Circulatory System Flashcard Set

The Circulatory system

A network of blood vessels that supply cells with nutrients and collect waste materials

Made up of:

• Blood: transport medium

• Blood Vessels: the transport vessels used 

• Heart: pumping mechanism 

Blood 

A collection of cells that have been specialized to perform a set of specific tasks; a connective tissue 

Functions of blood

• Circulates vital materials to your cells (e.g. O2, nutrients)

• Removes waste products of cell metabolism

• Equalize temperature in the body by delivering heat to extremities

• Defends body against disease (e.g. antibodies)

Components of blood:

• Red blood cells (erythrocytes) : bi-concave shape, no nucleus, transport O2 & CO2 through hemoglobin, live in body for 120 days (replaced w/ bone marrow), 45% of blood volume 

  • Oxygen carrying capacity: dependent on # of RBC and hemoglobin found in RBC - hemoglobin binds w/ oxygen

  • w/ hemoglobin body can survive for 5 mins

  • w/o hemoglobin = 4.5 seconds 

• White blood cells (leukocytes): colourless, have nuclei (produced in bone marrow), #s double/triple when fighting infection, defence against disease, complete phagocytosis, less than 1% of blood volume

  • Phagocytosis: when a leukocyte engulfs and digests harmful substances like bacteria, after the leukocytes release enzymes that destroy the bacteria and sometimes the leukocyte itself = pus

• Plasma: protein-rich liquid, blood cells and platelets are suspended in it, 90% water

• Platelets (thrombocytes): small, irregularly shaped cell fragments, no nuclei, breakdown in blood w/in 7-10 days, produced in bone marrow, in charge of blood clotting 

Blood clotting: 

• Begins when blood vessel is damaged

• Platelets rush to site → stick to collagen fibres = temporary clot 

• Below, fibrogen in the plasma becomes fibrin = forms mesh to trap more platelets 

Blood flow path:

Heart → large arteries → smaller arteries → arterioles → capillaries → venules → smaller veins → large veins → heart

Blood pressure:

Systolic - when the heart contracts 

Diastolic - when the heart relaxes 

Hypertension: consistently high blood pressure caused by medication, age, lifestyle 

• Heart has to work harder to pump blood around the body, blood vessels can rupture, heart attack or stroke can occur 

Arteries: 

Large blood vessels that carry blood away from the heart to cells and tissues 

• Thick muscular elastic walls 

• High pressure, blood travels in spurts b/c heart contracts forcing blood through artery = pulse 

Arterioles:

Smallest arteries that branch off from arteries = signals nervous system to regulate diameter of arterioles to control blood flow 

Veins:

Blood vessels that carry deoxygenated blood from cells and tissues back to the heart

• Thin, less muscular walls

• Low pressure, moved with the help of gravity, muscle contraction, venous valves 

Varicose veins: a condition where veins, particularly those near the surface of the skin in the legs, become enlarged, twisted, and dilated

• often due to increased blood pressure in the veins, leading to weakened or damaged valves that allow blood to flow backward, causing the veins to stretch and twist. 

Capillaries

Smallest blood vessel in the body, forms networks of blood vessels that supply every cell in the body with o2 and nutrients 

• Made up of a thin, single layer of cells 

• Blood pressure is extremely low, almost zero = nutrients and o2 are allowed to pass through into body cells and tissues + waste products and co2 are passed into the blood cells to travel into the veins and back to the heart

Automatic Nervous System aka the brain

The brain controls the diameter of blood vessels 

• Vasoconstriction: blood vessels contract = decrease in diameter of blood vessels = reduced blood flow to tissues, heat is taken back in 

• Vasodilation: blood vessels relax = increase in diameter of blood vessels = increased blood flow to tissues, heat is dispersed 

Circuits in the Circulatory System 

Pulmonary circuit: carries deoxygenated blood from the heart to the lungs and brings oxygenated blood back from the lungs to the heart = right side of the heart

Systemic circuit: carries oxygenated blood from the heart to the body and carries deoxygenated blood from the body back to the heart = left side of the heart

The Human Heart

• Muscular organ, about the size of your fist 

• Weighs about 10.5 ounces

• Located in the middle of your chest, breastbone protecting it at the front, spine protecting it in the back

• Heart is surround by fluid filled sac called the pericardium

• Beats 70 times per minute

Double pump: right pumps to the lungs, left pumps to the body

4 chambers of the heart - BLOOD FLOWS ATRIUM TO VENTRICLE 

• Right atrium

• Right ventricle

• Left atrium

• Left ventricle 

BLOOD FLOW STEPS: 

1. Deoxygenated blood enters the right atrium via the superior and inferior vena cava 

2. Blood flows to the right ventricle via the tricuspid valve 

3. The right ventricle pumps the blood to the lungs via the pulmonary valve and the left and pulmonary arteries 

4. Oxygen-rich blood returns from the lungs via the pulmonary veins 

5. The blood flows into the left ventricle via the mitral valve 

6. The left ventricle pumps blood up to the aorta via the aortic valve 

• The two atrioventricular valves prevent blood from entering the atria when the heart beats 

• Aortic valve prevents blood from moving into the aorta when heart is not beating

• Pulmonary valve prevents blood from moving from the pulmonary artery to the right ventricle when the heart is not beating 

Makes lubb-dubb sound 

• Lubb: atrioventricular valves closing as ventricle begin to contract

• Dubb: pulmonary and aortic valves closing as ventricles relax

The coronary arteries and veins provide blood circulation for the heart 

Heartbeat

Abnormal sounds: heart valves failing to close properly, can heart sound of blood leaking past to through the valve = murmur sounds 

• Heart muscle is myogenic = contracts and relaxes on its own 

  • Safety mechanism in place to make sure heart beats even if brain dead 

• Heartbeat initiated in cluster of cells in the right atrium called sinoatrial node (SA) = the “pacemaker”

• Gives signals to set normal rhythm of heartbeat

• Signals reach atrioventricular node (AV) 

• From AV node special conducting fibres called Purkinje fibres run down septum and throughout heart’s muscles cells

Electrocardiograph (ecg or ekg)

• Heartbeat is electrically stimulated

• Electrocardiograph detects electrical activity of heart through electrodes placed on body’s surface

  • ECG tracing shows strength and duration of electrical signals from heart.

  • Each repeating pattern represents one heartbeat.

P wave = atrial depolarization

QRS complex = ventricle depolarization

T wave = ventricle repolarization