Circulation

Chapter 34

34.1 Circulatory Systems

Circulatory system

• Usually blood, blood vessels, and heart

• Moves substances to and from interstitial fluid

faster than diffusion could move them

Interstitial fluid fills spaces between cells

• Exchanges substances with cells and blood

• Usually across blood capillaries

Open Circulatory System

Found in some invertebrates

• Blood mingles with tissue fluids

Closed Circulatory System

Found in vertebrates and some invertebrates

• Confines blood inside a heart and blood vessels

Vertebrate Circulatory Systems

Closed systems differ in whether blood flows

through one or two circuits of blood vessels and

how many chambers divide the heart’s interior

Birds and mammals have hearts with four

chambers and two separate circuits

• Pulmonary circuit

• Systemic circuit

Vertebrate Circulatory Systems

Fig. 34.3a, p.561

Fig. 34.3b, p.561

Fig. 34.3c, p.561

Fig. 34.3d, p.561

Key Concepts:

OVERVIEW OF CIRCULATORY SYSTEMS

Many animals have either an open or a closed

circulatory system that transports substances to

and from all body tissues

34.2 Blood

Blood

• Fluid connective tissue consisting of plasma,

blood cells, and platelets

Plasma

• Mostly water in which diverse ions and molecules

are dissolved

Blood Cells

Red blood cells (erythrocytes)

• Contain hemoglobin

• Rapidly transport oxygen (and carbon dioxide)

• Have no nucleus when mature

White blood cells (leukocytes)

• Tissue maintenance and repair

• Defenses against pathogens

Platelets

Platelets function in blood clotting

Platelets and all blood cells arise from stem cells

in bone marrow

Components of Human Blood

Cellular Components of Human Blood

34.3 Blood Disorders

Red blood cell disorders

• Anemias, polycythemia

White blood cell disorders

• Mononucleosis, leukemias

34.4 Blood Typing

Recognition proteins (self markers) on red blood

cell surfaces identify an individual’s blood types

The body attacks cells that bear nonself markers

ABO Blood Typing

Helps match blood of donors and recipients to

avoid blood transfusion problems (agglutination)

Rh Blood Typing

Helps prevent

problems that may

arise when maternal

and fetal Rh blood

types differ

Fig. 34.9a, p.565

Fig. 34.9b, p.565

Key Concepts:

BLOOD COMPOSITION AND FUNCTION

Vertebrate blood is a fluid connective tissue

It consists of red blood cells, white blood cells,

platelets, and diverse substances dissolved in

plasma, the transport medium

Red blood cells function in gas exchange; white

blood cells and platelets help defend the tissues

34.5 Human Cardiovascular System

Pulmonary circuit

• Oxygen-poor blood flows from the heart’s right

half to the lungs, picks up oxygen, then flows to

the heart’s left half

Systemic circuit

• Oxygen-rich blood flows from the heart’s left half

to all body tissues, delivers oxygen, then flows to

the heart’s right half

Pulmonary and Systemic Circuits

Fig. 34.10a, p.566

Fig. 34.10b, p.566

Major Blood Vessels

Fig. 34.11, p.567

Jugular Veins Receive blood from brain and from tissues of head

Femoral Vein Carries blood away from the thigh and inner knee

Carotid Arteries Deliver blood to neck, head, brain

Femoral Artery Delivers blood to the thigh and inner knee

Iliac Arteries Deliver blood to pelvic organs and lower abdominal wall

Abdominal Aorta Delivers blood to arteries leading to the digestive tract, kidneys, pelvic organs, lower extremities

Renal Artery Delivers blood to kidneys, where its volume, composition are adjusted

Brachial Artery Delivers blood to upper extremities; blood pressure measured here

Coronary Arteries Service the incessantly active cardiac muscle cells of heart

Pulmonary Arteries Deliver oxygen-poor blood from the heart to the lungs

Ascending Aorta Carries oxygenated blood away from heart; the largest artery

Iliac Veins Carry blood away from the pelvic organs and lower abdominal wall

Inferior Vena Cava Receives blood from all veins below diaphragm

Renal Vein Carries processed blood away from kidneys

Hepatic Vein Carries blood that has passed through small intestine and then liver

Pulmonary Veins Deliver oxygenated blood from the lungs to the heart

Superior Vena Cava Receives blood from veins of upper body

Transport and Exchange

Most blood flows through only one capillary

system

Blood in intestinal capillaries later flows through

liver capillaries

Liver metabolizes or stores nutrients and

neutralizes some bloodborne toxins

Maintaining Homeostasis

34.6 The Human Heart

A four-chambered, double pump

• Two halves, each with two chambers: an atrium

and a ventricle

Fig. 34.13a, p.568

Fig. 34.13b, p.568

Fig. 34.13c, p.568

The Cardiac Cycle

All heart chambers undergo rhythmic relaxation

(diastole) and contraction (systole)

• Each atrium expands as blood fills it and opens a

valve to a ventricle

• Both ventricles fill as the atria contract

• Ventricles contract, forcing blood into the aorta

and pulmonary arteries

• Ventricular force powers movement of blood

through blood vessels

The Cardiac Cycle

Fig. 34.14 p.569

a Atria fill.

Fluid pressure

opens the AV

valves, blood

flows into the

ventricles.

d Ventricles

relax. Semilunar

valves

close as atria

begin filling

for the next

cardiac cycle.

c Ventricles

contract. Semi-

lunar valves

open. Blood

flows into aorta

and pulmonary

artery.

b Next, atria

contract. As

fluid pressure

rises in the

ventricles, AV

valves close.

Cardiac Muscle

Cardiac Conduction System

SA node in right atrium wall is functionally linked

by long bundles of conducting fibers to AV node

SA node (cardiac pacemaker) generates action

potentials that pace cardiac contractions

• Nervous system doesn’t initiate heart beats; only

adjusts heart rate and strength

Signal spreads through the atria, down fibers in

the septum, and up walls of the ventricles

Cardiac Conduction System

Key Concepts: THE HUMAN HEART

AND TWO FLOW CIRCUITS

The human heart has four chambers

Blood flows into its two atria and then into two

ventricles, which pump it into two separate

circuits of blood vessels

One circuit extends through all body regions, the

other through lung tissue only

Both circuits loop back to the heart

34.7 Blood Pressure and Distribution

Blood pressure varies in the circulatory system

• Highest in contracting ventricles

• Declines as blood travels through arteries,

arterioles, capillaries, venules, and veins of the

systemic or pulmonary circuit

• Lowest in relaxed atria

Human Blood Vessels

Fig. 34.17a, p.570

Fig. 34.17b, p.570

Fig. 34.17c, p.570

Fig. 34.17d, p.570

Blood Pressure

through the Systemic Circuit

Fig. 34.18, p.570

venules

120

capillaries B

loo

d p

ress

ure

(m

m H

g)

0

40

80

arterioles

veins arteries

(diastolic)

(systolic)

Blood Flow

Flow speed depends on heartbeat strength and

rate, and resistance to flow in blood vessels

Adjusting the diameter of arterioles in different

parts of the body redistributes blood volume

Tissues that require the most metabolic support

get the most blood flow

Adjustments in Blood Distribution

Controlling Blood Pressure

Blood pressure depends on blood volume,

cardiac output, and arteriole constriction

34.8 Capillary Function

Capillary beds are zones of diffusion between

blood and interstitial fluid

• Ultrafiltration pushes fluid out of capillaries

• Fluid moves back in by capillary reabsorption

Processes are balanced

• At most, a small net outward flow of fluid from a

capillary bed

Fluid Movement at a Capillary Bed

Fig. 34.21a, p.572

blood

from

arteriole

blood to

venule

inward-directed

osmotic movement

outward-directed

bulk flow

cells of

tissue

Fig. 34.21b, p.572

Veins and Venules

Veins

• Transport blood back to the heart

• Serve as a blood volume reservoir where the flow

volume is adjusted

Venules

• Deliver blood from capillaries to veins

• Several capillaries drain into each venule

Vein Structure and Function

Key Concepts: BLOOD VESSEL

STRUCTURE AND FUNCTION

The heart pumps blood rhythmically, on its own

Blood pressure is highest in the heart’s

ventricles, drops as it flows through arteries, and

is lowest in the atria

Key Concepts: BLOOD VESSEL

STRUCTURE AND FUNCTION (cont.)

Adjustments at arterioles regulate how much

blood volume is distributed to tissues

Exchange of gases, wastes, and nutrients

between blood and tissues takes place at

capillaries

34.9 Hemostasis

Hemostasis

• Process that stops blood flow from small vessels

after injury by bringing about clot formation

• Blood clotting is beneficial, except in certain

cardiovascular disorders

Hemostasis

Phase 3 response

Clot formation starts after thirty seconds:

1. Enzymes activate factor X; prothrombin forms.

2. Prothrombrin converts an enzyme precursor

to thrombin.

3. Thrombin converts fibrinogen, a plasma

protein, to insoluble protein threads (fibrin).

4. Fibrin forms a net that entangles blood cells

and platelets; the entire mass is a blood clot.

Stimulus

Blood vessel damage

Phase 2 response

Platelets aggregate and stick together within

fifteen seconds, thus plugging the site.

Phase 1 response

A vascular spasm constricts the vessel at the

site of damage, slowing blood loss.

Circulatory System Disorders

Atherosclerosis, hypertension (chronic high

blood pressure), heart attacks, strokes, certain

arrhythmias

Regular exercise, maintaining normal body

weight, and not smoking lower risk for these

disorders

Atherosclerosis

Coronary Arteries

ECG: Arrhythmias

Fig. 34.26, p.575

bradycardia

(here, 46

beats per

minute)

tachycardia

(here, 136

beats per

minute)

ventricular

fibrillation

0 0.2 0.4 0.6 0.8

one normal

heartbeat

a time (seconds)

Key Concepts:

WHEN THE SYSTEM BREAKS DOWN

Ruptured or clogged blood vessels or abnormal

heart rhythms cause problems

Some problems have a genetic basis; most are

related to age or life-styles

34.10 The Lymphatic System

Lymphatic vascular system

• Includes lymph capillaries and lymph vessels

Interacts with the circulatory system

• Takes up excess water from interstitial fluid and

fats absorbed from the gut; delivers them to blood

• Delivers bloodborne pathogens to lymph nodes

Lymphoid Organs

Lymph nodes filter lymph

• White blood cells in nodes attack any pathogens

Spleen filters blood

• Removes any old red blood cells

Thymus gland

• T lymphocytes (immune cells) mature in thymus

The Human Lymphatic System

Fig. 34.27a, p.576

Fig. 34.27b, p.576

Fig. 34.27c, p.576

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 other threats to health