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Flashcards in Digestive System Deck (68)
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1

List the structures in order that occur in the digestive tract

1. oral cavity (mouth)
2. pharynx
3. esophagus
4. stomach
5. small intestine
6. large intestine
7. rectum
8. anus

2

Alimentary Canal

-runs from mouth to anus and is sectioned off by sphincters
-nutrients are obtained from food within the lumen of this canal and is known as extracellular digestion ("outside the body")

3

Absorption

involves the transport of products of digestion from the digestive tract into the circulatory system for distribution to the body's tissues and cells

4

Enteric Nervous System

-collection of millions of neurons that help govern the function of the GI system
-neurons are present in the walls of the digestive tract and trigger peristalsis (rhythmic contractions of the gut tube in order to move material through system)
-can function independently of the brain and spinal cord, but is heavily regulated by the autonomic NS

5

What occurs when the parasympathetic NS stimulates the GI tract?

-increases secretions from exocrine glands
-promotes peristalsis
-stimulates GI activities

6

What occurs when the sympathetic NS stimulates the GI tract?

-decreased secretions from exocrine glands
-inhibition of peristalsis
-decreased blood flow to GI tract
-slowed gut motility
-overall inhibition of GI activities

7

What is the only gland in the body that is not innervated by the parasympathetic NS?

sweat glands

8

Oral Cavity

-plays a role in both mechanical and chemical digestion of food
-mastication (chewing) occurs
-enzymes produced in the salivary glands begin breaking down chemical bonds in food macromolecules
-salivary glands are innervated by the parasympathetic NS

9

What are the two enzymes found in the oral cavity?

-salivary amylase: hydrolyzes starch into smaller sugars (maltose and dextrins)
-salivary lipase: catalyzes the hydrolysis of lipids

10

Pharynx

-cavity that leads from mouth and posterior nasal cavity to the esophagus
-connects both the esophagus and larynx
-food is prevented from entering the larynx during swallowing by the epiglottis
-can be divided into 3 parts: nasopharynx (behind nasal cavity), oropharynx (back of the mouth), laryngopharynx (above vocal cords)

11

Esophagus

-connects pharynx to stomach
-top third is composed of skeletal muscle so it is under somatic (voluntary) motor control
-bottom third is composed of smooth muscle so it is under autonomic (involuntary) control
-middle third is composed of both muscle types
-upper esophageal sphincter and lower esophageal sphincter (cardiac sphincter) are located here

12

Stomach

-highly muscular organ that uses hydrochloric acid and enzymes to digest food
-thick mucosa to prevent autodigestion
-can be divided into 4 divisions: fundus, body, antrum, pylorus
-mucosa contains gastric glands and pyloric glands
-mainly an organ of digestion, not so much absorption

13

Gastric Glands

-respond to signals from the vagus nerve of the parasympathetic NS, which activated by the brain in response to the sight, smell, and taste of food
-contain 3 different cell types: mucous cells, chief cells, parietal cells

14

Mucous Cells

produce the bicarbonate-rich mucus that protects the stomach wall from the acidic (pH=2) and proteolytic environment of the stomach

15

Gastric Jucie

combination of secretions from chief cells and parietal cells

16

Chief Cells

secret pepsinogen (inactive, zymogen, form of pepsin, a proteolytic enzyme) which digests proteins

17

Parietal Cells

-secrete hydrochloric acid (HCl) which has hydrogen ions that cleave pepsinogen to pepsin, decreases the pH, kills microbes, and denatures proteins
-secrete intrinsic factor (glycoprotein involved in proper absorption of vitamin B12)

18

Pepsin

-digests proteins by cleaving peptide bonds near aromatic amino acids, resulting in short peptide fragments
-activated by the acidic stomach environment

19

G Cells

-located in pyloric glands
-secrete gastrin

20

Gastrin

-peptide hormone
-induces the parietal cells in the stomach to secrete more HCl
-signals the stomach to contract and mix its contents -- increases gastric motility

21

Chyme

acidic, semifluid mixture that results from digestion of solid food in the stomach

22

What 2 substances can be directly absorbed from the stomach?

-alcohol
-aspirin

23

What are the 6 products secreted by the stomach?

1. HCl
2. Pepsinogen
3. Mucus
4. Bicarbonate
5. Water (dissolves and dilutes ingested material)
6. Intrinsic Factor

24

Small Intestine

-food leaves stomach and enters here via the pyloric sphincter
-consists of 3 segments: duodenum, jejunum, ileum

25

Duodenum

-responsible for the majority of chemical digestion
-presence of chyme here causes the release of brush-border enzymes like disaccharidases and peptidases
-secretes enteropeptidase (involved in activation of other digestive enzymes from the accessory organs)
-secretes secretin and cholecystokinin (CCK) into the bloodstream

26

Brush-Border Enzymes

-present on the liminal surface of cells lining the duodenum
-break down dimers and trimers of biomolecules into absorbable monomers

27

Maltase

-secreted by intestinal glands
-functions in the duodenum
-hydrolyzes maltose to two glucose molecules

28

Isomaltase

-secreted by intestinal glands
-functions in the duodenum
-hydrolyzes isomaltose into two glucose molecules

29

Sucrase

-secreted by intestinal glands
-functions in the duodenum
-hydrolyzes sucrose to glucose and fructose

30

Lactase

-produced by intestinal glands
-functions in the duodenum
-hydrolyzes lactose to glucose and galactose