Chapter 25- Digestive

Digestive Homeostasis Disorders HEART BURN

ACID from the stomach backs up into the esophagus.

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

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

Chemical digestion in the mouth

Our mouth has salivary glands that secrete saliva. This saliva contains the enzyme called salivary amylase. This salivary amylase and the enzyme called maltase (catalyzes maltose into glucose) enables the chemical digestion of the mouth to occur.

Accessory Organs

Pancreas Gall Bladder Spleen

Gall bladder

Pouch structure located near the liver which concentrates and stores bile

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.

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.

Food digestion in the stomach

Stomach's entrance is closed by a ring muscle at the end of the esophagus. When empty, the stomach is collapsed and shaped almost like a hot dog. Once food enters, the folds of stomach wall called rugae smooths out and expands to more than a liter.

Pharynx

The back of the throat.

Four kinds of teeth CANINES

are pointed used for tearing

ESOPHAGUS

canal that connects throat to the stomach

Enzymatic digestion in the stomach THE PARIETAL CELLS

in the gastric glands secrete hydrochloric acid and intrinsic factor, a substance needed for adequate absorption of vitamin B12.

Absorption in the SI Villi

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

Peristalsis

involuntary muscle contractions to move food along

MECHANICAL PHASE

involves the breaking up of food into small pieces, pushing the food down the food tube, and mixing with it digestive juices

CHEMICAL PHASE

involves the further breaking up of the larger molecules of food into smaller molecules by the action of digestive enzymes

stomach

kills germs break up food digest proteins store food

Mouth

mechanical digestion teeth breaking up food chemical digestion saliva amylase enzyme digests starch mucin slippery protein (mucus) protects soft lining of digestive system lubricates food for easier swallowing buffers neutralizes acid to prevent tooth decay anti-bacterial chemicals kill bacteria that enter mouth with food

Digestion

the breakdown of food (either chemically or mechanically) in order to utilize nutrient

DIGESTION

the breakdown of food to smaller molecules

PHARYNX or THROAT

the hallway of food used for both digestive and respiratory system.

Liver

the largest internal organ of the body and also one of the most complex organs which lies in the upper right abdomen just under the diaphragm

DIGESTIVE SYSTEM

the organs and glands in the body that are responsible for digestion

NUTRITION

the process of taking in and using food Process by which organisms obtain and utilize their food.

Four kinds of teeth INCISORS

thin-edged for cutting food

EPIGLOTTIS

tissue that closes the opening to the airway during swallowing

Micronutrients

vitamins, minerals, & water

Digestive Glands

Groups of specialized secretory cells. Found in the lining of the alimentary canal or accessory organs.

Duodenum

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

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.

Pepsin (an enzyme) in your stomach breaking the hamburger into amino acids?

Chemical

Saliva breaking the saltine down into molecules of glucose?

Chemical

Mouth

Chemical and mechanical digestion. Food is chewed (masticated) mechanically. A bolus (lump) is formed with saliva and the tongue.

Stomach

Food is temporarily stored here. Gastric juices are secreted. Has layers of muscle that line the inside. Mechanically and chemically breaks down food.

SPECIALIZED REGIONS WHERE DIGESTION TAKES PLACE

Food processing begins in the mouth. The bite food is then swallowed and is moved through the pharynx into the esophagus. Then, food is mechanically and enzymatically digested in the stomach. Most enzymatic digestion takes place in the small intestine. The large intestine then eliminates wastes leading to the opening for the elimination of wastes called anus.

WHERE DIGESTION TAKES PLACE WITH ASSISTING ORGANS

Food processing begins in the mouth. The bite food is then swallowed and is moved through the pharynx into the esophagus. Then, food is mechanically and enzymatically digested in the stomach. The liver secretes bile. The pancreas secretes digestive enzymes. Most enzymatic digestion takes place in the small intestine. Nutrients are then digested as they move the digestive tract. Nerves and hormones regulate digestion. Absorption takes place mainly through the villi of the small intestine. The large intestine then eliminates wastes leading to the opening for the elimination of wastes called anus.

Rectum

Last section of colon (large intestines) eliminate feces undigested materials extracellular waste mainly cellulose from plants roughage or fiber masses of bacteria

MECHANICAL PHASE OF DIGESTION IN THE MOUTH

MECHANICAL DIGESTION starts in the mouth (Mastication) where four kinds of teeth tear the food into pieces. Four kinds of teeth: INCISORS - thin-edged for cutting food CANINES - are pointed used for tearing MOLARS & PREMOLARS - specialized for crushing and grinding

Chewing a saltine?

Mechanical

Your tongue breaking pieces of a hamburger apart?

Mechanical

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.

THE HUMAN DIGESTIVE TRACT

The human digestive tract is a long, coiled, muscular tube that stretches from the mouth to the anus. From mouth to the anus, the human food tube or the digestive tract is about nine meters long.

Enzymatic digestion in the stomach

The stomach secretes millions of gastric glands.

The tongue, pharynx, and esophagus

The tongue also helps in the mechanical digestion of food. It helps push and mix food while the back part of it secretes mucus making swallowing easier. The pharynx and esophagus conduct food to the stomach. After being chewed, the food is swallowed through the pharynx extending to the esophagus.

Digestive Homeostasis Disorders CONSTIPATION

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

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

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.

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.

ileum

absorption of nutrients & water

jejunum

absorption of nutrients & water

Digestive Homeostasis Disorders GALLSTONES

an accumulation of hardened cholesterol and/or calcium deposits in the gallbladder Can either be "passed" (OUCH!!) or surgically removed

Pepsin

an enzyme that breaks down large proteins into amino acids.

Digestive Homeostasis Disorders APPENDICITIS

an inflammation of the appendix due to infection Common treatment is removal of the appendix via surgery

Small intestine Function

chemical digestion major organ of digestion & absorption absorption through lining over 6 meters! small intestine has huge surface area = 300m2 (~size of tennis court) Structure 3 sections duodenum = most digestion jejunum = absorption of nutrients & water ileum = absorption of nutrients & water

INCOMPLETE DIGESTIVE SYSTEM

common among invertebrates, there is only a single opening for the ingestion of food (an anus is absent)

COMPLETE DIGESTIVE SYSTEM

common among nematodes, annelids, mollusks, echinoderms, and vertebrates, this type has digestive tubes with two openings (a mouth and an anus)

Pancreas

digest proteins trypsin, chymotrypsin digest starch amylase Buffers neutralizes acid from stomach

mouth

digest starch kill germs moisten food

Digestive Homeostasis Disorders ULCERS

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

Absorption by Small Intestines Absorption through villi & microvilli

finger-like projections increase surface area for absorption

Epiglottis

flap of cartilage closes trachea (windpipe) when swallowing food travels down esophagus

Stomach Functions

food storage can stretch to fit ~2L food disinfect food HCl = pH 2 kills bacteria chemical digestion pepsin enzyme breaks down proteins

bolus (lump)

formed with saliva and the tongue.

duodenum

most digestionDuodenum

Larynx

passage for air, closes when we swallow Is approximately 15cm long.

Ingestion

process of taking food into the digestive system so that it may be hydrolized or digested.

Escherichia coli (E. coli)

produce vitamins vitamin K; B vitamins generate gases by-product of bacterial metabolism methane, hydrogen sulfide

liver

produces bile stored in gall bladder break up fats

Liver Function

produces bile bile stored in gallbladder until needed breaks up fats act like detergents to breakup fats Secretes bile. Helps maintain homeostasis by removing or adding nutrients to the blood. Converts excess glucose to glycogen and stores it. Converts excess amino acids to fatty acids and urea Stores iron and certain vitamins. Detoxifies alcohol and other drugs and poisons.

pancreas

produces enzymes to digest proteins & starch

Macronutrients

proteins, lipids, carbohydrates, etc...

PERISTALSIS

pushes soft mass of chewed food (bolus) and mixes it with digestive juices in stomach and small intestine

Large intestines (colon) Function

re-absorb water use ~9 liters of water every day in digestive juices > 90% of water reabsorbed not enough water absorbed diarrhea too much water absorbed constipation

ANTI-PERISTALSIS

results vomiting which prevents body from harmful substances that are ingested.

Enzymatic digestion in the stomach THE CHIEF CELLS

secrete pepsinogen (an inactive enzyme precursor). When pepsinogen comes in contact with the acidic gastric juice, it becomes pepsin (the main digestive enzyme of the stomach).

Peristalsis

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

Rectum

solid wastes exit the body.

Four kinds of teeth MOLARS & PREMOLARS

specialized for crushing and grinding

NUTRIENTS

substances in food that are used as energy sources to run the system of the body