CH. 26 Digestive System

Question 1

What is the bolus and chyme?

Answer 1

bolus is chewed food mixed with saliva and chyme is the paste like substance that is produced from stomach processes of bolus

Question 2

What are the two separate categories of organs of the digestive system?

Answer 2

1) Gastrointestinal tract: oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, anal canal, and ends at anus
2) Accessory digestive organs: teeth, tongue, salivary glands, liver, gallbladder, and pancreas

Question 3

What are the six main functions of the digestive system?

Answer 3

ingestion, motility, secretion, digestion, absorption, and elimination of wastes

Question 4

What is peristalsis?

Answer 4

process of muscular contraction that forms ripples along part of the GI tract and forces material to move further along the tract.

Question 5

What are the two aspects of digestion?

Answer 5

Mechanical digestion: physically breaks down ingested materials into smaller pieces

Chemical digestion: breaks down ingested material into smaller molecules by using enzymes

Question 6

What is the epithelial lining of the oral cavity and what is its significance?

Answer 6

Nonkeratinized stratified squamous epithelium: protects against the abrasive activities associated with digestion

Question 7

How do the uvula and soft palate function together?

Answer 7

when you swallow, the soft palate and the uvula elevate to close off the posterior entrance into the nasopharynx and prevent ingested materials from entering the nasal region

Question 8

What are the 3 different salivary glands?

Answer 8

1) Parotid - only serous secretions
2) Submandibular - both mucus and serous secretions
3) Sublingual - both mucus and serous secretions

Question 9

What are the two types of secretory cells that are housed in the salivary glands?

Answer 9

1) mucous cells: secrete mucin, which forms mucus upon hydration
2) serous cells: secrete a watery fluid containing ions, lysozyme, and salivary amylase

Question 10

How does swallowed material move throught the pharynx?

Answer 10

three skeletal muscle pairs, called phayngeal constricters, form the wall of the pharynx. sequential contraction of the constrictors decrease the diameter of the pharynx, pushing swalled material toward the esophagus

Question 11

What is the function of the epiglottis?

Answer 11

as pharyngeal constrictors contract, the epiglottis closes over the laryngeal opening to prevent ingested materials from entering the larynx and trachea

Question 12

What lines the abdominopelvic cavity?

Answer 12

parietal peritoneum: lines the inside surface of the body wall

visceral peritoneum: folds back to cover the surface of internal organs

peritoneal cavity: potential space where the peritoneal layers that face each other secrete a lubricating serous fluid in order to allow abdominal organs to move freely without friction

Question 13

What are mesenteries?

Answer 13

folds of peritoneum that support and stabilize the intraperitonal GI tact organs

Question 14

What are the 4 tunics of the GI organs?

Answer 14

1) mucosa
2) submucosa
3) muscularis
4) adventitia

Question 15

What are the three main components of the mucosa?

Answer 15

1) an inner (superficial) epithelium lining the lumen of the GI tract
2) an underlying areolar connective tissue called the lamina propria
3) a relatively thin layer of smooth muscle termed the muscularis mucosae

Question 16

What are the components of submucosa?

Answer 16

accumulations of lymphatic tissue in some submucosal regions; mucin secreting glands that project ducts across the mucosa and open into the lumen of the tract in the esophagus and duodenum; many large blood vessels and lymph vessels; and nerves that extend fine brnaches into both the mucosa and muscularis

Question 17

What occurs when the inner circular layer of the muscularis contract and what happens when the outer longitudional layer of the muscularis contract?

Answer 17

Contractions of the circular layer constrict the diameter of the tube lumen and contractions of the longitudional layer shorten the tube

inner circular muscle layer is greatly thickened at places to form a sphincter

• closes off the lumen opening at some point along the GI tract to control the movement of materials

Question 18

What are the two types that the outermost tunic can be composed of?

Answer 18

1) adventitia: composed of areolar connective tissue with dispersed collagen and elastic fibers
2) serosa: the same components as the adventitia, but is covered by a visceral peritoneum

Question 19

What is the mucosa of the esophagus composed of and how does it help its function?

Answer 19

nonkeratinized stratified squamous epithelium; better to withstand the abrasions of the bolus as it moves through the esophagus

Question 20

What are the 3 phases of swallowing?

Answer 20

1) voluntary phase: Food and saliva
mix in the oral cavity. Chewing forms a bolus that is mixed and manipulated
by the tongue and then pushed superiorly against the hard
palate. Transverse palatine folds in the hard palate help direct the
bolus posteriorly toward the oropharynx

2) pharyngeal phase: During this
phase, (1) the soft palate and uvula elevate to block the passageway
between the nasopharynx and oropharynx; (2) the bolus enters the
oropharynx; and (3) the larynx and laryngeal opening elevate toward
the epiglottis, ultimately covering and sealing the glottis to prevent
swallowed materials from entering the trachea

3) esophageal phase:This phase begins when the superior esophageal
sphincter relaxes to allow ingested materials into the esophagus. The
presence of the bolus within the lumen of the esophagus stimulates
peristaltic waves of muscular contraction that assist in propelling the
bolus toward the stomach. The inferior sphincter contracts after the bolus
passes into the stomach to prevent reflux of materials and fluids back
into the esophagus

Question 21

What functions does the stomach facilitate?

Answer 21

(1) mechanical digestion by contractions of its
thick muscularis layer that churns and mixes the bolus with gastric
secretions, and (2) chemical digestion through its gastric secretions
of acid and enzymes.

Question 22

What are the four regions of the stomach?

Answer 22

cardia, fundus. body, and pylorus

Question 23

What lines the stomach?

Answer 23

simple columnar epithelium, although little absorption occurs in the stomach

Question 24

What is the muscularis of the stomach composed of?

Answer 24

Three smooth muscle layers-

1) inner oblique layer
2) middle circular layer
3) outer longitudional layer

Question 25

What are the three specific segments of the small intestine?

Answer 25

1) duodenum: forms the initial first segment of the small intestine; originates at pyloric sphincter
2) jejunum: middle region; primary region within small intestine for chemical digestion and nutrient absorption
3) ileum: last region of small intestine; distal end terminates at the ileocecal valve

Question 26

How does the presence of villi on the surface of the circular folds of the small intestine help?

Answer 26

increase the surface area for absorption and secretion; microvilli on free surface of simple columnar cells increase the absorptive surface area even further

Question 27

What is mostly absorbed by the large intestine?

Answer 27

most of the water and ions from the remaining digested material; watery material that first enters large intestine soon solidifies and becomes feces

• also absorbs a very small percentage of nutrients

Question 28

What are the four segments the colon is partioned into?

Answer 28

1) ascending colon
2) transverse colon
3) descending colon
4) sigmoid colon

Question 29

What is the mucosa of the large intestine lined with?

Answer 29

simple columnar epithelium and goblet cells: simple columnar ET absorb nutrients that were not absorbed during passage through small intestine and goblet cells secrete mucin to lubricate the undigested material as it pases through