L1: intro to digestive system

Question 1

What is the overall function of the digestive system?

Answer 1

• food for energy and synthetic processes
• breaks down the nutrients into sub-units small enough for the body to absorb
• distribute the nutrients via circulation to cells for energy, growth and cell repair

Question 2

Components of the alimentary tract

Answer 2

• oral cavity, teeth, tongue
• pharynx
• oesophagus
• stomach
• large intestine
• small intestine

Question 3

Do nutrients become more or less available as you go further down the alimentary tract?

Answer 3

More available

Question 4

Accessory digestive organs

Answer 4

Salivary glands, liver, gallbladder, pancreas

Question 5

Exocrine glands out of the alimentary tract and accessory digestive organs

Answer 5

Salivary glands, liver, stomach, pancreas, small intestine

Question 6

What is a gland?

Answer 6

A gland is a functional unit of cells that works together to create and release a product into a duct or directly to the bloodstream

Question 7

Difference between exocrine and endocrine glands

Answer 7

Exocrine - makes a product to be released into a duct

Endocrine - makes a product to be released directly into the bloodstream

Question 8

Physical functions of the GI tract

Answer 8

Ingestion - taking food into the mouth
Mastication - chewing and mixing food with saliva
Deglutition - swallowing
Motility - movement of food through GIT

Question 9

Different types of motility in GIT

Answer 9

Peristalsis - propulsive - moves food

Segmentation - no net movement - mixes good

Question 10

What is peristalsis?

Answer 10

Successive waves of rhythmic contractions and relaxation that moves food in one direction

Question 11

What is segmentation?

Answer 11

Alternating forward/backward movements that mixes partially digested chyme and digestive juices and brings chyme into contact with the gut wall.

Question 12

Physiological functions of the GIT

Answer 12

Digestion - mechanical or chemical breakdown of carbs proteins and fats into subunits small enough to cross the gut wall
Absorption - subunits, water, ions all cross the epithelial lining of the small intestine and enter blood or lymph vessels
Secretion - digestive organs secrete many substances to aid digestion and absorption
Storage and elimination - temporary storage and elimination of indigestible food

Question 13

How is the alimentary tract adapted to have a high absorptive surface area?

Answer 13

Folds of Kerckring (plicae circulates) - extensive folds of mucosa and submucosa
Villi - fingerlike projections lines with absorptive cells called enterocytes
Microvilli (brush border) - plasma membrane extensions of absorptive enterocytes

Question 14

Mechanisms of absorption

Answer 14

• Simple diffusion
• Facilitated diffusion (faster than simple)
• Active transport

Question 15

What aids control of the GI tract?

Answer 15

Hormones, nerves, paraffins factors

Question 16

Why should dentists study the GI tract?

Answer 16

Poor dental and periodontal health may be a reflection of what is going on in the gut:
Xerostomoa, Ernest’s (vomiting), GORD, H.pylori infection, Fat malabsorption (vitamin deficiency), bile duct injury, gallstones, GI cancers

Poorly chewed food has less contact with digestive enzymes and hence leads to poor absorption, halitosis, Coeliac disease, IBD