A&P II Chapter 25 Digestive System

nutrients

smaller components

most __________ we eat cannot be used in existing form and must be broken down into ________ _______________ before the body can make use of them

digestive system

essentially a disassembly line

to break down nutrients into a form that can be used by the body

to absorb them so they can be distributed to the tissues

what are the functions of the digestive system

gastroenterology

the study of the digestive tract and the diagnosis and treatment of its disorders

ingestion

secretion

propulsion

digestion

absorption

defecation

what are the 6 stages of digestion?

ingestion

selective intake of food

secretion

endocrine/exocrine glands secrete substances (enzymes, acids, hormones) that aid other digestive processes

propulsion

ingested food is moved from one organ to the next via peristalsis

digestion

mechanical and chemical breakdown of food into a form usable by the body

absorption

uptake of nutrient molecules into the epithelial cells of the digestive tract and then into the blood and lymph

defecation

elimination of feces

mechanical digestion

the physical breakdown of food into smaller particles

cutting and grinding action of teeth

churning action of stomach and small intestine

what are some examples of mechanical digestions in the body?

mechanical digestion

exposes more food surface to the action of digestive enzymes

chemical digestion

a series of hydrolysis reactions that breaks dietary macromolecules into their monomers (residues)

chemical digestion

carried out by digestive enzymes produced by salivary glands, stomach, pancreas, and small intestine

polysaccharides into monosaccharides

proteins into amino acids

fats into monoglycerides and fatty acids

nucleic acids into nucleotides

what are the results of chemical digestion?

digestive tract

gastrointestinal tract

what are the two anatomical subdivisions of the digestive system?

digestive tract

alimentary canal

30 ft long muscular tube extending from mouth to anus

mouth, pharynx, esophagus, stomach, small intestine, and large intestine

what does the digestive tract consist of?

gastrointestinal (GI) tract

makes up the stomach and intestine

teeth, tongue, salivary glands, liver, gallbladder, and pancreas

what are the accessory organs?

epithelium

lamina propria

muscularis mucosae

what are the characteristics of the mucosa (inner most layer)?

submucosa

the layer that surrounds the mucosa

muscularis externa

the layer that surrounds the submucosa

inner circular layer

outer longitudinal layer

what are the two layers of muscularis externa?

areolar tissue

mesothelium

what are the characteristics of the serosa (outer most layer)?

enteric nervous system

a nervous network in the esophagus, stomach, and intestines that regulate digestive tract motility, secretion, and blood flow

enteric nervous system

contains sensory neurons that monitor tension in gut wall and conditions in lumen

submucosal (Meissner) plexus

myenteric (Auerbach) plexus

what are the two networks of neurons that the enteric nervous system is composed of?

submucosal (Meissner) plexus

(in submucosa) controls glandular secretion of mucosa

submucosal (Meissner) plexus

(in submucosa) controls movements of muscularis mucosae

myenteric (Auerbach) plexus

parasympathetic ganglia and nerve fibers between the two layers of the muscularis interna

myenteric (Auerbach) plexus

controls peristalsis and other contractions of muscularis externa

mesenteries

connective tissue sheets that loosely suspend the stomach and intestines from the abdominal wall

motility; secretion

__________ and __________ of the digestive tract are controlled by neural, hormonal, and paracrine mechanisms

short (myenteric) reflexes

long (vagovagal) reflexes

what are the two reflexes of neural control?

short (myenteric) reflexes

stretch or chemical stimulation acts through myenteric plexus

short (myenteric) reflexes

stimulates peristaltic contractions of swallowing

long (vagovagal) reflexes

parasympathetic stimulation of digestive motility and secretion

hormones

chemical messengers secreted into bloodstream and stimulate distant parts of the digestive tract

gastrin and secretion

paracrine secretions

chemical messengers that diffuse through the tissue fluids to stimulate nearby target cells

oral cavity

serves as the start point of the digestive system

ingestion, secretion, chemical and mechanical digestion, and propulsion

what all occurs in the oral cavity?

teeth and tongue and salivary glands

what two accessory organs are located in the oral cavity?

mastication (chewing)

breaks food into smaller pieces to be swallowed and exposes more surface to the action of digestive enzymes

mastication

first step in mechanical digestion

involuntary chewing reflex

during mastication, food stimulates oral receptors that trigger an ___________ __________ _________

teeth

key organs of mechanical digestion

teeth

located in bony sockets found in the maxilla and mandible and held in place by the periodontal ligament

incisors

canines (cuspids)

molars

what are the three types of teeth?

incisors

central teeth that are broad and flat with a narrow crown. specialized for cutting off pieces of food

canines (cuspids)

located on either side of the incisors. have pointed crowns that are specialized for ripping and tearing

molars

posterior and lateral to the canines. contain broad crowns and are specialized for grinding

1. moisten mouth

2. begin starch and fat digestion

3. cleanse teeth

4. inhibit bacterial growth

5. dissolve molecules so they can stimulate the taste buds

6. moisten food and bind it together into bolus to aid in swallowing

what are the functions of saliva?

salivary amylase

lingual lipase

mucus

lysozyme

immunoglobulin A (IgA)

electrolyes

in saliva and salivary glands, what are the solutes with a hypotonic solution of 97% to 99.5% water?

salivary amylase

enzyme that begins starch digestion in the mouth

lingual lipase

enzyme that is activated by stomach acid and digests fat after the food is swallowed

mucus

binds and lubricates the mass of food and aids in swallowing

lysozyme

enzyme that kills bacteria

immunoglobulin A (IgA)

an antibody that inhibits bacterial growth

electrolytes

Na+, K+, Cl-, phosphate, and bicarbonate

6.8 to 7.0

what is the pH for saliva and salivary glands

intrinsic salivary glands

small glands dispersed amid other oral tissues

lingual glands

labial glands

buccal glands

what are the three intrinsic salivary glands?

lingual glands

glands in the tongue; produce lingual lipase

labial glands

glands inside of the lips

buccal glands

glands inside of the cheek

extrinsic salivary glands

three pairs connected to oral cavity by ducts

parotid

submandibular gland

sublingual glands

what are the three extrinsic salivary glands?

parotid

gland located beneath the skin anterior to the earlobe;

mumps is an inflammation and swelling of this gland caused by a virus

submandibular gland

gland located halfway along the body of the mandible; its duct empties at the side of the lingual frenulum, near the lower central incisors

sublingual glands

glands located in the floor of the mouth; has multiple ducts that empty posterior to the papilla of the submandibular duct

1 to 1.5

extrinsic salivary glands secrete about _____ to _____ L of saliva per day

cells of acini

filter water and electrolytes from blood and add amylase, mucin, and lysozyme

salivary nuclei

in the medulla oblongata and pons respond to signals generated by presence of food

salivary nuclei

send signals by way of autonomic fibers in the facial and glossopharyngeal nerves to the glands

parasympathetics

stimulate the glands to produce an abundance of thin, enzyme-rich saliva

sympathetic stimulation

stimulates the glands to produce less, and thicker, saliva with more mucus

(dry or sticky under stress or dehydration)

bolus

mass swallowed as a result of saliva binding food particles into a soft, slippery, easily swallowed mass

pharyngeal constrictors

(superior, middle, and inferior) circular muscles that force food downward during swallowing

esophagus

a straight muscular tube 25 to 30 cm long

pharynx; cardiac orifice; esophageal hiatus

the esophagus extends from ________ to ___________ ___________ of stomach passing through ___________ ________ in diaphragm

lower esophageal sphincter

food pauses at this sphincter

heartburn

burning sensation in the lower esophageal sphincter produced by acid reflex into the esophagus

swallowing (deglutition)

a complex action involving over 22 muscles in the mouth, pharynx, and esophagus

swallowing center

pair of nuclei in medulla oblongata that coordinates swallowing

swallowing center

communicates with muscles of the pharynx and esophagus by way of trigeminal, facial, glossopharyngeal and hypoglossal nerves

voluntary phase

pharyngeal phase

esophageal phase

what three phases occur in swallowing?

peristalsis

wave of muscular contraction that pushes the bolus ahead of it

(entirely involuntary reflex)

1 to 2

4 to 8

liquid reaches the stomach in ______ to ______ seconds;

food bolus in ______ to ______ seconds

stomach

muscular sac in upper left abdominal cavity immediately inferior to the diaphragm

store food

what is the stomach's primary function?

stomach

mechanically breaks up food particles, liquefies the food, and begins chemical digestion of protein and fat

chyme

soupy or pasty mixture of semi digested food in the stomach

gastric pits

depressions in gastric mucosa lined with simple columnar epithelium

cardiac; pyloric; gastric

two or three tubular glands open into the bottom of each gastric pit: the ___________ glands in cardiac region, the ___________ glands in the pyloric region, and the ___________ glands in the rest of the stomach

mucus cells

secrete mucus; predominate in cardiac and pyloric glands

mucous neck cells

in gastric glands, called ________ _______ _______, since they are concentrated at the neck of the gland

regenerative (stem) cells

found in the base of the pit and in the neck of the gland