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What is the main purpose of the digestive system?
It provides the fuel for bodys cells and also provides the building blocks for cell growth and cell repair
What is the basic/foundational structure of the digestive system?
It is a continuous tube/ digestive tract also known as the gastrointestinal tract.
What is the digestive system divided into
Main organs and acessory organs
What are the main organs of the digestive system
The oral cavity
The Pharynx
Stomach
Small Intestine
Large Intestine
Anus
What are the acessory organs
Teeth
Tongue
Salivary Glands
Liver
Pancreas
Gallbladder
Where is the digestive tract located
In the abdominopelvic cavity covered by a peritoneum which is a serous membrane
What secures and stabilizes the digestive organs in the abdominopelvic cavity?
Mesentries or Mesentry proper
What are the 4 layers of the digestive tract wall
Mucosa
Submucosa
Muscle Layer
Serosa
What does the Mucosa layer of the digestive tract wall include
Epithelum
Connective Tissue or Lamina Propria
A Muscle layer that is a narrow sheet of smooth muscle and elastic fibers
What does the Submucosa layer in the digestive tract wall consist of?
A layer of dense irregular connective tissue that binds mucosa to muscle layer. It ahs a network of nerve fibers and neurons known as Submucosal neural plexus
What type of feeling is the submucosal neural plexus responsible for?
The gut brain connection where we get gut feelings about something
What does the muscle layer of the digestive tract wall include
Inner circular layer
Outer longitudinal layer
What is Peristalsis and where does it occur
It is the contraction of inner circular layer and outer longitudinal layer that squeezes and pushes contents forward in the muscular layer of the digestive tract
What is a bolus
Soft rounded ball of digestive contents like food
What are the acessory organs of the oral cavity
Teeth, tounge, salivary glands
What are the functions of the oral cavity
Sense food before swallowing
Mechanical digestion through chewing which touches all the accessory organs in the mouth and allows brain to recognize it is food
Mucus and saliva are mixted
Limited digestion
What is a Uvula and why is it important
It is a fleshy hanging piece at the back of the throat and it stops entry of food in the nose
What are the 3 major salivary glands
Parotid Gland
Sublingual gland
Submandibular Gland
What is the function of each salivary gland
Parotid gland secrets amylase which breaks down starches
Sublingual glands produce mucus
Submandibular glands sectete buffers and glycoproteins called musins
What are the 3 enzymes of the salivary glands?
Salivary amylase
Lingial Lipase= breaks down lipids
Lysosome=kills bacteria by destroying cell walls
What does the pharynx do and how does it do it?
It is a major organ and the passageway for food and the food passes down the oropharynx and laryngopharynx into the esophagus
What is the esophagus and what does it do?
Its a tube that the food goes down through and it rests and contracts in order to not let air into the stomach and prevents backflow of content from the stomach
What does deglutition mean
Swallowing
What are the 3 phases of swallowing
Buccal Phase
Pharyngeal Phase
Esophogeal Phase
What happens during the buccal phase?
It is intiated voluntary an the information is relayed to brain. In this phase the bolus is compressed then goes into oropharynx and seals off nasopharync
What happens in the pharyngeal phase
The bolus goes from the oral cavity to the pharynx where the epiglottis gets folded and food goes past the closed glottis. Uvula keeps blocking nasopharynx
How does the epiglottis work?
It is like a gate and as the bolus comes down it folds down to let the food go down through the esophogus
What happens in the esophageal phase?
While the food is in the esophagus peristasis occurs and bolus is moved toward the stomach
What is the end of the swallowing process
The bolus enters the stomach
Explain what the stomach does and its structure
The stomach is a J shape and it is a food tank that temporarily stores food but it forms chyme which is semifluid food mixed with acidic secretions of stomach.
What are the 4 parts of the stomach
Fundus
Body
Cardia
Rugae
What is a special part of the mucosa in the stomach wall
The gastric pit which has gastric glands that secrete mucous and enzymes
How is the muscular layer of the stomach wall different?
It has 3 layers of muscle with an additional oblique muscle because it needs enough muscle to mix and churn everything.
What type of lining is in the stomach
Simple columnar epithelium
What are the 3 types of cells in the Gastric Glands
Parietal
G
Chief Cells
What do G cells do?
They are an enteroendocrine cell that produce gastrin that enters the circulation
What do Parietal Cells do
Secrete a glycoprotein that helps absorb vitamin B12 and H+
What do chief cells do?
They secrete pepsinogen which is a proenzyme that is converted to pepsin
What is the only thing that is absorbed by the stomach
Alcohol
What is the cephalic phase
It starts when you smell, taste or think of food and is directed by the central nervous system who prepares stomach to receive food.
What is the gastric phase
This begins when food arrives to the stomach where food secretes gastric juice and mixes food into chyme
What is the intestinal phase
Chyme enters the small intestine but there will be crosstalk between small intestine and stomach. Small intestine needs to neutralize the chyme so it will tell stomach to slow its contractions and it will listen
What happens in the small intestine
Digested food is absorbed
What are the 3 parts of the small intestine
Duodenum
Jejunum
Ileum
What does the duodenum do?
It is the shortest part and it receives chyme and neutralizes chyme
What does the jejunum do
Chemical digestion and nutrient absorption happens here
What does the ileum do
This is the final and longest part where there is a ileocecal valve which is a sphincter that control material into the cecum or the first part of the large intestine
What happens in the large intestine
Stores digestive wastes and reabsorbs water
What are the 3 parts of the large intestine
Cecum
Colon
Rectum
What is the pancreas and what does it do
It is a accessory organ that has an exocrine portion and endocrine portion
Exocrine portion= produces digestive enzymes
Endocrine portion= secretes hormones
What does the liver do
It is an endocrine organ that has hepatocytes and secretes plasma proteins and secrete bile that is stored in the gallbaldder.
What is the hepatic triad
Portal vein, bile duct and hepatic artery
What does the hepatic vein carry
Good blood
What does the portal vein carry
All blood carrying absorbed blood
Central vein
Collects detoxified blood with low oxygen