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Anatomy Digestive System


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What are the 2 primary goals of the digestive system?
1. Obtain nutrients from ingested food 2. Eliminate solid waste
What are the 5 processes of the digestive system?
1. Ingestion 2. Digestion 3. Absorption 4. Metabolism 5. Defecation
What is ingestion?
The physical process of comsumption
What is digestion?
The breaking down of food particles. There is mechanical and chemical digestion.
What consists of Mechanical digestion?
1. Mouth. Mastication = chewing 2. Stomach and intestines. Smooth muscle contractions = GI motility (swirl, mix, and churn food after swallowing)
What is chemical digestion?
The break down of nutrients (proteins, fats, and lipids) by enzymes.
What is the enzyme found in the mouth?
Amylase (in saliva)
What are the enzymes found in the stomach?
Trypsin, Gastrin, and Pepsin.
What are the enzymes in the intestines?
There are numerous enzymes, don\'t need to know specific ones.
What is absorption?
Movement of nutrients, etc., across the digestive epithelium and into the interstitial fluid of the GI tract (entering body).
What are the enterocytes of the intestines?
They are the intestinal absorptive cells---simple columnar epithelial cells---of intestines.
True or False. Once digested food is in the GI tract lumen, it is considered to be inside the body.
False. The substances don\'t enter the internal environment (body) until they are absorbed.
What is metabolism?
The processing of absorbed food materials.
What is a major organ of metabolism?
The liver. It is the major processing organ of the body. It is an accessory organ.
What is defection?
The elimination of any undigested material which contains NO nutrients.
What is the responsible organ of defecation?
The terminal colon.
What are some things that are secreted from defecation?
Undigested foodstuffs, secretions from accessory glands (some bile, sloughed epithelial cells), some water and bacteria.
What is the gastrointestinal tract?
aka GI tract or alimentary canal. A hollow tube that runs from the oral cavity (mouth and lips) through the ventral body cavities, to the anal orifice. It is lined by epithelial tissue
What are some of the accessory organs that facilitate digestion?
Teeth, tongue, salivary glands, liver, gallbladder, and pancreas.
What are the four layers of the GI tract?
1. Mucosa 2. Submucosa 3. Muscularis Externa 4. Serosa
What does the mucosa line in the GI tract, and how many layers is it composed of?
It is the lining of the lumen (the inner, open space of a hallow organ) It is composed of 3 layers. - epithelial cells - areolar connective tissue -smooth muscle It contains lymphatic tissue
Where in the GI tract is there simple or stratified epithelial tissue?
oral cavity and esophagus are lined by stratified squamous epithelium that can resist stress and abrasion
What parts of the GI tract contain simple columnar epithelium?
The stomach, small intestine, and almost the entire large intestine. It is specialized for secretion and absorption.
True or False. The submucosa is composed of highly vasularized connective tissue.
What are some of the important things the submucosa contain? (3)
1. Contains the submucosal enteric neural plexus that controls GI secretion. (PARAsympathetic ganglia and POSTsympathetic fibers that innervates the mucosa) 2. Contains many glands which open into the lumen by way of ducts 3. Contains lymphatic tissue
Why would it be important for the digestive tract to be particularly rich in lymphatic tissue?
Transport materials that cannot enter local capillaries The material, such as large lipid-protein complexes, ultimately reach the venous circulation by way of the thoracic duct. (lacteals are present)
What are Lacteals?
Terminal lymphatics that absorb digested fats from small intestine
What are the two tissue types the Muscularis Externa contains?
1. Skeletal muscle tissue 2. Smooth muscle tissue
True or False. Skeletal Muscle tissue is under voluntary motor control.
Where is the skeletal mm tissue found in the GI tract?
In the mouth, pharynx, upper esophagus, and lower portion of the anal canal
What are the two layers of smooth mm tissue?
1. Circular 2. Longitudinal
What does circular smooth mm do?
It is the inner layer, and the contractions produce changes in diameter of segment
What does longitudinal smooth mm do?
It is the outer layer, and the contractions produce changes in length of segment.
Why is smooth mm so important to the GI tract?
It is essential to mechanical processing and the propulsion of materials along the GI tract.
True or False. The stomach has 2 layers of smooth mm tissue.
False. The stomach has three layers.
The Muscularis Externa contains the portion of the enteric neural plexus responsible for GI motility. What is the part of the plexus called, and what does it do, etc.?
Myenteric Plexus: --b/w circular and longitudinal layer --both Parasypm and sypm network --controls movement of GI tract (motility) --forms sphincters and valves in various locations
What is another name for the serosa layer?
It is also known as the visceral peritoneum.
The serous membrane is composed of two layers, what are they?
1. A layer of connective tissue and 2. A layer of simple squamous epithelium.
What does the Serosa secrete?
It secretes serous peritoneal fluid (a lubricant that reduces friction)
What is the Serosa? (Where is it located?)
It is a superficial layer of the viscera (organs) located in the adbominopelvic cavity.
Where is the Serosa layer absent?
In the oral cavity, pharynx, esophagus, and the rectum. --Any areas of skeletal muscle--

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