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BIOL1203 > UNIT 6 - DIGESTIVE SYSTEM > Flashcards

UNIT 6 - DIGESTIVE SYSTEM Flashcards

1
Q

1Digestive system

A

Consists of the gastrointestinal tract and accessory organs or digestion and involves breakdown of food

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2
Q

Functions of digestive system (4)

A
  • Takes in food
  • Breaks food down into nutrient molecules
  • Absorbs molecules into bloodstream
  • Get rid of any indigestible remains
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3
Q

Ingestion

A

Eating, or taking in food into the digestive tract

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4
Q

Digestion

A

Process by which insoluble food consisting of large molecules is broken down into soluble compounds

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5
Q

Mechanical digestion

A

Chewing of food into smaller pieces involving smooth muscle layers, teeth, tongue

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6
Q

Chemical digestion

A

Enzymes and acids breaking down the food involving pepsinogen, pepsin, HCl, gastric lipase

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7
Q

Absorption

A

Passage of food molecules from the digestive tract into circulatory/lymphatic system for transport to body cells

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8
Q

Defecation

A

Elimination or passing of feces from rectus out the body

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9
Q

Extracellular digestion

A

Food is broken down OUTSIDE the cell by enzymes produced by digestive tract cells

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10
Q

Intracellular digestion

A

Food is broken down INSIDE a cell (eg. Bacteria phagocytosed by WBC and digested by enzymes with lysosomes)

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11
Q

2 compartments of organs of digestive system:

A
  • Alimentary canal (gastrointestinal)
  • Accessory organs
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12
Q

Alimentary canal

A

Continuous muscular rube that runs from the mouth to the anus, consisting of mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus. Functions in digesting food and absorbing fragments through lining into blood

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13
Q

Accessory organs

A

Organs that aid in process of digestion consisting of teeth, tongue, gallbladder and digestive glands such as salivary gland, liver, pancreas

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14
Q

Digestive glands

A

Produce secretions that break down food

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15
Q

Mouth

A

Where food is chewed and mixed with enzyme containing saliva that begins process od digestion and where swallowing is initiated (eg. Mouth, tongue, salivary gland, teeth)

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16
Q

Tongue

A

Mixes food with saliva for easy swallowing

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17
Q

Buccal cavity

A

AKA oral cavity consisting of lips, cheeks, palate, tongue lined with stratified squamous epithelium

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18
Q

Uvula

A

Hanging from middle of posterior edge of soft palate

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19
Q

Soft palate

A

Behind hard palate separating nasal passage from food passage

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20
Q

Hard palate

A

Tissue covering part of maxilla in the anterior roof of mouth

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21
Q

Mastication

A

Chewing of food to make smaller food particles

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22
Q

Bolus

A

Small rounded mass of chewed food at moment of swallowing

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23
Q

Saliva

A

Clear liquid made by several glands in mouth and made up of 99.5% water and 0.5% solutes including salt, gases, bacteriostatic lysozyme and salivary amylase

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24
Q

Major salivary glands (3):

A
  • Parotid
  • Submandibular
  • Sublingual
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25
Q

Saliva functions (4)

A
  • Cleanse mouth
  • Dissolve food chemicals to be tasted
  • Moisten food and make bolus
  • Contain enzyme amylase that begins digestion with starch
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26
Q

Pharynx and esophagus

A

Conduits to pass food from mouth to stomach and have a major function in propulsion that starts with deglutition

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27
Q

Deglutition

A

Swallowing and involves coordination of 22 muscle groups and 3 phases

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28
Q

3 phases of deglutition (swallowing) (3)

A
  • Buccal phase (voluntary)
  • 2 pharyngeal esophageal phases (involuntary)
  • Controlled by swallowing center in medulla and lower pons
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29
Q

Buccal phase (voluntary)

A

Upper esophageal sphincter is closed, tongue moves upward and backwards against palate and pushes bolus to back of oral cavity into oropharynx

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30
Q

Pharyngeal esophageal phase (involuntary) 1

A

Uvula and soft palate move upward and close off nasopharynx, and larynx rises to epiglottis and blocks trachea. Upper esophageal sphincter relaxes and food enters esophagus

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31
Q

Pharyngeal esophageal phase (involuntary) 2:

A

Constrictor muscles of esophagus contract and force food inferiorly, upper esophageal sphincter closes

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32
Q

Esophagus

A

Muscular collapsible tube extending from pharynx to stomach located behind trachea and in front of vertebral column. It runs through neck, diaphragm and connects to stomach

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33
Q

Esophageal sphincter

A

Point where the esophagus connects to stomach

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34
Q

Peristalsis

A

Rhythmic muscular movements of alternating contractions of circular and longitudinal muscles that pushes food down esophagus towards stomach. Food is moved distally along tract

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35
Q

Circular muscle contractions

A

Lumen (internal diameter of digestive tract) contracts

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36
Q

Longitudinal muscle contraction

A

Length of digestive tract decreases and lumen widens

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37
Q

Stomach

A

Muscular J shaped organ in upper part of abdomen below diaphragm consisting of 4 major parts. Functions in digesting proteins and lipids (very small amounts of digestion)

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38
Q

4 major parts of stomach:

A
  • Cardia
  • Fundus (left)
  • Body
  • Pylorus (right)
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39
Q

Cardia

A

Lower portion where the esophagus is joined

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40
Q

Fundus

A

Rounded part of stomach above and left to cardia

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41
Q

Body

A

Largest central portion of stomach

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42
Q

Pylorus

A

Lower part of stomach attached to first part of small intestine (duodenum)

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43
Q

Pyloric sphincter

A

Band of circular muscle that can open or close and control movement of food from stomach into duodenum

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44
Q

Gastrin

A

Hormone produced by stomach that stimulates release of gastric juice (hydrochloric acid)

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45
Q

Gastric juice

A

Converts bolus to acid chyme with a pH of 2

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46
Q

Cells of gastric gland (5)

A
  • Surface mucous cell
  • Mucous neck cell
  • Parietal cell
  • Chief cell
  • G cell
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47
Q

Surface mucous cell

A

Secretes mucus

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48
Q

Mucous neck cell

A

Secretes mucus

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49
Q

Parietal cell

A

Secretes hydrochloric acid and intrinsic factor

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50
Q

Chief cell

A

Secretes pepsinogen and gastric lipase

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51
Q

G cell

A

Secretes hormone gastrin

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52
Q

Liver

A

Largest gland in body weighing 3 pounds and consists of 4 primary lobes

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53
Q

4 lobes of liver:

A
  • Right
  • Left
  • Caudate
  • Quadrate
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54
Q

Falciform ligament

A

Separates larger right and smaller left lobe of liver

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55
Q

Round ligament (ligamentum teres)

A

Rope like band of connective tissue of fetal umbillical vein along falciform ligament

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56
Q

Liver functions (9):

A
  • Produce bile salts from cholesterol for lipid emulsification
  • Fat/cholesterol absorption
  • Regulate blood glucose by producing and storing glycogen
  • Detoxifies poisonous substances
  • Produce plasma protein
  • Stores fat soluble vitamins ADKE
  • Storage for elements (Cu, Fe)
  • Fatty acids converted to storage forms
  • Degradation of hormones
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57
Q

Bile

A

Consists of bile salts, phospholipids, cholesterol, electrolytes and water used to break down fats during digestion and is produced by liver and is stored/concentrated in gallbladder

58
Q

Left and right hepatic duct

A

Made up of several small bile ducts in the right lobe of liver that join

59
Q

Common hepatic duct

A

Made up of the left hepatic duct joining with the right hepatic duct

60
Q

Common bile duct

A

Made up of the common hepatic duct joining with the cystic duct (duct from gallbladder)

61
Q

Ampulla of Vater

A

Made up of the common bile duct joining with the pancreatic duct that projects slightly into the duodenum

62
Q

Hepatic portal vein

A

Unions of veins of stomach, small intestine and large intestine that take blood to the liver. The liver does receive some arterial blood through hepatic artery but majority is from hepatic portal vein

63
Q

What happens to hepatic portal vein and artery in the liver

A

Both hepatic artery and hepatic portal vein break up into blood capillaries and release blood that mix together. The blood gets drained later on into two hepatic veins and enters inferior vena cava

64
Q

Hepatic portal system significance

A

Allows modification of nutrients absorbed from the digestive tract by the liver cells (eg. Level of blood glucose). The liver removes toxins from the blood and adds plasma proteins and therefore the liver modifies, stores, and controls various nutrients in the blood and detoxifies blood before entering circulatory system

65
Q

Pancreas

A

Soft gland about 12-15cm long and 2.5cm wide located below the curvature of stomach divided into three parts

66
Q

3 parts of pancreas:

A
  • Head
  • Body
  • Tail
67
Q

Exocrine functions of pancreas

A

Production of pancreatic juice (enzyme for digestion of fats, proteins, carbohydrates, nucleic acids)

68
Q

Bicarbonate ion:

A

Neutralizes acid chyme coming from the stomach and provides a basic pH for the enzyme to function

69
Q

Endocrine functions of pancreas

A

Produces insulin to lower blood sugar and glucagon to raise blood sugar via islets of langerhans

70
Q

Small intestine

A

Longest section of the alimental canal (3m), forms the pyloric sphincter to caecum and is made up of 3 parts. Functions in mechanical (segmentation) and chemical digestion of food, and absorption of water, digestion, vitamins, salts, and monosaccharides

71
Q

3 parts of small intestine:

A
  • Duodenum (25cm)
  • Jejunum (1m empty)
  • Ileum (2m twisted)
72
Q

Circular folds

A

Permanent folds on the lining of the small intestine (1cm deep) that force chyme to slowly spiral through lumen and allow more time for nutrient absorption

73
Q

Villi

A

Fingerlike projections of mucosa (1mm high) in small intestine with a core that contains dense capillary bed and lymphatic capillary called a lacteal for absorption

74
Q

Microvilli

A

Cytoplasmic extensions of mucosal cell that gives fuzzy appearance called brush border that contains membrane bound enzymes (brush border enzymes) used for final carbohydrate and protein digestion

75
Q

Segmentation

A

Most common motion of small intestine (mix/moves contents toward ileocecal valve) after a meal

76
Q

Peristalsis vs segmentation:

A
  • Peristalsis: Adjacent segment of alimentary canal organs alternately contract and relax. Food is moved distally along tract and some mixing may occur but primarily propulsive
  • Segmentation: Nonadjacent segment of alimentary canal organs contract and relax. Food is moved forward, then backward. Mixing of food occurs and breaks it down mechanically with some propulsion
77
Q

Large intestine

A

About 1.3m x 6.5cm and consists of 4 main parts. Although most of water absorption occurs in small intestine, it functions in absorption of water, minerals, vitamins. Synthesis of vitamins K and B5 by resident bacteria, production of feces/defecation and chemical digestion of food

78
Q

4 parts of large intestine:

A
  • Caecum (appendix)
  • Colon (main part, 4 divisions)
  • Rectum
  • Anal canal
79
Q

Feces

A

Undigested material composed of bacteria, water, hemoglobin breakdown products

80
Q

Anal canal

A

Last segment of large intestine that opens to body exterior at anus consisting of two sphincters

81
Q

2 sphincters of anus:

A
  • Internal anal sphincter: smooth muscle
  • External anal sphincter: skeletal muscle (voluntary control)
82
Q

Regulation of defecation (5)

A
  • Feces moving to rectum cause distension of rectal walls and stimulate pressure receptors on wall
  • Signal sent to bottom portion of spinal cord (sacral)
  • Impulse sent back to rectum and stimulate contraction of longitudinal muscles on rectal walls
  • Pressure on internal anal sphincter relaxes and opens
  • If external sphincter is relaxes, defecation occurs. If constricted, defecation is delayed
83
Q

Abdominal muscle function in defecation

A

Voluntary contractions of abdominal muscles help defecation by putting pressure on rectum

84
Q

6 essential nutritional factors:

A
  • Carbohydrates
  • Fats
  • Proteins
  • Water
  • Vitamins
  • Minerals
85
Q

Digestion of carbohydrates

A

Begins in the mouth

86
Q

What is starch broken down into

A

Glucose

87
Q

Salivary amylase

A

Initiates hydrolysis of starches (carbohydrate) in the mouth and breaks them into maltose (disaccharide of two glucose molecules). Sometimes there is not enough time so it only breaks them into shorter chains of starch

88
Q

Pancreatic amylase

A

Further digestion of carbohydrates breaking down starch into maltose in lumen of small intestine

89
Q

Maltase

A

Breaks down maltose to glucose

90
Q

Sucrase

A

Digests sucrose

91
Q

Lactase

A

Digests lactose

92
Q

Brush border

A

Cells lining small intestine

93
Q

Where does the absorption of monosaccharides occur

A

Small intestine

94
Q

Process of monosaccharide absorption (4)

A
  • Pancreatic amylase breaks down starch and glycogen into oligosaccharides/disaccharide
  • Brush border enzymes break oligosaccharides/dissacharides into monossachride- Monosaccharides transported across apical membrane of absorptive epithelial cell via active transport and Na+ K+ pump in basolateral membrane
  • Monosaccharides exit across basolateral membrane by facilitated diffusion and enter capillary via intracellular cleft
95
Q

How do monosaccharides get absorbed in epithelial cells

A

Glucose and galactose get transported by active cotransport with sodium ions, and fructose by facilitated diffusion

96
Q

How do monosaccharides get absorbed in blood

A

Facilitated diffusion

97
Q

What are proteins broken down into

A

Amino acids

98
Q

Digestion of proteins

A

Begins in the stomach

99
Q

Gastric juice

A

Composed of mucous, HCl, pepsinogen (inactive form of enzyme) formed within the stomach lining and secreted

100
Q

Pepsin

A

Stomach enzyme originating from pepsinogen, activated by HCl and secreted by the stomach. Functions in breaking down proteins into polypeptides and works well in very acidic pH

101
Q

Trypsin

A

Secreted in inactive form by the pancreas into duodenum and gets activated by enzyme in small intestinal wall and then activates others. Functions in digesting polypeptides into smaller peptide units

102
Q

Chymotrypsin

A

Secreted by the pancreas into duodenum and digests peptides into amino acids

103
Q

What happens to pepsin after digestion

A

It becomes inactive when the acidic environment of the stomach is neutralized in the small intestine and other enzymes like trypsin and chymotrypsin help with protein digestion

104
Q

Carboxypeptidase

A

Secreted by pancreas into duodenum and cuts off one amino acid from the COOH end

105
Q

Aminopeptidase

A

Secreted by brush border and cuts off one amino acid at amino end

106
Q

Dipeptidase

A

Splits dipeptides

107
Q

Endopeptidases

A

Cut peptide bonds within the protein molecule other than the ones at each end of protein molecule (eg. pepsin, trypsin, chymotrypsin)

108
Q

Exopeptidases

A

Cut peptide bonds at the ends of the protein molecule (eg. Carboxypeptidase, aminopeptidase)

109
Q

Process of protein absorption (4):

A
  • Pancreas proteases break down proteins into smaller pieces and some amino acids
  • Brush border enzymes break protein fragments into amino acids
  • Amino acids cotransported across apical membrane of absorptive epithelial cells via Na+ K+ pump in basolateral membrane
  • Amino acid exit across basolateral membrane via facilitated diffusion and enter capillary via intracellular cleft
110
Q

How do proteins get absorbed into epithelial cells

A

By active cotransport of amino acids with sodium

111
Q

How do proteins get absorbed into blood

A

By facilitated diffusion

112
Q

What are fats broken down into

A

Fatty acids and glycerol

113
Q

Digestion of lipids

A

Begins in the stomach

114
Q

Lingual lipase

A

Enzyme for digesting triglycerides within stomach to 1 fa and diglyceride activated by HCl when bolus reaches stomach

115
Q

Gastric lipase

A

Enzyme for digesting triglycerides within the stomach into 2 fa and 1 monoglyceride)

116
Q

Pancreatic lipase

A

Enzyme for breaking down triglycerides to 2 fa and monoglycerides

117
Q

Where do most lipid digestion occur

A

Small intestine

118
Q

Is lipase soluble in fat

A

NO so it can only act on the surface of fat globule

119
Q

Bile salts

A

Molecules polar at one end and nonpolar at other (similar to phospholipid) and functions to emulsify fats by breaking large globules of fat into smaller ones and preventing fat from forming a mass into larger droplets

120
Q

Emulsification

A

Process in which fat globules must be broken into tiny droplets for lipase to work

121
Q

Process of fat digestion in small intestine (6):

A
  • Lipase is not soluble in fat so it can only act at surface of fat globule
  • Bile emulsifies fat globule and break down into smaller droplets and increasing surface area and action of pancreatic lipase
  • Pancreatic lipase hydrolyzes triglycerides into 2 fa and monoglycerides
  • If the digested fa are short chains (less than 10-12 Carbon), they are soluble in water and can move easily to intestinal epithelial cells
  • If fa is long chains, they are not soluble in water so bile salts must interact with them to produce small droplets called micelles
  • Micelles diffuse over intestinal wall and the digested fat diffuses across intestinal wall leaving bile salts behind
122
Q

Short fa chains (digestion of fat)

A

Soluble in water and can easily move to intestinal epithelial cells and diffuse into them

123
Q

Long fa chains (digestion of fat)

A

Not soluble in water and must interact wih bile salts to produce small droplets

124
Q

Micelles

A

Small droplets of digested fat

125
Q

Absorption of lipids (3)

A
  • Short fatty acids absorbed through the cell into blood capillaries in villus
  • Monoglycerides and long fatty acids diffuse into villus epithelium with help of bile salts
  • Inside epithelia, the fa and MG are reassembled into triglycerides and travel through blood via chylomicrons
126
Q

Chylomicrons

A

Mixtures of triglycerides and cholesterol with a phospholipid and a protein coat to travel through blood for absorption

127
Q

How do chylomicrons leave the epithelial cell

A

Exocytosis to lacteals, then lymph, then left subclavian vein, then the general systemic circulation

128
Q

Nucleic acids

A

Found in cells of all plants and animals and are components of most vegetables and meats

129
Q

Ribonuclease

A

Pancreatic enzyme that digests RNA into nucleotides

130
Q

Deoxyribonuclease

A

Pancreatic enzyme that digests DNA into nucleotides

131
Q

Intestinal enzymes of nucleotides

A

Digest nucleotides into pentose sugars, phosphate, nitrogenous base

132
Q

Mechanism of control of digestion

A

Secretion of digestive juices in humans is under nervous and hormonal control

133
Q

Nervous control secretions

A

Short lived

134
Q

Hormonal regulation secretion

A

More sustained

135
Q

3 phases that regulate secretion of digestive juices:

A
  • Cephalic phase of digestion (neural)
  • Gastric phase of digestion (neural & hormonal)
  • Intestinal phase of digestion (neural & hormonal)
136
Q

Cephalic phase of digestion

A

Smell, taste, sight or thought of food stimulates cerebral cortex, hypothalamus and brain stem. Nervous impulses travel via vagus nerve to stomach and stimulate secretion of gastric juice (only neural regulation, no hormonal regulation)

137
Q

Gastric phase of digestion (neural)

A

Stretch and chemoreceptors in stomach activated as stomach distends and pH increases due to presence of proteins. Signals are sent by stretch and chemoreceptors to nerves within stomach wall that release HCl and greater stomach mobility

138
Q

Gastric phase of digestion (hormonal)

A

Regulated by hormone gastrin produced by gastric glands and stimulated by stomach distension, partially digested protein, increased pH above 2, caffeine

139
Q

Intestinal phase of digestion (neural)

A

Enterogastric reflex caused by distension of duodenum due to entry of stomach contents cause stretch receptors to send impulses to medulla to decrease gastric emptying which ensures acid chyme is not delivered to small intestine faster than it can be processed

140
Q

Intestinal phase of digestion (hormonal)

A

Secretin and cholecystokinin hormones contribute to regulation of secretive digestive juices here

141
Q

Secretin

A

Produced by endocrine glands in intestinal wall stimulate by acid chyme entering duodenum. Travels through the blood stream to pancreas and stimulates flow of pancreatic juice containing bicarbonate ion, decreasing acidity of chyme

142
Q

Cholecystokinin

A

Stimulated by amino acids/fatty acids in duodenum and travels through bloodstream to pancreas, then gallbladder to stimulate the secretion of pancreatic juice containing enzymes and bile to emulsify fats

BIOL1203 (12 decks)

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