GI - Structure & Function Flashcards
What’s the major function of the GI tract?
Mechanical & Chemical Breakdown
This is a hollow tube that extends from the mouth to the anus.
GI Tract
The walls of the GI tract have several layers, what are they?
1) Mucosa
2) Muscularis mucosae
3) Submucosa
4) Tunica muscularis (Circular & Longitudinal muscle)
5) Serosa
Except for swallowing and defecation, which are controlled voluntarily, the functions of the GI are controlled by _________ & _________ autonomic nerves…collectively called the ________ plexus and intestinal __________.
- Intrinsic & Extrinsic
- Enteric
- Hormones
Digestion begins with the mouth with chewing & salivation. What’s the digestive component of saliva?
Alpha-amylase
-Initiates carb digestion
The esophagus is a muscular tube (tunica muscularis) that transports food from the mouth to stomach. What are the two muscle types w/in the esophagus?
- Upper = striated
- Lower = smooth muscle
What term describes how the food is propelled through the GI tract by the tunica muscularis?
Peristalsis
Swallowing is controlled by the swallowing center in the reticular formation of the brain. What are the two phases of swallowing?
1) Voluntary - Oropharyngeal
2) Involuntary - Esophageal
What has to open to admit swallowed food into the stomach and then closes to prevent regurge?
Lower esophageal sphincter
The stomach is a baglike structure that ________ digestive juices, ______ and ______ food, and _______ partially digested food (chyme) into the duodenum.
- Secretes
- Mixes & Stores
- Propels/Moves
What are the smooth muscles of the stomach?
- Outer longitudinal
- Middle circular
- Internal oblique
What nerve stimulates gastric (stomach) secretion and motility?
Vagus
What hormones stimulate & delay gastric emptying?
- Stimulate = Gastrin & Motilin
- Delay = Secretin & Cholecystokinin
Gastric glands in the funds and body of the stomach secrete this, which is needed for Vit. B12 absorption, and hydrochloric acid, which dissolves food fibers, kills microorganisms, and activates the enzyme pepsin.
Intrinsic Factor
What cells in the stomach secrete pepsinogen & what’s pepsinogen converted to in the acid environment created by hydrochloric acid?
- Chief cells
- Pepsin
What stimulates acid secretion?
1) Vagus nerve
2) Gastrin
3) Histamine
What inhibits acid secretion?
1) Sympathetic stimulation
2) Cholecystokinin
What NT stimulates pepsin secretion?
Acetylcholine
What is the function of mucus in the stomach?
Protection of the stomach wall from acid and digestive enzymes
What are the three phases of acid secretion by the stomach?
1) Cephalic phase (anticipation & swallowing)
2) Gastric phase (Food in stomach)
3) Intestinal phase (Chyme in intestines)
What 3 segments make of the small intestines?
1) Duodenum
2) Jejunum
3) Ileum
- 5m total length
What occurs in the small intestines?
Digestion and absorption of all major nutrients & most ingested water occurs in SI
The peritoneum is a double layer of membranous tissue that contains what two layers?
1) Visceral (covers ab. organs)
2) Parietal (along ab. wall)
What is the primary blood supply to the SI provided by?
Superior Mesenteric Artery
The duodenum receives chyme from the stomach through what valve?
Pyloric valve
The presence of chyme in the duodenum stimulates this to occur from liver, gallbladder, & pancreas?
- Liver & GB = Bile
- Pancreas = Digestive enzymes and alkaline secretions
Bile and enzymes flow into the duodenum through an opening guarded by what sphincter?
Sphincter of Oddi
Bile, produced in the ______ is necessary for fat _________ & _________.
- Liver
- Digestion & Absorption
Biles alkalinity helps neutralize ______, thereby creating a pH that enables the _________ enzymes to digest proteins, carbs, & sugars.
- Chyme
- Pancreatic
What are enzymes secreted by the small intestines that act in SI to digest Cabs, Pros, & Fats?
1) Maltase
2) Sucrose
3) Lactase
What are the Pancreatic enzymes that act in the SI for digestion of macronutrients?
1) Proteases
2) Amylase
3) Lipase
Besides SI & Pancreatic enzymes, what other substance is needed to aid in digestion w/in the SI of Macronutrients?
Bile salts