Download A. Introduction

CIRCULATORY SYSTEM
I.
INTRODUCTION
A. Functions
1. To bring nutrients to the body cells and remove wastes
a) Blood is a connective tissue that serves to connect body cells to organs that
interact with the external environment
(1) Blood connects body cells to the lungs
(a) Removes CO2 and replenishes O2
(2) Blood connects body cells to the small intestines
(a) Acquires nutrients
(3) Blood connects body cells to the kidneys
(a) Removes nitrogenous wastes
B. Types
1. Simple diffusion
a) Some organisms, because of their size, require no specialized circulatory
system
(1) Oxygen can diffuse in from the environment and wastes can diffuse out
(2) As body size increases, simple diffusion cannot meet these demands
(3) Organisms that use simple diffusion include bacteria, protists, fungi,
sponges, radiates, and platyhelminths
2. Open and closed circulatory systems
a) In a closed circulatory system, circulatory cells remain in blood vessels at all
times
(1) The circulatory fluid is called blood
(2) Organisms with a closed circulatory system include the Nemertea,
mollusks, annelids, and vertebrates
b) In an open circulatory system, circulatory cells come in direct contact with
body tissues
(1) The circulatory fluid is called hemolymph
(2) Arthropods have this type of system
c) Echinoderms have a water-vascular circulatory system
II. HEART STRUCTURE
A. A cone-shaped muscular organ, about the size of a fist, located behind the
sternum
1. The coronary arteries nourish the heart
B. Contains three layers of tissues
1. Epicardium
a) Protective outer layer of connective tissue
2. Myocardium
a) Middle portion that consists largely of cardiac muscle tissue that is branched
3. Endocardium
a) Protective in layer of connective tissue lining the chambers
C. Consists of 4 chambers
1. Two thin-walled atria
a) The atria are receiving chambers
(1) The right atrium receives deoxygenated blood from the vena cava
(2) The left atrium receives oxygenated blood from the pulmonary veins
2. Two thick-walled lower chambers
a) The ventricles are pumping chambers
(1) The right ventricle pumps deoxygenated blood to the lungs via the
pulmonary trunk and arteries
(2) The left ventricle pumps oxygenated blood to organs and tissues via the
aorta
b) Walls of left ventricle are thicker since it must pump blood to the entire body
3. Valves
a) Atrial and ventricle chambers are separated by atrioventricular valves
(1) Tricuspid on right side and bicuspid on left side of heart
(2) Valves are supported by chordae tendineae
b) Semilunar valves are found between the ventricles and their attached
arteries
D. Overview of blood flow through the body
1. Note that the heart is a double pump with 2 separate circular paths
a) Pulmonary circuit
(1) Right side of heart  lungs  left side of heart
b) Systemic circuit
(1) Left side of heart  body  right side of heart
III. CARDIAC CYCLE (A HEART BEAT)
A. Definitions
1. Systole
a) Refers to chamber contraction and pumping
2. Diastole
a) Refers to chamber relaxation and filling
B. About 0.8 Seconds per cycle
1. 0.0 - 0.1 sec
a) Atrial systole
(1) Both atria contract
2. 0.1 - 0.4 sec
a) Ventricular systole
(1) Both ventricles contract
b) Beginning of atrial diastole
(1) Atria relax
(2) Atrioventricular valves close
3. 0.4 - 0.8 sec
a) Atrial and ventricular diastole
(1) The atria remain relaxed and the ventricles relax
(2) Semilunar valves close
C. Heart Sounds
1. lub-DUPP; lub-DUPP; lup-DUPP
a) Lub sound
(1) Due to closing of the atrioventricular valves
b) DUPP sound
(1) Due to the closing of the semilunar valves
2. Heart murmurs are often due to ineffective atrioventricular valves that allow
blood to pass back into the atria
IV. MYOGENIC TISSUE
A. Definition
1. Tissue with properties of muscle tissue and nervous tissue
a) Capable of contraction and electrical impulse propagation
B. Two major nodal tissues
1. Sinoatrial node
a) Located in the upper dorsal wall of the right atrium
(1) Common name is the pacemaker
b) It initiates the heartbeat by depolarizing approximately every 0.8 second
(1) Will contract without nervous system input, but nervous system can
effect periodicity of depolarization
(2) Causes the atria to contract
(3) If defective, may be replaced with an artificial pacemaker
2. Atrioventricular node
a) Found at the base of the right atrium near the septum
b) It stimulates the ventricles to contract after impulses have reached it from the
sinoatrial node
C. Electrocardiogram (ECG or EKG)
1. The electrical recordings of the heart contraction through body fluids
V. BLOOD PRESSURE
A. Introduction
1. The pressure of the blood against the wall of a blood vessel
a) The blood pressure in the brachial artery is commonly measured
B. Systolic blood pressure
1. Arterial pressure when ventricles are contracting
a) In the brachial artery is ~120 mm of mercury (Hg)
C.
Diastolic pressure
1. Arterial pressure when ventricles are relaxing
a) In the brachial artery is ~80 mm Hg
D. Can be determined with a sphygmomanometer and stethoscope
1. Procedure
a) Increase cuff pressure of sphygmomanometer until blood is cut off to the
lower arm
(1) The stethoscope will detect no sound, since blood will not be flowing
past the cuff
b) Slowly release pressure
(1) Record the pressure at first sound of blood going past the cuff
(a) The pressure of the cuff will about equal the pressure in the artery as
the heart is contracted
(b) This will by the systolic pressure
(2) Record the pressure at which no sound can be heard
(a) The cuff is no longer able to constrict the artery when the heart is
relaxed
(b) This is the diastolic pressure
VI. VASCULAR PATHWAYS
A. Pulmonary Circuit
1. Blood in the right ventricle is deoxygenated and high in CO 2
a) Right ventricle  pulmonary arteries and arterioles  pulmonary capillaries
(1) Oxygen diffuses into the blood from the lungs and CO 2 out of the blood
into the lungs
b)  pulmonary venules and veins  left atrium
B. Systemic Circuit
1. Blood in the left ventricle of the heart is oxygenated with low CO 2 content
a) Left ventricle  aorta  arteries  arterioles  capillaries
(1) Oxygen diffuses from blood into tissues and CO2 diffuses from tissues
into blood
b)  venules  veins  vena cava  right atrium
VII. BLOOD VESSELS
A. Arteries and Arterioles
1. Function
a) To transfer blood away from the heart
(1) Arteries are able to expand after each
heartbeat to accommodate increased blood
volume
B. Capillaries
1. Structure
a) Arterioles branch into capillaries, which are very
narrow and are composed of one layer of
endothelial cells
2. Function
a) Site of exchange of nutrients and waste between
the blood and body cells.
C. Veins and Venules
1. Structure
a) Has the same structure as an artery but wall is much thinner
b) Venules drain the blood from the capillaries, and then join to form a vein
2. Function
a) To return blood from the capillary beds to the heart
VIII.BLOOD
A. Introduction
1. Approximately five liters of blood
a) Can be divided into liquid portion and cellular portion
(1) The liquid portion is called plasma and makes up about 55% of the blood
be volume
(2) The cellular portion is called the hematocrit and makes up the remaining
45%
2. Functions
a) Transports molecules to / from the capillaries
b) Guards the body against microbial invasion
c) Prevents blood loss by clotting
B. Plasma
1. Components
a) Salts
(1) Maintains osmotic balance
(2) pH buffering
b) Proteins
(1) Albumin
(a) Osmotic balancing
(b) pH buffering
(2) Fibrinogen
(a) Blood clotting
(3) Immunoglobulins
(a) Antibodies aid in immunity
c) Other dissolved substances
(1) Glucose
(a) Energy source for cells
(2) Carbon dioxide
(a) Waste product of cells
(3) Hormones
(a) Chemical coordination of body systems
(4) Urea
(a) Waste product of cells
C. Cells
1. Erythrocytes
a) Common name is red blood cells
(1) 4.6 - 6.2 million erythrocytes / l
b) Structure
(1) Biconcave shape
(a) Increased surface area for gas diffusion in capillaries
(2) Packed with hemoglobin
(a) An oxygen carrying protein
(3) Anucleated
(a) Nucleus is extruded during development to make room for more
hemoglobin
c) Function
(1) Deliver oxygen from lungs to tissues
d) Life span is about 120 days
(1) Destroyed by macrophage in the liver and spleen
(2) Iron from broken down hemoglobin may be recovered and reused, or
excreted by liver to ultimately become bile pigments
2. Leukocytes
a) Commonly called white blood cells
(1) ~ 5,000 - 10,000 leukocytes / l
(a) Leuokopenia
(i) Less than 5,000 WBC / l
(ii) Indicates patient is immunocompromised
(b) Leukocytosis
(i) Greater than 10,000 WBC / l
(ii) Indicates patient has an infection
b) Structure
(1) Leukocytes are the only mature blood cells with nuclei
(a) The shape and size of the nucleus aids in the identification of cell
type
c) Function
(1) Identify and destroy foreign objects (antigens)
3. Thrombocytes
a) Commonly called platelets
b) Produced by fragmentation of megakaryocytes
c) Involved in blood clotting and inflammation