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Chapter 24
Lecture Outline
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Exchanging Materials: Basic Principles
Large, multicellular organisms need a way to deliver oxygen and nutrients to the cells deep within tissues.
Several organ systems help deliver oxygen, nutrients to and remove wastes from cells.– Circulatory, lymphatic, respiratory, digestive, and
excretory systems
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The Cardiovascular System
Pumps blood around the body Consists of
– Blood Fluid tissue that transports materials and heat
– The heart A muscular pump that forces fluid through the body
– Vessels “Pipes” that move blood through the body Arteries carry blood from the heart to the tissues. Capillaries are small vessels that carry blood through
tissues. Veins carry blood from the tissues to the heart.
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The Nature of Blood
Consists of – Several types of cells
Called the formed elements
– Plasma Contains different kinds of dissolved molecules
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Formed Elements
Red blood cells– Lack a nucleus– Contain hemoglobin– Transport oxygen and carbon dioxide– Carbonic anhydrase converts carbon dioxide to
bicarbonate that can be dissolved in the blood.– Anemia is a lack of oxygen resulting from a lack
of red blood cells.
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Formed Elements
White blood cells– Also called leukocytes– Lack hemoglobin– Have a nucleus– Include basophils, eosinophils, neutrophils,
lymphocytes, and monocytes– Defend the body against microorganisms,
damaging chemicals, and cancer
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Formed Elements
Platelets– Not whole cells– Fragments of white blood cells– Important in blood clotting
Collect at the site of a wound Release clotting factors
– Initiate a sequence of reactions that trap blood cells to form a clot
– Eventually the clots (scabs) are replaced by healthy, living tissue.
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Plasma
Liquid part of the blood Contains
– Salts that serve to Buffer and maintain blood pH Maintain osmotic balance
– Keeps the tissue fluid between cells at the right solute concentration so that it flows into the capillaries, maintaining blood pressure
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Plasma
Proteins– Antibodies and other immune proteins– Albumin to maintain osmotic balance
Transports bilirubin from degraded RBCs to the liver Accumulated bilirubin can cause jaundice
Nutrients– Amino acids– Sugars– Lipoproteins carry fats and cholesterol
Hormones
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Composition of Blood
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Functions of Blood
Transports molecules, cells – Oxygen, carbon dioxide– Nutrients– Waste products– Immune cells and antibodies– Hormones
Regulates temperature– If body temperature is too high, blood will be shunted to the
body surface to radiate heat.– If body temperature is too low, blood will be shunted to the
body core to conserve heat.
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The Heart
Pumps the blood Generates the pressure necessary to move
blood through vessels– Blood must flow to move nutrients to
tissues and waste away from tissues.– Heart must repeatedly contract in order to
keep blood moving.
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Mammalian Heart
Has four chambers with four valves– Two atria and two ventricles
Ventricles – Are larger and more muscular– Force blood through the arteries to the body– The aorta and pulmonary artery flow out of the
ventricles.Atria
– Are smaller with thinner walls– Pump blood into the ventricles
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Mammalian Heart
Atria and ventricles are separated by atrioventricular valves. – Valves ensure that the blood only flows in one
direction. Semilunar valves in the aorta and pulmonary
arteries– Act as “check valves” to prevent blood from flowing
back into the ventricles when they relax Damaged valves causes inefficient pumping.
– Detected as heart murmurs because some of the blood is being pushed backward
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The Anatomy of the Heart
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Mammalian Heart
Two different sides have different jobs– The right atrium receives blood from the body.– The right ventricle pumps the blood to the lungs.
Called pulmonary circulation Allows for the exchange of carbon dioxide and oxygen in
the lungs
– The left atrium receives blood from the lungs.– The left ventricle pumps blood to all other parts of
the body. Called systemic circulation Allows for the delivery of oxygen, nutrient, and waste
exchange in the tissues
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Pulmonary and Systemic Circulation
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Blood Vessels
The tubes that transport blood from one place to another in the body
Types of blood vessels– Arteries– Veins– Capillaries
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Arteries
Carry blood away from the heart Contraction of the ventricles increases the
pressure in the arteries.– Called systolic blood pressure
Relaxation of the ventricles decreases the pressure in the arteries.– Called diastolic blood pressure
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Arteries
Blood pressure readings include both types of blood pressure.– Systolic/diastolic– 120/80
Have thick, muscular, and elastic walls– Can stretch when pressure increases
Branch into arterioles to take blood throughout the body
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Veins
Collect blood from the capillaries and return it to the heart
Have very low pressure Walls not very muscular
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Veins
Have valves to prevent backflow– Dysfunctional valves cause varicose veins.
Contraction of leg muscles aids in pushing blood through veins.– Sitting or standing for a long time can cause
pooling of blood in the feet.Causes swellingCan cause fainting because the brain doesn’t
get enough blood
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The Structure of Arteries, Veins, and Capillaries
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Capillaries
Tiny vessels, one-cell thick– RBC go through capillaries single file
Have thin walls– Only one-cell thick– Allows materials to diffuse into and out of the blood– Allows liquid to be exchanged between the blood and tissue
fluid
Are numerous– All cells in the body have a capillary nearby.
Flow of blood through capillaries is slow– Allows time for diffusion and fluid exchange
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Capillaries
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The Lymphatic System
A second circulatory system A collection of thin-walled vessels
– Called lymph vessels– Branch throughout body and lymph organs
Functions– Moves fat from digestive system to blood stream– Transports excess fluid back to cardiovascular
system– Carries immune cells
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The Lymphatic System
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The Lymphatic System
Lymph– Fluid tissue that is moved through the lymph
organs via lymph vessels– Emptied into large veins near the heart– Moved through lymph vessels by muscle
contraction
Edema– Accumulation of fluid in tissues
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Lymph Organs
Lymph nodes– Filter lymph– Contain large numbers of white blood cells– Remove microorganisms and foreign particles from the
lymph– When an infection is active, the lymph nodes enlarge
Tonsils– Near the throat– Contain the tonsils and the adenoids– Filter pathogens that enter through the mouth and nose
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Lymph Organs
Spleen– Contains a large number of white blood cells– Filters the blood
Cleans out pathogens and dying RBCs
– Located just below the diaphragm
Thymus– Produces WBCs called T-lymphocytes– Most active in children– Shrinks as one ages
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Lymph Organs
Red bone marrow– Found in children’s bones– Reduced in adult bones– Produces RBCs, WBCs, and platelets
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The Respiratory System
Moves air into and out of the body Lungs
– Allow gas exchange between air and blood Trachea
– A tube that carries air into and out of the lung– Branches into bronchi then into bronchioles– Bronchioles end in alveoli– Alveoli are small sacs where gas exchange takes place
Air-transport pathway– Includes the nose, mouth, and throat– Pulls air into the trachea
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Respiratory Anatomy
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Breathing System Regulation
Breathing is the process of moving air into and out of the lungs.
Involves the diaphragm– A large muscle that separates the chest cavity (containing
lungs) from the abdominal cavity– When contracted, the diaphragm moves down
Creates negative pressure in the chest cavity Pulls air into the lungs
– When relaxed, the diaphragm resumes its normal position Generates positive pressure in the chest cavity Pushes air out of the lungs
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Breathing Movements
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Breathing During Exercise
Exercise increases the body’s demand for oxygen.– Requires faster gas exchange in lungs– Accomplished by
Increased breathing rate– Can involve greater diaphragm contraction
to pull in more air
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Breathing During Exercise
Can also involve contraction of abdominal muscles to fully empty the lungs– This happens when carbon dioxide concentration
increases in the blood and blood pH. Sensed by brain, then brain causes increased
contraction of the diaphragm and intercostal muscles
– Increased air exchange volume in each breath
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The Control of Breathing Rate
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Lung Function
Lungs are specialized so that blood and air can come very close together.– This facilitates gas exchange between them.– Blood flows through capillaries in the lungs that
come very close to the air in the alveoli.– Oxygen and carbon dioxide cross the alveoli and
capillary walls.– Therefore, the surface area of the alveoli must be
very large (collectively). This is why there are so many alveoli.
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The Association of Capillaries with Alveoli
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Lung Function
Gas exchange is facilitated by blood and air movement.– Blood enters the lungs high in carbon dioxide and
low in oxygen.– Air enters the lungs high in oxygen and low in
carbon dioxide.– Therefore, carbon dioxide diffuses from the blood
to the air and oxygen diffuses from the air to the blood.
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Disrupting Lung Function
Interfering with blood flow or gas exchange will reduce the efficiency of the organism.– A poorly pumping heart reduces the amount of
blood that is sent to the lungs.– Constriction of bronchioles (asthma) reduces the
amount of air that can enter the alveoli.– Reducing the number of alveoli (emphysema)
reduces the surface area for gas exchange.
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The Digestive System
Responsible for processing and distributing nutrients– Mechanical processing– Chemical processing– Nutrient uptake– Chemical alteration
Consists of – A muscular tube– Glands that secrete digestive juices
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The Digestive System
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Mechanical and Chemical Processing
The process of taking large pieces of food and breaking them down into individual molecules that can be absorbed
Mechanical processing– Chewing in the oral cavity generates a food bolus.
Increases surface area of foodAllows digestive enzymes greater access to
the food
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Mechanical and Chemical Processing
Salivary glands produce saliva containing some digestive enzymes.– Chewing mixes the food with the saliva.
Salivary amylase begins to break down starch.
– Tongue Tastes food Pushes food back toward throat
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Mechanical and Chemical Processing
Food bolus passes through the esophagus to the stomach
– Moves from mouth to the pharynx into the esophagus– Contractions of the pharynx move the food toward the
stomach.
In the stomach, food is churned.– Mixes food with digestive juices
Pepsin breaks down proteins.
– Low pH denatures proteins– The food then moves to the small intestine where chemical
breakdown is completed.
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Mechanical and Chemical Processing
Chemical processing in the small intestine– Also known as the duodenum– Receives digestive enzymes and bicarbonate ions
from the pancreas Digestive enzymes complete the chemical processing of
food. Bicarbonate neutralizes the low pH of the food coming
from the stomach.
– Receives bile from the liver by way of the gall bladder
Emulsifies fat into smaller fat globules Allows digestive enzymes greater access to the fats
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Mechanical and Chemical Processing
Finally, the remainder of the undigested food passes from the small intestine to the large intestine (colon).– 1.5 meters long– Water is reabsorbed.– Contains bacteria that utilize the undigested food
These bacteria produce vitamins that we need.
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Digestive Enzymes
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Nutrient Uptake
Once food is broken down into individual macromolecules, they can be absorbed into the bloodstream.– Absorption occurs through the lining of the small
intestine.– Requires a large surface area
The small intestine is very long (6 to 8 meters).The lining of the small intestine has fingerlike
projections called villi.
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Nutrient Uptake
Each villus contains – Several capillaries– A lymphatic vessel called a lacteal
Involves diffusion – Water and small ions move into blood via simple
diffusion.– Sugars and amino acids move into blood via
carrier proteins.– Fatty acids and glycerol enter intestinal cells
where they are built into fats and transported into the lacteals.
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Chemical Alterations: The Role of the Liver
The nutrient-rich blood leaves the intestine and goes straight to the liver.– Moves through the hepatic portal vein
In the liver– Enzymes modify the nutrient molecules.– Foreign organisms are filtered out.
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Chemical Alterations: The Role of the Liver
Toxic substances are detoxified– Ethyl alcohol– Plant toxins
Excess glucose is collected and stored as glycogen.
Excess amino acids are converted to – Other types of amino acids– Glucose and stored– Urea and sent to the kidneys
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The Excretory System (The Urinary System)
Responsible for the processing and elimination of metabolic waste– Urea– Toxic substances– Hydrogen ions– Water– Salts
Consists of– Kidneys– Ureters– Urinary bladder– Urethra
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The Urinary System
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Kidney Structure
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Kidney Function
In order to filter out waste, kidney must have a close association with bloodstream– Exchange of waste occurs across a surface– Requires large surface area
Glomerulus represents a large surface area
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Kidney Function
Major activities in kidney– Filtration
Blood enters glomerulus under pressure as the heart contracts.
Glomerular capillaries are porous.– Glucose, amino acids, ions, and water are pushed through
the pores into the nephron tubules.
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Kidney Function
Reabsorption– Not everything that is filtered into the nephron needs
to be excreted.– Some molecules are reabsorbed into capillaries
around the nephron. Amino acids, glucose, sodium
– Occurs mostly in the proximal convoluted tubule– Water is reabsorbed in the Loop of Henle.
Occurs because of osmotic gradients that exist in the kidney
Concentrates the urine and conserves water
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Kidney Function
Secretion– Additional waste is moved from the capillaries
around the nephron into the distal convoluted tubule.
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Specific Functions of the Nephron