Circulation Chapter 37 Part 2

37.7 Pressure, Transport, and Flow Distribution  Contracting ventricles put pressure on the blood, forcing it through a series of vessels • • • • •

Arteries carry blood from ventricles to arterioles Arterioles control blood distribution to capillaries Capillaries exchange substances Venules collect blood from capillaries Veins deliver blood back to heart

Human Blood Vessels

Fig. 37-17a, p. 648

outer coat

smooth muscle

basement membrane

endothelium

Artery

elastic tissue

elastic tissue

Fig. 37-17a, p. 648

Fig. 37-17b, p. 648

outer coat

smooth muscle rings basement over elastic tissue membrane endothelium Arteriole

Fig. 37-17b, p. 648

Fig. 37-17c, p. 648

basement membrane

endothelium Capillary (venules have a similar structure)

Fig. 37-17c, p. 648

Fig. 37-17d, p. 648

outer coat

smooth muscle, elastic fibers

basement membrane

endothelium

Vein valve

Fig. 37-17d, p. 648

Blood Pressure

 Blood pressure • The pressure exerted by blood on the walls of blood vessels • Highest in arteries, then declines through circuit • Rate of blood flow depends on the difference in blood pressure between two points, and resistance to flow

Blood Pressure in the Systolic Circuit

arteries

capillaries

arterioles

veins

venules Fig. 37-18, p. 648

Blood Flow

 Thick, elastic arteries smooth out variations in blood pressure during the cardiac cycle  Arterioles respond to signals from the autonomic and nervous systems, and to chemical signals, to direct blood flow to different parts of the body

Distribution of Cardiac Output in a Resting Person

100%

lungs

heart’s right half liver digestive tract kidneys skeletal muscle brain skin bone

cardiac muscle all other regions

heart’s left half 6%

21% 20% 15% 13% 9%

5% 3% 8% Fig. 37-19, p. 649

Controlling Blood Pressure  Blood pressure depends on total blood volume, how much blood the ventricles pump (cardiac output), and whether arterioles are constricted or dilated

 Receptors in the aorta and carotid arteries monitor blood pressure and send signals to the medulla, which regulates cardiac output and arteriole diameter

Measuring Blood Pressure

Animation: Measuring blood pressure

37.8 Diffusion at Capillaries, Then Back to the Heart  Capillary • A cylinder of endothelial cells, one cell thick • Capillary beds are diffusion zones, where blood exchanges substances with interstitial fluid • Hydrostatic pressure moves materials out (ultrafiltration) • Osmotic pressure moves water in (capillary reabsorption)

Fluid Movement at a Capillary Bed

blood to venule

high pressure causes outward flow

blood from arteriole

cells of tissue

inward-directed osmotic movement

B A

Fig. 37-21 (a-b), p. 650

Venous Pressure

 Venules deliver blood from capillaries to veins

 Veins deliver blood to the heart • Large-diameter, blood volume reservoirs • Valves help prevent backflow • Amount of blood in veins varies with activity level

Venous Valve Action

Fig. 37-22a, p. 651

venous valve Fig. 37-22a, p. 651

Fig. 37-22b, p. 651

blood flow to heart

valve open

valve closed

Fig. 37-22b, p. 651

Fig. 37-22c, p. 651

valve closed

valve closed

Fig. 37-22c, p. 651

37.7-37.8 Key Concepts

Blood Vessel Structure and Function  The heart pumps blood rhythmically, on its own

 Adjustments at arterioles regulate how blood volume is distributed among tissues  Exchange of gases, wastes, and nutrients between the blood and tissues takes place at capillaries

37.9 Blood and Cardiovascular Disorders  Red blood cell disorders • Anemias, beta-thalassemias, polycythemia

 White blood cell disorders • Infectious mononucleosis, leukemias, lymphomas

 Clotting disorders • Hemophilia, thrombus, embolus

Blood and Cardiovascular Disorders  Atherosclerosis • Buildup of lipids in the arterial wall that narrows the lumen, may rupture and trigger heart attack

Fig. 37-23a, p. 652

wall of artery, cross-section

unobstructed lumen of a normal artery

Fig. 37-23a, p. 652

Fig. 37-23b, p. 652

atherosclerotic plaque

blood clot sticking to plaque

narrowed lumen

Fig. 37-23b, p. 652

Clogged Coronary Arteries

coronary artery

Fig. 37-24a, p. 653

aorta

coronary artery blockage location of a shunt made of a section taken from one of the patient’s other blood vessels

Fig. 37-24b, p. 653

Blood and Cardiovascular Disorders

 Hypertension – a silent killer • Chronic blood pressure above 140/90

 High blood pressure and atherosclerosis increase the risk of heart attack and stroke

Blood and Cardiovascular Disorders  Arrhythmias – abnormal heart rhythms • EKGs record electrical activity of cardiac cycle

one normal heartbeat

0 0.2 0.4 0.6 0.8 a time (seconds) bradycardia (here, 46 beats per minute) b tachycardia (here, 136 beats per minute) c ventricular fibrillation

d Fig. 37-25, p. 653

Risk Factors  Cardiovascular disorders are the leading cause of death in the United States  Risk factors • Tobacco smoking, family history, hypertension, high cholesterol, diabetes mellitus, obesity, age, physical inactivity, gender

37.9 Key Concepts

When the System Breaks Down

 Cardiovascular problems include clogged blood vessels or abnormal heart rhythms  Some problems have a genetic basis; most are related to age or life-style

37.10 Interactions With the Lymphatic System

 Vessels and organs of the lymphatic system interact closely with the circulatory system  Lymph vascular system • Lymph capillaries and vessels that collect water and solutes from interstitial fluid and deliver them to the circulatory system

Three Functions of the Lymph Vascular System  Returns fluids and plasma proteins that leak out of capillaries to the circulatory system  Delivers fats absorbed from the small intestine to the blood

 Transports cellular debris, pathogens, and foreign cells to lymph nodes

Lymphoid Organs and Tissues

 Lymph nodes • Organs that filter lymph before it enters blood and identify pathogens

 Tonsils in throat and adenoids in nasal cavity • Respond to inhaled pathogens

Lymphoid Organs and Tissues

 Spleen • Filters pathogens and worn out blood cells from blood

 Thymus gland • Matures T lymphocytes essential to the immune system

Components of the Lymphatic System

Fig. 37-26a, p. 654

Tonsils Defense against bacteria and other foreign agents Right Lymphatic Duct Drains right upper portion of the body Thymus Gland Site where certain white blood cells acquire means to chemically recognize specific foreign invaders Thoracic Duct Drains most of the body Spleen Major site of antibody production; disposal site for old red blood cells and foreign debris; site of red blood cell formation in the embryo Some Lymph Vessels Return excess interstitial fluid and reclaimable solutes to the blood

Some Lymph Nodes Filter bacteria and many other agents of disease from lymph

Bone Marrow Marrow in some bones is production site for infectionfighting blood cells (as well as red blood cells and platelets) Fig. 37-26a, p. 654

Fig. 37-26b, p. 654

lymph capillary

interstitial fluid flaplike “valve” made of overlapping cells at tip of lymph capillary

capillary bed

Fig. 37-26b, p. 654

Fig. 37-26c, p. 654

lymph trickles past organized arrays of lymphocytes

valve (prevents backflow) Fig. 37-26c, p. 654

Animation: Human lymphatic system

Animation: Lymph vascular system

37.10 Key Concepts

Links With the Lymphatic System

 A lymph vascular system delivers excess fluid that collects in tissues to the blood  Lymphoid organs cleanse blood of infectious agents and cellular debris

Animation: Capillary forces

Animation: Examples of ECGs

Animation: Vein function

Animation: Vessel anatomy

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