Also called the digestive tract or gastrointestinal (GI) tract; consist of an alimentary canal and accessary glands.
Basic pathway of the diestive system:
Mouth: oral cavity, tongue ==> pharynx ==> esophagus ==> stomach ==> small intestine ==> large intestine/colon ==> rectum ==> anus
Secrete digestive enzymes into the canal: salivary glands, pancreas, liver.
How long does it take the body to digest food?
Total digestive process takes 12 - 24 hours
What are the four stages of food precessing?
Where are the hard & soft palates and gingivae located in the oral cavity?
The portion of the oral cavity on one side by the teeth and gingivae and on the other side by the lips (labial vestibule) and cheeks (buccal vestibule).
Posterior portion of soft palate
Skeletal muscle, manipulates food into a "bolus"
On upper surface contain taste buds (with chemoreceptors).
What condition can result at the lingual frenulum?
If too short, can cause speech porblems.
Produce saliva to clean mouth an teeth and moisten bolus (begins chemical digestion)
On lateral side of face, anterior to ear, enters oral cavity at approximately 2nd upper molar.
8 - 20 ducts empty saliva into the floor of mouth
On medial surface of mandible, empty on either side of the lingual frenulum.
Chew food to continue breakbown
- Pulp Cavity
- Root Canal
What are the types of teeths?
- Incisors -- front cutting teeth
- Cuspids – conical, tearing teeth (canines)
- Bicuspids – crushing, grinding teeth (2 roots)
- Molars – 3 or more roots – also crush and grind
What is the dental succession?
- First, it is 20 deciduous (baby) teeth
- Then, 32 permenant (adult) teeth
What are the dental references?
- Labial/Buccal Side
- Lingual/Palatal Side
- Mesial Side
- Distal Side
- Occlusal Surface
Pharynx (Digestion Specific)
Connects oral cavity to esophagus; involved in swallowing.
What happens to food or liquid in pharynx?
When food or liquid enters the pharynx, a reflex causes the larynx to rise, the glottis to close, and the epiglottis to flip down over the glottis.
Material is forced into the esophagus (tube posterior to the trachea that connects the pharynx to the stomach).
What are the layers of the digestive tract?
Serosa - outside layer of CT and peritoneum
Muscularis - muscular layer
Submucosa - CT with glands, nerves, and blood vessels
Mucosa - innermost layer, faces lumen (open space)
- Made of epithelium, CT, and muscle.
First segment of the digestive tract/tube
About 10 inches long
Brings bolus to stomach
Has 2 sphincters (muscles that close tubes)
- Lower esophageal/cardiac/gastroesophageal
Rhythmic contraction of digestive tubes
Begins in esophagus, continues through the entire tract, pushing bolus along
Controlled voluntarily in top 1/3 of esophagus, slightly voluntary in middle 1/3, and completely involuntary after that.
Irritation in stomach or small intestine can reverse a peristalsis.
Due to reflux - acid from stomach moves into the esophagus, irritating the mucosa
- Weakened Lower Esophageal Sphincter
- Hiatal Hernia
- Increased Pressure
The superior part of the stomach pushes through an enlarged esophageal hiatus into the thorax following a weakening of the diaphragmatic muscle fibers around the hiatus.
- No cardiac sphincter reinforcement = regurgitation of acid.
What are the regions of the stomach?
- Lesser Curvature
- Greater Curvature
- Polyric Sphincter
- Greater Omemtum
- Polyric Sphincter
What is the musculature of the stomach?
Outer layer - longitudinal
Middle Layer - circular
Inner Layer - oblique
What occurs to the food inside the stomach?
Layers of muscle churn bolus to break it down mechanically
Also chemical breakdown:
- Millions of digestive glands line the stomach - produce pepsin and HCl to aid in digestion and break down bacteria.
Caused when the HCl breaks down the stomach mucosa; usually caused by bacteria.
Hole in lining of stomach is produced
Treated with medication
When a bolus is mixed pepsin and HCl, it becomes chyme; a pasty, semisolid, acidic mixture
Exits stomach after about 2 - 6 hours; passes through the polyric sphincter into the duodenum (first portion of small intestine).
10 foot long, small diameter tube between the stomach and large intestine.
Breaks chyme into small molecules, absorbs nutrients, and transports undigested material to the large intestine; contains numerous of villi.
Millions of tiny finger-like projections on the mucosa (on plicae circulares) of the small intestine
- Increases surface area for nutrient absorption
What are the 3 segments of the small intestine?
Duodenum ==> jejunum ==> ileum
About 10 - 12" long, receives bile to emulsify fat; duodenum also receives pancreatic secretions - enzymes for digestion.
An emulsifying agent that is made by the liver and stored in the gallbladder.
Breaks fat into small particles so it can mix with enzymes and water.
About 2 - 3' long, further digests and absorbs food molecules.
About 4 - 6' long, further digests and absorbs food molecules; ends at the ileocecal valve - between ileum (end of small intestine) and cecum (beginning of large intestine).
Large diameter tube, about 5' long; composed of cecum, colon, rectum, and anal canal.
Absorbs water and electrolytes and prepares and stores undigestible material (feces).
Baglike section, has wormlike appendage called the vermiform appendix.
What are the segments of the colon?
- Ascending Colon
- Tranverse Colon
- Descending Colon
- Sigmoid Colon
6 - 7" long, has 3 folds to support fecal material.
Goes through body wall to exterior; ends in anus (anal sphincter) for defecation.
Dilated veins in anal canal that result from irritation of mucosa or pressure from pregnancy or hard stools.
Symptoms - itching, blood stools
Treatment - high fiber, high liquid diet, topical creams.
Infected and swollen appendix
Too much water is left in the intestine (to rid body of bacteria) or nervous stimulation due to stress.
Too much water is absorbed in the intestine, leaving dry, hard stools.
The development of diverticula (sac-like appendages in the walls of the large intestine).
Diverticulitis - inflammed diverticula
Thought to be caused by a low fiber diet
Usually symptom-free. Some individuals experience cramping, abdominal pain (esp. on lower left side), bloating, and constipation.
Mild cases treated with a higher fiber diet and pain medications. Serious cases may require surgery.
Growths from epithelial tissue of mucosa of intestine; can be cancerous.
If lower part of rectum and anal canal is removed, an artificial opening in the abdominal wall can be surgically formed - fecal materical is collected in a bag attached to the opening.
What classifies something as an acessory organ?
Contribute to digestion, but are not part of the alimentary canal.
A mixed gland because it has endocrine and exocrine functions:
- Endocrine glands - secrete substances directly into blood (ductless) - insulin/glucagon.
- Exocrine glands - secrete substances through ducts.
What are the functions of the organs secreted by endocrine?
- Secretes glucagon to increase blood glucose
- Secretes insulin to decrease blood glucose
What are the exocrine secretions of the pancreas?
Secretes pancreatic juice (digestive enzymes):
- Lipase - digests fats
- Amylase - digest carbohydrates
- Trypsin - digests proteins
Results from a blocked duct
Usually fatal because there are no symptoms until the cells have metastasized.
Largest gland of the body; located in mainly the URQ of abdomen
2 main lobes:
- Left lobe has 3 parts
- Right lobe has 1 part
What is the function of the liver?
Blood that has absorbed nutrients from the small intestine passes through the liver.
It performs multiple processes and then the blood continues through the rest of the body.
What are the processes that the blood undergoes at the liver before continuing and the other functions of the liver?
- Stores glucose as glycogen
- Breaks down amino acids from proteins
- Destroys old RBC's
- Produces Bile
- Removes toxins form the blood
- Stores Vitamins A, D, E, K
The liver breaks down hemoglobin and old cell pieces that pass through the blood
- These wastes are used by the liver to form bile
- Contains high amounts of cholesterol
- Is sent to the gallbladder to be stored.
Describe the circulation of blood through the liver...
Scar tissue replaces normal healthy tissue, blocking blood flow through the organ and preventing it from working as it should.
Usually caused by alcoholism or hepatitis C
Symptoms include nausea, weakness, weight loss, and exhaustion
Liver damage cannot be reversed.
- Located on the undersurface of the liver
- About 3 - 4 inches long
- Stores bile
- Squirts bile into small intestine
Bile emulsifies in the small intestine so lipase can work on small particles of fat and digest them.
Yellowing of skin, conjunctiva, and mucous membranes due to deposits of bilirubin (from breakdown of RBC's).
Bilirubin is toxic to the nervous system, causing neural damage if too much accumulates.
Bile ducts are obstructed (by gall stones) so bile cannot drain out of the liver and overflows into the blood.
From RBC's being broken down in large quantities.
Immature liver cannot excrete the bilirubin as quickly as it is being formed.
What is the demographics and treatment of physiologic jaundice?
Commonly occurs in newborns
UV light treatments convert bilirubin in the skin to harmless molecules.
In the U.S., 30% of the population is obese/overweight
Can lead to other health problems such as diabetes, colon cancer, breast cancer, and cardiovascular disease.