Cardiovascular System

Cardiovascular System

Characteristics of Blood

• Connective tissue• Plasma and cells• Transports substances

between body cells and the external environment

Blood Volumes

• Varies with body size, fluid and electrolyte concentrations, and amount of adipose

• Average adult volume – 5 liters (4-5 L for women, 5-6 L for men)

• Hematocrit – usually 45%

Blood Cell Types

• Erythrocytes – RBCs• Leukocytes – WBCs• Thrombocytes -

platelets

Red Blood Cells (RBCs)

• Biconcave disks that thin near the centers increased surface area for transporting gases

• Have nuclei early in development, but extrude them

• No nucleus – more room for hemoglobin, but cannot reproduce or make proteins

Hemoglobin

• Oxygen-carrying protein

• 1/3 of each RBC• Gives blood its color• Oxyhemoglobin• Deoxyhemoglobin• Hypoxia• Cyanosis

Red Blood Cell Counts

• RBCC – the number of RBCs in 1 mm3 of blood

• Adult male average – 4.6 – 6.2 million

• Adult female average – 4.2 – 5.4 million

• Determines blood’s oxygen carrying capacity

• Important diagnostic tool

Blood Cell Production • RBCs are normally

flexible, elastic, and able to pass through small blood vessels

• More fragile as they age

• Macrophages phagocytize and destroy damaged RBCs in the liver and spleen

Breakdown of Hemoglobin

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White Blood Cells (WBCs)• Function to protect against

disease– Phagocytize bacterial cells

– Produce antibodies

• Move by diapedesis• 2 main types:

– Granulocytes – neutrophils, eosinophils, and basophils

– Agranulocytes – monocytes and lymphocytes

Granulocytes

• Lobed nucleus with 2-5 sections

• Dark staining nucleus and pale granules

• 54-62% of WBCs• Contain many

lysosomes – actively phagocytizes bacteria

Granulocytes

• Contains coarse, uniformly sized granules

• 2 lobes on nucleus• Stains red• 1-3% of WBCs• Kills parasites• Helps control inflammation

and allergic reactions

Granulocyte

• Fewer, more irregular granules than eosinophils

• Granules stain deep blue• Less than 1% of WBCs• Contain heparin (inhibits

blood clotting) and histamine (increases blood flow to injured tissues)

Agranulocytes

• Largest blood cells• May live weeks

months• 3-9% of WBCs• Discussed later

Agranulocyte

• Form in red bone marrow and lymphatic system

• Slightly larger than RBCs• Large, round nucleus with

rim of cytoplasm• May live for years• 25-33% of WBCs• Discussed more later

White Blood Cell Count (WBCC)

• Number of WBCs in 1 mm3 of blood

• Adult average – 5000 – 10,000 cells

• Leukocytosis• Leukopenia• Differential WBCC (DIFF)

– More neutrophils – bacterial infection

– More eosinophils – parasitic infection, allergic reaction

• Leukemia

Platelets• Not complete cells• Form from megakaryocytes

that fragment• Lack nuclei• Half size of RBCs• Live 10 days• Average count – 130,000 –

360,000 cells• Help close breaks in

damaged blood vessels• Initiate formation of blood

clots

Plasma• 92% water• Functions include:

– Transporting nutrients, gases, and vitamins

– Regulating fluid and electrolyte balance

– Maintaining pH

Plasma Proteins

Hemostasis

• Vasospasm• Platelet plug formation• Coagulation• Fibroblasts invade clot

Hemostasis

Blood Groups

• ABO blood group is based on the presence or absence of 2 major antigens (RBC surface molecules)

• 4 possible combinations:– A

– B

– AB

– O

Rh Blood Group

Cardiovascular System – Pulmonary and Systemic Circuits

System Overview

• System consists of the heart and the blood vessels

• Function: to bring oxygen and nutrients to all body cells and to remove waste

Heart Location

Coverings of the Heart

• Pericardium– Fibrous pericardium

– Parietal pericardium

– Visceral pericardium

• Pericardial cavity• Pericardial fluid

reduces friction

Walls of the Heart

• Epicardium• Myocardium• Endocardium

– Purkinje fibers

Heart Chambers

• 4 chambers of the heart– Atria

• Thin walls• Receive blood returning to the

heart• Auricles

– Ventricles• Thicker walls• Receive blood from atria• Force blood out of heart

• Septum

Heart Valves

• Atrioventricular valves– Tricuspid – right– Bicuspid – left

• Semilunar valves– Pulmonary – right– Aortic – left

• Chordae tendinae• Papillary muscles

Blood Supply to the Heart

• Coronary arteries• Cardiac veins• Coronary sinus

Cardiac Cycle

• Cardiac cycle – series of events that constitute a complete heartbeat

• Systole – contraction• Diastole – relaxation

Cardiac Cycle

• Heart Sounds – “lub-dup”

• Lub – ventricular systole– AV valves close

• Dup – ventricular diastole– SL valves close

• Murmur

Cardiac Conduction System

• Coordinates the events of the cardiac cycle

• Consists of clumps and strands of specialized cardiac muscle that initiate and distribute impulses throughout the myocardium

Nodes of Cardiac Conduction System

• Sinoatrial node – AKA “pacemaker”– Just beneath

epicardium

– Located in right atrium near opening of superior vena cava

– Initiates impulses without nervous stimulation

Nodes of Cardiac Conduction System

• Atrioventricular node– Located in inferior portion

of septum

• AV bundle (bundle of His)– Large fibers run through the

interventricular septum

• Purkinje fibers– Spread from septum into

papillary muscles

– Stimulate ventricular contraction

Regulation of Cardiac Cycle

• Parasympathetic and sympathetic fibers from medulla oblongata run to the nodes – Secrete acetylcholine

to decrease heart rate– Secrete norepinephrine

to increase heart rate

• Cardiac center

Electrocardiogram (ECG)

• Recording of the electrical changes in the myocardium during the cardiac cycle

• P – atrial systole• QRS – ventricular

systole; covers atrial diastole

• T – ventricular diastole

Blood Vessels

Arteries

• Strong, elastic vessels that carry blood away from the heart

• Lead to finer branches called arterioles

Artery Layers

• Tunica interna – simple squamous epithelium for smooth surface

• Tunica media – largest layer; smooth muscle and elastic CT

• Tunica externa – CT that attaches artery to surrounding tissues

Capillaries• Smallest diameter blood

vessels• Extensions of inner lining of

arterioles• Connect arterioles and venules• Allow exchange between

blood and tissue fluid• More abundant around

muscles and nerves• Blood flow controlled by

precapillary sphincters• Exchanges occur by diffusion,

osmosis, and filtration

Veins• Carry blood back to the right

atrium of the heart• Form from microscopic

venules that are continuous with capillaries

• Structure similar to arteries, but less developed tunica media

• Many have valves to prevent blood backflow

• Act as blood reservoirs when hemorrhage causes decrease in arterial blood pressure

Blood Pressure• The force blood exerts against

the inner walls of blood vessels• Refers primarily to arterial

blood pressure• Increases during ventricular

systole – systolic pressure (100-140)

• Decreases during ventricular diastole – diastolic pressure (70-90)

• Pulse

Factors that Affect Blood Pressure

• Heart action – how much blood enters arteries

• Blood volume

• Peripheral resistance – friction between blood and vessels

• Blood viscosity

• Hypertension and stroke