Basic structure of the Digestive System Flashcards
what is the largest componenet of the digestibe system ?
The gastrointenstinal tract (GIT)
journey of the gastrointestinal tract
- Mouth
- Oesophagus
- Stomach
- Small intestine
- Large intedtine
- Caecum
- Rectum
- Anus
The Upper GIT consists of
- The mouth
- Oesophagus
- Stomach
- The small intestine- (Duodenum, jejunum + ilium)
The Upper GIT consists of
- The mouth
- Oesophagus
- Stomach
- The small intestine- (Duodenum, jejunum + ilium)
The lower GIT consists of
- Caecum (start of large intestine- colon)
- Colon
- Rectum (end of large intestine)
- Anus
The lower GIT consists of
- Caecum (start of large intestine- colon)
- Colon
- Rectum (end of large intestine)
- Anus
general histological theme of GIT:
- Mucosa
- Submucosa
- Muscularis Externa
- Adventita/Serosa
Mucosa
Innermost layer, contains the epithelial cells important in lubrication and absorption
Submucosa
This layer contains the support network of blood vessels and immune cells to keep the mucosa healthy in addition to attaching it to the muscular layers below
Muscularis Externa
The muscles necessary for peristalsis are contained in this layer which propel the food through the GI tract.
Submucosa/Serosa
- The outermost layer which allows the GIT to interact with other tissues around it
- Consists of several layers of connective tissue
what kind of tissue is serosa adn what organs does it include ?
Smooth tissue – All the GIT apart from the oesophagus
what kind of tissue is adventitia and what organs does it include ?
Adventitia- Fibrous connective – Oesophagus.
what are the 2 types of digestion ?
- Mechanical
- Chemical
what are the 2 types of digestion ?
- Mechanical
- Chemical
example of mechnical digestion
- Mastication
- Alimentary muscular contractions
examples of chemicla digestion
- Stomach
* Enzymes
* HCl - Duodenum
* Enzymes
* Bile
examples of Chemical-Microbial
- Bacteria produce enzymes capable of chemical digestion
What does the GIT do ?
- Collecting the nutrients we need as a raw material (food)
- Breaking food down (digestion)
- Getting rid of the components surplus to requirements or that we can’t digest (excretion).
how does the mouth have mechanical and chemical digestion ?
- Mechnical
chewing/mastication
- Chemical
amylase breaking down starch
how does the mouth have mechanical and chemical digestion ?
- Mechnical
chewing/mastication
- Chemical
amylase breaking down starch
what enzyme is produced by salivary glands around oral activity
α-amylase
what enzyme is produced by salivary glands around oral activity
α-amylase
what does Carbohydrases do ?
Hydrolyse Carbohydrates (Sugars)
what do Proteases/Peptidases do ?
Hydrolyse Proteins
what does Lipases do ?
Hydrolyse Lipids (Fats)
what does Nucleases do ?
Hydrolyse Nucleic Acids (DNA/RNA)
Zymogens:
- Enzymes that are synthesized as inactive precursors (pro-inactive forms) as producing a digestive enzyme inside the cell would lead to autolysis (self digestion)
- activated by cleavage of one or a few specific peptide bonds by components of the extracellular environment.
what does the oesophagus do ?
carries food from the mouth to the stomach
how is the oesophagus adapted for its function ?
- The mucosa of the oesophagus is a stratified squamous epithelium, the remainder of the GI tract is simple columnar
- The outermost layer of the oesophagus is an adventitia, the remainder of the GI tract is a serosa
what 2 muscles do peristalsis contain ?
These two muscle sheets in opposing direction work together to maximize the efficiency of peristalsis
where does the oesophagus terminate ?
In the stomach
GIT historical trend of the stomach
- The mucosa of the stomach is a columnar epithelium, and forms ‘glands’ which house a range of important cell types
- The muscular layer of the stomach wall contains three layers of muscle (as opposed to two), this ensures efficient mixing , churning and emptying
Functions of the stomach:
- the stomach contains an important protease called pepsin
Disruption; the acidic environment of the stomach also helps break down some chemical bonds in food- pH- 1.5 - 4
Functions of the stomach:
- the stomach contains an important protease called pepsin
Disruption; the acidic environment of the stomach also helps break down some chemical bonds in food- pH- 1.5 - 4
where is pepsin secreted ?
Pepsin is secreted as a zymogen called pepsinogen, which is activated by the acidic environment of the stomach lumen
ephitelial cells in the stomach produce….
pepsinogen
The passage of chyme from the stomach to the first stage of the intestine is controlled by…………
the pyloric spincter
The passage of chyme from the stomach to the first stage of the intestine is controlled by…………
the pyloric spincter
what does the chyme contain ?
gastric juices + partially digested food
what are the 3 distinct areas of the small intestine?
- Duodenum
- Jejunum
- Ileum
where do the liver and gall bladder exert their role ?
in the duodenum
what does the liver produce ?
Bile
the functions of Bile
- Bile emulsifies fats, breaking them down into smaller droplets which increases the surface area available for enzymes to act upon
- Nutralises acid
the functions of Bile
- Bile emulsifies fats, breaking them down into smaller droplets which increases the surface area available for enzymes to act upon
- Nutralises acid
what is the pancreas and what is its function ?
- The pancreas is the one of the body’s main sites of enzyme synthesis, it produces a large component of the enzymes required for digestion
how does the pancreas have both endocrine and exocrine functions ?
- Acts on distant cells via the circulation, e.g. secretion of insulin and glucagon into the blood
- Acts via ducts or channels rather than blood, e.g. secretion of digestive enzymes into the duodenum
what type of enzyme is Trypsin and where is it important ?
- A protease
- in the duodenum (secreted as trypsinogen)
what type of enzyme is Trypsin and where is it important ?
- A protease
- in the duodenum (secreted as trypsinogen)
An enzyme produced by intestinal epithelial cells called……………………….activates trypsin
enteropeptidase
An enzyme produced by intestinal epithelial cells called……………………….activates trypsin
enteropeptidase
what are lacterals ?
- Lacteals are capillaries of the lymphatic system found on villi
- Lipids are transported away from the GIT by the lacteals
Functions of the colon/large intestine
- **Site fo water absorption ** and electrolytes from intestinal fluid
- Compaction of intestinal contents into feces
- Absorption of important vitamins produced by bacteria
- Storage of fecal material prior to defecation
Functions of the colon/large intestine
- **Site fo water absorption ** and electrolytes from intestinal fluid
- Compaction of intestinal contents into feces
- Absorption of important vitamins produced by bacteria
- Storage of fecal material prior to defecation
