Chapter 42: Circulatory System p. 871

·        Diffusion too slow

·        Presence of circulatory system reduces the distance substances must diffuse (carried by the blood instead)

·        Critical component to maintaining homeostasis of body

·        Blood passes through organs (liver, kidney) which regulate the nutrients and waste content of blood.

·        Figure 42.2 p. 873

·        Figure42.4 p. 875

 

Gastrovascular cavities

·        Body plan does not require internal transport

·        Gastrovascular cavities are continuous with environment.

·        Example: Cnidarian (Hydra), carnivorous, aquatic

§         Contain Nematocysts, stinging organelles

 

Open Circulatory System

·        Insects, Crustaceans, Spiders, arthropods, mollusks

·        A system in which hemolymph bathes internal organs while moving through sinuses

·        Hemolymph is the fluid that acts like blood.

 

Closed Circulatory System

·        Annelids(earthworms), squids, vertebrates

·        System in which blood is confined to vessels

 

Cardiovascular system consists

·        Heart

·        blood vessels

·        Blood

 

HEART

·        Made of chambers, the atrium and ventricle

§         Atrium

·        Collecting chambers

·        Thin walls (allows the chamber to stretch)

§         Ventricle

·        Pumping chambers

·        Thick walls

·        See p. 874 Figure 42.3

·        Fish- 2 chambers---------- 1 atrium and 1 ventricle

·        Amphibians- 3 chambers ------------- 2 atria and 1 ventricle

·        Mammals- 4 chambers ----------- 2 atria and 2 ventricle

 

Human Heart

·        P. 876 Figure 42.5

·        Located beneath sternum

·        Comprised mostly of cardiac muscle tissure

·        Enclosed within the Pericardium

·        2 atria, collect blood returning to the heart

·        2 ventricles, pumping blood away from the heart

 

Cardiac cycle

·        A complete sequence of contractions and relaxation

·        Systole

§         Heart muscle contracts

§         Blood pumped away

·        Diastole

§         Heart muscles relax

§         Chambers fill with blood

 

4 valves of the heart

·        The “heart beat” heard is due to the opening and closing of the valves

·        The “lub” created by the recoil of blood against closed AV valves.

·        The “dub” recoil against SV valves

·        EKG

Atrioventricular valves (AV)

·        2 valves

·        found between each atrium and ventricle

·        prevents blood from back flowing during contractions

Semilunar valves

·        2 valves

§         location

·        aorta leaves left ventricle

·        pulmonary artery leaves the right ventricle

·        prevents blood from back flowing during relaxation

·        Heart rate- the number of heart beats per minute

§         Average 60 beats/min at rest

§         heart beat and water depth comparison...a transverse wave example

·        Heart Murmur- leaking valve

 

Blood Vessels

Arteries- lead away from the heart

·        Thicker walls to withstand pressure of blood being pumped away from the heart

·        The pulmonary artery is the only artery that carries deoxygenated blood

·        Arteries branch into smaller arterioles

Capillaries

·        Smaller vessels, increases surface area serviced by blood

·        Delivers oxygen, nutrients etc…picks up waste, CO₂, other cell products

Venules- Capillaries merge into larger vessels carry blood back to the heart

Veins- Carry blood back to the heart, thinner walls; blood pressure is lower in veins

 

Blood Pathway (Starting with the blood leaving the heart)

1. Aorta- largest artery, carries oxygenated blood; branches allowing blood to flow to the head and shoulder area, and to the lower part of the body.
2. arteries
3. arterioles
4. capillaries
5. venule
6. veins
7. Vena Cava
1. Superior Vena Cava- large vein bringing deoxygenated blood back from the head and shoulders to the heart
2. Inferior Vena Cava- large vein bringing deoxygenated blood from the lower part of the body to the heart
8. Right Atrium
9. AV valve
10. Right Ventricle
11. Semilunar valve
12. Pulmonary artery- blood is still deoxygenated
13. Lungs
14. Pulmonary Vein- only vein that carries oxygenated blood
15. Left atrium
16. AV valve
17. Left ventricle
18. Semilunar valve
19. Aorta