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Digestive System
Digestive & Metabolism
87
Anatomy
Undergraduate 2
04/24/2011

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Term
digestive system
Definition
- made up of long, muscular tube & glandular structures
- mouth => pharynx => esophagus => stomach => sm. intestine => large intestine => anus
- glandular structures: salivary glands, liver, gallbladder, pancreas (all dump secretions into digestive tube to do job)
- digestion of nutrients & excretion of solid waste
Term
oral cavity
Definition
- also called the buccal cavity; cheeks lined w/ stratified squamous epithelium
Term
teeth
Definition
- deciduous => baby teeth, fall out
- permanent => adult teeth
Term
caries
Definition
cavities, form due to bacteria fermenting carbohydrates which leads to acid waste on the teeth
Term
tongue
Definition
- highly movable, skeletal muscle, frenulum => fold of mucous membrane that attaches tongue to the floor of the mouth
- sensory receptors on surface for taste
- keeps food between teeth, mix food w/ saliva, need for swallowing & speech
Term
hard palate
Definition
- separates the nose from mouth
- palatine process of maxillary bones (fused)
- cleft palate occurs when bones do not fuse => affects feeding & language development
Term
fauces
Definition
- passageway to pharynx
Term
uvula
Definition
- free projection of soft palate, functions in swallowing => closes off passageway to nasopharynx
- 2 muscular folds run down lateral sides of soft palate => palatine tonsils located between the folds
Term
tunica mucosa
Definition
- innermost, mucous membrane layer (epithelium varies based on location)
- in the epithelium, there are numerous tight junctions (stomach/intestines) as well as enteroendocrine cells & glandular cells
- lamina propria => areolar connective tissue, supports epithelium, contains blood & lymph vessels that serve epithelium
- MALT located in tunica mucosa
- contains a thin layer of smooth muscle folds (stomach, intestine)
Term
enteroendocrine cells
Definition
cell in digestive tube that produces a particular hormone
Term
glandular cells
Definition
produce secretions for digestion, "digestive juices"
Term
tunica submucosa
Definition
- underneath mucous membrane layer, consists of areolar connective tissue and a nerve plexus (submucosal plexus/Meissner's plexus) which makes up part of the enteric nervous system
Term
enteric nervous system
Definition
- millions of neurons along digestive tube which contain both sensory & motor fibers (SNS & PNS fibers)
- submucosal plexus serves mucosa & submucosa, functions to stimulate glandular cells and smooth muscle cells of the mucosa
Term
glycogen
Definition
polysaccharide of glucose made by animals
Term
starch
Definition
polysaccharide of glucose made by plants
Term
myoglobin
Definition
loosely binds to oxygen, similar to hemoglobin but works in muscle cells instead
Term
tunica muscularis
Definition
- outermost, composed of smooth muscle, outer layer consists of longitudinal layer of fibers, inner layer consists of circular fibers
- contains the myenteric plexus (Auebach's plexus) which controls the motility of the digestive tube
Term
serosa
Definition
- serous membrane of digestive tube, also known as the peritoneum
- largest of the serous membranes, 2 layers w/ serous fluid between
Term
retroperitoneal
Definition
only anterior surface is covered by peritoneum (ex: kidney)
Term
folds in the peritoneum
Definition
- there are a large number of folds in the peritoneum
- functions:
1) passageway for blood vessels, lymph vessels, and nerves for each organ
2) anchor organs to each other and cavity wall
Term
mesentery
Definition
fold at the small intestine, anchors small intestine to posterior cavity wall
Term
mesocolon
Definition
fold at the large intestine, anchors large intestine to posterior cavity wall
Term
falciform ligament
Definition
fold at the liver, attaches the liver to anterior abdominal wall and diaphragm
Term
lesser omentum
Definition
fold at the stomach and duodenum, anchors those two structures to the liver
Term
greater omentum
Definition
largest of folds, attaches intestines to cavity walls and contains a significant amount of adipose tissue => "fatty apron"
Term
peritonitis
Definition
inflammation of peritoneum by a microbe
* since the peritoneum is involved with every structure of the abdominal cavity, if it is inflammed, it will eventually evolve into a systemic infection
Term
esophagus
Definition
- extends from pharynx to stomach, passes through diaphragm via esophageal hiatus
- posterior to trachea
- wall has 3 layers with modifications
Term
modifications of 3 wall layers in the esophagus
Definition
- covered by fibrous connective tissue instead of serosa
- in mucous membrane layer => stratified squamous epithelium
- at the superior end of the tube there is skeletal muscle, at the inferior end of the tube there is smooth muscle
- at the inferior end of the tube, circular smooth muscle forms a sphincter (lower esophageal/cardiac sphincter)
* regulates passageway of material into stomach & prevents contents of stomach from flowing back into esophagus (acid reflux)
Term
stomach
Definition
- bag that stores meal until small intestine can deal with it
- extends between esophagus and duodenum
- located immediately under the diaphragm
Term
3 regions of the stomach
Definition
- fundus (upper region) - "balloons" to the left
- body (central) - largest
- pyloric antrum - terminal region, opens into the duodenum (this area is fairly constricted)
Term
cardia
Definition
passageway from the esophagus to the stomach
Term
pylorus / pyloric canal
Definition
passageway from the stomach into the small intestine (duodenum)
Term
wall of the stomach (3 layers with modifications)
Definition
- mucosa layer is coated with an alkaline mucous which buffers HCl
- rugae => large folds of tunica mucosa, can see only when stomach is empty, and permit expansion of tunica mucosa
Term
modifications in the mucosal layer of the stomach
Definition
- simple columnar epithelium with invaginations
* gastric pits lined with simple columnar epithelium => some are glandular (gastric glands)
- enteroendocrine cells
Term
components of gastric glands
Definition
- zymogen cell (chief cell) => secrete pepsinogen & gastric lipase
- parietal cell => secrete HCl and intrinsic factor
- mucous cell => secrete mucous
Term
pepsinogen
Definition
inactive enzyme activated by HCl
* pepsin (active form)
* it is a proteolytic enzyme
Term
gastric lipase
Definition
breaks down fat
Term
intrinsic factor
Definition
needed for the intestines to absorb vitamin B12 efficiently
Term
most notable hormones of enteroendocrine cells
Definition
- G cell => secretes gastrin, located in the pyloric antrum / gastrin stimulates secretion of gastric juices and stimulates gastric motility
- D cell => secretes somatostatin / somatostatin inhibits secretion of gastrin
- unnamed cells in the fundic region => secrete gherlin / gherlin stimulates sensation of hunger; levels peak before a meal and decrease during & after a meal
Term
modifications of the muscularis layer in the stomach
Definition
there is a 3rd muscle layer which has an oblique arrangement
Term
small intestine
Definition
- principal site of chemical digestion and absorption, "work horse" of digestive tube
- extends from pyloric antrum of the stomach to the cecum of the large intestine
- has 3 regions: duodenum, jejunum, & ileum
Term
duodenum
Definition
- 1st region of the small intestine, shortest, widest, most fixed, retroperitoneal / receives secretions from liver, gallbladder, & pancreas / served by the celiac artery
* Brunner's glands => secrete mucous rich in HCO3- which buffers HCl coming from the stomach and protects enzymes from denaturation since they are proteins
Term
jejunum & ileum
Definition
- both served by the superior mesenteric artery
- ileum => largest region & terminal, attaches to cecum at the ileocecal valve
Term
modifications in the mucosal layer in the small intestine
Definition
- plicae circulares
- villi
- microvilli
- specialized cells
- paneth cells
- lymphoid nodules
Term
plicae circulares
Definition
permanent transverse folds in the tunica mucosa that increase surface area & cause food in the small intestine to churn/mix
Term
villi
Definition
fingerlike projections into the lumen of the small intestine that increase surface area
* simple columnar epithelium
* in the core of the villus exists a lacteal
Term
lacteal
Definition
blind end lymph capillary associated with a vascular capillary, lacteal absorbs fat whereas a vascular capillary absorbs all other nutrients
Term
microvilli
Definition
fingerlike projections on the apical surface of epithelial cells that increase the surface area of epithelial cells
Term
specialized cells of the small intestine
Definition
- Brunner's glands
- absorptive cells => epithelial cells with microvilli, important with nutrient absorption
- intestinal glandular cells => also known as the crypts of Lieberkuhn, collectively produce intestinal juices with enzymes necessary for digestion
- enteroendocrine cells in the duodenum
Term
enteroendocrine cells in the small intestine
Definition
- secrete secretin and CCK (cholecystokinin) which regulate stomach, pancreas, liver, & gallbladder functions
- GIP inhibits gastric function (juices and motility) and stimulates the release of insulin
Term
paneth cells
Definition
lysozymes, capable of phagocytosis
Term
lymphoid nodules
Definition
Peyer's patches in the ileum
Term
large intestine
Definition
- most materials have already been digested, compact solid waste/elimination
- extends from the ileum to the anus
- attached to cavity wall by mesocolon
- 2 regions: cecum & colon
Term
cecum
Definition
blind end pouch, located on the right lower side of abdominal cavity, attached to ileum @ the ileocecal valve (regulates movement of material from ileum to cecum)
* vermiform appendix - appendix (cecum) => contains lymphoid nodules
Term
colon
Definition
divided into regions: ascending, transverse, descending, sigmoid, and rectum
Term
ascending colon
Definition
moves upward from cecum, right posterior wall of cavity
Term
transverse colon
Definition
right to left side of cavity at the liver
Term
descending colon
Definition
begins at the spleen, down left side of cavity and stops at the iliac crest/pelvic girdle
Term
sigmoid colon
Definition
bent at pelvic girdle
Term
rectum
Definition
terminal portion of the large intestine, at the end of the rectum there is an anal canal that leads to the terminal opening of the digestive tube (anus)
* longitudinal folds in tunica mucosa => "anal/rectal columns" which contain arteries & veins
* 2 sphincters => internal (circularly arranged smooth muscle) & external (bands of skeletal muscle)
* superficial epithelium => keratinized
Term
wall of large intestine
Definition
- all modifications from the small intestine are gone, modifications in the mucosa & muscularis
Term
modifications in the mucosa layer of the large intestine
Definition
goblet cells
Term
modifications in the muscularis of the large intestine
Definition
- longitudinal with 3 bands => taeniae coli
- haustra => pouchlike structures in the wall
- epiploic/omental appendages => bags of peritoneum fileld with fat
Term
salivary glands
Definition
3 pairs: parotid, submandibular, sublingual
* ALL exocrine (drained by ducts at the oral cavity)
* 99.5% water, .05% solute
Term
parotid glands
Definition
subcutaneous region of cheek, anterior and inferior to the ears
Term
submandibular glands
Definition
beneath the base of the tongue
Term
solutes in saliva
Definition
- electrolytes (Na, Cl, HCO3, HPO4)
- IgA
- waste material (urea, uric acid)
- enzymes (lysozymes / salivary amylase & lingual lipase)
* salivary amylase breaks starch down into maltose
Term
secretion of saliva
Definition
- controlled by ANS (SLUD) / PNS speeds up salivary production
- impulses carried through facial & glossopharyngeal nerves
- sensory stimulation (sight, smell, taste, thought) produces more saliva
- chewing on something increases salivation
Term
pancreas
Definition
- large & lobulated, retroperitoneal, posterior to greater curvature of stomach, 3 regions: head, body, tail
- drained by a duct system w/ 2 large ducts: pancreatic & accessory
- has both exocrine & endocrine function
Term
pancreatic duct (duct of Wirsung)
Definition
- larger, when it leaves pancreas => merges with common bile duct (liver)
- CBD empties into duodenum of small intestine after merging
Term
accessory duct
Definition
empties directly into the duodenum
Term
exocrine functions of the pancreas
Definition
units called acini (clusters of glandular epithelial cells => 99% of the pancreas) secrete pancreatic juices that are alkaline (H2O, electrolytes including HCO3, large variety of digestive enzymes), juices drained by ducts, enzymes of juices do job @ duodenum, juice production controlled by secretin & CCK (both stimulate)
Term
endocrine functions of the pancreas
Definition
- pancreatic islets (islets of Langerhans), 3 main types of cells
* alpha
* beta
* delta
- somatostatin
- glucagon
- insulin
Term
alpha cells
Definition
make and secrete the hormone glucagon
Term
beta cells
Definition
make and secrete the hormone insulin
Term
delta cells
Definition
make and secrete the hormone somatostatin (growth hormone inhibiting hormone)
Term
somatostatin
Definition
suppresses release of insulin & glucagon, slows rate of food absorption along digestive tube & enzyme secretion
Term
glucagon
Definition
increases blood glucose levels, target organ is the liver
* secreted on a negative feedback loop involving blood glucose levels
Term
insulin
Definition
decreases blood glucose levels, works at the liver through a negative feedback system
* glucagon & insulin are antagonistic hormones
Term
liver
Definition
- largest glandular structure, under diaphragm, 2 layers: layer of CT covered by peritoneum
- falciform ligament divides the liver into a left and right lobe / right lobe subdivided into the caudate and quadrate lobes
* ALL UNITS SUBDIVIDED INTO HEPATIC LOBULES
Term
hepatic lobules
Definition
functional unit of the liver
Term
hepatocytes
Definition
epithelial cells arranged to form platelike structures, @ center plate exists a central vein
Term
sinusoids
Definition
exist here instead of regular capillaries, lined with fixed macrophages
Term
Kupffer cells / stellate reticuloendothelial cells
Definition
as blood flows through, fixed macrophages remove old formed elements, microbes, and debris
Term
bile
Definition
hepatocytes make and secrete bile => collected by a duct system
Term
bile canaliculi
Definition
tiny tubes located between hepatocytes, eventually merge to form right and left hepatic ducts => merge to form the common hepatic duct which then leaves the liver
Term
cystic duct
Definition
gallbladder is drained by this duct which merges with the common hepatic duct => WHEN MERGED, they become the common bile duct which opens into the duodenum of the small intestine
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