Lp 36 Flashcards
Bile does not require?
Enzymes
-enzymatic degradation of foodstuffs
-reduces macromolecules into absorbable substances
Enzymatic hydrolysis
-have molecules that are hydrophobic &hydrophilic at opposite poles
-emulsify fats (attach to fat droplets at one end & h20 at other)
Bile salts
SI absorbs?
-digested food
-minerals
-h20
H20, indigestible substances & bacteria pass into?
LI
H20 & minerals are reabsorbed; the rest?
Recal matter
-membrane -bound enzymes (on brush borders of SI microvilli) mediate last stage of protein digestion
-absorbed into mucosal cells via 2* transport (co- transported w/ na+)
Amino acids
3 monosaccharides derived from carbs?
-maltose: glucose (x2)
-sacrose: glucose + fructose
-lactose: glucose + galactose
-located next to carb enzymes
-work as soon as monosaccharides form
Carriers that transport sugars
-unique
-derivates of lipid digestion are h20 insoluble
-combine w/bile salts to form micelles
Lipids
-contain: f.a, monoglycerides, cholesterol & fat-soluble vitamins (A,D,E,K)
-outer surface is hydrophilic; interacts w/ h20 in lumen
-tiny
-diffuse b/w microvilli
-absorbed by intestinal mucosa
Lipids micelles
? Litres reach intestines daily
? % absorbed in SI
-9L
-95%
Fat-soluble & h20-soluble vitamins absorbed by?
Diffusion
Do transport w/sugars & a.a.
Na
-passively diffuses
-absorption of h20 increase k+ concentration in chyme
K
-co-transport (anti-port) in exchange for HCO3-
-HCO3- excretion: one method of ridding the body of ++ co2
Cl
-regulated by vit D
-only in duodenum
-decrease plasma {ca+} causes increase absorption
Ca
-actively transported
-stored in mucosal cells bound to ferritin
-decrease plasma [fe] causes increase fe uptake
-carried in blood carried by transferrin
Fe
-food moving from mouth to anus
-provided by smooth mm except in pharynx & upper 1/3 of esophagus (skeletal m)
Motility
-autorhythmic
-influenced by local, hormonal & neural factors
Smooth m in GI tract
Tonic movements last min to hrs
Movement is tonic & rhythmic
-constrict lumen
-push food down GI tract
-alt. Contraction of adjacent segments
-1 direction
Peristalsis
-nonadjacent segments alternately contract & relax
-food moves fwd & back
-mixing
Segmentation
Alimentary canal has its own nerve supply, the responsibility of?
Enteric neurons
Enteric neurons are semiautonomous & comprise most of the major?
Intrinsic nerve plexuses
-sensory & motor neurons
-largely regulate glands & smooth muscle in mucosa
Submucosa plexus
-between circular & longitudinal muscle layers of muscularis externa
-provide major n supply to GI tract wall & control GI tract motility
-control of patterns of segmentation & peristalsis is largely automatic, involving pacemaker cells & local reflex arcs
Myenteric plexus
-mostly excitatory
-increases motility (peristalsis) & secretion
-relaxes sphincters to allow movements of foodstuffs along tract
-increases bile secretion
Parasympathetic innervation
-inhibits motility
-constricts sphincters
-decreases secretions
-inhibits bile secretion
Sympathetic innervation
