Digestive System Flashcards
Structures of digestive tract
oral cavity, pharynx, esophagus, stomach, SI, LI, Anus
Accessory organs of digestive system
salivary glands, liver, gall bladder, and pancreas, teeth, tongue
Functions of digestive system
Ingestion
Secretion
Mechanical processing
Digestion
Absorption
Defecation
Immune barrier
What are the different motility present in GI tract
ingestion, mastication, swallowing, peristalsis, segmentation
What are the exocrine and endocrine secretions of digestive tract
exocrine; digestive enzymes, HCl, mucus, water, nicarbonate
endocrine: hormones to regulate digestion
Layers of the GI tract are also called:
what are the layers from innermost to outer:
Tunics:
Mucosa
submucosa
Muscular layer or muscularis externa
Serosa or Adventitia
When does bolus become chyme
when mixed with acid in stomach
where does most absorption vs digestion occur
duodenum- digestion
jejunum- absorption
Describe the characteristic of the mucosa (location, layers, etc)
inner secretory and absorptive lining/ layer of digestive tract
may be folded to increase SA
Mucous membrane
Consists of mucosal epithelium and lamina propia
Mucosal epithelium of the _______ can be either ______ or ______ varying on location. Name the appearance of the epithelium in locations
mucosa; stratified or simple squamous
Oral cavity, pharynx, and esophagus are lined
with nonkeratinized stratified squamous cells
(resist stress and abrasion)
*Stomach, small intestine, and large intestine are lined with simple columnar cells (for secretion and absorption)
Describe the layers of the mucosa
consists of simple columnar epithelium were cells are held by tight junctions,
epithelium is supported by lamina propia which is a think layer of connective tissue that contains lymphatic vessels, blood vessels, and sensory nerve endings to nourish epithelium.
External to lamina propia is thin layer of smooth muscle called muscular mucosae
function of muscular mucosae
contraction of muscle fibers change the shape of the lumen and moves the place circulares (small folds)
Describe the submucosa and its contents
above the mucosa, irregular dense fibrous connective tissue(thick, stretchy, difficult to tear)
highly vascular
contains large blood vessels,larvge lymphatic vessels and nerves that form the submucosal plexus
What is function of submucosal plexus
innervates the mucosa and they contain sensory neurons, parasympathetic and sympathetic nerve fibers
What is the third layer of the digestive tract, characteristics and functions
muscularis; consists of 2 smooth muscle layers (inner circular and outer longitudinal muscle layers)
between 2 muscle layers is the myenteric plexus
forms sphincters or valves in some locations (thickened circular muscular layer is seen in sphincters)
circular vs. longitudinal muscle layers
contraction of circular muscle decreases lumen diameter
contraction of longitudinal shortens the length in specific area
contraction of both mechanically processes the food and moves it along the tract (peristalsis)
Myenteric plexus vs. submucosal neural plexus
Submucosal plexus is in submucosa where there are glands so it is involved with control of secretions in DI tract
myenteric plexus is in muscularis in between 2 muscle layer (circular/longitudinal) it is involved with contraction of both muscle layers
Common physical characteristic of both the mucosa and submucosa
both contain glands that secrete secretions through ducts to epithelial surface of lumen
Outermost layer of DI tract, characteristics/functions
serosa;
where is serosa found/ not found. what do these other structures have instead and why
found only within peritoneal cavity not in pharynx, esophagus, and rectum which are covered by fibrous adventitia
adventitia is a dense network of collagen fibers, very thick to anchor the organs to nearby structures
The peritoneum consists of the serosa or ______ and the _______ continuous with each other. ________ lubricates the serial surfaces. Organs located within the peritoneum are_______.
visceral peritoneum, parietal peritoneum
serous fluid
intraperitoneal
name the different organs associated with the peritoneum and their locations
intraperitoneal: within the peritoneum; stomach jejunum ileum, spleen, transverse colon, liver
retroperitoneal: not surrounded by peritoneum; kidney, abdominal aorta, ureters,
secondary retroperitoneal: start within but then pushed out;pancreas and last 2/3 of duodenum
What are mesenteries; name them and there corresponding organ
folds of the peritoneum, responsible for anchoring each digestive organ in place
transverse mesocolon—> transverse colon in place
falciform ligament —>liver to diaphragm
lesser omentum —> liver to stomach
greater omentum —>stomach to transverse colon
mesentery proper —> SI in place
sigmoid mesocolon —> LI in place
greater omentum hangs over______ and contains thick layer of _______ that serves as______,______, and ______.
hangs like apron over intestines, contains thick layer of adipose tissue for energy reserve and padding protection and insulation against heat lost
what is peristalsis and segmentation and what are they controlled by
peristalsis- muscular layer propels bolus through DI tract in a series of peristaltic waves
Segmentation: material is churned and fragmented
movements controlled by myenteric reflexes of the enteric nervous system
structures within oral cavity
tongue, uvuala, palatal arches, salivary glands, teeth
Epithelium in oral cavity
non-keratinized stratified epithelium
roof of mouth consists of ____ and separates the oral cavity from _____.
_____ separates the oral cavity from nasopharynx.
the floor of the oral cavity consists of_____
hard palate; nasal cavity
soft palate
tongue
The space between the oral cavity and the oral pharynx;
____ guards the opening to the oral pharynx and blocks food from going down the throat too soon. When swallowing the _____ and ____ more up to block the nasopharynx
fauces
uvula
uvula and soft palate
Where does digestion begin and why
mouth; saliva contains salivary amylase to start digestion of starch and also contains muscus
functions of tongue
mechanical digestion (pushes food against palate), manipulation of food, sensory analysis, secretion of enzymes aiding in fat digestion, speaking
What is the frenulum
folds of skin in midline of lip that holds the lips in place . frenulum of Tonge keeps the tongue forward so it doesn’t roll back into pharynx
____ surround each tooth. Teeth are embedded in maxilla and mandible bone, their function is ______.
gingiva/gums, mechanical digestion
what are the pairs of salivary glands? How do they alter the salivary compisition?
parotid gland: 25% of saliva (serous) biggest salivary gland
sublingual gland: 5% of saliva (mucous) smallest salivary gland
submandibular gland: 70% of saliva (mucous+ serous saliva)
ALL 3 GLANDS PRODUCE SALIVARY AMYLASE (PARTIAL DIGESTION OF CARBS)
What are the types of saliva? describe their composition
mucous saliva is very thick and acts as binding agent to put what we are chewing together
serous saliva is water and enzymes is water and enzymes (salivary amylase)
Saliva consists of water, ins, buffers, and salivary amylase
What are the swallowing phase
buccal phase: conscious decision, tongue movement forcing bolus towards pharynx
pharyngeal phase: no conscious control, epiglottis covers glottis and the larynx, bolus moves from pharynx to esophagus
esophageal phase:once food passes upper esophageal sphincter it closes preventing regurgitation
Describe the the positioning of the esophagus to reach the stomach
passes behind heart, anterior to vertebrae, crosses diaphragm through esophageal hiatus, enters peritoneal cavity and reaches stomach
The layers of the esophagus are _______. esophagus is lined with_____. Upper esophagus, mouth, and pharynx are innervated by ______ while the Lower esophagus is controlled by _____ because as you go down the esophagus ______ decreases and _____ increases which is what pushes bolus towards stomach through ______ movement. ______ OPENS TO pass bolus into stomach. Esophagus is innervated by______
Adventitia, muscularis, submucosa, mucosa.
non-keratinized stratified squamous epithelium
somatic motor neurons;ANS; skeletal muscle fibers decrease; smooth muscle; peristaltic movement. Lower esophageal sphincter
VAGUS NERVE
The outside/white part of the teeth is called _______ it is covered by _______ that makes it white. Inside of the gingiva is _______. The ________ surface is the top part of tooth, where upper and lower teeth connect. Little part of tooth that is part of the gum line is called______
crown;enamel (hardest part of the body)
root
occlusal surface
neck
The gums or ________ help protect the tooth and form a cushion around it. Surrounding the root of the tooth is ______ that anchors the tooth to the ________ ______ that holds the tooth in the alveoli bony cavity that the tooth sits in.
gingiva
cement; periodontal ligament
There are no live cells in enamel it is tightly packed ______, only the ____ is covered in it. There are no live cells to prevent______. Under enamel there is _____ that is as hard as bone and consists of calcium carbonate and calcium phosphate. This has tubules that help transmit nutrients from the ______ to the enamel to keep teeth strong and healthy. The _____ contains blood vessels and nerves it is innervated by the ______ and ____ branch of the trigeminal nerve. For the nerves and blood vessels to reach the _____ they must puss through the _____ canal.
calcium phosphate, only the crown is covered by it
infections
dentine
pulp cavity x2; maxillary and mandibular
pulp cavity ; root canal
Functions of the stomach
storage of food
mechanical digestion through segmentation
chemical (protein) digestion
kills bacteria in food (acid)
moves food into SI in the form of chyme
very little digestion occurs here
The stomach consists of
lower esophageal sphincter—>cardiac—>fundus—>body—>pylorus—>pyloric sphincter
greater/ lesser curvatures and greater/lesser omentum
Greater omentum extends from the greater curvature and drapes across surface of the SI
Lesser omentum extends from lesser curvature of stomach to liver
lining has folds —>rugae (has gripping texture aiding in churning)
Smooth muscle layers of stomach
circular, longitudinal, and oblique muscles
The stomach is lined with ______ epithelium. ______ cells protect stomach from acidic environment by producing mucus.
simple columnar
mucous epithelial cells
In mucosa of stomach are entrances called_____ that go deep into mucosa where we find _______ that have specialized cells that secrete acid, enzymes, and hormone gastrin. On neck of gastric pit are ____ cells that produce mucous that lubricates food entering stomach. Deep into gastric pit are ______, ______, _____ cells.
gastric pits
gastric glands
mucous neck cells
parietal, chief, g cells
Associate each cell found in stomach to its function:
1. parietal cells
2. chief (zygomatic) cells
3. g cell
4.Enterochromaffin-like (ECL) cells
5. D cell
6. goblet (mucous) cell
7.P/D1 cells
- secrete HCl helping with chemical digestion of bolus and killing pathogens and intrinsic factor that helps SI absorb B12
- secrete pepsinogen that when mixed with HCl becomes pepsin
- secrete gastrin, stimulates chief +parietal cells , and contraction of muscle in stomach (activated by vagus nerve)
- secrete histamine and serotonin
- secrete somatostatin
- secrete mucous to protect lining
7.secrete hormone gherkin that signal brain to regulate hunger
In stomach are _______, when the pH is too ______ then g cells stop being activated therefore so do _______ +________.
There is _______ absorption in the stomach due to ________
chemoreceptors; low; chief and parietal cells
little to no; thick mucous layer
HCl is producied in parietal cells located in the gastric glands of stomach. CO2 diffuses into parietal cell an enzyme (carbonic anhydrase) turns co2 and water into carbonic acid. The carbonic acid dissociates into bicarbonate and H+, the bicarbonate is transported back into blood. There is an ion exchange molecule in plasma membrane of cell that exchanges bicarbonate going out for chloride going in.
H+ is actively transported into the duct of the gastric gland and the Cl- diffuses with the H+. K+ ions are counter transported into the parietal cell in exchange for the H+ ions. The overall result of this process is
the production of HCl in the parietal cells and its secretion into the ducts of the gastric gland therefore the gastric juices while secreting bicarbonate in the blood
Functions of HCl and pepsin
HCl drops pH to 2 which is the optimal pH for pepsin activity
HCl denatures ingested proteins allowing access to enzymes
HCl converts pepsinogen to pepsin
Pepsin catalyzes the hydrolysis of peptide bonds in the ingested proteins
Acid and pepsin could damage the stomach lining. What are defenses that help prevent this
-Adherent layer of mucus with alkaline bicarbonate
-tight junctions between epithelial cells
-rapid epithelial mitosis that replaces the epithelium every 3 days
Proteins begin digestion in the
starches begin digestion in the _____ but amylase is not active at ______ present in stomach so it becomes ________.
The only common substances absorbed in the stomach are______ and ____ this is due to _____. These substances can cause damage to the ______ and cause bleeding therefore must be avoided by those with gastric ulcers.
stomach
mouth; pH 2, inactivated by the high acidity of gastric juices
alcohol and NSAIDs (nonsteroidal anti-inflammatory drugs) (aspirin); high lipid solubility
gastric mucosa
Food entering the SI causes release of _____ and ___ . CCK inhibits stomach ______, preventing more chyme from being released and stimulate contraction of smooth muscle in _____. CCK also stimulates ______ to release digestive enzymes into _________ of SI.
Secretin stimulates release of ______ to neutralize chyme.
CCK and secretin.
contraction; gall bladder
pancreas; duodenum
buffers
SI starts at the _____ sphincter and ends at the _______ ______. Its 3 sections include _______. The ______ is folded into vilii and the ______ is folded into microvilli increasing the surface area for ______
pyloric sphincter;ileocecal valve
duodenum; jejunum, ileum
mucosa; epithelial plasma membranes; absorption of nutrients
Functions of the SI, what is absorbed in each region
complete digestion carbs, proteins, and fats
absorption of nutrients:
sugars, lipids, amino acids, calcium and iron are absorbed in jejunum
bile salts, b12, water, electrolytes in ileum
very rapid absorption due to villi and microvilli
DIGESTION+ABSORPTION
Layer of Si
mucosa, sub mucosa, muscularis, serosa
SI has circular folds with villi on top. One villus is lined with ______ cells and ______ cells. On the middle of each villus is _____ that has blood vessels and lacteals (lymphatic vessels of SI). Most nutrients are absorbed into blood vessels while _____ are absorbed into lacteals then transported to lymphatic vessel and then the left subclavian veins.
columnar epithelial cells and goblet cells.
lamina propia
lipids (fatty acids, cholesterol, lipid-soluble vitamins (A,D,E,K)
In duodenum at base of villi are ______ responsible for secreting large amounts of mucus that neutralize acidic chyme.
Jejunum has more pronounced ______ for increased absorption.
In Ileum the ______ + ______are reduced and there are________present that guard the SI from bacteria in LI
duodenal submucosal glands (brummer’s glands)
circular folds
circular folds + villi;lymphoid nodules (peers patches)
Smooth muscle of ______ controls the release of secretions: bile from the liver and gallbladder via common bile duct /buffers and digestive enzymes from pancreas via pancreatic duct
sphincter of oddi
The plasma membranes of the microvilli contain enzymes called ____, that hydrolyze disaccharides, poly peptides and other substrates. They are not released into lumen but stay attached to plasma membrane with active site exposed to chyme.
brush border enzyme
What causes lactose intolerance
inability to digest the disaccharide lactose into glucose and galactose for SI to absorb.
Digestion of lactose requires enzyme lactose (brush border disaccharidases)
accumulation f lactose in intestine produces gas, bloating, diarrhea, nausea
Brush border enzymes
Disaccharidase Brush border enzymes
Sucrase, Maltase, Lactase
Digests sucrose to glucose and fructose;
Digests maltose to glucose
Digests lactose to glucose and galactose
Peptidase Brush border enzymes
Aminopeptidase, Enterokinase
Produces free amino acids, dipeptides, and tripeptides
Activates trypsin (and indirectly other pancreatic juice enzymes);
Phosphatase Brush border enzymes
Ca2+, Mg2+-ATPase Alkaline phosphatase
Needed for absorption of dietary calcium; enzyme activity regulated by vitamin D
Removes phosphate groups from organic molecules; enzyme activity may be
regulated by vitamin D
Describe the motility present in SI
peristalsis is weak therefore movement of food is much slower
segmentation is stronger, serves to mix chyme
smooth muscle contractions occur automatically
Regions of LI
ileocecal valve–> cecum–> ascending colon–> transverse colon–> descending colon–> sigmoid colon –>rectum–> anal canal–> anus
LI functions
absorption of water, electrolytes, vitamin K, some b vitamins, storage of feces, production of vitamin K and B vitamins via microbial organisms, compacts waste into feces
LI contions ____ that breakdown food residues and make available important vitamins such as ______. Major bacteria in LI _____
intestinal flora; vitamin k
E.coli
breakdown of food generates______. Feces is stored in
flatulence
sigmoid colon
Made up of Circular muscle layer of LI is called______
longitudinal muscle layer of LI______
haustra
taenia coli-aids in peristalsis
There is no _____ in LI therefore there is not much absorption here. The lining of the LI is ______. Between epithelium are goblet cells and intestinal gland that secrete juice
villi
simple columnar epithelium
anal canal has ___ that lubricate feces as it is forced out
mucous glands
Most absorption occurs in ______ but some is left for ______. Not all water is absorbed _____ is left per day to be _____ with feces. The largest concern with diarrhea is dehydration due to ______.
SI;LI
200 mL
fluid loss
The largest abdominal organ is the ____ it is located on the _____ side and is divided into _____ lobes
liver, right, 4
______ and ____ ligaments hold the liver to the diaphragm. THE _____ ligament divides the right and left lobe. ______ ligament formed by degeneration of fetal umbilical vein
right and left coronary ligaments
falciform
round
The liver is only _ cells thick. Liver cells or _______ form________that are separated from each other by large capillary spaces called _____ which are very _____. The spaces also contain phagocytic _______ cells (immune/infection).
The liver has regenerative properties due to the ability of hepatocytes to convert to progenitor cells that can divide and convert back to hepatocytes, when original mass is restored cell division ceases. This ability is seen with toxins or infections however they cause fibrotic deposits of collagen that protect hepatocytes from toxic damage however excessive collagen and scarring alter liver function.
Hepatic damage due to alcohol or viral hepatitis causes liver ___ that can lead to cirrhosis of liver (permanently damaged and scarred).
hepatocytes; hepatic plates
sinusoids, very permeable
kupffer cells
fibrosis
hepatic plates aree arranged as lobules . In the middle of each lobule is a central vein and at the periphery of each lobule are branches of the hepatic portal vein and of the hepatic artery both of which open into the sinusoids between hepatic plates.
Products of digestion absorbed in intestines are delivered to the liver via the hepatic portal vein. The hepatic portal vein then carries the products of go tract to capillaries in liver. After passing through the second capillary bed of liver sinusoids it then enters general circulation through the hepatic vein that drains the liver.
Liver also receives arterial blood from hepatic artery.
Hepatic Portal system
intestinal capillaries—> portal veins—>hepatic capillaries—>central veins (hepatic vein)
The hepatic portal vein drains the capillaries of the intestine, pancreas, gallbladder, omentum and spleen 75-85% of blood flow to liver. Blood from intestines allows hepatic portal vein to deliver nutrients and other absorbed molecules to the liver. Hepatic artery supplies remaining 20-25% of blood flow to the liver. Arterial blood flow is adjusted to compensate for changes in the blood flow through hepatic portal vein. Therefore total hepatic blood flow is maintained at about 25% cardiac output . Relatively constant hepatic blood flow is necessary to maintain hepatic clearance- the ability of the liver to remove substances from blood.
bile secreted by hepatocytes is released into bile canaliculi within each hepatic plate, which drains into bile ducts in the periphery of each portal lobule, then to hepatic ducts away from liver
Liver functions
1-bile production and secretion ( 250-1500mL/day)
2-detoxification of blood (can remove hormones, drugs, and other substances by excreting in bile, phagocytosis by kupffer cells lining sinusoids, chemically altered by hepatocytes)
3-bile salts (aggregate to form micelles and thus emulsify fats)
4-secretion of glucose, triglycerides, and ketone bodies( carbohydrate/lipid metabolism)
(liver keeps balance of blood glucose by removing glucose and storing it as glycogen (glycogenesis) and triglycerides (lipogenesis) Liver can also make glucose from amino acids gluconeogenesis)and convert fatty acids into ketones(ketogenesis)
5. Production of plasma protein (protein synthesis)
plasma albumin and most plasma globulins, clotting factors (I, II,V,VII,IX,XI) and angiotensinogen are produced in the liver
functions of globulins
transport of cholesterol and triglycerides, transport of steroid and thyroid hormones, inhibition of trypsin(breaks down proteins in duodenum ) activity and blood clotting
bile is composed of
bile pigment (bilirubin)-enterohepatic circulation (recirculate between the liver and intestine)
bile salts -emulsification of fats
phospholipids (lecithin)
cholesterol
inorganic ions
In the ____- are the hepatic portal vein, hepatic artery proper and common bile duct
porta hepatitis
gallbladder functions
store and modify bile
if it gets filled up water is removed and it becomes more concentrated
Pathway of bile
liver—>bile ducts—>common hepatic duct—>cystic duct—>gallbladder—>cystic duct—>common bile duct—>sphincter of oddi
common bile duct connects to sphincter of oddi which only opens in the presence of _______ and _____. When bile backs up it is stored in gallbladder when chyme passes from stomach to duodenum this causes _____- cells to release CCK AND secretin inhibiting stomach contractions preventing more chyme from being released and stimulating contraction of smooth muscle in _____-
chyme +CCK
enteroendocrine cells
gallbladder
Pancreas is in _____ _____ quadrant behind the _____. Its 3 parts consist of ____. Has both functions —
left upper;stomach
head, body, tail
endocrine exocrine
describe the endocrine and exocrine functions of pancreas
endocrine: islets of langerhans cells (pancreatic islets) make insulin and glucagon
exocrine: acinar cells (pancreatic acini) make pancreatic juice which is delivered to the duodenum via the pancreatic duct
pancreatic juice composition and functions
a lot of water, bicarbonate, 20 digestive enzymes, that can digest lipids, nucleic acids, carbohydrates, proteins,
why are digestive enzymes released as zymogens
to prevent auto digestion of pancreas
List if pancreatic enzyme has zymogen, activator and name action
trypsin
phospholipase
lipase
amylase
ribonuclease
deoxyribonuclease
- trypsin; trypsinogen;enterokinase; cleaves internal peptide bonds
- phospholipase;prophospholipase; trypsin; cleaves fatty acids from phospholipids such as lecithin
- lipase; none;none; cleaves fatty acids from glycerol
- amylase; none;none; digests starch to maltose and short chains of glucose
5.ribonuclease; none;none; cleaves RNA to form short chains
6.deoxyribnuclease; none;none; cleaves DNA to form short chains
pancreatic enzymes are inactive until they reach ______. ______ activates trypsinogen to trypsin to digest ______. Trypsin activates other enzymes
SI
enterkinase;proteins
