PP 1 Human Alimentary Canal/ Mechanical Digestion

Plus –Definitions for All of Digestion

Definitions

• Ingestion – taking in substances (food [eating] / drinking) into the body through the mouth.

• Digestion – breaking down large insoluble food molecules into small water soluble molecules using mechanical and chemical processes.

• Absorption – movement of digested food molecules through the wall of the intestines into the blood or lymph .

Definitions continued

Assimilation – movement of digested food molecules into the cells of the body where they are used – becoming part of cell.

Egestion – Passing out of food that has not been digested as faeces through anus

ENZYMES

ENZYMES

Ingestion

Digestion Absorption

Assimilation

Egestion

Alimentary canal = long tube that starts at the mouth and ends at the anus – the way foodtravels through the system.

Nasal Cavity

Appendix

IleumDuodenum

Trachea

AnusRectum

Large Intestine

Gall BladderPancreasStomach

Oesophagus

Mouth

Liver

Small intestine = Duodenum ->Ileum

Colon

Large Intestine =Colon -> Rectum

Abdomen = the area belowRibs and above Hip bone

Capillary absorb:• sugar / a. a. / vitamins / inorganic ions / water

Lacteal absorb:• fatty acids / glycerol

The Villi: Surface area is important•

Breaking food down

• 10 hours for food to pass through from the mouth

• Mechanical digestion = physical breaking up food by teeth (chewing) and stomach walls churning (Peristalsis).

• Chemical Digestion = Break down of food molecules via enzymes.

Regions of Alimentary Canal

Functions Relations to : ingestion/ Digestion/ Absorption/ Assimilation

Mouth(more on chewing/teeth structure/ fluoride for teeth)

Use of lips / teeth / tongue to break down food mechanically (Mastication = chewing).Taste buds decide chemically if safe to eat or not.

Ingestion

Salivary glands Water + Amylase (starch -> maltose) + Mucus (slippery substance that allows slide)

Digestion

Esophagus Takes food from mouth to stomach after swallowing. Ingestion

Stomach Gastric juices (HCl (pH 2) + pepsin – to break down protein) secreted & Mucus also secreted to protect the stomach from being digested itself (but if it does happen – the sore is called an Ulcer. Physical churning is called Peristalsis. *Vitamins are directly absorbed

Digestion

*Absorption

Regions of Alimentary Canal

Functions Relations to : ingestion/ Digestion/ Absorption/ Assimilation

SI :Duodenum Liver / Pancreatic juices mix here.* Contains Villi (finger like projections)

Digestion* Absorption

SI : Ileum Contains villi: (finishes digestion / absorption)/ increases surface area to seep up the rate of absorption) / thin walls so not must time / space for absorption.All large molecules broken down to their simplest parts (maltose -> glucose via maltase)

Absorption: sugar / a. a. / fatty acids / glycerol / vitamins / inorganic ions / water (into blood or lymph)

Pancreas Releases Pancreatic juices (enzymes) & flows into duodenum via pancreatic duct. Also contains Sodium hydrogen carbonate (helps neutralize acids) from stomach pH 2 -> pH 6.5. =. Avoids harm to small intestine.Enzymes = carbohydrase (amylase) & Protease (trypsin) & Lipase

Digestion

SI : Small Intestine / LI = Large Intestine

Regions of Alimentary Canal

Functions Relations to : ingestion/ Digestion/ Absorption/ Assimilation

liver Produces bile / store in gal bladderAfter absorption of molecules – all go to the liver via hipatic portal vein. Liver’s job ; to Sort out molecules:• Some molecules will be carried in blood to the cells that need them.• Some will be stored in liver•Some will be changed for storageEg. Glucose that is not used will be converted to glycogen (stored in liver). Long term stored glycogen will be converted to fat (stored in other areas eg. Abdomen).Eg. Amino acids will be used to make protein and then transported by blood to other parts of the body.Excess a. a. will be converted into urea and removed via urine.• Break down dangerous toxins (alcohol) •Liver disease = cirrhosis

Assimilation

Regions of Alimentary Canal

Functions Relations to : ingestion/ Digestion/ Absorption/ Assimilation

Gal Bladder Bile is stored here and released into the duodenum when food is there via the bile duct. Bile = Helps digest fats (made of bile salts). Bile Salts break fat into droplets this is called Emulsification. It makes it easier for the fats to be digested and later absorbed.

Digestion

LI: Colon Fiber and water left . Water is absorbed5-10 decimeter cubed of water absorbed by the SI0.3-0.5 Decimeter cubed by the LI

Absorption

LI: Rectum Stores feces Egestion

Anus Removes feces Egestion

SI : Small Intestine / LI = Large Intestine

Process of Chewing

• In the mouth:- Large premolars and molars- Both have broad surfaces / ridges on them =>

when pushed together they crush the food- To increase the surface area of the food - Makes it easier for the enzyme to work on the

food.- Bolus = Food made by the tongue into a ball of

food to be swallowed.

Human teeth – structure / functionStructure Function

Incisors In front of mouth – helps to bite off pieces of food to take into the mouth

canines Next to incisors. Same function as incisors. In other carnivores – they are longer – for killing prey

Pre molars Behind the canines- for chewing food into small pieces and mix with saliva – easier for swallowing and tasting & Increase surface area of food so that digestive enzymes can work on food.

molars Behind pre molars. Function – same as pre molars.

Dental decay / proper teeth care

• Tooth decay – when enamel erodes due to acids (produced by bacteria)

• Plaque formation – bacteria and food caught in between teeth that harden around the tooth.

• Foods full of sugar can increases changes for plaque formation => dissolve enamel down to the dentine.

Teeth decay prevention

• Avoid sugary foods.• Regularly clean your teeth (brush / dental

floss/ tooth pick)• Use tooth paste with fluoride (is absorbed by

the teeth and prevents acid build up)• Visit dentist regularly.

Fluoride & prevention of tooth decay

• Fluoride in drinking water creates less tooth decay.

• Too much fluoride can cause black spots of teeth. Can cause vomiting / stomach cramps too.

• Best concentration of fluoride is 1 part per million.

Peristalsis• Longitudinal muscles – lengthwise• Circular muscles – around Swallow -> circular muscle relaxes

(tube gets wider) -> behind food circular muscle contracts .

When circular muscle relaxes – longitudinal muscle contracts (visa versa)

• Happens all the way down the alimentary canal