6.2 The blood system

components of the blood

1. plasma
2. erythrocytes
3. leucocytes
4. platelets

plasma (d)

liquid portion of blood; contains water, proteins, salts, nutrients, lipids, hormones, and vitamins

Erythrocytes (d)

red blood cells
transport oxygen

3 main types of blood vessels

1. arteries
2. veins
3. capillaries

tissue layers of the walls of blood vessels (3)

1. tunica externa- outer layer
2. tunica media - muscle/elastin layer
3. tunica intima-endothelium

structure of the tunica media(2)

1. a layer of circumferential smooth muscle and variable amounts of connective tissue
2. as second layer of elastic fibers(the external elastic lamina) is located beneath the smooth muscle.

Function of arteries (2)

1. carry blood away from the heart.
2. transports blood at high pressure away from the ventricles to the body tissues.

function of veins (2)

1. carry blood toward the heart
2. transports blood at low pressure

Capillaries (d) (2)

1. very small vessels that can penetrate into body tissues
2. blood moves slowly through them under low pressure providing opportunities for the exchange of substances.

structure of arteries with respect to function (3)

1. relatively small lumen to maintain high blood pressure
2. thick muscular wall and fibrous outer layer of collagen helps it to withstand high bp
3. arterial wall contains an inner layer of muscle and elastic fibers to help maintain pulse flow

3 main types of arteries

1. elastic arteries
2. muscular arteries
3. arterioles

elastic arteries (d)

1. arteries that receive blood directly from the heart
2. need to be elastic because: They are relatively thin compared to their diameter.
3. When the heart contracts, and ejects blood into these arteries, the walls need to stretch to accommodate the blood surge, storing energy.
4. Between heart contractions, the elastic walls recoil, to maintain blood pressure, continuing to move blood even when ventricles are relaxed.

tunica media of elastic arteries

broad and elastic with concentric fenestrated sheets of elastin, and collagen and only relatively few smooth muscle fibers

muscular arteries (d) (2)

1. distribute blood to various parts of the body
2. The walls of these arteries have lots of smooth muscle, which means that they are able to contract or relax (dilate) to change the amount of blood delivered, as needed.

tunica media of muscular arteries (2)

1. well defined layer of smooth muscle
2. elastin sheet is reduced

Arterioles (3)

1 small arteries that deliver blood to the capillaries
2. controls blood flow by contracting and dilating the size of its lumen
3. tunica media contains concentric rings of circular muscle to do this.

elastic recoil (d) (2)

1. refers to the inherent resistance of a tissue to changes in shape, and the tendency of the tissue to revert to its original shape once deformed.

2. With each heartbeat, blood is forced into the arteries causing them to dilate (expand). Then the arteries contract (recoil) as the blood moves further along in the circulatory system.

pulse (d)

alternate expansion and recoil of an artery

how do smooth and elastin fibres maintain blood pressure between pump cycles? (2)

1. systolic pressure
>store potential energy in elastin due to high pressure
2.diastolic pressure
>elastin fibers squeezes the blood in the lumen when the pressure in lumen fall at the end of a heart beat.

blood pressure (d)

The force that blood exerts on the walls of vessels through which it flows

vasoconstriction (d)

decreases blood flow as the smooth muscle in the walls of the tunica media contracts, making the lumen narrower and increasing blood pressure.

Vasolidation (d)

increases blood flow as the smooth muscle relaxes, allowing the lumen to widen and blood pressure to drop

what are the vascular nerves that control vasoconstriction and vasodilation?

nervi vasorum

what are the 2 tissues that capillaries do not supply blood to?

cornea and lens

how does the structure of the veins correspond to its function 3
(3)

1. relatively thinner tunica media with fewer smooth/elastin fibres
2. much larger lumen
3. has valves to prevent backflow of blood

describe the flow of blood in arteries in comparison to veins (2)

1. blood flow in arteries is
pulsatile
2. blood flow in veins is non-pulsatile

what mechanism is used to increase the pressure within the veins?

skeletal muscle pump mechanism

skeletal muscle pump mechanism
(D)

contraction of the surrounding skeletal muscle increases the pressure of the blood flowing within veins

what is the function of valves in veins?

ensuring unidirectional blood flow

how do venous valves and skeletal muscles regulate blood flow in the veins (4)

1. valves in veins are bicuspid, have 2 flap like structures that regulate blood flow. these are called pocket valves as they can catch blood
2. when the skeletal muscles contract blood is pushed toward the heart
3. the valves are open so blood can circulate
4. when the skeletal muscle is at rest the valves close.

specialized structure of capillaries to conduct material exchange

1. very small diameter which allows the passage of only a single RBC at a time to ensure optimal exchange.
2. wall is made of a single layer of cells to minimize the path of diffusion.
3. surrounded by a basement membrane permeable to necessary materials
4. may contain pores

types of capillaries based on structure and function(3)

1. Continuous
2. Fenestrated
3. Sinusoidal

continuous capillaries

Capillary wall is continuous and endothelium is held together by tight junctions

fenestrated capillaries

Capillary wall contains pores

sinusoidal capillaries

have large gaps between adjacent endothelial cells

comparison of the structure of veins, capillaries and arteries (diagram)

double circulation

A type of blood circulation system in which the blood flows through the heart twice. In this type of circulation, the pulmonary circulation is separate from the systemic circulation.

how are materials exchanged in capillaries, explain with reference to blood pressure. (5)

1. blood flows through capillaries at very low pressure to maximize material exchange
2. high blood pressure in arteries is dissipated by extensive branching of vessels and narrowing of lumen
3.atreriole end has higher hydrostatic pressure
4.forces material from the blood stream into the tissue fluid
5. venule end has lower hydrostatic pressure, allows materials from the tissues to enter the bloodstream.

anatomy of the heart

why is the contraction of the heart myogenic?

the signal for a cardiac compression is initiated by cardiomyocytes rather than from brain signals

name for heart muscle cells

cardiomyocytes

sinoatrial node (3)

1. cluster of specialized cardiomyocytes in the wall of the right atrium
2. directs the contraction of the heart muscle tissue
3. acts as the primary pacemaker

Secondary pacemaker of the heart

atrioventricular (AV) node

tertiary pacemaker of the heart

bundle of his

fibrillation

uncontrolled quivering or twitching of the heart muscle caused by the interference of pacemakers

sinus rhythm

the normal (optimal) heart rhythm arising from the sinoatrial node

Role of the pacemaker

Sends electrical signals to keep the pattern of the contraction and relaxation.

what are the steps of the electrical conduction of a heart beat? (6)

1. SA node sends out electrical impulse
2. impulse causes atria to contract
3. impulse stimulates the AV node
4. AV node sends a signal down the septum via a nerve bundle(bundle of his)
5. bundle of His innervates nerve fibres (purkinjie fibers) in the ventricular wall
6. innervation of purkinjie fibres causes ventricular contraction

external signals that can regulate the heart rate?(4)

1. nerve signals, trigger rapid changes
2. endocrine signals, trigger more sustained changes
3. changes to blood pressure levels
4. changes to blood pH

which part of the brain is the pacemaker connected to?

medulla oblongata

how does an impulse from the sympathetic nerve affect the heart rate?

1. releases the neurotransmitter noradrenaline
2. increases heart rate

another name for noradrenaline

norepiphrine

how does an impulse from the parasympathetic nerve affect the heart rate?

1. releases the neurotransmitter acetylcholine
2. decreases heart rate

Hormones

chemical messengers that are manufactured by the endocrine glands, travel through the bloodstream, and affect other tissues

another name for adrenaline

epinephrine

what affect does adrenaline have on the heart rate?

1. increases heart rate
2. activates the same chemical pathways as noradrenaline

Where is adrenaline produced?

adrenal glands above kidneys

cardiac cycle

the series of events that take place in the heart over the duration of a single heart beat

Systole

contraction

Diastole

Relaxation /dilation

what are the 3 main events of the cardiac cycle?

atrial systole
ventricular systole
diastole

what happens during atrial systole?

1. atria contract
2. blood flows from atria to ventricles
3.AV valve is open, semiluna valves closed

what happens during ventricular systole?

1.ventricle contracts
2. blood flows from ventricle to aorta
3. semiluna valves open, AV valves closed

what happen during caridac diastole?

1. atria and ventricles relax
2. blood flows into atrium and ventricle
3.AV valve open, semi luna valves close

lub sound

AV valves closing

dub sound

semilunar valves closing

systolic pressure

Blood pressure in the arteries during contraction of the ventricles.

diastolic pressure

Blood pressure that remains between heart contractions.

blood pressure is measured in which blood vessel?

arteries

normal blood pressure of a healthy adult?

120/80 mmHg

electrocardiogram

record of the electrical activity of the heart

what are the different regions of an electrocardiograph and what do they represent?

P wave
>atrial contraction
>depolarization of the atria in respince to the signalling from the SA node

QRS complex
>ventricular contraction
>depolarization of ventricles due to signal from AV node

T wave
>repolarization of ventricles
>ventricular relaxation

arrhythmia

Abnormal heart rhythm

Bradycardia

slow heart rate

tachcardia

fast heart rate

atrial fibrillation

rapid, random, ineffective contractions of the atrium

ventricular fibrillation

the rapid, irregular, and useless contractions of the ventricles

occlusion

blockage

coronary arteries

supply oxygen-rich blood to the myocardium

Artherosclerosis

Hardening and narrowing of the arteries due to buildup of cholesterol plaques

atherosclerotic plaque

The cholesterol-rich material that is deposited in the arteries of individuals with atherosclerosis.

How does coronary occlusion occur via atherosclerosis?(steps)

1. atheromas develop in the artery
2. reduce the diameter of the lumen
3. restricted blood flow increases pressure in the artery
4. damage to the internal wall due to stress
5.damaged region is repaired with fibrous tissue
6.reduces elasticity of the wall
7. lesions form as the smooth lining of the artery degrades
8.if the lesions rupture blood clotting is triggered forming a thrombus that restricts blood flow
9.if thrombus dislodges it can cause blockage in a smaller arteriole

artheroma

fatty deposit within the wall of an artery

embolus

A clot that breaks lose and travels through the bloodstream.

consequences of coronary occlusion?

- can lead to blood clots that cause heart attack or stroke

risk factors for coronary heart disease

age, genetics, obesity, diseases(eh.diabetes), diet, exercise, sex, smoking

why are males more susceptible to coronary heart disease

as they have lower oestrogen levels

why does smoking a risk facto for heart disease?

Nicotine causes vasoconstriction, raising blood pressure

What does the cardiovascular centre in the medulla oblongata of the brain monitor?

blood pressure, blood pH and carbon dioxide concentration