Gastrointestinal Tract 1

Question 1

What is included in the gastrointestinal tract?

Answer 1

• Oral Cavity( Mouth, teeth and salivary glands.
• pharynx
• esophagus
• stomach
• small intestines
• large intestines
• rectum and anal canal.

Question 2

What is the oral cavity bounded by?

Answer 2

-The lips and the palatoglossal folds.

Question 3

What is the Oral mucous?

Answer 3

Epithelium (Generally nokertinized stratified squamous epithelium). The epithelium is always a wet membrane due to underlying small accessory salivary glands.

Question 4

What constitutes the connective tissue of the oral cavity?

Answer 4

A thin superficial layer of loose connective tissue (Lamina or Tunica propria) with papillae interlocking with epithelial pegs and a deeper layer with coarse collagen bundle (Submucosa) containing numerous small salivary glands.

Question 5

What tissue underlying the submucosa?

Answer 5

It may be skeletal muscles (Cheeks, soft palate and lips) or bone (Hard Palate and gingiva.

Question 6

What is the function of the tongue?

Answer 6

Its a structure of digestion and phonation.

Question 7

What does the tongue consist of?

Answer 7

Extrinsic and intrinsic muscle skeletal muscle fibers.

Question 8

What do the tongue intrinsic muscles consist of?

Answer 8

Superior and inferior longitudinal fibers, vertical and transverse fibers.

Question 9

What covers the tongue?

Answer 9

A layer of nonkeratinized stratified squamous epithelium connective tissue then the lamina propria which is found between the epithelium and intrinsic muscles.

Question 10

What is distinct about the anterior two-thirds of the dorsal (upper) surface of the tongue?

Answer 10

It has many small surface projection called papillae

Question 11

What does the posterior 1/3 of the dorsal surface contains?

Answer 11

The lingual tonsils.

Question 12

What are the filiform papillae?

Answer 12

Finger like in shape, has no taste buds; their epithelial cells may be partially kertinized. they scrape food off the surface of the tongue.

Question 13

Fungiform papillae?

Answer 13

Shaped like muschrooms. Their epithelial surface is not kertinized. taste buds may be scattered on their epithelial surface.

Question 14

Circumvallate papillae?

Answer 14

Are the posterior boudnries of the anterior 2/3 of the tongue and are arranged in a V shaped line anterior to the sulcus terminalis. They are large about 6-12 in total. submerged into the surface of the tongue.

Question 15

What is Enamel?

Answer 15

Most calcified tissue in the body (95-98%). Enamel matrix is secreted by ameloblasts and subsquently cacified through the formation of enamel rods bound together by interrod enamel.

Question 16

Can enamel be replaced?

Answer 16

No enamel cannot be replaced beacuse the ameloblasts die at tooth eruption.

Question 17

What is Dentin?

Answer 17

Calcified tissue (About 70%) secreted by odontoblasts.

Question 18

How is dentin initially secreted?

Answer 18

Its initially secreted in an unminerlized state called predentin.

Question 19

What is cemmentum?

Answer 19

Covers the dentin of the root of the tooth. Similar to bone but it lacks haversian systems and blood vessels.

Question 20

What is Tooth pulp?

Answer 20

Loose connective tissue with odontoblasts, fibroblasts and thin collagen fibers and ground substance.

Question 21

What is periodontal ligament?

Answer 21

Dense connective tissue forming the periosteum of the alveolar bone and attaching to the cemmentum of the tooth.

Question 22

What is the function of periodontal ligament?

Answer 22

The periodontal ligament allows some movement of the tooth and it absorbs some of the pressure that would be other exerted on the bone during mastication. The periodontal ligament has a relatively high rate of protein turnover.

Question 23

What is the pharynx?

Answer 23

Derived from the foregut and divided into 3 regions. The nasopharynx, the oropharynx (which starts at the palatoglossal folds) and the laryngopharynx.

Question 24

What are the four concentric tubes (layers) that the GI tract created from starting at the level of the esophagus to the anal canal?

Answer 24

• The mucosa
• Submucosa
• Muscularis externa
• Serosa

Question 25

What composes the levels of mucosa and submucosa?

Answer 25

- The mucosa: the innermost layer consisting of epithelium with underlying connective tissue - The submucosa: the layer of connective tissue surrounding the mucosa.

Question 26

What composes the muscularis externa layer and the serosa?

Answer 26

- The muscularis externa: the layer of muscle surrounding the submucosa - The serosa: the layer of visceral peritoneum. (Layer of simple squamous epithelium with connective tissue) surrounding the abdominal organs or the "Adventitia".

Question 27

What is the adventitia?

Answer 27

Layer of connective tissue surrounding organs outside the abdominopelvic cavity (for example; esophagus, portions of rectum and anal canal)

Question 28

What is the mucosa generally composed of?

Answer 28

Simple columnar epithelium with an underlying connective tissue layer known as the lamina propria.

Question 29

What are the functions of epithelium?

Answer 29

- Promotion of digestion of food within the lumen of he GI tract by secretion of enzymes and ions that regulates PH - Absorption of digestion products - secretion of protective mucus - Secretion of hormones with localized actions (Enteroendocrine cells)

Question 30

What is the lamina propria and what does it contain?

Answer 30

- Loose connective tissue supports the epithelium. it contains: - Small blood and lymphatic vessels (known as lacteals in small intestines) - Glands, lymphoid tissue and smooth muscle cells - Diffuse lymphoid tissue composed of macrophages, lymphocytes, plasma cells and granulocytes that participate in local immune mechanisms.

Question 31

What is the muscularis mucousa and what does it separate?

Answer 31

layer of smooth muscle separates the lamina propria from the submucosa. this layer layer starts in the upper part of the esophageus but forms a complete layer only at the level of the stomach. The actions of smooth muscle cells in the muscularis mucosa produce some movement of the mucosa without involving the submucosa and muscularis externa.

Question 32

What is the submucosa?

Answer 32

a layer of loose connective tissue that contains larger diameter colagen fiber than does the lamina propria. -Contains larger diametere blood vessles. These vessels supply and drains the lamina propria vessels.

Question 33

What is the submucosal or meissner's plexus?

Answer 33

Contains a nerve plexus of autonomic neurons. Innervates the muscularis musocsae and certain sensory and secretory epithelial cells -It provides the neural regulation for movement and local hormonal secretions of the epithelial glands.

Question 34

What is the myenteric plexus or Auerbach's plexus?

Answer 34

Its another plexus that is supported by a thin layer of loose connective tissue between the muscle. The activity of the neurons in this plexus initiate and coordinate the contractile of the circular and longitudinal layers of smooth muscle.