CH. 26 Digestive System Flashcards
What is the bolus and chyme?
bolus is chewed food mixed with saliva and chyme is the paste like substance that is produced from stomach processes of bolus
What are the two separate categories of organs of the digestive system?
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
What are the six main functions of the digestive system?
ingestion, motility, secretion, digestion, absorption, and elimination of wastes
What is peristalsis?
process of muscular contraction that forms ripples along part of the GI tract and forces material to move further along the tract.
What are the two aspects of digestion?
Mechanical digestion: physically breaks down ingested materials into smaller pieces
Chemical digestion: breaks down ingested material into smaller molecules by using enzymes
What is the epithelial lining of the oral cavity and what is its significance?
Nonkeratinized stratified squamous epithelium: protects against the abrasive activities associated with digestion
How do the uvula and soft palate function together?
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
What are the 3 different salivary glands?
1) Parotid - only serous secretions
2) Submandibular - both mucus and serous secretions
3) Sublingual - both mucus and serous secretions
What are the two types of secretory cells that are housed in the salivary glands?
1) mucous cells: secrete mucin, which forms mucus upon hydration
2) serous cells: secrete a watery fluid containing ions, lysozyme, and salivary amylase
How does swallowed material move throught the pharynx?
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
What is the function of the epiglottis?
as pharyngeal constrictors contract, the epiglottis closes over the laryngeal opening to prevent ingested materials from entering the larynx and trachea
What lines the abdominopelvic cavity?
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
What are mesenteries?
folds of peritoneum that support and stabilize the intraperitonal GI tact organs
What are the 4 tunics of the GI organs?
1) mucosa
2) submucosa
3) muscularis
4) adventitia
What are the three main components of the mucosa?
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
What are the components of submucosa?
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
What occurs when the inner circular layer of the muscularis contract and what happens when the outer longitudional layer of the muscularis contract?
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
What are the two types that the outermost tunic can be composed of?
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
What is the mucosa of the esophagus composed of and how does it help its function?
nonkeratinized stratified squamous epithelium; better to withstand the abrasions of the bolus as it moves through the esophagus
What are the 3 phases of swallowing?
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
What functions does the stomach facilitate?
(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.
What are the four regions of the stomach?
cardia, fundus. body, and pylorus
What lines the stomach?
simple columnar epithelium, although little absorption occurs in the stomach
What is the muscularis of the stomach composed of?
Three smooth muscle layers-
1) inner oblique layer
2) middle circular layer
3) outer longitudional layer
