Ch 24 - Digestive System

local factors of motility control include ______, ___, & ____

-local env factors (pH, volume, chemical composition) -overstretching causing the release of chemicals like prostaglandins and histamines (which may affect adjacent cells within a small segment of the tract) -stretching of the intestinal wall can stimulate localized contractions of smooth muscles

the 6 main functions & processes of the digestive system?

1) ingestion -active process involving decision making 2) mechanical digestion and propulsion 3) chemical digestion 4) secretion -release of water, acids, enzymes, buggers, and salts by digestive tract, glands, and gallbladder 5) absorption -nutrients move across the digestive epithelium and move either to the interstitial fluid or in the blood for transport 6) defecation

What are the 3 major ways the digestive tract is regulated?

1) local factors 2) neural mechanisms 3) hormonal mechanisms

What 4 histological layers lie throughout the whole digestive tract?

1) mucosa (deepest) 2) submucosa 3) muscular layer (formerly called muscularis externa) 4) serosa (most superficial)

3 additional functions of digestive lining?

1) protects against corrosive effects of digestive acids and enzymes 2) protects against mechanical stresses like abrasian 3) protects against bacteria that are swallowed w/ food

the 2 layers of the smooth muscle cells in the muscularis mucosae?

1) the circular layer/muscle — inner layer that encircles the lumen 2) the longitudinal layer — an outer layer contains muscle cells arranged parallel to the long axis of the tract

_________ in the greater omentum conforms to the shapes of the surrounding organs, providing padding and protection across the anterior and lateral surfaces of the _____

Adipose tissue; abdomen.

_______, or swallowing, is divided into __________, ______, & ________ phases

Deglutition; buccal, pharyngeal, and esophageal

chewed food is called ____

a bolus

segmentation does not follow______ and therefore does not push materials along the tract_____

a set pattern; in any one direction

________ contributes to the characteristic "beer belly."

adipose tissue in the greater omentum (AKA visceral fat)

a(n) ________ is a dense fibrous sheath in areas where there is no serosa covering the muscular layer. It firmly attaches the ______ to adjacent structures

adventitia; digestive tract

digestive system is also called the _____ system and the GI tract is also called the ____

alimentary; alimentary canal

The lamina propria is a layer of _______ in the _______ that also contains__________

areolar tissue; mucosa; sensory nerve endings, lymphatic vessels, smooth muscle cells, and scattered lymphatic tissue blood vessels; **smooth muscle here is more so just for SHAPE than for actual movement through the tract

The buildup of fluid in the peritoneal cavity creates abdominal swelling called

ascites

The submucosa has lots of______ and in some regions it also contains ____ that secrete _____ into the lumen of the digestive tract.

blood vessels and lymphatic vessels; exocrine glands; buffers and enzymes

the perietal peritoneum lines the inner surface of _____

body wall

the myenteric plexus lies sandwiched between the_______

circular and longitudinal muscle layers

small intestine has ____ to increase surface area

circular folds (plicae circulares)

the muscular layer of the esophagus has the usual inner ______ layer and an outer ____ layer

circular; longitudinal

like the smooth muscle cells in the muscularis mucosae, those in the muscular layer are arranged in an inner ________ layer and an outer _______ layer.

circular; longitudinal **these layers are really what are moving food along the GI tract

at rest, superior and inferior ends of the esophagus are _____

closed **we use the terms "sphincters" but neither region has a well-defined sphincter muscle, so not true sphincters but similar

The esophagus begins posterior to the _____ cartilage, at the level of vertebra _____

cricoid; C6

The movements of the digestive tract are coordinated primarily by the sensory neurons, interneurons, and motor neurons of the________

enteric nervous system (ENS)

Also scattered among the columnar cells of the columnar epithelium are __________ cells which secrete hormones that coordinate the activities of______

enteroendocrine; the digestive tract and the accessory glands.

In general, parasympathetic stimulation ____ muscle tone/activity of the GI tract and sympathetic stimulation_____ it

increases; decreases

Along its outer margin, the submucosa contains a network of __________, called the_________

intrinsic nerve fibers and scattered neurons; submucosal neural plexus.

the mucosa and submucosa layers of the esophagus contain ______

large folds **allow for expansion during the passage of a large bolus **Muscle tone in the walls keeps the lumen closed, except when you swallow.

the _______ is a mesentery on the ventral surface of the stomach, between the stomach and the liver

lesser omentum

the _________ is a thick mesenterial sheet

mesentery proper

The mucosa of the esophagus contains a _______ , ________ epithelium similar to that of _______

nonkeratinized; stratified squamous; the pharynx and oral cavity

triggers for PSNS regulation of salivary secretion are _____

objects in mouth, chewing with an empty mouth, smelling food, thinking of food, irritants, nausea **Increased saliva production in response to unpleasant stimuli helps reduce the stimulus by dilution, rinsing, or buffering strong acids or bases

what are the major organs of the digestive system?

oral cavity (mouth), pharynx, esophagus, stomach, small intestine, large intestine

the visceral peritoneum lines the _____

organs

the greater omentum lays _____

over GI tract

This visceral smooth muscle includes cells called ______ cells that are located in the _________, which surround the lumen of the digestive tract.

pacesetter; muscularis mucosae and muscular layer;

When you are ready to swallow, the ______ muscles elevate the soft palate and adjacent portions of the ______.

palatal; pharyngeal wall

The ENS is primarily innervated by the_________ division of the ANS

parasympathetic

Each salivary gland has ______ innervation

parasympathetic and sympathetic **role of SNS unclear

The lesser omentum stabilizes the position of the ______ and provides an access route for blood vessels and other structures entering or leaving the ________

stomach; liver

the lesser omentum holds _______ in place to the ____

stomach; liver

____ sits on top of visceral fat and applies more so to women

subQ fat

The parasympathetic efferents originate in the ________ of the medulla oblongata and synapses in the __________

superior salivatory and inferior salivatory nuclei; submandibular and otic ganglia

lubrication increases the amt of ____ and helps move ____

taste; food toward esophagus

What are the accessory organs of the digestive system?

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

local factors regulate ______

the initial regulation of digestive function

Muscles of the neck and pharynx, _________, then elevate the larynx, which causes _______

the palatopharyngeus and stylopharyngeus; the epiglottis to bend over the glottis **the bolus can glide across the epiglottis rather than falling into the larynx

In the oral cavity, pharynx, esophagus, stomach, and the proximal portion of the small intestine, the lamina propria also contains______

the secretory cells of intestinal glands.

Digestive hormones can enhance or diminish _______ to_________

the sensitivity of the smooth muscle cells; neural commands **produced by enteroendocrine cells of GI tract

The pharynx, or _____, is an anatomical space that serves as a common passageway for _____

throat; solid food, liquid, and air.

salivary triggers stimulate receptors monitored by the _____ nerve or taste buds innervated by cranial nerves _____ or _____

trigeminal (V); VII, IX; X.

_______ sphincter prevents air entry and the _______sphincter prevents _____

upper esophageal; lower esophageal (cardiac sphincter); heartburn

food is forced from the oral cavity to the ______ and backwards from the action of the _______ and with help from _____

vestibule; muscles of mastication; cheeks, lips, and tongue **muscles of mastication are: masseter, temporalis, lateral pterygoid, medial pterygoid

The muscular layers of the digestive tract consist of _______ tissue

visceral smooth muscle

The ______ motor neurons that control smooth muscle contraction and glandular secretion are located in the______

visceral; myenteric plexus ***These neurons are usually considered parasympathetic, bc some of them synapse with parasympathetic preganglionic fibers

for every 1 human cell, we have ____ bacterial cells

10

All but the first _______ of the small intestine is suspended by the mesentery proper

25 cm (10 in.)

what are the 5 main retroperitoneal structures?

Pancreas Duodenum Urinary bladder Rectum Uterus

the muscular layer is dominated by ________ cells

Smooth muscle

in addition to producing salivary amylase (which helps digest _____), saliva also contains a small amount of _______ secreted by the glands of the tongue

carbs; lingual lipase

the mucosa is the _____ histological layer and consists of ______ covered with mucous

deepest; epithelium

the submucosa is a layer of__________ that binds the mucosa to the muscular layer

dense irregular connective tissue

Neural mechanisms control______ & involve both _____ and ____

digestive tract movement; short reflexes; long reflexes

The _______ mesentery of the stomach becomes greatly enlarged and forms an enormous pouch, the ________, that extends inferiorly between the body wall and the anterior surface of the small intestine

dorsal; greater omentum

the muscular layer of the esophagus is unique in that _____

each 1/3 along its length is different

the submucosa layer of the esophagus contains ______ that make mucous

esophageal glands **They produce mucus that reduces friction between the bolus and the esophageal lining.

after the thoracic cavity, a bolus enters the abdominopelvic cavity through the _______

esophageal hiatus **bolus enters stomach at T7

The esophagus is innervated by parasympathetic and sympathetic fibers from the _________

esophageal plexus

peristalsis occurs in ________ and produces ____

esophagus, small intestine, large intestine (AKA along the digestive tract); bolus

the _______ is a remnant of the ventral mesentery between the liver and the anterior abdominal wall

falciform ligament

the ______ ligament holds the liver to the _____ and _____

falciform; diaphragm; abdominal wall

The falciform ligament helps stabilize the position of the ______ relative to the _______

liver; diaphragm and abdominal wall.

stomach has _____ that fill out when the stomach is full

longitudinal folds

saliva contains antibodies (IgA) and _______, which both help control populations of oral bacteria

lysozymes

segmentation is an activity in_______ where they undergo cycles of contraction that ______, mixing the contents with intestinal secretions

most areas of the small intestine and some portions of the large intestine; churn and fragment the bolus

The wall of the esophagus contains _________ histological layers

mucosa, submucosa, and muscular **adventitia is connective tissue outside the muscular layer

The esophageal muscularis mucosae (in the _____) consists of an ______ layer of _______

mucosa; irregular; smooth muscle.

the epithelium in the stomach contains _______ cells, and in the intestines the epithelium contains _____ cells

mucous; goblet

the _________ layer is the 2nd most superficial histological layer of the GI tract and the submucosal plexus lies along the ______ border of it

muscular; inner ***submucosal plexus provides the innervation for movements

the ________ is a network of parasympathetic ganglia, sensory neurons, interneurons, and sympathetic postganglionic fibers.

myenteric plexus

mesenteries are double sheets of _______ membrane

peritoneal

the serosa covers the muscular layer along most portions of the digestive tract enclosed by the ______

peritoneal cavity

The serous membrane lining the peritoneal cavity continuously produces ________, which lubricates the surfaces.

peritoneal fluid

The abdominopelvic cavity contains the ______ cavity, which is lined by a serous membrane called the ____

peritoneal; peritoneum.

Omentum refers to areas of 4 layers of _______

peritoneum

while the glottis is closed, the _______ muscles push the bolus toward and into the esophagus

pharyngeal constrictor

retroperitoneal organs lie ______ rather than______, the peritoneal cavity

posterior to, surrounded by

The esophagus descends toward the thoracic cavity _____ to the trachea, continuing inferiorly along the ______ wall of the mediastinum.

posterior; posterior

_______ is different from peristalsis in that the muscular contraction seeks to keep materials IN the tube (rather than down it) in order to absorb/churn more

segmentation

the submucosal neural plexus contains _________ that innervate the_________

sensory neurons, PSNS neurons, and SNS postganglionic fibers; mucosa and submucosa

the myenteric plexus also contains ___________responsible for _______ reflexes that operate entirely outside the control of the central nervous system

sensory neurons, motor neurons, and interneurons; short **remember, myenteric plexus is network of parasympathetic ganglia, sensory neurons, interneurons, and sympathetic postganglionic fibers between the circular and longitudinal muscle layers.

the ____ is the most superficial layer and can be thought of as "_____"

serosa; protective **the serosa is a serous membrane

In most areas of the digestive tract, deep to the lamina propria is a narrow _______, called the ______

sheet of smooth muscle and elastic fibers; muscularis mucosae

the mucosa is made up of _____ epithelium in the stomach

simple columnar

the mucosa is made up of _____ epithelium in the oral cavity, pharynx, esophagus, and anal canal

simple/stratified squamous *book says stratified only*

muscular esophageal layers: superior 1/3: ________ middle 1/3: _______ inferior 1/3: ______

skeletal muscle fibers; a mixture of skeletal and smooth muscle tissue smooth muscle

short reflexes control localized activities that involve _______ of the digestive tract

small segments **For example, they may coordinate local peristalsis and trigger secretion by digestive glands in response to the arrival of a bolus.

GI tract made almost entirely of _____ muscle

smooth

Pacesetter cells undergo________, triggering a wave of contraction that spreads throughout the entire muscular sheet

spontaneous depolarization

Mesenteries function to ________ and also prevent ______

stabilize the positions of the attached organs; the intestines from becoming entangled during digestive movements or sudden changes in body position.