Week 3 - The Digestive System Flashcards
What are the 7 functions of the digestive system?
- Ingestion - taking into mouth
- Secretion - release of water et al into GI
- Mixing - churning and movement of food through GI
- Digestion - mechanical/ chemical breakdown
- Absorption - passage of digested products from GI into blood and lymph
- Defecation
What are the organs of the alimentary canal?
- Mouth - allows for chemical and mechanical breakdown of food
saliva - 99.5% water, 0.5% solutes
lubricates, dissolves and begins chemical breakdown of food
glands contained in mucous membrane
3 major salivary glands - Pharynx - transfers food from mouth to oesophagus
- Oesophogas - secretes mucous and transports food into the stomach. Does not produce enzymes/ carry on absorption
- Stomach - mixing chamber and holding reservoir - connects duodenum to oesophagus
- Small intestine - digestion and absorption of nutrients - duodenum, jejunum, ilieum
- Large intestine - absorption of water and electrolytes, production of certain vitamins (K), formation and expulsion of faeces - colons rectum and anus
What does the pancreas do?
creates pancreatic juice, which includes enzymes used in digestion
What 9 things does the liver do?
- secreting bile (needed for absorption of fats)
- carbohydrate metabolism
- lipid metabolism
- protein metabolism
- detoxification
- excretion of bilirubin
- storage of vitamins and minerals
- Phagocytosis aged RBC and WBC
- activation of Vit D
What does the gall bladder do?
Stores bile
What are the 4 layers of the GI tract?
- Mucosa - inner lining of the GI
- Submucosa - areolar connective tissue that binds the mucosa to the muscularis
- Muscularis
mouth, pharynxc, parts of oesophogas, external anal sphincter - skeletal muscle
rest - smooth muscle - involuntary contracts help break down food and propel it along - Serosa - portions of the GI tract that are suspended in the abdo cavity have a superficial layer called serosa
Describe the tongue
- Skeletal muscle covered with mucous membrane
- Made up of
Extrinsic muscles - move tongue side to side and in and out
Intrinisic - alter shape and size for speech and swallowing
Covered in papillae (contain taste buds)
What is the purpose of salivation?
Food molecules begin to dissolve in water in saliva
important ∵ enzymes can only react with food in a liquid
These enzymes are
* salivary amylase - initiates the breakdown of starch
* lingual lipase - becomes activated in the acidic environment of the stomach and starts to work after food is swallowed. helps break down fats and oils
What are the different types of teeth and what are they used for?
- Incisors closest to midline, chisel shaped for cutting food
- Canines - pointed surface for tearing and shredding food
- 1st and 2nd pre molars - chewing
- 1st 2nd and 3rd permanent molars - chewing
Describe the gross anatomy of the stomach
Cardia surrounds the opening of the oesophagus into the stomach
Pylorus (1 of 4 regions) joins to the duodenum via a smooth muscle called the pyloric sphincter
Name the cells involved in the production of gastric juices and what they do
- Parietal cells → hydrogen ions H+ & chloride ions (Cl-) → hydrochloric acid
also provide carbonic anhydrase which create carbonic acid (H2CO3) from water (H2O) and CO2 help makie blood & urine more alkaline - Chief cells secrete Pepsin which helps break down protein chains of amino acids
- note it is first secreted as pepsinogen, which converts to pepsin when it comes into contact with H2CO3
- Epilitheial cells are impermeable to most materials so only a small amount of nutrients are absorbed via mucous cells
What enzymes are used in digestion and what do they work on?
- Protease digests proteins into amino acids
- Amylase digests carbohydrates into simple sugars
- and lipase breaks down lipids into fatty acids.
What are the end products of protein, fat, and carbohydrate digestion?
carbohydrates → sugars - glucose
proteins → amino acids
and fats → fatty acids and glycerol
How are foodstuffs broken down and absorbed in the small intestine?
- Mechanical - The two types of movements of the small intestine
Segmentations are localised, mixing contractions that mix chyme with the digestive juices and bring the particles of food into contact with the mucosa for absorption; they do not push the intestinal contents along the tract.
migrating motility complex (MMC) - After most of a meal has been absorbed, segmentation stops and peristalsis begins. begins in the lower portion of the stomach and pushes chyme forward along a short stretch of small intestine before dying out. - Chemical
chyme entering the small intestine from the stomach contains partially digested carbohydrates, proteins, and lipids.
The completion of the digestion of carbohydrates, proteins, and lipids is a collective effort of pancreatic juice, bile, and intestinal juice in the small intestine. - Absorption
Carbs absorbed as monosaccharides (facilitated diffusion or active transport)
most proteins as amino acids (active transport)
dietary lipids via simple diffusion
What are the symptoms of and treatment for various homeostatic imbalances of the digestive system?
- Dental caries or tooth decay - brush teeth and floss
- Periodontal disease incl. pyorrhea (bleeding of gums) - caused by poor oral hygeine
- Peptic ulcer disease - where GI exposed to acidic gastri juices. Can cause bleeding and anemia. caused by helicobacter pylori; NSAIDS, hypersecretion of HCl. Avoid smoking, caffeine, alcohol and NSAIDs. H. pylori - antibitiotics. HCl H2 blockers
- Diverticular disease - saclike pouches on wall of colon occur where muscularis has weakened and amy become inflamed. P. constipation, ↑ rate of defecation, fever, vomiting △ to high fibre diet
- Colorectal cancer - genetics, alcohol, animal fat. Diarrhoea, constipation, cramping, abdo P, rectal bleeding
- Hepatitis - inflammation of the liver caused by viruses, drugs and chemicals
