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Circulatory System: Introduction
Circulatory System: Circulatory System: IntroductionIntroduction
Dr. Carmen E. RexachDr. Carmen E. RexachAnatomy 35Anatomy 35
Mt. San Antonio CollegeMt. San Antonio College
Components
• Cardiovascular system
• Lymphatic system
Cardiovascular system
• Heart, blood vessels, blood
• Functions:– transport of
nutrients, hormones, oxygen, waste, carbon dioxide
Lymphatic system
• Lymph nodes, lymphatic vessels, lymph
• Functions– Immune Response– Absorption of fat
from gi tract (lacteal)– Controlling volume of
interstitial fluid and blood
Cardiovascular system and Lymphatic system work in tandem
Hematology• Study of blood and components• Two parts
– Formed elements• Erythrocytes• Leukocytes• Thrombocytes (Platelets)
– Plasma
Hematocrit
Plasma (Blood Matrix)• Predominately water • Major solutes
– Salts– minerals– bicarbonate buffer– sugars, amino acids, vitamins
Plasma Proteins
• Predominately made in liver• Major plasma proteins
– Albumins– Lipoproteins– Clotting Factors– Globulins
• Including antibodies – Gamma globulins– made by lymphocytes
FormedElements
Formed elements
• Erythrocytes– Red blood cells– anucleate– lack mitochondria– millions of
hemoglobin molecules
– Life span = 3-4 months
Leukocytes• Nonspecific
– Neutrophils– Eosinophils– Basophils– NK cells– Monocytes,
macrophage• Specific
– T-lymphocytes– B-lymphocytes
granulocytes
Neutrophils (PMN’s)• the first WBC at an
infection site• 50-60% of circulating
leukocytes• voracious phagocytes• use lysozyme and
oxygen radicals to destroy microbes
Polymorphonuclear cells….can you tell why?
Eosinophils• slightly phagocytic• Effective against
helminths• Allergic and
hypersensitivity reactions
• Contribute to chronic inflammation
Note the large red stained granules
Basophils• mature into mast cells of
loose connective tissue• Smallest immune
effector cells• Produce:
– heparin • an anticoagulant
– histamine • Vasodilator• increases capillary
permeability• important to
inflammation, especially related to allergies
Note large blue granules
Monocytes
• Become macrophage when activated
• eat microbes cellular debris
• Antigen Presenting Cells– link nonspecific body
defenses to the immune responseLarge C-shaped
nucleus….and no granules!
Diapedesis
macropha
Lymphocytes• Involved in specific
immune response• Present in small
numbers until activated
• T cells primarily circulate, B cells primarily in lymph nodes Large nucleus almost
completely fills cell
Formed elements
• Thrombocytes– Formed by
disintegration of megakaryocytes
– Released into plasma
– Last 3-5 days– Important in blood
clotting
Platelet plug formation
• Activation of platelets makes them sticky
• Results in the formation of a platelet plug when blood vessel is damaged
The Heart• a dual pump (R and L)• Functions:
– 1) unidirectional flow of blood through heart and vessels
– 2) dual pump to lungs and systemic circulation to pick up oxygen, distribute it to tissues, carry CO2 back to lungs to be eliminated
– 3) develops blood pressure by alternate cycles of relaxation and contraction
Layers of heart wall• Endocardium
– Tunica intima of the heart– Composed of simple squamous epithelium + loose CT
• Myocardium– Tunica media – cardiac muscle
• branched• interdigitated• 1 centrally located nucleus• striated• intercalated discs
• Epicardium– Tunica externa or visceral pericardium – simple squamous epithelium and loose CT
• Parietal pericardium– a fibrous CT loose fitting sac – Lined with simple squamous epi.
Four chambers
• Dual pump– Functional
• Pulmonary circuit• Systemic circuit
– Two regions• Atria• Ventricles
Atria• thin walled receiving
chambers• derived from veins• auricles
– folded extensions of the atria
– increase volume• pectinate muscle
– atrial muscle, “honeycomb”appearance
Atria
• R atrium receives blood from the systemic circuit
• Openings– superior vena cava– inferior vena cava– coronary sinus (thebesian
valve)• L atrium receives blood
from the lungs• openings
– from pulmonary veins
Ventricles
• thick walled• pumping chambers derived
from arteries• trabeculae = “crossbars of
flesh”• R ventricle
– thinner wall– pumps to lungs– moderator bands control
the volume of the RV if present
• L ventricle– 2-3 X’s thicker than the RV– pumps to systemic circuit
Septa• cross walls or dividers of the hearts
– interatrial - between atria– interventricular - between ventricles– atrioventricular - between atria and
ventricles
Atrioventricular septum• Two parts
– 1. cardiac skeleton• a fibrous CT skeleton supporting the heart valves and
chambers– 2. heart valves (in the atrioventricular septum)
• atrioventricular (cuspid valves) between atria and ventricles
• semilunar valves between ventricles and major arteries
Atrioventricular valves• Function
– Permit atrioventricular flow– Prevent ventriculoatrial reflux
• Attached to accessory structures– chordae tendineae
• fibrous cords• “heart strings”
– papillary muscles • fingerlike muscles attached to
chordae tendineae• keep valves closed during
ventricular contraction
Semilunar (SLV) valves
• Between ventricles and major arteries– pulmonary trunk– aorta
• Permit– ventriculoarterial flow
• Prevent– arterioventricular reflux
Intrinsic conduction System
• sends rhythmic impulses through the heart to synchronize heart rate and stimulate contraction
• sinoatrial (SA) node– Pacemaker– located in R atrium near the superior
vena cava
Cardiac conduction system• Atrioventricular (AV) node
– first structure used to stimulate contraction of the ventricles, located near the center of the AV septum
• atrioventricular (AV) bundle – Bundle of HIS
• bundle branches – lead to the L and R ventricle respectively
• Purkinje fibers – terminal branches of the conduction system– continuous with cardiac muscle fibers.
Embryonic Development of the Heart
• day 18-20:– the entire embryo is disc shaped– all blood vessels begin as blood islands in splanchnic mesoderm
surrounding the head and neck
For more detailed information, http://pie.med.utoronto.ca/HTBG/HTBG_content/HTBG_heartEmbryologyApp.html
Dorsal view
Development of heart• day 20-21:
– embryo curls– the heart folds into the thorax & becomes a pair of
tubes
Heart Development
• day 22– pair of tubes fuse– heart begins
pumping – 4 bulges develop
(beginning at bottom: venous to arterial)
• sinus venosus• atrium• ventricle• bulbus cordis
Before 2 months
• the heart forms an S shape-
• ventricle moves caudally (to bottom)
• atrium moves cranially (to top)
By 2 months
• 4 distinct chambers develop
• interatrial septum grows caudally (from top to bottom)
• interventricularseptum grows cranially (from bottom to top)
• foramen ovale and a hole in the superior interventricularseptum retained until birth
• bulbus cordis splits into the pulmonary trunk and ascending aorta
Major CVS Circuits• 1. systemic
– high variable resistance circuit– Includes coronary circulation
• the vasa vasorum of the heart
• 2. pulmonary– low, constant resistance circuit