Chapter 41 - Organization of the Gastrointestinal System Flashcards
Is a tube that is specialized along its length for the sequential processing of food.
Gastrointestinal tube
The GI tract consists of both the series of ________ stretching from the mouth to the anus and the several __________ that add secretions to these hollow organs.
Hollow organs
Accessory glands and organs
The _______ and _______ are responsible for:
- Chopping food into small pieces
- Lubricating it
- Initiating carbohydrate and fat digestion
- Propelling the food into the esophagus.
Mouth and oropharynx
The ________ acts as a conduit to the stomach.
Esophagus
The ______ temporarily stores food and also initiates digestion by churning and by secreting proteases and acid.
Stomach
The _________ continues the work of digestion and is the primary site for the absorption of nutrients.
Small intestine
The ___________ reabsorbs fluids and electrolytes and also stores the fecal matter before expulsion from the body.
Large intestine
The accessory glands and organs include the:
- Salivary glands
- Pancreas
- Liver
The __________ secretes digestive enzymes into the DUODENUM in addition to secreting HCO-3 to neutralize gastric acid.
Pancreas
The liver secretes ______ which the gallbladder stores for future delivery to the duodenum during a meal.
Bile
Bile contains ___________ which play a key role in the digestion of fats.
Bile acids
The _______ consists of the EPITHELIAL LAYER, as well as an underlying layer of LOOSE CONNECTIVE TISSUE known as the __________ which contains CAPILLARIES, ENTERIC NEURONS and IMMUNE CELLS as well as a thin layer of SMOOTH MUSCLE known as ______________.
Mucosa
Lamina propria
Lamina muscularis mucosae (literally, the muscle layer of the mucosa).
The layer of epithelial cells can be EVAGINATED to form ________ or INVAGINATED to form ________.
Villi
Crypts (or glands)
Finally, on a larger scale the mucosa is organized into _________.
Large folds
The __________ consists of LOOSE CONNECTIVE TISSUE and LARGE BLOOD VESSELS.
Submucosa
The submucosa may also contain _______ that secrete material into the GI lumen.
Glands
The muscle layer, the ___________ includes two layers of smooth muscle. _________ are present between these two muscle layers.
Muscularis externa
Enteric neurons
The inner layer is ________.
Circular
The outer layer is _________.
Longitudinal
Assimilation of dietary food substances requires ________ as well as ________.
Digestion
Absorption
The sedentary human body requires _____ body weight each day.
30 kcal/kg
Note: This nutrient requirement is normally acquired by the oral intake of multiple food substances that GI tract then assimilates.
Absorb WATER and ELECTROLYTES.
Small and large intestine
Absorbs lipids, carbohydrates and amino acids.
Small intestine
Can provide sufficient calories to sustain adults and to support growth in premature infants.
Parenteral (i.e intravenous) alimentation
Has been used successfully on a long-term basis in many clinical settings in which oral intake is impossible or undesirable.
Total parenteral nutrition
Food substances are not necessarily - and often are - consumed in a __________ that the small intestine can directly absorb.
Chemical form
To facilitate __________, the GI tract digests the food by both MECHANICAL and CHEMICAL PROCESSES.
Absorption
_______ of ingested food begins in the mouth with CHEWING (MASTICATION).
Mechanical disruption
The mechanical processes that alter food composition to facilitate absorption continue in the _______, both to initiate protein and lipid enzymatic digestion and to allow passage of gastric contents through the pylorus into the duodenum.
Stomach
This change in the SIZE and CONSISTENCY of gastric contents is necessary because solids that are _______ in diameter do not pass through the pylorus.
> 2 mm
Although most lipids are consumed in the form of triacylglycerols, it is ________ and _________, not triacylglycerols that are absorbed by the small intestine.
Fatty acids
Monoacylglycerols
Thus, a complex series of _________ are required to convert dietary triacylglycerols to these smaller lipid forms.
Chemical reactions (lipid digestion)
Similarly, amino acids are present in food as PROTEINS and LARGE PEPTIDES, but only amino acids and small peptides - primarly _________ and ________ are absorbed by the small intestine.
Dipeptides
Tripeptides
Carbohydrates are present in the diet as:
- Starch
- Disaccharides
- Monosaccharides
However, because the small intestine absorbs all carbohydrates as __________.
Monosaccharides
Note: Most dietary carbohydrates require chemical digestion before their absorption.
Digestion requires enzymes secreted in the:
“SPMS”
- Stomach
- Pancreas
- Mouth
- Small intestine
_________ involves the conversion of dietary food nutrients to a form that the small intestine can absorb.
Digestion
For carbohydrates and lipids, these digestive processes are initiated in the mouth by salivary and lingual enzymes: ________ for carbohydrates and ________ for lipids.
Amylase
Lipase
*Carbohydrate digestion does not involve any secreted gastric enzymes.
___________ is initiated in the stomach by GASTRIC PROTEASES (i.e., pepsins), whereas additional lipid digestion in the stomach occurs primarily as a result of the lingual lipase that is swallowed, although some gastric lipase is also secreted.
Protein digestion
Digestion is completed in the ____________ by the action of both pancreatic enzymes and enzymes at the brush border of the small intestine.
small intestine
Pancreatic enzymes, which include ________, ________ and ________ are critical for the digestion of lipids, protein and carbohydrates, respectively.
lipase, chymotrypsin and amylase
The enzymes on the luminal surface of the small intestine (e.g., brush border disaccharidases and dipeptidases) complete the digestion of ___________ and ___________.
carbohydrates and proteins
Digestion by these brush border enzymes is referred to as ____________.
membrane digestion
The load to the small intestine is also significantly ________ than that of the ingested material.
greater
Dietary fluid intake is 1.5 to 2.5 L/day whereas the fluid load presented to the small intestine is __________.
8 to 9 L/day
The necessary control is achieved by neural and hormonal processes that are initiated by _____________; the result is a coordinated series of motor and secretory responses.
dietary food substances
