Digestive System Flashcards
organs involved in the digestion of food
digestive system
a continuous tube that extends from the mouth to the anus through the thoracic and
abdominopelvic cavities
Alimentary canal/ Gastrointestinal tract (GIT)
the length of the GI tract is about 5–7 meters (16.5–23 ft)
in a living person when the muscles along the wall of the GI tract organs are in a state of _____ (sustained contraction).
tonus
Teeth-Tongue-Salivary glands-Liver, Gallbladder- Pancreas
Accessory structures or gland organs
aid in the physical breakdown of food,
teeth
assists in chewing and
swallowing
tongue
taking food into mouth. This process involves taking foods and liquids into the mouth (eating)
ingestion
release of water, acid, buffers, and enzymes into lumen of GI tract
secretion
Each day, cells within the walls of the GI tract and accessory digestive organs secrete
a total of about _______liters of water, acid, buffers, and enzymes into the lumen (interior
space) of the tract.
7
churning and movement of food through GI tract
mixing and propulsion
Alternating________ of smooth muscle in the walls of the GI tract
mix food and secretions and move them toward the anus
contractions and relaxations
capability of the GI
tract to mix and move material along its length
motility
mechanical and chemical breakdown of food
digestion
the teeth cut and grind food before it is swallowed, and then
smooth muscles of the stomach and small intestine churn the food to further assist
the process. As a result, food molecules become dissolved and thoroughly mixed with
digestive enzymes.
mechanical digestion
the _____ cut and grind food before it is swallowed, and then
________of the stomach and _______ churn the food to further assist
the process. As a result, food molecules become dissolved and thoroughly mixed with
__________.
teeth
smooth muscles and small intestine
digestive enzymes
the large carbohydrate, lipid, protein, and
nucleic acid molecules in food are split into smaller molecules by hydrolysis. Digestive
enzymes produced by the salivary glands, tongue, stomach, pancreas, and small
intestine catalyze these catabolic reactions.
chemical digestion
the large carbohydrate, lipid, protein, and
nucleic acid molecules in food are split into smaller molecules by _______.
_______ produced by the salivary glands, tongue, stomach, pancreas, and small
intestine catalyze these catabolic reactions.
hydrolysis
Digestive enzymes
substances in food can be
absorbed without chemical digestion.
vitamins, ions, cholesterol, water
passage of digested products from GI tract into blood and lymph
absorption
The entrance of ingested and secreted fluids, ions, and the products of digestion into
the epithelial cells lining the lumen of the GI tract is called ______. The absorbed
substances pass into blood or lymph and circulate to cells throughout the body
absorption
elimination of feces from GI tract.
defecation
Wastes, indigestible substances, bacteria, cells sloughed from the lining of the GI
tract, and digested materials that were not absorbed in their journey through the
digestive tract leave the body through the anus in a process called
defecation
eliminated material is termed
feces
4 layers of GI tract
mucosa, submucosa, muscularis, and serosa/adventitia
mucous membrane lining the alimentary tract
mucosa
layer of mucosa that is in direct contact with the contents of the GI tract
epithelium
in the mouth, pharynx, esophagus, and anal canal is mainly ______ that serves a protective function
nonkeratinized stratified squamous epithelium
functions in secretion and absorption, lines the
stomach and intestines.
simple columnar epithelium
secrete hormones to the bloodstream
endocrine cells (enteroendocrine cells)
secrete mucus and fluid into the lumen of the GI tract
exocrine cells
layer of mucosa that is composed of loose areolar connective tissue to which the epithelial cells are
attached
lamina propria
contains nerves, blood vessels and lymph vessels which are the routes by which
nutrients absorbed into the GI tract reach the other tissues of the body.
lamina propria
Contains MALT (Mucosa-Associated Lymphoid Tissue)
lamina propria
contains immune system cells that protect the body against infection
or diseases. Found in the tonsils, appendix, SI, and LI
MALT
thin layer of smooth muscle which throws the mucous membrane of the stomach
and small intestine into many small folds, which increase the surface area for
digestion and absorption.
muscularis mucosae
Its movements ensure that all absorptive cells are fully
exposed to the contents of the GI tract.
muscularis mucosae
Inner layer of muscularis mucosae
circular layer
outer layer of muscularis mucosae
longitudinal
thick layer of areolar connective tissue that binds mucosa to the muscularis layer
submucosa
HIGHLY VASCULARIZED that receive absorbed food molecules
submucosa
contains SUBMUCOSAL PLEXUS/ PLEXUS OF MEISSNER
submucosa
a portion of the ANS: Enteric Nervous System that regulates/innervates the secretory cells of GIT
Plexus of Meissner
part of submucosa which is responsible in voluntary swallowing
*mouth, pharynx, superior and middle part of the esophagus, external anal spinchter
-which permits voluntary control of defecation
skeletal muscles
part of submucosa which is responsible in involuntary contractions
-throughout the rest of the GIT especially at the intestines
smooth muscles
contains the major nerve of the GIT and is parasympathetic
smooth muscles
controls GI motility/peristalsis
Myenteric Plexus or Plexus of Auerbach
increases GI motility
parasympathetic nervous system
layer of GI tract that is superficial or outermost layer; is a serous membrane composed of areolar connective
tissue and simple squamous epithelium (mesothelium).
serosa
ADVENTITIA of the esophagus (the esophagus lacks a serosa; instead, only a single
layer of areolar connective tissue)
serosa
lacks a serosa
esophagus
layer of GI tract that contains VISCERAL PERITONIUM (membrane that covers an organ of the GIT); because it forms
a portion of the peritoneum,
serosa
membrane that covers an organ of the GIT
visceral peritoneum
largest serous membrane of the bod
peritoneum
made up of the large folds that bind the organs together and to the
walls of the abdominal cavity
peritoneum
2 layers of peritoneum
simple squamous epithelium and connective tissue
type of peritoneum that lines the wall of the abdominopelvic cvity
parietal peritoneum
type of peritoneum that lines the organ in the abdominal cavity
visceral peritoneum
space between the parietal & visceral peritoneum
peritoneal cavity
type of peritoneum that are double layers of serous membrane
mesentery
A fan-shaped fold of the peritoneum
mesentery
contains blood and lymphatic vesssels and nerves supplying the abdominal
organs
mesentery
Holds GI in place
*the tip of the fold binds the SI to the posterior portion of the abdominal wall
mesentery
binds the LI to the posterior abdominal wall
mesocolon
carries blood vessels and lymphatic vessels to the intestines
mesocolon
“sickle-shaped” peritoneal fold
falciform
attaches the liver to the anterior abdominal wall
falciform
the only digestive organ attached to the anterior abdominal wall
liver
fast skin
omentum
suspends the stomach and doudenum from the liver
lesser omentum
pathway for blood vessels entering the liver and contains the hepatic
portal vein, common hepatic artery, and common bile duct, along with some
lymph nodes.
lesser omentum
largest peritoneal fold
greater omentum
it hangs loosely like a fatty portion over the transverse colon and coils to the SI
greater omentum
extends downward anterior to the SI then it extends upward and attaches to
the transverse colon
greater omentum
Greater omentum normally contains a considerable amount of _______, which can greatly expand with weight gain, contributing
to the characteristic “beer belly” seen in some overweight individuals.
adipose tissue
consists of mastication and movements of the gastrointestinal
tract that aid chemical digestion.
mechanical digestion
series of hydrolysis reactions that break down large
carbohydrates, lipids, proteins, and nucleic acids in foods into smaller molecules that
are usable by body cells.
chemical digestion
Folds of peritoneum
mesentery, mesocolon, falciform ligament, lesser
omentum, and greater omentum
extends from the lips to the oropharynx
mouth/ buccal cavity
fleshy folds surrounding the opening of the mouth. They contain the
orbicularis oris muscle and are covered externally by skin and internally by a mucous
membrane
lips/labia
middle fold of the mouth
labial frenulum
space between the gums and teeth
vestibule
opening between oral cavity and pharynx
fauces
anterior portion of roof of the mouth
hard palate
posterior portion of the roof of the mouth
soft palate
lateral walls of the oral cavity
cheeks
conical muscular process hanging from the soft palate
uvula
a fold of mucous membrane in the midline of the undersurface of
the tongue, is attached to the floor of the mouth and aids in limiting the movement of
the tongue posteriorly
lingual frenulum
accessory digestive organs located in sockets of the alveolar processes of the mandible
and maxillae.
teeth/ dentes
part of tooth that is the visible portion above the level of the gums
crown
part of tooth that is the constricted junction of the crown and root near the gum line
neck
part of tooth that is embedded in the socket are one to three ______.
roots
a calcified connective tissue that gives a tooth its shape and rigidity; encloses
the pulp cavity
dentin
it is harder than the bone because of its higher content of Ca salts
*70% of its dry weight consists of Ca salts
dentin
-lies in the crown and is filled up with PULP or connective tissue
-contains blood vessels, nerves and lymphatic vessels
pulp cavity
a narrow extension of the pulp cavity that runs thru the root of the tooth
root canal
an opening at the base of the root canal thru which blood vessels, lymphatics
and nerve pass thru or enter
apical foramen
the HARDEST substance of the body
-the richest with Ca salts: Ca phosphate and Ca carbonate (95% of its dryweight)
-covers the dentin
enamel
protects the tooth from “wear-and-tear” when chewing
enamel
a bone-like substance which attaches the root to the periodontal ligament
cementum
covers the dentin of the root of the tooth
cementum
sockets where the teeth are rooted on
alveoli
-lines the alveolar wall
periodontal membrane
extend slightly into each socket forming gingival sulcus
gingivae/ gums
anchors/holds the teeth in position and acts as shock-absorber when chewing
periodontal ligament
Type of teeth that has 10 pairs; 1 pair of teeth appears each month until all the 20 are present
-start to fall of between the ages of 6 and 13 and be replaced by permanent teeth
temporary/milk teeth/baby teeth/ deciduous teeth
falling out
decidu
type of teeth that has 32 or 16 paires
-incisors, canine, first molar, and second molar
permanent/secondary teeth
permanent teeth that has 4 pairs: 2 pairs of central & 2 pairs lateral
incisors
permanent teeth that has 2 pairs of poined cusps for tearing
canines/cuspids
permanent teeth that has
1st: 2 pairs
2nd: 2 pairs
premolars/bicuspids
permanent teeth
1st (2 pairs) erupt t age 6-7
2nd (2 pairs) erupt at age 11-13
3rd (2 pairs) erupt at age 17-21
molars
-results from chewing (Mastication) thru the coordinated functions of the tongue
and teeth
mechanical digestion
ingested foods in mechanical digestion is reduced to soft, flexible mass called
bolus
it is facilitated by the action of 2 enzymes
chemical digestion
enzyme for chemical digestion that breaks down starch
Salivary amylase
enzyme for chemical digestion that starts the breakdown of triglycerides into f.a and monoglycerides
lingual lipase
keep food between teeth
cheeks and lips
secrete saliva
salivary gland
move tongue from side to side and in and out
extrinsic tongue muscles
alter shape of toungue
intrinsic tongue muscle
serve as receptor for gustation and presence of food in mouth
taste buds
secrete lingual lipase
lingual glands
cut, tear, and pulverize food
teeth
the common passageway of food, air and fluid
pharynx
When food is first swallowed, it passes from the mouth into the _______ ( throat), a
funnel-shaped tube that extends from the internal nares to the esophagus posteriorly
and to the larynx anteriorly
pharynx
structure in the pharynx which is the conical muscular process hanging from the free border of the soft palate
*together with the soft palate, it closes of te nasopharynx preventing
swallowed food or fluid to enter nasal cavity
uvula
structure of the pharynx which is the anterior arch/pillar
palatoglossal arch
structure of the pharynx which is the posterior arch/pillar
palatopharyngeal arch
a collapsible muscular tube, about 25 cm (10 in.) long, that lies posterior to the trachea. It begins at the inferior end of the laryngopharynx, passes through the inferior
aspect of the neck, and enters the mediastinum anterior to the vertebral column.
Esophagus
esophagus pierces the diaphragm through an opening called the _______, and ends in the
superior portion of the stomach.
Esophageal Hiatus
the movement of bolus thru the esophagus is facilitated by
peristalsis and mucus
The involuntary and coordinated contraction and relaxation of the circular
and longitudinal muscles of the esophagus
peristalsis
secreted by the esophageal glands lubricates the bolus and reduces friction
mucus
made up of circular muscles that regulates the movement of food into and out of the
esophagus
esophageal sphincters
relaxation of this spinchter allows the movement of food from the pharynx into
the esophagus
Upper esophageal sphincter (UES)
regulates the movement of food from the esophagus into the stomach.
lower esophageal sphincter (LES)
- the movement of food from the mouth to the stomach
-Facilitated by the secretion of saliva and mucus and involves the mouth,
pharynx, and esophagus.
deglutition (swallowing)
stage of deglutition whereas bolus is forced backward into the oropharyx thru the movement of
the tongue
voluntary stage
stage of deglutition whereas involuntary passage of the bolus from the oropharynx into the
laryngopharynx
*as the larynx rises, the epiglottis move backward and downward, sealing off the
rima glottides: this movement pulls the vocal cords together, sealing off the
respiratory tract while widening the opening between the laryngopharynx and
esophagus
pharyngeal stage
stage of deglutition whereas involuntary passage of bolus from the laryngopharynx to
esophagus into the stomach
esophageal stage
The esophageal stage of swallowing begins once the _______enters the _________. During
this phase, _________, a progression of coordinated contractions and relaxations of the
circular and longitudinal layers of the muscularis, pushes the bolus onward.
bolus, esophagus
peristalsis
Swallowing starts when the bolus is forced to the back of the oral cavity and into the
_____ by the movement of the tongue upward and backward against the ________;
these actions constitute the ______. With the passage of the bolus
into the oropharynx, the __________ of swallowing begins. The bolus
stimulates receptors in the oropharynx, which send impulses to the deglutition center in
the _____ and lower _______ of the brain stem. The returning impulses cause
the_______ and _____ to move upward to close off the nasopharynx, which prevents
swallowed foods and liquids from entering the ______. In addition, the _____
closes off the opening to the larynx, which prevents the bolus from entering the rest of
the ____________. The bolus moves through the _________ and the________.
Once the _______________ relaxes, the bolus moves into the ___________.
oropharynx, palate
voluntary stage of swallowing
involuntary stage of swallowing
medulla oblongata, pons
soft palate, uvula, nasal cavity
epiglottis, respiratory tract
oropharynx, laryngopharynx
upper esophageal sphincter, esophagus
Peristalsis
occurs in other tubular structures, including other parts of the GI tract and the ureters,
bile ducts, and uterine tubes; in the esophagus it is controlled by the ____________.
medulla oblongata
- In the section of the esophagus just superior to the bolus, the____________
contract, constricting the ____________ and squeezing the bolus toward the
stomach. - ______________ inferior to the bolus also contract, which shortens this inferior
section and pushes its walls outward so it can receive the bolus. The contractions are repeated in waves that push the food toward the stomach. Steps 1 and 2 repeat until
the bolus reaches the______________. - The lower esophageal sphincter relaxes and the bolus moves into the ______________.
circular muscle fibers, esophageal wall
longitudinal fibers
lower esophageal sphincter muscles
stomach
secreted by esophageal glands lubricates the bolus and reduces friction.
mucus
The passage of solid or semisolid food from the mouth to the stomach takes 4 to 8 seconds
4 to 8 seconds
very soft foods and liquids pass through in about 1 second
1 second
Mastification- Bolus- chemical receptors in the oropharynx- impulses are sent to the
Deglutition Area (M.O. and Pons)-innervation of the organs
true
mechanism that move foods from the mouth into the stomach. Breathing is temporarily interrupted
deglutition
shapes the chewed, lubricated food(bolus) and moves it into the back of the mouth cavity
tongue
rises against the palate and closes the nasopharynx
tongue
seal off the nasal cavity
uvula and soft palate
covers the larynx
epiglottis
lubricates esophagus for smooth passage of bolus
mucus
J-shaped enlargement of the GI tract directly inferior to the diaphragm in the abdomen
stomach
connects the esophagus to the duodenum, the first part of the small intestine
stomach
located at the epigastric, umbilical region & left of hypochondriac region of the abdomen
stomach
where bolus is converted into CHYME (food in liquid form)
stomach
bolus is converted into _____ which is its liquid form
chyme
serves as a mixing vat & holding reservoir
stomach
capacity of stomach
1.5 L
where the chemical digestion of CHON starts & digestion of triglycerides continues
stomach
area around cardiac opening; surrounds the opening of the esophagus into the
stomach.
cardia
rounded portion, superior & left of cardia
fundus
area of stomach inferior to the fundus; largest portion
body
connects to the duodenum
pylorus
part of pylorus that connects to the body of the stomach
pyloric opening/antrum
part of pylorus that leads to the third region
pyloric canal
The pylorus communicates with the duodenum of the small
intestine via a smooth muscle sphincter
pyloric sphincter
wrinkles and large folds of mucosa & submucosa (when the stomach is empty, the mucosa
forms large folds called rugae)
rugae
curve of the stomach, right border; medial concave
lesser curvature
curve of the stomach, left border; lateral convex
greater curvature
layers of simple columnar epithelial cells
mucosa
made up of 5 types of cells
-these epithelial cells extend down into the lamina propia where they form
columns of Secretory Cells called Gastric Glands
epithelial layer of mucosa
secretory cells that release their secretions through the Gastric Pits
gastric glands
a narrow channel where the secretion of the gastric glands flow into
the lumen of the stomach
gastric pits
type of gastric glands
exocrine and endocrine gland cells
exocrine gland cell that secrete mucus
mucous neck cells
exocrine gland cells= that secrete pepsinogen and gastric lipase in exocrine gland cells
chief cells/ zymogenic cells
exocrine gland cells that secrete hydrochloric acid; intrinsic factor needed for the
absorption of Vit B12
parietal cells
Lack of the intrinsic factor results to ____________ bec. Vit
B12 is necessary for RBC production
pernicious anemia
Consist of the secretions of the mucous neck cells, chief (zymogenic cells) &
the parietal cells
- 2000 to 3000 ml/day
gastric juice
endocrine cells that secrete he hormone Gastrin into the bloodstream
G-cells
endocrine gland cells that secrete mucus that coats and
protects the lining of the stomach
mucous surface cells (MSC)
made up of 3 layers of smooth muscles that allows the stomach to churn
food and break them into small particles & mix them with gastric juice
muscularis
made up of smooth muscles
muscularis mucosae
3 smooth muscles in muscularis
inner oblique, middle circular, and outer longitudinal
covers the stomach; part of the visceral peritoneum
serosa
at the__________, serosa extends superiority to the liver as the lesser
omentum
lesser curvature
at the _____________, serosa continues inferiorly as the greater omentum &
drapes over the intestines
greater curvature
function of stomach the mixing waves or peristaltic movement pass every 15-25 sec
-bolus is reduced to its liquid form called chime juice
mixing of food
function of stomach for storing food
reservoir of food
the storage area (food remains without being mixed with gastric juice in 1 hr)
fundus
solid foods stay the stomach for _______ hrs
4-5
liquid foods stay in the stomach for ____hrs
2-4
function of stomach that is the combination of the different types of muscles enables the stomach to break food into
smaller pieces
churning of food
______ in the stomach absorb water, ions, & short-chain
fatty acids as well as certain drugs
mucous cells
digestion activities are initiated by impulses from the brain specifically
the cerebral cortex & feeding center in the hypothalamus
cephalic phase
mocus as the stimulation of gastric contraction & secretion continues;
governed by the Neural & hormonl mechanisms
Gastric phase
starts with the activation of the receptors in the small intestines
intestinal phase
reflexes initiated during the ___________ phases stimulate secretory activity & GI
motility
cephalic and gastric
During the ______ phase, inhibitory mechanisms occur
intestinal
Cephalic Phase
a- Prasympathetic postganglionic fibers of the submucosal plexus (Plexus of
Meissner)
b- Passing through the medulla oblongata
c- Parasympathetic preganglionic fiber of CN X (Vagus Nerve)
d- Transmission of the impulses to the cerebral cortex & feeding center at the
hypothalamus
e- Smell, sight, thought of a certain food
f- Increased release of these gastric secretions from the gastric glands
g- Stimulation of the sensory receptors
h- Stimulation/innervations of the secretory cells
*parietal cells: HCl & intrinsic factor
*Chief cells: pepsinogen & gastric lipases
*mucus cells: mucus
e
g
d
b
c
a
h
f
Gastric phase (neural mechanism)
a- Increased secretion of gastric juice & increase peristalsis/ motility
b- Vagus nerve (parasympathetic stimulation)
c- Food
d- Impulses are conveyed to the vagus nerve
e- Stimulation of the stretch receptors (detect stomach distention) & the
chemical receptors (detect changes in pH of gastric content
f- Submucosal plexus
g- To the medulla oblongata
h- 1) Food mixes with gastric juice
2) As peristaltic waves become stronger, a small of Chyme squirts through
the pyloric sphinchter (10-15 ml/ 2-3 tsp of chime)
c
e
d
g
b
f
a
h
Gastric phase (hormonal mechanism)
- Partially digested CHONs buffer/ neutralize hydrogen ions
- increase in the pH of gastric contents
stretching of the smooth muscles of the stomach/distention of the stomach
-stimulation of the stretch receptors (mechanoreceptors) and chemical
receptors
-Parasympathetic fibers are stimulated
-Release of acetylcholine
-Ach stimulates secretion of gastrin by the enteroendocrine/ G cells
-Release of gastrin into the bloodstream
Gastrin acts on the target organs/cells
-Stimulate the growth of gastric glands
*increases secretion of gastric juice
*strengthens contraction of LES
*relaxes the pyloric spinchter & ileocecal spinchter
increases mobility of the stomach
-the release of gastrin is stimulated when the pH increases and is inhibited when
the pH is below 2 (acidic)
Intestinal phase
- Entrance of chime with fatty acids & glucose into the SI
- Stimulation of the enteroendocrine cells of the mucosal layer of the SI
- Release of 3 hormones in the blood
*GIP (Gastric inhibitory peptide)- ingibits gastric secretion and gastric motility &
emptying
*Secretin- stimulates release of pancreatic juice rich in bicarbonate; stimulates bile
secretion; decreases gastric secretions
*CCK (cholecytokinin)- stimulates release of pancreatic juice rich in digestive
enzymes; nduces satiety
- The presence of chime containing f.a. & glucose distends the duodenum
- Stimulation of stretch receptors
- Impulses are sent to the medulla oblongata
- Inhibitory signals are sent to submucosal plexus
- Stomach is inhibited to secrete gastric secretion inhibition GI motility
Regulation of Gastric emptying
a- Gastric emptying (passage of chime from the stomach into the duodenum)
b- Increase in gastrin secretion (hormonal mechanism)
Increase vagus nerve stimulation (neural mechanism)
c- Distention of the stomach because of chime/ the presence of partially digested CHON or
other substances like alcohol & caffeine
d- Contraction of the LES
Increase motility of the stomach
Relaxation of the pyloric spinchter
c
b
d
a
Inhibition of gastric emptying
a- Initiation of enterogastric reflex — Increase in the secretion of CCK
b- Impulses propagate from the duodenum to the stomach
c- Distention of the duodenum; presence of f.a., glucose and partially digested CHON in the
duodenal chyme
d- Inhibition of the parasympathetic nervous system
Stimulation of the sympathetic nervous system
Decreased stomach motility
Decreased gastric emptying
c
a
b
d
longest portion of the GIT about 5m long & 2.5 cm dm
small intestine
where almost digestion & absorption occur
-chyme remains for 3-5 hrs
small intestines
distal end of pyloric sphincter
cecum
shortest region of small intestine,
and is retroperitoneal. It starts at
the pyloric sphincter of the
stomach and is in the form of a C-shaped tube that extends about
25 cm (10 in.) until it merges with
the jejunum;
duodenum
means “12”; it is so
named because it is about as long
as the width of 12 fingers.
-receives secretions from liver
(bile) & pancreas (pancreatic
juice)
duodenum
in the small intestine about 1 m (3 ft) long and extends to the ileum.. - means “empty,” which is how it is found at death.
jejunum
the final and longest region of the small intestine
ileum
ileum joins the large intestine at a smooth muscle sphincter
called the
ileocecal sphincter (valve)
epithelium mucosa of the small intestine is made up of ____ types of cell
4
digest and absorb nutrients; release enzymes that digest food
and contain microvilli that absorb nutrients in small intestinal chyme
absorptive cells
apical membrane of absorptive cells forms
microvilli
increase the surface area for absorption
microvilli
secrete mucus in the mucosa of small intestines
goblet cells
secrete lysozyme: a bacterial enzyme
paneth cells
by the S cells- secretes pancreatic juice
secretin
by the CCK cells
Cholecystokinin (CCK)
K cells
GIP (gastric inhibitory peptides)
numerous at the distal portion of the ileum
solitary lymphatic lymph nodes
group of lymphatic nodules at the ileum
-help destroy microbes from the SI
payer’s patches
permanent ridges
Villi-finger-like structures of mucosa
-increase the surface area for absorption
-has areolar connective tissue with arteriole & venule capillary network
-has LACTEAL or lymphatic capillary
muscularis mucosae
contains Brunner’s g;ands
submucosa
secrete alkaline mucus that neutralizes the
acidic chime
Brunner’s glands
membrane surrounding the small intestines
serosa
a clear yellow fluid, is secreted each day.
- slightly alkaline (pH 7.6)
intestinal juice
synthesized by the absorptive epithelial cells of the microvilli
brush-border enzymes
protein-digesting enzymes
peptidases
Brush-border enzymes
1. carbohydrate-digesting enzymes
a. dextrinase
b. maltase
c. sucrose
d. lactase
2. protein-digesting enzymes called peptidases
a. aminopeptidase
b. dipeptidase)
3. nucleotide-digesting enzyme
a. nucleosidases
b. phosphatases
digestion controlled by the ANS
mechanical digestion
localized, mixing contractions that occur in portions of intestine
distended by a large volume of chyme.
segmentation
termed a migrating motility complex (MMC)
-consist of mild waves of contraction & relaxation of circular & longitudinal
muscles, passing thru the length of the SI & pushing chime into the ileocecal
spinchter
peristalsis
secreted by he acini (clusters of glandular epithelial cells of
the pancreas)
pancreatic juice
clusters of glandular epithelial cells of
the pancreas
acini
a hormone that stimulates the production of
intestinal juice
VIP or vasoactive intestinal polypeptide
decrease intestinal motility
sympathetic impulses
pasive transport of absorption
diffusion
with the aid of hollow, channel like-proteins
facilitated diffusion
with the expenditure of energy (ATP)
active transport
absorbed as monosaccharides
CHO
undergo facilitated diffusion
fructose
undergo active transport with Na
galactose and glucose
absorbed as amino acids
CHON
absorbed as fatty acids in simple diffusion
fats
facilitated by calcitriol (active form of vitamin D)
calcium
% of nutrients absorbed in the small intestine
90%
% of nutrients absorbed in stomach and long intestine
10%
absorbed via osmosis
water
terminal portion of the GI tract
- is about 1.5 m (5 ft) long and 6.5 cm (2.5 in.) extends from the ileum to the anus
- attached to the posterior abdominal wall by its mesocolon
long intestine
-has no villi or permanent folds
long intestine
the SI joins the LI thru the
ileocecal sphincter
a small pouch
cecum
a twisted, coiled tube
appendix
ascends on
the right side of the abdomen,
reaches the inferior surface of the
liver, and turns abruptly to the left
to form the right colic (hepatic)
flexure.
ascending colon
The colon continues across the abdomen to the left side
4. Descending colon
transverse colon
begins near the left iliac crest, projects medially to the
midline, and terminates as the rectum at about the level of the third sacral
vertebra.
sigmoid colon
Where the completion of absorption of water, some ions and vitamins. Produce certain vitamins
*bacteria in the LI produce some vitamins & Vit K. It form feces andexpel waste products
long intestine
mechanical physiology of large intestine (gastroileal reflex)
Meal
intensified ileal peristalsis
chime is pushed to the cecum
Distention of the cecum
Contraction of the ileocecal spinchter
Haustral Churning
mechanical physiology of large intestine (haustral churning)
As chime passes thru the ileocecal sphincter
Accumulation of food material at the ascending colon
Distention of the haustra
Contraction of the intestinal wall
Squeezing off contents to the next haustrum
mechanical physiology of large intestine (mass peristalsis)
With increase peristalsis
Colon contents are propelled into the rectum
anus
The final stage of digestion occurs in the colon through the activity of bacteria that
inhabit the lumen. Mucus is secreted by the glands of the large intestine, but no
enzymes are secreted. Chyme is prepared for elimination by the action of bacteria,
which ferment any remaining carbohydrates and release hydrogen, carbon dioxide,
and methane gases.
chemical digestion in long intestine
CHO of chemical digestion
Intestinal bacteria
Ferments remaining CHO
Hydrogen, CO2 & methane gas
Flatus (gas in the colon)
*flatulence: gas formation in excessive amount
CHON of chemical digestion
Bilirubin: decomposed into simpler pigments called
Stercobilin (gives feces a brown color)
Some vitamins are bacterial products
B vitamins; Vitamin K
Absorbed in the colon
Physiology of defecation
Mass peristaltic movements of the LI
Fecal material is pushed in the rectum
Rectal wall distention
Stimulation of streton receptors
Sensory impulses are sent to the sacral spinal cord
Motor impulses from the spinal cord. are conveyed thru the parasympathetic nerve fibers
Stimulation of the descending colon, sigmoid, rectum and anus
Contraction of the longitudinal rectal muscles
Shortening of the rectum
Increase pressure in the rectum
*along the voluntary contraction of the diaphragm, abdominal muscles
Expulsion of the feces thru the anus
*parasympathetic stimulation/opening of the internal spinchter
- largest
-located inferior and anterior to the ears, between the skin and the
masseter muscle
parotid glands
found in the floor of the mouth; they are medial
and partly inferior to the body of the mandible.
-contain cells similar to those found in the parotid glands, plus some
mucous cells, they secrete a fluid that contains amylase but is thickened
with mucus.
submandibular glands
beneath the tongue and superior to the
submandibular glands.
sublingual glands
the secretion of saliva
- controlled by the autonomic nervous system.
-average 1000–1500 mL of saliva daily
salivation
___________ promotes continuous secretion of a moderate amount
of saliva, which keeps the mucous membranes moist and lubricates the movements of the
tongue and lips during speech. The saliva is then swallowed and helps moisten the __________.
Eventually, most components of saliva are reabsorbed, which prevents ________.
parasympathetic stimulation
esophagus
fluid loss
__________ dominates during stress, resulting in dryness of the mouth. If
the body becomes ___________, the salivary glands stop secreting saliva to conserve water;
the resulting dryness in the mouth contributes to the sensation of______.
sympathetic stimulation
dehydrated
thirst
The feel and taste of food also are potent stimulators of salivary gland secretions.
_________ in the food stimulate receptors in taste buds on the tongue, and impulses are
conveyed from the taste buds to two salivary nuclei in the brain stem (_______ and _________
salivatory nuclei). Returning parasympathetic impulses in fibers of the ______ and
______ (IX) nerves stimulate the secretion of saliva. Saliva continues to be secreted
heavily for some time after food is swallowed; this flow of saliva washes out the mouth and
dilutes and buffers the remnants of irritating chemicals such as that tasty (but hot!) salsa. The
smell, sight, sound, or thought of food may also stimulate secretion of saliva.
chemicals
superior, inferior
facial, glossopharyngeal
an accessory digestive organ composed of skeletal muscle covered with mucous membrane.
-It is divided into symmetrical lateral halves by a median septum that extends its
entire length, and it is attached inferiorly to the hyoid bone, styloid process of the temporal
bone, and mandible.
tongue
Each half of the tongue consists of an identical complement of
extrinsic and intrinsic muscles
originate outside the tongue (attach to bones in the area) and
insert into connective tissues in the tongue, include the hyoglossus, genioglossus,
and styloglossus muscles
extrinsic muscle
move the tongue from side to side and in and out to maneuver food for chewing,
shape the food into a rounded mass, and force the food to the back of the mouth
for swallowing
-They also form the floor of the mouth and hold the tongue in position.
extrinsic muscle
originate in and insert into connective tissue within the tongue.
They alter the shape and size of the tongue for speech and swallowing.
intrinsic muscles
a retroperitoneal gland that lies posterior to the greater curvature of the stomach.
-connected to the duodenum by 2 ducts
pancreas
main ducts of pancreas
- Duct of Wirsung (Pancreatic Duct)
- Duct of Snatorini (Accessory Duct)
- Ampulla of Vater (Hepatopancreatic Ampulla)
The ___________, is the larger of the two ducts. In most people, the
pancreatic duct joins the common _________ duct from the liver and gallbladder and enters the
duodenum as a dilated common duct called the ____________. The ampulla opens on an elevation of the duodenal mucosa known as the ___________, which lies about 10 cm (4 in.) inferior to the pyloric sphincter of the
stomach. The passage of pancreatic juice and bile through the hepatopancreatic ampulla into
the duodenum of the small intestine is regulated by a mass of smooth muscle surrounding
the ampulla known as the ___________.
The other major duct of the pancreas, the _______________, leads from the
pancreas and empties into the duodenum about 2.5 cm (1 in.) superior to the
hepatopancreatic ampulla
pancreatic duct
bile, ampulla of vater
major duodenal papilla
sphincter of Oddi
accessory duct
are secreted by exocrine cells into small ducts that ultimately unite to
form two larger ducts, the pancreatic duct and the accessory duct.
pancreatic duct
responsible for the alkalinity of the pancreatic juice
sodium bicarbonate
responsible for the completion of digestion of food nutrients in the SI
enzyme
the heaviest gland of the body, weighing about 1.4 kg (about 3 lb) in an average adult.
-the largest organ inside the body
liver
divided into two principal lobes—a large right lobe and a smaller left lobe
liver
a fold of the parietal peritoneum which help suspend the liver in
place
falciparum ligaments
fibrous cord that extends from the liver-umbilicus
-a remnant of the umbilical vein of the fetus
ligamentum teres
help suspend the liver from diaphragm
coronary ligaments
the functional unit of the liver At its center is the central vein, and radiating
out from it are rows of hepatocytes and hepatic sinusoids. Located at three corners of
the hexagon is a portal triad.
lobule
the center of each lobule, surrounded by hepatocytes
central veins
Together, a bile duct, branch of the hepatic artery, and branch of the
hepatic vein
portal triad
From central veins the blood flows into the hepatic veins, which drain
into the inferior vena cava
hepatic veins
radiates out from the central vein of each lobule like spikes of a wheel
hepatic cord
are the major functional cells of the liver and perform a wide array of
metabolic, secretory, and endocrine functions
hepatocytes
highly permeable blood capillaries between rows of hepatocytes that
receive oxygenated blood from branches of the hepatic artery and nutrient-rich
deoxygenated blood from branches of the hepatic portal vein; converge and deliver
blood into a central vein
sinusoids
phagocytes
Kupffer cells
small ducts between hepatocytes that collect bile produced by the
hepatocytes.
bile canaliculi
obtains oxygenated blood
hepatic artery
receives deoxygenated blood containing newly absorbed
nutrients, drugs, and possibly microbes and toxins from the gastrointestinal tract
hepatic portal vein
blood supply of the liver
deoxygenated blood form hepatic portal vein
hepatic sinusoids
central vein
hepatic vein
inferior vena cava
right atrium of the heart
yellow, brownish or live green substance secreted by hepatocytes
*plays a role in emulsification of fats
bile
bile secretion
choleresis
principal bile pigment
conjugated bilirubin
