Week 12: Chp 55: Assessment of Gastrointestinal Function Flashcards
(138 cards)
What is the gastrointestinal system responsible for?
intake, digestion, and elimination of foods and fluids, and proper functioning is key to adequate nutrition
- known as the alimentary tract, begins with the esophagus and ends with the anus
- responsible for the digestion and absorption of nutrients and expelling of metabolic wastes
What are the two divisions of the GI system?
- Alimentary Tract
- Accessory Organs
If normal intake can not be through the mouth, how else is nutrition delivered?
nutrition may be delivered directly to the stomach or small intestine
Where does digestion begin?
begins in the mouth and continues in the stomach and small intestine
-the large intestine is responsible for reabsorption of fluids and electrolytes and elimination of waste products
What is the large intestine responsible for?
the reabsorption of fluids and electrolytes and elimination of waste products
What are the accessory organs?
teeth, tongue, salivary glands, liver, gallbladder, and pancreas
The GI tract consists of what?
the mouth, pharynx, esophagus, stomach, small intestine, and large intestine
The Mouth
where digestion begins, where the mechanical (mastication) and chemical breakdown of food occurs
The mechanical breakdown of ingested food occurs through the process of what?
mastication (chewing)
Mastication
- chewing
- the mechanical breakdown of ingested food
- saliva, which contains amylase, lipase, and lysozyme, is excreted from a group of glands: parotid, sublingual, and submandibular glands
- amylase is responsible for the chemical breakdown of carbohydrates, whereas lipase chemically digests fat; digestion of proteins actually occurs in the stomach
- lysozyme has antimicrobial properties that destroy the cell wall of bacteria in the mouth
Chemical breakdown
Saliva, which contains amylase, lipase, and lysozyme, is excreted from a group of glands: parotid, sublingual, and submandibular glands
- amylase is responsible for the chemical breakdown of carbohydrates, where a lipase chemically digests fat
- lysozyme has antimicrobial properties that destroy the cell wall of bacteria in the mouth
Deglutition
“swallowing”
consists of two phases and involves the pharynx, esophageal muscles, and the following cranial nerves CN V (trigeminal), CN VII (facial), CN IX (glossopharyngeal), and CN XII (hypoglossal)
-the buccal (mouth) phase involves the tongue and the pharyngeal muscles, and the esophageal phase involves the palate and esophageal muscles
-peristaltic movement of the esophagus moves the bolus of food into the stomach
2 phases of deglutition
“Swallowing”
- Buccal (mouth) phase: involves the tongue and the pharyngeal muscles
- Esophageal phase: involves the palate and esophageal muscles
The Esophagus: What is it and the location
is a hollow muscular tube that extends from approximately the vertebral levels of C6 to T7
-it is positioned inferior (below) to the pharynx and posterior (behind) to the trachea and passes through the diaphragm via a space known as the esophageal hiatus and then connects to the stomach
The Esophagus and what it does
the peristaltic movements push the food bolus downward as the esophagus constricts above the bolus and dilates below the bolus
-in normal digestion, the lower esophageal sphincter protects the esophageal mucosa from regurgitation of partially digested food and the acid produced in the stomach
What happens in the stomach?
digestion of protein -specialized cells secrete chemicals essential to the digestive functions of the stomach >Mucous Cells >Parietal Cells >Chief Cells >Enteroendocrine Cells
Stomach Cells: Mucous cells
secrete mucus that protects the stomach lining
Stomach Cells: Parietal Cells
secrete hydrochloric acid that aids in the conversion of food to chyme (partly digestive semiliquid food), as well as convert gastric lipase and pepsinogen to active forms
-also secrete intrinsic factor, a chemical needed for the absorption of vitamin B12, an important component of hemoglobin synthesis
Stomach Cells: Chief Cells
secrete the enzymes gastric lipase, which digests approximately 15% of dietary fat, and pepsinogen, which is responsible for protein digestion
Stomach Cells: Enteroendocrine cells
secrete hormones needed for digestion:
>Gastrin: stimulates secretion of hydrochloric acid and enzymes, and intestinal motility
>Serotonin: stimulates gastric motility
>Histamine: stimulates secretion of hydrochloric acid
>Somatostatin: inhibitory hormone that delays emptying of the stomach, reduces absorption in the small intestine, and inhibits secretions from the gallbladder and pancreas
Gastric Motility is influenced by?
smooth muscle regulated by the sympathetic and parasympathetic nervous systems
Before meals the stomach has a volume of what?
has a volume of 50 mL, but can hold up to 4 L at its fullest
-swallowing stimulates the swallowing center in the medulla oblongata to signal the stomach to stretch to receive food
What does the peristaltic contraction controlled by the pacemaker cells of the smooth muscle do in the stomach?
churn the food and mix it with gastric secretions
The stomach has 4 landmark areas
- the cardiac area (small segment below the gastroesophageal sphincter)
- fundic area (uppermost segment)
- corpus (body, and largest segment)
- pyloric area (lowermost segment and consists of the antrum, a narrow funnel that leads to the pyloric canal)