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AnatomyPhysiology IV


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general roles of digestive system
digestion of food, absorption of nutrients and water from it
2 main parts of digestive system
alimentary canal (GI tract); accessory digestive organs
components of alimentary canal
small intestine
large intestine

list the accessory digestive organs
salivary glands

list the essential activities of the digestive process
mechanical digestion
chemical digestion

def. ingestion
taking food into the digestive tract
def. propulsion
swallowing and peristalsis
peristalsis -- waves of contraction and relaxation of smooth muscle in organ walls
def. mechanical digestion
chewing, mixing, churning food
def. chemical digestion
chemical breakdown of food into simple nutrients
def. absorption
movement of simple nutrients from GI tract to the blood or lymph
def. defecation
elimination of indigestible solid wastes
what kind of receptors are in the GI tract
they respond to what

respond to:

receptors in GI tract initiate what after they respond to stimuli
activate or inhibit digestive glands
speed up or slow down peristalsis

what are the main neural control systems
intrinsic neural control (enteric nervous sys)
extrinsic neural control
(autonomic nervous sys)

components of intrinsic neural control system
submucoal nerve plexus
myenteric nerve plexus
components of extrinsic neural control system
reflexes arising from:
or outside GI tract

the reflexes involve:
CNS centers
or autonomic nerves (long reflexes)

function of submucosal nerve plexus
regulates glands and smooth muscle in mucosa
function of myenteric nerve plexus
major nerve supply that controls GI tract mobility
what characterizes the processes of segmentation and peristalsis
large autonomic
involve local reflex arcs
relationship b/w intrinsic and extrinsic control systems
linked by autonomic reflex arcs
long reflexes vs. short reflexes
stimulus --> CNS --> local nerve plexus --> muscle effector --> response

straight from stimulus to local nerve plexus

peritoneal cavity
abdominal cavity that contains the GI tract organs
what is peritoneum?
gen char?

serous membrane of abdominal cavity

visceral layer
parietal layer

contains vasc and nerve supplies to viscera
holds dig organs in place and helps store fat
lubricates dig organs and allows them to slide rel to each other

arteries of dig sys
what organs do they serve
what are the arteries' functions

hepatic, splenic, L gastric --> spleen, liver, stomach

inf and sup mesenteric --> S and L intestines

to get nutrients from GI tract to rest of body tissues

what is hepatic portal circulation (compare to gen circ)
its functions
is a diversion before gen circ

prevents spikes in blood sugar -- collects nutient-rich venous blood from stomach, S and L intestines; delivers this to liver for processing and storage of nutrients before entering gen circ

what is the same from the esophagus to the anal canal
walls of GI tract have same four tunics

mucosa, submucosa, muscularis, externa, serosa

functions of mucosa
components in stomach in S intestine

secretion of mucus
to protect organs from digesting themselves
eases food along tract
____ of the end products of digestion
protects against infectious diseases

contain enzyme secreting cells, hormone secreting cells (therefore endocrine and digestive functions)

char of submucosa
connective tissue layer with:
elastic fibers
blood and lymph vessels
lymph nodes

what is attributed to muscularis externa
segmentation and peristalsis
role of serosa
protective visceral peritoneum
function of salivary glands; location
produce and secrete saliva that:
cleans mouth
moistens and dissolves food chemicals
aids in bolus formation

in mouth

list the types of salivary glands

functions of extrinsic salivary glands/what activates them
secrete enzyme-rich saliva in resp to:
ingested food (stimulates chemoreceptors)
thought of food
secretes amylase

function of amylase
enzyme that breaks down starches
function, location of intrinsic salivary glands
keep mouth moist
scattered throughout oral mucosa
what inhibits salivation
strong sympathetic activation
teeth are classified how; list the categories
by shape/function

premolars and molars

chisel-shaped; for cutting or nipping
conical, fangline teeth -- tear/piece
premolars and molars
have broad crowns with rounded tips for grinding or crushing
what are the regions of teeth
define crown; what are its components
exposed part of tooth above gingiva

pulp cavity

char of enamel; location
acellular, brittle material
made of Ca2+ salts and hydroxyapatite crystrals
hardest substance in body

on crown

definition gingiva
char of dentin; location
boneline material deep to the enamel cap
forms bulk of the tooth

on crown of tooth

char of pulp cavity; location
cavity surr by dentin
contains pulp

on crown of tooth

components of pulp
connective tissue
blood vessels

definition root
portion of tooth embedded in jawbone
definition root canal
portion of pulp cavity that extends into the root
definition of dental caries; process
cavities - gradual demineraliz of enamel and dentin by bacterial action

dental plaque (sugar, bacteria, mouth debris) adheres to tooth
bacteria prod acid
it dissolves Ca2+ salts
salts don't protect dentin and pulp from proteolytic enzymes

definition gingivitis; effect
plaque accumulates, calcifies, and forms calculus

this disrupts seal b/w gums and teeth --> gums at risk for infection

definition calculus
definition periodontitis
serious gum disease from immune response
immune sys attacks bacteria and body tissues, carving pockets around teeth and dissolving bone --> causes abcess
char, location, function of esophagus
muscular tube
from laryngopharynx to stomach
joins stomach at cardiac orifice
travels through mediastinum, diaphragm
glands secrete mucus as bolus moves through

general events occurring in stomach
chemical breakdown of proteins begins
food converted to chyme
definition chyme
liquified food
what is muscularis; function
muscular part of stomach allowing stomach to churn, mix, pummel food physically
breaks down food into small fragments/chyme
epithelial lining of stomach made up of what
goblet cells
function of goblet cells
produce coat of alkaline mucus that traps bicarbonate-rich fluid beneath it
what are gastric pits? function?
____ (in stomach)
contain gastric glands that secrete gastric juice, mucus, and gastrin
regulation of release of gastric juice (general)
neural and hormonal mechanisms in three phases
phases of control of gastric secretion
cephalic (reflex) phase
gastric phase
intestinal phase

cephalic phase
part of control of gastric regulation
before food entry
excit - sight/thought of food, stim of taste/smell receptors
inhib - loss of appetite, depression

gastric phase
part of control of gastric secretion
once food enters stomach
excit - stomach distension, activ of chemoreceptors, caffeine, rising pH, gastrin rel in blood
inhib - pH lower than 2, emotional upset overriding parasymp nervous signals

intestinal phase
part of control of gastric secretion
as partially digested food enters duodenum
excit - enters duodenum, stim gastric gland activity
inhib - distension of duodenum, presence of fatty, acidic, or hypertonic chyme; irritants in duodenum

when is HCl secretion highest
when all three ligands (ACh, histamine, gastrin) bind to parietal cells (part of gastric glands in stomach)
what decreases HCl release; where is it released from
antihistamines (they block H2 receptors)
what is the basic electrical rhythm (BER)
what initiates it
peristaltic waves move toward the pylorus at rate of 3 waves per min
initiated by smooth muscle pacemaker cells
fate of chyme in stomach
delivered in small amounts to the duodenum OR
forced backward into the stomach for further mixing
what is the effect of the pyloric sphincter relaxing
gastric emptying occurs
what mechanisms control speed of gastric secretion and emptying
carb-rich chyme quickly moves from stomach to duodenum

fat-rich chyme digested more slowly causing food to remain in stomach longer

small intestine runs from where to where
pyloric sphincter to ileocecal valve
what are the subdivisions of the small intestine

what connects small intestine and large intestine
ileocecal valve
where do the bile duct and pancreatic duct flow to
they join the duodenum at the hepatopancreatic ampulla
what controls the entry of bile and pancreatic secretions into the s. intestine
sphincter of Oddi
function of cells of intestinal crypts in small intestine
secrete intestinal juice
rel by intestinal glands in resp to distension of irritation of the mucosa
what is the largest gland in the body
list the divisions of the liver
4 lobes:

char of intestinal juice
alkaline and isotonic with blood plasma
mostly water but contains some mucus
where is gallbladder in relation to liver
rests in recess of R lobe of liver
path of bile ducts from liver
bile ducts fuse into common hepatic duct --> fuses with cystic duct from gallbladder --> bile duct
function of enterohepatic circulation
recycles bile salts
function of gallbladder
concentrates bile and stores it by absorbing water and ions out of the bile rel by liver cells
what causes bile release
acidic, fatty chyme in duodenum --> causes rel of CCK and secretin into blood --> gallbladder contracts, hepatopancreatic sphincter relaxes --> bile enters duodenum (part of s. intestine)
functions of the pancreas
exocrine -- secretes pancreatic juice, which breaks down all categories of food

endocrine -- rel of insulin, glucagon, etc for glucose homeostasis

how does pancreatic juice aid in digestion
acini (secretory cell clusters) release zymogen granules --> they contain digestive enzymes

bicarbonate in it neutralizes stomach acid in the duocenum (part of s. intestine)

examples of enzymes in pancreatic juice
trypsinogen --> activated in duodenum to trypsin
procarboxypeptidase --> carboxypeptidase

active when secreted: amylase, lipases, nucleases

secretin and CCK regulate release of what

secretin vs. CCK differences

bile from gallbladder
pancreatic juice from pancreas

both when fatty/acidic chyme enters duodenum

for p. juice:
once CCK reaches pancreas - induces rel of enzyme-rich p.juice
once secretin reaches pancreas - induces rel of bicarbonate-rich p. juice

what, other than secretin and CCK, induces p.juice release?
vagal (parasymp) stimulation
what in chyme has been digested when it reaches duodenum
carb and protein partially
no fat digestion
required conditions for digestion; where is digestion completed
completed in small intestine
chyme rel slowly
diluting and mixing chyme with bicarbonate (b/c it is hypertonic and acidic)
liver and pancreas supply bile, enzymes, bicarbonate

site of nutrient absorption
small intestine (ALL occurs there)
enzymes used for digestion of carb
salivary amylase
pancreatic amylase
brush border enzymes

can all saccharides be digested
all but cellulose
but only mono and di can be absorbed
what facilitates absorption of carb
glucose transports in enterocyte cell membrane by facil. diffusion
where do carbs go when they absorbed
enter capillary bed in villi of small intestine
transported to liver by hepatic portal vein
enzymes used for digestion of proteins
pepsin (stomach)
small intestine:
p. enzymes - trypsin, chymotrypsin, c.peptidase
brush border enzymes - aminopeptidase, c.peptidases, dipeptidases

what types of proteins can be significantly absorbed
single, di, tri peptides
where do amino acids go after absorption
enter capillary bed of villi in small intestine
transported to liver by hepatic portal vein
(just like carb)

what other than enzymes is req for digestion of fats
bile salts in high enough concen to fully solubilize fats (the critical micellar concentration)
enzymes/chemicals needed for digestion of fats
bile salts
pancreatic lipases
absorption process for fats
simple diffusion into intestinal cells
combine w/ proteins - rel as chylomicrons into lymphatic lacteals
chylomicrons transported to systemic circ via lymph

enzymes req for absorption of nucleic acids
pancreatic ribonucleases
deoxyribonuclease in small intestine
what form of nucleic acids can be absorbed
must be as single nucleic acids
absorption process for nucleic acids
active transport via membrane transport proteins
absorption of fat-soluble vitamins (which vit are these)
A, D, E, K
co-solubilized and co-absorbed with fats -- req bile salts for significant absorption
absorption of water-soluble vitamins (which vit are these)
B, C
by facilitated diffusion through transport proteins

except for B12 --> must be bound to intrinsic factor (prod by stomach) for efficient absorption by s. intestine

Ca2+ absorption regulated how
related to blood levels of Ca
regulated by vit D and parathyroid hormone
absorption of electrolytes and ions (Na+, Fe, anions)
most actively absorbed along the entire small intestine
Na+ - with glucose and AAs
iron - transported into mucosal cells; binds to ferritin
anions - passively follow elect gradient estab by Na+

water absorption
85% of water is absorbed in smalll intestine
moves in both dir across intest mucosa, but
net osmosis occurs when concen gradient is estab by active transport of solutes INTO mucosal cells
kidneys elim approp amount of water to maintain the proper balance

what can cause malabsorption of nutrients
anything interfering with delivery of bile or p.juice
damage to intestinal mucosa (bacterial infection)
gluten enteropathy (damages villi and reduces length of microvilli)

subdivisions of the large intestine
anal canal

where does ileum join the large intestine
at the cecum
what contains the appendix
regions of the colon
ascending colon
hepatic flexure
transverse colon
splenix flexure
descending colon
sigmoid colon

what part of the colon joins the rectum
sigmoid colon
list the sphincters of the anus
internal (involuntary control)
when are sphincters closed? is this contracted or relaxed?
all times other than during defecation - contracted
what are hemorrhoids
inflammation of superficial venous plexuses assoc with the anal canal that cause itchiness
what/where are bacterial flora
bacteria surviving the small intestine that enter cecum
bacteria entering via anus
actions of bacterial flora
colonize the colon
ferment indigestible carb
and therefore rel irritating acids and gases
synthesize B complex vitamins and vit K

actions of large intestine
absorption of water and electrolytes
propulsion of fecal material toward the anus
does digestion occur in the large intestine
no (other than by bacteria)
what causes diarrhea
lack of absorption of water and electrolytes by large intestine
what are haustral contractions
how do they occur
slow segmenting movements in large intestine that move the contents of the colon
haustras contract sequentially as stimulated by distension
what stimulates defecation
rectal walls fill with feces --> walls are distended --> stimulates contraction of rectal walls and relaxation of internal sphincter --> voluntarily the external sphincter is relaxed
compare gastric and duodenal ulcers (general)
erosion of mucosal lining of stomach
erosion of mucosal lining of upper duodenum
cause and treatment of gastric ulcer
insufficient protection of mucosa or excessive HCl prod

treat by decreasing HCl prod (histamine H2 receptor blockers like Pepsid) or neutralize gastric acid (antacids)

cause and treatment for duodenal ulcers
infection of mucosa by H.pylori bacteria

antibiotics and acid reducing medications; bismuth s. (Pepto-Bismol)

what are gallstones? what are they made up of?
precipitation or crystalliz. of some of components of bile in gallbladder
cholesterol, bile salts/pigments, calcium salts, or mixture
location of gallstones
stay in gallbladder or get lodged in one of ducts between gallbladder and small intestine
effect of backed up bile
into liver or pancreas -- infection and inflammation --> hepatitis, pancreatitis, cancer

from liver, eventually through blood and into tissues --> jaundice

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