Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
139 Cards in this Set
- Front
- Back
|
What is the function of the digestive system? |
To supply your cells with nutrients |
|
|
What are the steps in the digestive system? |
*ingestion *mechanical digestion *chemical digestion *secretion *absorption *excretion |
|
|
Name the basic gross anatomy of the digestive system. |
*mouth, teeth, tongue *pharynx *esophagus *stomach *small intestine *large intestine *salivary glands *liver *pancreas |
|
|
What are the names of the 4 layers of the digestive tract? |
*serosa *muscularis externa *submucosa *mucosa |
|
|
What is the serosa? |
*Outer layer of the digestive tract *tough, connective tissue membrane *protection is its function |
|
|
What is the muscular externa? |
*2nd layer of digestive tract *longitudinal and circular muscle layers for contraction |
|
|
What is the submucosa? |
*3rd layer of digestive tract *loose connective tissue, blood vessels, and glands *secretion is its function |
|
|
What is the mucosa? |
It is the innermost layer of the digestive tract and has 3 layers of its own. *muscularis mucosa interna *lamina propria (loose CT) *epithelium lining (digestion/absorption of nutrients) |
|
|
What are the 2 nerve plexuses of the digestive tract? |
*myenteric plexus (auerbach) *submucosal plexus (meissner) |
|
|
Why is the GI tract called "Little Brain?" |
It is able to function independent from the central nervous system |
|
|
What is the myenteric plexus (auerbach)? |
*nerve plexus of digestive tract *neurons net between circular & longitudinal muscle layers *controls contractions of muscularis externa, peristalsis, segmentation, haustration, and mass movement |
|
|
What is the submucosal plexus (meissner)? |
*scattered neurons in the submucosal layer *controls contractions of muscular mucosa (interna) *controls glandular secretion of mucosa |
|
|
What is mastication? |
The breaking of food into smaller pieces to be swallowed. It increases the surface area exposed to digestive enzymes. |
|
|
Contact of food with sensory receptors triggers... |
the chewing reflex |
|
|
What three things manipulate food when chewing? |
*tongue *buccinator *orbicularis oris |
|
|
What elevates the teeth to crush food? |
masseter and temporalis |
|
|
What swing the teeth from side to side in a grinding action of the molars? |
medial and lateral pterygoids |
|
|
What are the constituents of saliva? |
Hypotonic solution of 99.5% water and solutes (salivary amylase, lingual lipase, mucus, lysozymes, immunoglobulin A, and electrolytes) |
|
|
What is the function of salivary amylase? |
Begins starch digestion |
|
|
What is the function of lingual lipase? |
Digests fat and is activated by the stomach |
|
|
Mucus aids in what? |
swallowing by lubrication |
|
|
What do lysozymes do? |
They are enzymes that kill bacteria |
|
|
What is immunoglobulin A do? |
It inhibits bacterial growth |
|
|
What electrolytes are present in saliva? |
Na+, K+, Cl-, phosphate, and bicarbonate |
|
|
What is the function of saliva? |
To moisten, begin starch and fat digestion, clean teeth, inhibit bacteria, bind food together into a bolus |
|
|
Where does starch digestion begin? |
It begins in the saliva with salivary amylase and is secreted by the salivary glands and digests starch into smaller molecules |
|
|
What is the smallest molecule that amylase starch can break food down into? |
disaccharides |
|
|
What structure prevents a food bolus from entering the trachea during swallowing? |
The epiglottis |
|
|
What is peristalsis? |
It is the squeezing contraction that goes progressively down the esophageal tube to squeeze food down the tube |
|
|
What are the four functions of the stomach? |
storage, mechanical digestion, chemical digestion, and limited absorption |
|
|
Describe the storage function of the stomach. |
The stomach can contain large amounts of food from one sitting |
|
|
Describe the mechanical digestion function of the stomach. |
*reduces food to liquid acid chyme by mixing waves *forces small amounts of chyme from stomach into the small intestine |
|
|
Describe the chemical digestion function of the stomach. |
Protein digestion begins by pepsin |
|
|
What is pepsin? |
a protein used in digestion |
|
|
Describe the limited absorption function of the stomach. |
Aspirin, alcohol, electrolytes, water, and some drugs can be absorbed |
|
|
What are rugae? Where are they found? What is their function? |
They are the foldings on the top layer of the muscle wall in the stomach lining and GI tract. The foldings can expand so you don't rupture the mucosa. |
|
|
What are the five different cell types of gastric glands? |
*mucous neck cells *parietal cells *chief cells *regenerative cells *entro-endocrine cells |
|
|
What do mucous neck cells secrete? |
protective surface mucus |
|
|
What do parietal cells secrete? |
HCl acid and intrinsic factor |
|
|
What do chief cells secrete? |
pepsinogen, gastric lipase, and chymocin |
|
|
What do entry-endocrine cells secrete? |
gastric hormones |
|
|
What do regenerative cells produce? |
new cells |
|
|
What is the function of HCl in the stomach? |
*activates pepsin & lingual lipase *breaks connective tissue & plant cell walls *liquifies food to form chyme *converts ingested ferric ions (Fe3+) to ferrous ions (Fe2+) for absorption and use in hemoglobin synthesis |
|
|
What is the relationship between gastric intrinsic factor, vitamin B12, and pernicious anemia? |
If you are deficient in gastric intrinsic factor, you can't absorb vitamin B12--so you are B12 deficient which causes pernicious anemia. B12 is needed to produce and form mature RBCs. |
|
|
What is gastric intrinsic factor? |
*essential for Vit B12 absorption of small intestine *deficiency causes pernicious anemia |
|
|
What do gastric lipase and chymosin do? |
*lipase digests butterfat of milk in infants *chymosin curdles milk by coagulating proteins |
|
|
What is pepsin secreted as? What converts it to pepsin? |
Pepsin is secreted as inactive pepsinogen zymogens and HCl converts it to active pepsin |
|
|
What are the 3 phases of gastric secretion? |
*cephalic phase *gastric phase *intestinal phase |
|
|
What happens during the cephalic phase? |
The vagus nerve stimulates gastric secretion even before food is swallowed. |
|
|
What happens during the gastric phase? |
Food stretches the stomach and activates myenteric and vasovagal reflexes. These reflexes stimulate gastric secretion. Histamine and gastrin also stimulate acid and enzyme secretion. |
|
|
What happens during the intestinal phase? |
Intestinal gastrin briefly stimulates the stomach, but then secretin, GIP, CCK, and the enterogastric reflex inhibit gastric secretion and motility when the duodenum processes the chyme already in it. Sympathetic nerve fibers suppress gastric activity, while vagal (parasympathetic) stimulation of the stomach is now inhibited. |
|
|
What are the 3 named parts of the small intestine? |
Duodenum: connects to the stomach and to the jejunum Jejunum Ileum: longest part of the tract |
|
|
What is the structure and function of villi? |
It lines the small intestine (4.5 million villi). They are small finger like extensions, covered with a simple columnar mucous membrane, blood capillaries inside for absorbing most substances, and single lymph capillary called a lacteal for absorbing most fat |
|
|
What is the function of the small intestines? |
*mechanical digestion *chemical digestion *absorption of most substances |
|
|
What happens during mechanical digestion of the small intestines? |
*peristalsis propels chyme along the intestine *segmentation move chyme back and forth to mix it thoroughly |
|
|
What happens during chemical digestion of the small intestine? |
*enzymes from pancreas and small intestine complete digestion of protein, starch, disaccharide sugars and fat *gallbladder empties bile into small intestine to aid in fat digestion |
|
|
Where does the pancreas empty its secretions into the small intestines? |
The pancreas has a head, neck, body, and tail. The head goes into the duodenum and the tail goes into the spleen. Pancreatic duct joins bile duct and connects to duodenum. |
|
|
What is secreted from the exocrine pancreatic duct cells? |
Cholecystokinin, secretin, and gastrin |
|
|
What is cholecystokinin? Where is it released from? Why is it released? |
It is released from duodenum in response to the arrival of acid and fat. It causes the contraction of gallbladder, secretion of pancreatic enzymes, relaxation of hepato-pancreatic sphincter
|
|
|
What is secretin? Where is it released from? Why is it released? |
It is released from the duodenum in response to acidic chyme. It stimulates all ducts to secrete more bicarbonate. |
|
|
What is gastrin? Where is it released from? What does it do? |
It is from the stomach and duodenum and weakly stimulates gallbladder contraction and pancreatic enzyme secretion. |
|
|
What organ secretes cholecystokinin, secretin, and gastrin? |
the pancreas |
|
|
What are the steps in protein digestion by pancreatic enzymes? (5 steps) |
*enzymes secreted as inactive zymogens *trypsinogen activated to trypsin by entrokinase enzyme from duodenum epithelium cells *chemotrypsinogen activated to chymotrypsin by the trypsin enzyme *procarboxypeptidase activated by trypsin enzyme to carboxypeptidase *activated enzymes digest proteins into small peptides |
|
|
During protein digestion, what activates trypsinogen?
|
entrokinase enzyme activates trypsin which activates trypsinogen |
|
|
During protein digestion, what activates chemotrypsin? |
trypsin enzyme activates chemotrypsinogen which activates to chemotrypsin |
|
|
During protein digestion, what activates carboxypeptidase?
|
trypsin enzyme activates procarboxypeptidase which activates to carboxypeptidase |
|
|
What do activated enzymes do to proteins? |
They digest proteins into small peptides |
|
|
Where is bile produced? |
In the liver |
|
|
Where is bile stored? |
the gallbladder |
|
|
What is the function of bile? |
It emulsifies--breaks fat drops into very small droplets |
|
|
Where is the function of bile carried out? |
Bile from the gallbladder is required for lipase to digest fat more efficiently. Bile flows from the gallbladder down the bile duct into the duodenum to mix with and emulsify the fat. |
|
|
What is the direction of blood flow in the liver? |
Blood is supplied by branches of the hepatic artery. Blood flows toward the center of each lobule through liver capillaries. Blood flows from the capillaries into the central vein in the center of the lobule. |
|
|
What type of capillaries are present in the liver? |
Liver capillaries are called sinusoids. Blood flows toward the center of each lobule through sinusoids. Rows of liver cells surround the capillaries. Blood flows from the capillaries into the central vein in the center of the lobule. |
|
|
What are Kupffer cells? |
They are liver macrophages that are found in the capillaries for phagocytosis. They clean the blood before it goes to the heart |
|
|
What is a hepatocyte? |
They are liver cells with the job of secreting bile |
|
|
What is the function of the liver? |
*carb, lipid, protein metabolism *removal of waste products & detox *storage of glycogen, Vits, and iron *phagocytosis by Kupffer cells *activation of Vit D *bile synthesis and secretion *plasma protein synthesis |
|
|
What is the function of the brush border enzymes on microvilli of intestinal absorptive cells? |
*It digests and absorbs nutrients |
|
|
How are fats, carb, and amino acids absorbed? |
*peptidases digest peptides into amino acids*intestinal lipase digest fats to glycerol and fatty acids *oligosaccharides digest to monosaccharides |
|
|
What is the function of the large intestine? |
*feces formation *limited digestion of undigested food by bacteria *formation of Vit K and some B vitamins by bacteria *absorption of some water, electrolytes, vitamins, and bile salts |
|
|
What do glands of the large intestine produce? |
They produce a lot of mucus |
|
|
Understand motility and absorption. |
*transit time: 12 to 24 hours *feces contains water, bacteria, undigested fiber, mucus, fat, sloughed epithelial cells *haustral contractions *mass movement |
|
|
What is typical transit time? |
Typical transit time is 12 to 24 hours--water and electrolytes are absorbed during this time |
|
|
What are haustra? |
Haustral contractions occur every 30 minutes when stimulated by distension. It moves the feces along the large intestine. |
|
|
What is mass movement? |
Mass movement pushes feces into the rectum. It occurs 1 to 3 times daily and is triggered by gastrocolic and duodenocolic reflexes from the stomach and duodenum filling. |
|
|
What are the basic mechanisms of the neural control of defecation? |
*intrinsic reflex: activates mass movement to fill rectum and stimulate rectal stretch receptors *spinal cord reflex: causes contraction of rectum and relaxation of internal anal sphincter *pudendal nerve reflex: causes conscious voluntary relaxation of the external sphincter and defecation |
|
|
What is the large intestine's role in water balance?
|
It absorbs some water, electrolytes, vitamins, and bile salts 0.8 L is absorbed by the large intestine every day |
|
|
What is gingivitis? |
inflammation of the gums |
|
|
What is periodontal disease? |
inflammations of the teeth, ligaments, and alveolar bones |
|
|
What is stomatitis? |
inflammation of the mouth mucus membranes |
|
|
What is esophagitis? |
inflammation of the esophagus |
|
|
What is dysphagia? |
difficulty of swallowing |
|
|
What is gastritis? |
inflammation of the stomach |
|
|
What is enteritis? |
inflammation of small intestine |
|
|
What is diverticulitis? |
inflammation of the colon |
|
|
What is hepatitis? |
inflammation of the liver |
|
|
What is pancreatitis? |
inflammation of the pancreas |
|
|
What are hemorrhoids? |
permanently distended veins |
|
|
What are cheeks and lips used for? |
*keep food between teeth for chewing *essential for speech and suckling in infants *vestible is the space between teeth and cheeks |
|
|
Describe the tongue. |
It is a sensitive, muscular manipulator of food. Has papillae and taste buds on the dorsal surface. Lingual glands secrete saliva and has tonsils in root |
|
|
What do the hard and soft palate do? |
They allow breathing and chewing at the same time |
|
|
Describe tooth structure. |
Humans have 20 baby teeth and 32 adult teeth. Cementum and dentin are living tissues. Enamel is noncellular secretion formed during teeth development. |
|
|
How many liters of saliva is produced per day? |
1 to 1.5 liters |
|
|
How do cells work during salivation? |
Cells filter water from blood and add electrolytes, amylase, lipase, mucin, and lysozyme to it. |
|
|
Food stimulates receptors that signal salivary nuclei in the... |
medulla and the pons |
|
|
Parasympathetic stimulation does what in salivation? |
Salivary glands produce thin saliva, rich in enzymes |
|
|
Sympathetic stimulation does what in salivation? |
It produces less abundant, thicker saliva, with more mucus |
|
|
Higher brain centers stimulate salivary nuclei, meaning... |
sight, smell, and thought of food cause salivation |
|
|
What pushes a bolus of food from the oral cavity into oropharynx? |
The tongue *we are aware of this phase of swallowing |
|
|
What closes the nasopharynx? |
the soft palate |
|
|
What closes the glottis? |
epiglottis |
|
|
During choking, can a person breath or vocalize? |
No, they can't breath or vocalize |
|
|
What happens during the esophageal phase of swallowing? |
The upper esophageal sphincter opens when swallowing only. Peristalsis propels the bolus down the esophagus toward the stomach. |
|
|
What happens when the cardiac (lower esophageal) opens, what happens? |
The food bolus can enter the stomach |
|
|
Is Fe3+ easy to absorb? If not, what should it be converted to for better absorption? |
Fe3+ (ferric ions) are difficult to absorb and it needs to be converted to Fe2+ (ferrous ions) for better absorption and hemoglobin synthesis |
|
|
The villus has what types of cells in it? |
*simple columnar cells *absorptive cells *goblet cells *endocrine cells *paneth cell of intestinal crypt |
|
|
What do absorptive cells in villi do? |
They are in charge of finishing digestion |
|
|
What are goblet cells? |
They produce a lot of mucus to make chyme slide easily along the intestine |
|
|
What do endocrine cells do? |
They produce intestinal hormones like GIP, CCK, and gastrin. |
|
|
What do panted cells of the intestinal crypt? |
They are macrophages that are capable of eating all micro-organisms or bacteria or anything that can reach the small intestine--they are protective cells of the small intestine |
|
|
What are acini? Where are they found? |
They are exocrine cells that secrete digestive enzymes into the ducts. It is found in the pancreas. |
|
|
What do duct cells secrete and what is their purpose? |
They secrete a bicarbonate solution that buffers the acidic chyme from stomach and raise its pH from 2 to 3 up to 7 to 8 |
|
|
Does the duodenum have a protective mucus cover? |
No |
|
|
Why is chyme acidic? |
Because it is mixed with HCl |
|
|
Describe fat digestion. |
*triglycerides are digested in the small intestine by pancreatic lipase *digestion of each triglyceride yields a monoglyceride molecule and two fatty acids |
|
|
Describe the flow of bile. |
Hepatocytes secrete bile, bile flows from liver through hepatic ducts into the gallbladder, gallbladder stores and concentrates bile, then through the common bile duct, then to the pancreatic duct, then into the duodenum, the jejunum, the ileum, the cecum, the large intestine, and then the rectum...to the anus. |
|
|
Describe lobules in the liver. |
They consist of rows of liver cells and have a rich blood supply. The blood is supplied by branches of the hepatic artery and portal vein at the six corners of each lobule. |
|
|
What does the common bile duct connect? |
the common hepatic duct and the cystic duct from the gallbladder |
|
|
What duct unites with the pancreatic duct? |
the common bile duct |
|
|
What are the three disaccharides? What digests them? And what are they digested into? |
*sucrose:sucrase: glucose and fructose *maltose:maltase: glucose and glucose *lactose:lactase: glucose and galactose |
|
|
What does the small intestine absorb? |
*DNA *RNA *Vitamins *Minerals |
|
|
Describe DNA and RNA absorption in the small intestine. |
*it is hydrolyzed by nucleases to nucleotides *neclosidases and phosphates of the brush border split them into phosphate ions, ribose or deoxyribose sugar, and nitrogenous bases and then they are absorbed |
|
|
Describe the absorption of vitamins in the small intestine. |
*vitamins are absorbed unchanged *Vitamin A, D, E, and K and other lipids are absorbed *B complex and C are absorbed by simple diffusion *B12 is absorbed if bound to intrinsic factor |
|
|
Describe the absorption of minerals in the small intestine. |
*they are absorbed all along the small intestine *Na+ is co-transported with sugars and amino acids *Cl- is exchanged for bicarbonate *Iron and Calcium are absorbed as needed |
|
|
What two things does the large intestine need to be able to do? |
*needs to be big enough to store waste coming in from the small intestine from the ileum *needs mobility to move waste around until it is excreted |
|
|
What is the flow of waste through the large intestine? |
cecum, ascending colon, haustrum, transverse colon, desceding colon, sigmoid colon, external anal sphincter |
|
|
Describe the mucosa in the large intestine. |
They are made of simple columnar epithelium. The have no villi--so they have little to no absorption The glands found here are mucus glands. |
|
|
How is water absorbed in the body? |
by osmosis following the absorption of salts and organic nutrients |
|
|
How many liters of water does the digestive tract receive per day? |
9 L (0.7 L in food, 1.6 L in drink, 6.7 L in secretions) *8 L is absorbed by the small intestine and 0.8 by the large intestine |
|
|
When does diarrhea occur? |
When too little water is absorbed. Feces passes through too quickly if the GI is irritated or the feces contains high concentrations of an unabsorbed solute such as lactose or chloride. |
