(LESSON 14) Circulatory System: Blood and Heart Flashcards
Subdivisions of the Circulatory System
Cardiovascular system and lymphatic system
Cardiovascular System
blood, heart, and blood vessels
erythrocytes
Red Blood Cells(RBC’s).
- Most numerous formed element:
- Cells in a cubic millimeter:
- Females: 4.3 to 5.2 million
- Males: 5.1 to 5.8 million
- 25 trillion are present in the bloodstream of a healthy adult
- Cells in a cubic millimeter:
- 7.5 microns in diameter
- biconcave discs
- anucleate bag of hemoglobin (aka: no nucleus. Hemoglobin: oxygen-carrying protein)
- Transport oxygen and CO2
Leukocytes
White Blood Cells (WBC)
- Less numerous than erythrocytes
- 4800 to 11,000/cubic millimeter
- Crucial to body’s defense against disease
- Spherical in shape
- Only formed elements that are complete cells (nucleus and oragnelles)
Buffy Coat
Thin gray layer at the junction of erythrocytes and plasma. Contains **leukocytes **(white blood cells) that protect the body and thrombocytes (platelets) which are cell fragments that help stop bleeding.
Hematocrit
“Blood fraction” The percentage of blood volume that consists of erythrocytes. Averages 45 but varies. Males=47%+/-5% and females si 42%+/-5%. In newborns can be 42-68%. Leukocytes and platelets consititute less than 1% of blood volume and plasma makes up remaining 55%
Blood plasma
straw-colored, sticky fluid. About 90% water.
- Contains over 100 different kinds of molecules such as Na+ and C1-.
- Nutrients such as simple sugars, amino acids, and lipids.
- Wastes such as urea, ammonia, CO2
- Also oxygen, hormones, and vitamins
- 3 proteins: albumin, globulins and fibronogen
Albumin
Protein in blood plasma. Helps keep water from diffusing out of the bloodstream into the extra cellular matrix of tissues.
Globulins
Protein in blood plasma. Includes both antibodies and the blood proteins that transport lipids, iron, and copper.
Fibrinogen
Protein in blood plasma. involved in a series of chemical reactions that achieves blood clotting with other protein and nonprotein molecules.
Coagulation
When blood stands, the chemical reaction that occurs, producing:
- a clot entangles the formed elements
- a clear fluid called serum
(Serum is plasma from which clotting factors have been removed)
Features of Blood Cells
(Formed elements of blood)
- Neither erythrocytes nor platelets are true cells
- Erythrocytes lack nuclei and organelles
- Platelets are merely cell fragments
- Most of the formed elements cannot divide. They survive in the blood stream for just a few hours to a few months, being replaced by new cells produced in the bone marrow. Formed elements are broken down and components recycled.
The main classes of blood cells
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Diapedesis
(Leaping Through)
The process where leukocytes leave the capillary walls, targeting infection sites producing dangerous chemicals.
- Leukocytes actively squeeze between endothelial cells that form the capillary walls
- cells travel to the infection site by **amoeboid motion: **forming flowing cytoplasmic extensions that move them along, functioing outside of the bloodstream in loose connective tissue.
Leukocytosis
When a leukocyte count exceeds 11,000/cubic millimeter during an infection or inflammation.
5 types of leukocytes
2 groups
- Granulocytes: contain many obvious granules
- neutrophils-
- eosinophils
- basophils
- Agranulocytes: lack obvious granules
- lymphocytes
- monocytes
From most abundant to least abundant:
“Never Let Monkeys Eat Bananas”
Neutrophils, lymphocytes, monocytes, eosinophils, basophils
Platelets
AKA Thrombocytes.
- Platelets are not cells but cytoplasmic fragments.
- They contain chemicals needed for clotting.
- Hemophilia—sex-linked disorder occurring primarily in males; factor VIII deficiency
Hematopoiesis
AKA Hemopoiesis.
The process by which blood cells are formed.
- Occurs in red bone marrow at the rate of 100 billion cells/day
Hemocytoblast
Blood stem cells that create:
- erythrocytes
- leukocytes
- platelets
Bone Marrow
Occupies the interior of all bones. If all bone marrow in the skeleton were combined it would form the second largest organ in the body, next to the skin.
- Red Marrow
- Yellow Marrow
Red Marrow
The only marrow that actively generates blood cells. Red hue is derived from the immature erythrocytes it contains.
Yellow marrow
Dormant. Makes blood cells only in emergencies that demand increased hematopoiesis. Color reflects the many fat cells it contains.
Genesis of Erythrocytes
Erythropoiesis
- An immature erythrocyte produces large numbers of ribosomes.
- Erythrocytes synthesize hemoglobin.
- Erythrocytes retain hemoglobin but reject the nucleus and most organelles.
Erythrocyte Destruction
- The cell can’t grow, divide, or synthesize protein.
- It becomes “old” in approximately 100 days.
- The spleen traps and fragments degenerating erythrocytes.
- Iron is salvaged, heme is degraded to bilirubin, and the rest of the cell is digested by macrophages.
Disorders of Erythrocytes
- Polycythemia
- Anemia
- Sickle Cell Disease
Polycythemia
(Many blood cells) Disorder of Erythrocytes
- Abnormal excess of erythrocytes in the blood.
- Can result from bone marrow cancer
- Causes an increase in viscosity of the blood, which slows/blocks the flow of blood through smaller vessels.
- Treated by dilution-removing some blood and replacing it with sterile physiological saline
Anemia
(Lacking blood) Disorder of erythrocytes
- Any condition in which RBC levels or hemoglobin concentrations are so low that the blood can’t carry sufficient oxygen.
- Caused by:
- blood loss
- iron deficiency
- destruction of erythrocytes at rate which exceeds replacement
- vitamin B12 or Folic Acid deficiency
- genetic defect of hemoglobin
- Symptoms:
- constantly tired
- often pale
- short of breath
- often cold due to lack of oxygen to tissue
Sickle Cell Disease
Formerly Sickle Cell Anemia. Disorder of Erythrocytes.
- Inherited, primarily by people of Central African descent
- 1 of every 400 African Americans apprx.
- Hemoglobin defect
- Abnormal hemoglobin crystalize when oxygen in blood is low or RBC’s are dehydrated. (Exercise, anxiety)
- Circulating RBC’s distort into shape of crescent (sickle cell), become rigid, fragile, and easily destroyed. Also block vessels.
- Symptoms:
- severe bone and chest pain
- infections
- stroke
- Some new drugs have helped this not be fatal
- Bone marrow transplant can offer cure, however:
- 10% death rate
- 20% rejection rate
Disorders of Leukocytes
- Leukemia: cancer of the blood
- Leukocytosis: an excess of leukocytes, indication of infection or inflammation
- Infectious mononucleosis: caused by the Epstein-Barr virus; results in the production of excessive number of agranulocytes
Pulmonary circuit
Blood vessels that carry blood to and from the lungs
Systemic Circuit
the vessels that transport blood to and from all body tissues
Atrium
Entranceway. The heart has two receiving chambers, left and right atriums, that receive blood returning from the systemic and pulmonary circuits.
Ventricles
Hollow-Belly. The heart has two main pumping chambers, the right and left ventricles, that pump blood around the two circuits.
HEART:
Size, location, and orientation
- It is about the size of a fist.
- It is divided into four chambers- 2 atria and 2 ventricles.
- It weighs approximately 300 grams (less than a pound).
- It is enclosed in the mediastinum.
- The base is the posterosuperior portion of the heart.
- The apex of the heart is directed inferiorly toward the left hip.
Pericardium
triple layered sac that encloses the heart.
Fibrous Pericardium
the outer layer of pericardium that is a strong layer of dense connective tissue. Adheres to diaphragm inferiorly and is fused to the roots of the great vessels that leave and enter the heart superiorly. Holds heart in place and keeps it from overfilling with blood
Serous Pericardium
a closed, double layered sac sandwiched between the fibrous pericardium and the heart.
Parietal layer of serous pericardium
adheres to the inner surface of the fibrous pericardium.
visceral layer of the serous pericardium
epicardium
lies on the heart and is considered a part of the heart wall.
Pericardial cavity
a slit like space between the parietal and visceral layers of the serous pericardium. A lubricating film of serous fluid is secreted into the cavity to reduce friction between the beating heart and the outer wall of the pericardial sac.
Epicardium
Visceral layer of serous pericardium. Infiltrated with fat, especially with older people. Outer layer of heart wall.
Myocardium
forms the buld of the heart. “Muscle heart”. Consists of cardiac muscle tissue and is the layer that actually contracts.
endocardium
inside the heart. Located deep to the myocardium, a sheet of endothelium resting on a thin layer of connective tissue. Lines heart chambers, covers heart valves.
Right Atrium
- forms right border of human heart.
- Receiving chamber for oxygen-poor blood returning from the systemic circuit from 3 veins
- superior vena cava
- inferior cena cava
- coronary sinus
Right Atrium
Forms the entire right border of the human heart, superior, is the receiving chamber for oxygen-poor blood returning from the systemic cicuit.
Receives blood from:
- superior vena cava
- inferior vena cava
- coronary sinus
Right auricle
(part of right atrium)
a small flap haped like a dog’s ear. Auricle=little ear. projects anteriorly from superior corner of atrium.
Pectinate muscle
(Part of right atrium)
“Like the teeth of a comb”. Lined by horizontal ridges, within the auricle and anterior wall of the atria.
Crista terminalis
“terminal crest” C-shaped ridge that separates the smooth posterior wall and the anterior pectinate muscle of the right auricle. Helps locate where veins enter right atrium.
Fossa ovalis
a depression in the interatrial septum that marks the spot where an opening existed in the fetal heart.
Right Ventricle
- Forms most of the anterior surface of the heart
- inferior portion of the heart.
- Receives blood from the right atrium and pumps it into the pulmonary circuit via the pulmonary trunk
- Superiorly the opening between the right ventricle and the pulmonary trunk contains the pulmonary semilunar valve (pulmonary valve)**
- Contain:
- Trabeculae carnae
- papillary muscle
- chordae tendinae
Pulmonary Trunk
A large vessel on the anterior superior portion of the heart that receives blood from the right ventricle and directs it to the lungs via the pulmonary arteries.
Trabeculae carneae
“Little beams of flesh” Irregular ridges of muscle that line the ventricular walls internally.
Papillary muscles
cone shaped muscles that project from the walls into the ventricular cavity
Prevent AV valves from everting
chordae tenineae
“tendinous cords” Thin strong bands that project superiorly from the papillary muscles to the flaps (cusps) of the tricuspid valve. “tugging on heart strings”
Left atrium
- makes up most of the heart’s posterior surface or base.
- Receives oxygen-rich blood returning from the lungs through two right and two left pulmonary veins.
- Internally most of the atrial wall is smooth with pectinate muscle lining the auricle only
Left Auricle
anterior part of the atrium, flap like extension
Left Ventricle
- forms the apex of the heart and dominates the hearts inferior surface.
- Pumps blood into the systemic circuit.
- Superiorly opens into the stem artery of the systemic circulation (aorta) through the aortic semilunar valve (aortic valve)
- Also contains:
- trabeculae carneae
- papillary muscles
- chordae tendineae
- cusps of atrioventricular (mitral) valve
Veins
- inferior vena cava
- superior vena cava
- coronary sinus
- pulmonary veins
- two vessels from each lung that return oxygenated blood to the heart’s left atrium.
Arteries
- pulmonary arteries
- paired branches of the pulmonary trunk that direct deoxygenated blood to the lungs to be oxygenated
- aorta
Right Atrioventricular (tricuspid) valve
separates atrium and ventricle on the right side. Prevents backflow into the right atrium during ventricular contraction.
left atrioventricular (bicuspid or mitrial) valve
separates atrium and ventricle on the left side. Prevents backflow of blood into the left atrium during ventricular contraction.
Pulmonary semilunar valve
separates right ventricle and left pulmonary artery. Precents backflow from of blood from the pulmonary trunk to the right ventricle during ventricular relaxation.
Aortic Semilunar valve
separates left ventricle and aorta. Three half-moon shaped cusps that prevent backflow of blood from the aorta to the relaxed left ventricle.
Fibrous Skeleton
Lies in the plane between the atria and the ventricles and surrounds all four heart valves like handcuffs. Composed of dense connective tissue.
Functions:
- Anchors valve cusps
- prevents overdilation of the valve openings as blood pulses through
- point of insertion for bundles of cardiac muscle in atria and ventricles
- blocks direct spread of electrical impulses from the atria to the ventricles.
- critical for proper coordination of atrial and ventricular contractions
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- critical for proper coordination of atrial and ventricular contractions
Valve function
Valves prevent backflow of blood.
Atrioventricular Valve backflow
Prevent backflow of blood into the atria during contraction of ventricles. Relaxed (diastole) ventricles allow for blood flow from atria to ventricles. When ventricles contract, pressure in ventricles rises and forces blood superiorly against the valve cusps, closing the valves. Chordae tendinae and papillary muscles keep valves closed and anchored.
When atria contract, AV valves open, SL valve is closed.
When ventricles contract, AV valve is closed and SL valve is open.
Semilunar Valve Backflow
Prevent backflow from the great arteries into the ventricles. When ventricles contract and raise intraventricular pressure, the semilunar valves are forced open and their cusps are flattened against the arterial walls as the blood rushes past them. When the ventricles relax, blood that tends to flow back toward the heart fills the cusps of the semilunar valves and forces them shut.
Valve Disorders
The mitral valve, and the aortic valve to a lesser extent, are most often involved in valve disorders because they are subjected to the great forces resulting from contraction of the the powerful left ventricle.
Mitral Valve Prolapse
an inherited weakness of the collagen in the valve and chordae tendineae allows one or both cusps of this valve to “flop” into the left atrium during ventricular systole. Affecting 2.5%-5% of the populartion, this is the most common heart valve disorder. Characterized by a click followed by a swish. Can lead to heart failure though most cases are mild and harmless.
Conducting System
- Cardiac muscle cells have the intrinsic ability to generate or conduct an impulse and contract.
- The components, listed in sequential order, are the sinoatrial node, atrioventricular node, atrioventricular bundle, bundle branches, and Purkinje fibers.
- Heart chambers sequentially contract in response to the impulse conduction path just listed.
- The SA node is the origin of the conducting impulse and thus it sets the rate of the heartbeat (the pacemaker)
The need of a pacemaker
Damage to the AV node and AV bundle cause a **heart block, **which interferes with the ability of the ventricles to receive the pacing impulses. Ventricles beat at slower rate and cannot maintain adequate circulation, the a pace maker to discharge contractions at a sufficient rate.
Heart murmurs
this is the sound that can be heard when there are disorders in the valves. It is the sound of the backflow of blood.
Atherosclerosis
an accumulation of fatty deposits in the inner lining of the body’s arteries that can block blood flow through these arteries.
Coronary Artery Disease (CAD)
When atherosclerosis affects the coronary arteries. The arteries supplying the heart wall are narrowed or blocked.
Angina Pectoris
A common symptom of CAD. Thoracic pain caused by inadequate oxygenation of heart muscle cells, which weaken but do not die. Occurs most often during exercise when the heart demands more oxygen than the narrow arteries can deliver.
Myocardial Infarction
When the blockage of a coronary artery is more complete or prolonged, the oxygen-starved cardiac muscle cells die. This is a heat attack.
- Sharp pain strikes with lightning speed through the chest (sometimes left arm and left side of neck) and does not subside
- Death from cardiact arrest occurs almost immediately in about 1 of 3 cases.
- Kill directly through severe weakening of the heart
- kill indirectly due to heart-rhythm disruptions caused by damage to the conducting system
Silent ischemia
A painless but fatal heart attack. Blood flow to the heart is interrupted often, as in angima, but wihtout any pain to provide warning. Can be detected with ECG during exercise.
Neutrophils
- consume and destroy bacteria
- by phagocytosis
- by releasing bacteria destroing substances into extracellular matric
- Most abundant leukocyte
- about 60% of all white blood cells
- **pus **is composed of dead neutrophils and other leukocytes and tissue debris
Eosinophils
- Granulocyte
- Rare: 1-4% of all leukocytes
- helps end allergic reactions and parasites by:
- phagocytizing allergens
- secreting substance
- Fighting parasites is the most important role of eosinophils
Basophils
- Granulocyte
- Rarest of white blood cells: account for .5% or 1 in 200
- Mediate inflammation during allergic response and parasitic infections.
Lymphocytes
- Agranulocytes
- Most important cells of the immune system
- 20-45% of all leukocytes
- Fight infectious organisms with T cells and B cells
- T Cells: attack foreign bodies directly.
- develop immunocompetence in the thymus
- B Cells: differentiate and produce antibodies (proteins) that bind to the antigen and marks it for destruction by the microphages.
- T Cells: attack foreign bodies directly.
Monocytes
- Agranulocytes
- the largest leukoctyes
- 4-8% of white blood cells
- Once they reach the connective tissue from the blood stream they transform into macrophages
Macrophages
- Transformed monocytes
- Phagocytic cells that move by amoeboid motion through connective tissue and ingest a wide variety of foreign cells, molecules, and tiny particles of debris.
Blood flow through the heart
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Ascending Aorta
receives blood immediately from the left ventricle
Coronary arteries
vessels that branch immediately from the ascending aorta, supply blood to the myocardium. (right, left, marginal, circumflex, etc)
Aortic Arch
curved portion of the aorta that extends superior and posterior to the pulmonary trunk.
descending aorta
Portion of the aorta that descends from the aortic arch and continues inferiorly until it divides into the common iliac arteries.
Sinoatrial Node SA Node
- The impulse that signals each heartbeat begins here. (pacemaker)
- Mass of cells that lie in the wall of the right atrium
Atrioventricular Node AV Node
Purkinje Fibers
- Subenocardial branches
- approach the apex of the heart then turn superiorly into ventricular walls
- ensure that the contraction of the ventricles begins at the apex of the heart and travels superiorly so blood is ejected superiorly ino the great arteries
- Modified muscle that is adapted for conduction
Conducting system of heart
- specialized muscle cells that carry impulses throughout heart musculature, signaling the heart chambers to contract in the proper sequence
Innervation of the heart
Atrial Contraction
- SA node sends impulse that signal each heartbeat
- 70-80 impulses/min
- signal spreads throughout myocardium through gap junctions in intercalated disks
Innervation of the heart
Ventricular Contraction
- From SA node, signals spread in a wave along cardiac muscle fiber of atria, signaling atria to contract
- Some signals travel along internodal pathways to the **atrioventricular (AV) node **in the inferior part of the interatrial septum
- There signals are delayed for a fraction of a second
- After delay, impulses race through the atrioventricular bundle which enters the interventricular septum
- There signals divide into left and right bundle branches (crura)
- Halfway down the septum crura become purkinje fibers, which ensure that contraction occurs at apex to force blood superiorly into great arteries
