The Circulatory System

Importance of Circulatory System Carry nutrients to cells Carry waste away from cells Transport dissolved gasses Transport chemical messages (hormones) Regulate temperature Highway for cells of the immune system Around the world 2.5 times @ equator (40 000 km circumference)

3 Fundamental Features A fluid that transports material throughout the body BLOOD A network of hollow tubes in which the blood circulates BLOOD VESSELS A pump that pushes the blood through the tubes HEART

BLOOD AND BLOOD VESSELS

Blood 70 kg person has ~ 5L of blood Blood is a “fluid” tissue referred to as connective tissue due to its ability to link all cells and organs in the body.

The Components of Blood Plasma Red Blood Cells (Erythrocytes) White Blood Cells (Leukocytes) Platelets

Plasma Plasma = fluid medium which transports the following around the body and accounts for 55% of blood volume: Water: 92% of plasma Proteins Dissolved gasses: CO2 & O2 Nutrients: glucose, vitamins Wastes Hormones

Erythrocytes aka Red Blood Cells Function: Transport oxygen No nucleus (more room for hemoglobin) Contain hemoglobin: Iron-containing protein with a high-affinity for oxygen Carries oxygen from lungs  tissues Has nothing to do with whether or not they are bound to oxygen. More like how superficial they are to the skin. Blue light passes through skin and illuminates the veins so we see them as blue. Optical illusion. Thread veins are illuminated by red light. Arteries would also be blue if they were closer to the surface, but they are deeper in the body since they carry higher pressure and need more protection. 2 million – 3 million Erythrocytes are produced each second! (developed in the bone marrow)

Hemoglobin Protein which carries oxygen Found inside red blood cells

Leukocytes aka White Blood Cells Function: <1% of total blood cells but will double when body is fighting infection Have a nucleus Several types of WBC’s, all of which serve a specific role in the immune system Some WBC’s engulf invaders via phagocytosis  release enzymes that digest invader https://www.youtube.com/watch?v=Z_mXDvZQ6dU

5 Types of WBC’s Granulocytes: Neutrophil: Most abundant in body engulf and digest bacteria Eosinophil: Found in lining of digestive and respiratory tracts. Attack and kill parasites and kill cancer cells Basophil: Recognize pathogens and alert the immune system by secreting chemicals

5 Types of WBC’s Agranulocytes Lymphocytes: produce proteins called antibodies that incapacitate pathogens Monocytes: help to destroy bacteria

Thrombocytes aka Platelets Small cell fragment No nucleus Fragile Rupture when they hit a sharp edge (i.e. torn blood vessel)  initiates blood clotting reaction (coagulation)

Blood Vessels

(gas exchange with body cells) Summary of vessels Capillaries (gas exchange with body cells) Arterioles Venules Arteries (high pressure) Veins (low pressure) Heart Lungs Arteries/arterioles carry blood away from heart Veins/venules carry blood to the heart oxygenated deoxygenated

Arteries Carry blood away from the heart Have thick walls - needed to withstand the high blood pressure Walls contain smooth muscle and an elastic connective tissue Pulse = change in diameter of arteries following heart contraction Arteries branch into arterioles

Arterioles Smaller arteries Walls contain muscles which can regulate the diameter of the arterioles Vasoconstriction: diameter reduced, blood flow reduced Vasodilation: diameter increased, blood flow increased Arterioles branch into capillaries

Capillaries One cell thick (ideal for diffusion) Site of gas/fluid exchange Deliver O2/nutrients to body cells Picks up CO2/wastes Easily ruptured  bruising Merge into venules

ALL Tissues are Surrounded by Capillaries

Venules Drain blood directly from capillaries Thinner walls than arterioles Lower pressure Merge into veins

Veins Thinner walls than arteries, less muscle and connective tissue Do not contract to help move blood back to the heart Lower pressure Arteries Veins

Venules/Veins – Returning Blood to Heart Solution 1. One-Way Valves ONLY veins have them! Prevent low pressure blood from flowing backwards 2. Contracting muscles Example: the muscles of the leg help force blood through the valves in a step-wise fashion stretching

Arteries Veins Arteries Veins Transport blood AWAY from the heart Thick Muscular Do not have one-way valves Transport blood TOWARDS the heart Thin Less muscle Have one-way valves

Evolution of the Circulatory System Unicellular and simple multicellular organisms do not need circulatory systems (use diffusion & osmosis) Circulatory systems are an evolutionary adaptation to increase in size and complexity The heart evolved from a simple 2-chambered structure to a 4-chambered structure

The Mammalian Circulatory System:

Heart Circuits The pathway of vessels carrying blood to and from the lungs compromises the pulmonary circulatory system The pathway of vessels carrying blood to and from the body compromises the systemic circulatory system

Systemic Systemic Pulmonary Capillary Beds of Head and Arms Capillary Beds of Lungs Pulmonary Systemic Capillary Beds of Trunk and Legs

Homework Read pages 482-488 Answer: Pg 486 # 7-12