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Flashcards in GI Physiology Deck (92)
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1

What are the 6 steps in digestion?

See picture

1. Ingestion

2. Mechanical digestion

3. Propulsion

4. Chemical digestion

5. Absorption

6. Defecation

2

Layers (Tunics) of GI Wall

4

1. Mucosa

2. Submucosa

3. Circular and Longitudinal Smooth Muscle

4. Serosa

 

3

Mucosa

1. What does this layer face?

2. Made of? Specialized for?

3. Blood supply?

Submucosa

4. What does it consist of? 4

Circular and Longitudinal Smooth Muscle

5. Function?

Serosa

6. Faces what?

Mucosa

1. Innermost layer (faces lumen)

2. Layer of epithelial cells specialized for absorption and secretion

3. Highly vascularized

Submucosa

4. Consists of collagen, elastin, glands, and blood vessels

Circular and Longitudinal Smooth Muscle

5. Provides motility for GI tract

Serosa

6. Faces the blood

4

What enzymes break down food in the mouth?

2

1. lingual amylase

   carb. (step 1)

2.  lingual lipase

     lipid (step 1)

5

1. ____muscles and 2.___cranial nerves (600 times/daily)

3. What does the esophageal phase of swallowing begin with?

4. Composition of Saliva→ Secreted by ______ and _______cells

5. What is saliva composed of? 6

1. 26

2. 5

3. 

-Begins with crico-pharyngeal relaxation

-Involuntary

4. serous and mucous

5. 

a) 97–99.5% water, slightly acidic

b) lytes—Na+, K+, Cl–, PO4 2–, HCO3–

c) Salivary amylase and lingual lipase

d) Mucin

e) Metabolic wastes—urea and uric acid

f) Lysozyme, IgA and a cyanide compound protect against microorganisms

6

1. Salivary glands produce how much saliva a day?

2. Functions of saliva? 4

1. Salivary glands produce 1 L/day of saliva

-Each gland delivers saliva to mouth through a duct

 

Functions of saliva

1. Initial digestion of starches and lipids by salivary enzymes

2. Dilution and buffering of ingested foods

3. Lubrication of ingested food to aid its movement

4. Many more functions

7

Secretions are produced by what? 4

What do secretions add to the lumen of GI tract? 4

Secretions produced by

1. Salivary glands (saliva)

2. Gastric mucosal cells (gastric secretion)

3. Pancreatic exocrine cells (pancreatic secretion)

4. Liver (bile)

 

Addition of GI tract:

1. fluids,

2. enzymes,

3. electrolytes

4. mucus

8

Function: 

1. Stomach?

2. Small intestine?

3. Large intestine?

1. Stomach: digestion and break down of food to smaller, absorb-able particles.
 

2. Small intestine: absorption of nutrients
 

3. Large intestine: absorption of water

9

1. What is the stomach specialized for?

2. Holds how much?

3. Gastric juice converts food into semiliquid called what?

4. 4 parts of the stomach?

1. Specialized for accumulation of food

2. Capable of considerable expansion (can hold 2-3L)

3. Gastric juice converts food into semiliquid called chyme

4. 4 Parts

-Cardia

-Fundus

-Body

-Pylorus

10

Functions of Stomach

6

1. Short-term storage reservoir

2. Absorption, digestion and secretion

3. Chemical and enzymatic digestion is initiated, particularly of proteins

4. Liquefaction of food→ chyme

5. Slowly released into the small intestine for further processing

6. The stomach uses pepsin and peptidase (enzymes) to break down proteins

 

11

Why is the acidic anvironment of the stomach important?

The acid  provides good environment for the enzymes to work in.

12

What are the Three Phases of Digestion?

 

 

1. Cephalic Phase                                

2. Gastric Phase

3. Intestinal Phase

13

1. Cephalic Phase: What structures are involved? 4                       

2. Gastric Phase: What substances are involved? 2

3. Intestinal Phase: What hormone is involved?

Cephalic Phase :

1. Cortex,

2. amygdala

3. hypothalamus

4. vagus nerve                                                               

Gastric Phase:

1. hydrochloric acid

2. pepsin

 

Intestinal Phase:

1. enterogastrone Hormones secreted in duodenum and lower GI tract.

14

1. During cephalic and gastric phases, stimulation by vagal nerve fibers causes release of what?

2. Acidic chyme entering duodenum causes the enteroendocrine cells to release what?

3. Whereas fatty, protein rich chyme induces release of what?

4. Where do these two enzymes go next?

 

1. pancreatic juice and weak contractions of the gallbladder

2. secretin

3. cholecystokinin

4. Blood stream

15

1. Upon reaching the pancreas, cholecystokinin induces the secretion of what?

2. Secretin causes copious secretion of what?

1. enzyme-rich pancreatitis juice

2. bicarbonate-rich pancreatic juice

16

1. Gastric mucosal cells secrete what?

2. What two substances initiate protein digestion?

3. What is required for absorption of Vit B12?

4. Body of the stomach conatins what kind of glands?

5. Atrum of the stomach conatins what kind of glands?

6. What protects gastric mucosa from HCL?

1. gastric juice

2. HCl and pepsinogen initiate protein digestion

3. Intrinsic factor required for absorption of vitamin B12

4. Body of stomach contains oxyntic glands

5. Antrum of stomach contains pyloric glands

6. Mucus protects gastric mucosa from HCl

17

1. What are the two types of cells in the body of the stomach?

2. What are the two types of cells in the antrum of the stomach?

1. Parietal cells and Chief cells

2. G cells and Mucous neck cells

18

1. What do parietal cells secrete? 2

2. What do chief cells secrete? 1

3. G cells secrete what? 1

4. What do mucous neck cells secrete? 3

1. Parietal cells → HCl and Intrinsic Factor

2. Chief cells → Pepsinogen

3. G cells → Gastrin into the circulation

4. Mucous neck cells → Mucus, HCO3-, and Pepsinogen

19

1. Gastrin: Secreted by G cells in stomach in response to what?

2. Stimuli includes what? 3

3. Gastrin promotes what kind of secretion?

4. Stimulates the growth of what?

5. What is its secretion inhibited by?

1. eating

2. 

-proteins,

-distention of stomach

-vagal stimulation

3. Promotes H+ secretion by gastric parietal cells

4. Stimulates growth of gastric mucosa

5. Low pH in the stomach

20

Other Functions of GASTRIN HORMONE:

4

1. Pepsinogen release

2. Increase stomach motility

3. Relax pyloric sphincter

4. Contract LES

21

Regulation of HCl Secretion

What three hormones are involved in this?

1. ACh

2. Histamine

3. Gastrin

22

1. ACh is realeased from?

2. Binds to receptors where?

3. Produces what by parietal cells?

4. What blocks muscarinic receptors on parietal cells?

1. Released from vagus nerve

2. Binds to receptors on parietal cells

3. Produces H+ secretion by parietal cells

4. Atropine blocks muscarinic receptors on parietal cells

23

1. Histamines released from mastlike cells where?

2. Binds to what on parietal cells?

3. Produces what by parietal cells?

4. What block H2 receptors?

1. Released from mastlike cells in gastric mucosa

2. Binds to H2 receptors on parietal cells

3. Produces H+ secretion by parietal cells

4. Cimetidine blocks H2 receptors

24

Gastrin

1. Released into circulation by what of stomach antrum?

2. Binds to receptors of what cells?

3. Stimulates what?

1. Released into circulation by G cells of stomach antrum

2. Binds to receptors on parietal cells

3. Stimulates H+ secretion

25

What are the two general processes that cause peptic ulcers?

Increased damage

Impaired host defenses

26

What things could cause increased damage in the stomach causing a peptic ulcer? 8

 

What things could cause impaired defenses in the stomach that lead to peptic ulcers? 3

See picture

27

What is segmentation contractions?

2

1. Circular muscle contracts sending chyme in both  directions

2. Intestine then relaxes allowing chyme to merge back together

28

What is peristalic contractions? 2

1. Longitudinal muscle contracts propeling chyme along small intestine

2. Simultaneously, portion of intestine caudad to bolus relaxes

29

1. What are the enzymes (2) in the salivary glands and what are their targets (2)?

2. What are the enzymes (2) in the stomach and what are their targets (2)?

3. What are the enzymes (5) in the Pancreas and what are their targets (5)?

4. What are the enzymes (3) in the intestine and what are their targets (3)?

See picture

30

Autonomic Nervous System has an extrinsic and an intrinsic component

1. Extrinsic controls what? 2

2. What is the intrinsic also called?

3. Contained where?

4. Communicates with what?

1. Extrinsic

-Sympathetic and

-Parasympathetic innervation of GI tract

Intrinsic

2. Called Enteric Nervous System

3. Contained within wall of GI tract

4. Communicates with Extrinsic component