Digestive System Flashcards
What are the main functions of the digestive system?
- Take in food
- Break down into nutrient molecules
- Absorb molecules into the bloodstream
- Get rid of waste
What are the two groups of the digestive system?
- Alimentary canal (gastrointestinal/GI/gut)
- Accessory digestive organs
What constitutes the alimentary canal?
Mouth, pharynx, esophagus, stomach, small intestine, large intestine and anus
What constitutes the accessory digestive organs?
Teeth, tongue, gallbladder, digestive glands, salivary glands, liver and pancreas
What is propulsion and what does it involve?
- Movement of food through the alimentary canal including:
- swallowing
- Peristalsis: altering waves of contraction and relaxation
What is a mesentery and what does it do?
A double layer of peritoneum- a sheet of two serous membranes fused back to back that extends to the digestive organs from the body wall.
- Provide routes for blood vessels, lymphatics, and nerves to reach the digestive viscera
- Hold organs in place
- Store fat
What is segmentation?
- The process of mechanical breakdown; chewing, mixing food with saliva, and churning food in stomach.
Digestion is a series of _______ steps that involve enzymes that break down complex food molecules into chemical building blocks
Catabolic
What does absorption mean?
Passage of digested fragments from lumen of GI tract into blood or lymph
What does defecation mean?
Elimination of indigestible substances via anus in form of feces
What are the four basic layers of all digestive organs?
Tunics:
- Mucosa
- Submucosa
- Muscularis externa
- Serosa
What does the mucosa or mucous membrane do?
- Secrete mucus, digestive enzymes and hormones
- Absorb the end products of digestion into the blood
- Protect against infectious disease
Simple columnar epithelium
What does MALT (the mucosa-associated lymphoid tissue) do?
Help defend against bacteria and other pathogens
What type of cells secrete mucous?
Mucous neck cells
What do parietal cells do?
Secrete HCL which activates pepsin and kills many bacteria and intrinsic factor needed for B12 absorption
What do chief cells secrete?
Pepsinogen and lipases
What do enteroendocrine cells secrete?
Paracrine chemicals e.g. serotonin and histamine into lamina propria, and hormones somatostatin and gastrin?
What two hormones/chemicals increase release of HCL?
Gastrin and histamine
What hormone decreases HCL secretion?
Somatostatin
What hormone increases gastric motility (the ability of an organism to move independently, using metabolic energy)?
Serotonin
What are the processes carried out by stomach?
- Carries out breakdown of food
- Serves as holding area for food
- Delivers chyme to small intestine
- Denatures proteins by HCI
- Pepsin carries out enzymatic digestion of proteins
- Lipid-soluble alcohol and aspirin are absorbed into blood
- Only stomach function essential to life is secretion of intrinsic factor for vitamin B12 absorption
What enzyme carries out digestion of protein in the stomach?
Pepsin
What are absorbed into blood in the stomach?
Lipid-soluble alcohol and aspirin
What is the only stomach function that is essential to life?
Secretion of intrinsic factor for vitamin B12 absorption
- Needed for red blood cells to mature
- Lack of intrinsic causes pernicious anemia
Liver, gallbladder and pancreas are accessory organs associated with ______?
Small intestine
What is the function of liver and what is it for?
Production of bile for detoxification