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Biolology > Chapter 49 Digestive System > Flashcards

Chapter 49 Digestive System Flashcards

1
Q

What are the four steps of the GI tract?

A

1) Ingestion
2) Digestion
3) Absorption
4) Elimination

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2
Q

What is ingestion?

A

Food is taken in through the mouth and swallowed to move through the GI tract

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3
Q

What is digestion and what are the types?

A

Digestion is the breakdown of complex biomolecules into smaller ones
a) Mechanical Digestion: broken down by teeth
b) Chemical Digestion: broken down my enzymes and biomolecules (bile)

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4
Q

What is absorption?

A

Food particles become small enough and are absorbed by epithelial cells

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5
Q

What is elimination?

A

indigestible parts are removed and needed substances are reabsorbed (water and bile acids)

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6
Q

What is the progression of the digestive system?

A

1) Mouth
2) Pharynx
3) Esophagus
4) Stomach
5) Small Intestine
6) Large Intestine
7) Rectum
8) Anus

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7
Q

What are the accessory organs of the digestive system?

A

1) Salivary glands
2) Liver
3) Gallbladder
4) Pancreas
5) Appendix

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8
Q

What does concentric mean?
What are the four concentric layers that line the gut (lumen)?

A

Wrapped around one another
1) Mucosa
2) Submucosa
3) Muscularis
4) Peritoneum

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9
Q

What is the function of the mucosa and where is it located?

A
  • innermost epithelial cell layer
  • secretes digestive enzymes and hormones for digestion
  • secretes mucus to protect the gut
  • absorbs digested particles
  • Villi/Microvilli increase surface area and help with absorption
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10
Q

What is the function of the submucosa?

A
  • supports overlying epithelium
  • contains blood vessels that supply GI tract with oxygen and nutrients
  • transports nutrients to rest of body
  • has nervous tissue with sensory and secretory functions
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11
Q

What is the function of the muscularis?

A
  • made up of smooth muscle arranged circularly or longitudinally
  • contraction moves food (via peristalsis)
  • muscular sphincters can stop food
  • nervous tissue helps control contractions (acts independent of CNS)
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12
Q

What is the function of the peritoneum and where is it located?

A
  • outermost layer of epithelial cell and attaches the GI to the rest of the body
  • has epithelial tissue which secretes fluid to reduce friction of organs in the body cavity
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13
Q

What is the function of the enteric nervous system?

A
  • Nerve nets in submucosa and between smooth muscle make up the enteric nervous system
  • The nerves only form synapses with other nerves in the same enteric network.
  • Responsible for communication in the gut
  • CNS can influence this system, but it is autonomous
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14
Q

What is the structure of the mouth and two mechanisms for breakdown of food?

A

1) Mechanical Breakdown: food broken down via teeth
a) Incisors: used for cutting, chopping, or gnawing
b) Canines: for stabbing, gripping, ripping
c) Molars: shearing, crushing, grinding
*Tongue is a skeletal muscle
2) Chemical Breakdown: food broken down via saliva
- Salivary Amylase: starch/carbohydrates –> glucose
- Results in a clump of food called a bolus

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15
Q

What movements occurs in the pharynx?

A
  • Pharynx is the throat
  • Pharynx –> esophagus (via swallowing)
  • No digestion occurs here
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16
Q

What is the function of the epiglottis?

A
  • Epiglottis prevents food from going into the trachea (part of the pharynx)
  • The epiglottis is the covering for the glottis (opening of windpipe)
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17
Q

What is the function of the esophagus?

A
  • Muscular tube which food moves through to the stomach
  • Food is moved via peristaltic contractions
  • No digestion occurs here
18
Q

How does peristalsis work?

A
  • Waves of muscular contractions move food toward stomach
  • When food reaches the smooth muscle in esophagus, the esophagus contracts and pushes the food toward the stomach

**the upper esophagus is skeletal muscle; the rest is smooth muscle

19
Q

How does digestion in the stomach work and what are the parts in the stomach that facilitate it?

A
  • Esophagus empties food into the J-shaped stomach
  • Peristaltic waves push food through the stomach (churning/motility)
  • Sphincters (2 muscular rings) control movement into and out of the stomach
20
Q

What are the two sphincters in the stomach and their functions?

A

1) Lower Esophageal Sphincter: (esophagus and stomach)
- relaxes and stomach fills with food
- contracts when stomach is full (limits input)
2) Pyloric Sphincter: (stomach and small intestine)
- relaxes as stomach fills with food
- contracts as strong peristaltic waves move food through it
- only a limited amount can enter intestine at once (4 hours)

21
Q

What are the functions of the stomach?

A

1) Stores food
- stretches to accommodate food
2) Mixes food + acid = chyme
- Chyme is a semi-solid paste from bolus and gastric juices
3) Continues digestive processes
- Fat digestion begins here
- Carbohydrate and protein digestion continues here

**Only items absorbed in the stomach are alcohol, aspirin, and caffeine

22
Q

What are the three main gastric secretions of the stomach?

A

1) Hydrochloric Acid (HCl) from parietal cells
- hydrolyzes chemical bonds & activates pepsinogen
- pH around 1 (acidic) which kills microorganisms and denatures proteins and requires stomach lining to be replaced every 3 days
2) Pepsinogen from chief cells
- converted to pepsin (digests protein) by low pH
3) Mucus
- lubricates stomach lining protecting it from acid

23
Q

What enzyme is found in the stomach and how do the ions move?

A

Carbonic anhydrase catalyzes the dissociation of carbonic acid
- H+ is exchanged for K+ in gastric pit lumens
- H+ is constantly returned to the stomach

24
Q

What is heartburn caused by and how can it be solved?

A
  • Heartburn occurs when the lower esophageal sphincter relaxes and excess acids flow up into your esophagus
  • Tums (antacid) weaken the stomach acid as they contain CaCO3, MgOH, AlOH, NaCO3
  • Drugs like Prilosec and Nexum (proton pump inhibitors) block H+ pumps in the stomach that produce acid
25
Q

What are the parts and functions of the small intestine?

A

1) Duodenum (most digestion occurs here)
- beginning of small intestine
- site of secretion of pancreatic juices and bile
- gets hit by gastric juices (common in peptic ulcers)
2) Jejunum: (absorption)
- upper 40% of small intestine above duodenum
3) Ileum: (absorption)
- lower part of small intestine

26
Q

What moves food between the small and large intestine?

A

Ileocaecal Sphincter

27
Q

What are the purposes of the small intestine?

A

1) Primary site of absorption
2) Site where accessory organs secrete products (liver, gallbladder, pancreas)
3) Site where lipid digestion begins
4) Where most digestion is completed

28
Q

What structures in the small intestine help with absorption and how?

A

Villi: highly folded tissue
Microvilli: epithelial cells with projections

  • Increase surface area for absorption
29
Q

What do the cells lining the small intestine release?

A

1) Disaccharidase
- disaccharides –> monosaccharides (carbs)
2) Peptidase
- protein fragments –> amino acids
3) Nucleases
- DNA/RNA –> nucleotides
4) Choleocystokinin (CCK): hormones released from intestinal mucosal cells
- stimulates release of bile and pancreatic juices

30
Q

What does the pancreas do and what does it produce?

A

The pancreas secretes digestive juices into the small intestine (duodenum) via the pancreatic duct.

a) Bicarbonate: to reduce the acidity of gastric juices

b) Enzymes: (functions best at neutral or slightly basic pH)
1) Pancreatic Amylase: polysaccharides –> disaccharides
2) Trypsin & Chymotrypsin: proteins –> protein fragments
3) Peptidase: protein fragments –> amino acids
4) Nucleases: DNA/RNA –> nucleotides
5) Lipase: triglycerides –> free fatty acids and glycerol

no digestion in the pancreas

31
Q

What do the liver and gallbladder do?

A
  • synthesizes bile salts from cholesterol and secretes them as bile
  • bile stored in gallbladder
  • contains phospholipids and bilirubin
  • bile breaks down fats into micelles
32
Q

What organs are present in the large intestine and what are their functions?

A

1) Cecum (pouch at beginning of large intestine)
2) Ascending Colon
3) Transverse Colon
4) Descending Colon
5) Anal Sphincter (allows for defecation)
6) Appendix
- at beginning of large intestine
- no known digestive function
- may have role in immunity (good bacteria)

33
Q

What are the functions of the large intestines?

A

1) absorbs almost all water
2) absorption of bile acids to be recycled
3) concentrates and stores fecal material (unwanted/undigestible waste)

34
Q

What are the three ways that food in stomach is regulated?

A

1) Gastrin
2) Cholecystokinin
3) Secretin

35
Q

How does gastrin function?

A
  • Released as a stretching of the stomach from mucosal cells into blood
    Stimulates:
    1) release of HCl and Pepsin (digestion)
    2) Increased stomach contractions (churning)

*HCl has negative feedback, low pH = low gastrin

36
Q

How does cholecystokinin(CCK) function?

A
  • Released from small intestine mucosa when fat/lipid enters duodenum
    Stimulates:
  • release of bile by gallbladder and pancreatic enzymes

**CCK has negative feedback, decreases churning

37
Q

How does secretin function?

A
  • Released by duodenum mucosa when chyme reaches small intestine
    Stimulates:
  • Release of pancreatic bicarbonate which neutralizes HCl

**Secretin has negative feedback, decreases churning

38
Q

What is energy?

A

capacity to do work

39
Q

What is a calorie?
What is a kilocalorie?

A

A calorie is the amount of heat needed to raise 1 gram of water by 1 degree Celsius

  • 1 kcal = 1000 calories
  • 1 Cal = 1 kcal
40
Q

What are the basal expenditures for male and females?

A

Female: 1300-1500 cal/day
Male: 1600-1800 cal/day

**Exercise increases this number

Biolology (7 decks)

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