Digestion Flashcards
What is digestion
The breaking down of ingested food into useable smaller nutrient molecules that can enter the vascular or lymphatic system so body can make energy out of it
How is digestion achieved
Mainly through GI tract
What does the digestive system consist of
- Gastrointestinal tract ( one long tube from mouth to anus which breaks down food and absorbs it )
- The accessory structures (digestive organs)- not part of the tract - (e.g. teeth, tongue, liver, pancreas that help by mechanical or chemical means - things which we can absorb into the vascular or lymphatic system)
What is our food composed off?
The major nutrients:
Vitamins- act as co-enzymes - make enzymes work in body - they can be either fat soluble A,D,E,K) OR water soluble. (B AND C)
Minerals/trace elements- body requirements of 7 minerals- calcium, phosphorous, potassium, sulphur, sodium, chloride, magnesium) and trace amounts of. about a dozen others. They serve other functions such as CA: bone, Fe- haemoglobin, Ca/Na/K- nerve/muscle)
What are the major nutrients
- Carbohydrates - mono-,di-,&poly-saccharides) - short and long chain sugar molecules
- Protein - amino acid chains
- Fats (glycerol and fatty acids)
What are the 6 processes of digestion consist of?
Ingestion- take food in Propulsion- propel food through GI tract Mechanical Breakdown-in the stomach and teeth (accessory structure) Digestion- chemically Absorption- into vascular system Defecation- get rid off it
How do the processes of digestion happen
At the same time, together. Not one after the other
What are the 4 layers of a general GI tract
Tube consisting of 4 layers:
- Inner layer known as mucosa - inside
- Under sub mucosa - outside
- Layer of muscle
- Outer serosa - tough outer protective connective tissue
Where does GI tract start and end and what is in middle
Starts at mouth and ends at anus ( comes out as faeces )
Stomach and intestine in middle
What does mucosa contain
- Mucous secreting goblet cells to protect and lubricate the passage of food and gut
- Cells secreting digestive enzymes and hormones (in the stomach and small intestine)
- Epithelial cells (simple columnar epithelium)
- Lamina propria
Properties of lamina propria
- Lies underneath the epithelium which is loose aerolar connective tissue
- Have lymphatic vessels of lymphatic system- protect body, protective lymphoid follicles.
What type of epithelium in mouth and anus
Stratified squamous epithelium, not simple
Function of mucous in GI tract
- Protect and lubricate the gut
- Stomach has HCL - don’t want that destroying GI tract
What is the submucosa?
- External to mucosa
- Made of loose aereolar connective tissue
- Contains lymphatic and blood vessels and abundant nerve supply
- elastic fibres/tissue .
Why is their elastic tissue/fibres in GI tract
Whole system has to be able to expand when food goes in and down
What is the muscularis layer of the GI tract made up of
Inner circular ( round ) and outer longitudinal layer along GI tract of smooth muscle innervated by ANS
What is function of muscle in GI tract
- Shove food along by the process of peristalsis.
- Food turned into a bolus (balls) and that is then pushed through GI tract by contraction of the muscle behind bolus and relaxation of muscle infront of bolus
What is surrounding the whole GI tract
Protective serosa
What is function of mouth
Responsible for ingestion
Structure of mouth
- Lined with thick stratified squamous epithelium - protection
- Has tongue which mixes the food with saliva, forming a bolus which is shoved along by peristalsis
- tongue contains taste buds
- teeth macerate the food (mastication- crush food)
- mouth is connected to a number of glands whose secretions form saliva - produce digestive enzymes and protective mucous
Why do we need teeth in mouth
Digest things chemically - smash into small things
Digestive enzymes cant act on big things so you need teeth to crush it down
What are the 3 salivary glands called and what do they do
-Parotid glands
-Submandiular gland
-Sublingual gland
produce saliva
What do these secretions of saliva serve to do
- dissolve the food so we can taste it
- help form the food into a bolus
- lubricate the mouth
- begin digestion of starch mostly and fats by producing the enzymes amylase ( digest starch ) and lipase ( digest fats)
What type of gland is salivary gland and what do they contain
Exocrine
Contain mucous and serous secreting cells
What is the main digestive enzyme in mouth
Amylase
Where does the food/fluid and air end up once gone through mouth?
- Back of throat- Pharynx- which can be divided into various regions
What is the Pharynx?
Back of throat where food/fluid and air leave via the mouth
What is role of epiglottis
Normally its open to allow air to pass down trachea
Opens and shut so food goes down to stomach and air down to lungs
What happens to epiglottis when swallowing
Closes thus lowering the diaphgram ensuring food and liquids do not enter the trachea but instead enter oesophagus
Dont want food down trachea as it could cause pneumonia and could die
What is the process when food and air goes in
Food in mouth Air in through nose Mix air taken in and food in the pharynx Need to seperate - food down to stomach and air down to lungs - cant get it other way = MIX AIR AND FOOD FIRST THEN SEPARATE