29 Lecture Ppt

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 29 Circulation and Cardiovascu lar Systems

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Transcript of 29 Lecture Ppt

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Chapter 29Circulation and Cardiovascular

Systems

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A Circulatory System Helps Maintain Homeostasis

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29.1 A circulatory system serves the needs of cells

The circulatory system transports oxygen and nutrients, such as glucose and amino acids, to the cells It picks up wastes, which are later excreted from the

body by the lungs or kidneys Both gas exchange and nutrient-for-waste

exchange occur across the walls of the smallest blood vessels, capillaries No cell in the body of an animal is far from a capillary

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Figure 29.1 Exchanges of gases, nutrients, and wastes takes place across capillary walls

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29.2 Some invertebrates do not have a circulatory system

Cnidarians, such as hydras, and flatworms, such as planarians, do not have a circulatory system

In a hydra The cells are either part of an external layer, or they line

the gastrovascular cavity In either case, each cell is exposed to water and can

independently exchange gases and get rid of wastes In a planarian

Trilobed gastrovascular cavity branches throughout the small, flattened body

No cell is very far from one of the three digestive branches, so nutrient molecules can diffuse from cell to cell

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Figure 29.2 Invertebrates with a gastrovascular cavity

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29.3 Other invertebrates have an open or a closed circulatory system

There are two types of circulatory fluid: Blood - always contained within blood vessels Hemolymph - a mixture of blood and tissue fluid that flows into a body

cavity Open circulatory system - found in arthropods and molluscs

Heart pumps hemolymph via vessels into tissue spaces and eventually hemolymph drains back to the heart

Slow delivery of oxygen and nutrients is sufficient for a sluggish animal (clam)

A grasshopper has colorless blood and doesn’t depend on its open circulatory system to deliver oxygen to its muscles

Tracheae open to outside and take oxygen directly to flight muscles Closed circulatory system - found in annelids (earthworms)

Heart pumps blood, which usually consists of cells and plasma, into a system of blood vessels and valves prevent the backward flow of blood

Blood moves into capillaries, for exchanges with tissue fluid Blood then moves from small veins into the dorsal blood vessel (a vein) This dorsal blood vessel returns blood to the heart for repumping

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Figure 29.3A Open circulatory system in a grasshopper

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Figure 29.3B Closed circulatory system in an earthworm

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29.4 All vertebrates have a closed circulatory system

Two different circulatory pathways in vertebrates Single-loop: heart only pumps blood to gills Two-circuit: systemic circuit - heart pumps blood to all parts of the body

except for the lungs; the pulmonary circuit - heart pumps blood to the lungs Fishes - heart has a single atrium and a single ventricle

Blood is fully enriched with oxygen when it leaves gills, the respiratory organ for aquatic organisms

Amphibians and Reptiles - single ventricle pumps blood in the pulmonary circuit to the lungs Also pumps blood in the systemic circuit to the rest of the body Although both O2 -rich and O2 -poor blood enter the single ventricle, it is kept

separate O2 -poor blood is pumped out of the ventricle to the lungs before O2-rich blood

enters and is pumped to the systemic circuit Birds and Mammals

Two atria and two ventricles in the heart and the complete separation of the pulmonary and systemic circuits

Right ventricle pumps blood under pressure to the lungs, and the larger left ventricle pumps blood under pressure to the rest of the body

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Figure 29.4A Single-loop circulatory pathway in fishes

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Figure 29.4B Two-circuit pathway in amphibians and most reptiles

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Figure 29.4C Complete separation of pulmonary and systemic circuits in birds, mammals, and some reptiles

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The Mammalian Cardiovascular System Consists of the Heart

and Blood Vessels

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29.5 The mammalian heart has four chambers

All vertebrates have a closed circulatory system, called a cardiovascular system because it consists of a heart (cardio) and a system of blood vessels (vascular) Septum divides the heart into left and right sides

Right side of heart pumps O2-poor blood to lungs, and the left side pumps O2-rich blood to tissues

Each side has two chambers Upper, thin-walled chambers are atria (sing., atrium) Lower chambers are thick-walled ventricles

Atria receive blood; ventricles pump blood away from heart29-15

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Heart Valves

Atrioventricular valves - between the atria and ventricles

Semilunar valves - between the ventricles and their attached vessels

After the blood passes through the right atrioventricular valve, the right ventricle pumps it through the pulmonary semilunar valve into the pulmonary trunk and pulmonary arteries that take it to the lungs Pulmonary veins bring O2-rich blood back to the left atrium

After the blood passes through the left atrioventricular valve, the left ventricle pumps it through the aortic semilunar valve into the aorta, which takes it to the tissues Heart murmur is often due to leaky atrioventricular valves,

which allow blood to pass back into the atria after they have closed 29-16

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Figure 29.5 Structure of the heart

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29.6 The heartbeat is rhythmic The average human heart contracts, or beats, about 70 times a

minute, or 2.5 billion times in a lifetime Each heartbeat, called the cardiac cycle, can be divided into three

phases The atria contract (while the ventricles relax) The ventricles contract (while the atria relax) All chambers rest

Systole refers to contraction of the heart chambers, and the word diastole refers to relaxation of these chambers

When the heart beats, the familiar “lub-dub ” sound is heard as the valves of the heart close Pulse - wave effect that passes down walls of arterial blood vessels

following ventricular systole Rhythmic contraction of heart is due to cardiac conduction

system The SA (sinoatrial) node initiates the heartbeat every 0.85 seconds

and is called the cardiac pacemaker An electrocardiogram (ECG) is a recording of the electrical changes

that occur in the heart during a cardiac cycle29-18

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Figure 29.6A The phases of a heartbeat

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Figure 29.6B Conduction system of the heart

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29.7 Blood vessel structure is suited to its function

Arteries (and arterioles) - carry blood away from the heart to the capillaries Arteries have a much thick wall with elastic tissue that allows

arteries to expand and accommodate the sudden increase in blood volume that results after each heartbeat

Smaller arteries branch into a number of arterioles Capillaries - permit exchange of material with tissues

Extremely narrow (8–10 mm wide) and have thin walls composed of single layer of epithelium with basement membrane

The thin walls of a capillary facilitate capillary exchange Veins (and venules) - return blood from the capillaries to

the heart Venules (small veins) - drain blood from the capillaries; then join to

form a vein Veins often have valves that allow blood to flow only toward the

heart when open and prevent the backward flow of blood when closed 29-21

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Figure 29.7A Types of blood vessels

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Figure 29.7B Anatomy of a capillary bed

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29.8 Blood vessels form two circuits in mammals

The Pulmonary Circuit O2-poor blood from all regions of body collects in right atrium and then

passes into right ventricle, which pumps it into the pulmonary trunk Pulmonary trunk divides into the right and left pulmonary arteries, which

carry blood to the lungs As blood passes through pulmonary capillaries, carbon dioxide is given

off and oxygen is picked up O2-rich blood returns to left atrium of through pulmonary veins

The Systemic Circuit Aorta and the venae cavae (sing., vena cava ) are the major blood

vessels To trace the path of blood to any organ in the body, start with the left

ventricle, then go the aorta, then the proper branch of the aorta, the organ, and the vein returning blood to the vena cava, which enters the right atrium

Portal systems begin and end in capillaries Hepatic portal system takes blood from the intestines to the liver

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Figure 29.8 Path of blood in the body

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29.9 Blood pressure is essential to the flow of blood in each circuit

Blood pressure is normally measured on the brachial artery of the upper arm A blood pressure reading consists of two numbers that represent

systolic and diastolic pressures, respectively Systolic pressure results from blood being forced into the arteries

during ventricular systole Diastolic pressure is the pressure in the arteries during ventricular

diastole Blood pressure accounts for the flow of blood from the

heart to the capillaries As blood flows from the aorta into the various arteries and

arterioles, blood pressure falls Blood pressure in the veins is low and cannot move blood back

to the heart, especially from the limbs Venous return depends upon three factors:

Skeletal muscle contraction, presence of valves in veins, and respiratory movements

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Figure 29.9A Velocity and blood pressure are related to the cross-sectional area of the blood vessels

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Figure 29.9B How a valve affects the movement of blood in a vein

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APPLYING THE CONCEPTS—HOW BIOLOGY IMPACTS OUR LIVES 29.10 Blood vessel deterioration results in cardiovascular disease

In U.S., about 20% of population suffers from hypertension, high blood pressure Heredity and lifestyle contribute to hypertension

Hypertension is often seen in individuals who have atherosclerosis, which occurs when plaque protrudes into the lumen of a vessel and interferes with the flow of blood

Plaque can cause a clot to form on the irregular arterial wall As long as the clot remains stationary, it is called a thrombus, but

when and if it dislodges and moves along with the blood, it is called an embolus

A stroke often occurs when a small cranial arteriole bursts or is blocked by an embolus

Heart attack - when a coronary artery is completely blocked, a portion of the heart muscle dies due to lack of oxygen

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APPLYING THE CONCEPTS—HOW BIOLOGY IMPACTS OUR LIVES

29.11 Cardiovascular disease can often be prevented

The Don’ts Smoking - When a person smokes, nicotine enters the

bloodstream and causes the arterioles to constrict and the blood pressure to rise

Drug Abuse - Stimulants, such as cocaine and amphetamines, can cause an irregular heartbeat and lead to heart attacks and strokes

Weight Gain - in persons who are more than 20% above the recommended weight more tissues require servicing, and the heart sends the extra blood out under greater pressure

The Dos Healthy Diet - Physicians advise people to replace harmful

saturated fats and trans fats with healthier ones, such as monounsaturated fats (olive and canola oils) and polyunsaturated fats (corn, safflower, and soybean oils)

Cholesterol Profile - Starting at age 20, all adults are advised to have their cholesterol levels tested at least every five years

Exercise - People who exercise are less apt to have cardiovascular disease

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Figure 29.11 Plaque buildup in a coronary artery

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Blood Has Vital Functions

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29.12 Blood is a liquid tissue

Blood’s numerous functions include the following: Transports substances to and from the capillaries, where

exchanges with tissue fluid take place Helps defend the body against invasion by pathogens (e.g.,

disease-causing viruses and bacteria) Helps regulate body temperature Forms clots, preventing a potentially life-threatening loss of

blood Blood has two main portions

Plasma - composed mostly of water (90–92%) and proteins (7–8%) Also contains smaller quantities of many types of molecules,

including nutrients, wastes, and salts Formed elements - red blood cells, white blood cells, and

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Types of Blood Cells

Red blood cells (erythrocytes) - transport oxygen using hemoglobin, which contains iron, and combines loosely with oxygen

White blood cells (leukocytes) - help fight infections Neutrophils, which are amoeboid, squeeze through the capillary

wall and enter the tissue fluid, where they engulf foreign material Monocytes appear and are transformed into macrophages,

large phagocytizing cells that release white blood cell growth factors

Lymphocytes play important role in fighting infection T cells attack infected cells that contain viruses B cells - produce antibodies

Each B cell produces just one type of antibody, which is specific for one type of antigen

An antigen, which is most often a protein but sometimes a polysaccharide, causes the body to produce an antibody to combine with the antigen

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Figure 29.12 Composition of blood

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29.13 Blood clotting involves platelets

Platelets result from fragmentation of large cells in the bone marrow called megakaryocytes Blood contains 150,000–300,000 platelets per mm3

When a blood vessel in the body is damaged platelets clump at the site of the puncture and partially seal the leak Platelets and the injured tissues release a clotting factor called prothrombin

activator that converts prothrombin to thrombin Thrombin acts as an enzyme that severs two short amino acid chains from

each fibrinogen molecule These activated fragments then join forming long threads of fibrin that wind

around the platelet plug in the damaged area of the blood vessel and provide the framework for the clot

If blood is allowed to clot in a test tube, a yellowish fluid develops above the clotted material, called serum Contains all the components of plasma, except fibrinogen

Hemophilia is a well-known, inherited clotting disorder Due to the absence of a particular clotting factor, the slightest bump can cause

internal bleeding

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Figure 29.13 Blood clotting

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APPLYING THE CONCEPTS—HOW SCIENCE PROGRESSES

29.14 Adult stem cells include blood stem cells

A stem cell is a cell that is capable of becoming different types of cells While embryonic stem cells possess the ability to become

virtually any cell type, adult stem cells are not quite as versatile because they can become only certain other types of cell

Adult stem cells have been identified in many tissues, including the liver, skin, muscle, and even within the brain, but the richest source is in the red bone marrow Adult stem cells from bone marrow are used to treat many white

blood cell and immune system disorders, including leukemia, certain blood cancers, and anemia

Like any organ transplant, a bone marrow transplant poses the risk of rejection

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Figure 29.14 Hematopoietic cells (adult stem cells in red bone marrow) produce cells that become the various types of blood cells.

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29.15 Capillary exchange is vital to cells

Capillary exchange occurs between a systemic capillary and tissue fluid, the fluid between the body’s cells Two forces control movement of fluid through capillary wall

Blood pressure, which tends to cause water to move out of a capillary into the tissue fluid

Osmotic pressure, which tends to cause water to move from the tissue fluid into a capillary

Red blood cells and almost all plasma proteins remain in the capillaries Fluid and other substances that leave a capillary contribute to the

tissue fluid At the venous end of a capillary, blood pressure has fallen so

osmotic pressure is greater than blood pressure, and water tends to move into the capillary Some excess tissue fluid is always collected by the lymphatic

capillaries Tissue fluid contained within lymphatic vessels is called lymph

Lymph is returned to the systemic venous blood when the major lymphatic vessels enter the subclavian veins in the shoulder region

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Figure 29.15A Capillary exchange

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Figure 29.15B A lymphatic capillary bed lies near a blood capillary bed

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29.16 Blood types must be matched for transfusions

ABO System Presence or absence of type A and type B

antigens on red blood cells determines a person’s blood type In the ABO system, there are four types of blood:

A, B, AB, and O Type O blood has no antigens on the red blood cells and

is sometimes called the universal donor

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Rh System and Erythroblastosis Fetalis

Rh System Another important antigen in matching blood types is the Rh

factor 85% of the U.S. population have this particular antigen on red

blood cells and are called Rh-positive Erythroblastosis Fetalis

During pregnancy, if the mother is Rh-negative and the father is Rh-positive, the child may be Rh-positive

Rh-positive red blood cells may begin leaking across the placenta into the mother’s cardiovascular system, since placental tissues normally break down before and at birth

The mother produces anti-Rh antibodies, which may cross the placenta and destroy the child’s red blood cells during a subsequent pregnancy

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Figure 29.16A No agglutination occurs when the donor and recipient have the same type blood

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Figure 29.16B Agglutination occurs because blood type B has anti-A antibodies in the plasma

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Connecting the Concepts:Chapter 29

It is possible to relate the type of cardiovascular system to the lifestyle of an animal Some small, aquatic animals have no cardiovascular system—

external water passing in and out of a gastrovascular cavity is sufficient to meet the needs of their cells

Grasshoppers have an open circulatory system, but they utilize tracheae to deliver oxygen directly to their muscles

We traced the evolution of the two-circuit circulatory pathway in vertebrates and saw that a two-circuit pathway allows blood to pass to the lungs and to the tissues under pressure This is particularly useful in birds and mammals, which maintain

a warm body and an active way of life Body fluids make ideal culture media for the growth of infectious

parasites, and these fluids often have ways to ward off an invasion. You already know that white blood cells are involved in these endeavors

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