314151 Lecture Notes - Lecture 2: Enteric Nervous System, Semipermeable Membrane, Mastication

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Active lifestyle:
Being active and performing some sort of physical activity for over 150 minutes a week.
Health:
The state of being in complete physical, mental and social well being. It is not the absence of illness or disease.
Lecture 2 8/3/16
Career Paths
Lecture 3 15/3/16
The Digestive System
The digestive tract is a tube that runs from the mouth to the anus. It has accessory organs (glands that secrete
fluids into the canal) that help break down foods.
Food goes in the oral cavity (mouth), down the pharynx and esophagus, into the stomach where it goes to the
small intestine (where the accessory organs are), the large intestine and then through to the anus.
Functions of the digestive system
1. Ingestion the introduction of food to the oral cavity.
2. Mastication food is mechanically broken down to increase surface area so enzymes can start
chemical digestion.
3. Propulsion the movement of food through the digestive system.
Swallowing moves the bolus from oral cavity to the esophagus.
Peristalsis wave of smooth muscle contracting behind the bolus to propel forward and then
the relaxation of smooth muscle in front of the bolus.
Mass movements contractions that move material in the large intestine.
4. Mixing food is mixed with digestion secretions to help with the break down of the food into smaller
parts.
5. Secretion purpose is to break down the food. Mucus covers the entire digestive tract to help
lubricate. It also coats the stomach, esophagus and intestine to protect the epithelial cells from the
stomach acid. Enzymes secreted from the pancreas, small intestine and stomach break down the
food.
6. Digestion Mechanical (mastication) and chemical (enzymes) digestion.
7. Absorption Molecules move out of the digestive tract into the circulatory or lymphatic system.
Movement is achieved through diffusion (movement of air from high-low pressure), osmosis
(movement of water across a semi-permeable membrane), facilitated diffusion (molecules combine
with a carrier protein and cross the membrane), active transport pumped across ,
endocytosis (plasma membrane wraps around the molecule and carries it away) or
(waste products are eliminated from the body via. Defecation.
The main aim of the digestive system is to break down foods to smaller molecules that can be absorbed into
the circulatory system.
Histology of the digestive tract
There are 4 layers:
1. Mucosa inner most layer that secretes mucous.
2. Submucosa nerves, lymphatic, blood vessels and small glands.
3. Musculairs smooth muscle two circular layers and a longitudinal layer.
4. Serosa smooth layer that covers the digestive tract.
Regulation of the digestive system
Nervous Regulation
- Enteric nervous system (ENS) is within the wall of the digestive tract. It controls blood flow and
propulsions
Chemical Regulation
- Neurotransmitters - Acetylcholine stimulates and norepinephrine inhibits digestive secretion and
movement.
- Hormones Endocrine secretions serotonin, gastrin, secretin.
- Paracrine secretions histamine.
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Document Summary

Being active and performing some sort of physical activity for over 150 minutes a week. The state of being in complete physical, mental and social well being. It is not the absence of illness or disease. The digestive tract is a tube that runs from the mouth to the anus. It has accessory organs (glands that secrete fluids into the canal) that help break down foods. Food goes in the oral cavity (mouth), down the pharynx and esophagus, into the stomach where it goes to the small intestine (where the accessory organs are), the large intestine and then through to the anus. Ingestion the introduction of food to the oral cavity: mastication food is mechanically broken down to increase surface area so enzymes can start chemical digestion, propulsion the movement of food through the digestive system. Swallowing moves the bolus from oral cavity to the esophagus.

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