Digestive System Flashcards
What is digestion?
The process where large, complex food substances are broken down into small, simple, soluble substances that can be easily absorbed
What is the function of the GI tract (digestive tract)?
Hollow tube
Approx 10m long
Travels length of body starting at the mouth, passing through the thorax, abdomen, pelvis and ending at the anus
What is the function of the accessory organs?
Contribute to digestive process
Passes various secretions into digestive tract
Generally situated outside DT- secretions pass through ducts to enter main tract
Name examples of organs of the DT…
Stomach Mouth Oesophagus Small/large intestine Rectum Anus
Name examples of accessory organs…
Liver
Pancreas
Gall bladder
Salivary glands
What allows for ingestion to take place?
Mouth- food is taken into the oral cavity
What enables propulsion to take place?
Movement by Peristalsis
Includes oesophagus, stomach, small/large intestine
Define digestion…
Food is broken down mechanically and chemically by enzymes
What enables digestion to take place?
Mouth- tongue and teeth (mechanical) and saliva (chemical)
Stomach
What allows absorption to take place?
Small intestine
What is absorption?
The movement of digested molecules across the GI tract into the blood
What is assimilation?
Movement of molecules from the blood to the cells
Then become a part of body tissues
What enables elimination to take place?
Rectum and anus- defecation
What is the function of the mouth?
Contains teeth, tongue, and salivary glands
Allow food to begin the digestive process- breaking down food to smaller pieces, mixes with saliva and manipulates it so it can be swallowed
What enzyme is found in saliva?
Salivary Amylase- initiates starch digestion
What are the functions of saliva?
1) antibacterial effect eg enzyme lysozyme (destroys bacteria)
2) washes away food that may be a source of bacteria
3) acting as buffer- contains bicarbonate (neutralises acids, preventing dental issues)
How is food swallowed?
Bolus (ball of food) is formed
Directed by tongue around the mouth until it can be swallowed
What is swallowing?
Series of movements transporting food from the mouth to the pharynx into the oesophagus
How is the pharynx involved in respiration?
Air enters pharynx when heading into the lungs while food passes through here and enters the stomach
What structure prevents food from entering the trachea?
Epiglottis
What are the 4 layers of the wall of the digestive tract?
1) mucosa
2) submucosa
3) muscularis
4) serosa
What is the mucosa?
Innermost layer of DT
Largely made of epithelial tissue
Ingested food is in direct contact with this layer- lot of wear and tear
DT- folded to provide larger SA for digestion/absorption
(In intestine) forms finger like projections-villi
What is the function of the mucosa?
Specialised cells scattered throughout- secretes mucus, lubricating/protecting gut lining
Also cells secreting chemicals needed for digestion
Thin epithelial layer provides route for absorption
What is sub-mucosa?
Layer of loose connective tissue
Contains nerves, blood and lymph vessels
What is the function of the sub-mucosa?
Blood supply enables nourishment of tissues + transports products of digestion
Primarily involved in absorption of fat
(Lymph vessels- involved in immune system)
What is the muscularis?
3rd layer of DT
Contains 2 layers of smooth muscle- circular and longitudinal with nerve tissue (plexuses) between them
What is the function of the muscularis?
Coordinated contraction of it- rhythmic peristalsis
Includes skeletal muscle (in mouth, pharynx and upper part of oesophagus) involved in voluntary swallowing
What is the serosa?
Outer coat
Contains loose fibrous tissue and nerve, blood and lymph vessels
What is the function of serosa?
Protection (of outer layer)
What is the oesophagus?
Straight, muscular tube connecting pharynx to stomach
Muscular wall containing mucous glands
What is the function of the oesophagus?
Mucous glands in walls secrete mucus, keeping lining moist/lubricated- allows bolus to slide down smoothly
Longitudinal/circular muscles lining walls contract-move bolus along- Peristalsis
What prevents food going back into the oesophagus?
Oesophagus has upward curve
Cardiac sphincter/lower oesophageal sphincter at stomach entrance- opens allowing bolus to enter and closes preventing reflux
What is the stomach?
Large, j-shaped bag
Lies just under diaphragm in upper left side it abdominal cavity
What are the 3 parts of the stomach?
1) fundus- lies near cardiac sphincter
2) body- middle part
3) antrum- lower part containing pyloric sphincter
What are rugae?
Folds in the stomach (mucosa/sub-mucosa) - flatten out and allow for the stomach to expand
What are the specialised cells in the stomach?
1) goblet cells- produce mucus to coat/protect stomach lining
2) parietal cells- produce HCl and intrinsic factor
3) G cells- produce hormone gastric, regulating gastric secretions
4) chief cells- produce pepsinogen (inactive precursor to pepsin) chemically breaking down protein molecules
What are the 3 sections of the small intestine?
1) duodenum
2) jejunum
3) ileum
What is the function of the duodenum?
Short c-shaped tube
Contains glands- secrete an alkaline mucus used to neutralise acidic chyme produced in the stomach
Region where large ducts, liver + pancreas connect
What is the major role of the small intestine?
Absorb nutrients that have been broken down from food
Absorbed via active transport and diffusion
What adaptations does the small intestine have for nutrient absorption?
1) large SA- folds of intestinal wall, villi and microvilli
2) network of capillaries- short distance for nutrients to travel into bloodstream, aiding absorption
What are the functions of the large intestine?
1) absorption of water/electrolytes
2) storage/elimination of faeces
3) bacteria digest some polysaccharides
4) bacteria produce vitamins (K+B)
5) appendix has immune function
What is the function of the liver?
Makes bile- emulsified fat/aids fat absorption
Bile- pH 8
What is the function of the gall bladder?
Stores bile- secretion into the duodenum
What is the function of the pancreas?
Makes pancreatic juice containing digestive enzymes/bicarbonate ions
pH 8
