Flashcards in Digestive System 1 Deck (85):
What is the digestive tract also called?
Where does the digestive tract extend to and from?
Extends from the mouth to the anus.
What is the digestive tract composed of (when simplified to one component)
A muscular tube.
What can be said about the muscular tube of the digestive tract?
It is composed of internal and apical surfaces. The apical surfaces are exposed to the external environment.
The function of the digestive system involves supplying the body with what main three components?
What is the supply of nutrients in the digestive system dependent on?
The food ingested.
What does the gastrointestinal tract optimise conditions for?
Digestion and Absorption.
In the digestive system, what is ingested food broken down into?
Substrates available for cells.
What are the six main functions of the digestive system?
Describe ingestion in the digestive system.
Material enters digestive tract via mouth
Describe mechanical processing in the digestive system.
Makes ingested material easier to propel along tract
Increases surface area to allow easier breakdown
Describe digestion in the digestive system.
Chemical breakdown of food for absorption
Large molecules (e.g. starch) broken into down small molecules (e.g. absorbable sugars)
Describe secretion in the digestive system.
Release of water, acids, enzymes, buffers, salts
Describe absorption in the digestive system.
Movement of substrates, electrolytes, vitamins and water across epithelium into interstitial fluid.
Describe excretion in the digestive system.
Removal of waste products from body
What is the end result of the functions of the digestive system?
The body is supplied with nutrients, electrolytes and water; and waste is removed
What are digestive organs?
Components that make up the digestive tract.
Name 6 digestive organs.
Oral Cavity (Mouth)
What are the major functions of the oral cavity/mouth?
Ingestion, mechanical processing with accessory organs (teeth and tongue), moistening, mixing with salivary secretions.
What are the major functions of the pharynx?
Muscular propulsion of materials into the oesophagus.
What are the major functions of the oesophagus?
Transport of materials to the stomach.
What are the major functions of the stomach?
Chemical breakdown of materials by acid and enzymes; mechanical processing through muscular contractions.
What are the major functions of the small intestine?
Enzymatic digestion and absorption of water, organic substrates, vitamins, and ions.
What are the major functions of the large intestine?
Dehydration and compaction of indigestible materials in preparation for elimination.
What is the function of accessory organs?
To contribute to the function of the digestive tract.
Name 7 accessory organs.
What are the major functions of the teeth?
Mechanical processing by chewing (mastication)
What are the major functions of the tongue?
Assists mechanical processing with teeth
What are the major functions of the salivary glands?
Secretion of lubricating fluid containing enzymes that break down carbohydrates.
What are the major functions of the liver?
Secretion of bile, storage of nutrients, many other vital functions.
What are the major functions of the gall bladder?
Storage and concentration of bile.
What are the major functions of the pancreas?
Exocrine cells secrete buffers and digestive enzymes; endocrine cells secrete hormones.
What is bile important for?
What is Serous membrane composed of?
What is between the sheets of serous membrane?
What is the function of serous membrane?
Stabilisation and attachment of digestive organs to the peritoneal cavity
Stops digestive organs from entangling
Is histological organisation the same for all organs?
Describe the histological organisation of organs.
4 Layers: Mucosa, submucosa, muscularis externa, serosa.
Describe the mucosa layer.
Contains mucous membrane
Participates in secretion and absorption.
Describe the submucosa layer
Binds to the muscularis externa
Dense irregular connective tissue
Surrounds muscularis mucosae
Large blood and lymphatic vessels
May contain exocrine glands
Secrete buffers and enzymes into digestive tract
Describe the muscularis externa layer
Smooth muscle - contraction.
Describe the serosa layer
Is a membrane that allows attachment
A lining of serous membrane covering muscularis externa
Attaches to the mesentery
What is the inner lining of the mucosa layer composed of?
What is the mucous membrane of the mucosa layer made of?
Describe the digestive epithelium of the mucosa layer.
Simple columnar or stratified squamous enteroendocrine cells
Moistened by glandular secretions
Longitudinal folds, circular folds and villi to increase surface area.
Describe the lamina propria of the mucosa layer.
Areolar tissue containing:
-Blood and Lymphatic vessels
-Sensory nerve endings
Made of smooth muscle cells (muscularis mucosae)
What type of cells are found in digestive epithelium?
Where are stratified squamous cells found in digestive epithelium?
Where are simple columnar cells found in digestive epithelium?
In what type of digestive cells are goblet (mucous) cells found in?
What does digestive epithelium protect against?
Digestive acids and enzymes
Mechanical stresses, such as abrasion
Name 4 specialised epithelial cells found in digestive epithelium.
Describe the stem cells of digestive epithelium.
Constant cell renewal – digestive epithelial cells are renewed every 3 days on average.
Describe the enteroendocrine cells of digestive epithelium.
Describe the goblet cells of digestive epithelium.
Describe the Paneth's cells of digestive epithelium.
Secrete antimicrobial peptides
Aid in protecting microbes
What is the submucosal plexus also called?
Describe the submucosal plexus.
Enzymes that help to "switch the system on or off"
Innervates the mucosa and submucosa
Sensory neurons, ganglionic neurons & postganglionic neurons
What is the muscularis externa made of?
Smooth muscle cells
Arranged in an inner circular layer and outer longitudinal layer.
What is the muscularis externa involved in?
Mechanical processing and the movement of materials along the digestive tract.
What are the movements of the muscularis externa coordinated by?
The enteric nervous system.
What are the movements of the muscularis externa primarily innervated by?
The parasympathetic division of the autonomic nervous system.
What does digestive movement involve?
The contraction and relaxation of smooth muscle.
Describe pacesetter cells
Undergo spontaneous depolarisation
Trigger waves of contraction (depolarisation) that spread throughout the entire muscular sheet
Located in the muscularis mucosae and muscularis externa
What is vital for movement of materials along the digestive tract?
What is the role of the peristalsis?
To move food/material along the digestive tract.
How does the peristalsis move food/material along the digestive tract?
Waves of muscular contraction:
-Circular muscles – push forward
-Longitudinal muscles – shorten
This propels bolus forward
What is segmentation also called?
What is segmentation?
Cycles of contraction
-Churn and fragment bolus
-Mix with intestinal secretions (e.g. duodenum)
Why does the digestive tract need to be regulated?
The rate of secretion/absorption must be regulated so the process is effective
What receptors are involved in the digestive system?
Chemoreceptors, Osmoreceptors, Stretch receptors, External (Sight, Smell)
What are the two main components involved with the regulation of the digestive tract?
Describe processing/control centres.
Nerves of the:
-Enteric nervous system( part of Peripheral Nervous System, housed within the digestive tract, local regulation)
-Autonomic Nervous System (sympathetic and parasympathetic)
Hormones (endocrine system) such as Gastrin, GIP, CCK, secretin, VIP
What is the role of the large intestine?
To absorb the final nutrients and secrete the final waste products.
Why is it important to have a balanced diet?
To ensure we have the correct amino acids to make our cells regulate properly
What are carbohydrates broken down into?
What do acids help to do in the digestive system?
Break down proteins.
What is the key process in the digestive system and why?
Absorption, because all in all, the important thing is what is going into our body.
What part of the body is the site of the first major chemical digestion?
What protects the lining of our organs from acid in the digestive system?
What is the mysentery?
A serous membrane that holds all of our organs together in one place.
What is the innermost layer of histological organs?
What do the stratified squamous epithelium of the digestive system protect against?
What do goblet cells do?
Secrete mucous onto the surface of epithelium to lubricate it.