Functions of the Circulatory System:– transport– defense– regulation

Lecture 6. Transport/Circulation

Animals without Circulatory System

protozoanssponges

flatworms cnidarians

• a single-celled protist living in water has a sufficient surface area of plasma membrane to service its entire volume

• the gastrovascular cavity of hydra opens to the exterior, both outer and inner layers of cells are bathed in water

• in cnidarians like Aurelia, the products of digestion in the gastrovascular cavity are directly available to the cells of the inner layer

• only a short distance to diffuse to the cells of the outer layer

• flat body = way to maximize exposure to the surrounding medium

–most organisms have extensively folded orbranched internal surfaces specialized for exchange withthe environment

–the circulatory system shuttles material among all the exchange surfaces within the animal

Internal Fluid Environment

protozoans

• cellular cytoplasm in unicellular animals

Internal Fluid Environment

• multicellular animals

• Two types of circulatory systems• Closed – heart pumps blood in a network of blood vessels and capillaries

• Open – heart pumps haemolymph into tissue spaces

Two Types of Circulatory System

Two Types of Circulatory System

insects, other arthropods, most mollusks

earthworms, squids, octopuses, vertebrates

Plan and Parts of Vertebrate Circulatory System

• often called the cardiovascular system

• the heart consists of one atrium or two atria, and one or two ventricles

• arteries, arterioles, veins, venules, and capillaries

• blood

• The Vertebrate Circulatory System• Closed type• Heart :

• Atrium – receive blood from circulation• Ventricle – pumps blood to blood vessels

Plan and Parts of Vertebrate Circulatory System

• Blood vessels :• Artery – brings blood AWAY from the heart• Arteriole – leads to capillaries• Capillary – where gas exchange takes place• Venule – leads to vein• Vein – brings blood TO the heart

• The Vertebrate Circulatory System

Plan and Parts of Vertebrate Circulatory System

–two-chambered heart

–subsidiary chambers: sinus venosus (SV), conus arteriosus (CA)

–blood circuit: single circuit

SV

CAArtery

–three-chambered heart

–blood circuit: double circuit

ArteryVein

Fig. 31.11Heart of an Amphibian with Lungs

• Reptiles also have double circulation with pulmonary (lung) and systemic circuits

• reptilian heart is three-chambered (except for crocodiles)

• ventricle is partially divided

– four-chambered heart

–crocodilians, birds, and mammals

–blood circuit: double circuit

ArteryVein

Human Heart

(Bicuspid or mitral valve)

(Tricuspid valve)

Coronary System

The Cardiac Cycle

Systole - contraction Diastole - relaxation

• cardiac output (5.25 L/min) depends on two factors:

– the rate of contraction or heart rate (number of beats per second)

– stroke volume (75 mL), the amount of blood pumped by the left ventricle in each contraction

• the heart sounds we can hear with a stethoscope are caused by the closing of the valves

– sound pattern is “lub-dup, lub-dup, lub-dup”

– “lub” is created by the recoil of blood against the closed AV valves

– “dup” is the recoil of blood against the semilunar valves

• the impulses generated during the heart cycle produce electrical currents that are conducted through body fluids to the skin

• the currents can be detected by electrodes and recorded as an electrocardiogram (ECG or EKG).

The control of heart rhythm

Fig. 31.14

– two sets of nerves (sympathetic and parasympathetic) affect heart rate with one set speeding up the pacemaker and the other set slowing it down

– the pacemaker is also influenced by hormones

– rate of impulse generation by the pacemaker increases in response to increases in body temperature and with exercise

The structure of blood vessels

32Blood flow in veins

The interrelationship of cross-sectional area of blood vessels, blood flow velocity, and blood pressure.

Measurement of blood pressure

•Makes use of a sphygmomanometer and the brachial artery•Systolic pressure - peak pressure in the arteries, which occurs near the end of the cardiac cycle when the ventricles are contracting

•Dyastolic pressure - minimum pressure in the arteries, which occurs near the beginning of the cardiac cycle when the ventricles are filled with blood

Changes in blood pressure

•Varies within the day due to circadian rhythm

•Also change due to stress, nutrition, exercise, drugs, disease, and simply standing up

•Hypertension – when arterial pressure is abnormally high•Hypotension – when arterial pressure is abnormally low

Blood flow in capillary beds

Fluid exchange between capillaries and the interstitial fluid

The Blood

•Hemophilia – inability to clot blood – a sex-linked trait

•Hemophilia A – clotting factor VIII deficiency•Hemophilia B – clotting factor IX deficiency