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PHGY 216 EXAM LATEST UPDATE
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PHGY 216 EXAM LATEST UPDATEWhat is the gastrointestinal system - Answer continuous series of hollow, muscular
tubes that extend from the mouth to the anus, where the movement of muscles, along
with the release of various secretions, allows for the digestion and absorption of food
What is the primary role of the digestive system - Answer to take food and drinks that
are consumed and transfer the nutrients, water, and electrolytes into the body
What are the five stages of nutrient breakdown - Answer 1. Ingestion: physical act of
eating
2. Digestion: breakdown of food into small molecules that can be absorbed
3. Absorption: the movement of the nutrients from the digestive tract into the circulatory
system
4. Distribution: the movements through the circulatory system for delivery to the tissue
and cells
5. Usage: the movement of the nutrients into cells for metabolism or anabolic processes
What are the four basic digestive processes - Answer 1. Motility
2. Secretion
3. Digestion
4. absorption
What does motility refer to? - Answer muscle contractions that both mix and propel
contents of the digestive system
- smooth muscle cells in walls of digestive system have constant level of contraction, or
tone, to prevent too musch stretching of the walls to keep pressure on the contents
- propulsivle movements push contents forward
- mixing movements help mix the food with digestive enzymes, and promote absorption
by ensuring all contents eventually make contact with walls of the digestive system
what does the rate of movement of the digestive system depend on? - Answer the
segment of the digestive system, since contents are moved at an appropriate speed to
sllow each segment to do its job
What is the purpose of propulsive movements - Answer push contents forward
What is the purpose of mixing movements - Answer - help mix the food with digestive
enzymes
,- promote absorption by ensuring all contents eventually make contact with walls of the
digestive system
Which digestive organs use skeletal muscle rather than smooth muscle to move material
within them - Answer - top of the esophagus
- mouth
- external anal sphincter
Describe the basic digestive process of secretion - Answer - exocrine glands run along
the entire digestive system secreting digestive juices into the digestive tract lumen
- digestive juices vary throughout the digestive system depending on regional function,
but all contain water and electrolytes
- each section secretes a unique mixture of enzymes, bile salts, and mucus
- secretory cells of the glands get their water and raw materials from the plasma to
produce particular secretion
- upon signal appropriate neural or hormonal→secretions are released into the lumen of
the digestive tract
- normally all secretions are absorbed back into the body after they have completed
their role in digestion
- endocrin cells: secrete gastrointestinal hormones into the blood to help control motility
and exocrine gland secretion
all digestive juices contain - Answer water and electrolytes
Where do secretory cells of the glands get their water and raw materials from - Answer
the plasma
What is digestion - Answer the biochemical process of enzymatic breakdown of foods
that are structurally complex into small, absorbable units
- each of three food families (carbohydrates, proteins, and fats) undergo different
processes
Majority of carbohydrates are ingested as what - Answer polysaccharides
What are plant based polysaccharides are mainly - Answer starches
meats contain what polysaccharide - Answer glycogen
aside from the majority of carbohydrates that are ingested, what are other
carbohydrates that are ingested as... - Answer disaccharides like sucrose and lactose
all starch, glycogen, and disaccharides are broken down into... - Answer
,monosaccharides, mainly glucose with some fructose and glaactose
Dietary fats are usually consumed as... - Answer triglycerides (three fatty acids
attached to a glycerol moelcule)
Describe digestion of triglycerides - Answer broken down to release two fatty acids,
leaving a monoglyceride (glycerol molecule with one fatty acid molecule attached)
- allows both fre faty acids and monoglyceride to be absorbed
Most absorption occurs where - Answer in the small intestine, where diegstion is
completed
What occurs during the process of absorption - Answer the small absorbable units
produced as a result of digestion, along with water, vitamins, and electrolytes →move
from the digestive tract lumen into → the blood and lymph
What are the four major layers of the digestive tract walls - Answer 1. Mucosa
2. Submucosa
3. Musclearis externa
4. serosa
Describe the digestive tract wall: mucosa (location and characteristic) - Answer -
innermost layer that lines luminal surface
- surface is highly folded to increase surface area
- surface area is variable: in esophagus, there is little folding, while small intestine
(where absorption occurs) has highest amount of folding
Describe the digestive tract wall: submucosa (location and characteristic) - Answer -
thick layer made of connective tissues that support the mucosa
- contains larger blood and lymph vessels that send smaller branches to the mucosa and
to the outer layers
- contains submicosal plexus (network of nerves)
Describe the digestive tract wall: muscularis externa (location and characteristic) -
Answer - made up of smooth muscle layer that surrounds submucosa
- two muscle layers: inner circular layer, and outer longitudinal layer
- between muscles is another nerve network (myentric plexus)
What does contraction of inner layer of muscularis externa do - Answer decreases the
lumen diameter
, What does contraction of the outer longitudinal layer of the muscularis externa do? -
Answer shortens the tube
What is the function of muscularis externa (circular and longitudinal layers) - Answer
both layers provide the propulsive and mixing contractions
What is the myentric plexus - Answer nerve network between the circular and
longitudinal muscles of muscularis externa
What is the function of the myentric plexus - Answer along with hrmones and locl
chemical mediators, this structure in the muscularis externa (between the circular and
longitudinal muscles) regulates local gut activity
Describe the digestive tract wall: serosa (location and characteristic) - Answer -
outermost CT layer that covers digestive tract
- this CT layer is continuous throughout most of the digestive tract with the mesentry
- function: helps suspend the digestive organs from the inner wall of the abdominal
cavity, allowing them to move for mixing and propulsion
What is the mesentry - Answer a fold of membrane that attaches the intestine to the wall
around the stomach area and holds it in place
What are the four factors that regulate the digestive system function - Answer 1.
Autonomous smooth muscle function
2. Intrinsic nervous plexus
3. extrinsic autonomic nerves
4. Gastrointestinal hormones
What is Autonomous smooth muscle function - Answer smoth muscles cells that have
pacemaker-like rhythmic, spontaneous changes in membrane potential
What type of electric activity does Autonomous smooth muscle get triggers by - Answer
slow-wave potentials
Where does the slow-wave potentials conducted by to stimulate smooth muscle cells
originate - Answer non-contractile interstitial cells of Cajal
Where are the interstitial cells of Cajal located? - Answer at boundary of circular and
longitudinal muscle layers
Can slow-waves themselves induce contractions? - Answer no, as they are not action
potentials
Describe the autonomous smooth muscle function - Answer 1. Slow wave potentials are
produced by interstitial cells of Cajal
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