Overview of GIT

Question 1

GIT

Answer 1

The GIT is an open-ended muscular tube

• about 4.5 m in an adult living human
• called also digestive tract / gut / alimentary canal

Question 2

Major functions of the GIT

Answer 2

6 steps. 4 basic processes:
– Ingestion
– 1. Motility / propulsion – 2. Digestion
– 3. Secretion
– 4. Absorption
– Elimination (defecation)

Question 3

Muscularis externa

Answer 3

Produces the food through
Outer longitudinal muscle
Inner circular muscle

Question 4

Mucosa

Answer 4

Mucous membrane
Lamina propria
Muscularis mucosa

Question 5

The GIT wall: 4 functional types of epithelium

Answer 5

Protective: oral cavity, pharynx, oesophagus and anal canal
Secretory: stomach
Absorptive: small intestine
Absorptive/Protective: large intestine

Question 6

2 types of digestive motility

Answer 6

1. Peristalsis

2. Segmentation

Question 7

1. Peristalsis

Answer 7

Adjacent segments of the alimentary canal organs alternately contract and relax.
• Food is push FORWARD through the digestive tract

Question 8

2. Segmentation

Answer 8

Nonadjacent segments of the alimentary canal organs contract and relax
• MIX food with DIGESTIVE JUICES and help with ABSORPTION
• MIX food with DIGESTIVE JUICES and help with ABSORPTION

Question 9

Regulation of GIT functions

1. involuntary control.

Answer 9

1. involuntary control and
   voluntary:
   Only the first part – ingestion and swallowing, and the last part – defecation are under voluntary

Question 10

long reflexes

Answer 10

visual and sensory stimuli > Salivary center in medulla > Autonomic nerves>Salivary glands > inc. Salivary glands

Question 11

Functions of oral cavity*

Answer 11

• Ingestion and sensory analysis of material (before swallowing)
• Mastication (mechanical processing) – through actions of teeth, tongue, and palatal surfaces
• Lubrication – mixing with mucus and salivary gland secretions
• Limited digestion – of carbohydrates & lipids
*Phonation & ventilation

Question 12

Swallowing reflexes

Answer 12

The reflex is initiated by touch receptors in the pharynx as a bolus of food is pushed to the back of the mouth by the tongue, or by stimulation of the palate (palatal reflex).

Swallowing is a complex mechanism using both skeletal muscle (tongue) and smooth muscles of the pharynx and esophagus. The autonomic nervous system (ANS) coordinates this process in the pharyngeal and esophageal phases.

Question 13

Stomach structure

Answer 13

Stomach – a muscular chamber, inferior to the diaphragm.

Question 14

Three main parts of the stomach:

Answer 14

1. Fundus – dome-shaped region beneath the diaphragm
2. Body (oxyntic mucosa) – mid- portion of the stomach
   – many gastric glands
3. Antrum – the lower part
   – terminates at the pyloric sphincter
   (continues into the duodenum)

Question 15

stomach functions

Answer 15

Functions:
• 1. Stores ingested food and begins some digestion
• 2. Secretes hydrochloric acid (HCl) and enzymes that begin protein
digestion.
– Producestheintrinsicfactor
• 3. Mixes the food bolus and produces a creamy paste (chyme) mixture
• Also participates in some digestion
– Mechanical break up of food particles - liquefies the food – Chemical digestion
• Absorption: water, ions, alcohol and aspirin

Question 16

Peristaltic contraction in the stomach

Answer 16

1. GASTRIC EMPTYING

2. GASTRIC MIXING