the heart and the circulatory system

Characteristics of a good transport system

Liquid to carry dissolved nutrients, gases and waste products

Pump to push the fluid around the body vid mass flow

Many exchange surfaces to supply tissues with o2 and glucose for respiration

A method ensuring blood reaches all parts of body

Method for oxygenating the blood

Open circulatory system

These are found in animals with an exoskeleton, including insects

Blood is not contained in vessels but is free to move through the body cavity

Blood covers and bathes the body tissues so no need for capillaries as exchange surfaces

Blood is moved either by body movements or by a pumping organ where blood enters the end of this organ through OSTIA and is pumped toward the head where it is released into the body cavity

Larger insects have open tubes that direct blood to metabolically active parts of the body (muscles in wings and legs)

Disadvantages to open circulatory system

Slow movement of blood and low blood pressure

Body movements may impact on circulation of blood

Closed circulatory system

Movements of the heart are independent of body movements so transport is unaffected

Blood is under high pressure so moved more rapidly

Quicker delivery of oxygen and nutrients and similarly quicker removal or carbon dioxide and wastes

Single closed circulatory system

Found in fish, where the blood flows once through the heart for every circuit in the body

Double closed circulatory systems

Found in mammals where blood flows twice through the heart for every circuit of the body

Components of single circulatory system

Blood pressure drops when blood moves through gills

Blood moves slowly towards the body tissues

Supply of oxygen and nutrients and removal of waste has a limited rater

Most fish do not maintain body temperature and so need less energy

Components of double circulatory system

Lower blood pressure in pulmonary circulation so that capillaries in lungs are not damaged

High blood pressure in systemic circulation, so blood moves to the respiring tissues more rapidly

Supply of oxygen and nutrients, and removal of waste can be much faster

Mammals maintain body temperature and so require a lot of energy from respiration

How much does the heart weigh

300g

Where is the heart located

In the middle of the thorax, lower border points to the left of the thorax

How many types of tissue in the heart

3

Outer epicardium tissue

Flattened epithelial cells and supporting connective tissue

Myocardium tissue

Very thick, muscular made up of cardiac muscle

Inner endocardium tissue

Flattened epithelial cells supported by delicate layer of connective tissue, made up of branching cells (1 or 2 nuclei)

How does blood return back to the heart

Via veins to right atrium vis coronary sinus

Atria

Receives blood from veins contract and push blood into ventricles

Ventricles

Severe force of contraction - pumps blood to arteries

Greater force - thicker myocardia in ventricles

Myocardia

Type of muscle in heart

Left ventricle

Myocardia thicker than on right hand side - pumps blood to aorta and round body

Higher pressure than right ventricles which pump blood to lungs

What prevents valves from opening upwards

They are attached by small muscles projecting from walls

What do you call the small muscles projecting from walls preventing valves from inverting

Chordae tendineae

Where are atrioventricular valves located

At atrioventricular orifices between atria and ventricles

When do valves prevent the back flow of blood

When ventricles contract makes sure that blood moves to aorta and pulmonary arteries

Where are semilunar located

Aorta and pulmonary artery

What do semilunar valves do

Prevent blood moving back into ventricles during diastole

What makes heart sounds

Av valves - Lubb

Semilunar valves - Dup

Arteries

Transport blood from the heart

smooth inner endothelial lining so theres less resistance to blood flow

Thick layer of smooth muscle to dilate and constrict blood vessels

Lots of collagen fibres - strength and support

Elastic fibres - stretch and recoil

Small lumen to maintain high blood pressure

Inner tunica intima layer

Flattened epithelial cells and supporting connective tissue

Middle tunica media

Smooth muscle cells and elastic fibres

Outer tunica adventitia

Connective tissue

Arterioles

Arterial vessels with diameter <0.3 mm

Divide rapidly and become smaller - eventually capillaries b

Capillaries

Walls made up of single layers of flattened epithelial cells allowing efficient exchange

Usually 7um in diameter - same as red blood cells

Originates from arterioles which then drain into venules

Narrow lumen

Thin endothelium - one cell thick short diffusion pathway

Veins

Vessels that return blood to heart

Same structure as walls or arteries but larger lumens

Some contain valves - mostly in limbs

Large lumen

Thinner layer of muscle and elastic fibres

Reduced collagen fibres

Walls of capillaries

Selectively permeable membrane

What is tissue fluid formed by

Ultrafiltration

What does tissue fluid contain

water, glucose and amino acids, fatty acids, glycerol mineral salts, dissolved gases and vitamins

What does high pressure cause in tissue fluid

causes movement of tissue fluid into lymph vessel

What does low pressure cause in tissue fluid

Allows movement of lymph back into venous end of capillaries

If water is not reabsorbed in tissue fluid where does it go

Drains into blind-ended lymphatics capillaries

What happens as pressure decreases during circulation

1. BP dramatically drop

2. Systolic pressure and diastolic pressure become the same in the arterioles

Why can arteries maintain the systolic and diastolic pressure unlike veins

Due to its elastic recoil

Systole

Contraction of the cardiac muscle

Diastole

Relaxation of the cardiac muscle

When is thromboplastin released

When damage of the blood vessel is detected

what activated thromboplastin

When platelets come in contact with the wound and change shape

What converts prothrombin into thrombin

thromboplastin

what converts soluble fibrinogen into insoluble fibrin

thrombin

Atherosclerosis

a process where the arteries become fully or partially blocked

What causes atherosclerosis

fat deposits or blood clot

What can atherosclerosis cause

heart attack or stroke in the brain

Cell/tissue death in legs

Could lead to an aneurysm

Biological name for a heart attack

myocardial infarction

How does atherosclerosis cause an aneurysm

increased pressure at a blockage bursts the artery wall leading to the blockage

Does atherosclerosis effects veins

No

Atherosclerosis definition

damage to the inner lining of the arteries which can be magnified by high blood pressure

Angina

chest pain that extends down left arm or up neck

Heart attack

Lack of blood means muscle becomes ischaemic

This can cause death of heart muscle caused by clot in coronary artery

ischarmic

Dosent have any oxygenated blood

Heart failure

main artery becomes blocked, preventing any heart function

stroke definition

death of part of the brain tissue

things that can cause a stroke

mini stroke where bloody supply is briefly interrupted

Blood clot becoming dislodged from a larger artery hence blocking a smaller one in the brain

Bursting of an artery in the brain (brain haemorrhage)

How can the aorta reduce its lumen diameter

Due to it having elastic fibres is allows the aorta to stretch under pressure and then recoil

The recoil shrinks the lumen

Atrioventricular valves

Mitral or tricuspid/bicuspid

They separate atria from ventricles

Semilunar valves

Pulmonary/aortic

Separate arteries from ventricles

Tendinous chords

Valve tendons

Prevent atrioventricular valves turning inside out due to pressure

Septum

Muscle and connective tissue

Prevents oxygenated/ deoxygenated blood mixing

Coronary arteries

Wrapped around the heart to supply blood to cardiac muscle

Symptoms of a stroke

Numbness/weakness in face, arm or leg (one side of body)

Confusion and problems speaking and understanding

Difficulty with vision

Dizziness, loss of balance and coordination

Migraine-type headache and no obvious cause

First signs of cardiovascular disease

High blood pressure and hypertension from narrowing of the lumens of the arteries

This causes the heart to pump harder raising the blood pressure

This can be magnified by arteriosclerosis which means that arteries cannot dilate and recoil easily

Other signs of cardiovascular disease

Difficulty exercising and shortness of breath after moderate activity

Can indicate atherosclerosis in the coronary arteries leading to underperformance of the cardiac muscle

Symptoms of angina

Severe pain in chest during exercise

Symptoms of heart attack

Disabling pains in chest and arm

Onset can be slow - similar symptoms to indigestion

What are 3 stages of the cardiac cycle

Atrial systole

Ventricular systole

Cardiac diastole

Atrial systole

During atrial systole the atria contract forcing the atrioventricular valves open and blood flows into the ventricles

Ventricular systole

Contraction of the ventricles causes the atrioventricular valves to close and semilunar valves to open thus allowing blood to leave the left ventricle through the aorta and right ventricle through the pulmonary artery

Cardiac diastole

Atria and ventricles relax and pressure inside the heart chambers decreases causing semilunar valves and pulmonary arteries close, preventing back flow of blood