LECTURE SIXTEEN CARDIOVASCULAR SYSTEM
HUMAN ANATOMY LECTURE SIXTEEN CARDIOVASCULAR SYSTEM CARDIOVASCULAR
SYSTEM
Includes: heart blood vessels fluid connective tissue component
BLOOD FUNCTION - maintain homeostasis by:
Transportation of gases, nutrients, and waste products Transport of
regulatory molecules (hormones) Regulation of pH and ion
concentration of interstitial fluids Maintenance of body
temperature Protection against foreign substances (toxins and
pathogens) Clot formation CHARACTERISTICS Fluid connective tissue
consisting of cells (formed elements) and cell fragments (formed
elements) surrounded by a liquid matrix (plasma) Temperature ~38 C
pH PLASMA Albumin Globulins Fibrinogen
91% water, 7% proteins (albumin, globulins, fibrinogen), 2% other
High capacity for holding heat - distributes heat generated from
metabolic activity of tissues Albumin Most abundant (60%) of plasma
proteins Important in transport of materials in the blood - A.A.
and some hormones Globulins Function as antibodies and for
transport of some ions and hormones Fibrinogen Responsible for
formation of blood clots FORMED ELEMENTS Erythrocytes (RBC),
leukocytes (WBC), thrombocytes (platelets) Produced by a process
called HEMATOPOIESIS - in adults occurs in red bone marrow Derive
from STEM CELLS that differentiate into specific cell types
ERYTHROCYTES - RED BLOOD CELLS
Biconcave disc with thin central region and thicker edges -
increases surface area for movement of gases in and out of cell -
ability to form stacks within tiny blood vessels - flexibility to
bend or stretch Lack organelles (to make room for more gases) - not
able to divide so are replaced every ~120 days HEMOGLOBIN is the
main component - composed of 4 globins (large protein molecules)
and a heme (pigment molecule that holds iron) - heme with oxygen =
oxyhemoglobin (bright red) - heme without oxygen = deoxyhemoglobin
(dark red) - heme with carbon dioxide = carbaminohemoglobin BLOOD
TYPING Antigens (proteins) appear on the surface of RBCs
TYPE A blood has A ANTIGENS TYPE B blood has B ANTIGENS TYPE AB
blood has AB ANTIGENS TYPE O blood has NO ANTIGENS Antibodies in
the plasma attack antigens TYPE A blood has B ANTIBODIES TYPE B
blood has A ANTIBODIES TYPE AB blood has NO ANTIBODIES TYPE O blood
has A and B ANTIBODIES Donors give blood and recipients receive
blood LEUKOCYTES - WHITE BLOOD CELLS
Spherical cells that lack white hemoglobin (clear/white) Much
larger than RBCs, have nucleus and other organelles Primary
functions are: - to protect the body against invading
microorganisms - to remove dead cells and debris from the tissues
by phagocytosis Move out of the blood and through the tissues by
ameboid movement - cytoplasmic streaming into projections of the
cellular membrane Migrate through body tissues to areas of
infection or injury - able to chemically detect signs of tissue
damage Many are capable of phagocytosis (engulfing) of pathogens,
cell debris, etc. TYPES OF LEUKOCYTES GRANULOCYTES (1) Neutrophils
most common
Named for appearance when stained - large cytoplasmic granules =
GRANULOCYTES - very small granules = AGRANULOCYTES GRANULOCYTES (1)
Neutrophils most common Have a very dense segmented nucleus with 2
5 lobes attached by a string-like structure - polymorphonuclear
leukocytes Highly mobile, first to the site of an injury
Phagocytize foreign substances, attack bacteria marked by
antibodies (2) Basophils least common Have many granules that stain
very dark Migrate to injury site and discharge granules into
interstitial fluid - histamine dilates blood vessels and heparin to
prevent blood clotting (3) Eosinophils Granules stain red Attack
objects coated with antibodies and release chemicals that reduce
inflammation AGRANULOCYTES (1) Lymphocytes smallest WBC
Large, round nucleus surrounded by a thin layer of cytoplasm
Continuously migrate through bloodstream, through tissues, and back
into the bloodstream Production of antibodies and other chemicals
that destroy microorganisms, produce allergic reactions, control
tumors, and regulate immune system (2) Monocytes largest WBC Large
spherical cells Leave bloodstream and become macrophages -
phagocytize bacteria, dead cells, and other cellular debris within
tissues Release chemicals that attract other WBCs THROMBOCYTES -
PLATELETS
Fragments of cells - bits of cytoplasm surrounded by cell membrane
Produced in bone marrow by megakaryocytes (very large cells)
Prevent blood loss by: (1) formation of platelet plugs to seal
holes in small vessels (2) formation of clots to seal larger wounds
in vessels - platelet plug forms to close site temporarily -
chemicals released causing vasoconstriction, bring more platelets
to the injury site, promoting vessel repair - plasma proteins form
permanent clot HEART Located in the thoracic cavity between the
lungs, within the mediastium The apex (pointed tip) is the most
inferior region - directed anteriorly and to the left, deep to the
5th intercostal space (between the ribs) The base (flat top) is
directed superiorly and slightly posteriorly -deep to the 2nd
intercostal space Functions: - generating blood pressure - routing
blood through the systemic (body) and pulmonary (lungs) circuits -
ensuring one-way blood flow EXTERNAL ANATOMY Pericardium
-double-layered closed sac anchoring the heart and vessels within
the mediastium Consists of: - fibrous pericardium = outer layer
with dense network of collagen fibers - serous pericardium = thin
layer of connective tissue Serous pericardium is divided into: -
visceral pericardium or epicardium covering the outer surface of
the heart - parietal pericardium lining the fibrous pericaridium
Pericardial cavity (space) between the visceral and parietal
pericardium - full of pericardial fluid produced by serous
pericardium reduces friction as the heart moves within the
pericardium PERICARDIUM Auricles extend from each atria -
expandable extension of atria
Coronary sulcus - deep groove separating atria and ventricles -
anterior and posterior interventricular sulci mark the separation
between the left and right ventricles (fat builds up in these
depressions) HEART WALL Three layers of tissue: Epicardium
(visceral pericardium)
thin, serous membrane forming the outer layer simple squamous
epithelium over a layer of loose connective tissue and fat
Myocardium Middle layer of cardiac muscle, blood vessels, nerves
Concentric layers of cardiac muscle tissue The atrial myocardium
contains muscle bundles that wrap around the atria and from figure
eights encircling the large vessels Superficial muscles wrap around
the ventricles with deeper layers spiraling around and between the
ventricles Endocardium Smooth inner surface of heart chambers
Simple squamous epithelium continuous with lining of the large
vessels Form the heart valves by folding with connective tissue
between the layers MUSCLE LAYERS INTERNAL ANATOMY Divided into four
chambers: right and left atrium - right and left ventricles
Interatrial septum separates the atria and thicker interventricular
septum separates the ventricles ATRIA Smaller, thinner walled upper
chambers - receive blood right atrium - superior and inferior vena
cava bring blood from upper and lower body - small coronary sinus
enters from the wall of the heart left atrium - pulmonary veins (4)
bring blood from the lungs VENTRICLES Major pumping chambers - push
blood to heart and body right ventricle - pulmonary trunk to
pulmonary arteries to lungs left ventricle aorta carries blood to
body Left ventricle wall is thicker than the right pumps blood
further Walls have muscular ridges called trabeculae carneae
INTERNAL STRUCTURE HEART VALVES One-way valves prevent the backflow
of blood as chambers contract Fibrous connective tissue rings
(skeleton of the heart) around the valves provide solid support for
the valves ATRIOVENTRICULAR VALVES Located between the atrium and
ventricles right AV valve - tricuspid valve with 3 cusps (folds)
left AV valve bicuspid (mitral) valve with 2 cusps After blood
flows from atria to ventricles the valves are pushed backward
toward atria forcing the opening shut Papillary muscles attach to
valves by thin, strong connective tissue strings called chordae
tendinae - muscles contraction prevents valves from opening
SEMILUNAR VALVES Found in aorta and pulmonary trunk Consists of
three pocketlike semilunar cusps When ventricles contract blood
pushes valves open - during relaxation blood flows back toward the
ventricle, entering pockets of cusps causing them to bulge inward
and meet in the center, thus blocking the vessel VALVES BLOOD
SUPPLY TO THE HEART
Myocardium is thick and very active metabolically Coronary arteries
supply blood to the heart wall Two c. arteries originate from base
of the aorta, just above the semilunar valve - the left c. artery
supplies the left side and the right c.artery supplies the right
side - both lie within the coronary sulcus Cardiac veins drain
blood from the myocardium The great cardiac vein runs along the
interventricular sulcus - running parallel to the c.arteries and
carries blood to the coronary sinus (a large vein within the
coronary sulcus on posterior side of heart) The coronary sinus
drains into the right atrium HEARTBEAT Contraction of the atria and
ventricles is coordinated by specialized cardiac muscle cells
(nodes) in the heart wall that form the conduction system of the
heart SINOARTERIAL NODE The impulse originates in the SA node which
contain pacemaker cells that establish heartbeat Embedded in the
posterior wall of the right atrium near the entrance of the
superior vena cava Send electrical impulses across the atria
causing them to contract Connected to the AV node by internodal
pathways in the atrial walls ATRIAVENTRICULAR NODE Found within the
floor of the right atrium near the opening of the coronary sinus
Impulse is conducted into a bundle of fibers - the atrioventricular
bundle or bundle of His down the septum and divide into left and
right bundle branches At the tips of the bundle branches the
conducting tissue forms many small bundles of Purkinje fibers -
extend to the apex of the heart and to the cardiac muscle of the
ventricle walls - conduct action potentials very quickly SA node
atria contract AV node bundle of His Purkinje fibers
ventricles contract while atria relax entire heart relaxes
ELECTROCARDIOGRAM Electrodes are placed on the surface of the body
to measure electrical current of the heartbeat P wave - contraction
of the atria QRS complex - contraction of the ventricles T wave -
relaxation of atria BLOOD VESSELS Walls of blood vessels (arteries
and veins) are made up of three layers: (1) Tunica intima - inner
endothelial lining with connective tissue layer - arteries have
thick layer of elastic fibers (2) Tunica media - concentric rings
of smooth muscle bound to other layers by collagen fibers - in
arteries separated from tunica externa by a layer of elastic fibers
- larger arteries have very thick layer (3) Tunica externa -
outermost layer, a connective tissue sheath for anchoring - in
arteries collagen fibers with elastin ARTERIES ELASTIC ARTERIES
MUSCULAR or DISTRIBUTING ARTERIES ARTERIOLES
Carry blood away from the heart Have thick, muscular, elastic walls
that allow changes in diameter in response to changes in blood
pressure - allow artery to expand and contract ELASTIC ARTERIES
Largest in diameter with thickest walls Greater portion of elastic
tissue as compared to smooth muscle compared to smaller arteries
MUSCULAR or DISTRIBUTING ARTERIES Medium-sized arteries distribute
blood to skeletal muscles and organs Walls are thick as compared to
their diameter - thick tunica media layer Blood flow is controlled
by vasoconstriction and vasodilation ARTERIOLES Tunica media is
only one or two layers of smooth muscle in larger arterioles, small
arterioles only have smooth muscle scattered throughout Innervated
by sympathetic nerve fibers - vasoconstriction CAPILLARIES Very
thin walls allow exchange between blood and surrounding fluids
Diameter so narrow that red blood cells flow through in single file
Origin of each branch has precapillary sphincters of smooth muscle
that regulate blood flow At arteriole end oxygen and nutrients
leave and at venous end carbon dioxide and waste products enter
VEINS Collect blood from tissues and organs and returns it to the
heart Walls are thinner than arteries because blood pressure is
much lower VENULES Take blood from capillaries Lack tunica media
layer MEDIUM-SIZED VEINS Tunica media layer is thin with little
smooth muscle Thickest layer is tunica externa Tunica intima folds
inward forming one-way valves to prevent backflow of blood - more
in veins of lower limbs LARGE VEINS Have all tunica layers with
thin media and thicker externa layers ARTERIES vs VEINS Artery
walls are thicker - more muscle and elastic fibers in the tunica
media Lumen of the artery often looks smaller than that of a vein
because it recoils when not being stretched - looks pleated
Arteries retain cylindrical shape - veins often collapse Arteries
are more resilient - keep their shaped stretched Arteries dont have
valves CARDIOVASCULAR SYSTEM
SYSTEMIC SYSTEM - heart to body to heart left ventricle aorta
arteries of tissue or organ capillaries veins right atrium vena
cava PULMONARY SYSTEM - heart to lungs to heart right ventricle
pulmonary trunk pulmonary arteries lungs left atrium pulmonary
veins