The Digestive System

Marki, Anastasia, and Pritch

What’s The Point?

• Breaks down food in order to gain three essential things: chemical energy, organic molecules and essential nutrients

Chemical Energy

• Energy that is in the form of molecular bonds created during photosynthesis

• Chemical energy in the form of starches is used in cellular respiration to create ATP

Organic Molecules

• Organic molecules are used as building blocks within the organism

Essential Nutrients

• Four different types:

• amino acids

• fatty acids

• vitamins

• minerals

Amino Acids

• Eight essential to humans and a ninth one Histidine is needed by babies

• Complete proteins such as meat have all eight

• Incomplete proteins such as corn or beans do not have all eight unless eaten together

Beans and otherlegumes

Corn (maize)and other grains

Lysine

Essential amino acids for adults

Tryptophan

Isoleucine

Leucine

Phenylalanine

Threonine

Valine

Methionine

Fatty Acids

• Few that animals cannot synthesize themselves:

• linoleic acid is necessary to make membrane phospholipids

Vitamins

• Organic molecules that perform various functions but cannot be synthesized within the body

• Vitamin B2 is FAD+• Water soluble are B and C, work as

coenzymes• Fat soluble A, K, and D work as building

blocks

Minerals

• Inorganic elements

• Calcium and phosphorus used in building bones

• Iodine in hormones

Nourishment

• Under-nourishment- body does not have enough chemical energy

• Mal-nourishment- body does not have enough of a specific essential nutrient

Steps of Eating

Ingestion Digestion Absorption Elimination

Undigestedmaterial

Chemical digestion(enzymatic hydrolysis)

Nutrientmoleculesenter bodycells

Smallmolecules

Mechanicaldigestion

Food

Piecesof food

1 2 3 4

Types of Digestive Compartments

• Intracellular digestion versus extracellular digestion

Intracellular Digestion

• By phago or pino cytosis, food is ingested by cells and made into food vacuoles where they can be digested

• Occurs in sponges (filter feeders) and single-celled organisms

Extracellular Digestion

• Gastrovascular cavity: only a mouth

• Alimentary canal: mouth and anus

Fig. 41-10

Cecum

Anus Anus

Ascendingportion oflarge intestine

Gall-bladder

Smallintestine

Largeintestine

Smallintestine

Rectum

Pancreas

Liver

Salivary glands

TongueOral cavity

PharynxEsophagus

Sphincter

Stomach

Sphincter

Duodenum ofsmall intestine

Appendix

Liver

Pancreas

Smallintestine

Largeintestine

Rectum

StomachGall-bladder

A schematic diagram of thehuman digestive system

Esophagus

Salivaryglands

Mouth

Humans have extracellular digestion and an alimentary canal

Cnidaria- exhibit a gastrovascular cavity

Main Organs

Layers of Tissue

Linear Path

Anus

Liver

Pancreas

Smallintestine

Largeintestine

Rectum

Stomach

Gall-bladder

A schematic diagram of thehuman digestive system

Esophagus

Salivaryglands

Mouth

Whole Body

Ingestion

• Mouth• Salivary glands that secrete saliva• Amylase hydrolyzes starch and glycogen• Muchin lubricates mouth and food to avoid abrasion• Buffer neutralizes acids• Tongue regulates what goes into mouth by taste• Bolus, a ball of food, is created and shoved back to

the pharynx• Pharynx: (fork between trachea and esophagus) • epiglottis covers glottis opening to trachea

Pharynx

Ingestion

• Esophagus: muscles lining it

• Peristalsis- wave-like contractions that push food down in 5-10 seconds

• Sphincter- muscular rings in the esophagus that close off parts of the alimentary canal

Stomach

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are needed to see this picture.

Digestion

• Stomach:

• Gastric Juice : HCL + pepsin• Chyme: gastric juice + food • Mucus• Muscle

Digestion

• Small intestine (duodenum)

• - secretions from pancreas and gall bladder

Blood Sugar Homeostasis

Homeostasis:90 mg glucose/100 mL blood

Stimulus:Blood glucose

level risesafter eating.

Stimulus:Blood glucose

level dropsbelow set point.

Cecum

Cecum

Small intestine

HerbivoreCarnivore

Colon(largeintestine)

StomachSmall intestine

Large Intestine

• 90% water is recollected

• Includes the colon

Linear Flow Total

Bloodstream

Veins to heart

Lymphaticsystem

Small intestine

Esophagus

StomachLipids

Mouth

Hepatic portal vein

Absorbed food(except lipids)

Absorbedwater

Secretions fromthe gastric glandsof the stomach

Secretions from the pancreas and the liver

Liver

Rectum

Anus

Largeintestine

Final Table

Oral cavity,pharynx,esophagus

Stomach

Lumen ofsmall intes-tine

Epitheliumof smallintestine(brushborder)

Carbohydrate digestion

Polysaccharides

Smaller polysaccharides,maltose

Polysaccharides

Maltose and otherdisaccharides

Disaccharides

Protein digestion Nucleic acid digestion Fat digestion

Proteins

Small polypeptides

Pepsin

Pancreatic amylases

Salivary amylase

Disaccharidases

Monosaccharides

Small peptides

Amino acids

Amino acids

Polypeptides

Smallerpolypeptides

Pancreatic trypsin andchymotrypsin

Pancreatic carboxypeptidase

Dipeptidases, carboxypeptidase,and aminopeptidase

DNA, RNA

Pancreatic nucleases

Fat globules

NucleotidesFat droplets

Nucleosides

Nitrogenous bases,sugars, phosphates

Nucleotidases

Nucleosidasesandphosphatases

Glycerol, fattyacids, monoglycerides

Bile salts

Pancreatic lipase

(starch, glycogen) (sucrose, lactose)

Diseases

• Crohn’s Disease

• Acid Reflux Disease• Celiac Disease

Crohn’s Disease

• an inflammatory autoimmune disease• Symptoms: primarily abdominal pain, diarrhea

(usually with blood), vomiting or weight loss• The immune system attacking the

gastrointestinal tract and producing inflammation in the gastrointestinal tract

• No cure, but stem cell research is promising• medication to control symptoms, maintain

remission and prevent relapses

Crohn’s Disease

• Affects the ileum and the large intestine or both most commonly

• Structuring: narrowing of the bowel which can lead to bowel obstruction or changes in the caliber of feces

• Penetrating: creates abnormal passageways between the bowel and other structures like the skin

• Inflammatory: inflammation without causing strictures or fistula

Celiac Disease

• an autoimmune disorder of the small intestine that occurs in genetically predisposed people.

• Symptoms: chronic diarrhea, failure to thrive in children, fatigue. There are asymptomatic cases

• Treatment: a gluten free diet

Acid Reflux

Acid is regurgitated and burns the esophagus

Symptoms: Heartburn, Nausea, Chronic Salivation, Damage to esophagus

Treatments are usually lifestyle (foods, positional therapy) changes along with medications and possibly surgery

Acid Reflux

• Reflux esophagitis

• Esophageal strictures

• Barrett's esophagus

• Esophageal adenocarcinoma—a rare form of cancer.

• http://www.youtube.com/watch?v=o4ulnK5mK-A&feature=related