7. DIGESTIVE SYSTEM I Flashcards
Structure and functions of the digestive system. The key enzymes and hormones involved in digestion. The types of dietary carbohydrates, fats/oils and proteins.
Expand on “You are what you eat”
You are what you digest
You are what you absorb
You are what you don’t excrete
Name 5 functions of saliva
DIGESTION - amylase LUBRICATION CLEANSING - of oral cavity & teeth DEFENSE - presence of IgA & lysosomes TASTE BUFFER - for acidic foods (bicarbonate) WASTE REMOVAL - eliminates urea/uric acid
What is the pH inside the stomach?
2 to 3
What prevents the contents of the stomach from refluxing into the oesophagus?
The lower oesophageal sphincter (aka the cardiac sphincter)
What are the six processes of digestion
1. Ingestion 2. Secretion - digestive juices 3. Mixing & propulsion - contraction, relaxation 4. Digestion - mechanical & chemical 5. Absorption - into blood & lymph 6. Elimination
What is the basic four-layer arrangement of tissues in the GIT?
- Mucosa
- Submucosa
- Muscularis Externa
- Serosa (peritoneum)
What is the GALT?
Mucosal-Associated Lymphoid tissue specifically found in the gut (hence Gut-Associated Lymphoid Tissue) which makes up 25% of intestinal mucosal mass and contains 70% of the body’s immune cells. It is a very important part of the body’s first line of defense.
What three layers comprises the Mucosa of the GIT?
- Epithelium
- Lamina Propria
- Muscularis Mucosa
What is MALT and where in the body can it be found?
Mucosal-Associated Lymphoid tissue which is a collection of immune cells and can be found in the Lamina Propria layer of the tonsils, oesophagus, small intestine, appendix, large intestine.
True or false: The peritoneum is the smallest serous membrane in the body
False
The peritoneum is supplied with many blood and ______ vessels and consists of a visceral and __________ layer. It provides a physical barrier to prevent local spread of __________.
lymph
parietal
infection
Define Ascites and name a possible cause
Ascites is accumulation of fluid in the peritoneal cavity and could be caused by liver cirrhosis, heart failure, GIT malignancies, pancreatitis.
Define Peretonitis and name two probable causes.
Peretonitis is an acute inflammation of the peritoneum and could be caused by bacterial infection, ruptured appendix, friction or surgical wounds.
What is the greater omentum?
It is the largest fold of the peritoneum which drapes over the transverse colon and small intestine like an apron. It stores adipose tissue (fat) and has many lymph nodes containing macrophages and plasma cells.
The lesser omentum is a pathway for _______ ________ entering the liver. It contains the hepatic _______ ____, common _______ artery, common ____ duct and lymph nodes.
blood vessels
portal vein
hepatic
bile
What is known as the ‘brain of the gut’?
The Enteric Nervous System
True or False: The Enteric Nervous System has only slightly less neurons than the spinal cord.
False. It has 100 million neurons - more than the spinal cord.
What regulatory effect does the Sympathetic Nervous system have on the Enteric Nervous System?
It decreases muscular activity (peristalsis) and glandular secretions
What are the two networks of the Enteric Nervous System called, where are they located and what is their function.
- Myenteric Plexus: sympathetic and parasympathetic nerve fibres located between the circular and longitudinal muscles of the muscularis. It controls the strength and frequency of muscle contraction (gut motility)
- Submucosal Plexus: The same two types of nerve fibres, situated within the submucosa which controls digestive secretions and detects sensory information.
Name three accessory organs of the digestive system.
Salivary glands, pancreas, liver, gall bladder and biliary tract.
What percentage of the body’s immune system resides in the gut?
70%
What is the network of sympathetic and parasympathetic nerve fibres in the submucosa called and what does it control?
The submucosal plexus controls digestive secretions and detects sensory information.
What three types of neurons can be found in the enteric nervous system?
- Motor neurons: in the myenteric plexus controls peristalsis and in the submucosal plexus controls secretions.
- Sensory neurons: receive information about the mucosal environment (chemoreceptors and stretch receptors).
- Interneurons: connects the two plexuses.
Which parts of the digestive system contain skeletal muscle?
The mouth, pharynx, upper oesophagus and anal sphincter.