Chapter 2 - The Circulatory System Flashcards
What is an open circulatory system?
When blood leaves blood vessels.
Unicellular animals, like the Amoeba, use what system of transport?
An open circulatory system
Diffusion is sufficient for transport of materials
What is a closed circulatory system?
Blood is confined to blood vessels
Used in multicellular animals.
Characteristics of a closed circulatory system?
Blood confined to blood vessels
Blood flows in one direction only
Allows of faster distribution and the controlled distribution of blood around the body
Allows alterations in blood flow to body organs e.g during exercise more oxygen is delivered to the muscles.
What does the human circulatory system consist of?
Blood vessels
The heart
Blood
Tell me about arteries
Carry blood away from the heart
Have high pressure
Have thick walls and narrow lumens
Do not have valves
Carry oxygen-rich blood (except for the pulmonary artery)
Divide into smaller vessels called arterioles
Tell me about veins
Carry blood to the heart
Have low pressure
Have thin walls and large lumens
Have valves
Carry oxygen-poor blood (except for the pulmonary vein)
Small veins are called venules
Layer structure in Arteries and Veins
Outer layer of tough inelastic protein called collagen which prevents the walls from over-expansion
A middle layer of muscle and elastic fibres. The muscle can alter the size of the vessel and therefore alter the blood pressure and the volume of blood being carried. This allows arteries to dilate during exercise so more blood flows to the leg muscles
An inner layer of living cells called the endothelium which surrounds the lumen.
The lumen is the central blood filled space
Differences between arteries and veins
Arteries : Carries blood away from the heart Blood under high pressure Thick walls Small lumen Blood flows in pulses Valves absent Blood rich in 02
Veins: Carries blood to the heart Blood under low pressure Thin walls Large lumen Blood flows smoothly with no pulses Valves present Blood low in 02
Tell me about capillaries
Capillaries connect arteries to veins, have thin walls and allow exchange of materials.
Their walls are made of a single layer of endothelium cells
Capillary walls are permeable so they allow exchange of materials between the blood and body tissues
No valves or pulse as low Blood pressure
Lumen is very narrow
Carry both oxygenated and deoxygenated blood
Adoptions of capillaries for gaseous exchange
Porous and wall is only one cell thick providing a shorter diffusion distance
Blood flows slowly through capillaries allowing more time for exchange of materials
Vast number of capillaries provides a high surface area for efficient exchange
Define what an arteriole is. What can they do? What is their role?
Materials are tiny branches of arteries that lead to capillaries
They can constrict and dilate to regulate blood flow
Their role is to transport blood from the arteries to capillaries they are also the main regulators of blood flow and pressure
What are venules? What is their role?
Venules are small veins formed went capillaries join together
Their role is to drain blood from capillaries to veins for return to the heart. Many venules unite to form a vein.
Define Blood Pressure
BP is the force blood exerts against the wall of a blood vessel
Where is blood pressure highest?
In the arteries when the heart contracts
This pressure causes the artery to expand slightly which can be detected as a pulse
Where is blood pressure lowest?
In the veins
In the veins ordinary body muscles contract and this squeezes the veins and help to return the blood to the heart
What do valves do?
They control the direction of blood flow by preventing backflow of blood, ensuring blood flows towards the heart.
Location of the heart?
Located in the middle of the thorax, under the sternum, between the two lungs to the left hand side of the chest just above the diaphragm
What is the heart made of?
Cardiac muscle and surrounded by a double membrane called the pericardium
Pericardial fluid between these membranes help to reduce friction with nearby organs when the heart beats
Tell me about cardiac muscle
Very elastic
Does not fatigue
Receives its own blood supply through the cardiac (coronary) blood vessels
What to coronary arteries do?
Bring oxygenated blood to the cardiac muscle of the heart. Two coronary arteries arise from the base of the Aorta, just beyond the semi-lunar valve.
What do coronary veins do?
Return de-oxygenated blood directly to the right atrium
Top two chambers of the heart are called the..
Atria
Bottom two chambers of the heart are called the…
Ventricles
What do the atria do?
Pump blood to the lower chambers or ventricles
Distance is short so they have thin walls
What do the ventricles do?
Pump blood out of the heart
Where does the right ventricle pump blood?
The the lungs
Where does the left ventricle pump blood?
The the head and body
Much farther distance to pump blood so wall of left ventricle is much thicker
Valves are connected to the walls of the heart by projections called…
Papillary muscles
Valve between the right atrium and right ventricle is called …
3-flap tricuspid valve
Valve between the left atrium and left ventricle is called…
2-flap bicuspid valve
What valves are found at the base of both the pulmonary artery and the aorta?
Semi-lunar valves
What is the septum?
A middle muscular wall which divides the heart into two sides.
Ensures that o2 rich and o2 poor blood don’t mix
Blood flow in the heart
LORD
Left oxygenated Right deoxygenated
Describe blood flow in the right side of the heart
Blood enters heart via SUPERIOR & INFERIOR VENA CAVA.
Blood rich in CO2
Flows into the right atrium, tricuspid valves open and blood is forced down into the ventricles. The valves close to prevent backflow
The heart PULSATES and forces the blood up through the SEMI-LUNAR VALVES & out of the PULMONARY ARTERY.
Valves close to prevent backflow.
Blood is taken to lungs to remove Co2 and collect o2
Describe blood flow in the left side of the heart
Blood returns from the lungs rich in o2 via the PULMONARY VEIN. There are 2 one from each lung.
Blood enters the atrium and fills the chamber
BI-CUSPID valves open and blood flows down into the ventricles. The valves close to prevent backflow
Heart then pulses and the blood is forced up through the semi lunar valves and out the AORTA and all around the body
The coronary artery is the first branch off and this takes blood to the heart muscle itself.
Double circulation
Pulmonary circuit
Heart to lungs and then back to heart
Double circulation
Systematic circuit
Heart to rest of body and back to the heart
What happens in the pulmonary circuit?
Heart - lungs - heart
Right ventricle pumps blood around the pul circuit
In this circuit blood gains o2 and looses co2 in the lungs
The circuit is short so walls of right ventricle are thin
What happens in the systematic circuit?
Heart - body - heart
Left ventricle pumps oxygenated blood to the head, arms, trunk, and legs
Much longer route so walls of left ventricle are ticker & stronger than the right ventricle.
Double vs Single Circulation
Advantages?
Double separates the oxygenated blood from deoxygenated blood
Ensures BP is high enough to reach all parts of body
Allows a rapid and efficient delivery of nutrients
Single circulation system can only produce low bp around most of the body. This restricts the activities of the animal e.g earthworm and fish
What is a portal system?
One which begins and ends in capillaries
It is a blood supply that flows from ONE ORGAN DIRECTLY to ANOTHER ORGAN WITHOUT passing through the HEART.
EXAMPLE - hepatic portal vein brings blood rich in digested food but lacking in o2 from the intestine directly to the liver. It does not transport lipids.
Outline the control of the heartbeat
Electrical impulses cause contraction of the heart
Impulses are produced by SA node or pacemaker located in the right atrium
Tell me about the SA and AV nodes in the heart. What is their process of functioning?
The pacemaker pulses and causes the atria to contract
This stimulates the AV node located further down in the right atrium
The AV node sends an impulse down special muscle fibres located in the septum
The impulse is passed out to the walls of the ventricles by thin fibres. The impulse from these pulses causes the ventricles to contract
What does the pacemaker do? What changes the rate at which the pacemaker operates?
Controls the rate of the heartbeat
Nerves from the brain can change the rate at which the pacemaker operates
Changes in heartbeat
Factors that increase the heartbeat?
Exercise
Temperature
Emotions
Shock
Factors that decrease the heartbeat
Relaxation
Sleep
Alcohol
What is diastole?
Diastole is when the heart chambers relax
What is systole?
This is when the heart chambers contract
3 stages of the Heartbeat
Simple stages
Blood enters the heart
Blood is pumped from the atria to the ventricles
Blood leaves the heart
Outline what happens when blood enters the heart
What conditions are present within the heart?
The atria and ventricles are both relaxed (diastole)
Blood enters the atria
All valves are closed
Outline what happens when blood is pumped from the atria to the ventricles
Electrical impulses from the pacemaker cause atria to contract (atrial systole)
This pumps blood to the ventricles
The tricuspid valves and bicuspid valves open
The vena cava and pulmonary veins close to stop blood entering the atria
The semi lunar valves remain closed
Outline what happens when blood leaves the heart
The atria relax and impulses from the AV node cause the ventricles to contract (ventrical systole)
Blood is forced out of the heart into the pulmonary artery and the aorta
This pressure forces the semi lunar valves to open and closes the cuspid valves ( causing the ‘lub’ sound)
The ventricles now relax again
Closing the semi lunar valves prevents blood flowing back into the ventricles
The closure causes the dub sound
What is a pulse and What causes it? Where can it be felt?
Its is the expansion and contraction of an artery as blood is forced through it
Left ventricles contract - pressure of the blood forced into the aorta causes the aorta to expand
Felt in neck or wrist
What is the average pulse (heart) rate of an adult ?
72 beats per min
Where is blood pressure measured?
In an artery in the upper arm
What type of two blood pressures are measured? What is the average blood pressure of a healthy adult?
Systolic and diastolic pressures of the ventricles
120/80 mm Hg
If the ______ pressure is above ____ the person is suffering from ____ blood pressure
Diastolic
Above 95
High BP (hypertension)
What are the main causes of high BP?
Blockages in the arterioles or small arteries
These cause the heart to pump harder and may lead to a stroke ( lack of blood to the brain) , heart attack and death
Effects of smoking on the circulatory system
Nicotine raises heart rate and blood pressure thus increasing the work load of the heart
Carbon monoxide destroys the oxygen carrying ability of RBC. This results in lower energy production by the body
Other chemicals in tobacco increase blood clots occurring (thrombosis)
Main dietary factors affecting the circulatory system?
Saturated fats
- causing blocked arteries
- Raising cholesterol levels and increases risk of heart disease
High salt intake raises blood pressure
Being greatly overweight raises BP and causes heart attacks
What does cholesterol do?
Increases the risk of forming blockages in arteries, especially the coronary arteries and those leading to the brain
Blockages result in heart attacks and strokes
What does exercise do for the heart and circulation?
Enlarges and strengthens the heart
Improves overall circulation
Stimulates the formation of more capillaries in working muscles
Definition of blood pressure? What does it depend on?
The force exerted by the blood on the walls of the arteries due to the contacting of the heart
It depends on the volume of blood within the system and the space available within the blood vessels
What are the main functions of the blood?what do they transport and defend against
Transport food, waste products, hormones by plasma
Transport heat
Transport o2 by RBC
Defend against disease ( WBC )
Platelets clots blood
Define what blood is
A complex fluid connective tissue which is pumped through the closed blood vessels of the circulatory system
Plasma proteins- name the two types
Antibodies and Clotting proteins
Role of plasma
Transport - carries dissolved substances such as glucos, carbon dioxide, salts, urea and hormones
Carries heat around the body - homeostasis: maintaining a constant internal environment
Serum is plasma which has the clotting proteins removed. Still contains antibodies - used as injections to boost immune system
Where are RBC produced
In the bone marrow of large bones like the femur
Shape of RBC
Bi concave disks
Past exam Q 2009
What is the role of the SA and AV nodes in the heart?
SA
The pacemaker
Causes atria to contract
Generates an electrical impulse
AV
Causes the ventricles to contract
Mock exam Q
From what major artery do the coronary arteries emerge
Aorta
Mock Q
Give the precise location of the point of origin of the coronary arteries
At the base of the aorta , just beyond the semi-lunar valves
Mock Q
Explain why blood flow only occurs in the cardiac muscle during diastole
Blood may only enter the atria of the heart when all the chambers are relaxed
Mock Q
Name the structure into which the cardiac veins drain their blood
The right atrium
Heart dissection
Describe how you dissected a heart in order to investigate the internal structure of atria and ventricles (9 marks = 3 points for 3 marks each point)
1) safety precaution : wear gloves, goggles and lab coat.
2) identify the front ( ventral) and back of the heart
3) Place heart on a dissection board, front ventral side facing up
4) use a scalpel to make incisions
Incision 1 = shallow cut in the left atrium and left ventricle
Incision 2 = along front side of heart, on the right side, 1cm away and parallel to first incision
State the procedure that you followed to expose a semi lunar valve
Cut open the aorta or pulmonary artery
Where in your dissection did you find the origin of the coronary artery
At the base of the aorta, near the semi-lunar valve
