Respiration and Circulation Part 2

Biology 155

Krilowicz

Spring 2010

II. Circulation:

A. Components-

1. The cardiovascular system = heart + blood vessels

Function = Circulates the blood to and from the tissues

Fig. 23.3A

2. The lymphatic system = lymph vessels + lymph nodes

Functions –

-immune defense

- returns some fluid from the tissues

Fig. 24.3

Return of excess fluid from the tissues via the immune system

B. Functions of the Circulatory System

1. Transport – oxygen, carbon dioxide, nutrients, wastes and hormones in blood

2. Blood clotting – to seal breaks in vessels, uses platelets and clotting proteins

3. Protection – internal defense using the white blood cells and the lymphatic system

C. Types of Circulatory Systems

1. None –a. Only used by small animals and/or those with

low rates of oxygen use

b. Circulation occurs due to simple diffusion through the body tissues

Examples of Animals That Lack a Circulatory System

• sponges (not shown)• jellyfish • flatworms • sea stars

2.

3.

(Pump)Few vessels

(Tissue sinuses)

Few vessels

Blood leaves vessels, loses pressure, thus low flow, low oxygen demand system

large vessels (arteries, arterioles)

Capillaries in tissues for exchange

(pump)

large vessels (veins)

Blood stays in vessels, thus high pressure, high flow system for high oxygen demand

Fig. 23.1

Examples of Animals with an Open Circulatory System

• clams • Crayfish, shrimp,

lobsters (not shown) • insects as exception to

low oxygen use rule (remember the tracheal system)

Examples of Animals with a Closed Circulatory System

• vertebrates from fish to mammals

D. The Vertebrate Circulatory System -

1. Blood consists of–a. Plasma = fluid with dissolved substances

(examples – nutrients, hormones and most carbon dioxide)

b. Cells and cell fragments –1) White blood cells – defense

2) Red blood cells – oxygen transport

3) Platelets – blood clotting

2. Vertebrate hearts and circulatory patterns -

Note that the evolution of the four-chambered heart of the mammals and birds allows blood to be returned to the heart after exchanging gases at the lungs and to be pumped a second time before traveling to the tissues, needed for high oxygen demand associated with high body temperatures

Mammals and

aorta

Vena cava

Atrium = receiving chamber

Ventricle = pump

Two-chambered heart with blood pumped once; lower pressure, lower flow system

And thus blood is pumped twice for a higher pressure, higher flow system

arteries

(Pressure declines)

CO2

O2

O2CO2

Pulmonary artery

Pulmonary vein

aorta

Vena cava

Left atriumRight ventricle

Right atrium

CO2

O2

CO2

O2

Fig. 23.2

3. Generation of the heart beat – note that all cardiac cells are autorhythmic and contract on their own

Pacemaker (fastest rate of contraction) =

Electrical signals = action potentials pass due to intercalated discs

(Holds signal before passing to ventricles, connective tissue between atria and ventricles prevents immediate passage of signal

Fig. 23.5A