2.
The mouth is the beginning of the alimentary canal, it
mechanically breaks down food and mixes it with saliva (1)
The mouth is made up of the tongue, palate, teeth, and salivary
glands.
The tongue is composed of two parts:
1.
Body- made up of skeletal muscle fibers, and has a rough
surface which is composed of papillae or taste buds
2.
Root- attached to the hyoid bone, covered with lingual
tonsils(1)
The palate is divided into 2 regions:
1.
Hard palate- forms the roof of the mouth, and consist of
stratified squamous epithelium tissue.
2.
Soft palate- extends posteriorly to form the uvula, consist of
stratified squamous epithelium tissue. (2)
3.
Teeth are composed of a calcified material known
as enamel.(2)
There are 4 types of teeth: 8 incisors, 4 canine, 8
premolars, and 12 molars. (1)
Salivary glands are scattered throughout the oral
cavity. The glands are connected to the oral cavity
by a system of ducts.(2)
Salivary glands are made up of two types of cells:
1.
2.
Serous glands- secrete salivary amylase a digestive
enzyme
Mucous glands- secrete mucus for lubrication
4.
The esophagus is a straight tube that begins at the base
of the laryngopharynx and ends at the stomach. (1)
The esophagus has only one main function, which is to
carry food, liquids, and salvia from the mouth to the
stomach.(3)
The inner most lining of the esophagus is composed of
stratified squamous epithelium for protection and at
the base of this layer lies cuboidal epithelium for
mitosis. (3)
To move food down the esophagus is done by
peristalsis, this is done by muscle contractions around
the esophagus to push the food to the stomach.(1,3)
6.
The stomach’s main function is to receive ingesta and to
change them in such a way that they can be received by
the small intestine. (4)
They stomach is split into 4 main compartments:
1. fundus- balloons above the cardia, acts as short term
storage area, contains fundic glands that produce
hydrochloric acid. (1,4)
2. Cardiac- small portion near the esophageal opening, it
helps eliminate reflux of stomach content back into the
esophagus. (5)
3. Body- main part of the stomach, aids in mechanically
breaking down food by tonus and peristalsis, also
contains fundic glands to chemically break down
food. Mixes the food with gastric juices by tonus &
peristalisis(1,4)
7.
4. Pyloric- separated into 2 portions: 1) the antrumcontains pyloric glands that produce juices that are
alkaline and highly viscous. 2) canal- composed of circular
muscle fibers that grind the chyme. (4)
The lining of the stomach is composed of 4 layers: the
mucosa, the submucosa, muscular coat, & the serosa.(4)
The mucosa is the inner most lining of the stomach and is
made up of columnar epithelium, mucous cells, chief
cells, & parietal cells. The mucous, chief, and parietal cells
release gastric juices.
The submucosa is composed of loose connective tissue
and elastic tissue fibers, permits the mucosa to move
freely with changes in contractility & tonus.(4)
The muscular coat is composed of smooth muscle to
grind food.(4)
8.
9.
The small intestine receives secretions from the
pancreas and liver to aid in the digestion of
nutrients and chyme, and also absorbs the
products of digestion. (1)
The small intestine is composed of 3 segments:
1.
2.
3.
Duodenum- shortest, widest, and most fixed part of
the small intestine. (6)
Jejunum- 8- 10ft. In length, the diameter is greater
than the Ileum.
Ileum- last segment of the small intestine, the walls
are thinner & less vascular
10.
The inner lining of the walls of the small intestine are
made up of circular folds called plicae circulares. These
folds start about 1-2 in. past the pylorus and end in the
lower ileum increasing the surface area for
absorbtion.(6)
The inner lining also has finger like projections called
intesinal villus. The villi are composed of a single layer
of simple columnar epithelium. The epithelial cells
have microvilli that project outward and increase the
surface area by 24-fold. (1,6)
In the microvilli, digestive enzymes are embedded on
the surface that helps break down any food molecules
before absorption. (1,6,7)
13.
The principal function of the colon is that of
solidification of chyme and the storage and
evacuation of waste. (1,7)
The colon can be split into two separate portions
based on their function.
1.
The right portion-which is composed of the cecum and
the ascending colon has an absorptive function. (7)
a)
2.
the ascending colon mainly absorbs water and salt that the
small intestine missed. (7)
The left portion- is composed of the transverse and
descending colon and its main function is storage and
evacuation of waste.
14.
The walls of the colon have the same tissue
make up as other parts of the alimentary canal,
which is the simple columnar epithelium. (1,7)
The columnar epithelium holds an abundant of
goblet cells that secrete mucus for lubrication
and the epithelium lacks the villi and microvilli
due to not much absorption is done in the
colon. (7)
16.
The anal canal is composed of the last 2.5-4 cm of
the large intestine. (1)
Within the lining of the anal canal is the transition
from the columnar epithelium so the intestine to
the stratified squamous epithelium of the skin. (7)
At the distal end of the anal canal lies the anus,
which is enclosed by two sphincter muscles: the
internal and external sphincter. (7).
The internal sphincter is a continuation of the
circular smooth muscle of the rectum which has
involuntary control, and the external sphincter
forms a collar around the anal canal which has
voluntary control.(1,7)
17. 1.
2.
3.
4.
5.
6.
7.
1) Shier, D., Butler, J.B., and R. Lewis. (2012). Hole’s Human
Anatomy and Physiology. 13th Edition. McGraw-Hill Inc.
Boston, MA.
Provenza, Dr. Vincent, and Werner Seibal. Oral Histology.
Philadelphia, PA: Lea and Febiger, 1986
http://bio.rutgers.edu/~gb102/lab_9/904cmesophagus.html
Bockus, Henry L. M.D.. Gastroenterology, vol. 1.
Philadelphia, P.A.: W.B. Saunders Company, 1963.
http://alysculhane.com/horse_care/Vet_Anatomy_Physiol
ogy/digestive_system.htm
Sheehy, Thomas W. M.D., and Martin H. Floch M.D. The
Small Intestine. Harper and Row, 1964.
Bockus, Henry L. M.D.. Gastroenterology, vol. 2.
Philadelphia, P.A.: W.B. Saunders Company, 1963.
