Circulation

Chapter 42

The Need for a Circulatory System?

• One celled organisms (bacteria) do not have a circulatory system—they rely solely on diffusion

• Cnidarians (hydra, jelly fish) do not have a true circulatory system- the gastrovascular cavity branch throughout the organism relying on diffusion to distribute nutrients

• So why do other organisms need a circulatory system?

The Basics of a Circulatory System

• Circulatory fluid (ie: blood)

• Vessels

• A muscular pump (ie: a heart)

Invertebrate Circulation - Open

• Open Circulatory System –blood and interstitial fluid (together called hemolymph) bathe organs directly, blood is pumped to the spaces (sinuses) around the organs and returns to the heart through pores called ostia

• ex: mollusks and arthropods• Advantage: requires less energy to maintain (as

compared to closed)

Open Circulatory System- the grasshopper

Invertebrate Circulation - Closed

• Blood is moved through blood vessels and is separate from interstitial fluid

• ex: earthworm, squid, octopi

• Advantage: more effective, faster

Closed Circulatory System – the earthworm

All Vertebrate Circulation Has:

• Closed circulatory system

• AKA cardiovascular system

• Heart- has atria and ventricles

• Vessels: have arteries, veins and capillaries, along with arterioles and venules

Parts of the Circulatory System

• Atria – chamber of heart that receives the blood• Ventricles – chamber of heart that pumps blood

out of heart—more muscular• Artery – pumps blood away from heart, flows into

arterioles then to capillaries• Vein – capillary blood flows into venules which

turn into veins, then bringing blood to the heart• Capillary – very thin vessels that allow for quick

diffusion

Fish Circulation

• Heart: one ventricle and one atria

• Gill Circulation: blood pumped from heart to gills where gas exchange occurs

• Systemic Circulation: blood from gills gets carried to all the other parts of the body

Amphibian Circulation

• Heart: 2 atria and one ventricle

• Artery out of ventricle splits into two: pulmocutaneous circuit and the systemic circuit – double circulation

Reptile Circulation

• Heart:3 chambers (ventricle is separated by septum to prevent mixing of blood)

• Pulmonary and systemic (double circulation) circuits

Mammals and Birds

• Heart: 4 chambered (completely separates oxygen rich and poor blood), double circulation

Vertebrate Circulation

Simple Diagram of Blood Flow through Heart

• Superior and inferior vena cava

• Pulmonary artery• Pulmonary vein• Aorta

Blood Flow through a Mammalian Heart

The Heart• Cardiac Cycle – complete sequence of pumping and filling

• Systole – contraction phase of heart

• Diastole – relaxation phase of heart

• Semilunar Valves –stop backflow of blood out of heart “dub”

• Atrioventricular (AV)Valve – separate and stop backflow of blood between atria and ventricles “lub”

• Sinoatrial (SA) Node – in RA, pacemaker, coordinates contraction of atria

• Atrioventricular (AV) Node - receives message from SA node and contracts ventricles

The Cardiac Cycle

• Diastole – during relaxation phase blood flows into the atria

• Atrial Systole – contracts blood from atria into ventricle

• Ventricular Systole – contracts ventricular blood into arteries

The Control of Heart Rhythm

Blood Vessels

• Arteries and veins made up of connective tissue outside, smooth muscle in the middle and endothelium in the middle

• Arteries – pump blood away from heart, have more muscle, helps maintain blood pressure

• Veins – bring blood to the heart, valves, associated with the skeletal muscles

• Capillaries – consist of only endothelium, very thin to allow for diffusion between blood and ISF

Artery to Vein

Blood Pressure

• Blood Pressure – pressure blood puts on its vessels, highest in arteries

• Systolic – pressure in arteries when heart contracts• Diastolic – pressure when heart is relaxed• Stress, high sodium diet, etc. can raise blood pressure

Lymphatic System

• Capillaries lose fluid as they diffuse materials from blood to ISF

• The lymphatic system recycles this lost fluid through lymph vessels- carries fluid called lymph and returns it to circulatory system

• Lymph nodes are filled with WBC’s that attack viruses and bacteria

• Why would your lymph nodes (“glands”) be swollen when you are sick?

• What are the two major roles of the lymphatic system?

The Fluid of the Blood

• Plasma – mainly water, also contains proteins, ions, antibodies, fibrinogen, nutrients, wastes, hormones; serves to maintain osmotic balance and buffer the blood

RBC’s

• AKA erythrocytes• Small and biconcave to allow the most

surface area for oxygen transport• Contain hemoglobin (contains iron) that

binds to oxygen• Lack nuclei and mitochondria• Why is it important that RBC’s do not have

mitochondria?

WBC’s

• AKA Leukocytes• Involved in immune

system• Found in blood, lymph

and ISF• You can wait to learn

these cells until next chapter!!!

Platelets

• Involved in clotting by serving as a physical barrier (plug) to the wound, and by secreting chemical clotting factors (prothrombin, thrombin and fibrinogen) that make fibrin (a fibrous network)

Circulatory Diseases

• Hemophilia – genetic disease that results in improper clotting

• Murmor – defect in heart valves, usually harmless• Artherosclerosis – plaques narrow coronary arteries• High Cholesterol – HDL and LDL • Hypertension – high blood pressure• Heart Attack – blockage that stops blood flow to heart,

could result in death of the cardiac muscle• Stroke – blockage in artery of head, result in death of

nervous tissue

The Respiratory System• Gas exchange – uptake of oxygen and

release of carbon dioxide• Need a respiratory surface- the place where

gases are exchanged• Respiratory surface should be high in surface area and moist• COUNTERCURRENT EXCHANGE

Respiratory Adaptations

• Respiratory Surface/ Organism

• Cell Membrane/ Unicellular and Simple Animals

• Skin/earthworm (amphibians)

• Gills/aquatic organisms

• Tracheae/ insects

• Lungs and alveoli/ vertebrates

Gills as a Respiratory Surface

• Aquatic organisms have no problem with moisture, but water has a low oxygen content, therefore ventilation (increasing the flow) is necessary

• Countercurrent exchange-blood flows opposite to water flow

Countercurrent Exchange

Tracheal System as a Respiratory System

Made up of air tubes which branch to the surface of every cell

Lungs as a Respiratory Surface

Alveoli are interface between the respiratory system and the circulatory system – they are closely related to capillaries

Parts of Mammalian Respiratory SystemNose/Mouth

Larynx

Trachea

Bronchi

Bronchiole

Alveoli

Negative Pressure Breathing

• Pulls air into lungs (like a suction pump)

• Aided by the contraction of the diaphragm

Negative Pressure Breathing

Autonomic Control of BreathingPons and medulla regulate breathing

Sensors respond to pH changes – lowered pH signals increase breathing

Respiratory Pigments

• Carry oxygen to increase efficiency

• Hemocyanin- contains copper, found in arthropods

• Hemoglobin – contain iron, found in vertebrates