The Digestive and Excretory Systems

Objectives

• To list the organs of the digestive and excretory systems• To describe the function of the organs of the digestive

and excretory system• To compare and contrast the digestive and excretory

systems• To explain how the digestive and excretory systems

relate to each other as well as in relation to other body systms

Components

• Esophagus• Stomach• Small Intestine• Large Intestine• Gall bladder• Liver• Pancreas

Digestive System

• This system is responsible for breaking down food into a useable form of energy for the body

Alimentary Canal

• Path food travels through the body (your digestive tract)– From mouth to the anus

Organs of the Digestive system

• Mouth– Digestion starts here– Mechanically breaks down food by the chewing

mechanism• Chewing is called mastication

– Here there are enzymes (present in saliva) that also aid in the break down of food• Enzymes are chemicals that simply break up

particles/bacteria/viruses… etc– Words ending in –ase are usually enzymes

Stomach

Esophagus

Esophagus

• the tube that connects your mouth and your stomach

• You have a trap door called the epiglottis to cover your windpipe when you swallow.

Organs of the Digestive System

• Esophagus- muscular tube through which food travels to the stomach– Food moves along the digestive system by means

of a muscular movement called peristalsis• Peristalsis is an involuntary contraction (and

relaxation) of muscles in the digestive system that moves food along the alimentary canal

– At the beginning of the esophagus is a small flap (or gate-like structure) called the epiglottis that closes off the entrance to the trachea when you swallow

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Peristalsis

Stomach• A stretchy bag that

holds your food after you eat

• Helps to break food into smaller pieces so your body can use it for energy and nutrition

Organs

• Stomach- muscular organ responsible for the further breakdown of nutrients– Mixing chamber and storage chamber• Chemical break down through stomach acid • Mechanical break down through churning/mixing

– No food is absorbed through the stomach wall (which is coated with mucus to prevent the stomach acid from “eating through” itself)

Small Intestine

Small Intestine

• Tube that is 20 feet long.

• Continues to digest food

• Food stays in your small intestine for 4 to 8 hours

Organs

• Small intestine- chemical digestion continues here; in fact, most of the chemical digestion occurs here along with NUTRIENT ABSORPTION!– From ~15 to 32 feet• Average 17 feet

– Has 3 sections• Duodenum-

– ~10 inches– digestive juice are secreted from intestine, pancreas and liver

are mixed with the food to further break it down

Small intestine cont

• Pt 2– Jejunum- ~4 to 7 ft long• Food nutrients are absorbed here

• Pt 3– Ileum- ~5 to 7 feet long• More food absorption occurs here

Small intestine

• Food absorption– Villi- small tube structures that cover the wall of

the small intestine• Used for food/nutrient absorption

– Food absorbed in the small intestine enters the blood stream in the capillaries and is transported throughout the body (to where needed)

Liver

Liver• Factory for antibodies and bile

• Stores vitamins and sugars until your body needs them

Food Processors

• Liver- the largest internal organ– Functions as an aid to the digestive system in 2

ways• 1 through production of bile- yellowish-greenish fluid

used for digestion of fats in the small intestine• 2 to filter toxic substances from the body and it stores

excess glucose

Gall Bladder

Gall Bladder• Storage tank for bile (a greenish-yellow liquid)

that helps your body break down and use fats

• Located under your liver

• Shaped like a pear

Pancreas• Helps you digest

food by breaking down sugars

Large Intestine

Large Intestine• Tube that is 5 feet long

• Gets waste from small intestine

• Waste stays for 10 to 12 hours

Garbage Disposal

• Large Intestine/Colon – Measures about 5 feet long– This organ absorbs most of the water and some of

the remaining nutrients left from the food you ate– After food has finished its trip through the colon it

moves to the rectum and then anus to be excreted as fecal matter

Large Intestine/Colon

• Also aids the immune system in that it contains healthy bacteria to fight off harmful bacteria (or microorganisms)– These bacteria also provide vitamins for the body

Functions of the Digestive System

• Digest the food we eat

• Take the nutrients out of your food so your body can use it

Human Excretory System

Excretory System• The kidneys regulate the amount of water, salts and

other substances in the blood. • The kidneys are fist-sized, bean shaped structures

that remove nitrogenous wastes (urine) and excess salts from the blood.

• The ureters are tubes that carry urine from the pelvis of the kidneys to the urinary bladder.

• The urinary bladder temporarily stores urine until it is released from the body.

• The urethra is the tube that carries urine from the urinary bladder to the outside of the body.

• The outer end of the urethra is controlled by a circular muscle called a sphincter.

Kidneys• Two reddish organs just above the waist

behind the stomach• Filter the blood and removes waste

Food Processors

• Gallbladder- located beneath the liver and stores the bile produced in the liver

• Pancreas- located behind the stomach and produces pancreatic juices– Pancreatic juices are sent to the small intestine to

aid in digestion of carbohydrates, proteins and fats

The Job of the Kidneys

• They are responsible for cleaning the blood by removing metabolic wastes, excess solutes, and excess water and excreting them as urine

• Besides removing urea, it also removes excess salts or glucose, the remnants of drugs (reason for urine tests), and excess water.

Function of the Kidney• The principal function of the kidney is to

filter blood in order to remove cellular waste products from the body.

• At any given time, 20 % of blood is in the kidneys. Humans can function with one kidney.

• If one ceases to work, the other increases in size to handle the workload.

NOTE

• Since the kidneys control what leaves and what remains in the nephrons, they maintain the levels of water, ions and other materials nearly constant and within the limits to maintain homeostasis.

Urinary Bladder• Smooth muscle bag• Stores waste solution - urine

Urethra• Connects bladder to outside of the body• Allows urine to pass out of the body

Ureter• Connects the kidneys to the urinary bladder

Nephron• Filtering unit of the

kidney• Blood enters full of

waste and leaves filtered

• Blood enters under high pressure and flows into the capillary beds

Regulation of Water Levels

• If the blood becomes too dilute or too concentrated with solutes, then it can interfere with normal cellular activity.

• The kidneys are able to regulate water concentration in the blood by removing excess water if the blood is too dilute or conserving water in the blood if it is not dilute enough

Waste Products

• Carbon dioxide – a waste product of cellular respiration is dumped into the blood stream and eventually removed by the lungs

• Ammonia (NH3) is removed through water– This waste comes from the cells breakdown of

old proteins – It is also what makes bleach smell so in high

concentrations it is poisonous to the cells and must be removed

Formation of Urine

• If there is too much water in the blood, then it is removed and put in urine.

• If there is not enough water in the blood, the kidneys will not remove it.

• If there is too much urea or other solutes in the blood, the kidneys will remove these excess solutes.

• By regulating solute numbers and water volume, the kidneys normally maintain homeostasis in blood solute concentration.

Why is excretion necessary?

• In order for cells to stay alive, they must continually intake water and other molecules.

• The cells would continue to get bigger and bigger if they only took in molecules

• They must also export molecules– These molecules may be important signaling

molecules such as hormones, or they may be molecules of glucose on their way to other cells, or they may be waste products of cellular metabolism that cells need to dispose.

Removal of Ammonia

• Once excreted into the blood stream by cells, it is carried to the liver where it is converted from ammonia into urea which is much less toxic

• It is then carried from the liver to the kidneys where it is removed

Excretory System Problems

• Kidney stones – crystalized mineral salts and uric acid salts in the urine. Stones block flow of urine and cause excrutiating pain.

• Kidney failure - can be caused by long-term diabetes, infections, physical injuries, chemical poisoning. Causes toxic materials to build up to lethal levels. Dialysis or kidney transplant is the treatment.

Describe the functions of a person's urinary system

Rids the body of wastes, control blood volume, balances salts & water

Explain how the kidneys remove wastes and keep fluids and salts in balance

Kidneys filter the blood to remove extra wastes, sugar, water, and salt. Sugar,

water, and salt still needed by the body is returned to the blood.

Describe what happens when the urinary system does not function

properly.

Wastes are not removed. This causes the destruction of cells. Water not removed

causes swellings and too much water around the heart. Slats that are not taken away can

cause organ damage.

Compare the excretory system and urinary system

The excretory system is made of all body organs that get rid of wastes. The urinary

system is made of organs that produce urine as a waste.

How is your urinary system similar to a water-purification system?

It serves as a filter to screen out harmful materials and helps get rid of

wastes in the blood

When you drink a lot of water, you also need to urinate often. Why?

The job of the kidneys is to eliminate excess water and wastes. If you drink

more than your body needs, it is eliminated by the urinary system.

Healthy Habits• Eat foods that

are high in fiber like fruits and vegetables

•Drink plenty of water

• Chew your food completely before you swallow

Interesting Facts• Food is in your digestive system

for about 24 hours

• Your stomach stretches when you eat like a balloon being filled with air