Human Digestion

Nutrition • process by which organisms obtain and utilize their food

2 Parts: • 1. ingestion- process of taking food into the

digestive system so that it may be hydrolized or digested.

• 2. digestion- the breakdown of food (either chemically or mechanically) in order to utilize nutrients

Terms to know: • Autotrophs- make their own food.

• Heterotrophs- get food from other sources.

Nutrients • Micronutrients- vitamins, minerals, & water

• Macronutrients- proteins, lipids, carbohydrates, etc…

Mouth• Chemical and

mechanical digestion.

• Food is chewed (masticated) mechanically.

• A bolus (lump) is formed with saliva and the tongue.

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?

GI (gastrointestinal) tract = alimentary canal

Pharynx• The back of the

throat.• Larynx- passage

for air, closes when we swallow.

• Is approximately 15cm long.

Digestive Glands• Groups of

specialized secretory 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

Peristalsis

Stomach• Food is temporarily

stored here.• Gastric juices are

secreted.• Has layers of

muscle that line the inside.

• Mechanically and chemically breaks down food.

Gastric Juices• Secreted by the

stomach.• Acidic (pH 1.5-2.5)

(HCl).• Pepsin- an enzyme that

breaks down large proteins into amino acids.

• Food is further broken down into a thin liquid called chyme.

Accessory Organs

• Pancreas

• Gall Bladder

• Spleen

Gall bladder

• Pouch structure located near the liver which concentrates and stores bile

• Bile duct – 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 (physically breaks apart FATS)

• 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 digestive enzymes (exocrine) and hormones (endocrine)

• ** Pancreatic juice digests all major nutrient types.

• Nearly all digestion occurs in the small intestine & all digestion is completed in the SI.

Small Intestine• Most chemical

digestion takes place here.

• Simple sugars and proteins are absorbed into the inner lining.

• Fatty acids and glycerol go to lymphatic system.

• Lined with villi, which increase surface area for absorption, one cell thick.

Absorption in the SI • Much absorption is thought to occur directly through the wall

without the need for special adaptations

• Almost 90% of our daily fluid intake is absorbed in the small intestine.

• Villi - increase the surface area of the small intestines, thus providing better absorption of materials

VILLI

Large Intestine• Solid materials pass

through the large intestine.

• These are undigestible solids (fibers).

• Water is absorbed.• Vitamins K and B are

reabsorbed with the water.

• Rectum- solid wastes exit the body.

Digestive Homeostasis Disorders

• ULCERS – erosion of the surface of the alimentary canal generally associated with some kind of irritant

• CONSTIPATION – a condition in which the large intestine is emptied with difficulty.

• Too much water is reabsorbed and the solid waste hardens

• Solution: Drink more water eat more fiber.

Digestive Homeostasis Disorders

Digestive Homeostasis Disorders

• DIARRHEA – a gastrointestinal disturbance characterized by decreased water absorption and increased peristaltic activity of the large intestine.

• This results in increased, multiple, watery feces.

• This condition may result in severe dehydration, especially in infants

Digestive Homeostasis Disorders

• APPENDICITIS – an inflammation of the appendix due to infection

• Common treatment is removal of the appendix via surgery

Digestive Homeostasis Disorders

• GALLSTONES – an accumulation of hardened cholesterol and/or calcium deposits in the gallbladder

• Can either be “passed” (OUCH!!) or surgically removed

Digestive Homeostasis Disorders

• ANOREXIA NERVOSA - a psychological condition where an individual thinks they appear overweight and refuses to eat.

• Weighs 85% or less than what is developmentally expected for age and height

• Young girls do not begin to menstruate at the appropriate age.

Digestive Homeostasis Disorders

• HEART BURN – ACID from the stomach backs up into the esophagus.

Nutrition• Carbohydrates- main source of

energy. Starch and sugars are carbohydrates.

• Monosaccharides- the simplest carbohydrates (Glucose).

• Disaccharides- the combination of two simple sugars ( Maltose).

Nutrition continued……

• Polysaccharides- long chains of monosaccharides (simple sugars) bonded together. Starches are polysaccharides, they are also found in Cellulose.

• Lipids-fats and oils. The building blocks of lipids are fatty acids and glycerol.

Proteins• Are made up of Carbon,

Hydrogen, Oxygen, and NITROGEN.

• Proteins are made up of amino acids.

• Two amino acids bonded together are called a dipeptide.

• Many amino acids bonded together form a chain called a polypeptide.

Enzymes• Enzymes control chemical reactions.• Enzymes are large complex protein

molecules.• Enzymes are organic catalysts. They

either speed up or slow down a chemical reaction.

• A coenzyme is the non-protein part of an enzyme (usually vitamins).

• Enzyme function is controlled by temperature, pH, and conc. of enzymes and substrate.

Nucleic Acids• Are very large molecules made up of

carbon, oxygen, nitrogen, and phosphorus.

• Nucleotides are the building blocks of nucleic acids.

• Nucleotides are made up of a phosphate group, a sugar molecule, nitrogen base.

pH Scale• The pH scale measures

whether a solution is acid, basic, or neutral.

• 0-6.9 is acid• 7.1-14 is basic• 7 is neutral

Let’s go to the Video!