Digestion Flashcards

1
Q

What organs are included in the alimentary canal? What is the function of this continuous structure?

A

Mouth, pharynx, esophagus, stomach, small intestine, large intestine. The function of these organs is to pull nutrients out of our food to nourish the body.

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2
Q

What are the accessory digestive organs?

A

The liver, gall bladder and pancreas.

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3
Q

Ingestion

A

which just means eating.

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4
Q

Propulsion

A

means moving food through the system. This includes swallowing and peristalsis, which is the contraction of the involuntary smooth muscle surrounding the organs of this system.

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5
Q

Mechanical breakdown of food

A

increases the surface area of the food for enzymes to work on it. This includes chewing, mixing the food with saliva and segmentation.

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6
Q

Segmentation

A

is the contraction of the circular layer of smooth muscle. This swishes the food back and forth within one section of the intestine, making sure that all nutrients have a chance to come into contact with the cells lining the intestine, so that they can be absorbed.

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7
Q

Digestion of food

A

refers to the enzymes working on the food, breaking it into its monomers (monosaccharides for carbs, amino acids for proteins, fatty acids and glycerol for lipids and nucleotides for nucleic acids.

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8
Q

Absorption

A

refers to how these monomers move from the intestine into the body (blood and lymph). They are absorbed into the cells that line the intestine.

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9
Q

Defecation

A

refers to eliminating any waste that is left over from this process.

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10
Q

What membrane lines the wall of the abdominopelvic cavity? Lines the organs of the cavity?

A

Parietal peritoneum lines the wall of the abdominal cavity. The visceral peritoneum lines the organs in this cavity.

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11
Q

What is a mesentery and what are their functions?

A

A mesentery is a double layer of peritoneum fused together. These anchor organs to the wall of the body cavity.

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12
Q

What is the retroperitoneal cavity? What organs are found there?

A

Retroperitoneal organs lie behind the peritoneum. They don’t have a mesentery, but adhere to the dorsal wall of the cavity.

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13
Q

What are the four layers of the digestive tract?

A

Mucosa, sub-mucosa, muscularis and serosa.

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14
Q

What are the functions of the mucosa?

A

To secrete mucous, enzymes and hormones, to absorb nutrients from the products of digestion and to protect against disease (there are MALT tissues here).

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15
Q

What are the three layers of the mucosa?

A

Simple columnar epithelium, lamina propria and the muscularis mucosae.

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16
Q

What type of epithelium lines the digestive tract?

A

Simple columnar epithelium.

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17
Q

What type of tissue is the lamina propria made out of?

A

Areolar C.T. This brings blood supply to the epithelial cells and contains the MALT tissues to protect against bacteria that can enter with your food.

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18
Q

Describe the submucosa.

A

The submucosa is made out of areolar connective tissue. It has blood and lymph supply, MALT tissues, nerve fibers and many elastic fibers.

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19
Q

Describe the muscularis externa.

A

There are two layers of smooth muscle here. The inner layer is longitudinal and when it contracts it propels food forward. We call this peristalsis. The second layer is circular. When it contracts it swishes food back and forth within a compartment. We call this segmentation.

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20
Q

Describe the serosa.

A

This is also the visceral peritoneum. It is a very thin layer of areolar C.T. with one layer of simple squamous epithelium.

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21
Q

What is the splanchnic circulation?

A

Circulation of the digestive tract (GI tract). These vessels branch off of the aorta and serve the spleen, liver, stomach, pancreas, small and large intestines.

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22
Q

What’s the enteric nervous system?

A

Nerve supply to the GI tract.

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23
Q

Where is the submucosal nerve plexus? Myenteric?

A

This is part of the enteric system that is in the submucosa. The myenteric nerve plexus is found between the circular and longitudinal muscle layers in the muscularis.

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24
Q

Describe the anatomy of the mouth. What main function occurs here?

A

The cavity is called the oral cavity. The palate is the roof of the mouth. The hard palate is anterior and is made up of the palatine processes of the maxilla anteriorly and the two palatine bones posteriorly. The rigid surface is used by the tongue to mash food into smaller pieces and the corrugated texture provides friction to break food apart. The soft palate is posterior and is made up of mostly skeletal muscle.

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25
Q

Describe the anatomy of the palate and how it contributes to mastication of food in the mouth.

A

helps masks foods and turn then into a bolus.

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26
Q

What are the main functions of the tongue?

A

To break food into smaller pieces, mix it with saliva, which contains enzymes, and form a bolus to swallow..

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27
Q

What are the three different types of papilla found on the tongue? Function of each?

A

Filiform papillae roughen the tongue to increase friction for food. Fungiform papillae are scattered over the tongue and have taste buds on them. Vallate papillae are in the back of the tongue and foliate papillae are on the lateral sides of the tongue.

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28
Q

What’s a bolus?

A

A ball of food that is swallowed.

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29
Q

What are the functions of saliva?

A

Cleanse the mouth, dissolve food chemicals so that they can be tasted, moisten food to help create a bolus out of it, and contains 2 enzymes that begin to break down food: linguinal lipase (breaks down lipids) and salivary amylase (breaks down carbs).

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30
Q

What are the three main salivary glands and where are they?

A

They are outside the oral cavity and empty saliva into the mouth. THey include the parotid gland, submandibular gland and sublingual gland.

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31
Q

What do the serous cells of the salivary glands secrete? Mucus glands?

A

Serous cells secrete lysozyme, ions and some mucin. Mucus glands secrete mucus.

32
Q

What does saliva consist of?

A

Mostly water and electrolytes. It also contains digestive enzymes mentioned above (#23), proteins (mucin, lysozyme, defensins, and IgA), and some metabolic wastes.

33
Q

Describe nervous system control of salivation.

A

Salivation is controlled by the parasympathetic nervous system. Chemoreceptors and mechanoreceptors in the mouth signal the salivatory nuclei in the brain stem (the pons and the medulla oblongata). Parasympathetic activity increases and innervates the salivary glands.

34
Q

What two parts of the pharynx does food pass through? What structures in this passageway reflect its function?

A

The oropharynx and the laryngopharynx. The nasopharynx only passes air and is higher than the back of the mouth, so no food moves through this part. The epithelium is stratified squamous in the oro and laryngopharynx. There are two layers of skeletal muscle. Contraction moves food through the tube.

35
Q

Describe the anatomy of the esophagus. Include laryngopharynx, epiglottis, esophageal hiatus, cardinal orifice, cardiac sphincter.

A

Food moves through the laryngopharynx and the epiglottis flaps closed over the larynx, so no food can enter the trachea (airway). The esophagus goes through the diaphragm at the esophageal hiatus and enters the abdomen. It enters the stomach at the cardial orifice. The cardiac sphincter is the sphincter connecting the esophagus and the stomach. When the circular layer of muscle that composes this sphincter contracts, no food is allowed through.

36
Q

Describe the four layers of the esophagus: mucosa, submucosa, muscularis and serosa.

A

Mucosa is stratified squamous epithelium, for protection from friction of the food moving through it. The sub-mucosa is areolar C.T. with esophageal glands. As a bolus of food moves through the esophagus, it presses these glands which causes them to release mucus.

37
Q

What is chyme? Where is it made?

A

The stomach takes the bolus of food that enters and it uses very powerful muscular contractions of both muscle layers to mash this food until it is liquid. This liquid is called chyme.

38
Q

Gross anatomy of the stomach: what are rugae, cardia, fundus, body, pyloric antrum, pyloric canal, pylorus, pyloric sphincter or valve, the greater curvature, the lesser curvature, greater and lesser omentum. Find these structures on a diagram.

A

Done

39
Q

Rugae

A

are folds of the stomach. When the stomach fills, these rugae stretch out, allowing the organ to expand without there being a lot of pressure on the organ wall.

40
Q

Describe the anatomy of the muscularis in the stomach. What’s the function of this layer of tissue here?

A

There are two layers of smooth muscle here. The inner layer is circular and the outer layer is longitudinal. The circular layer is for segmentation and the longitudinal layer is for peristalsis.

41
Q

What are gastric pits/glands? Describe their structure and function.

A

The stomach is dotted, to the naked eye, with millions of these little pits. Each of them leads to 3-5 gastric glands. Inside a gastric gland are several different types of cells that contribute to digestion of food.
35. Describe each type of glandular cell function: neck cells, parietal cells, chief cells, and enteroendrocrine cells. Neck cells secrete mucus. Parietal cells secrete HCl and intrinsic factor. HCl helps decrease the pH of the stomach to about 2. In these kinds of conditions, pepsin, the enzyme that breaks down protein in the stomach, can function best. intrinsic factor is required for the absorption of B12 in the small intestine. B12 binds to intrinsic factor and then that complex binds to receptors on the epithelial cells that line the small intestine and from there they are absorbed. Chief cells secrete pepsinogen and lipases. pepsinogen is the inactive form of pepsin. It is activated by HCl and pepsin itself. Lipases start to break down fats, but only account for about 15% of fat digestion that takes place in the GI tract (most occurs in the small intestine). Last, enteroendocrine cells release chemical messengers into the interstitial fluid of the lamina propria. These include hormones like histamine (when an inflammatory response is occuring), serotonin, gastrin, and so forth.

42
Q

What are three factors that protect the stomach lining from the acidic environment of the stomach?

A

The stomach protects itself using the ‘mucosal barrier’. The pH of the stomach is about 2.0. That is low enough to kill the cells that line it, so those cells are protected by this barrier. The barriers has a thick coat of bicarbonate-rich mucus. The third factor is that the cells are joined together using tight-junctions, so nothing can slide between them. So, bicarbonate has the ability to bind with H+ to form water, neutralizing the H+ and increasing pH. So, if any H+ does sink deep enough into the mucus, bicarbonate buffers it. The mucus is a very thick barrier which protects the cells. Last, the tight junctions also act as a barrier.

43
Q

What are the four main activities/functions the stomach is involved in?

A

Propulsion (peristalsis occurs here). Mechanical breakdown occurs here when the food bolus is crushed by peristaltic waves. This breaks the bolus down into chyme/liquid. Digestion occurs in the stomach to some extent. Protein digestion begins with pepsin. Salivary amylase continues to work on carbs until it is denatured by the low stomach pH. Linguinal lipase continues to work on lipids until it is denatured and gastric lipases continue to work on those lipids.

44
Q

Identify the right, left, quadrate and caudate lobes of the liver, the falciform ligament, gall bladder, right and left hepatic ducts, common hepatic duct, systic duct, bile duct on a diagram.

A

Done

45
Q

Describe what a liver lobule and hepatocytes are.

A

A hepatocyte is a cell of the liver. The liver is composed of lobules and the lobules are composed of hepatocytes.

46
Q

What are the three structures of the portal triad and where would you find a triad?

A

The portal triads are found at the six corners of each lobule of the liver. They are composed of a branch of the hepatic artery, which brings blood to the hepatocytes, a branch of the hepatic portal vein, which comes from the small intestine and brings nutrients from digestion to the liver, and a bile duct, which is collecting bile from the hepatocytes of the lobule. So, the hepatic portal and hepatic artery are bringing blood to the lobule and the bile duct is draining bile away from the cells.

47
Q

What is a liver sinusoid and what is its function?

A

Blood from the hepatic portal vein and hepatic artery moves through the sinusoids and empties into the central vein. Sinusoids are vessels, but they have a bigger volume and lower pressure. They are collecting areas for blood.

48
Q

What’s the function of stellate macrophages? Where would you find these cells?

A

They exist in the walls of the sinusoids and their job is to remove debris like worn out red blood cells, bacteria, and so forth. They are an immune system cell.

49
Q

What are the functions of hepatocytes (the liver)?

A

Hepatocytes make about 900 mls of bile per day, store glucose as glycogen, use amino acids to make proteins (the liver makes all 20 blood plasma proteins), store fat-soluble vitamins, and detoxify things coming from the digestive tract.

50
Q

What are bile canaliculi?

A

They are tiny vessels that run between adjacent hepatocytes collecting bile that has been made in the cells. They take the bile and drain it into the bile duct of the portal triad.

51
Q

What cells make bile? What is it made out of? What is bilirubin? Where does it come from? What happens to it in the small intestine? What is stercobilin?

A

Hepatocytes make bile. Bile consists of bile salts (these are the ‘things’ that emulsify lipids in the small intestine so that fat digestion is efficient), bile pigments (bilirubin), cholesterol, triglycerides, phospholipids, and electrolytes. Bilirubin is a pigment in bile. Bilirubin is the yellow waste product from the breakdown of red blood cells. It is absorbed by the liver cells from the blood and moved into bile. It is converted into stercobolin in the small intestine. Stercobolin gives feces its brown color.

52
Q

What’s the function of the gall bladder? Describe its anatomy.

A

The gall bladder stores bile made by the hepatocytes. It is a thin, muscular sac. It looks green when filled with bile.

53
Q

What’s the function of acini cells in the pancreas?

A

They secrete digestive enzymes.

54
Q

The ducts of the pancreas secrete two things that are important to the secretions of the acini cells. What are they?

A

Water, to dilute the enzymes and bicarbonate, to neutralize the highly acidic chyme that is coming in from the stomach.

55
Q

What else does the pancreas secrete?

A

Insulin and glucagon.

56
Q

What is pancreatic juice composed of?

A

Water, bicarbonate and digestive enzymes.

57
Q

Why is the bicarbonate in the pancreatic secretions important?

A

Water, to dilute the enzymes and bicarbonate, to neutralize the highly acidic chyme that is coming in from the stomach.

58
Q

What are the four types of pancreatic enzymes? What are they targeting?

A

Proteases target proteins, breaking them down into single amino acids or short chains of amino acids. Amylases break down carbohydrates. Lipases break down fats and Nucleases break down nucleic acids.

59
Q

What is the hepatopancratic ampulla and where would you find it?

A

It is the sphincter that closes the duct that contains bile and pancreatic juices. It connects this duct with the small intestine at the beginning of the small intestine.

60
Q

Describe the gross anatomy of the small intestine.

A

The small intestine is about 20 feel long. It begins at the pyloric sphincter, which is the sphincter between the stomach and small intestine. It is divided into three parts: the duodenum, which is retroperitoneal, the jejunum and the ileum. The ileocecal valve/sphincter is the sphincter between the small and large intestine.

61
Q

What are the three adaptations of the small intestine that increase surface area?

A

Circular folds, villi and microvilli. Circular folds are big undulations of the mucosa and submucosa of the small intestine. Villi are undulations or often called finger like projections of the simple columnar epithelial tissue (the mucosa) lining the organ and microvilli are extensions of the plasma membrane that create what we call the brush border on these cells.

62
Q

What are the 5 types of cells in the epithelium of the small intestine and what is their function?

A

Enterocytes make up the bulk of the cells. These are the simple columnar epithelial cells that absorb nutrients from the small intestine. Goblet cells secrete mucus. Enteroendocrine cells (just like in the stomach) secrete hormones that increase gastric secretions in the stomach, Paneth cells are immune system cells that release defensins and lysozyme. Both of these destroy bacteria. Stem cells divide to produce these other four types of cells.

63
Q

What are Peyer’s patches? Where do you find them?

A

Peyer’s Patches are MALT tissues. They are collection of lymphoid follicles found in the submucosa of the terminal/distal end of the small intestine. Their function is to find and destroy bacteria that might have entered with the food you have eaten.

64
Q

What are three places that enzymes for digestion are made?

A

Saliva, gastric pits, pancreas.

65
Q

Describe segmentation and peristalsis. What is the main function of each?

A

Segmentation squeezes the contents of the small intestine with the circular muscle layer of the muscularis. This is kind of like taking a toothpaste tube and squishing it back and forth by grabbing it on both ends and squeezing one hand at a time. This swishes the abdominal contents back and forth over the cells lining the small intestine, giving those cells ample opportunity to absorb the nutrients contained there. Peristalsis is created by the longitudinal layer of smooth muscle in the muscularis. The result of this muscle contracting is propulsion of food through the system.

66
Q

Define the term digestion:

A

breaking down food into its building blocks (monomers).

67
Q

What are the monomers for each of the 4 different organic molecules?

A

Monosaccharides for carbohydrates, amino acids for proteins, glycerol and fatty acids for lipids and nucleotides for nucleic acids.

68
Q

Describe the digestion and absorption of proteins.

A

Nothing happens in the mouth. Pepsinogen is activated to pepsin in the stomach. Pepsin is the first enzyme that begins the process of breaking proteins down. Pancreatic proteases break proteins down in the small intestine. They break them down into single amino acids and/or small chains of amino acids. Finally, brush border enzymes (enzymes secreted by the enterocytes brush border) complete the digestion into single amino acids. Single amino acids are then absorbed.

69
Q

Describe the digestion of carbohydrates.

A

Salivary amylase begins carbohydrate digestion in the mouth. This enzyme continues to work in the stomach for a short while, until it is denatured by the low pH of the stomach. No additional enzymes are added in the stomach. Pancreatic amylase continues the digestion into mono and disaccharides. Brush border enzymes complete the digestion into monosaccharides.

70
Q

Describe the digestion of nucleic acids.

A

There is no digestion until the small intestine. Pancreatic nucleases break these down into nucleotide monomers (nucleic acids). Brush border enzymes digest the nucleic acids into their pieces (bases, phosphates and ribose, a sugar). These are then transported across the membrane.

71
Q

Describe the digestion of lipids.

A

Linguinal lipase begins the breakdown of lipids in the mouth. It continues to work in the stomach until it is denatured by the low pH of the stomach. No further digestion of lipids occurs in the stomach. Pancreatic lipases are the enzymes that break lipids down. Bile salts help this process by emulsifying the fat globules (breaking them up into smaller pieces so that there is more surface area for the enzymes to work on the fats). Without this help, fats wouldn’t have long enough in the small intestine to be completely broken down and we wouldn’t be able to absorb enough. Micelle formation: fatty acids and monoglycerides organize themselves with bile salts to form a micelle. Micelles take the fatty acids to the surface of the enterocytes. These then diffuse across the enterocyte membrane. The smooth ER of the enterocyte converts the fatty acids back into a triglyceride. They combine with phospholipids and cholesterol and are surrounded by a layer of proteins. The chylomicron is exported out of the enterocyte by exocytosis. These enter lacteals, which are part of the lymphatic system. From there, these are carried in the blood.

72
Q

What are the functions of the large intestine?

A

To absorb any remaining water, eliminate waste and absorb products of the bacterial action. Bacteria in the large intestine ferment any carbohydrate that wasn’t fully digested in the small intestine.

73
Q

Describe the gross anatomy of the colon. Include the terms cecum, appendix, ascending colon, right colic flexure, transverse colon, left colic flexure, descending colon, sigmoid colon, rectum, anal canal, anus, internal anal sphincter and external anal sphincter. Identify these structures on a diagram.

A

Done

74
Q

Contrast the small and large intestinal mucosa layers.

A

The small intestines mucosa is simple columnar epithelium and so is the large intestines’. However, in the small intestine there are circular folds, villi and microvilli to increase the surface area for absorption. The large intestine looks flat across the top, no undulations. Also, there are a lot of mucus glands in the colon, so the mucus lubricates the elimination of waste.

75
Q

What are the benefits of the bacteria in our large intestine?

A

They ferment indigestible carbohydrates (fiber). They get energy. They produce short chained carbs, which are absorbed and used for energy. They also make vitamin K and many different B vitamins.

76
Q

How do fat soluble vitamins become absorbed? Water soluble?

A

Fat soluble vitamins dissolve in fats and then when the fats are absorbed, the vitamins are absorbed. Water soluble vitamins (B and C) are absorbed using active or passive transport. B12 is the exception. B12 binds to intrinsic factor and then that complex is absorbed.