Download The digestive system

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Digestive system
Label Digestive Tract
Upper
Respiratory
Tract
Esophagus
Liver
Gall
bladder
Duodenum
Colon
Ileum
Appendix
Rectum
Abdominal aorta
Stomach
Spleen
Pancreas
Small intestine
Digestive System Functions
1. Ingestion:
– occurs when materials enter digestive tract
via the mouth
2. Mechanical processing:
– crushing and shearing
– makes materials easier to propel along
digestive tract
3. Digestion:
– is the chemical breakdown of food into small
organic fragments for absorption by digestive
epithelium
Continue functions
4. Secretion:
– is the release of water, acids, enzymes,
buffers, and salts by epithelium of digestive
tract by glandular organs
5. Absorption:
–
movement of organic substrates, electrolytes,
vitamins, and water across digestive epithelium into
interstitial fluid of digestive tract
6. Excretion:
– removal of waste products from body fluids
Alimentary Canal
•
•
a hollow tube extending from mouth to anus
Four main tissue layers
–
–
–
–
•
Mucosa
Submucosa
Muscularis externa
Serosa
Foods must be broken down to their building
blocks to be absorbed.
– Carbohydrate building blocks: simple sugars
– Protein building blocks: amino acids
– Fat or lipid building blocks: fatty acids and glycerol
Oral cavity
Upper lip
Palate
Uvula
Palatine tonsil
Tongue
Lower lip
Functions of Oral Cavity
• Lubrication:
– mixing with mucus and salivary gland
secretions
• Limited digestion:
– of carbohydrates and lipids
• Sensory analysis:
– of material before swallowing
• Mechanical processing:
– through actions of teeth, tongue, and palatal
surfaces
Tongue
Papillae
Salivary glands
Parotid gland
Sublingual gland
Submaxillary gland
Salivary Glands
• Three pairs – parotid, submandibular, and
sublingual
• Secrete saliva into the oral cavity
• Contains mucus and serous fluids
• The serous component contains salivary
amylase
Teeth
Child
Adult
Tooth
Crown
Enamel
Dentin
Neck
Gum
Pulp cavity
Nerves and
blood vessels
Root
Maxillary bone
Cementum
Alveolar bone
Teeth
• Two sets of teeth are formed.
• The first set consists of 20 deciduous teeth that
begin to appear at 6 months of age and are lost
by 12 years.
• Permanent teeth (32) begin to replace deciduous
teeth around 7 years.
• A typical tooth consists of crown covered with
enamel and root covered with cementum.
• Most of the tooth is bonelike dentin.
• The pulp cavity contains blood vessels and
nerves
Types of Teeth
• Incisors – thin, sharp teeth that are best for
cutting ( 8 total)
• Canines – teeth that aid in tearing ( 4 total)
• Premolars – grinding food ( 8 total)
• Molars – larger and also used for grinding
(12 total)
Teeth
Mastication
• Also called chewing
Chewed Food
• As you chew your food it mixes with saliva
and becomes a round ball called a BOLUS.
Pharynx
• The pharynx is a muscular tube that
provides passage way for both food and
air.
• Regions of the Pharynx
– Nasopharynx
– Oropharynx
– Laryngopharynx
• Food passes through oropharynx and
laryngopharynx to esophagus
Pharynx
Swallowing
• Swallowing has two phases:
– The buccal phase
• voluntary
• begins in the mouth
• the tongue pushes the bolus into the pharynx
– pharyngeal-esophageal phase
• involves the closing off of nasal and respiratory
passages
• conduction of food to the stomach by peristalsis
from the pharynx through the esophagus
Swallowing
When we
swallow food or
fluids, the larynx
is pulled upward
and the epiglottis
tips forming a lid
over the opening
of the larynx
This routes
food into the
esophagus
Swallowing
Peristalsis
Esophagus
• A hollow muscular tube
• About 25 cm long and 2 cm wide
• Conveys solid food and liquids to the
stomach
• Begins posterior to cricoid cartilage
Stomach
Esophagus
Fundus
Body
Pylorus
Pyloric Den
Duodenum
Functions of the Stomach
1. Storage of ingested food
2. Mechanical breakdown of ingested food
3. Disruption of chemical bonds in food
material by acids and enzymes
4. Production of intrinsic factor:
– glycoprotein required for absorption of
vitamin B12 in small intestine
Regions of the Stomach
Cardia
Fundus
Body
Pylorus
Parts of the stomach
Stomach Anatomy
• C-shaped organ
• located on the left
side of the abdomen
beneath the
diaphragm.
• Food enters it through
the cardioesophageal
sphincter
• Food leaves to enter
the small intestine
through the pyloric
sphincter.
4 Layers of the Stomach
• Serous Coat: covers most of the stomach
• Muscular Coat: churns food, three layers of
muscles that run in different directions
• Mucous Coat: protects the inner lining of
the stomach
• Submucosal Coat: connects the muscular
and mucosal layers
Stomach Layers
Mechanical Digestion
• 3 layers of
muscularis layer
– Longitudinal
– Circular
– Oblique
• 3 layers allow
churning and
mixing of food
(mechanical
digestion)
What happens in the
stomach?
• Food enters and gastric secretions is
stimulated by the vagus nerves and by
gastrin
• HCL activates the protein digesting
enzyme pepsin
• Food is mechanically broken down by
churning of stomach muscles
Mucous Coat of Stomach
• Mucous cells secrete mucous that protect
the cells lining the stomach and prevent
the stomach from digesting itself.
Mucous Coat of Stomach
• When the stomach is
empty, the walls are
folded into rugae
(stomach folds), which
allow the stomach to
expand as more food
fills it.
Stomach Digestion
• Peristaltic contractions (mechanical
digestion) mix the bolus with strong
digestive juices that the stomach lining
cells secrete (chemical digestion)
Chemical Digestion
Stomach
• Carbohydrate digestion continues in the
stomach.
• Protein digestion begins in the stomach.
– Pepsinogen and HCL are secreted into the
lumen of the stomach
– HCL converts pepsinogen to pepsin and
contributes to the breakdown of the bolus into
a liquid called chyme.
– Pepsin begins the chemical digestion of
proteins.
Stomach
• Stomach has stretch receptors to indicate
to the brain when stomach is full.
• Food is digested in the stomach for several
hours.
• Chyme is slowly transported from the
pylorus (end of the stomach) through the
pyloric sphincter into the small intestine.
Stomach to small intestine
• Food moves through
the pyloric sphincter
into the small intestine
• Chyme – name given
the partially digested
food that moves into
the SI from the
stomach.
Small Intestine
• Tube-like suspended
from the posterior
body wall by the
mesentery
• Begins at the pyloric
sphincter and ends at
the cecum
• Food digestion and
absorption are
completed here
3 Parts of the small intestine
• The small intestine is
subdivided into the
duodenum, jejunum,
and ileum.
Intestinal Movement
• SI moves food by peristalsis and mixes it
by segmentation
• Peristalsis propels food through the
intestine by waves
• Segmentation mixes food by sequential
movement.
Peristalsis
Segmentation
Duodenum
Duodenum
• The first portion of the
small intestine is the
duodenum where
acidic chyme from the
stomach mixes with
Liver
Bile
Gallbladder
– bile from the liver &
gallbladder
– digestive juices from
the pancreas &
intestine itself.
Stomach
Acid chyme
Intestinal
juice
Pancreatic juice
Pancreas
Duodenum of
small intestine
Chemical Digestion:
Small Intestine
• The pancreas and gland cells of the small
intestine secrete digestive enzymes.
Enzymes include
– Trypsin: protein digestion
– Amylase: carbohydrate digestion
– Lipase: lipid digestion
• Bile is created in the liver and stored in the
gallbladder.
– Bile emulsifies (breaks down) lipids (fats)
• like dish detergent with grease
Pancreas
• Secretion of
pancreatic juice
into the duodenum
• Pancreatic juice
contains enzymes
that digest carbs,
fats, proteins, and
nucleic acids
Liver
• Largest internal organ
• Liver is divided into
two lobes
• Secretes a digestive
fluid called bile,
produced by the
breakdown of dietary
fats and old red blood
cells
• Removes toxins and
wastes from the blood
Liver lobule
Intralobular vein
Hepatocyte
Kupffer cell
Sinusoid
Bile canaliculus
Branch of
hepatic artery
Branch of portal vein
Bile duct
Gall Bladder
• Pear shaped sac on
the inferior surface of
the liver
• Stores bile from the
liver
Digestion Ends
• Once food passes through the duodenum,
digestion is complete.
Jejunum and Ileum
• Chyme then passes into the jejunum and
ileum.
Surface of Small Intestine
• Surface contains
lymph vessels and
small arteries and
veins
• Millions of projections
called villi increase
surface area which
aids in absorption of
nutrients
Food Absorption
• Food molecules enter the bloodstream
through intestinal walls
• Capillaries absorb proteins and
carbohydrates
• Lymph vessels absorb products of fat
digestion that eventually lead to the
bloodstream
Wall of Small Intestine
Intestinal villi
Mucus cell
Capillary system
Epithelial cell
Blood circulation
Lymphatic circulation
Lacteal
Venule
Arteriole
Large Intestine
• Once food has passed through the small
intestine it is mostly indigestible material
and water.
• Food now enters the large intestine
Large Intestine 6 parts
•
•
•
•
•
•
Cecum
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
rectum
Colon
Transverse
colon
Ascending
colon
Descendant
colon
Caecum
Appendix
Sigmoid
Rectum
Anus
Cecum
• Pouch shaped
beginning of the colon
• Appendix is attached
to the bottom of the
cecum
• Apppendix intercepts
pathogenic
microorgamisms and
sometimes fecal
matter
Large Intestine
• The rest of the
large intestine
absorbs water
and turns
chyme into
feces
Rectum
• Final section of
the large intestine
• Empty except just
before and during
defication
Anus
• Contain two
sphincters
which act as
valves
during
defecation
Hernia
• A protrusion of
an organ or
body tissue out
of the body
cavity that it
normally
occupies.
Peptic Ulcer
• Areas of
eroded tissue
in the lining
of the
stomach,
esophagus,
or duodenum
Liver Disease
• Cirrhosis – scarring
of the liver from
alcohol abuse
Hepatitis
• Inflammation of
the liver
Gallstones
• Solid
accumulation of
bile pigment and
cholesterol
Cancer
• Pancreatic and colon
cancer
Hemmorhoids
• Swollen veins in the
lining of the anus
• Can be internal or
external
Nutrients
• Chemical substances
supplied from the
environment that an
organism requires for
survival
Metabolism
• All chemical
breakdown
(catabolic) and
building
reactions
(anabolic)
needed to
maintain life
Sources of major nutrients
•
•
•
•
•
Carbohydrates
Lipids
Proteins
Vitamins
Minerals
Carbohydrates
• Organic
compounds which
include sugars
and starches
• One of the body’s
main sources of
energy
Lipids
• Organic compounds
that include fats, oils,
and fatlike
substances.
• The body’s other main
source of energy
Proteins
• Long chains of amino
acids that help with
cell growth and repair
Vitamins
• Organic compounds
required in small
amounts.
• Fat-soluble vitamins
are A, D, E, and K
• Water-soluble
vitamins are B and C
Minerals
• Inorganic
elements that are
essential in
human
metabolism.
• Most
concentrated in
bones and teeth
and make up
about 4% of our
body weight