardiac
fundus
body
pyloric
Stomach SecretionsMucous membrane of stomach is thick, studded with many small openings called gastric pits that are at the ends of tubular gastric glands.
Gastric glands generally have 3 types of secretory cells:
Mucous Cells- in the necks of the glands near the openings of the gastric pits
Chief Cells- in the deeper part of the glands, secrete digestive enzymes
Parietal Cells- in the deeper part of the glands, cellsrelease hydrochloric acid.
Together they form Gastric Juice.
Components of gastric juice:
Component Source Function
Pepsinogen Chief cells of the gastric glands Inactive for of pepsin
Pepsin Formed from pepsinogen in the presence of hydrochloric acid
A protein-splitting enzyme that digests nearly all types of dietary protein
Hydrochloric Acid Parietal cells of the gastric glands
Provides the acid eniviornment needed for the conversion of pepsinogen into pepsin and for the action of pepsin
Mucus Mucous Cells Provides a viscous, alkaline protective layer on the inside stomach wall
Intrinsic Factor Parietal cells of the gastric glands
Aids in vitamin B12 absorption
PancreasExtends horizontally across the posterior abdominal wall in the C-shaped curve of the duodenum
Pancreatic Actinar-cells that produce pancreatic juice, make up the bulk of the pancreas.
Smaller tubes unite to form larger ones, Panceratic duct, extending the length of the pancreas.
Hepatopancreatic spincher- controls movement of pancreatic juices into the duodenum(the first segment of the small intestine).
Makes insulin, secreting it directly into the bloodstream.
Insulin is the chief hormone for metabolizing sugar.
Liver (anatomy)
Reddish-Brown color-well supplied by blood vessels.
Covered by fibrous capsule and connective tissue
Divided into two lobes (large right lobe and small left lobe.)
Hepatic lobes: Each of the two lobes are separated into many smaller ones. These are the functional units of the liver.
Gallbladder: pear-shaped sac off the liver that store bile in between meals.
Liver (physiology)Breaks down food
Stores important substances
Contains Macrophages
Help lipid metabolism (food-->fats):
Converts portions of carbs and protein molecules into fat molecules
oxidizes fatty acids
Synthesizes lipoproteins.
Helps protein metabolism (food -->protein): synthesizing plasma proteins and converting certain amino acids to other amino acids.
Small intestine
Tubular organ
Runs between stomach and large intestine
Fills most of abdominal cavity
Made up of 3 parts:
Duodenum-25cm
Jejunum-2/5 of peritoneal cavity
Ileum-remainder of peritoneal cavity
Small intestine (cont.)Wall of the small intestine:
Lined with villi (part of mucus membrane)-increase surface area and aid in mixing and absorption
Intestinal gland-located between villi
Secretions and Absorptions:
Mucus secreting goblet cells
Digestive enzymes (peptidases, sucrase, maltase, and lactase)
Movement:
Segmentation (major mixing)
Peristalsis (when irritated)
Large intestine
Begins in lower right side of abdominal cavity
1.5 meters long
4 parts:
Cecum
Colon
Rectum
Anal cord
Large intestine (cont.)Large intestine wall:
similar to other walls in alimentary canal
unique layer of longitudinal, banded muscle fibers
Functions:
secretes mucus
absorbs water and electrolytes
forms and stores feces
Movement:
similar to small intestine
mass movements 2-3 times a day
defecation reflex: stimulates waste elimination
Diseases and Disorders involved
Crohns disease (aka iletis or enteritis)
what is it- inflammation of any area of the digestive tract. Most commonly affects the lower part of the small intestine
causes- pain, empties intestines resulting in diarrhea
most common age is 20-30
Jewish have increased risk-Blacks have decreased
Symptoms-pain, diarrhea
Diagnosis-thorough physical exam and a series of tests
Treatment- drugs, nutrition supplements and/or surgery
Diseases and Disorders (cont.)
Appendicitis
what it is- an irritation, inflammation, and infection of the appendix. occurs when inside becomes filled with mucus, stool, or parasites (causes swelling)
causes- pain, no purpose but if goes untreated it can burst and lead to infection
symptoms- stomach ache on right side
diagnosis-blood and urine test
most occur between ages 10 and 30
treatment: removal
Diseases andDisorders (cont.)lactose intolerance
what it is-the body’s inability to break down lactose (sugar found in milk)
causes pain, digestive diseases, injury to small intestine
symptoms-pain 30min-2hrs after eating, diarrhea, bloating, gas
diagnoses- lactose intolerance test
treatment- diet, oral pill
