Digestive System Flashcards
six functions of the digestive system
- ingestion
- secretion
- propulsion
- digestion
- absorption
- defecation
organs of the alimentary canal
- oral cavity (mouth)
- pharynx
- stomach
- small intestine
- large intestine
accessory organs and structures involved in the digestive process
- teeth
- tongue
- salivary glands
- liver
- gallbladder
- pancreas
peritoneal membrane (or peritoneum, the serous membrane of the abdominopelvic cavity)
consists of two layers
- parietal peritoneum (outer)
- visceral peritoneum (inner)
- peritoneal cavity (between the layers)
intraperitoneal vs. retroperitoneal regions
intraperitoneal are located entirely within the peritoneal cavity
retroperitoneal are located partly or completely outside the cavity
2 prominent mesenteries of the abdominopelvic cavity
greater omentum and lesser omentum
4 layers that make up the wall of the GI tract
mucosa, submucosa, muscularis externa, and either the serosa or adventitia.
role of the mucosa layer
coats the epithelium, protecting it and the underlying tissues from ingested food and chemicals secreted by digestive organs. Houses regenerative epithelial cells that have a high rate of mitosis, allowing the mucosa to replace epithelial cells as they are damaged or sloughed off in the alimentary canal
nerve plexus in the submucosa layer
submucosal plexus
nerve plexus in the muscularis layer
myenteric plexus
sphincter
special, circular muscles that open and close certain body parts. Most often, the action of a sphincter is to regulate the passage of some type of fluid, such as bile, urine or fecal matter
relationship of smooth muscle contraction and the types of motility
in oral cavity, the pharynx, the superior portion of the esophagus, and the last portion of the large intestine, motility is due to skeletal muscle. In the rest of the alimentary canal, motility is the work of smooth muscle. Motility takes several forms (swallowing, churning, peristalsis, and defecation)
interaction of the sympathetic, parasympathetic and enteric nervous systems and their effects on mobility and secretions
Nervous system regulation of motility is accomplished by the nerves of the ANS. The sympathetic and parasympathetic branches of the ANS generally have opposite effects on gastrointestinal motility—sympathetic activity inhibits digestive processes, and parasympathetic activity stimulates them
Short reflexes from the ENS (local)
long vs. short reflexes and their regulation over the digestive process
short reflexes- reflex pathways are confined to local neurons
long reflexes- must travel outside the local digestive neurons to the CNS to function
3 hormones that participate in regulating digestion
gastrin ( stomach ), secretin ( small intestine ), cholecytokinin (small intestine), gastric inhibitory peptide (small intestine), and motilin (small intestine)
function of hard and soft palate
hard- assists in mechanical digestion
soft- prevent food from entering the nasal cavity
function of the intrinsic and extrinsic muscles of the tongue
intrinsic- control the shape and size of the tongue, push the food against the hard palate during chewing, which assists in mechanical digestion, and also push the bolus posteriorly during swallowing
extrinsic- control the position of the tongue, move the tongue during chewing and help turn the food into a bolus
function of the papilla on the tongue
filiform- assists in mechanical digestion
fungiform, circumvallate, foliate- taste buds
3 major salivary glands
- parotid
- submandibular
- sublingual
components of saliva
water, enzymes, mucus, salivary amylase, lysozyme, secretory IgA, bicarbonate ions, other solutes
functions of saliva
moistening, lubricating, cleansing the oral mucosa. deters growth of bacteria in the oral cavity, mechanical digestion, chemical digestion
roles of the sympathetic and parasympathetic nervous system in regulating saliva production
Sympathetic nerves innervate the salivary glands and their ducts, triggering increased saliva production and facilitating saliva transport through ducts
sympathetic- stimulate mostly mucous cells
parasympathetic- stimulate mostly serous
mastication
the process of chewing during which food is physically broken into smaller pieces by the teeth, tongue and hard palate
structure of the teeth
crown (visible portion), root (embedded), enamel (outer layer of hard mineralized substances), pulp(soft inner gelatinous substance), dentin (inner layer of mineralized tissue in both the root and crown)
region(s) of the pharynx where both food and air pass
oropharynx, esophagus
structure that prevents food from going up into the nose
uvula
structure that prevents food from entering the larynx
epiglottis
type of muscle found in the superior and inferior esophageal sphincters
superior- skeletal
inferior- smooth
deglutition
specialized type of propulsion that pushes a bolus of food from the oral cavity through the pharynx and esophagus to the stomach
peristaltic movement
Peristaltic waves move the bolus down the esophagus to the stomach
This phase begins as the upper esophageal sphincter relaxes. Neurons of the enteric nervous system then stimulate the inner circular and outer longitudinal layers of the muscularis externa to undergo peristalsis and “massage” the bolus inferiorly toward the stomach.
Figure 22.10 gross anatomy of the stomach
Review
function of the gastric folds
Rugae, allow the stomach to expand considerably
Figure 22.11 histology of the stomach wall
Review
Why the stomach has 3 layers of smooth muscle
additional layer of smooth muscle allows the stomach to perform churning, a motion that pummels the food into a liquid called chyme
cells that line the gastric pit
mucous neck cells, parietal cells, chief cells, diffuse neuroendocrine system cells
substances/hormones produced from the different cells of the gastric pit
mucous neck cells- secrete acidic mucus to mucus prevent the mucus from neutralizing the acid produced by other cells known as parietal cells
parietal cells- secrete HCl that activates pepsinogen, destroys most disease causing organisms we digest
cheif cells- pepsinogen (becomes pepsin in contact with acidic pH, begins protein digestion)
diffuse neuroendocrine cells- gastrin and histamine (stimulates acid secretion from parietal cells)
how the stomach protects itself from HCl
Between the gastric pits we find columnar epithelial cells that secrete a thick mucus layer that lines and protects the cells of the stomach from its own secretions
role of HCl
Acid is an important component of gastric juice because it is required to activate a precursor enzyme called pepsinogen (pep-SIN-oh-jen) and also because it destroys most disease-causing organisms we ingest
chyme
liquid mixture that results from the stomach churning a bolus and mixing it with gastric juice
3 phases that regulate digestion in the stomach and how they are initiated
- cephalic phase (sight, smell, taste or even thought of food)
- gastric phase (when food enters the stomach)
- intestinal phase (the presence of partially digested proteins in the fluid entering the duodenum)
3 functions of the stomach
secretion, propulsion, digestion
How might a stomach problem lead to pernicious anemia?
The most common cause of pernicious anemia is the loss of stomach cells that make intrinsic factor. Intrinsic factor helps the body absorb vitamin B12 in the intestine. The loss of parietal cells may be due to destruction by the body’s own immune system
Figure 22.14 Gross Anatomy of the small intestines, know function of each structure
Review
Figure 22.15
Review
villi
folds of the mucosa and submucosa of the small intestine that increase surface area for absorption
microvilli
highly folded extensions of the plasma membrane that increase its surface area for absorption