BIOL 66- Ch 13: Blood, Heart, and Circulation

Circulatory System

Organ system that transports molecules and other substances rapidly over long distances, between cells, tissues, and organs; O2, CO2, fatty acids, waste products

Circulatory system Divisions

Cardiovascular and Lymphatic

Cardiovascular system- components

Heart, vessels/vascular system, and blood

Cardiovascular system- components relations

cardiac muscle cells that pump, creates contraction (pressure) that pushes blood out of the heart, through vessels (vascular) traveling throughout the body

Heart

major pump of variable rate and strength

Vessels/Vascular System

pipes of variable diameters, interconnected system

Blood

Fluid (CT) of variable volume and viscosity- ability to flow, sticky and thickness; contains water, solutes, and cells; average 5.5L

Composition of blood- Hematocrit

hematocrit is a rapid assessment of blood compositions, it is the percent of blood volume that is composed of RBC

Composition of blood- Hemoglobin

Hemoglobin in RBCs carries O2 to tissues and CO2 away from tissues, like lung expiration

Composition of blood- Plasma

the fluid portion of blood, includes water, ions, proteins, nutrients, gasses, hormones, wastes, etc.

Composition of blood- White Blood Cells

WBC, leukocytes, for immunity

Composition of blood- Platelets

cell fragments for clotting

Centrifuge blood sample

causes plasma to seperate and move to the top

Centrifuge blood sample- layers top to bottom

blood plasma, Buffy coat (platelets and WBC) and formed elements (RBC, hematocrit height)

Circulation

the heart is a muscular pump that propels the blood through the pulmonary (lung) circulation and systemic (other organs and tissues) circulation; fully oxygenated when passing through lungs, partially oxygenated when delivering O2 to cells

Heart- Muscular organ

Cardiac muscle and endothelial cells; myocardium, muscular tissue of the heart; each cardiac muscle cell contracts with a heart beat

Heat- pumping action

Pumping action of the heart due to muscle contraction creates pressure to move blood quickly throughout the body

Heart- Septum

separates the right and left sides of the heart

Heart- Ventricle

lower chamber of the heart, pumps blood into arteries

Heart- Right Ventricle

Right ventricle pumps blood to the lungs via pulmonary arteries, pulmonary circulation

Heart- Left Ventricle

Left ventricle pumps oxygenated blood into the other tissues via aorta, systemic circulation

Heart- Interventricular septum

separates the two ventricles

Heart- Atrium

upper chambers of the heart, receives venous blood returning to heart

Heart- Right Atrium

Right atrium receives blood from systemic circulation, via venae cavae

Heart- Left Atrium

Left atrium receives blood from pulmonary circulation, via pulmonary veins

Heart- Fibrous Skeleton

Connective tissue that separate the atrium and ventricle

Blood circulation

blood is ejected through contraction of both ventricles at the same time during a specific phase; RA → tricuspid valve → RV → Pulmonary SL valve → Pulmonary a. → Lungs → Pulmonary v. → LA → Bicuspid valve → LV → Aortic SL valve → aorta → arteries → capillaries → veins → inferior and superior vena cava, repeats

Pulmonary circulation

circuit where partially oxygenated blood travels from the RV of the heart via the pulmonary arteries to the lungs, where blood picks up O2 from inspiration and releases CO2 from expiration, oxygenated blood then travels to LA and enters via pulmonary veins

Systemic Circulation

Circuit where oxygenated blood travels from LV via the aorta through the organ systems, then blood delivers O2 from inspiration and picks up CO2 for expiration, partially oxygenated blood travels back to the RA and enters via superior and inferior vena cava

Pulmonary circulation- summary

begins at RV, pulmonary a., low O2 artery content, pulmonary v., high O2 vein content, terminates at LA

Systemic Circulation- Summary

begins at LV, aorta and it’s branches, high O2 artery content, Superior and Inferior vena cava and branches, low O2 vein content, terminates at RA

Atrioventricular (AV) Valves

between the atria and ventricles; valves open and closes due to pressure difference across it, pressure can push a valve open or force it close

Atrioventricular (AV) Valves- Tricuspid valve

3 flaps; between RA and RV

Atrioventricular (AV) Valves- Bicuspid Valve

2 flaps; between LA and LV

Semilunar Valve- Pulmonary valve

between RV and pulmonary trunk (right and left pulmonary arteries)

Semilunar Valve- Aortic Valve

between LV and aorta

Cardiac Cycle- Diastole and Systole

Alternating contractions and relaxations of atria and ventricles (0.8s) until death occurs; ventricles must be filled with blood in order to occur

Systole

period of ventricular contraction and blood ejection, 0.3s; through systemic and pulmonary circulation, muscle cells contract

Diastole

period of ventricular relaxation and blood filling, 0.5s; filled with blood from aorta, muscle cells relax

Cardiac Cycle- Pressure

force exerted by blood due to heart contracting, mmHg

Cardiac Cycle- Blood Flow

from a region of higher pressure to region of lower pressure; volume/unit time, such as L/min

Heart sounds

two sounds heard through stethoscope; lub and dub; korotkoff sounds heard in brachial artery when taking manual blood pressure

Heart sounds- First sounds

soft, low-pitched “lub”; AV valve closed, at onset of systole, peak

Heart sounds- Second sound

louder “dub”; SL valve closure, at onset of diastole

Cardiac Cycle- Systole

1. isovolumetric contraction: pressure in ventricles increase as ventricle begins contraction, causing AV valves to close, lub

2. Ejection of blood into aorta and pulmonary trunk occurs when ventricular pressure exceeds aortic pressure (120 mmHg) so that SL valves open

Cardiac Cycle- Diastole

3. Isovolumetric relaxation: pressure in ventricles decreased, causing SL valves to close, dub, aortic pressure is 80 mmHg

4. When pressure in ventricle falls below atrial pressure, AV valves open and there is rapid filling of the ventricles (blood in atria → ventricles)

5. Atrial contraction delivers the final amount of blood into the ventricles just prior to #1 occurring again

Stroke Volume

when ventricles contract, amount of blood ejected; around 2/3 of the blood in the ventricles

End-diastolic volume (EDV)

volume of blood in ventricle at the end of diastole; amount actually being ejected

Contraction and relaxation of cardiac muscle cells

contraction= depolarize, relaxation= repolarize

Electrical Activity of the Heart- Sinoatrial node

depolarization in SA node initiates APs that spread to the rest of the cardiac cells leading to contraction

Electrical Activity of the Heart- AV node

carries APs from RA

Electrical Activity of the Heart- Bundle of His

where APs travel to ventricles

Sinoatrial Node

small group of cardiac muscle cells in RA; heart’s pacemaker; cells depolarize spontaneously and quickly; excitation causes contraction; APs spread through cells of atria via gap junctions, electrical synapses

Bundle of His

slow conduction in AV node, so ventricular contraction occurs after atrial contraction has ended

Electrocardiogram

ECG, EKG; detects electrical activity in the heart via electrodes on the surface of the skin; electrodes record current conducted through fluid around heart, caused by simultaneous APs in myocardial cells; sum of total cells

ECG waves

P, QRS, and T

P wave

results from the spread of atrial depolarization

QRS wave

results from spread of depolarization into the ventricles and repolarization of atrium

T wave

results from repolarization of the ventricles

ECG and APs

the relationship between ECG, recorded as the difference between currents at the left and right wrists, and an AP of a typical ventricular myocardial cell

Structure of Blood Vessels

CT, smooth muscle, and epithelial tissue (capillaries only have epithelial tissue); distribute blood to tissues, regulate BP; Closed loop; arteries branch into arterioles, vessels between arteries and capillaries; in capillaries (small blood vessels) there’s exchange of substances between cells and vessles like nutrients and waste; capillaries merge to form venules, vessels between capillaries and veins; venules merge into veins, going back to the heart

blood vessels- direction which blood loops

artery → arteriole → capillaries → venule → vein

Arteries

have strong, thick, elastic walls that assist flow; high pressure, low volume

Veins

have weaker walls and a wider lumen (hollow interior) and fill more easily; low pressure, high volume; act as volume reservoirs, 54% total volume, more than half the blood volume of the body here

Arterioles

the greatest pressure drop is in the arterioles; these vessels serve as controller of flow into capillary beds

Vasoconstriction of arterioles

contraction of their smooth muscle layer to decrease diameter, decreases blood flow

Vasodilation of arterioles

relaxation of smooth muscle layer to increase diameter, increases blood flow

Capillaries

Smallest blood vessels, mediate exchange of substances with ISF; in every tissue except cornea; single (thin) layer of epithelium allows rapid exchange of substances

Capillaries- Exchange of substances

gas exchange (O2, CO2), nutrient and waste exchange, cell secretions (how hormones get delivered to tissues)

Veins- blood flow

greatest total blood volume and can expand with greater blood volume; low pressure but blood flows back to the heart due to skeletal muscle pump, and the direction of flow is one-way due to venous valves in peripheral veins

Veins- pressure

pressure decreases as it gets farther away from source

Venous flow

Venous flow is assisted by the skeletal muslce pump (pushes blood to heart, up) mechanism working in combination with one-way venous valves, prevents back flow

Veins during muscle contraction

when muscle contracts, vein are partially compressed → diameter reduction, venous pressure increase, and increase volume of blood returning to the heart

Coronary Artery Disease

insufficient blood flow (ischemia) to heart due to change in coronary arteries (arteries that nourish heart); can cause heart attack, myocardial infarction

Atherosclerosis

primary cause in coronary arteries; thickening of arterial wall with plaques that include cholesterol and fat deposits

Coronary Artery Disease- Risk Factors

hypertension, stress, smoking, obesity, sedentary lifestyle, diabetes, high cholesterol

Thrombus

blood clot; can stick to plaque

Plaque

build up of fat and cholesterol

Lymphatic System- transport

transport excess ISF that filters out of blood vessels back to the blood; transports fat absorbed from the SI into the blood

Lymphatic System- Lymphocytes

defend against disease-causing agents

Lymphatic System- Lymph Nodes

filter lymph to remove pathogens before the fluid is returned to the blood

Lymphatic System- Lymphatic fluid

lymph, mainly immune system function