Circulatory SystemProvides O2 and nutrients to all body cells and removes

wastes.

Structure of the Heart - Fig. 12-1, 12-2; located within mediastinum and rests on the diaphragm

Coverings of the heart Enclosed in a layered pericardium Pericardial space between layers is fluid

filled Wall of heart

Endocardium – inner layer Myocardium – middle; mostly cardiac

muscles Epicardium (visceral pericardium) –

outer layer

Structure of the Heart - Fig. 12-1, 12-2; located within mediastinum and rests on the diaphragm

Heart Chambers, Valves & Blood Flow Heart is divided into 4 chambers – 2

atria, 2 ventricles R. chambers and valves – O2 poor blood

R. atrium receives blood from superior & inferior vena cava & coronary sinus

Blood passes through tricuspid valve to R. ventricle

Blood passes through pulmonary semilunar valve to L. & R. pulmonary arteries ***only arteries to carry O2 poor blood***

Structure of the Heart - Fig. 12-1, 12-2; located within mediastinum and rests on the diaphragm

Heart Chambers, Valves & Blood Flow L. chambers and valves – O 2 rich

Blood returns from lungs via L. & R. pulmonary veins ***only veins to carry O2 rich blood***

O2 rich blood dumps into L. atrium Blood passes through bicuspid valve into L.

ventricle Blood passes through aortic semilunar valve

to aorta Distributed to the rest of body (systemic

circulation)

Structure of the Heart - Fig. 12-1, 12-2; located within mediastinum and rests on the diaphragm

Structure of the Heart - Fig. 12-1, 12-2; located within mediastinum and rests on the diaphragm

Structure of the Heart - Fig. 12-1, 12-2; located within mediastinum and rests on the diaphragm

http://www.youtube.com/watch?v=mH0QTWzU-xI (blood flow through the heart)

http://vimeo.com/8321006 (animation - blood flow)

Actions of the Heart Cardiac Cycle

Pressure within chambers rises & falls in repeated cycles

Contraction of heart – systole Relaxation of heart – diastole

When atria are relaxes (atrial diastole) blood flows into them from veins (about 70% of blood flows directly into ventricles)

When atria contract (atrial systole) the remaining 30% of blood flows into ventricles

As ventricles contract (ventricular systole) bicuspid/tricuspid valves are pressed closed; blood flows either to lungs or body

Stroke volume = volume of blood ejected from ventricles

http://www.youtube.com/watch?v=jLTdgrhpDCg

Actions of the Heart Heart Sounds

Described as lub-dub Due to the vibrations produced by the

blood & valve movements Lub – occurs as A-V valves are

closing/ventricles contract Dub – occurs as semilunar valves are

closing/ventricles relax

Actions of the Heart http://www.youtube.com/watch?v=te_SY3MeW

ys

Actions of the Heart Cardiac Conduction System – Fig. 12-7

Composed of specialized cardiac muscle tissue and functions to initiate and conduct depolarization waves through the myocardium

Signal is initiated by S-A node located in upper part of R. atrium (known as the pace maker of the heart). Ability to excite themselves Impulses spread into surrounding myocardium Atria contract

Actions of the Heart Cardiac Conduction System – Fig. 12-7

Impulses travel slowly from S-A node (so atria have time to contract) to A-V node located in lower part of R. atrium Impulses now travel quickly to A-V bundle

(bundle of His) and then to Purkinje fibers Ventricles contract – muscle fibers in

ventricular walls are arranged in whorls that “wring” blood out of ventricles

Actions of the Heart Regulation of the Cardiac Cycle

Heartbeat is affected by physical exercise, body temp. and concentration of various ions

Parasympathetic impulses cause a decrease in heart rate

Sympathetic impulses cause an increase in heart rate

Blood Vessels – Closed circuit of tubes; - Fig.

Blood Vessels – Closed circuit of tubes; - Fig. 12-9

Arteries & Arterioles Adapted to carry relatively high

pressure blood AWAY from the heart Arterioles are branches of arteries Walls of arteries consist of layers of

endothelium, elastic membrane, smooth muscle, and connective tissue ***walls of arteries are thicker than walls of veins or capillaries***

Blood Vessels – Closed circuit of tubes; - Fig. 12-9

Capillaries – form connections between arterioles & venules Consist of a single layer of cells that

forms a semipermeable membrane Capillary density varies directly with

tissue metabolic rates Muscle & nerve – rich supply Cartilaginous, epidermis, cornea (low

metabolic rates) lack capillaries

Blood Vessels – Closed circuit of tubes; - Fig. 12-9

Capillaries – form connections between arterioles & venules Capillary flow is regulated by opening &

closing of precapillary sphincters Open when cells are low in O2 Close when cellular needs are met

Blood Vessels – Closed circuit of tubes; - Fig. 12-9

Capillaries – form connections between arterioles & venules Gasses, nutrients, and metabolic by-products

are exchanged between capillary blood & tissue fluid Diffusion provides the most important

means of transport Filtration due to the hydrostatic pressure of

blood causes outward movement of fluid at the arterial end of capillary

Osmosis causes a net inward movement of fluid at the venule end of a capillary

Blood Vessels – Closed circuit of tubes; - Fig. 12-9

Capillaries – form connections between arterioles & venules

Blood Vessels – Closed circuit of tubes; - Fig. 12-9

Capillaries – form connections between arterioles & venules

Blood Vessels – Closed circuit of tubes; - Fig. 12-9

Veins & venules Venules continue from capillaries and

merge to form veins Veins carry blood TOWARD the heart Contain valves to keep blood moving

toward the heart Venous walls are similar to arterial

walls, but are thinner and contain less muscle and elastic tissue.

Blood Vessels – Closed circuit of tubes; - Fig. 12-9

http://www.youtube.com/watch?v=HNuPWdfjDoc

Blood Pressure Blood pressure is the force exerted by blood

against the insides of the blood vessels – Fig. 12-16 (also see – Clinical Application pg. 327)

http://www.youtube.com/watch?v=0L3hV-PLlC4 (how to take blood pressure)

Arterial blood pressure Produced primarily be heart action; rises &

falls with phases of the cardiac cycle Systolic pressure occurs when the ventricles

contract; diastolic pressure occurs when the ventricles relax

Blood Pressure

Blood Pressure Factors that influence arterial blood

pressure Blood Volume

An increase in volume causes an increase in pressure

A decrease in volume causes a decrease in pressure

Blood Pressure Factors that influence arterial blood pressure

Heart Action Volume of blood discharged from L. ventricle with

each contraction is called stroke volume (70ml – 75ml) Cardiac output = volume discharged in 1 minute Cardiac output = stroke volume x heart rate (ex. 75ml x 70 beats/min. = 5250 ml/min)

If stroke volume increases & heart rate stays the same the cardiac output increases causing an increase in blood pressure

Blood Pressure Factors that influence arterial blood pressure

Peripheral Resistance – friction between the blood and the walls of the blood vessels An increase in PR causes an increase in bp A decrease in PR causes a decrease in bp

Viscosity – physical property – thickness An increase in viscosity causes an increase

in bp A decrease in viscosity causes a decrease

in bp

Blood Pressure Control of Blood Pressure – heart rate is

regulated by different portions of medulla oblongata

Venous Blood Flow Not a direct result of heart action; it depends

on skeletal muscle contraction, breathing movements, and venoconstriction

Many veins contain flaplike valves that prevent blood from backing up

Blood Pressure Central Venous Pressure – pressure in the

R. atrium Influenced by factors that alter flow of

blood into R. atrium Ex. – A weak heart causes an increase

in pressure in R. atrium which causes the flow of blood to slow which causes pressure to increase in peripheral veins

Paths of Circulation

Paths of Circulation Pulmonary Circulation

Composed of vessels that carry blood from R. ventricle to lungs and back to l. atrium

Pulmonary capillaries contain lower pressure than systemic capillaries (R. ventricle contracts with less force than L. ventricle

Exchange of oxygen and carbon dioxide; tightly joined epithelial cells of alveoli prevent most substance from entering alveoli

Paths of Circulation Pulmonary Circulation

Paths of Circulation Systemic Circulation http://www.youtube.com/watch?v=0jznS5psypI

Vessels that carry blood from L. ventricle to body cells and back to R. atrium

Includes aorta & branches & system of veins Hepatic portal – the route of blood flow through

the liver (fig. 12-14); blood passes through 2 capillary beds before returning to the heart

Renal circulation – the route of blood through kidneys (fig. 17-3 pg. 443); blood passes through 2 capillary beds before returning to the heart

Coronary Circulation – The delivery of oxygen & nutrients and the removal of carbon dioxide & wastes from cardiac muscle tissue

Paths of Circulation Hepatic Portal Circulation

Paths of Circulation Renal Circulation

Paths of Circulation Coronary

Circulation

Fetal Blood & Circulation Blood is carried between the placenta and the fetus

by umbilical vessels Fetal blood carries more O2 than maternal blood Blood enters fetus through umbilical vein (O2 rich)

and partially bypasses the liver by means of the ductus venosus

Blood enters R. atrium & partially bypasses the lungs by means of the foramen ovale

Blood entering the pulmonary trunk partially bypasses the lungs by means of the ductus arteriosus

Blood enters umbilical arteries from the internal iliac arteries (O2 poor)

Fetal Blood &

Circulation

http://www.youtube.com/watch?v=OV8wtPYGE-I

http://www.mhhe.com/biosci/genbio/virtual_labs_2K8/labs/BL_14/index.html (Virtual Blood Pressure Lab)