Digestive Physiology Flashcards
What is MECHANICAL DIGESTION?
The breakdown of large food particles into smaller food particles
What 3 structures are involved in MECHANICAL DIGESTION?
- TEETH (especially MOLARS and PREMOLARS)
- STOMACH (churning)
- SMALL INTESTINE (segmentation)
What is CHEMICAL DIGESTION?
Enzymatic breakdown of organic MACROMOLECULES into smaller MOLECULES (MONOMERS)
What happens to CHEMICAL BONDS during CHEMICAL DIGESTION?
They are broken
What is released when CHEMICAL BONDS are broken?
ENERGY
What is the ENERGY released by broken BONDS used for?
Making ATP
CHEMICAL DIGESTION involves________ _______
CATABOLIC REACTIONS (large macromolecules/polymers are broken down into smaller molecules/monomers)
True or false:
CATABOLIC REACTIONS are EXERGONIC/EXOTHERMIC
True
What happens during an EXERGONIC/EXOTHERMIC REACTION?
ENERGY is released when CHEMICAL BONDS are broken; this ENERGY can be used to make high ENERGY phosphate bonds in ATP
True or false:
A PROTEIN is a short POLYMER of AMINO ACIDS (A.A)
False
long not short
How many A.A are there? How many are essential in our diets?
20, 8
Give 2 examples of complex CARBOHYDRATES
STARCH and GLYCOGEN
Give 3 examples of DISSACCHARIDES
SUCROSE, MALTOSE, and LACTOSE
Give 3 examples of MONOSACCHARIDES
GLUCOSE, FRUCTOSE, and GALACTOSE
What does GLYCEROL + 3 FATTY ACIDS make?
TRIGLYCERIDE
Where does most absorption occur?
In the SMALL INTESTINE (S INT), especially in the ILEUM and JEJUNUM, across the BRUSH BORDER membrane
Where do small nutrient molecules go?
They move into EPITHELIAL CELLS, then into BLOOD or LYMPH CAPILLARY (LACTEALS)
How do MONOSACCHARIDES and A.As move into CELLS, even when concentration is high in CELLS
By COTRANSPORT
What is another way MONOSACCHARIDES and A.As move into CELLS
By FACILITATED DIFFUSION
*this only moves down the concentration gradient
How would products of PROTEIN and CARBOHYDRATE digestion enter the LIVER?
First step - Enter CAPILLARIES on the LAMINA PROPRIA
Second step - Enter the HEPATIC PORTAL VEIN
Then - They’ve made it to the LIVER, YAY
Are transporters required to bring LIPIDS (MONOGLYCERIDES + FATTY ACIDS) across the BRUSH BORDER MEMBRANE?
Nope
Are LIPIDS WATER-SOLUBLE?
No
duhh they’re LIPID-SOLUBLE
What must happen to LIPIDS before they can be transported in BLOOD or LYMPH?
They must be coated in PROTEIN and PHOSPHOLIPIDS
What are the LIPOPROTEINS called?
CHYLOMICRONS
How would FATTY CHYLE get from the LACTEALS to VEINS?
First step - LACTEALS deliver to CISTERNA CHYLI
Second step - Drains to the THORACIC DUCT
Then - They’re in the VEINS, YAY
What breaks down TRIGLYCERIDES in the ENDOTHELIUM of CAPILLARIES?
The ENZYME LIPOPROTEIN LIPASE
TRIGLYCERIDES break down into…
…MONOGLYCERIDES + FATTY ACIDS
FATTY ACIDS go to which 3 things?
- ADIPOSE TISSUE (stored as TRIGLYCERIDES)
- MUSCLE (used for ENERGY)
- The LIVER (processing center)
Where are LIPOPROTEINS synthesized?
In the LIVER
F of LIPOPROTEINS?
F - transport LIPIDS (TRIGLYCERIDES/CHOLESTEROL) to and from LIVER and TISSUES
True or false:
LOW DENSITY LIPOPROTEINS (LDL) = less of LIPID, lots of PROTEIN
False
LDL = Lots of LIPID, less PROTEIN
What is HIGH DENSITY LIPOPROTEIN (HDL)?
The opposite of LDL; less LIPID, lots of PROTEIN
What is a risk of high LDL?
Inc. risk of HEART ATTACK and STROKE
Which VITAMINS are water-soluble? How are they absorbed?
B and C, FACILITATED DIFFUSION
What is INTRINSIC FACTOR?
a GLYCOPROTEIN secreted by PARIETAL CELLS of STOMACH
What does INTRINSIC FACTOR do?
Enables the body to absorb VITAMIN B12
Which VITAMINS are fat-soluble? How are they absorbed?
A, D, K, and E, DIFFUSION with LIPIDS (incorporated into CHYLOMICRONS
What is PERNICIOUS ANEMIA?
A genetic defect that codes for INTRINSIC FACTOR; cannot absorb VIT B12, which is required for CELL division
True or false:
Transporters are not required for water-soluble and charged ions/electrolytes
False
They are required
Absorption of ions/electrolytes is done using ________ _______ or ________ __________
FACILITATED DIFFUSION, ACTIVE TRANSPORT
Na+ is…
…COTRANSPORTED
What activates the Ca2+ transporter?
VITAMIN D3 and PARATHYROID HORMONE (PTH)
What kind of transport does IRON use?
ACTIVE TRANSPORT (enhanced by VIT C/acids)
Which is easier to transport:
Fe3+ or Fe2+
Fe2+ (conversion facilitated by VIT C/acids
How does H2O enter the GI TRACT?
From food beverages and GI secretions
How many ml of H2O from food and fluids?
2000 ml
How many ml of H2O from saliva?
1500 ml
How many ml of H2O from gastric secretions?
2000 ml
How many ml of H2O from intestinal secretions?
1500 ml
How many ml of H2O from pancreatic secretions?
1500 ml
How many ml of H2O from bile?
500 ml
What is the total fluid entering the GI TRACT daily?
9000 ml
How is H2O reaborbed?
OSMOSIS
Where is 92% of H2O absorbed?
In the S. INT.
Approx. what % is reabsorbed in the LARGE INTESTINE (L. INT.)
6 - 7%
How many ml/day are excreted in FECES?
Only about 150 ml
2 things that regulate DIGESTION
- HORMONES
2. ANS - The ENTERIC PLEXUS
What is the ENTERIC PLEXUS?
A network od sensory and motor NEURONS in GI TRACT
When does the CEPHALIC PHASE occur?
Before food enters the STOMACH
What causes an inc. of SALIVA and GASTRIC JUICE during the CEPHALIC PHASE?
The sight/smell/taste/thought of food activates the HYPOTHALAMUS, which then inc. the activity of the PARASYMPATHETIC SYSTEM, which results in inc. SALIVA and GASTRIC JUICES
What activates the GASTRIC PHASE?
The arrival of food (especially PROTEIN) in the STOMACH
What 2 receptors are stimulated during the GASTRIC PHASE?
- CHEMORECEPTORS
2. STRETCH RECEPTORS
What is the result of inc. stimulation of CHEMORECEPTORS?
Inc. GASTRIC SECRETION (HORMONE secreted by G CELLS of GASTRIC GLANDS), therefore inc. GASTRIC JUICE and GASTRIC MOTILITY
What is the result of inc. stimulation of STRETCH RECEPTORS?
Inc. PARASYMPATHETIC activity (VAGUS NERVE), therefore inc. GASTRIC JUICE and GASTRIC MOTILITY
What is the INTESTINAL PHASE activated by?
The arrival of ACID CHYME in the DUODENUM
What does ACID CHYME in the DUODENUM activate?
CHEMO and STRETCH RECEPTORS
What do CHEMO and STRETCH RECEPTORS do?
Activate PARASYMPATHETIC RESPONSE, DUODENAL ENDOCRINE CELLS secrete HORMONES - SECRETIN and CHOLECYSTOKININ (CCK)
What is the effect of SECRETIN?
Inc. PANCREATIC NaHC03
Inc. BILE secretion by LIVER
Dec. GASTRIC SECRETION
Dec. GASTRIC MOTILITY
What is the effect of CCK?
Inc. PANCREATIC ENZYME secretion Inc. GALLBLADDER contraction Relaxes HEPATOPANCREATIC SPHINCTER Inc. PANCREATIC NaHCO3 Dec. GASTRIC secretion Dec. GASTRIC MOTILITY
Explain GLUCOSE DEPENDENT INSULINOTROPIC PEPTIDE (GIP)
Secreted when SUGARS and FATS enter DUODENUM
Stim. INSULIN secretion by PANCREAS
Stim. LIPOGENESIS in ADIPOCYTES
Explain VASOACTIVE INTESTINAL PEPTIDE (VIP)
Stim. INTESTINAL GLANDS, which inc. NaHCO3 and H2O secretion
Dilates INTESTINAL BLOOD VESSELS, which inc. BLOOD flow
What is MASS MOVEMENT?
A strong PERISTALTIC contraction of the COLON that occurs once or twice a day
GASTRIC and DUODENAL reflexes are activated by the…
…arrival of food in the STOMACH/INTESTINES
The distension of the RECTUM with FECES will activate what?
The DEFECATION reflex
What is the DEFECATION reflex?
Relaxation of the SMOOTH MUSCLE in the INTERNAL ANAL SPHINCTER
True or false:
The SKELETAL MUSCLE of the INTERNAL ANAL SPHINCTER is controlled by the PARASYMPATHETIC SYSTEM
False
The INTERNAL ANAL SPHINCTER is made of SMOOTH MUSCLE
True or false:
We have conscious control over the EXTERNAL ANAL SPHINCTER
True
What is the avg. transit time from MOUTH to ANUS?
24 - 48 hours
Where is appetite regulated?
The SATIETY CENTERS in the HYPOTHALAMUS
What is involved in short term regulation for dec. appetite?
STRETCH RECEPTORS in STOMACH Inc. BLOOD GLUCOSE on BLOOD Inc. A.A in BLOOD Inc. INSULIN Inc. CCK
What is involved in short term regulation for inc. appetite?
GHRELIN
What is GHRELIN?
A HORMONE secreted by CELLS lining the STOMACH when empty
What is involved in long term regulation for dec. appetite?
LECTIN
What is LECTIN?
A HORMONE secreted by ADIPOSE TISSUE
If there was an inc. in ADIPOSE TISSUE, there would also be an inc. in LECTIN, and therefore…
…a dec. in appetite
What may result in LEPTIN resistance?
Excess weight
