Download 06 General anatomy of the digestive system

General anatomy of
the
Digestive
System
Introduction
 Structure
of the digestive
system


A tube that extends from mouth to anus
Accessory organs are attached
 Functions
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Ingestion
Movement
Digestion
Absorption
Defecation
include
Overview of Digestive
System
Histological Organization


Same basic
arrangement of tissues
from esophagus to anal
canal
Four layers (from
innermost to outermost)
 Mucosa
 Submucosa
 Muscularis
 Serosa
Movement and Mixing of
Digestive Materials


Peristalsis
 Coordinated motion
of two muscular
layers
 Circular muscles
contract, then
longitudinal
muscles
Segmentation

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
Mixing of food
Circular muscles in two
areas contract
Longitudinal muscles
alternately contract & relax
The Oral Cavity
 Structure

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Lined with stratified
squamous epithelium
Lips surround the
opening
Roof is formed from
the hard & soft palate
Tongue dominates the
floor
 Functions


Take in food
Prepare food for
digestion
The
Tongue
 Structure

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Skeletal muscle
covered with mucosa
The lingual
frenulum connects
the tongue to the
floor of the mouth
Surface
 Papillae
 Functions

Maneuvers food
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Salivary
Glands
Found outside mouth
Ducts carry saliva to mouth
3 pairs
 Parotid glands
 Submandibular glands
 Sublingual glands
Saliva
 Functions
 Keeps mucous
membranes moist
 Lubricates food
 Dissolves food
 Begins carbohydrate
digestion
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2 sets
 Deciduous (20)
 Permanent (32)
Held in sockets
Gingiva = gums
Structure
 Crown
 Root
 Neck
Composition
 Dentin
 Enamel
 Cementum
Dental caries
Wisdom teeth
Teeth
The Pharynx and
Esophagus


Food enters the
esophagus from the
pharynx
The esophagus is a
muscular tube behind
the trachea
 Food is moved by
peristalsis from the
pharynx to the
stomach
 Cardiac sphincter
separates esophagus
from stomach
Stomach



The
Stomach
Same 4 basic layers
When the stomach is
empty, the mucosa lies
in large folds
 Rugae
Pyloric sphincter
separates stomach from
small intestine
Histology of the Stomach


Mucosa is simple
columnar epithelium
with goblet cells
Mucosa is folded to
form gastric pits
 Gastric glands
secrete gastric juice
Gastric Gland

Several kinds of
cells produce
substances that
form gastric juice
 Mucus cells
 Chief cells
 Parietal cells
 Enteroendocrine
cells
Functions of the Stomach
 Mechanical

Food reaches pylorus
 Chemical

digestion
Digestion of proteins
 Absorption

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
digestion
No food
Water, electrolytes
Some drugs
Alcohol

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The
Small
Intestine
About 18 feet long
The duodenum
 About 8 inches long
 Common bile duct &
pancreatic duct empty here
The jejunum
 About 8 feet long
 Most digestion occurs here
The ileum
 About 9.5 feet long
 Most absorption occurs here
 Ends in the ileocecal valve
A Villus
Functions of the Small
Intestine
 Chyme
is further broken
down

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
Proteins
Carbohydrates
Fats
 Most
absorption is in the
small intestine
The Large Intestine (Colon)
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About 4.5 feet long
Mesocolon supports
Begins with the cecum
Appendix is attached
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Colon connects to rectum
Rectum connects to anal
canal
Empties to the exterior
through the anus
Histology and Functions of the
Large Intestine

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Mucosa - simple
columnar epithelium
 Completion of
absorption
 Formation of feces
Lots of mucus glands
Expulsion of feces from
the body
Digestion in the Large
Intestine
 Mechanical
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Regulated by the ileocecal valve
Mixing and peristalsis
Mass peristalsis
 Chemical
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Mucus secreted
No enzymes
Bacteria – prepare chyme for elimination
Feces Formation &
Defecation
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Chyme is now solid or semi-solid - feces
Large intestine absorbs any more water and electrolytes from
feces
Defecation
 Mass peristalsis pushes fecal material into rectum
 Rectum stretches
 Defecation reflex
Accessory Organs
 Liver
 Pancreas
 Gall
bladder
The Liver

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Performs many lifesustaining functions
Location – under the
diaphragm on the right
 Connected to the
diaphragm by the
falciform ligament
Divided into lobes
 Right lobe
 Left lobe
 Caudate lobe
 Quadrate lobe
Histology of the Liver

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Outside is a capsule
Composed of tiny
lobules
Each lobule is
surrounded by liver
cells and sinusoids
 Hepatocytes
 Kupffer cells
Bile ducts run between
liver cells
Functions of the Liver
bile – the primary
digestive function
 Produces

Composition
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Water
Bile salts
Cholesterol
Pigments
 Bilirubin
Digestive function

Emulsification of fats
Other Functions
of the Liver
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Absorbs and stores iron, vitamins A, D, E, B7, K
Detoxifies toxins and hormones
Metabolizes proteins, carbohydrates, and lipids
Removes bacteria from the blood
Produces plasma proteins
Removes worn-out and damaged red blood cells
The Gallbladder

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Location – underside of
right lobe of liver
Function – concentrate
and store bile
 Collected from liver
 Hepatic ducts
 Adds bile to
duodenum
 Cystic duct
 Common bile
duct
Gallstones
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The Pancreas
Location – in the
curvature of the
duodenum
Connected to the
duodenum by the
pancreatic duct
Produces pancreatic
juice
Functions
 Exocrine - digestion
of all nutrient groups
 Endocrine – control
blood glucose level