Digestive System Flashcards
Name in order the organs of the alimentary canal, beginning at the mouth
Mouth
pharynx
esophagus
stomach
small intestine
large intestine
rectum
Name and describe the general function of the accessory digestive organs.
Teeth - mechanical breakdown
Tongue - propulsion (swallowing)
Salivary Glands - propulsion (swallowing)
Liver - secretes bile
Gallbladder - holds the bile
Pancreas- has juice that has enzymes that
Identify and describe the 6 basic activities performed by the alimentary canal (e.g.,
ingestion) which aid the digestive process.
1.) ingestion - taking food into the digestive tract
2.) propulsion :
*swallowing (voluntary) -
*peristalsis (involuntary) - alternating waves of contraction and relaxation to propel food along the tract, some mixing occurs
3.) mechanical digestion- increases surface area of food. chewing, and mixing food with saliva by the tongue, churning food in the stomach, and segmentation (rhythmic local constrictions of the small intestine). It mixes foods with digestive juices and makes absorption easier by moving the food among the intestinal walls.
4.) (chemical) digestion - enzymes secreted in the lumen (cavity) of the alimentary canal break down food into their building blocks
5.) absorption - passage of digested end products : vitamins, minerals, water from the lumen of the GI tract through mucousal cells by active or passive transport into the blood or lymph
6.) defecation - eliminates indigestible substances from the body
Identify and describe the four tissue layers of the alimentary canal wall.
innermost to outermost
- mucosa
- protects underlying tissue (including nonspecific defense)
- absorbs digested material
- and/or secretes mucous, digestive juices, hormones
*epithelium- the innermost layer ; may be simple or stratified ET (stratified near places of abrasion, rectum )
*lamina propria - areolar CT layer which lies deep to the ET ; contains blood vessels, sensory nerve ending, lymph vessels & scattered lymphoid tissues (MALT & tonsils)
*muscularis mucosae - layer of muscularis smooth muscle which is present in most parts of the alimentary canal ; produces folding (which increases mucousal surface area) and local movements (which change the shape of the lumen)
- submucosa
- composed of loose CT which immediately surround the mucosa, richly supplied with blood vessels, lymphatics, and nerves
- has a vascular network that carries away absorbed nutrients
- nerves in the layer form the sub mucosal plexus (part of the enteric nervous system) : helps coordinate and regulate movements of the mucosa, vasoconstriction/vasodilation of local blood vessels, and secretory function of digestive glands - muscularis externa - in the mouth and pharynx, this is made of skeletal muscle
- other parts of the alimentary canal is made of two layers of smooth muscle: - inner circular layer
- superficial longitudinal layer
-contractions of these layers mixes and propels food along the alimentary canal
– at certain point along the canal, the circular layer is thickened, forming sphincters, which prevent back flow of materials
*forms the myenteric plexus :
- contains both the enteric and ANS fibers
- regulates motility (movement/contraction patterns) of the tract walls
- regulates glandular secretion into the lumen
4.serosa
- forms the outermost layer of the organs in the peritoneal cavity
- composed of mesothelium (simple squamous epithelium) and underlying areolar CT (in esophagus and rectum, its replaces by adventitia)
peritoneum - serous membrane of the abdominopelvic cavity
- about 7L/day of peritoneal fluid is secreted and reabsorbed by the peritoneum
ASCITES - abnormal accumulation of peritoneal fluid in the peritoneal cavity, can cause abdominal bloating and accompanies, heart failure, liver and kidney disease etc
Identify and describe the two basic motility patterns of the alimentary canal.
peristalsis- ADJACENT segments of the alimentary canal organs, alternate between contracting then relaxing
*moved distally along the tract (propulsive) but some mixing may occur
segmentation- NONADJACENT segments of the alimentary canal organs contract then relax
*food moved forward then backward
* mainly mixes food, and breaks it down mechanically, some propulsion may occur
In what way do each of the motility patterns (#5) contribute to the digestive process?
esophagus - only peristalsis
*moved distally along the tract (propulsive) but some mixing may occur
stomach - segmentation
*food moved forward then backward
* mainly mixes food, and breaks it down mechanically, some propulsion may occur
What is the splanchnic circulation?
the arteries that branch off the abdominal aorta to serve the digestive organs and the hepatic portal circulation
Identify the main blood vessels of the splanchnic circulation. What organs are served by
each of the blood vessels named?
branches of the celiac trunk: left gastric artery, splenic artery, common hepatic artery
mesenteric arteries - serves large and small intestine
hepatic portal circulation - collects nutrient rich venous blood draining from the digestive viscera and delivered to the liver
Name and locate the two nerve plexuses that make up the enteric nervous system
submucosal- in the submucosa
myenteric plexuses - in muscularis externa
What is the general function of the enteric nervous system?
regulates digestive system activity
How are motor impulses of the parasympathetic nervous system conducted to the GI
tract? What is the general effect of parasympathetic input on digestive function?
Through long reflex arcs.
They involve CNS integration centers and extrinsic autonomic fibers. the GI tract receives parasympathetic motor fibers from the ANS.
Intiated by stimuli from inside or outside the GI tract
parasympathetic NS - enhance digestion
How are motor impulses of the sympathetic nervous system conducted to the GI tract?
What is the general effect of sympathetic input on digestive function?
They involve CNS integration centers and extrinsic autonomic fibers. the GI tract receives sympathetic motor fibers from the ANS.
Intiated by stimuli from inside or outside the GI tract sympathetic NS - inhibits digestion
What is a mesentery? Describe the difference between intraperitoneal and retroperitoneal.
a fused, double-layer or partial peritoneum
1. connects visceral & partial peritoneum
2. anchors organs
3. encases lymphatics, blood vessels, and nerves
intraperitoneal - within the peritoneal cavity
retroperitoneal organs - adhere to dorsal abdominal wall- have no surrounding mesentery
Distinguish between the following serous membranes: visceral peritoneum, parietal
peritoneum, mesentery, greater omentum, lesser omentum, mesocolon.
visceral peritoneum -
parietal peritoneum -
mesentery - a fused, double-layer of partial peritoneum
greater omentum & lesser omentum - are double folds of mesentery that have special names, attach to (And extend from) the greater and lesser curvatures of the stomach, respectively
mesocolon- a dorsal mesentery that secures the late intestine to the parietal peritoneum of the posterior abdominal wall.
Describe the composition and 4 function(s) of saliva.
electrolytes (Na, K, CI, PO4, HCO3-)
enzymes: amylase and lingual lipase (more minor contributor tho)
proteins: mucin, lysozyme, IgA
metabolic waste: urea and uric acid
- cleanses the mouth
- dissolves food chemicals so they can be tasted
- moistens food and helps compact it into a bolus
- has the enzyme amylase that begins the digestion of starchy foods
How is the secretion of saliva controlled?
by the parasympathetic (increases amount of watery saliva) and sympathetic divisions (release of thick mucin-rich saliva) of the ANS system (impulses sent to the facial CN and glossopharyngeal CN)
Humans have two dentitions. What are they?
primary (deciduous teeth) (milk/baby teeth)
permanent dentitions
When do each of the dentitions normally begin to appear? At what age are they
typically complete? When complete, how many teeth does each contain?
primary
* lower central incisors first appear at 6 months, teeth keeps erupting every one to two months until around 20 to 24 months
permanent : 32 in a full set
- primary falls out around 6 to 12 because the roots are absorbed
- wisdom teeth emerge between 17 to 25
Describe the structure and function of the esophagus.
muscular tube about 10 inch (25 cm)
same structure as the alimentary canal: (innermost to outermost)
- mucosa
- submucosa
- muscularis externa
- adventitia
a conduit to pass food from the mouth to the stomach
What purpose is served by the lower esophageal sphincter?
prevents gastric reflux, is at the area where the esophagus meets the stomach
Describe the swallowing reflex –noting especially the stimuli which trigger swallowing
and the motor responses involved.
phase 1: buccal phase - the upper esophageal spinchter is contracted (closed)
- the tongue presses against the hard palate, forcing the food bolus into the oropharynx
VOLUNTARY
phase 2: pharyngeal-esophageal phase - blocking happens, the soft palate and usual rise, blocking off the nasopharynx. the epiglottis, blocks off the trachea.
-then the upper esophageal spinchter relax and food enters the esophagus
phase 3: pharyngeal-esophageal phase continues:
pharynx contracts, pushing the food down
the sprinter contracts again
phase 4: peristalsis pushes to the food to the stomach
phase 5: the gastroesophageal spinchter surrounding the cardia opens, and closes after food enters the stomach to prevent regurgitation
INVOLUNTARY
