Key area 5- the structure and function of arteries, capillaries, and veins

The cardiovascular system includes:

• The heart is a muscular pump

• The blood is fluid connective tissue

• The blood vessels, arteries, veins, and capillaries

Blood flow from the heart

• blood flows away from the heart in arteries to the capillaries and back to the heart in the veins

• There is a decrease in blood pressure as the blood travels away from the heart

• Arterial branches of the air supply oxygenated blood to all parts of the body

• Deoxygenated blood leaves the organs in veins

• Veins unite to form the Vena cover, which returns blood to the heart

The heart muscle

• The heart muscle has its own blood circulation

• The coronary artery provides the muscle with oxygenated blood

• The coronary vein Returns the auction blood to the circulation

Pulmonary system

• this is the route by which blood is circulated from the heart to the lungs and back

• The pulmonary artery carries the deoxygenated blood, and the pulmonary vein carries oxygenated blood

Structure and function of blood vessels

• The central cavity of a blood vessel is called the lumen

• The luminous line with a thin layer of cells called the endothelium

• The composition of the vessel walls surrounding the endothelium is different in arteries, veins, and capillaries

Artery

• Arteries carry blood away from the heart

• They have an inner and outer layer of connective tissue containing elastic fibers

• Arteries have a thick middle layer. I’ve smooth muscle with more elastic fibers.

• Elastic fibers and nailed the artery to pulsate, stretch and recoil, thereby accommodating the surge of blood after each contraction of the heart

Smooth muscle

• smooth Muscle in the walls of Of the arterioles can contract or become relaxed

• This construction or relaxation brings about vasal, dilation or vasoconstriction to control blood flow

• This allows changing demands of the body’s tissues to be met

Vasodilation

• The circular muscle in the arterioles wall is relaxed and the lumen wider

• This allows an increased blood flow to the Skeletal muscles

Vasoconstriction

• at the same time As vasodilation the arterioles leading to the small intestine undergo vasoconstriction

• Their sickly muscles are contracted, and the lumen is narrower

• As a result, this reduces the blood flow to the gut

Veins

• veins carry blood back into the heart

• The outer muscular layer of connecting tissue containing layers of elastic fibers in the vein wall are thinner than those in an artery because blood flows along a vein at low pressure

• Aluminum vein is wider than that of an artery

• Valves are present in vein to prevent the back flow of blood

Capillaries and exchange of material

• blood is transported from arterioles to venules By passing through dense network of blood vessels called capillaries

• Exchange of substances between blood and living tissue takes place through capillary walls

• Capillary walls are composed of endothelium and are only one cell thick

Plasma and tissue fluid

• plasma is a watery yellow fluid containing dissolved substances, such as glucose, amino acids, blood cells, platelets, and plasma proteins

• Blood arriving at the arterioles and of a capillary bed is at a forced pressure Then blood in the capillaries

• As blood is forced into the narrow capillaries, it undergoes pressure filtration

• Pressure filtration Causes much of the plasma to be squeezed out through the thin capillary walls surrounding cells

• Once the plasma is squeezed out, it is then referred to tissue fluid

Difference between plasma and tissue fluid

The only difference between plasma and fluid is that plasma has proteins

Flow through capillaries

Continent of tissue fluid

• food & oxygen

• these diffuse down a concentration gradient into the surrounding cells

• Carbon dioxide and other metabolism, waste diffuse out of cells and a concentration gradient into the tissue fluid to be excreted

Tissue fluid and lymph

• much of the tissue fluid returns in the blood at the venule End of the capillary bed through osmosis

• Tissue fluid lacks plasma proteins as they were too large to be filtered through the capillary walls

• Some of the tissue fluid does not return to the blood in the capillaries

Lymphatic vessels

• The tissue fluid is absorbed by Thin-walled lymphatic vessels

• Once the tissue fluid reaches the lymphatic vessels, it is called lymph

• Tiny lip vessels, unit to form, larger vessels

• Flow of lymph is brought about by the vessels being compressed when muscles contract during breathing and body movement

• Larger lymph vessels have valves to prevent backflow

• Lymph vessels return their contents to the blood via two lymphatic ducts

• These into the veins coming from the arms

Method of tissue fluid returning to the circulatory system

• tissue fluid returns to the circulatory system through osmosis as tissue fluid lax plasma proteins. It has a higher water concentration than blood plasma so tissue fluid is absorbed by the thin, lymphatic vessels, becoming lymph to then be returned to the circulatory system

Exchange of O2 molecules

• Oxygen diffuses through the capillary wall, into the tissue fluid, and the cells.

Exchange of CO2 molecules

• Carbon dioxide diffuses from the cells into the tissue fluid, then across the capillary walls into the blood plasma.

Exchange of glucose molecules

• Glucose diffuses from the blood plasma, across the capillary walls to the tissue fluid, and then to the cells.

Exchange of urea

• The waste product urea diffuses from the cells of the liver, to the tissue fluid, and then across the capillary walls into the blood plasma.