Download THE DIGESTIVE AND URINARY SYSTEMS

UNIT 12: Digestive & Urinary Systems Notes
Cells → Tissues → Organs → Organ Systems → An Organism (simplest to most complex)
Cells are made of atoms. The six most important elements for life are: Carbon, Hydrogen, Nitrogen,
Oxygen, Phosphorous and Sulfur. These six elements make up 99% of the mass of the human body.
Your body is a collection of systems that must work together in order to maintain homeostasis. Each
separate organ system cannot work independently and relies on many other organ systems to work
properly. If one organ system is not working as it should, your other systems can be affected.
I.
The Digestive System
You feel hungry because your brain receives signals that your cells need energy, but eating is only
the beginning of the story.
Digestive System: A collection of organs that break down food so that it can be used by the body;
the organs in this system include the stomach, the pancreas, the liver, the gallbladder, the small
intestine, and the large intestine.
A. Additional Functions of the Digestive System.
1. Mechanical & Chemical breakdown of food into smaller components that are more
easily absorbed into the blood stream.
- Carbohydrates into sugars
- Lipids into fats, oils or waxes
- Proteins into amino acids
- Nucleic Acids into nucleotides
B. Digestive System at a Glance
- The most obvious part of your digestive system is the digestive tract.
- Digestive Tract: A series of tubelike organs that are joined end to end.
∙ Includes your mouth, throat, esophagus, stomach, small intestine, large
intestine, rectum, and anus.
∙ Also includes the liver, gallbladder, pancreas, and salivary glands (they all
secrete substances that are used in digestion.
- The human digestive tract may be more than 9 meters long!
- The digestive tract is basically a long tube with an opening at each end.
C. The Journey of a Food
- Digestion: The process of breaking down food into a form that can pass from the
digestive tract into the bloodstream.
- Enzymes: Break some nutrients into smaller particles that the body can use.
∙ Enzymes in the stomach and small intestine break down proteins.
- Enzymes act as a chemical scissors to cut the long chains of amino
acids into small chains → The small chains are then split by other
enzymes → Individual amino acids are small enough to enter the
bloodstream, where they can be used to make new proteins.
- There are two types of digestion – mechanical and chemical
∙ Mechanical Digestion: The breaking, crushing, and mashing of food.
- Physical Change: A change in a substance that doesn’t change
what the substance is. (change in shape and size only)
∙ Teeth break down food into smaller pieces.
∙ Peristalsis in the esophagus and stomach mash it into
small pieces as it moves it.
∙ Water being absorbed into the bloodstream.
∙
-
Chemical Digestion: Large molecules are broken down into nutrients
through chemical change.
- Chemical Change: A change in a substance that changes what
the substance is.
∙ Saliva chemically breaks down starch
(carbohydrates) into sugar using the enzyme amylase.
∙ Saliva also starts the digestion of fats using an
enzyme called lipase.
∙ Hydrochloric acid and other enzymes (pepsin) are
secreted in the stomach causing a chemical change
with the food as it breaks it down even more.
∙ Bile breaks down fat in the liver.
Nutrients: Substances in food that the body needs for normal growth,
maintenance, and repair.
∙ There are 3 major types of macromolecule nutrients.
- Carbohydrates, Lipids & Proteins
- Proteins – made up of chains of amino acids. Proteins are too
large to be absorbed directly into the bloodstream, so they must
be broken down first into smaller parts (the amino acids).
D. Digestion Begins in the Mouth
1. Chewing is important for two reasons – First, chewing creates small, slippery
pieces of food that are easier to swallow than big, dry pieces. Second, small pieces
of food are easier to digest.
2. The tongue moves food around in the mouth and holds food in place while
chewing. It also aids in the swallowing process.
3. Teeth (most adults have 32 permanent teeth)
- Teeth are very important organs for mechanical digestion. With the help of
strong muscles and your jaw bones, teeth are able to break and grind food.
- Enamel: The outermost layer of a tooth and it is the hardest material in the body.
∙ Enamel protects nerves and softer material inside the tooth.
- Parts of the teeth: Crown, Enamel, Neck, and Root
- You have 4 main types of teeth:
1. Incisors – for shredding food
2. Canine – for shredding food
3. Premolars – for mashing food
4. Molars – for grinding
4. And Over the Gums
- Saliva: A liquid that contains an enzyme that begins the chemical digestion
and is watery to make it easier to swallow food.
∙ Saliva is made in salivary glands located in and around the mouth.
∙ The enzyme in saliva begins the chemical digestion of carbohydrates.
Saliva turns complex carbohydrates into simple sugars.
5. Look Out Stomach, Here It Comes!
- Once the food is soft and mushy, the tongue pushes it into the throat and
down the esophagus.
- Esophagus: A long, straight tube that connects the throat to the stomach.
- Peristalsis: The rhythmic muscle contractions that esophagus uses to
squeeze the mass of food down the throat.
∙ Peristalsis forces the food into the stomach.
E.
The Stomach’s Harsh Environment
1. Stomach: A muscular, baglike organ attached to the lower end of the esophagus.
∙ A thick substance called mucus covers the stomach’s lining and offers
some protection from its harsh environment. However, the acids still
damage the lining, and the entire lining must be replaced every few days.
∙ The stomach grinds (using mall ridges on the inside surface) and mixes
food for hours before it releases the mixture into the small intestine.
∙ The stomach continues the physical digestion of your food by squeezing
its contents with muscular contractions. The stomach also produces an
acid enzyme that helps break the food down into usable nutrients.
∙ Stomach acid also kills most bacteria you might swallow while eating.
∙ Chyme: Soupy mixture of broken down food in the stomach.
2. Doorway to the Small Intestine
∙ Chyme is slowly released into the small intestine through a small ring of
muscle that works like a valve – preventing backflow.
∙ Releasing chyme slowly from the stomach gives the intestine more time
to mix the chyme with fluids from the liver and pancreas.
F. The Gigantic Small Intestine?
1. Small Intestine: A muscular tube that is about 2.5 cm in diameter and about 6m long.
- The length of the small intestine is so long to give a greater surface area for
nutrient absorption. The chemical breakdown of food is completed in the first
25 cm or so (the duodenum), the rest is for nutrient absorption.
2. Villi: Fingerlike projections that are covered with tiny nutrient-absorbing cells that
pass nutrients on to the bloodstream.
- If you flattened out the surface of the small intestine, it would be larger than
a tennis court! The inside wall of the small intestine is covered with villi.
∙ The villi extend into the chyme and absorb the nutrients that then
enter the bloodstream.
3. Most chemical digestion takes place in the small intestine.
4. Chyme moves very slowly through the small intestine by peristalsis.
5. Enzymes produced in the small intestine and the pancreas help digest the proteins,
carbohydrates, and fats.
G. The Pancreas
1. Pancreas: A fish-shaped organ located between the stomach and small intestine.
- The pancreas makes pancreatic juice that flows into the small intestine.
- The juice contains digestive enzymes and bicarbonate that neutralizes the
acid in chyme.
∙ Without bicarbonate, acids would damage the lining of the
intestine and prevent enzymes form doing their work.
2. The pancreas also functions as a part of the endocrine system, making hormones
that regulate blood sugar.
H. The Liver and Gallbladder
1. Liver: A large reddish brown organ that helps with digestion.
- Your liver is located toward your right side, slightly higher than your stomach.
- Your liver has several important jobs:
1. Bile: The green liquid your liver makes that is used in fat digestion.
2. Your liver stores nutrients.
3. Your liver breaks down toxic substances in the blood.
4. Your liver makes cholesterol for cell membranes.
- If three-fourths of the liver were removed, the rest would go on working
and would eventually grow to replace the part that was removed.
2. Bile Breaks Up Fat
- Gallbladder: A small baglike organ that temporarily stores the bile made
by the liver.
- Bile is squeezed from the gallbladder into the small intestine, where it
breaks up large fat droplets into very small droplets.
3. Storing Nutrients and Protecting the Body
- After nutrients are broken down, they are absorbed into the bloodstream
and carried through the body.
- Nutrients not needed right away are stored in the liver and released into
the bloodstream as needed.
4. The liver, gallbladder, and pancreas are linked to the small intestine, but food does
not move through them.
I. The End of the Line
1. Whatever can’t be absorbed into the blood gets pushed into the large intestine.
2. Large Intestine: The organ of the digestive system that stores, compacts, and then
eliminates indigestible material from the body.
- It is about 7.5 cm wide and 1.5 m long & is the large intestine is the final
organ of digestion. Bacteria here help make certain vitamins (like vitamin K)
3. In the Large Intestine
- Undigested material enters the large intestine as a soupy mixture and the
large intestine reabsorbs most of the water in the mixture.
- Feces (stool): The solid dry mass of undigested material that leaves the
body – after the watery portion is reabsorbed.
- Cellulose: A carbohydrate found in whole grains, fruits, and vegetables
that humans cannot digest. (AKA: Fiber)
∙ Fiber keeps the stool soft and keeps things moving through the
large intestine.
- Feces and other human wastes contain microorganisms and other
substances that can contaminate drinking water. Every time you flush a
toilet, the water and wastes go through the sewer to a sewage treatment
plant. Here the disease-causing microorganisms are removed, and the
clean water is released back to river, lakes, and streams.
4. A Way Out
- Rectum: Last section of the large intestine. (stores feces until they are expelled)
- Anus: An opening that feces pass through to the outside of the body.
∙ It takes about 24 hours for food to go from the mouth to the anus.
J. External & Internal Stimuli Responses
1. External Responses
- Smell: Smelling food can cause gastric juices to be released in the stomach
resulting in contractions and hunger.
- Eating: Lots of acidic foods can lead to indigestion and ulcers.
2. Internal Responses
- Hunger: The hunger center is located in the hypothalamus of the brain. It is
stimulated by the level of circulating nutrients (mostly glucose). When blood
levels of the nutrients are low, the hunger center is stimulated to send out nerve
impulses that lead to stomach contractions.
- Thirst: When water loss is greater than water gain the body reaches a state of
dehydration and dehydration stimulates the thirst reflex.
- Vomiting: Vomiting is actually a reflex triggered by a signal from the brain. The
signal to vomit can be stimulated by smells, taste, various illnesses, emotions
(such as fear), pain, injury, infection, food irritation, dizziness, and motion.
K. Problems in the Digestive System
1. Disorders of the digestive system are frequently related to eating behaviors, but
some are caused by disease.
- Heartburn: A burning sensation in the chest, just behind the sternum.
∙ Sphincters: Bands of muscle that block off the stomach at either end.
∙ Occasionally, backflow of chyme from the stomach to the
esophagus causes a burning pain in the chest called heartburn.
∙ Eating too much, eating right before going to bed, and eating
very acidic foods sometimes causes heartburn.
- Constipation: When bowel movements become difficult and less frequent.
∙ Some constipation is caused by the intestines not working properly
and other types are caused by diet, hormones or medications.
∙ Often from not enough fiber, not enough water, or decreased
physical activity.
- Diarrhea: When bowel movements are frequent and watery.
∙ Diarrhea occurs when too little water is removed from digested
food in the large intestine. (too much water)
∙ Diarrhea may cause dehydration and is especially dangerous for
infants and small children.
- Colon Cancer: A serious disease of the digestive tract that can lead to death.
∙ The colon is the long tubular portion of the large intestine.
∙ Tumors in the colon interfere with the normal functioning of organs.
∙ Tumors can also break away and start tumors in other areas in the body.
- Stomach (Gastric) Ulcer: An open sore in the stomach lining.
∙ Gastric ulcers are often caused by bacteria and can be treated
successfully with antibiotics.
∙ A high-fat diet, smoking, caffeine, and alcohol may make this
condition worse.
II.
The Urinary (Excretory) System
As your body performs that chemical activities that keep you alive, waste products such as
carbon dioxide and nitrogen are produced.
Excretion: The process of removing wastes and excess products from the body. Humans must get rid
of not only digestive waste but metabolic waste as well (from cells – water, urea, CO2, salts…)
Three of your body systems are involved in excretion:
1. Skin – releases waste products and water when you sweat.
2. Lungs – expel carbon dioxide and water when you exhale.
3. Urinary System – removes waste products from your blood.
NOTE: The digestive system is not involved in excretion because the term excretion is
used only when substances must pass through a membrane in order to leave the body.
A. Additional Functions of the Urinary System
1. Concentrating Urine
2. Regulating Electrolytes – The kidneys excrete and re-absorb electrolytes under the
influence of certain hormones.
3. Maintaining acid-base homeostasis (pH balance)
B. Cleaning the Blood
- As blood travels through the tissues, it collects all of the waste products produced
by the body’s cells. Your blood is like a supply train that comes into a town to
drop off supplies and take away garbage.
-
If the cells in your body cannot get rid of their waste products, they can actually be
poisoned.
Your urinary system removes waste materials from your blood so that the blood
can transport nutrients again.
When the body uses the amino acids from proteins in food, it sometimes must
remove the nitrogen groups. When this happens, ammonia is produced. Ammonia
is poisonous to our bodies. The body quickly converts the ammonia to urea
through chemical reactions. Urea is soluble in water and can be removed from the
body through urine.
C. Flow-Through Filters
- Kidney: A pair of bean-shaped organs that constantly clean the blood (removes
many harmful substances from the blood.)
∙ Your kidneys filter about 2,000 L of blood each day.
∙ Your body only holds 5.6 L of blood, so your blood cycles through the
kidneys about 350 times a day.
- Nephron: A microscopic filter in the kidney that removes a variety of harmful
substances from the blood.
∙ There are about 1 million of these microscopic filters in the kidneys.
∙ Nephrons remove a variety of harmful substances from the body.
∙ The most important of these substances is urea, which contains nitrogen
and is formed when cells use protein for energy.
- How the Kidneys Filter Blood
1. A large artery brings blood into each kidney.
2. Tiny blood vessels branch off the main artery and pass through part of
each nephron.
3. Water and other mall substances, such as glucose, salts, amino acids, and
urea, are forced out of the blood vessels and into the nephrons.
4. As these substances flow through the nephrons, most of the water and some
nutrients are moved back into blood vessels that wrap around the nephrons.
A concentrated mixture of waste materials is left behind in the nephrons.
5. The cleaned blood, now with slightly less water and much less waste
material, leaves each kidney in a large vein to recirculate in the body.
6. The yellow fluid that remains in the nephrons is called urine. Urine
leaves each kidney through a slender tube called the ureter and flows into
the urinary bladder, where it is stored.
7. Urine leaves the body through another tube called the urethra. Urination
is the process of expelling urine from the body.
- Urine: A concentrated mixture of waste materials that forms in the nephrons of the kidney.
- Ureter: A slender tube in which urine leaves the kidneys.
- Urinary Bladder: A baglike organ that stores urine until it can be eliminated
through the urethra.
- Urethra: A tube in which urine leaves the body.
- Urination: The process of expelling urine from the body.
D. Water In, Water Out
- Our bodies take in water every day… so if we did not excrete an equal amount of
water, our bodies would swell up with all the excess.
- Losing water through sweat and urine is necessary to stay healthy, but how does the
body keep the water levels in the proper balance?
- The balance of liquids is controlled by chemical messengers in the body called hormones.
- If you lost a kidney to disease, you could still survive.
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-
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Sweat and Thirst.
∙ When you get hot, you lose more water in the form of sweat. The evaporation of
water from your skin cools you down. As the water content of the blood drops,
the salivary glands produce less saliva. This is one of the reasons you feel thirsty.
Antidiuretic Hormone
∙ When you get thirsty, other parts of your body react to the water shortage.
∙ Antidiuretic Hormone (ADH): A hormone released that signals the kidneys
to take back water from the nephrons and return it to the bloodstream, thereby
making less urine.
∙ When your blood is too watery, smaller amount of ADH are released.
The kidneys react by allowing more water to stay in the nephron and
leave the body as urine.
Diuretics
∙ Diuretic: A substance that causes the kidneys to make more urine, which
decreases the amount of water in the blood.
∙ So instead of giving your body more water, caffeinated beverages cause
additional water to be lost in urine.
E. External & Internal Stimuli Responses
1. External Responses
- Urinary Infections: The body’s response to foreign bacteria (usually E. coli).
The body tries to fight the infection causing swelling and irritation.
2. Internal Responses
- Urination: The need to urinate arises when the volume of urine is high in the
urinary bladder and the nerves signaling to the brain increase and the
sensation for urinating increases.
- Kidney Stones: They form when a change occurs in the normal balance of
water, salts, minerals, and other things found in urine. The most common
cause of kidney stones is not drinking enough water.
F. Urinary System Ailments
- Since the urinary system regulates body fluids and removes wastes from the blood,
any malfunction can become life-threatening.
1. Urinary (Bacterial) Infections: Bacteria can get into the bladder and ureters through the
urethra and cause painful infections. It is important to treat such as an infection early
because it could spread to the kidneys and lead to permanent damage to the nephrons.
2. Kidney Stones: Result from stones in the ureter – solid concretions formed in the
kidneys from dissolved urinary minerals.
- Sometimes salts and wastes collect inside the kidneys and form kidney stones.
Kidney stones interfere with urine flow and cause pain. Most kidney stones
pass naturally from the body, but sometimes medical procedure is necessary.
3. Kidney Disease: Any collection of diseases with the kidneys.
- Damage to nephrons can prevent normal kidney functioning, leading to
kidney disease. If the kidneys do not function properly, a kidney machine
can be used to filter waste from the blood. Blood is pumped from an
artery into the forearm or wrist to a kidney machine, where it is filtered.
The cleaned blood is then pumped back into a vein in the arm.
4. Reduced Urinary Output (Urinary Retention): A lack of ability to urinate.
- It is a is a common complication of benign prostatic hyperplasia & can
also be caused by nerve dysfunction, constipation, infection or
medications.
- Can lead to bladder stones, loss of muscle tone, hydronesprosis
(congestion of the kidneys), or diverticula in the bladder wall.