Digestive System (Final Exam)

Question 1

What is the lining epithelium of the GI tract?

Answer 1

Stratified squamous epithelium from lips to nonglandular stomach.
Simple columnar in glandular stomach and intestine.

Question 2

What is the oral cavity? What is it composed of? What do ruminants have that is special here?

Answer 2

Lips, cheeks, palate, pharynx, tongue.
Lamina propria of CT (submucosa missing)
Has labiae and buccal salivary glands and tonsils.
Dental pad in ruminants (keratinized)

Question 3

Describe the tongue.

Answer 3

Covered by mucosa (lamina propria = loose CT, gland); Submucosa is missing!
Dorsal/upper side is keratinized and surface is irregular due to present of papillae (mechanical and gustatory)
Some papillae have taste buds
Skeletal muscle arranged in 3 DIRECTION - move tongue in all directions

Question 4

What are the cells that form the hard structures of the tooth?

Answer 4

Ameloblasts –> Enamel (covers external surface)
Odontoblasts –> Dentin (beneath enamel)
Cementoblasts –> Cementum

Question 5

What are the soft tissues of the tooth?

Answer 5

Tooth pulp - loose CT and nerves (root mesenchyme is derived from neural crest cells)
Periodontal Ligament - from fibroblasts

Question 6

Describe tooth development.

Answer 6

Odontoblasts cover surface of mesenchymal papilla and produce predentin and dentin
Ameloblasts are tall columnar cells that will produce enamel

Question 7

What is the general organization of digestive organs?

Answer 7

Mucosa - inner epithelium, middle lamina propria (loose CT of mucous membrane with cells of immune system), this outer muscularis mucosae (smooth muscle of mucosa)
Submucosa (+/-) - not in tongue
Muscularis - inner circular, outer longitudinal
Tunia Serosa (mesothelial lining) or Adventitia (no mesothelium) - peritoneum, pleural lining

Question 8

Describe the Tunica Submucosa

Answer 8

Loose CT, loose than lamina propria mucosae
Facilitates motility of mucosa
May contain glands, vessels, nerve plexus (submucous plexus of Meissner) and lymphatic nodules

Question 9

Describe the Tunica Muscularis

Answer 9

Smooth or skeletal muscle
Usually 2 layers: inner circular, outer longitudinal
Control lumen size, motility of tube
Contains myenteric plexus (Auberbach), vessels, nerves, nerve cell bodies in ganglia or on plexus

Question 10

Describe Tunica Serosa/Adventita

Answer 10

T. Serosa = mesothelium, loose CT +/- adipose tissue
T. Adventitia - loose/dense CT only, no mesothelium
Most external tunic.
If associated with pleural, pericardial or peritoneal cavities is composed of mesothelium and underlying CT

Question 11

Where does Tunica Adventitia occur in the GI tract?

Answer 11

portion of esophagus, rectum
Also vagina, bronchi, trachea
Where passing through mediastinum, body wall or the neck.

Question 12

Describe the esophagus.

Answer 12

Mucous glands in submucosa.
May have lamina muscularis mucosae
Heals poorly
Tunica muscularis may be skeletal or combo of skeletal/smooth
Tunica adventita is outermost in cervical and thoracic regions.

Question 13

What are gastric pits?

Answer 13

Invaginations of lining epithelium

Question 14

What type of glands is the cardiac region composed of? The fundic region?

Answer 14

Cardiac Region - mostly of mucous glands

Fundic Region - proper gastric glands (parietal and chief cells)

Question 15

What are the 3 types of gastric glands?

Answer 15

1. Mucous Glands
2. Proper gastric glands
3. Pyloric Glands

Question 16

Describe the cardiac gland region of the stomach.

Answer 16

Near the esophageal stomach junction composed mainly of mucous glands and a few parietal cells

Question 17

Describe the fundic region of the stomach

Answer 17

Composed of parietal (secrete hydrochloric acid, acidophilic, secrete intrinsic factor for vitamin B12 absorption) and chief cells/peptic cells (produce pepsinogen, basophilic, secrete chymosin (rennin in ruminants) in infants - curdles milk)

Question 18

Describe the pyloric region of the stomach.

Answer 18

Has mucous glands and G cells that produce GASTRIN

Question 19

Describe the small intestine.

Answer 19

Lined by simple columnar epithelium
Goblet cells increase aborally
Has plicae, microvilli, villi (increase SA)
VILLI only in Small Intestine
At base of villi = CRYPTS of LIEBERKUHN
Lacteals at center of villi
Duodenum has Brunners Glands (duodenal glands) in submucosa

Question 20

What are lacteals?

Answer 20

Blind-ended lymphatic vessels in intestinal villi.
Chyle found in lacteals is filtered through intestinal lymph nodes before ultimately re-entering the blood at the jugular veins.
Fat rich fluid - ends up in thoracic duct

Question 21

What are Peyer’s Patches?

Answer 21

Aggregations of lymphoid nodules present in lamina propria and submucosa of small intestine
Seen in distal jejunum, ileum

Question 22

What are Paneth Cells?

Answer 22

Located near crypt base in some species (primates, horses, rodents)
Considered to have both secretory and phagocytic functions - produce cryptdin and lysins (toxic to bacteria)
Act in paracine manner by opening anion channel in enterocytes causing chloride secretion from crypt erythrocytes
Eosinophilic, round, granules

Question 23

What are enteroendocrine cells?

Answer 23

AKA enterochromaffin, argentaffin
Localized in crypts
Produce seratonin, etc, in response to chemical and mechanical stimuli

Question 24

Describe the large intestine

Answer 24

No villi, absorbs H2O, secretes mucus
Still has intestinal crypts but relatively long
Bands (Taenia coli - smooth muscle, elastic fibers)
Increase in # of goblet cells

Question 25

What are the 3 different glandular regions of the anus?

Answer 25

1. Anal Glands - empty into lumen of anus 2. Anal Sac Glands - empty into anal sacs (outside = skeletal muscle, inside = smooth muscle (Look like liver cells in glands) 3. Circumanal Glands - nonpatent ducts, no function knwon

Question 26

Describe anal sacs.

Answer 26

Paired anal sacs are located lateral and below the anus in carnviores. Anal sacs are lined by keratinized stratiied squamous epithelium. Located between the inner smooth muscle of the internal anal sphincter and the outer skeletal muscle of the external anal sphincter. Glands of anal sac are: Apocrine, Tubular Sweat Glands in dog; Apocrine, Tubular and both Sebaceous and apocrine sweat glands in the Cat

Question 27

Describe circumanal/perianal glands.

Answer 27

Present in subcutis around the anus in dog (also in skin near the prepuce, tail, flank and groin) Composed of: modified sebaceous glands in upper portion and non-sebaceous glands in lower portion Non-sebaceous glands resemble hepatocytes (hepatoid glands)

Question 28

What does saliva contain?

Answer 28

water, salts, enzymes, igA, lysozyme, lactoferrin | Function: digestion, moisture, lubrication, evaporative cooling, local immunity

Question 29

What are salivary glands divided into? Describe.

Answer 29

Major Salivary Glands - parotid, sublingual, submandibular | Minor Salivary Glands (are intramural) - lingual, palate, labial, buccal, zygomatic (carnivores), molar (cats)

Question 30

What type of secretion do salivary glands give off?

Answer 30

``` Serous, Mucous, Mixed Parotid Gland - serous Mandibular Gland - mixed Sublingual Gland - mixed Zygomatic Gland - serous ```

Question 31

What are the secretory units of salivary glands called?

Answer 31

Adenomeres

Question 32

What is each lobe of the liver covered y?

Answer 32

Covered by mesothelium lcoated over a CT layer known as teh Capsule of Glisson

Question 33

What are hepatocytes?

Answer 33

Parenchymal cells arranged in plates with adjacent sinusoids. Plates are organized into hepatic lobules.

Question 34

What are the 2 poles of a hepatocyte:

Answer 34

Bile Pole | Vascular Pole

Question 35

What is the space of disse?

Answer 35

Site of exchange between blood and hepatocyte

Question 36

What is the function of hepatocytes?

Answer 36

Storage of metabolites (energy) | Lipids and carbohydrates are stored in the liver in the form of triglycerides and glycogen

Question 37

What are macrophages called in the liver? Where are they located?

Answer 37

Kupffer cells. | Located adjacent to sinusoids.

Question 38

What are portal triads/portal tracts/portobiliary space?

Answer 38

Branch of hepatic artery, branch of portal vein and bile ductules are seen at edges

Question 39

What is the hepatic acinus? Describe blood flow.

Answer 39

Refers to the vascular flow pattern between lobules of the liver. Flow begins at triad, flows towards central veins via sinusoidal capillaries. Hepatocytes nearest central vein receive blood lowest in O2 (first to be damaged if vascular compromise exists)

Question 40

What are the zones of the hepatic acinus?

Answer 40

``` Zone 1 (perilobular) - high in O2, high in nutrients, high pathogen exposure Zone 2 - moderate Zone 3 (centrilobular) - low ```

Question 41

What is the Gallbladder?

Answer 41

Accepts bile from cystic duct for storage. Abundance mucosae folds when gallbladder is empty. Simple columnar eptihelium, with microvilli, tight junctions, mitochondria, secretory vesicles Epithelial cells are capable of modifying bile No lamina muscularis mucosae Tunica serosa surrounds almost whole organ

Question 42

What kind of secretory units does the exocrine pancrease have?

Answer 42

Tubuloacinar - drain into intercalated ducts lined by cuboidal cells.

Question 43

How does the pancreas differ from a serous salivary parotid gland?

Answer 43

Has no striated ducts Duct system in pancreas is less developed Has endocrine pancreatic islets of Langehans