Digestive System
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Transcript Digestive System
Digestive
System
Digestive Tract
Also
called alimentary canal
Hollow tube roughly 8 meters in length
Structure of the Wall
Lumen
- hollow center of tube
Mucosa - epithelial layer with mucoussecreting cells
Submucosa - connective tissue layer
rich with blood vessels, lymphatic
vessels, and nerves
Muscular layer - smooth muscle layer
Circular-
adjust lumen diameter
Longitudinal- adjust tract length
Serosa
- outermost layer; secretes
serous fluid
Movements of the Tube
Types of Digestion
Mechanical
Physical
breakdown of food into
smaller pieces
Chemical
Breakdown
of food molecules
into more simple molecules by
enzymes
Mouth
Receives
food
Pushes into the remaining digestive
tract
Includes: lips, teeth, cheeks, tongue,
and palate
Two cavities:
1)
Oral cavity
2)
Vestibule
Space
between palate and tongue
Cavity
between teeth and lips and cheeks
1.
7.
Exit Slip
2.
8.
3.
9.
4.
10.
5.
11.
6.
Cheek and Lips
Cheeks
Contain
muscles used during chewing
Stratified squamous epithelial tissue
inside
Lips
Highly
mobile skeletal muscles rich in
sensory receptors
Aid in sensing temperature and texture
of food
Tongue
Functions:
Keeps
food underneath teeth
Mixes food with saliva
Moves bolus to the back of the
mouth during swallowing
Muscular
structure covered with
mucous membrane
Root is attached to hyoid bone
Attached to floor of mouth by
frenulum
Papillae provide surface friction
and contain taste buds
Palate
Forms
roof of oral cavity
Hard palate
Anterior
Soft
portion
palate
Posterior
Soft
portion; includes uvula
palate raises during
swallowing to close off nasal
cavity
Tonsils
Masses
of lymphatic tissue
Lingual
On the tongue
Pharyngeal
Posterior wall of pharynx;
also called adenoids
Palatine
Back of mouth on either
side of tongue; associated
with palate
Teeth
Two
sets:
1) Primary - 20 teeth
Lost/shed, nonpermanent
2) Secondary - 32 teeth
Permanent, come in after primary teeth are
lost/shed
Function:
Begin
mechanical digestion of food
Anatomy of Tooth
Crown - section above gingiva (gum)
Root -section below gingiva
Enamel - outer covering on crown
Dentin - bone-like substance that fills
most of the tooth
Pulp cavity - connective tissue that
contains blood vessels and nerves
Root canal - tubular extension that
brings blood vessel and nerve to the
pulp cavity
Cementum and periodontal ligament hold tooth in alveolar process of jaw
bone
Salivary Glands
Functions:
Moistens
food
Binds food together
Dissolves food (so it can be tasted)
Cleanses mouth and teeth
Begins digestion of carbohydrates
Two
1)
types of cells
Serous cells
Secretes
2)
serous fluid with enzyme amylase
Mucous cells
Secretes
mucous
Salivary Glands (cont)
3
Types:
1)
Parotid glands:
Largest glands; anterior and inferior to
ear; secrete watery saliva rich in amylase
2) Submandibular:
Located in floor of mouth just inside
lower jaw
3) Sublingual:
Smallest glands; inferior to tongue;
secrete saliva in mucous concentration
Pharynx
Cavity
located posterior to oral cavity
Provides connection to larynx and
esophagus
Three parts:
1)
Nasopharynx - upper potion connecting
to nasal cavity
2) Oropharynx - middle section posterior to
palate
3) Laryngopharynx - lower portion posterior
to larynx opening; leads to esophagus
Swallowing Action
1.
2.
3.
4.
5.
6.
7.
Bolus stimulates sensory receptors in
pharyngeal opening
Soft palate raises- closes nasal cavity
Larynx elevates; epiglottis closes off
larynx
Tongue presses against palate
Longitudinal muscle pull pharynx
towards food
Muscles relax near esophagus to open
the tube
Peristalsis moves food into esophagus
Esophagus
Hollow
collapsible tube
Move food from pharynx to stomach
Passes through diaphragm in opening called
esophageal hiatus
When food reaches opening of stomach, lower
esophageal sphincter opens
Stomach
J-shaped
pouch in
abdomen
Holds
about 1 liter of food
Functions:
Mix
food with gastric juices
Begin protein digestion
Responsible for limited
absorption
Moves food into small intestine
Stomach (cont)
Rugae
Thick
folds of mucosa and submucosa
allow for expansion of stomach wall
Regions
of the stomach
Cardiac - portion near esophagus
Fundic - portion lateral to cardiac where
stomach ballons
Body - main portion of stomach between
cardiac and pyloric
Pyloric - portion near opening to
duodenum
Pyloric Sphincter - thick muscle band
controlling entrance into duodenum
Stomach
Gastric Secretions
Mucosa
is studded with gastric pits
Gastric pits are the opening to gastric
glands
Gastric glands have three types of
secreting cells:
1)
Mucous cells - secrete mucous; helps
prevent stomach from digesting itself
2) Chief cells - secrete pepsinogen
3) Parietal cells - secrete HCl and intrinsic
factor
Gastric secretions
(cont)
As
food enters stomach, mixing actions
occur to breakdown food into chyme
Gastric juices are added
HCl creates acidic environment
Shortens
pepsin
(activates) pepsinogen and makes it
Helps with vitamin B12 absorption
Gastric secretions
(cont)
Limited
absorption of the following occur:
Water
Salts
Alcohol
Lipid-soluble drugs
Chyme
is moved to pyloric sphincter and
pushed through
Control of Gastric
Secretions
Digestion
is controlled by medulla
oblongata
Parasympathetic NS:
Increases gastric secretions
Sympathetic
Decreases gastric secretions
Hormones:
NS:
Gastrin - stimulates production of gastric juices
Cholecystokinin - released when small intestine
fills with food; decreases gastric motility
Review Quiz
Mouth->Stomach
Contains rugae (folds)?
2. Contains lower sphincter and opens to stomach?
3. Mixes food with gastric juices?
4. Provides connection to larynx and esophagus?
5. Begins mechanical digestion of food?
1.
1.
2.
3.
4.
5.
Stomach
Esophagus
Stomach
Pharynx
Teeth
Pancreas
Has
endocrine and exocrine function (Ch
11!)
Nestled in C-shaped curve of duodenum
Pancreatic acinar cells
Secrete
pancreatic juices
Clustered around tubes that eventually empty
into pancreatic duct
Pancreatic
pancreas
Empties
duct run the length of the
the juice into the duodenum
Hepatopancreatic
Controls
emptying
sphincter
Pancreatic Enzymes
Carbohydrates:
Pancreatic
amylase
Breaks polysaccharides into
dissaccharides
Lipids:
Pancreatic
lipase
Breaks fats into glycerol and fatty acids
Nucleic
Acids:
Nucleases
Breaks
nucleic acids into nucleotides
Pancreatic Enzymes
(cont)
Protein:
3
enzymes (break them down into amino
acids)
Trypsin
Chymotrypsin
Carboxypeptidase
Stored
forms
in zymogen granules in inactive
Ex: Trypsin’s inactive form is trypsinogen and is activated
by enterokinase which is secreted by mucosa of
duodenum
Control of Pancreatic
Juices and Enzymes
Parasympathetic NS control:
Acidic chyme:
Stimulate release of pancreatic juices
Stimulates release of secretin into the bloodstream
Stimulates release of pancreatic juice high in
bicarbonate ions
Chyme high in protein and fat
Stimulates release of cholecystokinin into
bloodstream
Stimulates release of pancreatic juice high in
digestive enzymes
Liver
Functions:
Controlling
carbohydrate metabolism
Lipid metabolism
Protein metabolism
Storage
Blood filtering
Detoxification
Secretion of bile
Liver Structure
Connective
tissue divides liver into larger right lobe
and smaller left lobe
Liver is further divided into lobules
Hepatic cells radiate around a central vein
Spaces between the hepatic cells are called
hepatic sinusoids
Liver Structure (cont)
Blood
from digestive track enters sinusoids from
hepatic portal vein
Kupffer cells
Large macrophages (filter out pathogens from sinusoids)
Hepatic
cells
Take out excess nutrients
Blood
enters central vein and continues on its path
back to the heart
What is Bile?
Yellowish-green
cells
Includes:
liquid secreted by liver
Bile salts, bile pigments, cholesterol, and
electrolytes
What does bile do?
Emulsification
Breaks fats globules into smaller droplets
Smaller droplets are easier for lipases to
digest
Enhances
absorption of fatty acids,
cholesterol, and fat-soluble vitamins A, D,
E, and K
Bile (cont)
Sequence
Hepatic
of travel:
cells → Bile canaliculi → Bile
Ductules → Bile duct → Hepatic duct
→ Common hepatic duct →
Hepatopancreatic sphincter →
Duodenum
Gallbladder
Between meals, bile up in common hepatic
duct and into the cystic duct that attaches to it
Bile is backed up into gallbladder that is
attached to the
cystic duct
Gallbladder also
absorbs excess
water in bile therefore
concentrating it
Control of Bile Release
Chyme
high in protein and fat
Stimulates release of cholecystokinin into
bloodstream which stimulates release of
bile
Where
peristalsis reaches
hepatopancreatic sphincter, it relaxes
and bile squirts into duodenum
Small Intestine
Structure
Three
1)
parts:
Duodenum
First part after stomach; forms a Cshape
2) Jejunum
More active than ileum
3) Ileum
Leads to large intestine
Small Intestine
Structure (cont)
Mesentary
Holds loops of intestine to posterior abdominal wall
Supports blood vessels, lymphatic vessels, and nerves
associated with intestine
Greater
omentum
Double fold of membrane covering intestines
Helps wall off infected area
Prevent spread throughout cavity
Structure of
Intestinal
Wall
Wall
has many projections called villi
Increase digestive surface area
Most numerous in duodenum and
first part of
jejunum
Covered with simple columnar epithelium
Have a connective tissue core
Contains blood vessels, a lymphatic vessel
called a lacteal, and nerves
At the base are pockets called intestinal
glands
Small Intestine Secretions
Mucosa
Goblet
cells secrete mucos
Mucous
Secreting
mucous
Intestinal
Secrete
cell in submucosa - secrete alkaline
gland
watery substance
Epithelial
cells of mucosa (all release enzymes)
Peptidase
Sucrase,
maltase, and lactase
Intestinal lipase
Control of Small Intestine
Secretions
Parasympathetic
NS:
Triggers release when intestine wall is
expanded
Other
glands are stimulated by chyme
(both mechanically and chemically)
Sm. Intes. Absorption
Small
intestines = 95% of absorption of nutrients
Absorption follows release of chemicals:
Chemicals mix with chyme to help digestion and
absorption
Bile
Pancreatic
juices
Intestinal enzymes (maltase, lactase, sucrase, trypsin and
chymotrypsin)
Absorption (cont)
Carbohydrates:
Simple
sugars are moved into the blood stream
by diffusion or active transport
Proteins:
Amino
acids are actively transported into the
blood stream
Lipids
Fatty acids and glycerol diffuse into cell of villi
Fatty acids with short chains diffuse into blood
stream
Other are synthesized into fats and packed with
protein (chylomicron) by the ER
These enter the lacteal and are carried to the
blood
Movements of Sm Intes
Mixing
movements
Contractions move chyme from side to side
to mix it
Peristalsis
Movement toward large intestine; very slow
Peristaltic
Forceful contraction if intestine if irritated or
over distended; pushes chyme to large
intestine without much absorption’ leads to
diarrhea
Ileocecal
rush
sphincter
Controls movement between ileum and
cecum; normally closed; open after a meal
Structure of Large
Intestine
Large
diameter lumen
Composed of:
Cecum
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Rectum
Anal Canal
Structure of Large Intestine
Wall
Longitudinal
muscle
occurs in three
bands called teniae
coli
Tension in teniae coli
creates pouches
called haustra in
intestine
Functions of Large Intestine
Mucous
secretion
Protects walls
Bind fecal matter
Controls pH
Absorption
Absorb water and electrolytes in proximal portion
Habitat
for bacteria
Bacteria digest parts of fecal matter that is indigestible
to us;
Synthesize vitamins that are then absorbed
Movements of Large Intestine
Mixing
Same
movements
as small intestine
Peristalsis
Waves
meals
occur only a few time a day; usually after
Defecation
reflex
Feces
are forced into rectum; internal anal
sphincter is relaxed
Pressure
is increased in abdomen which
squeezes the rectum
External anal sphincter is relaxed
Composition of Feces
Water
Undigested
material
Electrolytes
Mucous
Intestinal
Bacteria
Cells
Thumbs up, Thumbs Down
The large intestines houses bacteria such as E coli?
Thumbs up!
2. The liver can absorb excess water in bile.
Thumbs down! Gallbladder
3. The small intestines contains mesentery which helps bind
and support.
Thumbs up!
4. The large intestines helps perform peristalsis and
peristaltic rush.
Thumbs down! Small intestines
5. The liver metabolizes proteins and lipids and filters blood.
Thumbs up!!
1.
Review of Digestive Tract
Digestive Nutrients
Macronutrients
Carbohydrates
Protein
Lipids
Micronutrients
Vitamins
Minerals
Essential
Nutrients
Nutrients that body cannot produce itself
Carbohydrates
Process
of Digestion:
Complex carbohydrate (Polysaccharide) →
Disaccharide → Monosaccharide
Indigestible
carbohydrates:
Ex: Cellulose - provides roughage (or fiber)
to diet
Carbohydrates (cont)
Fructose
and galactose are converted to glucose
by the liver
Excess glucose
Liver converts glucose to glycogen or to fats
Deficiency
of Glucose
Liver converts glycogen, fats, or proteins to glucose
Requirements
for carbohydrates varies depending
upon energy expenditures
More energy = more carbohydrate requirement
Ex: Athletes will consume pasta before event for more
energy
Lipids
Process of Digestion:
Fat → Glycerol + Fatty Acids
Use of Lipid Products:
Used to synthesize glucose
Converted to acetyl CoA and enters
Krebs/Citric acid cycle (of cellular respiration)
Stored in adipose tissue (insulation)
Used in building cellular structures (cell and
organelle membranes)
Used to synthesize some hormones (steroid)
Animation
Protein
Process
Polypeptide → Amino Acids
Uses
of Digestion:
of Amino Acids:
Used to create enzymes
Used to create structural proteins (muscle, etc)
Various other uses
Deaminated (removal of amine group from amino
acid) by liver
Converted
respiration)
into products used in citric acid cycle (cellular
Proteins (cont)
Nonessential
Can be synthesized by body; do not need to be in diet
Essential
amino acids
Cannot be synthesized by body; do need to be in diet
Complete
proteins
Dietary proteins that contain enough of the essential amino
acids
Incomplete
proteins
Dietary proteins that don’t contain enough of the essential
amino acids
Partially
amino acids
complete proteins
Contain enough essential proteins to sustain life but not enough
to promote growth
Vitamins
Organic
compounds requires in small
amounts for normal metabolism
Fat-soluble: A, D, E, and K
Accumulate in tissues and can
lead to overdoses
Water-soluble:
B and C
Excess is often excreted
Minerals
Elements
other than carbon needed for
human metabolism
Concentrated in bones and teeth; parts
of structural components and enzymes;
free-floating ions
Major Minerals: Ca, P, K, S, Na, Cl, and Mg
Trace Elements: Fe, Mn, Cu, I, Co, Zn, F, Cr
Diseases and disorders
Hepatitis:
Inflammation
of liver
Caused by class of viruses (usually)
Names
of hepatitis (A-G) come from virus
Symptoms:
Lack
of appetite
Nausea and vomiting
Low fever and mild headache
Stiff joints and rash
Upper right quadrant pain in
abdomen
Dark/foamy urine
Yellowish skin/sclera of eye
Diseases and disorders
Lactose
Intolerance:
Lactose sugar unable to be broken down
Caused by lack of production of lactase (enzyme
which breaks down lactose)
Symptoms:
Bloating
Intestinal
cramps
Diarrhea
Avoidance:
Avoid
lactose sugar (drink soy/almond milk)
Take lactase pills before eating lactose