The Circulatory System [5] Flashcards
Function of circulatory system
Transport system, linking cells of all systems and maintains homestasis. Link between body cells and external environment that supplies their requirements
What are the functions of blood?
- Transport oxygen, nutrients, waste, hormones, heat
- Maintain pH, water content and ion concentration in fluids
- Protect against pathogens
- Prevent blood loss
How much blood for each gender
Female: 4-5 L
Male: 5-6 L
%composition of plasma
55% of blood volume
%composition of erythrocytes
40-45% of blood volume
%composition of leucocytes
1% of blood volume
%composition of thrombocytes
<1% of blood volume
What is plasma (composition and function)
Liquid component of blood, mostly water with dissolved substances e.g. sugar and salts
Transports blood components through the body (cells, nutrients, hormones, waste, proteins, antibodies)
Describe structure of erythrocytes
Biconcave, no nucleus, live for 120 days, haemoglobin,
State primary function of erythrocytes
Transport oxygen from lungs to cells
Primary function of leucocytes
Protect body from infection
What are granulocytes and its three types
Leucocytes that are granular (grainy) cytoplasm and lobed (not spherical) nucleus
Neutrophils, eosinophils, basophils
What are agrabulocytes and its two types
Leucocytes that are agranular (not grainy) cytoplasm, spherical nucleus
Lymphocytes and monocytes
What are neutrophils
Granulocyte
Most common type of leucocytes
Enzymes that digest pathogens
What are eosinophils
Granulocyte
Leucocytes that lead to inflammatory responses to large parasites like worms
What are basophils
Granulocyte
Lead to allergic reactions, producing heparin and histamine to defend against parasites and bacteria
What are lymphocytes
Agranulocytes
Involved in immune response
T-lymphocytes for cell mediated immunity
B-lymphocytes for antibody mediated immunity
What are monocytes
Agranulocyte
Form cells (such as macrophages) that engulf pathogens or unusable cells through phagocytosis
What are thrombocytes and their function
Platelets, small fragments of cells
Allow blood clotting
How is oxygen carried in the blood (%)
97% in haemoglobin
3% dissolved in plasma
How much does haemoglobin increase the blood’s O2 carrying capacity?
60-70×
O2 + Haemoglobin =
oxyhaemoglobin
When does oxyhaemoglobin form
When O2 concentration is high, HbO2 forms
When O2 concentration is low, HbO2 breaks down into Hb and O2
Oxygenated vs deoxygenated blood appearance
haemoglobin = bright red
oxyhaemoglobin = dark red
thus arteries = red
veins = dark red
How are red blood cells well suited to oxygen transport?
Haemoglobin - combines with O2
No nucleus - more space for Hb, more flexible
Biconcave - more surface area for O2 exchange, thicker edges provide larger volume for haemoglobin
How is carbon dioxide transported in the blood?
(%)
7-8% dissolved in plasma
22% in carbaminohaemoglobin (CO2 + Hb)
70% as bicarbonate ions (HCO3-) suspended in plasma
How are bicarbonate (HCO3-) and hydrogen (H+) ions formed and broken down?
CO2 reacts with H2O to form carbonic acid (H2CO3), which ionised into hydrogen and bicarbonate
At alveoli, H+ and HCO3- recombine to form carbonic acid, which is broken down by enzymes into CO2 and water. CO2 diffuses into alveoli
How are organic / inorganic nutrients transported in the blood
All substances are dissolved in the plasma (besides CO2):
Inorganic: as ions (Na²+, Ca²+, K+, Cl-, I-)
Organic: as whole molecules (glucose, vitamins, amino acids, fatty acids, glycerol)
What metabolic wastes do blood remove and why is this important
Wastes are harmful to the body if accumulated (e.g. urea, creatinine, uric acid)
State the three steps of blood clotting
Internal walls of the blood vessel becomes rough, allowing thrombocytes to stick. Sticking platelets attract more. Platelets release vasoconstrictors that prolong muscle constriction
Describe Vasoconstriction
Muscles in the walls of damaged arteries constrict to reduce blood flow
Describe platelet plug
Internal walls of the damaged blood vessels become rough, allowing platelets to stick and attract more, reducing blood flow
Platelets and injured cells release vasoconstrictors, chemicals that prolong muscle constriction
Describe coagulation
For more serious injuries, blood clotting occurs
Chemicals (clotting factors) react to form FIBRIN, an insoluble protein that threads to form a mesh that traps material
CLOT or THROMBUS
Describe clot retraction
Fibrin contracts, becoming denser and stronger, pulling damaged vessels together
SERUM is squeezed out and dried, forming a scab
What is the thrombin system?
How fibrin is made
1) Platelets and injured cells release thromboplastin
2) Thromboplastin reacts with Ca²+ and PROTHROMBIN to form thrombin
3) Thrombin converts fibrinogen to fibrin
What happens if a thrombus breaks loose inside the body
Lodges in a vital blood vessel in the heart or brain, cutting blood flow, causing heart attack or stroke
What is pericardium?
Membrane holding the heart in place, but allowing it to move.
Also prevents overstretching
What is the wall of the heart made of
Cardiac muscle, muscle that doesn’t need rest
What separates the two sides of the heart?
Septum
Function of right side of the heart
Receive deoxygenated blood from body and pumps it to lungs
Function of the left side of the heart
Receive oxygenated blood from the lungs and pumps it to body
Function of right atrium
Receives blood from body and passes it to right ventricle
Function of right ventricle
Pumps blood to lungs
Function of left atrium
Receives blood from lungs and passes it to left ventricle
Left ventricle
Pumps blood to body
Why is wall of left ventricle thicker
Needs more strength to pump blood through body
Purpose of valves in the heart
Ensure blood flows in one direction
Two types of valves in the heart
Atrioventricular and Semilunar
Structure and function of atrioventricular valves
Held by tendons, chordae tendineae, attached to papillary muscles
Closes to prevent blood in ventricles from being pumped back up into atria
Structure and function of semilunar valves
Closes to prevent blood in arteries from flowing back into ventricles
Tricuspid valve structure + function
Three cusps, prevents blood from flowing from right ventricle into right atrium
Mitral valve structure + function
2 cusps, prevents blood from flowing from left ventricle to left atrium
Pulmonary valve structure + function
3 cusps, prevents blood from flowing from pulmonary artery into right ventricle
Structure + function of aortic valve
3 cusps, prevents blood from flowing from aorta to left ventricle
Function of blood vessels and three types (don’t describe)
Carry blood from heart to body/lungs and back
Arteries, veins, capillaries
Size hierarchy of blood vessels
Arteries > arterioles > capillaries > venules > veins
Structure + function of arteries (don’t go into detail)
Carry blood away from heart
Smooth muscle and elastic fibres
How does the smooth muscle in arteries affect blood flow
Muscles DON’T contract to move blood
Vasoconstriction: contracts, reduces diameter, hence blood flow
Vasodilation: relaxes, increases diameter, hence blood flow
Structure + function of arterioles
Smallest arteries with smooth muscle and elastic fibres
Supply capillaries with blood
Smooth muscle is especially important in regulating pressure
What is the purpose of fibres in arteries
Allow artery walks to stretch when ventricles pump blood, and recoil when they relax.
Why are wastes used as vasodilators
Wastes (CO2, lactic acid, urea) are indicators of metabolic activity
Body recognises they need to be removed, and additional nutrients are required
Hence, arteries widen to allow more blood flow
Structure and function of capillaries
Microscopic links between veins and arteries, forming a network reaching almost every body cell
One cell thick walls, allows for easy diffusion of substances between cells and blood
Structure and function of veins (don’t go into detail)
Carry blood towards heart
No muscles, not elastic, thin walls
Have valves
Explain blood pressure in veins
Constantly low pressure, as blood loses most of its pressure in capillaries
Why are veins not muscular and elastic
As blood pressure is lower in veins, they don’t need to change diameter to move blood.
Why do veins have valves
Due to low blood pressure, veins have valves to prevent backwards flow
Define blood flow
Movement of blood through circulatory system, delivering nutrients while removing wastes
How does blood flow adapt to body requirements
By changing:
- volume of blood output from heart
- diameter of blood vessels
Define the cardiac cycle
Sequence of events in one heartbeat
Define systole
Contraction of heart muscles, pumping blood out of heart chambers
Define diastole
Relaxation of heart muscles, filling chambers with blood
State the steps of the cardiac cycle
1) Atria and ventricles are in diastole shortly as they receive blood from body/lungs through veins
2) Atrial Systole: both atria contract to force blood into ventricles, and atrioventricular valves snap shut
3) Ventricular Systole: both ventricles contract to force blood into arteries while atria refill, and semilunar valves snap shut
Define cardiac output and state formula
Volume of blood pumped by one ventricle, per minute
Output = stroke volume × heart rate
(stroke volume = volume forced from a ventricle per contraction)
What is pulmonary circulation and its main pump
Takes deoxygenated blood from right ventricle to lungs, and returns oxygenated blood to left atrium
Pump: right ventricle
What is systematic circulation and its main pump
Takes deoxygenated blood from body to right atrium, and sends oxygenated blood to body
Pump: left ventricle
What are antigens?
Sugars (A and B) on the surface of a person’s erythrocytes
Ability to make antigens are determined by DNA
What are antibodies?
Proteins formed by the immune system that neutralise foreign substances (such as unfamiliar blood types)
Anti-A and Anti-B
Describe blood group A
(antigens, antibodies, can donate/receive)
Antigens: A
Antibodies: Anti-B
Can donate to: A, AB
Can receive from: A, O
Describe blood group B
(antigens, antibodies, can donate/receive)
Antigens: B
Antibodies: Anti-A
Can donate to: B, AB
Can receive from: B, O
Describe blood group AB
(antigens, antibodies, can donate/receive)
Antigens: A and B
Antibodies: None
Can donate to: AB
Can receive from: A, B, AB, O
Describe blood group O
(antigens, antibodies, can donate/receive)
Antigens: Neither A nor B
Antibodies: Both Anti-A and Anti-B
Can donate to: A, B, AB, O
Can receive from: O
