Chapter 3 - Digestion, Absorption, and Transport Flashcards
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What is the order that food goes through in the digestive tract?
Mouth to pharynx to epiglottis to esophagus to cardiac sphincter to stomach to pyloric sphincter to small intestine (duodenum, jejunum, ileum) to ileocecal sphincter to large intestine to rectum to anus
What are the seven challenges the body has to overcome with digestion?
- Arranging so swallowing and breathing don’t interfere with each other
- Making a passage way through the diaphragm to the stomach
- Moving slow enough that all rxns occur completely
- Keeping food at the right consistency (lubrication)
- Reabsorbing water
- Having cells that are protected against the powerful digestive juices
- Evacuation needs to occur periodically
What is the function of the mouth in the digestive system?
Chew (mastication) and mix food with saliva
What is the function of the pharynx in the digestive system?
Direct food from the mouth to the esophagus
What is the function of the epiglottis in the digestive system?
To protect the airways during swallowing
What is the function of the trachea in the digestive system?
To allow air to pass to and from the lungs
What is the function of the esophagus in the digestive system?
To pass food from the mouth to the stomach
What is the function of the cardiac sphincter in the digestive system?
To allow passage from mouth to esophagus and from esophagus to stomach; prevents backflow from stomach to esophagus and from esophagus to mouth
What is the function of the diaphragm in the digestive system?
To separate the abdomen from the thoracic cavity
What is the function of the stomach in the digestive system?
To add acid, enzymes, and fluid; churns, mixes, and grinds food to a liquid mass
What is the function of the pyloric sphincter in the digestive system?
To allow passage from the stomach to small intestine; prevents backflow from the small intestine
What is the function of the liver in the digestive system?
To produce bile salts (detergent-like substances which help digest fats)
What is the function of the bile duct in the digestive system?
To conduct bile from the gallbladder to the small intestine
What is the function of the gallbladder in the digestive system?
To store bile until dietary fat is present in the duodenum
What is the function of the small intestine in the digestive system?
To secrete enzymes that digest all energy-yielding nutrients to their basic building blocks; cells of wall absorb nutrients into blood and lymph
What is the function of the illeocecal valve/sphincter in the digestive system?
To allow passage from the small to large intestine; prevents backflow from the large intestine
What is the function of the pancreas in the digestive system?
Manufactures enzymes that are delivered to the lumen of the small intestine to digest all energy-yielding nutrients and release bicarbonate to neutralized acidic chyme that enters the small intestine
What is the function of the pancreatic duct in the digestive system?
To conduct pancreatic juice from the pancreas to the small intestine
What is the function of the appendix in the digestive system?
To store lymph cells
What is the function of the large intestine in the digestive system?
To reabsorb water and minerals; to pass stool (fibre, bacteria, and unabsorbed nutrients) along with water to the rectum
What is the function of the rectum in the digestive system?
To store wastes prior to elimination
What is the function of the anus in the digestive system?
To hold the rectum closes; open to allow elimination of waste
The sense of smell is _____ times _____ sensitive than the sense of taste
1000s, more
What are the segments of the small intestine?
Duodenum, jejunum, ileum
What are the two organs outside of the GI tract that aid in digestion?
The gallbladder and the pancreas; their enzymes are dripped in by the bile duct into the small intestine
How does food travel through the large intestine?
Past the appendix to the ascending colon to the transverse colon to the descending colon, past the sigmoid colon to the rectum
Define
Chyme
the semiliquid mass of partly digested food released by the stomach into the duodenum.
Define
Motility
The ability of the GI tract muscles to move
Define
Peristalsis
wavelike muscular contractions of the GI tract that propel its contents along.
Define
Segmentation
periodic squeezing or partitioning of the intestine at intervals along its length by its circular muscles.
Does peristalsis differ between organs or is it consistent process throughout?
The rate and intensities differ between organs
ex. 3/minute in the stomach but 10/minute in the small intestine
What determines the rate and intensity of peristalsis?
There is a natural rhythm based on the organ’s function, but it can be affected by:
* Stress
* Medication(s)
* Medical conditions (ex. gastroparesis)
What are unique features of the stomach that aid in digestion?
It has the thickest walls and strongest muscles of all the GI tract organs; it has three sets of muscles (circular, longitudinal, and diagonal) which aid is churning chyme
How often does the pyloric sphincter open?
3/minute, so chyme enters the SI in small portions
What is the purpose of segmentation?
To further break apart food particles in producing chyme and promoting close contact with the digestive juices and the absorbing cells of the intestinal walls before letting the contents move slowly along.
When does the upper esophageal sphincter open?
In response to swallowing
What are the differences between the dietary enzymes and hormones?
All enzymes and some hormones are proteins, but enzymes are not hormones. Enzymes facilitate the making and breaking of bonds in chemical reactions; hormones act as chemical messengers, sometimes regulating enzyme action
What rxn are dietary enzymes involved in?
Hydrolysis
What is saliva composed of?
Water, salts, mucus and enzymes that initiate the digestion of carbohydrates (salivary amylase)
Besides lubricating food, what function does saliva serve?
It protects the teeth, and the linings of the mouth, esophagus, and stomach from substances that might cause damage
ex. saliva neutralizes acids that breakdown enamel and also remineralize the teeth with the minerals within saliva
What are gastric juices composed of?
Water, enzymes, and hydrochloric acid
What is heartburn?
The sensation of HCl when it refluxes to the near-neutral esophagus
Why does stomach acid need to be so strong?
- Prevents bacterial growth and kills bacteria on our food
- Speed up the breakdown of food
What enzymes can function within the stomach’s low pH?
Stomach enzymes but not salivary amylase; the salivary enzymes then become additional proteins to digest
