unit 1 assignment 3 dom hughes cv

8/7/2019 Unit 1 Assignment 3 Dom Hughes Cv

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Unit 1 Assignment 3 Dom Hughes

The Cardiovascular system

In this assignment I will be explaining the structure and function of the

cardiovascular system.

Structure of the cardiovascular system

They include 2 main headings:

y Heart

y Blood vessels

The heart

The heart is the centre of the cardiovascular system. It is situated in the

left hand side of the chest beneath the sternum. It is a hollow muscular

pump that drives blood into and through the arteries in order to deliver

it to the tissues and working muscles.

The heart is surrounded by a twin layered sac known as the pericardium.

The cavity between the layers is filled with pericardial fluid, whose

purpose is to prevent friction as the heart beats. The heart wall itself is

made up of three layers: The epicedium (the outer layer), myocardium

(the strong middle layer that forms most of the heart wall) and the



endocardium (the inner layer). The right side of the heart is separated

from the left by a solid wall known as the septum. This prevents th e

blood on the right side coming into contact with the blood on the left

side. The heart can be thought of as two pumps. They include the two

chambers on the right and the left. The chambers on the right supplyblood and this is where gaseous exchange take s place. This blood is the

returned to the left hand side of the heart via the capillaries, venules

and veins.

There are many different parts in the heart that all have certain jobs to

keep the blood pumping.

Aorta

This is located is the upper chamber of the heart and they receive blood

returning to your heart from either the body or the lungs. The right

atrium receives deoxygenated blood and the left oxygenated blood.

Ventricles

These are the pumping chambers of the heart and have thicker walls

than the atria. The right ventricle pumps blood to the pulmonary

circulation for the lungs and the left ventricle pumps blood for the

circulation for the body.

Bicuspid valve

These are one of the four valves in the heart which are situated between

the left atrium and the left ventricle.

Tricuspid valve

This is situated between the right atrium and the right ventricle and it

allows blood to flow from the right atrium to the right ventricle.

Aortic valve

This is between the left ventricle and the aorta which prevents backflow.

Pulmonary valve

This is between the right ventricle and the pulmonary artery which also

prevents backflow from the pulmonary artery.

Aorta

This is the bodys main artery and it originates in the left ventricle and

carries oxygenated blood to all parts of the body.

Superior vena cava

This is a vein that receives deoxygenated blood from the upper body.



Inf erior vena cava

This vein receives deoxygenated blood from the lower body.

Pulmonary vein

This carries oxygenated blood from the lungs to the left atrium.

Pulmonary artery This carries deoxygenated blood from the heart back to the lungs. It is

the only artery that carries deoxygenated blood.

Blood vessels

This is where the blood flows around the body in a complex network of

vessels.

There are 4 types of blood vessels:

y Arteries

y Arterioles

y Capillaries

y Veins

Arteries

They carry blood away from the heart and they also carry oxygenated

blood. They have two major properties elastically and contractility. They

have thick muscular wall to carry blood at high speeds under pressure.

The arteries can expand to accommodate the extra blood. The smooth

muscle surrounding the arteries enables their diameter to be decreased

and increased as required. This contractility of the arteries helps to

maintain blood pressure in relation to changes in blood flow. They are

largely deep and branch into smaller arterioles that ultimately deliver

blood to the capillaries.



Arterioles

They have thinner walls than arteries. They control blood distribution

.This mechanism facilitates adjustment of blood flow to the capillaries.

They are required during exercise to increase the amount of blood flow

in order to get extra oxygen. Other areas like the gut have their

temporary blood flow so therefore the diameter of their arterioles is

decreased.



Capillaries

These form an extensive network that connects arteries and veins by

uniting arterioles and venules. They are the smallest of the blood

vessels, narrow and thin. They are a essential part of the vascular systemas they allow diffusion of oxygen and nutrients. The walls of the

capillaries are only one cell thick, allowing nutrients, oxygen and waste

products. The pressure of blood within the capillaries is higher than that

in veins.

Veins

This is the return of the deoxygenated blood to the heart. They have

thinner walls than arteries and have a large diameter. Contacting

muscles push the thin walls of the veins inwards to help squeeze the

blood back towards the heart. AS the muscles contract there are a

number of pockets in the veins that assist in preventing any backflow

when the muscles relax. They branch into smaller vessels called venules,

which extend to the capillary network.



Functions of the cardiovascular system

There are many important factors that help the function of thecardiovascular system.

Thermoregulation

This is when increased energy expenditure during exercise requires

adjustments in blood flow that affect the cardiovascular system. This

system is responsible for the distribution and redistribution of heat

within your body to maintain thermal balance.

Vasodilation

During movement the cardiovascular systems active muscles increase

through dilation of arterioles. Vasodilation causes an increase in the

diameter of blood vessels to decrease resistance to the flow of blood to

the area supplied by the vessels.

Vasoconstriction

Sometimes blood vessels can also temporarily shut down blood flow to

tissues. It also causes a decrease in the diameter of blood vessels. Once



contraction of involuntary muscles fibres occur the walls of the blood

vessel increase resistance to blood flow.

Function of blood

The function of the blood is to provide the fluid environment for cells

and is the medium by which many materials are carried to and fromthese cells. Blood has four principle constituents; they include plasma,

red blood cells, white blood cells of which there are different types, and

platelets or cell fragments.

There are many functions for the blood. They include distribution,

regulation and protection. The blood helps to maintain the bodys

temperature by absorbing and distributing heat. Nutrients are

transported from the intestines to the liver and body cells, and waste

products from the tissues. Also protective white blood cells, antibodies,

hormones and medicines are also transported in the blood.

Oxygen transport

Exercise increases the demand for more oxygen. The blood gets

transported from the lungs to the parts of the body that require it the

most.

Clotting

This is a complex process during which white blood cells form solid clots.

If a blood vessel is damaged the wall is covered by a fibrin clot to assist

repair of the damage. Platelets form a plug at the site of damage. This is

made possible by the constant supply of blood through the

cardiovascular system.

Fighting inf ection

In blood it contains antibodies and white blood cells which help defend

against viruses and bacteria.

unit 1 assignment 3 dom hughes cv

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