Digestive System

Question 1

What does the GI tract do

Answer 1

Moves nutrients, water and electrolytes from the external environment to the internal environment

Question 2

Function of the digestive system

Answer 2

Breaks down large molecules to small, soluble molecules that can be absorbed and used by body cells

Question 3

7 activities of the digestive system

Answer 3

1. Ingestion
2. Mastication
3. Deglutination
4. Digestion
5. Absorption
6. Peristalsis
7. Defecation

Question 4

Ingestion

Answer 4

Intake of food into the mouth

Question 5

Mastication

Answer 5

Chewing food which pulverises it and mixes it w saliva

Question 6

Deglutination

Answer 6

Swallowing, moving food from mouth to pharynx and to the oesophagus

Question 7

Digestion

Answer 7

Mechanical and chemical breakdown of food to prepare it for absorption

Question 8

Absorption

Answer 8

Passage of food molecules through mucous membrane of the small inetstine and into blood and lymph for distribution to cells

Question 9

Peristalsis

Answer 9

Wavelike contractions of the smooth muscle of the intestines that move food through GI tract

Question 10

Defecation

Answer 10

Discharge of indigestible waste from GI tract

Question 11

What does the food entering the digestive system pass through

Answer 11

1. Mouth
2. Pharynx
3. Oesophagus
4. Stomach
5. Small Intestine
6. Large Intestine

Question 12

The 4 layers of the wall of the GI tract and what they are made of/ secrete

Answer 12

1. Mucosa: mucous membrane, contains glandular cells that secrete digestive enzymes and goblet cells that secrete mucous
2. Submucosa: contains blood vessels
3. Muscularis: a layer of circular muscle and longitudinal muscle
4. Serosa: secretes serous fluid that keeps outer surface moist

Question 13

Mechanical digestion

Answer 13

In the oral cavity as teeth crush food and in the stomach as its muscular walls churn food

Question 14

Chemical digestion (3)

Answer 14

1. HCl denatures proteins
2. Bile salts emulsify lipids
3. Specific enzymes hydrolysis chemical bonds

Question 15

What does saliva consist of (3)

Answer 15

1. Water
2. Mucous
3. Digestive enzyme salivary amylase

Question 16

What happens after the food is chewed and moistened

Answer 16

The tongue forms a ball like mass called a bolus and pushes it into the upper part of the throat, the pharynx

Question 17

Where does the food go after the pharynx

Answer 17

Food enters the oesophagus and moves down towards the stomach

Question 18

What regulates entry into the stomach

Answer 18

The lower oesophageal sphincter

Question 19

What is secreted by the stomach

Answer 19

Gastric juice is secreted by gastric glands in the stomach

Question 20

What type of digestion occurs in the stomach

Answer 20

• Chemical (gastric juices)
• Mechanical (churning of the stomach)

Question 21

What do the specialised epithelial cells in the stomach do

Answer 21

Secrete mucous to protect the stomach lining from being attacked by acid and pepsin

Question 22

4 regions of the stomach

Answer 22

1. Cardia
2. Fundus
3. Body
4. Pylorus

Question 23

4 layers of the stomach wall

Answer 23

1. Mucosa
2. Submucosa
3. Muscularis
4. Serosa
   (same as other 4 tunicas found in the other regions of GI tract)

Question 24

the 5 types of cells in the gastric glands and what they secrete

Answer 24

1. Goblet cells: secrete protective mucous
2. Parietal cells: secrete HCl
3. Chief cells: secrete pepsinogen
4. Argentaffin cells: secrete serotonin, histamine, autocrine regulators
5. Endocrine cells (G cells): secrete the hormone gastrin into the blood

Question 25

How does the stomach control the production of gastric juice

Answer 25

A hormone, gastrin

Question 26

What happens when the chyme is ready to leave the stomach

Answer 26

The gate of the small intestine, the pyloric sphincter, opens and allows limited amounts of chyme to pass

Question 27

What does the pancreas secrete (2)

Answer 27

* **Pancreatic juice including enzymes** * An **alkaline solution** that **neutralises the acidic chyme to provide an environment where the enzymes can act**

Question 28

How does the liver aid in digestion

Answer 28

Aids in the digestion of lipids by secreting bile. Bile contains bile salts which emulsify lipids.

Question 29

Where does most of the digestion take place

Answer 29

The small intestine

Question 30

What is the first 25cm of the S.I known as and what occurs here (3)

Answer 30

The duodenum: 1. Starches and glycogen are broken down to sugars 2. Proteins are broken down to amino acids 3. Triglycerides are broken down to fatty acids and glycerol

Question 31

How are nutrients absorbed in the S.I

Answer 31

* Mucosa and submucosa of S.I thrown into folds, which are covered by projections called villi * The epithelial cells of the villi are covered in microvilli * Within each villus are a network of capillaries and a lymphatic vessel * Each amino acid and monosaccharide must use a carrier molecule to get into an epithelial cell of a villus * Once they are in the epithelial cells they eventually accumulate and move by facilitated diffusion through the base of the cell and into the blood * In bloodstream they are taken to the liver for processing and storage

Question 32

How are lipids absorbed

Answer 32

* After triglycerides are broken down into fatty acids and glycerol they become surrounded by **bile salts called micelles** * The shell of the bile salt is discarded and they move easily across the membrane and into the cell * **Short chained fatty acids are absorbed directly into bloodstream** * **Longer chained fatty acids are reasembled into triglycerides by the ER** and **encased in a protein** (particle known as a **chylomicron**) * After processing they pass **out of the epithelial cell and into the lymphatic fluid** * The **chylomicrons pass through the capillaries of the liver and adipose tissue** and an **enzyme breaks them down to fatty acids and glycerol** * These **products diffuse from blood stream into liver and adipose tissue** where they are **resynthesised into triglycerides** and **stored for later when energy is required**

Question 33

Role of large intestine (colon) (3)

Answer 33

1. Absorb sodium ions and water 2. Eliminate wastes 3. Provide a home for friendly bacteria