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Digestive System (The organs that produce digestive hormones and their…
Digestive System
Pathway of food through the digestive tract
the process of swallowing and involves moving food from the mouth to the stomach. Consist of three phases:
Voluntary phase- phase where you have conscious control and push the food to the back of the throat or the oropharynx.
Deglutition:
Pharyngeal phase- involuntary. Nerve receptors trigger the uvula and soft plate to lift up closing off the nasopharynx and sending waves of contractions down through the laryngopharynx. Upper esophageal sphincter is relaxed so food can move into the esophagus.
Esophageal phase- also involuntary. Peristalsis moves food down to the lower esophageal sphincter. When the bolus of food gets down to the lower end of the esophagus, the lower esophageal sphincter relaxes allowing food to enter the stomach.
Mechanical and Chemical digestion
Mechanical
the physical breaking down of foods that occurs in the mouth and the stomach
Chemical
Uses chemicals to breakdown large macromolecules into smaller molecules for absorption.
It begins in the mouth with saliva, continues in the stomach with hydrochloric acid and enzymes. Most of the chemical digestion occurs in the small intestine. Enzymes are the source for the majority of this breakdown.
General function of the digestive system
Absorption
digestive tract allows movement of small, diffusible molecules into the bloodstream so they can enter the cells.
Enzymes are produced by many cells in the organs and accessory organs of the digestive tract.
Enzymatic hydrolysis
the breakdown of food particles by chemical action of enzymes.
In the stomach is the movement from the muscles which help to churn the food into even smaller bits to allow easier digestion by enzymes.
Mechanical breakdown of food
where food is moved around by the tongue and broken up into smaller pieces by the teeth.
Gross and microscopic anatomy of the accessory organs
The gallbladder primarily stores, concentrates, and releases bile.
The pancreas produces pancreatic juice, which contains digestive enzymes and bicarbonate ions, and delivers it to the duodenum.
The digestive role of the liver is to produce bile and export it to the duodenum.
Chemical digestion in the small intestine cannot occur without the liver and pancreas. The liver produces bile and delivers it to the common hepatic duct. Bile contains bile salts and phospholipids, which emulsify large lipid globules into tiny lipid droplets, a necessary step in lipid digestion and absorption. The gallbladder stores and concentrates bile, releasing it when it is needed by the small intestine.
The pancreas produces the enzyme a bicarbonate-rich pancreatic juice. Delivers it to the small intestine through ducts. Pancreatic juice buffers the acidic gastric juice in chyme, inactivates pepsin from the stomach, and enables the optimal functioning of digestive enzymes in the small intestine.
Accessory organs: the liver, pancreas, and gallbladder
The organs that produce digestive hormones and their role
Cholecystokinin (CCK)
- hormone produced by the enteroendocrine cells. Stimulates the pancreas to secrete enzymes into the duodenum and stimulates the gallbladder to empty.
a hormone produced in the stomach by G cells. Helps stimulate acid secretion which helps to move things along.
Secretin:
produced by the enteroendocrine cells it stimulates the pancreas to release a digestive juice rich in bicarbonate. Bicarbonate is release inro the duodenum and helps to decrease the acidity of the acid chyme from the stomach.
The small intestine doesn't have mucoid lining to protect it form acid destruction. Its function id for absorption. Also stimulates the stomach to produce pepsin when this is not released the stomach stops producing this enzyme.
Gastrin:
Describe Peritoneum and Mesenteries
Mesentery- the mesenteries is connective tissue that holds the small intestine in numerous folds in the abdomen.
Peritoneum lines the entire abdominal cavity. Made up of two layers of connective tissue: parietal peritoneum and visceral peritoneum.
Mesocolon- layer helps to hold the large intestine in place
Falciform ligament- a ligament that attaches the liver to the anterior (ventral) body wall.
Mesentery- the mesenteries is connective tissue that holds the small intestine in numerous folds in the abdomen.
Lesser Omentum- layer helps to hold the stomach and the duodenum below the liver.
Greater Omentum- layer of fat and connective tissue that lies over the entire abdominal cavity like an apron.