Human Digestion

Nutrition _________________________________________________. There are two parts to Nutrition: 1. __________________- process of taking food into the digestive system so that it may be hydrolized or digested. 2. ___________________- the breakdown of food (either chemically or mechanically) in order to utilize nutrients

Types of Nutrients __________________- vitamins, minerals, & water __________________________- proteins, lipids, carbohydrates, etc…

Human digestive system

GI (gastrointestinal) tract = ____________________

Ingestion Mouth –________________________ __________ –breaking up food –________________________ ___________ –__________________ »enzyme digests starch –_________________ »slippery protein (mucus) »protects soft lining of digestive system »lubricates food for easier swallowing –_________________ »neutralizes acid to prevent tooth decay –_________________________ »kill bacteria that enter mouth with food

mouth  break up food  digest starch  kill germs  moisten food

Mouth ____________ and ______________ digestion. Food is chewed (masticated) mechanically. A ________ (lump) is formed with saliva and the tongue.

Swallowing (& not choking) _____________________ –flap of cartilage –closes ___________ (windpipe) when swallowing –food travels down ________________ ___________________ –involuntary muscle contractions to move food along

Which type of digestion is the following? 1.Chewing a saltine? -_________________ 2. Saliva breaking the saltine down into molecules of glucose? -_______________________ 3. Your tongue breaking pieces of a hamburger apart? ____________________________ 4. Pepsin (an enzyme) in your stomach breaking the hamburger into amino acids? _________________________

Pharynx The back of the throat. ____________- passage for air, closes when we swallow. Is approximately 15cm long.

Digestive Glands Groups of specialized ___________ cells. Found in the lining of the alimentary canal or accessory organs.

series of involuntary wave-like muscle contractions which move food along the digestive tract ____________

Stomach Food is temporarily stored here. _______________ are secreted. Has layers of muscle that line the inside. _____________ and ____________ breaks down food.

Stomach Functions –________________ can stretch to fit ~2L food –_________________ HCl = pH 2 –kills bacteria –_________________ __________ –__________________________ But the stomach is made out of protein! What stops the stomach from digesting itself? mucus secreted by stomach cells protects stomach lining

stomach  kills germs  break up food  digest proteins  store food sphincter mouth  break up food  digest starch  kill germs  moisten food

Gastric Juices Secreted by the stomach. Acidic (pH ) (HCl). ___________- an enzyme that breaks down large ________ into _______________. Food is further broken down into a thin liquid called ______________.

Accessory Organs Pancreas Gall Bladder Spleen

Gall bladder __________________________________ ______________ – a long tube that carries BILE. The top half of the common bile duct is associated with the liver, while the bottom half of the common bile duct is associated with the pancreas, through which it passes on its way to the intestine.

BILE Bile emulsifies lipids (__________________________________ ________________________) Bile is a bitter, greenish-yellow alkaline fluid, stored in the gallbladder between meals and upon eating is discharged into the duodenum where it aids the process of digestion.

Pancreas An organ which secretes both ______________ enzymes (exocrine) and _______________ (endocrine) ** Pancreatic juice digests ______________________________________ ______________________________________

Pancreas ______________________ –_________________ trypsin, chymotrypsin –________________ amylase Buffers –neutralizes acid from stomach

Liver Function –___________________________ _____________________________ ____________ –act like detergents to breakup fats bile contains colors from old red blood cells collected in liver = iron in RBC rusts & makes feces brown bile contains colors from old red blood cells collected in liver = iron in RBC rusts & makes feces brown

pancreas  produces enzymes to digest proteins & starch stomach  kills germs  break up food  digest proteins  store food mouth  break up food  digest starch  kill germs  moisten food liver  produces bile - stored in gall bladder  break up fats

Small Intestine Most _______________ digestion takes place here. Simple __________ and ____________ are absorbed into the inner lining. ____________ and ____________ go to lymphatic system. Lined with villi, which increase surface area for absorption, one cell thick.

Small intestine Function –_______________________________ major organ of _________ & ______________ –_____________________________ over 6 meters! small intestine has huge surface area = 300m 2 (~size of tennis court) Structure –3 sections __________________ = most digestion ___________________ = absorption of nutrients & water ___________ = absorption of nutrients & water

Duodenum 1st section of small intestines –acid food from stomach –mixes with digestive juices from:  pancreas  liver  gall bladder

stomach  kills germs  break up food  digest proteins  store food mouth  break up food  digest starch  kill germs  moisten food pancreas  produces enzymes to digest proteins & starch

Absorption in the SI Much absorption is thought to occur directly through the wall without the need for special adaptations _______________________________________________ _______________________________________________. _________ - increase the surface area of the small intestines, thus providing better absorption of materials

Absorption by Small Intestines ________________________________ –finger-like projections –_________________________________

VILLI

Large intestines (colon) Function –______________________ use ~9 liters of water every day in digestive juices > 90% of water reabsorbed –not enough water absorbed »______________ –too much water absorbed »______________

Large Intestine __________________ pass through the large intestine. These are ____________ solids (fibers). Water is absorbed. _________________ are reabsorbed with the water. _______________- solid wastes exit the body.

You’ve got company! Living in the large intestine is a community of helpful bacteria –___________________________ (E. coli) ______________________ –vitamin K; B vitamins ______________________ –by-product of bacterial metabolism –methane, hydrogen sulfide

Appendix Vestigial organ

Rectum Last section of colon (large intestines) –eliminate feces __________________ –_______________ »mainly cellulose from plants »______________ –masses of bacteria

Digestive Homeostasis Disorders ___________ – erosion of the surface of the alimentary canal generally associated with some kind of irritant

______________________ – a condition in which the large intestine is emptied with difficulty. Too much water is reabsorbed and the solid waste hardens Digestive Homeostasis Disorders

_____________ – a gastrointestinal disturbance characterized by decreased water absorption and increased peristaltic activity of the large intestine. This results in increased, multiple, watery feces. __________________________

Digestive Homeostasis Disorders _________________ – an inflammation of the appendix due to infection Common treatment is removal of the appendix via surgery

Digestive Homeostasis Disorders ________________ – an accumulation of hardened cholesterol and/or calcium deposits in the gallbladder Can either be “passed” (OUCH!!) or surgically removed

Digestive Homeostasis Disorders ____________________ - a psychological condition where an individual thinks they appear overweight and refuses to eat. Weighs ________________ than what is developmentally expected for age and height Young girls do not begin to menstruate at the appropriate age.

Digestive Homeostasis Disorders _____________ – ACID from the stomach backs up into the esophagus.