Download Digestive System

Digestive System
Zahraa Ahmed
Buthaina Al-Ezzi
The digestive system
• The digestive system is a long hollow tube or tract
that starts at the oral cavity and terminates at the
anus.
• The system consists of the oral cavity, esophagus,
stomach, small intestine, large intestine, rectum,
and anal canal.
• The oral cavity consists of the mouth and its structures,
which include the tongue, teeth and major and minor
salivary glands, and tonsils.
Major functions of the digestive system include
1.transport of ingested water and food along the
alimentary canal
2.secretion of fluids, electrolytes, and digestive
enzymes
3.digestion and absorption of digested products; and
excretion of indigestible remains.
In the oral cavity, food is ingested, masticated
(chewed), and lubricated by saliva for swallowing.
Because food is physically broken down in the oral
cavity, this region is lined by a protective, non
keratinized, stratified squamous epithelium,
The Lips
• The oral cavity is formed, by (the lips and cheeks.) The
lips are lined by a very thin skin covered by a stratified
squamous keratinized epithelium. Blood vessels are close
to the lip surface, imparting a red color to the lips. The
outer surface of the lip contains hair follicles, sebaceous
glands, and sweat glands. The lips also contain skeletal
muscle called orbicularis oris M
• the outer lining changes to a thicker, stratified squamous
non keratinized oral epithelium. Beneath the oral
epithelium are found mucus-secreting labial glands.
The lip structure:
1- The external surface
2- The internal surface
3- the vermilion margin (red
margin)
The external surface of the lip:
is covered with thin skin formed
of epidermis and dermis with the associated hair
follicles, sebaceous glands and sweat glands.
underbeneath the skin, bundles of circular skeletal
muscle of the orbicularis oris m.
The internal surface of The lip:
Lines by mucous membrane which is formed of:
stratified squamous non-keratinized epithelium (thicker
than that of epidermis of the external surface)
lamina propria : formed C.T. contain; Blood
vessels, lymphatic Vessels , nerves and group of labial
minor salivary glands (mucous acini)
The Vermilion (red) margin of the lip:
is continuous with the thin skin of the ext. surface of the lip
covered by modified skin characterized by : transparent
epithelium; formed of stratified squamous non-keratinized
epithelium without hair follicles, sebaceous glands or sweat
glands. deeply and vascular dermal papillae (giving the red color
of the lip margin), highly supplied with nerves.
The Tongue
• The tongue is a muscular organ located in the
oral cavity. The core of the tongue consists of
connective tissue and interlacing bundles of
skeletal muscle fibers.
• The distribution and random orientation of
individual skeletal muscle fibers in the tongue
allows for increased movement during chewing,
swallowing, and speaking.
Papillae
• The epithelium on the dorsal surface of the tongue is
irregular or rough owing to numerous elevations or
projections called papillae.
• All papillae on the tongue are covered by stratified
squamous epithelium that shows partial or
incomplete keratinization. In contrast, the
epithelium on the ventral surface of the tongue is
smooth.
• There are four types of papillae on the tongue:
filiform, fungiform, circumvallate, and foliate.
Taste Buds
• Located in the epithelium of the foliate and fungiform papillae, and
on the lateral sides of the circumvallate papillae, are barrel-shaped
structures called the taste buds.
• The free surface of each taste bud contains an opening called the
taste pore
• The main functions of the tongue during food processing are to
perceive taste and to assist with mastication (chewing) and
swallowing of the food mass, called a bolus.
Papillae
1. Filiform The most numerous and smallest papillae
on the surface of the tongue are the narrow, conical
shaped filiform papillae. They cover the entire
dorsal surface of the tongue.
2. Fungiform Papillae: Less numerous but larger,
broader, and taller than the filiform papillae are the
fungiform papillae.
• These papillae exhibit a mushroom-like shape and
are more prevalent in the anterior region of the
tongue.
3.Circumvallate papillae are much larger than the
fungiform or filiform papillae. Eight to 12
circumvallate papillae are located in the posterior
region of the tongue.
• These papillae are characterized by furrows that
completely encircle them. Numerous excretory ducts
from underlying serous (von Ebner’s) glands,
located in the connective tissue,
4. Foliate Papillae
are well developed in some animals but are
rudimentary or poorly developed in humans..
Teeth
are a major component of the oral cavity and are essential for the
beginning of the digestive process.
Teeth are embedded in and attached to the alveolar processes of
the maxilla and mandible.
Teeth are made up of three specialized tissues:
• Enamel
a hard, thin, translucent layer
of acellular mineralized tissue
that covers the crown of the tooth.
Dentin, it lies deep to the enamel
in the crown and cementum in the root.
Its unique tubular structure and
biochemical composition support the
more rigid enamel and cementum
overlying the surface of the tooth.
• Cementum, a thin, pale-yellowish layer of bonelike calcified tissue covering the dentin of the root of
the teeth.
Cementum is softer and more permeable than dentin
and is easily removed by abrasion when the root
surface is exposed to the oral environment
Dental pulp
The dental pulp (also called "the nerve" of the tooth)
is the central part of the tooth and is filled with soft
connective tissue that contains blood vessels and
nerves.