Post on 26-Dec-2015
Cardiovascular SystemUnit 10
Structure and Function
Three parts: Heart Blood vessels Blood
Function = transports oxygen, nutrients, cell wastes, hormones, etc., distributes body heat
Anatomy of the Heart
Approximately the size of a fist, hollow, cone-shaped
Inside the bony thorax between the lungs
Pointed apex is angled toward left hip, rests on the diaphragm at the same level as the fifth intercostal space
Broader base points towards right shoulder blade, beneath second rib
Anatomy of the Heart
Anatomy of the Heart
Enclosed by a double sac of serous membrane = pericardium
The thin epicardium hugs the external surface of the heart and is part of the heart wall
Myocardium = thick middle layer made of thick bundles of cardiac muscles twisted into ring-like arrangements, this is the layer that actually contracts
Endocardium = thin inner layer, lubricated sheet of endothelium, continuous with the linings of the blood vessels leaving and entering the heart, allows blood to flow more smoothly
Pericarditis = inflammation of the pericardium, causes pericardial layers to stick to each other, forming painful adhesions that interfere with heart movements
Anatomy of the Heart
Anatomy of the Heart
Four chambers Atria = top chambers, receive blood
Right atrium = receives from body, deoxygenated blood
Left atrium = receives from lungs, oxygenated blood Ventricles = bottom chambers, pump blood out
of heart Left ventricle = pumps to body, oxygenated blood Right ventricle = pumps to lungs, deoxygenated
blood Interventricular and interatrial septum =
divides heart longitudinally
Anatomy of the Heart
Major Heart Vessels
Vena cava = brings blood from body to right atrium Superior vena cava = blood from above the
heart Inferior vena cava = blood from below the heart
Pulmonary veins = bring blood from lungs to left atrium
Aorta = large artery that carries blood from left ventricle to rest of body
Pulmonary arteries = carry blood from right ventricle to lungs
Major Heart Vessels
Heart Valves
Allow blood to flow in only one direction: atria ventricles arteries
Atrioventricular valves (AV) = between atrial and ventricular chambers Bicuspid valve= two cusps (flaps of endocardium),
between left atrium and ventricle, also known as mitral valve
Tricuspid valve = three cusps, between right atrium and ventricle
Chordae tendineae – “heart strings,” anchor cusps to ventricles, help keep them closed
Semilunar valves = base of the two large arteries Pulmonary semilunar valve = base of pulmonary artery Aortic semilunar valve = base of aorta
Heart Valves
How does the heart beat?
Double pump – right side = pulmonary (lungs), left side = systemic (rest of body)
Both atria contract together and both ventricles contract together
How does the heart beat? Cardiac cycle = start of one heart beat
to the initiation of the next Heart usually beats ~75 times per minute Cardiac cycle usually lasts ~0.8 seconds
Systole = heart contraction Diastole = heart relaxation Three main phases of cardiac cycle:
1. Mid-to-late diastole 2. Ventricular systole 3. Early diastole
How does the heart beat?
1. Mid-to-late diastole: Heart in complete relaxation pressure in heart is low, blood is
flowing passively into the atria Semilunar valves are closed AV valves are open The atria contract and force the blood into the ventricles
2. Ventricular systole: The pressure building in the ventricles closes the AV valves, then
opens the semilunar valves Blood rushes out of ventricles into arteries Atria are relaxed during this phase and starting to fill up with
blood again 3. Early diastole:
Ventricles relax and semilunar valves close to prevent backflow ventricles are completely closed chambers, pressure drops
When the pressure drops low enough, the AV valves open
How does the heart beat? Cardiac muscles can contract spontaneously,
even if all nervous connections are severed. Different rhythms in different areas of the
heart atria = 60 beats/minute, ventricles = 20-40 beats/minute needs unifying control
Two main systems: intrinsic conduction system (nodal system) and autonomic nervous system
Autonomic nervous system acts like “brakes” or “gas pedal” decrease or increase heart rate
How does the heart beat? Intrinsic conduction system is built into the heart
tissue – found nowhere else in the body Causes heart depolarization from atria to ventricles Enforces rate of ~75 beats per minute Path of signal:
Sinoatrial (SA) node – right atrium “pacemaker” Atrioventricular (AV) node – junction of atria and
ventricles Atrioventricular (AV) bundle (bundle of His) – junction of
atria and ventricles Right and left bundle branches – to right and left of
bundle of His Purkinje fibers – spread throughout ventricle muscle walls
Warm up video questions – Copy on your own paper
1. What is the new craze sweeping the nation? 2. “Out through your ______, in through your
________.” 3. What are two signs that you’re “not
circulating right?” (These are mentioned at different times in the video).
4. What are the four parts of the heart mentioned in the song?
5. What does circulation take to your cells? 6. What does circulation get rid of for your cells? 7. What jobs do red and white blood cells have? http://www.youtube.com/watch?v=5tTkxYeNF9Q
Electrocardiogram (ECG)
Traces the flow of electric current through the heart
3 waves: P wave – small, signals depolarization of
atria before they contract QRS complex – the “peak,” symbolizes
depolarization of ventricles before they contract, repolarization of atria is generally hidden by this complex
T wave – repolarization of ventricles
Electrocardiogram (ECG)
Blood Vessels
Blood circulates through the body in a closed transport system “vascular system”
Leaves the heart in large arteries Moves to smaller arteries arterioles
capillary beds Capillary beds drain into venules small
veins veins leading to heart Arteries, arterioles, veins, and venules =
transporting blood Capillaries = where the exchange between
tissue cells and blood occur
Blood Vessels
Blood Vessels
Blood vessels (except for capillaries) have three coats, or tunics
Tunica interna – Lines the interior of the vessels, thin layer of endothelium resting on loose layer of connective tissue, cells fit close together to make slippery surface that decreases friction as blood flows through
Tunica media – bulky middle coat, smooth muscle and elastic tissue, controlled by sympathetic nervous system, changes diameter of blood vessels and therefore, blood pressure
Tunica externa – outermost layer, fibrous connective tissue, supports and protects vessels
Blood Vessels
Blood Vessels
Arteries tend to have thicker walls than veins Some larger arteries even have elastic laminae,
complete sheets of elastic tissue within their tunica media
Arteries must be able to expand as blood is forced into them and relax when it leaves during diastole walls must be strong and stretchy to handle continuous changes in pressure
Veins have thinner walls and have much lower pressure Sometimes have to work against gravity Lumens are larger than those in arteries Valves to prevent backflow of blood Skeletal muscles help “milk” blood back to heart Inhaling also causes a drop in pressure that causes the
big veins near the heart to expand and fill
Blood Vessels
Capillary walls are just one cell layer thick easier to make exchanges between blood and tissue cells
Capillary beds = interweaving networks of tiny capillary vessels
Microcirculation – flow of blood from arteriole capillary bed venule
Two parts to capillary bed: Vascular shunt – vessel that connects to
arteriole and venule at opposite ends of bed True capillaries – actual exchange vessels,
10-100 per bed
Blood Vessels
Capillaries form such an intricate network so that no substance has to diffuse very far to enter or leave a cell
Space between tissue cells and capillaries is filled with interstitial fluid
Substances move according to their concentration gradients high to low
Can take one of four “routes:” 1. Diffuse directly across plasma membrane if they are lipid
soluble (ex. Respiratory gases) 2. Endocytosis or exocytosis – moving within vesicles 3. Fluid can flow through intercellular clefts (gaps between
cells) 4. Small solutes and fluids can move through fenestrated
capillaries, which are usually found where absorption or filtration is a priority (ex. Intestine, kidneys)
Only substances that cannot pass through these “routes” will remain in capillaries (ex. Proteins, blood cells)
Important arteries
Ascending aorta Aortic arch Thoracic aorta Abdominal aorta Right and left
common iliac arteries Brachiocephalic artery Right and left
subclavian arteries Right and left
common carotid arteries
Important Veins
Superior and inferior vena cava Brachiocephalic vein Internal and exterior jugular veins Vertebral vein Subclavian vein Basilic vein Cepalic vein Hepatic portal vein Hepatic veins Renal veins Internal, external, and common
iliac veins Great saphenous vein (longest in
body) Femoral vein Fibular vein Anterior and posterior tibial veins
Special Circulations – Brain
Need continuous blood supply to the brain Two pairs of arteries: internal carotid arteries and vertebral
arteries Internal carotid arteries go through neck and temporal
bone, then divides into anterior and middle cerebral arteries Vertebral arteries go through base of neck then join inside
the skull to form basilar artery, which serves the brain stem and cerebellum. It then divides again to form the posterior cerebral arteries.
Anterior and posterior blood supplies are connected by small communicating arterial branches a complete circle of connecting blood vessels called the circle of Willis
Circle of Willis protects brain by providing more than one route for blood to reach the brain in case of clots or impaired blood flow
Special Circulations - Brain
Special Circulations – Hepatic Portal
Drains blood from digestive organs, spleen, and pancreas and delivers it to the liver through the hepatic portal vein
Liver processes the nutrients from food to help maintain the balance of glucose, fat, and protein concentrations in the blood some get removed for storage
Liver is drained by hepatic veins inferior vena cava
Unique because normally arteries capillaries veins, but in this case, veins feed the liver circulation
Special Circulations – Hepatic Portal
Special Circulations - Fetal Nutrient, excretory, and gas exchanges all happen
through placenta because lungs and digestive system are not yet functioning.
Nutrients and oxygen move from mother to baby while wastes move in the other direction.
Umbilical cord has three blood vessels: one umbilical vein and two umbilical arteries
Vein carries blood with nutrients and oxygen to baby while the arteries carry CO2 and other waste to the placenta
Blood flows mainly to the heart of the fetus, bypassing the immature liver through the ductus venosus which enters the inferior vena cava
Special Circulations - Fetal Since lungs aren’t being used, two shunts help
bypass them Blood entering right atrium goes straight to left
atrium through foramen ovale Blood that makes it to the right ventricle is
pumped out pulmonary trunk to ductus arteriosus, where it is pumped back to the aorta.
At birth, the foramen ovale closes and the ductus arteriosus collapses and is converted to fibrous ligamentum arteriosum (connects aorta to pulmonary artery)
Special Circulations - Fetal
Physiology of Circulation
Pulse – rhythmic expansion and recoil of arteries resulting from heart beating can be felt outside of body when an artery is close to the body surface
Pulse can be influenced by activity, postural changes, and emotions
Pressure points – points where pulse can be most easily felt; they are compressed to stop blood flow during hemorrhaging
Physiology of Circulation
Blood pressure = pressure blood exerts against inner walls of blood vessels
The force that keeps blood circulating continuously, even between heartbeats blood moves from high to low pressure
Systolic pressure – pressure in the arteries at the peak of ventricle contraction
Diastolic pressure – pressure when ventricles are relaxing
Blood pressure is measured in millimeters of mercury (mm Hg) and with the systolic pressure over the diastolic pressure (ex. 120/80)
Hypertension = chronic high blood pressure (140/90 or higher)
Physiology of Circulation
Blood pressure is usually measured through the auscultatory method:
Blood flow is stopped through an inflated blood pressure cuff.
As the pressure in the cuff is slowly released, the examiner listens carefully for two signals.
The first signal is a soft tapping sound as blood starts to spurt through the artery this is recorded as systolic pressure.
The second signal is when the tapping sound can no longer be heard this point is recorded as diastolic pressure
Physiology of Circulation
Blood pressure is directly related to cardiac output and peripheral resistance (the amount of friction encountered by the blood as it flows through the vessels)
Factors that can affect blood pressure: Age Weight Time of day Exercise Body position Emotional state Drugs Kidneys Temperature Diet