GIT L1: Overview of GIT Flashcards
The GIT is an _______ muscular tube - about _____ m in an adult living human - called also digestive tract / gut / alimentary canal
open-ended; 4.5
Why does the mucus change in areas?
To stop infection..etc (different bacteria) due to the open-ended structures
What are the 6 major functions of the GIT (6 steps; 4 basic processes)?
- Ingestion
- Motility / propulsion
- Digestion
- Secretion
- Glands which secrete juices
- Absorption Get nutrients from
- Elimination (defecation)
What are the 4 layers of the GIT?
EXAM QUESTION
- Mucosa
- Submucosa
- Muscularis externa
- Serosa
The GIT is _____ within open ended structure.
homogenous
What are 2 characteristics of mucosa?
- Has different layers
- Where secretion produced and absorption occur
What are 2 characteristics of submucosa?
- Maintain mucosa in a particular shape
- Bring blood from vessels and nutrients to the mucosa
What are 2 characteristics of muscularis externa?
- Muscles used to push food forward
- Help stomach to have a mechanical breakdown (digestion)
What is a characteristic of serosa?
Overs the whole tube
What are 4 functional types of epithelium?
- Protective
- Secretory
- Absorptive
- Absorptive/Protective
What are 4 examples of protective epithelium in the GIT wall?
- oral cavity
- pharynx
- oesophagus
- anal canal
What is an example of secretory epithelium in the GIT wall?
stomach
What is an example of absorptive epithelium in the GIT wall?
small intestine
What is an example of absorptive/protective epithelium in the GIT wall?
large intestine
What are 2 types of digestive motility?
- Peristalsis
- Segmentation
What is peristalsis?
EXAM QUESTION
Adjacent segments of the alimentary canal organs alternately contract and relax.
- Food is push FORWARD through the digestive tract (no digestion occurs)
- Very strong (hang upside down –> can still each against gravity)
What is segmentation?
EXAM QUESTION
Nonadjacent segments of the alimentary canal organs contract and relax.
- Food is moved FORWARD THAN BACKWARD
- MIX food with DIGESTIVE JUICES and help with ABSORPTION
What are 2 ways to regulate GIT functions?
EXAM QUESTION
- Involuntary
- Voluntary
What are long reflexes in the GIT triggered by? EXAM QUESTION
External stimuli (sight, smell, taste, thought of food) system needs to prepare food by producing gastric juices
What are short reflexes in the GIT triggered by? EXAM QUESTION
Internal stimuli (food inside month) –> chemoreceptors, osmoreceptors or mechanoreceptors
Pressure receptors activated when food is in the mouth
What are 2 examples of salivation regulation?
EXAM QUESTION
- Simple reflex (pressure receptors activated when food is in the mouth)
- Conditioned reflex (think about food)
What are 4 functions of the oral cavity?
- Ingestion
- Mastication
- Lubrication
- Limited digestion
What is ingestion function in the oral cavity?
and sensory analysis of material (before swallowing)
What is mastication function in the oral cavity?
(mechanical processing) – through actions of teeth, tongue, and palatal surfaces
Food in smaller pieces to aid the breakdown
What is lubrication function in the oral cavity?
mixing with mucus and salivary gland secretions
From mouth to stomach (while muscles are present)
What is limited digestion function in the oral cavity?
of carbohydrates (Complex carbs) & lipids
*Phonation & ventilation
What happens in the position of the oropharyngeal structures at rest
Swallowing reflex
- Bolus (masticated food with saliva)
- Swallowing starts
What happens in the oral part or oropharyngeal stage of swallowing
Brainstem starts the swallowing process
What happens in the pharyngeal part or oropharyngeal stage?
- Glottis closes to make sure that food doesn’t pass down the trachea into the lungs (airway path is wrong)
- Want the food to go down the epiglottis This swallowing reflex is involuntary- controlled by:
- Receptors at the back of tongue, and mouth activate central centres in the brainstem
- Only voluntary action is the “swallowing” at the beginning
What happens at the beginning of the oesophageal stage of swallowing?
- Once food has passed this tract –> everything goes back to normal People who are paralysed or have problems at the level of their brainstem
- Can have difficulty eating (must be feed through a nasal tube)
- No longer have central centres to help with the swallowing process
What happens at the completion of oesophageal stage?
- Receptors activate muscularis externa which help to push the bolus down the osophagus (peristalsis)
- Receptors also open up the gastro-osophageal sphincter and bolus passes into the stomach
What are the 2 stages of swallowing?
- Oral-pharyngeal
- Oesophageal
What are 8 steps that occur in the oral-pharyngeal stage?
- Bolus is voluntarily pressed by the tongue up against roof of mouth and backwards towards the pharynx
- In response to activation of pharyngeal pressure receptors, swallowing centre in the medulla initiates reflexes that prevent food entry into respiratory passages
- Uvula contracts
- Laryngeal muscles contract which closes the glottis at the top of the trachea
- Epiglottis swings down and covers the closed glottis
- Respiration is temporarily inhibited
- As the upper pharyngeal sphincter is contracted, contractions drive the bolus into the oesophagus
- Oral-pharyngeal stage is done and breathing resumes
What are 3 steps that occur in the oesophageal stage?
- Primary wave of peristalsis (initiated by primary swallowing centre) pushes bolus down through the oesophagus
- If the bolus is sticky and adheres to the oesophagus, secondary peristalsis waves triggered by the intrinsic plexus at the point of distention completely clear the oesophageal lumen to finish the swallow
- As the bolus travels through the oesophagus, the lower oesophageal sphincter relaxes, allowing food to enter the stomach
What are the 11 stages of the swallowing reflex?
Oral-pharyngeal stage
- Bolus is voluntarily pressed by the tongue up against roof of mouth and backwards towards the pharynx
- In response to activation of pharyngeal pressure receptors, swallowing centre in the medulla initiates reflexes that prevent food entry into respiratory passages
- Uvula contracts
- Laryngeal muscles contract which closes the glottis at the top of the trachea
- Epiglottis swings down and covers the closed glottis
- Respiration is temporarily inhibited
- As the upper pharyngeal sphincter is contracted, contractions drive the bolus into the oesophagus
- Oral-pharyngeal stage is done and breathing resumes
Oesophageal stage
- Primary wave of peristalsis (initiated by primary swallowing centre) pushes bolus down through the oesophagus
- If the bolus is sticky and adheres to the oesophagus, secondary peristalsis waves triggered by the intrinsic plexus at the point of distention completely clear the oesophageal lumen to finish the swallow
- As the bolus travels through the oesophagus, the lower oesophageal sphincter relaxes, allowing food to enter the stomach
What is the stomach?
a muscular chamber, inferior to the diaphragm.
for mechanical digestion
What are the 3 functional compartments of the stomach?
- Fundus
- Body
- Antrum
What is the fundus of the stomach?
dome-shaped region beneath the diaphragm
What is the body of the stomach?
(oxyntic mucosa) – midportion of the stomach
- many gastric glands
- which produce the gastric juices
What is the antrum of the stomach?
the lower part – terminates at the pyloric sphincter (continues into the duodenum) Area where food is “stored”/ “left” before passed into duodenum
Different areas/compartments of the stomach are activated at ______ stages of the digestion
different
What are the 5 functions of the stomach?
- Stores ingested food and begins some digestion
- Secretes hydrochloric acid (HCl) (Gastric juices) and enzymes that begin protein digestion.
- Produces the intrinsic factor
- 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 People with gastric problems shouldn’t take aspirin as it attacks the muscosa and gets absorbed at the level as well
What does the stomach store?
ingested food and begins some digestion
What does the stomach secrete?
hydrochloric acid (HCl) and enzymes that begin protein digestion. – Produces the intrinsic factor
How does the stomach mix?
the food bolus and produces a creamy paste (chyme) mixture
How does the stomach digest?
– Mechanical break up of food particles - liquefies the food – Chemical digestion
What does the stomach absorb?
water, ions, alcohol and aspirin
Both processes (emptying and mixing) regulated by receptors and plexus within the stomach wall and the 2 sphincters –> can senses the ______ of the food in the stomach/ These 2 processes determine how long the food takes to be digested (depending on what type of food it is eg. soup or christmas pudding)
consistency
What is gastric emptying?
Peristalsis-like contraction which starts from fundus and goes until antrum
Stomach contracts in a way that pushes some (digested) food out into the duodenum
A way for the stomach to know how the second stage of the GIT tract has started
Fundus and body - Has chyme
Antrum- Somewhat digested chyme which is ready to go into the intestines
What is gastric mixing?
When the contractions push some of the digested food (liquic- chyme) into the duodenum
At the same time, the muscles at the sphincter are going to close and the liquid (chyme) comes back up and can be mixed together
This process is repeated until no more liquid is in the stomach and has all been passed into the intestines
Eg. liquid in a plastic bag –> trying to squeeze it –> liquid will go in and out and backwards and forwards
