Digestive system Flashcards
Digestion
Digestion is the breakdown of large insoluble food molecules into small water-soluble food molecules so that they can be absorbed into the blood stream
Mechanical digestion
the physical breakdown of food particles into smaller pieces to increase the surface area.
Chemical digestion
Chemical digestion uses enzymes to break down large, complex molecules into smaller, simpler molecules. These smaller molecules are then small enough to be absorbed into the bloodstream.
4 Functions of digestion
Ingestion of food and water, Movement of food along Alimentary Canal (GI Tract), Absorption of digested food and water into blood and lymph, Elimination of material that’s not absorbed
Alimentary canal
the continuous tube that runs from the mouth to the anus. the lining of the canal is the surface through which nutrients are absorbed.
Mouth cavity
mechanical digestion by teeth, chemical digestion of starch by saliva
Salivary glands
three pairs of glands produce saliva, which dissolves food so it can be tasted. saliva contains mucus that lubricates the mouth and food and holds food in a bolus for swallowing. it also contains the enzyme salivary amylase, which begins starch digestion.
Liver
produces bile, which is stored and concentrated in the gall bladder
Gall bladder
stores bile and releases it into the small intestine, where the Bile salts act as emulsifying agents, breaking fat down into smaller droplets.
Duodenum
first part of small intestine, The absorption of vitamins, minerals, and other nutrients
large intestine
transverse, ascending, descending colon - Glandular cells in L intestine secrete mucus, the slow movement of materials allows water to be absorbed and contents to harden, Bacteria breaks down the remaining organic materials, which are then absorbed through the walls into the blood.
Caecum
pouch where the small intestine joins the large intestine
Appendix
plays a role in immunity and stores useful bacteria
Rectum
final part of large intestine in which feces are formed
Pharynx
back of mouth cavity, by moving upwards and backwards, the tongue pushes food into the pharynx for swallowing
Oesophagus
carries food from the mouth stomach, it passes through the diaphragm into the abdominal canal
Pyloric sphincter
band of circular muscle that regulates flow of material from the stomach to duodenum
Pancreas
produces pancreatic juice containing enzymes for digesting proteins, lipids and nucleic acids
Small intestines
its lining secretes intestinal juices contains enzymes, internal surface is lined with villi for the absorption of digested food.
Made up of:
1. Duodenum
2. Jejunum
2. Ileum
Anus and rectum
a muscle that can be voluntarily controlled, Peristalsis pushes left over material in L Intestine into Rectum, Walls of rectum stretch + trigger defecation, Controlled by anal sphincters.
Human Dentition
Mechanical Mastication (Chewing action of teeth)-
4 incisors: chisel shaped teeth for biting, cutting
2 canines: 1 on each side for tearing
4 premolars: 2 on each side
6 molars: 3 on each side, crushing + grinding food
Saliva (chemical)
Saliva secreted by salivary glands –mucus, digestive, enzymes, salivary amylase
Functions- Mucus lubricates mouth and food, Dissolves food so taste receptors are stimulated, Stickiness of mucus helps food hold together – bolus, Salivary amylase breaks down starch into glucose
Bolus Formation + Swallowing
Bolus is the term for food after it has been ingested, chewed and mixed with saliva in one’s mouth. The function of bolus is toprovide a more compact package of food that can be better swallowed.
Swallowing
Tongue pushes bolus down pharynx into oesophagus.
Epiglottis closes off trachea when swallowing.
Peristalsis
the involuntary constriction and relaxation of the muscle, creating wave-like movements that push the contents of the canal forward.
stomach (Mechanical Digestion)
Muscular contractions churn food and mixes with gastric Juice, converted to thick soupy liquid called Chyme, produces pepsin and rennin.
J shaped bag with mucosa folds in stomach called Rugae, Lined with a mucosa layer- Gastric Pit
Cardiac Sphincter
separates the oesophagus and stomach
Pepsin
type of protease, a stomach enzyme that serves to digest proteins found in ingested food, only works in acidic condition. eg amino acids and hydrophobic
Gastric Pit
contains cells, which secretes HCl (which kills bacteria
and help with food breakdown), mucus and gastric juices- moves from almost natural acidic organ to a high acidic organ.
Pyloric Sphincter
regulates the chyme entering into the Small intestine.
Segmentation
is to slosh the contents of the small intestine back and forth mixing its contents with the digestive juices.
Feaces
Feces contains water, undigested food material + remains of cells that have broken away from alimentary canal.
Elimination – Removal of indigestible material, bacteria and bile pigments from the body.
Constipation
If large Intestine movement slows and contents stay there for a while, leads to constipation. if too much water is absorbed, feces becomes harder drier, defecation becomes difficult + painful.
Diarrhea
Frequent watery feces due to irritation of S or L Intestine. Which increases peristalsis + material moves through too quick + water not absorbed - Bacterial/Viral infection. Ie food poisoning; Cholera can lead to severe diarrhea, dehydration then death.
Soluble fiber in the diet
Soluble fiber attracts water in the gut, slow digestion, prevent blood glucose surges after eating and reduce hunger. uncontrol of blood glucose = risk factors for diabetes, doubles the risk of developing heart disease.
Bowel cancer
Uncontrolled growth of cells in the wall of the large intestine. Research suggests L intestine cancer due to diet, high alcohol intake and smoking, Overweight and physical inactivity
Coeliac disease
Unable to tolerate a protein called gluten – If eat gluten, immune system destroys villi in small Intestine. villi absorption doesn’t happen therefore become malnourished no matter how much food is eaten.
Muscle cramps, joint pain, can be difficult to diagnose, Treatment: Gluten Free Diet.
Protease
an enzyme that spits or severs proteins, acts under any condition.
Mouth
salivary gland, neutral-slightly acidic, produces salivary amalyse, acts upon glycogen and starch, produces maltose.
