Digestive System Flashcards
What controls the rate in which the stomach is emptying?
Pyloric sphincter
What must happen to nutrients?
They must be broken down into smaller components before body can make use of them
What does the digestive system act as?
A disassembly line
What does the digestive system do?
To break down nutrients into forms that can be used by the body
To absorb them so they can be distributed to the tissues
____ is the study of the digestive tract and the diagnosis and treatment of its disorders
Gastroenterology
What is the digestive system ?
organ system that processes food, extracts nutrients, and eliminates residue
What are the 5 stages of digestion?
Injestion, digestion, absorption, compaction, exceretion (defecation)
Digestion is ______
the mechanical and chemical breakdown of food molecules into a form usable by the body
_________ is the uptake of nutrient molecules into the epithelial cells of the digestive tract and then into the blood and lymph
Absorption
____ is the absorbing water and consolidating the indigestible residue into feces
Compaction
____ is the physical breakdown of food into smaller particles
Mechanical digestion
What are 2 examples of mechanical digestion?
Cutting and grinding action of the teeth
Churning action of stomach and small intestines
____ is a series of hydrolysis reactions that breaks dietary macromolecules into their individual monomers
Chemical digestion
Where are digestive enzymes produced?
In salivary glands, stomach, pancreas and small intenstine
Polysaccharides (carbohydrates) are broken down to ____, proteins to ________, lipids to ____ and nucleic acids to _________
Glucose
Amino acids
Monoglycerides and fatty acids
Nucleotides
____ is the muscular contractions that break up and propel food through the canal, mix it with digestive enzymes and eliminates the waste
Motility
____ is the release of digestive enzymes and hormones that carry out or regulate digestion
Secretion
____ is the release of digestive enzymes and hormones that carry out or regulate digestion
Secretion
____ is active transport and facilitated diffusion that absorb nutrients and transfer them to the blood and lymph
Membrane transport
What are the 2 main divisons of the digestive tract?
Digestive tract and accessory organs
What is the digestive tract also called?
Alimentary canal
What are the accessory organs?
Teeth, tongue, salivary glands, liver, gallbladder, and pancreas
What are the tissue layers of the GI tract?
Mucosa, submucosa, muscularis externa and serosa
The epithelium, lamina propria, muscularis mucosae and MALT make up the ______
Mucosa
What makes up the submucosa?
Blood and lymphatic vessels, nerve plexus and glands
What is the muscularis externa composed of ?
Inner circular layer
Outer longitudinal layer
The serosa is the ______
Areolar tissue or mesothelium
What are the 2 nerve networks of the enteric nervous control?
Submucosal and myenteric plexus
The ________ controls glandular secretion of mucosa
Controls movement (contractions) of muscularis mucosae and is found in the submucosa
Submucosal plexus
What NS contriols peristalis?
Myenteric plexus
____________ is a serous membrane that lines the peritoneal cavity of the abdomen and covers the mesenteries and viscera.
Peritoneum
What do the lesser and greater omentum do?
Lesser - attaches stomach to liver
Greater - covers small intestines like an apron
What does the mesentery of small intestine do?
holds many blood vessels
What does the mesocolon do?
anchors colon to posterior body wall
The motility and secretion of the digestive tract are controlled by ______, ______, and __________.
neural, hormonal, and paracrine mechanisms.
Includes 2 automatic reflexes:
short (myenteric) reflexes: swallowing
long (vagovagal) reflexes: parasympathetic stimulation of digestive motility and secretion
neural control in the regulation of the digestive tract.
What are examples of hormones produced by the digestive tract?
gastrin and secretin
What are examples of paracrine secretions?
histamine and prostaglandins
What are the functions of the mouth (oral or buccal cavity)?
Ingestion (food intake)
Taste and other sensory responses to food
Mechanical digestion: chewing
Chemical digestion: begins digestion of carbohydrates and lipids
Swallowing, speech, and respiration
Lubrication: mixing with mucous and salivary gland secretions
What type of tissue lines the mouth?
Stratified squamous epithelium
What do the lingual glands in the tongue do?
secrete saliva, tonsils in root
What is the vestibule?
space between teeth and cheeks
What are the lips/labia divided into?
cutaneous area (mustache area) and red (vermillion) area (lipstick area)
How many baby/decidous teeth do people have by 2 years?
20
How many teeth do adults have?
Adult have (32): 16 in mandible and maxilla
Incisors, canines, premolars and molars
Explain each tooth.
2 incisors—central and lateral
1 canine—pointed and act to puncture and shred food
2 premolars—broad surface for crushing, shredding, and grinding
3 molars—even broader surface for crushing, shredding, and grinding
____ is sticky residue on the teeth made up of bacteria and sugars
Plaque
When is root canal therapy needed?
if cavity reaches pulp
____ is the inflammation of gums.
Gingivitis
________ is the destruction of the supporting bone around the teeth which may result in tooth loss
Periodontal disease
What is the first step of mechanical digestion?
Mastication or chewing
In chewing, the __________, ______, and manipulate food and push it between the teeth
tongue, buccinator and orbicularis oris
In chewing, the masseter and temporalis _____
Elevate the teeth to crush food
What swings the teeth in side-to-side grinding action of molars?
medial and lateral pterygoids
What are some functions of saliva?
moistens the mouth
begins starch and fat digestion
cleanse teeth
inhibit bacteria
moistens food and binds it together into bolus
Is saliva hypertonic or hypotonic?
Hypotonic
What does salivary amylase do?
enzyme that begins starch digestion
What is lingual lipase?
enzyme that digests fat after it reaches the stomach (activated by stomach acid)
What does mucus do?
binds and lubricates a mass of food and aids in swallowing
What is lysozyme?
an enzyme that kills bacteria
What is immunoglobin A?
an antibody that inhibits bacterial growth
What is the pH of saliva?
Between 6.8 to 7.0
What do intrinsic salivary glands so?
secrete small amounts of saliva at constant rate
What are the 3 pairs of the extrinsic glands called?
Parotid, submandibular and sublingual glands
What do the mucous cells do?
Secrete mucus
What do serous cells do?
Secrete thin fluid rich in enzymes (amylase) and electrolytes
Salivary amylase begins to digest starch as food is chewed, which mucus in the saliva binds food particles into a soft, slippery mass called a ________
bolus
What does the esophagus prevent?
Stomach contents from regurgitating into the esophagus
What are the tissue layers of the esophagus?
Mucosa, submucose, muscularis externa
What is the esophagus covered with?
Adventitia
What tissue is the mucosa made of?
nonkeratinized stratified squamous epithelium
What are the stages of swallowing?
Oral/buccal phase (voluntary control)
Pharyngeal phase (involuntary control)
Esophageal phase
In the ____ phase, the tongue forms a food bolus and pushes it into the laryngopharynx.
oral/buccal
In the ____ phase, the palate, tongue, vocal cords, and epiglottis block the oral and nasal cavities and airway while pharyngeal constrictors push the bolus into the esophagus.
pharyngeal
Peristalsis drives the bolus downward, and relaxation of the lower esophageal sphincter admits it into the stomach.
Esophageal phase
____ is a muscular sac in upper left abdominal cavity immediately inferior to the diaphragm
Stomach
What is the resulting soupy mixture in the stoamch when food is broken down, liquidified
Chyme
What does chyme absorb?
aspirin and some lipid-soluble drugs
What are the 4 regions of the stomach?
Cardia (cardial) region
Fundus
Body (corpus)
Pyloric region
What makes up the greatest part of stomach?
Body (corpus)
What does the pyloric sphincter do?
Regulates the passage of chyme into the duodenum
How does innervation occur in the stomach?
Innervation by:
Parasympathetic fibers from vagus
Sympathetic fibers from celiac ganglia
How does the stomach have blood?
Branches of the celiac trunk
All blood drained from stomach and intestines enters ____________ and is filtered through liver before returning to heart
hepatic portal circulation
What is the mucosal tissue of the stomach wall made of?
simple columnar glandular epithelium
What is it called in the mucosa when stomach emptied the mucosa and submucosa layers appear wrinkled
Gastric rugae
What are the 3 layers of the muscularis externa of the stomach wall?
outer longitudinal, middle circular and inner oblique layers
What are the cells of the gastric glands?
Mucus cells, regenerative (stem) cells, parietal cells, chief cells and enteroendocrine cells
What do mucus cells do?
secrete mucus
What do Regenerative (stem) cells do?
Divide rapidly and produce continual supply of new cells to replace cells that die
What do parietal cells do?
secrete HCl acid and intrinsic factor
What do chief cells do?
secrete pepsinogen
chymosin and lipase
What do enteroendocrine cells do?
Secrete hormones and paracrine messengers that regulate digestion
What do G cells produce?
Gastrin
What enzyme do parietal cells contain?
Carbonic anhydrase
What does increase in bicarbonate in the blood cause?
Alkaline tide/increases blood pH
What does HCl activate?
Pepsin and lingual lipase
What does HCl convert?
ingested ferric ions (Fe^(3+) ) to ferrous ions (Fe^(2+) )
What is Fe2+ used for?
Hemoglobin synthesis
How does hydochloric acid contribute to nonspecific disease resistance?
By destroying most ingested pathogens
What is intrinsic factor used for and why is this important?
B12 absorption which is needed for hemoglobin synthesis
____ cells are needed for protein digestion.
Pepsin
What makes gastric lipase?
Chief cells
G cells make ____, which promotes parietal cells to make ______
Gastrin
HCl
What is vomiting?
forceful ejection of stomach and intestinal contents (chyme) from the mouth
What causes vomiting?
Overstretching of the stomach or duodenum
Chemical irritants such as alcohol and bacterial toxins
Visceral trauma
Intense pain or psychological and sensory stimuli
________ is sudden vomiting with no prior nausea or retching
Projectile vomiting
What are the 3 ways the stomach is protected from the harsh enzymatic and acidic environment it creates?
Mucous coat, tight juctions and epithelial cell replacement
What can the breakdown of the protective measures of the stomach result in?
inflammation and peptic ulcer
What are most uclers caused by, and what can this be treated with?
Helicobacter pylori and antibiotics/Pepto-Bismol
What is the gastric activity divided into?
Cephalic, Gastric and Intestinal Phases
In the ____ phase, vagus nerve stimulates gastric secretions and motility just with sight, smell, taste or thought of food
Cephalic
In the ____ phase, duodenum regulates gastric activity through hormones and nervous reflexes
Intestinal
What are the 3 main chemicals the gastric secretion is stimulated by?
Ach, histamine and gastrin
What do the liver, gallbladder and pancreas all do?
All release important secretions into small intestine to continue digestion
How many lobes does the liver have?
4
The sinusoid of the liver contains phagocytic cells called ________
Kupffer cells (hepatic macrophages)
In the liver, the central vein (passes down the core) surrounded by hepatocyte (cuboidal cells) separated by ____________ (blood-filled channels that fill spaces between the plates) which are lined with _________
Hepatic sinusoids
Fenestrated epithelium
What do hepatocytes absorb from the blood after a meal?
glucose, amino acids, iron, vitamins, and other nutrients for metabolism or storage
What do hepatocytes do between meals?
break down stored glycogen and release glucose into the blood
What do hepatocytes remove and degrade?
hormones, toxins, bile pigments, and drugs
What do hepatocytes secrete into the blood?
albumin, lipoproteins, clotting factors, angiotensinogen, and other products
What does the gallbladder do?
stores and concentrates bile by absorbing water and electrolytes
What is bile?
yellow-green fluid containing minerals, cholesterol, neutral fats, phospholipids, bile pigments, and bile acids
____ is the principal pigment derived from the decomposition of hemoglobin
Bilirubin
________ is responsible for the brown color of feces
________ is responsible for yellow color of urine
Sterocobilin and urobilin
When can gallstones form?
if bile becomes excessively concentrated with wastes
The pancreas is both a ____ and a ____ gland.
Endocrine and exocrine
What cells secrete pancreatic juice into the duodenum?
Acini cells
The ____ in the pancreas controls release of both bile and pancreatic juice into the duodenum
Hepatopancreatic sphincter
What are the proteases/zymogens of the pancreas?
trypsinogen
chymotrypsinogen
procarboxypeptidase
What does amylase do?
Digests starches
What does lipase do?
Digests lipids (fats)
What do ribonuclease and deoxyribonuclease do?
digest RNA and DNA respectively
Trypsinogen converted to ________ by _______
Trypsin
intenstinal epithelium
What occurs in the small intestine?
Nearly all chemical digestion and nutrient absorption
The largest pat of the digestive tract is the _____
Small intenstine
What are the 3 regions of the small intestine?
Duodenum, jejunum and ileum
The ____ known as the Mixing bowl” that receives chyme from stomach and digestive secretions from pancreas and liver
duodenum
What does the duodenum neutralize?
neutralizes stomach acids, emulsifies fats, pepsin inactivated by pH increase, pancreatic enzymes
What are peyer’s patches and where are they found?
clusters of lymphatic nodules
in the ileum
What is the microscopic anatomy of the small intestine composed of?
Circular folds, intenstibal vili, microvilli and intestinal crypts
________ are fingerlike projections in mucosa of small intestines
Intestinal Villi
What is Intestinal Villi covered by?
simple columnar epithelium with microvilli
The contractions of small intestine serve three functions, which are _____
- To mix chyme with intestinal juice, bile and pancreatic juice (allows these fluids to neutralize acid and digest nutrients more effectively)
- To churn chyme and bring it in contact with the mucosa for contact digestion and nutrient absorption
- Moves residue towards large intestine
What is the puropose of segmentation in small intestine?
is to mix and churn not to move material along as in peristalsis
What is peristalsis?
The gradual movement of contents towards colon (large Intestnes)
What does the usually closed ileoccecal valve do?
Prevents reflux of fecal contents into the ileum
What does a balanced diet contain?
Carbohydrates
Proteins
Lipids
Nucleic Acids/Vitamins/Minerals
Water
What are digestive enzymes secreted by?
Salivary glands
Tongue
Stomach
Pancreas
What do lipases seperate?
Lipases separate fatty acids from glycerides
________ are absent from saliva but begin working in the stomach
Proteins
____ amylase completes digestion.
Pancreatic
