Chapter 24: The Digestive System

Question 1

What are the 6 essential functions of the digestive system?

Answer 1

1. Ingestion
2. Secretion
3. Mixing and propulsion
4. Digestion (mechanical & chemical)
5. Absorption
6. Defecation

Question 2

What are the 4 layers throughout the digestive tract walls?

Answer 2

1. Mucosa (innermost; lining lumen)
2. Submucosa
3. Muscularis
4. Serosa (outermost)

Question 3

Mesentery

Answer 3

Connects the small intestine to the posterior body wall

Question 4

Falciform ligament

Answer 4

Attaches the liver to the anterior body wall and diaphragm

Question 5

Mesocolon

Answer 5

Connects the large intestine to the posterior body wall

Question 6

Which organ lacks a serosa layer? What is the layer called instead?

Answer 6

The esophagus

The layer is called adventitia

(i.e. mucosa, submucosa, muscularis, adventitia)

Question 7

What are the 2 layers of the muscular portion of the digestive tract calls? What organ has a 3rd layer and what is it called?

Answer 7

1. Inner circular muscle
2. Outer longitudinal muscle

The stomach has a 3rd layer called the oblique smooth muscle layer which comes before the other 2.

Question 8

What is the difference between an omentums and mesenteries?

Answer 8

Omentums bind organs to eachother.

Mesenteries bind organs to the abdominal wall.

Question 9

What are the 2 control mechanisms involved in regulating the digestive functions of muscle motility and secretions ?

Answer 9

1. Endocrine control - involves various hormones (gastrin, secretin, CCK)
2. Neural control - uses chemoreceptors and stretch receptors to send sensory input to the enteric NS and autonomic NS (both systems will control gut motility and GIT secretions)

Question 10

What is the myenteric plexus?

Answer 10

Part of the enteric NS located in the gut wall between the circular and longitudinal muscle layers.

It controls gut motility

Question 11

What is the submucosal plexus?

Answer 11

Part of the enteric NS located within the submucosa layer.

Controls GIT secretions

Question 12

Which nervous system increases GIT activity and which one decreases it?

Answer 12

Parasympathetic - increases GIT activity

Sympathetic - decreases GIT activity

Question 13

What secretion is made in the mouth and what does it do?

Answer 13

Salivary glands near the mouth will secrete salivary amylase into the mouth to begin carbohydrate digestion to turn starch into sugar.

Question 14

What are the steps of swallowing?

Answer 14

1. Tongue pushed food against hard palate and stimulates receptors for swallow initiation in pons/medulla
2. The soft palate and uvula rise to close nasopharynx and allow food to pass through
3. Epiglottis covers glottis and food passes through upper esophagus
4. Peristalsis propels food (bolus) down

Question 15

What is the main action of the esophagus?

Answer 15

Peristalsis

Occurs by circular muscle layer contracting to squeeze bolus downwards, and longitudinal muscle layer contracting to expand and receive the bolus.

Question 16

What are the 4 regions of the stomach?

Answer 16

1. Cardiac
2. Fundic
3. Body
4. Pyloric

Question 17

Parietal cells of the stomach

Answer 17

Produce HCL to maintain an acidic pH environment within the stomach.

Question 18

Chief cells of the stomach

Answer 18

Make pepsinogen that will be activated into pepsin by HCL, and then will be able to digest proteins

Question 19

Enteroendocrine cells of the stomach

Answer 19

Produce G cells that will secrete gastrin

Question 20

Mucus neck cells of stomach

Answer 20

Produce mucus to protect the lining of the lumen from the acidic HCL and pepsin

Question 21

How much gastric juice is secreted per day?

Answer 21

About 2-3 litres

Question 22

Absorptive cells of small intestine

Answer 22

Absorb and digest nutrients, and produce brush border enzymes (ex. Sucrose, Maltase)

Question 23

Goblet cells of small intestine

Answer 23

Make mucus to protect from HCL that traveled down from stomach

Question 24

Secretory cells of small intestine

Answer 24

Secret alkaline (basic pH) intestinal juice

This is water + mucus (includes NO enzymes)

Question 25

Paneth cells of small intestine

Answer 25

Secrete lysozyme

Question 26

Enterenocrine cells of the small intestine

Answer 26

S cells which secrete secretin

Question 27

How much nutrient absorbsion takes place in the small intestine?

Answer 27

90%

Question 28

What is the difference between peristalsis and segmentation?

Answer 28

**Peristalsis** involves adjacent segments alternatively contracting and relaxing to push food down **Segmentation** involves non-adjacent segments alternatively contracting and relaxing to mix food together in the small intestine

Question 29

What is the difference between and exocrine and endocrine gland? What percentages of the pancreas are these glands?

Answer 29

**Exocrine** - make secretions into a duct system (99% of the pancreas) Ex. Secrete pancreatic juice into ducts before it goes into the duodenum **Endocrine** - make secretions directly into the bloodstream (1% of the pancreas)

Question 30

What is pancreatic juice made up of

Answer 30

- Pancreatic amylase (to break down carbohydrates) - Pancreatic lipase (to break down lipids - Tripsinogen (to break down proteins) Others: water, salts, various enzymes

Question 31

Which lobe of the liver is bigger?

Answer 31

The right lobe is bigger than the left lobe

Question 32

What is a portal system?

Answer 32

Allows the transportation of something from one capillary bed to another capillary bed through a vein Ex. Hepatic portal vein

Question 33

What are liver cells called and what do they do?

Answer 33

Hepatocytes Functions to process nutrients arriving from the GIT through the hepatic portal vein (which gives the liver capillaries nutrient rich blood from the stomach-intestines capillaries ) They also produce 1L of bile per day

Question 34

What are kupffer cells in the liver?

Answer 34

Phagocytic cells able to destroy any worn out red or white blood cells, bacteria, and other foreign matter from venous blood coming from the GIT.

Question 35

What is bile made of? Does it have enzymes?

Answer 35

- mostly water and ions - bile salts (to emulsify lipids) - cholesterol - bile pigments (bilirubin) *NO ENZYMES* (makes sure to know for exam)

Question 36

Does bile use chemical or physical breakdown? Why is this the case?

Answer 36

Physical breakdown This is due to the fact that bile contains **no enzymes** so there is no chemical breakdown occurring

Question 37

Define amphipathic. What have we studied that relates to this?

Answer 37

Molecules that have both polar and non polar parts to it (therefore they can dissolve in water) Bile salts are an example of this

Question 38

What is emulsification?

Answer 38

The breakdown of large lipids into smaller lipids using **bile salts**

Question 39

What hormone stimulates the gall bladder to release bile into the duodenum?

Answer 39

CCK hormone

Question 40

Which hormone stimulates the liver to produce bile?

Answer 40

Secretin hormone

Question 41

Where is water absorbed? How is it absorbed

Answer 41

90% is absorbed in the small intestine 10% is absorbed in the large intestine Both through the process of osmosis

Question 42

What are the 3 phases of digestion?

Answer 42

1. **Cephalic** - smell, sight, thought of food will activate neural centres and increase salivary/gastric activity 2. **Gastric** - food arrives in stomach, increase of motility and gastric gland activity 3. **Intestinal** - exit of food out of the stomach into the duodenum to be absorbed

Question 43

Are enzymes secreted in the large intestine?

Answer 43

**No**