SBI3U - Unit 4 - Circulatory System

The Function of Circulation

• Circulatory System - The system that transports blood, nutrients, and waste around the body

• Purposes of the circulatory system:

  • To transport gases from the respiratory system, nutrient molecules, and waste molecules from the digestive system

  • It regulates internal temperature and transports chemical substances that are vital to health from one part of the body to the other

  • It protects against blood loss from injury and against disease-causing microbes or toxic substances introduced into the body

• Major components of the circulatory system:

  • Heart - A muscular organ that continuously pumps the blood via the circulatory system to the lungs and body and generates blood flow

  • Blood Vessel - A hollow tube that carries blood to and from body tissues

    • The heart and vessels are part of the cardiovascular system

    • Artery - A blood vessel that carries blood away from the heart

      • Has highly elastic walls that allows the artery to expand as a wave of blood surges through it during the contraction of ventricles, and then to snap back during the relaxation of ventricles

        • This keeps the blood flowing in the right direction and provides an additional pumping motion to help propel blood

      • Arteriole - A smaller-diameter artery

    • Vein - A vessel that carries blood toward the heart

      • Has thin walls and a larger inner circumference, not as elastic, and cannot contract to help move the blood

      • The contraction of muscles keeps the blood in the veins flowing toward the heart

      • Veins have one-way valves that prevent the blood from flowing backward

      • Venule - A smaller-diameter vein

    • Capillary - A one-cell thick vessel where gases, nutrients, and other materials are transferred between blood and tissue cells

      • Capillaries are spread in a fine network, and are 8μm thick, which allows blood cells to pass in a single-file line

  • Blood - The bodily fluid in which blood cells are suspended, which transports nutrients and gases throughout the body

• Two types of circulatory systems

  • Open Circulatory System - A circulatory system in which vessels open into the animal’s body cavity

    • The blood makes direct contact with the organs and tissues

    • There is no distinction between the blood and the interstitial fluid, and forms a mixture called called hemolymph

    • Arthropods and mollusks (except cephalopods) have open systems where the blood is pumped by a tubular, sac-like heart

    • Ex. Grasshoppers have a single vessel that runs from the head to the abdomen. The vessels divides into chambers in the abdomen, which serves as the insect’s heart. Tiny holes in the heart wall called ostia allow hemolymph to enter the heart chambers and are pushes into the chambers by muscle contractions. Nutrients and wastes are exchanged, and then the hemolymph passes into the transporting vessel to be eliminated from the body.

  • Closed Circulatory System - A circulatory system in which the circulating blood is contained within vessels and kept separate from the intestinal cavity

    • The blood is kept under pressure, follows a fixed path of circulation, and is confined to a network of vessels that keeps the blood separate from the intestinal fluid

    • Used by vertebrates, cephalopods, and annelids

    • Invertebrates have closed systems that have a dorsal and ventral blood vessel

    • Fish have closed, single circuit systems, where the blood is returned to the heart after every circulation of the body

    • Birds, reptiles, amphibians, and mammals have closed, double circuit systems with a pulmonary and systemic circulation

• The mammalian circulatory system

  • Mammals have a complex body system with a high demand for energy, so their circulatory systems must also carry waste products away from the cells quickly

    • Oxygen-rich and oxygen-poor blood must flow separately in the double circulatory system

  • Pulmonary Circulation - The path that blood follows from the heart to the lungs and back to the heart

    • The blood that flows from the heart to the lungs carries waste carbon dioxide gas

    • As this blood passes through the respiratory surfaces of the lungs, gas exchange takes place

    • Carbon dioxide leaves the blood and oxygen moves into the blood

    • The oxygen-righ blood goes back to the heart and is pumped from the heart into a second circuit that transfers it throughout the body

  • Systemic Circulation - The path that blood follows from the heart to the body and back to the heart

    • Oxygenated blood from the heart goes to other tissues and organs throughout the body

    • After circulating throughout the body, the blood returns to the heart carrying waste carbon dioxide from the body’s tissues

    • The blood then enters the pulmonary circulation

  • Cardiac Circulation - The movement of blood through the heart tissues

    • Blood is usually in the systemic or pulmonary circulation, but the heart muscle itself also needs blood

Transport and Exchange Systems

• Diffusion - The exchange of materials across a moist body surface without requiring specialized transport or exchange systems

• Mass Transport - The system for exchange and transport that facilitates movement of materials at equal rates or as a single mass, which accounts for the long distance transport of fluids in living organisms, such as the circulatory systems

Checklist

Text

• Pg 478-479

• Pg 482-483

Biozone 2

• 104

• 108

• 109

Other

• Fishtail video