Digestive System Part 1

Question 1

what are the main functions of the digestive system?

Answer 1

• swallow and digest food
• absorb water and nutrients
• expel solid waste
• secretion (mucosa)
• barrier (mucosa)
• immunological protection (mucosa)

Question 2

what is the main function of the oral cavity in the GI Tract?

Answer 2

• receives food
• chews food
• moistens food
• enzymes been the digestion process in the mouth

Question 3

what are the three regions of the oral mucosa and their epithelium type?

Answer 3

• lining: non-keratinized stratified squamous epithelium
• masticatory: keratinized stratified squamous epithelium (resist abrasion)
• specialized: non-keratinized stratified squamous epithelium (taste buds)

Question 4

what are the components of the oral cavity?

Answer 4

• epithelium
• lamina propria (minor salivary glands of the lips tongue and cheeks)
• muscle (voluntary manipulation; speech, digestion, swallowing)
• secretory products
• lymphatic tissues: (diffuse, nodules, tonsils)

Question 5

what are the regions the lips are divided into?

Answer 5

• external skin region: keratinized stratified squamous epithelium
• vermilon zone: slightly keratinized stratified squamous epithelium
• internal mucosal region: non-keratinized stratified squamous epithelium

Question 6

what are the characteristics of the vermilion zone?

Answer 6

• no sweat or sebaceous glands
• requires periodic moistening
• underlying connective tissue rich in sensory innervation and capillaries (pink tint)

Question 7

what is the palate?

Answer 7

roof of the oral cavity that is bound by the
- hard palate
- soft palate (talking breathing, swallowing) ***also has oral and nasal surfaces

Question 8

what is the function of the epiglottis?

Answer 8

when swallowing food it shuts of the pathway to the airways to ensure food travels down towards the esophagus

Question 9

what is the structure of the hard palate?

Answer 9

keratinized stratified squamous epithelium supported by a lamina propria which are both supported by underlying spicular bone

Question 10

what is the soft palate?

Answer 10

soft structure supported by skeletal muscle that houses numerous secretory mucous glands

Question 11

what is the structure of the nasal surface of the soft palate?

Answer 11

lined by pseudo-stratified ciliated columnar epithelium with numerous mixed glands

Question 12

what is the structure of the oral surface of the soft palate?

Answer 12

lined by a nonkeratinized stratified squamous epithelium of the wet kind which interdigitated with the underlying lamina propria

Question 13

what is the pharynx?

Answer 13

• nasopharynx, oropharynx, hypopharynx
• passage way of food to the esophagus

Question 14

what are the layers/general structure of the digestive tube (esophagus to colon)?

Answer 14

• mucosa: epithelium, lamina propria, mucularis mucosae
• submucosa: glands, vessels with nerve plexus
• mucularis externa: inner circular layer, outer longitudinal layer, nerve plexus in between
• adventitia (loose CT, esophagus) or serosa (stomach to colon)

Question 15

what are the differences in structure of the mucosal areas in the digestive tube?

Answer 15

• esophagus: mucous folds
• stomach: pits
• duodenum: villi
• jejunum: villi
• ileum: villi
• colon: gland openings

Question 16

what is the esophagus?

Answer 16

strong muscular tube that conveys food from the oropharynx to the stomach

Question 17

what does the initiation of swallowing involve?

Answer 17

voluntary act involving the skeletal musculature of the oropharynx followed by a strong peristaltic reflex in the upper part of the esophagus

Question 18

what is the structure of the esophagus and the components?

Answer 18

• mucosa: thick protective non-keratinized stratified squamous epithelium, a thin layer of connective tissue (lamina propria), muscularis mucosa
• submucosa: very loose, elastic fibers and seromucous glands
• muscularis externa: outer and inner layer

Question 19

what is found in the submucosa and between the layers of the muscularis?

Answer 19

peripheral ganglia

Question 20

what is Barrett Esophagus?

Answer 20

intestinal metaplasia of the distal esophagus causing patches of red, velvety mucosa extending upward from the gastroesophageal junction

Question 21

what does Barrett’s Esophagus have an increased risk of?

Answer 21

esophageal adenocarcinoma

Question 22

what are the regions of the stomach?

Answer 22

• cardiac region: superior opening or inlet of the stomach
• fundus and body: major part of the stomach between the fundus and pyloric antrum with lesser and greater curvature areas
• pyloric part: funnel shaped outflow region of the stomach

Question 23

what are rugae of the stomach?

Answer 23

epithelial folds of the stomach

Question 24

What are the main functions of the stomach in digestion?

Answer 24

• mechanically churns food into pulp-like fluid called chyme
• digests proteins using pepsin, adds acid to food, and produces gastric lipase for fat digestion
• some absorption also occurs (water, ions, alcohol, aspirin, caffeine)

Question 25

What substances are produced by the stomach and what are their roles?

Answer 25

- mucus (protects lining) - lysozyme (antibacterial) - gastrin (stimulates acid production) - somatostatin (regulates digestion)

Question 26

is the stomach an exocrine or endocrine organ?

Answer 26

both

Question 27

what is the gastric mucosa?

Answer 27

the innermost layer of the stomach, containing specialized cells organized into structures called gastric pits and gastric glands

Question 28

what are the regions of a gastric gland?

Answer 28

- Gastric Pit (Foveolus): lined with surface mucous cells that secrete mucus to protect the stomach lining from acidic conditions - Isthmus: a transition area of parietal cells - Neck: contains neck mucous cells, stem cells, and parietal cells - Base of the Gland: houses chief/peptic cells, oxyntic (parietal) cells, neck mucous cells, and neuroendocrine cells

Question 29

what are the differences in gastric pits and glands for the different regions of the stomach?

Answer 29

- Cardiac Stomach: length of pits is equal to the length of glands (highly coiled galnds) - Fundic Stomach: shorter pits and longer glands - Pyloric Stomach: deep pits and short coiled glands

Question 30

What type of epithelium lines the gastric pits and ridges of the stomach and how often do they renew?

Answer 30

- simple tall columnar epithelium - every three days

Question 31

Where does the regeneration of gastric epithelial cells primarily occur?

Answer 31

In the deeper regions of the pits and necks of the glands

Question 32

what are enteroendocrine cells?

Answer 32

- peptide-producing and secreting cells (gastrin) - that coordinate GI function, send and receive signals - found at the bases of the glands and between other epithelial cells

Question 33

What is the major location and function of Gastrin?

Answer 33

- located in the Pylorus - stimulates gastric acid secretion, pepsinogen release, and increases motility

Question 34

what is the major location and functions of Secretin?

Answer 34

- produced in the Small Intestine - stimulates pancreatic enzyme secretion and bicarbonate ion secretion - inhibits gastric acid secretion and stomach emptying

Question 35

what is the major location and functions of Cholecystokinin (CCK)?

Answer 35

- found in the Small Intestine - stimulates pancreatic enzyme secretion and gallbladder contraction - inhibits gastric acid secretion and stomach emptying

Question 36

what is the major location and functions of Gastric Inhibitory Peptide?

Answer 36

- located in the Duodenum and Jejunum - primarily stimulates insulin release - inhibits gastric acid secretion

Question 37

what is the major location and functions of Serotonin?

Answer 37

- found in the Stomach and Intestines - increases gut motility.

Question 38

what is the major location and functions of Histamine?

Answer 38

- located in the mucosa throughout the GI tract - stimulates gastric acid secretion

Question 39

what is the major location and functions of Somatostatin?

Answer 39

- located in the Pylorus, Duodenum, and Pancreatic Islets - inhibits gastrin release, gastric acid secretion, and the release of other GI hormones

Question 40

what are chief cells and what do they contain?

Answer 40

- simple cuboidal cells lining lower part of the gastric gland - filled with coarse granules which contain pepsinogen and lipase

Question 41

what are parietal cells and what do they contain?

Answer 41

- cell that has abundant mitochondria and secretory canaliculi - contains receptors for histamine, gastrin and acetylcholine

Question 42

How is hydrochloric acid produced in Parietal Cells?

Answer 42

- CO₂and H₂O→ H₂CO₃ (carbonic acid) via enzyme carbonic anhydrase - H₂CO₃ splits into H⁺ (hydrogen ion) and HCO₃⁻ (bicarbonate ion) - HCO₃⁻ is transported out of the cell into the bloodstream - Cl is brought into the cell in exchange - H⁺ ions are pumped into the stomach lumen, K⁺ ions are exchanged back into the parietal cell (ATPase) - Cl⁻ ions follow into the lumen through chloride channels and H⁺ + Cl⁻ → HCl in the stomach

Question 43

what do the different epithelial cells of the stomach secrete?

Answer 43

- surface mucosal cell: secrete mucus - mucous neck cell: secrete mucus - parietal cell: secrete hydrochloric acid and intrinsic factor - chief cell: secretes pepsinogen and gastric lipase

Question 44

What is the role of acetylcholine in the stomach?

Answer 44

parasympathetic (vagus nerve) mediator stimulates parietal cells to secrete HCl

Question 45

what is the role of the fenestrated capillaries around the gastric glands?

Answer 45

facilitate bicarbonate delivery to protect the surface epithelial cells

Question 46

What is Peptic Ulcer Disease?

Answer 46

disease caused by H. pylori infection or NSAID use that imbalances mucosal defenses and damaging forces