Finals - Digestive system Flashcards
digestive system provides the body with
nutrients, water and electrolytes essential for health
the organs of the digestive system function
ingest, digest, and absorb food and
eliminate the undigested remains as feces
digestive system consists of
a hollow tube (alimentary
canal) extending from the mouth to the anus, into which various
accessory organs or glands empty their secretions.
digestive organ system are divided into two groups
- alimentary canal
2. accessory digestive organs
alimentary canal
-Mouth, pharynx, and
esophagus
-Stomach, small intestine, and
large intestine (colon)
accessory digestive organs
-Teeth and tongue
-Gallbladder, salivary glands,
liver, and pancreas
the digestive processes of digestive system
- Ingestion
- Propulsion
- Mechanical digestion
- Chemical digestion
- Absorption
- Defecation
• The walls of the ventral body cavity and the outer surfaces of the
organs it contains are covered with
h an thin, double-layered membrane
called the serosa (serous membrane)
parietal serosa
: the part of the
membrane lining the cavity walls
viceral serosa
: the part of the
membrane covering the external surface
of the organs within the cavit
function of serosa
produce a thin
lubricating fluid that allows the viceral
organs to slide over one another or to rub
against the cavity wall without friction.
• They also compartmentalize the various
organs so that infection of one organ is
prevented from spreading to others
peritoneum
: the serosa lining the the abdominopelvic cavity and
covering its organs.
visceral peritoneum
surrounds digestive organs
parietal peritoneum
lines the body wall
peritoneal cavity
space between the visceral and parietal peritoneum that contains a lubricating serous fluid
mesentery
a double layer of peritoneum…a sheet of two serous
membranes fused back to back that extends to the digestive organs
from the body wall.
mesentery function
Holds organs in place
-Sites of fat storage
-Provides a route for circulatory vessels and nerves
Dorsal mesenteries > ventral mesenteries
the two ventral mesenteries are?
falciform ligament
lesser omentum
falciform ligament
binds the anterior aspect of the liver to the
anterior abdominal wall and diaphragm
lesser omentum
runs from the liver to the stomach and
duodenum.
the dorsal mesenteries are
greater omentum
mesentery (proper)
transverse mesocolon
sigmoid mesocolon
greater omentum
connects the greater curvature of the stomach
to the posterior abdominal wall
mesentery (proper)
sheet that fans
interiorly from the posterior
abdominal to support the jejunum and
ileum.
transverse mesocolon
holds
transverse colon to posterior
abdominal wall
sigmoid mesocolon
connects
sigmoid colon to posterior pelvic wal
the four tissue layers of the alimentary canal
Mucosa → Submucosa → Muscularis externa → Serosa
mucosa (mucous membrane)
innermost layer containing three
sublayers: a) a lining epithelium, b) a lamina propria, and c) a
muscularis mucosae
mucosa
lining epithelium
lamina propria
muscularis mucosae
lining epithelium
: abuts the lumen of the alimentary canal and
functions to absorb nutrients and secrete mucus
lamina propria
a: a loose areolar or reticular C.T. that nourishes the
lining epithelium and absorb digested nutrients.
- Contains MALT
muscularis mucosae
a thin
layer of smooth muscle that
produces local movements of
the mucosa
muscularis mucosae function
-Dislodges food particles
that become embedded in
the mucosa
submucosa
: a layer of C.T. containing major blood and lymphatic
vessels and nerve fibers
the vascular network of submucosa
sends branches to all other layers of the wall
the C.T of submucosa
is a “moderately dense” C.T….an intermediate between loose
areolar and dense irregular C.T.
muscularis externa (muscularis) consists of
of two layers of smooth
muscle that are responsible for peristalsis
the two layers of muscularis externa
a) inner circular layer: squeezes the gut tube
b) outer longitudinal layer: shortens the gut tube
-In some places, the circular layer thickens to form sphincters that act
as
valves to prevent the backflow of food from one organ to the next.
serosa
(visceral peritoneum): the protective outermost layer;
areolar C.T. covered by single layer of squamous epithelial cells
mouth (oral cavity)
where food enters the alimentary canal and is
chewed, manipulated by the tongue, and moistened with saliva.
Mouth
- Mucosa-lined cavity bounded
by the lips, cheeks, palate, and the
tongue.
oral orifice
anterior opening
poseteriorly the mouth borders?
the fauces of the oropharynx
the mouth is divided into?
where food enters the alimentary canal and is
chewed, manipulated by the tongue, and moistened with saliva.
Mouth
- Mucosa-lined cavity bounded
by the lips, cheeks, palate, and the
tongue.
vestibule
: the slit between the
teeth and the cheeks (or lips)
oral cavity proper
the region
of the mouth that lies internal to
the teeth.
Lips (labia) and cheek
h help keep food inside the mouth
during chewing, are composed of a core of skeletal muscle covered
by skin
lips
: thick flaps extending
from the inferior boundary of the
nose to the superior boundary of
the chin
red margin
in: the region of the lip
where lipstick is applied…a
transition zone where the skin
meets the oral mucosa
labia frenulum
a median fold
that connects the internal aspect
of each lip to the gum
palate
the roof of the mouth; has two distinct parts…
- hard palate
- soft palate
hard palate
the anterior bony
part that forms a rigid surface
against which the tongue forces
food during chewing
soft palate
the posterior
muscular part that is a mobile flap
that rises to close off the
nasopharynx during swallowing
uvula
projects downward from
the free edge of the soft palate
the soft palate is anchored to?
the tongue by the palatoglossal
arches and to the wall of the oropharynx by the palatopharyngeal
arches.
tongue constructed of
f interlacing fascicles of skeletal muscle
fibers.
functions of tongue
- Grips food and constantly repositions it between the teeth. - Mixes the food with salvia and form it into a compact mass called a bolus. - During swallowing…the tongue moves posteriorly to push the bolus into the pharynx. - Houses most of the tastebuds - In speech, the tongue helps form some consonants (k, d, t, and l)
lingual frenulum
a fold of mucosa on the undersurface of the
tongue that both secures the tongue` to the floor of the mouth and limits
its posterior movements.
three major types of peglike
projections that the mucosa of the superior surface of the tongue bears
filiform papillae
fungiform papilae
circumvallate papillae
filiform papillae
: give the tongue roughness and provide friction
fungiform papillae
: scattered widely over the tongue and give it a
reddish hue, contains taste buds
circumvallate papillae
V-shaped row in back of tongue, contains
taste buds
the teeth (denitions)
) tear and grind the food, breaking it into
smaller fragments.
• Humans have two sets of teeth…
primary denition (deciduous teeth)
20 total that erupt at
intervals between 6 and 24
months
permanent teeth
enlarge and develop causing the root of deciduous teeth to be resorbed and fall out between the ages of 6 and 12 years; all but the third molars (“wisdom teeth”) have erupted by the end of adolescence; there are usually 32 permanent teeth
teeth are classifed according to ?
their shape and function
- incisors
- canines
- premolars (bicuspid and molars
incisors
: chisel-shaped teeth adapted for cutting or nipping
canines
conical or fanglike teeth that tear or pierce
c) Premolars (bicuspids) and molars
have broad crowns with
rounded tips and are best suited for grinding or crushing
during chewing (mastication)
upper and lower premolars and
molars lock together generating crushing force
saliva
a mixture of water, mucus, and enzymes
function of saliva
a) moisten, dissolves food, binds food together (bolus)
b) aids in digestion of starch
c) prevents tooth decay by neutralizing acids
d) contains bactericidal enzymes, antiviral substances, and
antibodies to kill harmful oral microorganisms
e) contains proteins to help growth of beneficial bacteria
all salivary glands are
are compound (branched ducts) tubuloalveolar (secretory unit shape) glands:
intrinsic salivary glands
s: scattered within mucosa of tongue,
palate, lips, and cheeks; keep mouth moist at all times
extrinsic salivary glands
: lie external to the mouth but have ducts
that open to the mouth
parotid glands
exterior
to ear, between masseter
and skin
submandibular jglands
at medial surface of
mandible, anterior to
mandibular angle
sublingual glands
in
floor of oral cavity,
inferior to tongue
• From the mouth, the oropharynx and laryngopharynx allow passage
of
f food and fluids to the esophagus and air to the trachea.
the pharynx is lined with
- Lined with stratified squamous epithelium and mucus glands
- Has two skeletal muscle layers; Inner longitudinal and outer pharyngeal constrictors
esophagus
Muscular tube (~10 inches) that joins the laryngopharynx to the stomach; travels through the mediastinum and pierces the diaphragm; joins the stomach at the cardiac orifice -The empty esophagus is folded longitudinally and flattened
esophagus glands and muscularis
Glands secrete mucus as a bolus moves through the esophagus -Muscularis changes from skeletal (superiorly) to smooth muscle (inferiorly)
stomach
Site where food is churned into chyme (the liquid substance found in the stomach; consists of partially digested food, water, hydrochloric acid, and various digestive enzymes). ~4 hours
stomach functions
-Protein digestion begins (Secretes
pepsin)…functions under acidic
conditions
-Hydrochloric acid: a strong acid
that destroys many harmful bacteria
in the food
location of the stomach, cardiac region (cardia), fundus, Body
stomach: lies in upper left quadrant of peritoneal cavity
- Cardiac region (cardia): surrounds the cardiac orifice at the junction
with the esophagus
Fundus: dome-shaped region immediately inferior to diaphragm
body
- Body: midportion of the
stomach
pyloric region
made up of
the antrum (cave) and canal
which terminates at the
pylorus
pylorus
is continuous
with the duodenum (1st part
small intestine) through the
pyloric sphincter
rugae
greater curvature
lesser curvature
- Rugae: longitudinal folds of mucosa; allow distension
- Greater curvature: entire extent of the convex lateral surface
- Lesser curvature: concave medial surface
small intestine
Longest portion of the alimentary canal (short people: 2.7-5 meters, tall people: 6-7 meters). -Site of most enzymatic digestion and absorption
three subdivision of small intestine
: duodenum
(5%), jejunum (40%), and
ileum (55%)
duodenum
chyme passes through the pyloric valve and enters the
duodenum (~10 inches long).
-Receives digestive enzymes from the pancreas and bile from the liver
and gallbladder
main pancreatic duct and common bile duct enter the wall of the duodenum where they form a bulb called
hepatopancreatic
ampulla.
The ampulla opens into the duodenum via a mound called
the
major duodenal papilla.
The wall of the small intestine has three structural modifications that
amplify its absorptive surface
) Circular folds (plicae circulares)
b) Villi
c) microvilli
a) Circular folds (plicae circulares):
1cm tall transverse ridges of the
mucosa and submucosa.
-Force the chyme to spiral through the intestinal lumen…slowing its
movement.
billi
1 mm tall fingerlike projections of the mucosa that are
covered by a simple columnar epithelium made up primarily of
absorptive cells (enterocytes) specialized for absorbing digested
nutrients.
-Contains lacteals and blood capillaries
microvilli
tiny projections of absorptive cell’s at the apical surface
that contain enzymes
Total surface area of small intestine = 200 m
absorptive cells
uptake digested nutrients…contain many
mitochondria.
- Contain an abundant amount of endoplasmic reticulum…assembles
newly absorbed lipid molecules into lipid-protein complexes called
chylomicrons, which enter the lacteal capillaries
goblet cells
secrete mucus that lubricates chyme and forms a
protective barrier that prevents enzymatic digestion of the intestinal
wall
Enteroendocrine cell
cells of the
duodenum that secrete hormones:
a) Cholecystokinin
b) secretin
cholecystokinin
signals the
gallbladder to release stored bile and the
pancrease to secrete its digestive
enzymes
secretin
signals the pancreatic ducts
to secrete a bicarbonate-rich juice to
neutralize the acidic chyme entering the
duodenum
Intestinal crypts
mucosa between the
villi that contain epithelial cells that
secrete intestinal juice…a watery liquid
that mixes with chyme
epithelial stem cells divide in and renew ?
- Epithelial stem cells divide in the crypts and renew the mucosal
epithelium by moving continuously into the villi.
large intestine main function
\: absorb water and electrolytes (~12-24 hours). -Digested residue contains few nutrients -Small amount of digestion by bacteria -Mass peristaltic movements force feces toward the rectum
• Large intestine: 1.5 meters
-Subdivided into:
- Cecum,
- appendix,
- colon,
- rectum,
- anal canal
The large intestine exhibits three special features:
teniae coli
haustra
epiploic appendages
teniae coli
three longitudinal strips, spaced at equal intervals
around the circumference of the cecum and colon.
-Thickenings of the longitudinal layer of the muscularis externa
haustra
puckered sacs of the large intestine
epiploic appendages
fat-filled pouches of visceral peritoneum that
hang from the intestine…no known function.
cecum
a pouch connected to the ileum and the ascending colon of
the large intestine
ileocecal valve
a sphincter muscle situated at the junction of the small intestine (ileum) and the large intestine. -It regulates the flow of chyme into the bowels
vermiform appendix
tube connected to the cecum; neutralizes
pathogens.
-Removed: the appendix is a vestigial structure with no absolute
purpose
colon
A storage tube for solid wastes. The main function of the
colon appears to be extraction of water and salts from feces.
-Divided into distinct segments: Ascending, transverse, descending,
and sigmoid colon
rectum
the final straight portion of the large intestine, terminating
at the anus
anal canal
the last subdivision of the large intestine. The external
opening of the rectum
liver
Largest gland in the
body (~3 lbs)
-Performs over 500 functions
functions of liver
\: It plays a major role in… metabolism, glycogen storage, decomposition of red blood cells, plasma protein synthesis, and detoxification.
liver digestive function
…produces bile; an alkaline compound
which aids in digestion, via the emulsification of lipids.
most of the liver is covered with a?
a layer of visceral peritoneum…
however the superior part (bare area) is fused to the diaphragm and is
devoid of peritoneum.
the liver has four lobes
left, right, caudate, quadrate lobes.
falciform ligament
mesentery that separates the right and left lobes
anteriorly and binds the liver to the anterior abdominal wall.
porta hepatis
area near the center of the visceral surface where most
of the major vessels and nerves enter and leave the liver.
-Enter via the porta hepatis:
-Enter via the porta hepatis:
a) The right and left branches of the hepatic portal vein, which carry nutrient-rich blood from the stomach and intestines b) The right and left branches of the hepatic artery carrying oxygen-rich blood to the liver
-Exit via the porta hepatis:
a) The right and left hepatic ducts, which carry bile from the
respective lobes exit and fuse to form the common hepatic duct
gallbladder
rests in a recess on the inferior surface of the right lobe
and is the storage place for bile
-Thin-walled, green muscular sac on the ventral surface of the liver,
stores and concentrates bile by absorbing its water and ions, releases
bile via the cystic duct, which flows into the bile duct
Cystic duct, hepatic duct, and common bile duct:
-Bile, which is synthesized in the liver, is carried to the right and left
hepatic ducts, which converge to form the common hepatic duct.
There it enters the superior end of the common bile duct and either
empties into the second part of the duodenum, or enters the cystic
duct to be stored in the gallbladder.
Pancreas:
-Exocrine function:
Acinar cells make, store, and secrete pancreatic enzymes which are activated in the duodenum and breaks down food.
pancreas
-Endocrine function:
produces the hormones
insulin and glucagon which
regulates blood sugar
• Pancreas: Pancreatic duct
-A duct joining the pancreas to the common bile duct to supply
pancreatic juices which aid in digestion provided by the “exocrine
pancreas”.
