Mouth, Oesophagus & Stomach

Question 1

Major Organs of Digestive Tract

Answer 1

Oral cavity (mouth)
Pharynx
Oesophagus
Stomach
Small intestine
Large intestine

Question 2

Accessory Organs of the Digestive System

Answer 2

Teeth
Tongue
Salivary glands
Liver
Gallbladder

Question 3

Gastrointestinal (GI) System Function

Answer 3

Food: ingested -> digestion: essential for -> absorption: excretion of -> waste
Absorbs water, carbohydrates (sugars), fats (fatty acids), proteins (amino acids), vitamins and minerals

Question 4

Secretion

Answer 4

Enzymes:
- Salivary glands - breaks down carbs
- Stomach - breaks down proteins/peptides
- Pancreas - breaks down proteins/peptides and carbs
Ions:
- Stomach - H+ (acid)
Other Secretions:
- Liver - bile
- Pancreas - acid-neutralising buffers
- Duodenum - acid-neutralising buffers

Question 5

Types of Digestion

Answer 5

Essential for breakdown of food and absorption of nutrients

1. Mechanical - motility patterns
2. Chemical - secretions

Question 6

Absorption

Answer 6

Enables nutrients to enter the bloodstream

Question 7

Where does Absorption occur?

Answer 7

Stomach - water
Small intestine - 90% of nutrients, salt, water
Large intestine - salt & water

Question 8

Location of GI System

Answer 8

Abdominal cavity
Most of intestinal tract is suspended in the peritoneal cavity
Held in place by mesenteries

Question 9

Visceral Peritoneum

Answer 9

Lines organs

Question 10

Parietal Peritoneum

Answer 10

Lines the body wall

Question 11

Mesenteries

Answer 11

Double fold of peritoneum
Contains blood vessels, nerves, lymphatics
Attaches intestines to posterior abdominal wall
Holds intestines in place

Question 12

What does the Oral Cavity do?

Answer 12

Mechanical processing
Moistening
Mixing with salivary secretions

Question 13

Salivary Glands

Answer 13

Parotid
Sublingual
Submandibular

Question 14

Pharynx

Answer 14

Passageway for food, liquid, air

Muscular propulsion of food material into the oesophagus

Question 15

Epiglottis

Answer 15

Prevents passage of food & liquid into lungs
1st act of swallowing is under control of skeletal muscle (voluntary)
2nd part of swallowing is under smooth muscle control (involuntary)
Located above the larynx

Question 16

Oesophagus

Answer 16

Conveys food and liquid into the stomach

Unidirectional

Question 17

Layers of the Oesophagus

Answer 17

1. Mucosa - lines the lumen
2. Submucosa - folds of mucosa & submucosa enable expansion when swallowing
3. Muscularis (smooth muscle) - keeps the lumen closed during inactivity
4. Adventitia - provides a connective tissue coating

Question 18

Stomach

Answer 18

Mechanical breakdown: muscular contractions
Chemical breakdown: acid & enzymes
Storage

Question 19

Stomach: Mechanical Breakdown

Answer 19

Muscular wall - 3 layers:
- Longitudinal (outer)
- Circular (middle)
- Oblique (inner)
Assists in mixing & churning
Essential to chyme (food and stomach acid) formation/exposure to enzymes/acid

Question 20

Stomach: Storage

Answer 20

Rugae (muscular folds) - allow distention
Capacity - 1-1.5L
Stores chyme
Pyloric sphincter controls the rate of chyme release into the small intestine

Question 21

Stomach Wall

Answer 21

1. Mucosa - simple, columnar epithelium; produces mucus to protect cells from acid/enzymes
2. Submucosa - structure, flexibility
3. Muscularis externa - contract & release to churn the chyme and stimulate the enzymes to make the chyme
4. Serosa - allow the GI system to move without causing friction with other structures

Question 22

Stomach: Chemical Breakdown

Answer 22

Gastric glands secrete acid and enzymes
Parietal cells secrete hydrochloric acid
G cells detect stomach acid level to keep it at the optimum level & secretes gastrin
Chief cells secrete pepsinogen

Question 23

Peristalsis

Answer 23

*Moves food through the digestive tract
Contractions moving the food bolus down the tract (oesophagus, stomach, small intestine, large intestine) by propulsion
1. Bolus of food arrives in digestive system
2. Circular muscles contract behind bolus
3. Longitudinal muscles ahead of bolus contract
4. Contraction in circular muscle layer forces bolus forward

Question 24

Segmentation

Answer 24

*Mixes the food during digestion
Mechanical digestion - mixing (not movement)
Mix bolus with secretions, release nutrients from bolus
Location: small & large intestines

Question 25

Blood Supply: Arteries

Answer 25

3 branches of celiac trunk artery supply the abdominal viscera
Celiac trunk artery branches off the abdominal aorta

Question 26

Blood Supply: Veins

Answer 26

Hepatic portal vein drains the abdominal viscera

Hepatic portal circulation sends blood directly to the liver instead of back to the heart

Question 27

Portal Circulation

Answer 27

Oxygenated blood comes from the heart -> travels into artery -> into first capillary bed (stomach/intestines) -> through hepatic portal vein -> into second capillary bed (liver) -> into veins and back to heart