health course chapter 10

Section 10.1 Your Digestive System

Your digestive system has three main functionsFunctions of the Digestive System

• digestion• absorption• elimination


• The process by which the digestive system breaks down food into molecules that the body can use is called digestion.

Digestion

• During mechanical digestion, foods are physically broken apart into smaller pieces.

• During chemical digestion, chemicals produced by your body break large molecules into smaller ones that your body can use.

• Most of the chemicals involved in digestion are enzymes, substances that speed up reactions.


• Absorption is the process by which nutrients pass through the lining of your digestive system into your blood.

Absorption and Elimination

• Materials that are not absorbed are eliminated from the body as wastes.


The organs of the digestive system include theStructures of the Digestive System

• mouth• pharynx• esophagus• stomach• small intestine• large intestine• liver• gallbladder• pancreas


• Your teeth tear, crush, and grind your food.Mouth

• An enzyme in saliva begins to break down starches in your food.

• Saliva moistens the bites of food.

• Your tongue pushes the food around.


• The pharynx is the junction between the digestive tract and the respiratory system.

Pharynx

• A flap of tissue called the epiglottis seals off the trachea, or windpipe, preventing food and liquid from entering your lungs.


• After passing through the pharynx, the food enters the esophagus, a muscular tube that connects the pharynx to the stomach

Esophagus

• Waves of muscle contractions, called peristalsis, push food through the rest of the digestive system.


Pharynx

EpiglottisMouth

Salivary gland

LiverEsophagus

Stomach

Pancreas

Small intestine

Large intestine

Rectum

Gallbladder


• From the esophagus, food passes through a valve and into the stomach, a muscular pouch located in the abdomen.

Stomach

• Mechanical digestion occurs as three layers of muscle produce a churning motion.

• Chemical digestion occurs as cells lining the stomach release gastric juice.

• Peristalsis moves the food, which is now a thick liquid called chyme (kym), into the small intestine.


• The small intestine is where most chemical digestion and absorption of nutrients takes place.

Small Intestine

• Liver The role of the liver is to produce bile. Bile is a substance that physically breaks up large fat droplets that clump together.

• Gallbladder Bile flows from the liver into the gallbladder, the organ that stores bile.

• Pancreas The pancreas secretes enzymes into the small intestine that complete the breakdown of carbohydrates, proteins, and fats.

• The lining of the small intestine is covered with millions of tiny fingerlike projections called villi (singular, villus).


• The large intestine is about 5 feet long and 3 inches wide.

The Large Intestine

• As the material moves through the large intestine, most of the remaining water is absorbed into the blood.

Section 10.2 Keeping Your Digestive System Healthy

• Healthy eating habits and regular exercise are important for keeping your digestive system healthy.

Avoiding Digestive Disorders

• Consume plenty of fiber.• Avoid fatty foods.• Eat moderately.• Plan meals for a time when you can relax.• Drink water.• Get regular exercise.


To avoid foodborne illnesses, it is very important to prepare and store food properly.

Food Safety


• Foodborne illnesses result from consuming a food or drink that contains either a poison or a disease-causing microorganism.

Foodborne Illness

• Microorganisms are typically spread in one of three ways.

• food is undercooked

• raw food touches cooked food

• people preparing food transfer the organisms onto their hands, countertops, or utensils


• Cook meat, seafood, poultry, and eggs thoroughly.Food Preparation and Storage

• Quickly refrigerate leftovers.

• Wash your hands with soap.

• Use paper towels, rather than sponges.

• Rinse fruits and vegetables in running water.

• Keep uncooked food separated to prevent cross-contamination, the spread of microorganisms from one food to another food.

Section 10.3 Your Excretory System

Health Stats This graph compares the amount of water you excrete in sweat and urine on a normal day and on a hot day.

In a paragraph, discuss how weather affects water loss.


• Excretion is the process by which the body collects and removes wastes.

Organs of Excretion

• Several organs in the body are involved in waste collection and removal

• liver• lungs• skin• kidneys


• The liver converts impurities and poisons in the body to less harmful substances.

Liver

• The liver forms urea from a harmful waste product of protein breakdown.


• The lungs remove carbon dioxide and some water from the body.

Lungs and Skin

• Sweat glands in the skin serve an excretory function because water and urea are excreted in perspiration.


• The kidneys, which are the major organs of the excretory system, filter urea and other wastes from the blood.

Kidneys

• You have two kidneys, each about the size of a fist.

• Urine is a watery fluid produced by the kidneys that contains urea and other wastes.


Kidney The kidneys produce urine by filtering urea and other wastesfrom the blood.

UreterOne ureter extends from each kidney. The ureters carry urinefrom the kidneys to the bladder.

BladderThe bladder is a saclikemuscular organ that stores urine.

UrethraUrine travels through the urethra as it exits the body.

The Excretory System


• Each kidney contains about a million nephrons, tiny filtering units that remove wastes and produce urine.

Filtration of Wastes

• The nephrons filter wastes in stages.

• Needed materials and wastes are filtered from the blood.

• Most needed materials are returned to the blood, and the wastes are eliminated from the body.


• Blood enters the kidneys.Filtering Out Wastes

• Blood flows through smaller blood vessels until it reaches a cluster of tiny blood vessels in a nephron called a glomerulus (gloh MUR yoo lus).

• Urea, salts, glucose, and water are filtered from the glomerulus into a thin-walled capsule.


• As the filtered material flows through the tube, the glucose, most of the water, and other needed materials pass from the tube back into the blood.

Formation of Urine

• Urea and other wastes, such as excess vitamins and harmful substances, stay in the tube.


A Nephron Blood flows from an artery into a nephron.

In the glomerulus, urea, water, glucose, and other materials are filtered from the blood. These materials pass into a capsulethat surrounds the glomerulus.

The materials pass from the capsuleinto a long, twisting tube. The tubeis surrounded by blood vessels.

As the filtered material flows through the tube, most of the water and glucose are reabsorbed into the blood. Most of the urea and other waste stay in the tube.

After the reabsorbing process iscomplete, the liquid that remainsin the tube is called urine.


To help your kidneys function at their best, it is important to drink plenty of water and to see a doctor if you have symptoms of an infection.

Keeping Healthy


Because many of the waste products filtered by your kidneys are harmful, it is best if they are diluted as much as possible.

Drinking Water


• Urinary tract infections, which are bacterial infections of the urethra or bladder, are common disorders.

Treating Infections

• Symptoms of urinary tract infections include frequent, painful urination and blood in the urine.


• Kidney stones are pebblelike masses of salts, and often calcium, that form in the kidneys.

Preventing Kidney Stones

• Drinking plenty of fluids and eating a diet that is low in salt may reduce your risk of developing kidney stones.


• Kidneys that are damaged from an injury, diabetes, uncontrolled high blood pressure, or other diseases may fail.

Treating Kidney Failure

• Kidney failure can be treated by dialysis.

• During dialysis, a machine is used to filter blood in place of the kidneys.

health course chapter 10

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