The Digestive System
I. OVERVIEW OF THE DIGESTIVE SYSTEM
The function of the digestive system is to:
1. Break down food
2. Removes solid wastes from body
3. Secretion of water
Although the small intestine is the workhorse of the
digestive system, where the majority of digestion
occurs, and where most of the released nutrients are
released into the blood or lymph, each of the
digestive system organs makes a vital contribution to
this process
II. Walls of the GI tract
The innermost layer of the digestive tract is the mucous, which contains epithelium
(which secrete mucus, digestive enzymes, and hormones) and muscularis mucosa
(which connect glands that empty into the digestive tract).
The middle layer of the GI tract is called the muscularis propria. It is composed of
loose connective tissue containing blood vessels, nerves, glands, and lymphatic
vessels.
The third and most superficial layer (the outermost layer) is called the adventitia.
or muscle layer and consists of two layers of smooth muscles.
fibrous pericardium – also called serous layer, outer fibrous layer
III.
Relationship with other body Systems
Body system
Benefits received by the digestive system
Cardiovascular
To provide nutrients
Endocrine
secretes enzymes into the digestive tract.
Integumentary
gaining its nutrients from the digestive processes that extract nutrients from
the food we consume.
Lymphatic
absorption of fats and fat-soluble vitamins from the digestive system and the
subsequent transport of these substances to the venous circulation.
Body system
Benefits received by the digestive system
Muscular
Your smooth muscles contract and relax as food passes through your body
during digestion.
Nervous
These nerves release chemicals that cause the muscle layer of the GI tract to
either contract or relax, depending on whether food needs digesting.
Respiratory
The respiratory system is primarily used to transport air, while the digestive
system is used to transport fluids (such as water) and solids (such as food
particulates).
Skeletal
The skeletal system helps the digestive system by supporting it, giving it
structure, and allowing it to function.
Urinary
The kidney and urinary systems help the body to eliminate liquid waste
IV. Functions of the Digestive Organs
Organ
Major functions


Mouth




It carries air, food and fluid
down from the nose and
mouth.

carry food and liquid from
your mouth to your stomach.

Food reservoir
Secretes gastric juice
Breaks up food
Performs a limited amount
of absorption
Produces the hormones
Pharynx
Esophagus

Stomach
Chewing
Breathing
Taste
Talking
Saliva



Other functions

Hard pallet
Soft pallet

Breakdown food

Equalizes pressure in the ears
and drains fluid from the ears.

Propel food down

Secretes intrinsic factor

Organ
Major functions
Other functions
gastrin



Small
intestine



Accessory
organs



Large
intestine


Further digests food
Absorbs nutrients
Sends food to larger
intestines
Gets rid of unnecessary
components
Liver filters
Pancreas empties into
duodenum
Gallbladder stores bile
Absorb water
Absorb salt
Gets rid of any waste
products left over
Absorb vitamins
V. Digestive Processes
The processes of digestion include six activities
1.
2.
3.
4.
5.
6.
ingestion
Digestion
motility of the GI wall
absorption
elimination
regulation
Describe each of these processes
1.food is taken in

Makes sure no harmful
bacteria enters

Dule gland

Forming feces
Propels feces

2.breakdown of food into simpler nutrients
3. physically breaks down large chucks into small and moves along tract
4. movement through the GI mucosa into the internal environment
5. excretion of material not absorbed
6. coordination of various functions of the digestive system
VI. The upper alimentary canal
Esophagus , stomach & duodenum as well as three associated accessory organs—
the liver, gallbladder, and pancreas.
VII. Divisions of the stomach
a. Fundus – enlarged portion to the left and above the opening of the esophagus
into the stomach
b. Body – central part of the stomach
c. Pylorus – lower portion
d. cardia – small collar or margin of the stomach at its junction with the esophagus
VIII. Divisions of the small intestine:
duodenum – uppermost division; part to which the pyloric end of the stomach
attaches
jejunum -is the midsection of the small intestine, specialized for the absorption
ileum - The final section of the small intestine.
IX.
Describe the function of the LIVER, GALLBLADDER and Pancreas
Liver filters toxins
Pancreas empties into duodenum
Gallbladder stores bile