biology chapter 8 transport in animals

what type of system are blood vessels a part of?

Blood vessels are part of a closed circulatory system

what are the types of blood vessels?

arteries, arterioles, capillaries, venules, veins

from the heart?

-arteries and arterioles carry oxygenated blood from the heart to body cells

to the heart?

-veins and venules carry deoxygenated blood from the body cells to the heart

name the artery that carries deoxygenated blood

pulmonary artery--> carry deoxygenated blood from the right ventricle to the lungs

arteries lead into....

-arteries lead into arterioles then into capillaries where gas exchange occurs.

from here....

capillaries move into venules then into veins and back to the heart

components of blood vessels

-elastic fibres—> these are made of elastin. They stretch and recoil providing the vessel with flexibility

-smooth muscle—>contacts and relaxes changing the size of the lumen

-collagen—>provides structural support to maintain shape and volume of the vessel

Structure of an artery

narrow lumen, tunica intima, tunica media, tunica externa,

tunica interna (intima)

consists of an endothelium (1 cell thick layer) and some connective tissue

tunica media

The middle and thickest layer of tissue of a blood vessel wall, composed of elastic tissue and smooth muscle cells that allow the vessel to expand or contract in response to changes in blood pressure and tissue demand.

tunica externa (adventitia)

collagen fibers that protect and reinforce vessels

arteries and arterioles carry blood under?

high pressure, the narrow lumen helps to maintain this pressure

what allows vessel to expand and recoil (pulse)

the thick elastic and muscle layers allow the vessel to expand with heart beats and then recoil (pulse)

arterioles have...

little elastic tissue and more smooth muscle which have little pulse surges, they contract and dilate to move blood flow

Capillaries

-the lumen is only one blood cell thick to ensure red blood cells travel through in single file

-substances are exchanged from blood cells to surrounding tissue through gaps in the endothelium

-capillaries have a very large surface area

Adaptations of capillaries

-large surface area—> allow the diffusion of substances in and out of the capillaries

-cross sectional area is small—> to reduce rate of blood flow from the artery supplying them

-endothelium is one cell thick—> provide a short diffusion pathway for diffusion

structure of veins

-large lumen, contains valves

-intima—> consists of an endothelium (1cell thick) and some connective tissue

-media—>consists of a thin layer of elastic tissue and muscle tissue

- externa—> consists of a thick layer of collagen

veins do not have a pulse as...

its blood pressure is low as it is lost as blood moves around the body (despite holding up to 60% of total blood volume)

veins has no..

no elastin fibres or smooth muscle

several venules will split from..

one vein

valves only found in..

medium sized veins

valves act as a..

on-way blood flow system to prevent back flow

large valves

will have active muscles moving blood

breathing movements

in the chest this aids the movement of blood

varicose veins

abnormally swollen, twisted veins with defective valves that allow back flow of blood; most often seen in the legs

Veins structural differences from arteries

- Lumens are larger

-single layer of cells surrounding lumen

- 65% of blood in veins at any given time

- Tunica externa is thicker

- Less elastin in walls

- Walls are thinner than those of comparable arteries

-present valves in lumen

arteries structural differences from veins

-small/narrow lumen

-single layer of cells surrounding lumen

-elastic tissue, smooth muscle and collagen

-thick layers in walls

-absent valves in lumen

Systole

Contraction of the heart

Diastole

Relaxation of the heart

during systole..

blood is pumped through the aorta and other arteries at high pressure. The elastic fibres of arteries enable them to expand and allow blood through.

during diastole

the blood pressure in the arteries drops. The elastic recoil of the artery walls help force the blood on.

what is blood

Blood is a specialised transport medium that is also considered a special type of connective tissue

bloods range of functions

-transport

-defence

-thermoregulation

-maintaining pH of body fluids

components of blood

erythrocytes (RBC), leukocytes (WBC), platelets, plasma

total volume of blood in human body

5dm3

avg number of red blood cells

2.5x10^15

white blood cells?

5x10^11

platelets?

6x10^12

specialised features of an erythrocyte

-flattened, biconcave disc shape —> ensures large surface area to volume ratio for

efficient gas exchange

-large amount of haemoglobin—> for transporting oxygen

-no nucleus or organelles—>maximises space for haemoglobin, so more oxygen can be transported

-diameter (6-8um) larger than capillary diameter: slows blood flow to enable diffusion of oxygen

Erythrocytes structure

Biconcave

Lots of surface area

Short diffusion path for oxygen

Bags of hemoglobin

Lots of binding sites for oxygen

plasma proteins and blood pressure

-About 8% of blood plasma consists of plasma proteins, of which about half may be albumins.

-these are involved in the transport of other substances (e.g. hormones) and help regulate the osmotic pressure of blood.

blood water potential 1

-Substances dissolved in the blood plasma can move in and out of the capillaries

-Some large proteins, such as albumin, have an osmotic effect

-they cause the blood to have a relatively low water potential

blood water potential 2

-as a result water tends to move into the blood from surrounding tissues by osmosis

-this is called oncotic pressure = -3.3kPa

Formation of tissue fluid 1

Pressure inside the blood, caused by the contraction of the heart, is high - called hydrostatic pressure

At the arteriole end of a capillary hydrostatic pressure forces water out the capillaries. Pressure = 4.6kPa

formation of tissue fluid 2

At the venule end of the capillary oncotic pressure is higher than the HP as there is a lower water potential in the blood

Water moves aback into the capillaries

tissue fluid allows the body to

easily and quickly move dissolved molecules onto the bodies cells, and take away waste materials back into the blood

hydrostatic pressure

this high blood pressure inside the capillaries, forcing blood plasma, dissolved solutes and small proteins out of the capillaries, through the endothelium onto the bodies cells (arterial end of the capillaries)

oncotic pressure

the removal of the blood plasma, causes a decrease in the water potential of the blood, as a result water moves back into the capillaries by osmosis (venous end)

not all tissue fluid returns to the..

capillaries, about 10% remains in the tissues. The excess drains into the lymphatic system, where it forms lymph.

lymph is a

colourless/ pale yellow fluid similar to tissue fluid but containing more lipids and WBCs.

the lymphatic system drains into

the circulatory system near the vena cavae via the thoracic duct.

the importance of lymph?

Tissue fluid flows into lymph system through valves. nodes

Without the lymph system you would die within 24 hours, as the rate of water loss in the blood would be too large

This would lead to a build up of tissue fluid in the tissues, this is called • oedema

lymphatic system

lymphatic capillaries and vein-like lymph vessels, containing valves

lymph nodes

sac-like organs that trap pathogens and foreign substances, and contain large numbers of white blood cells

lymphatic tissue

in the spleen, thymus and tonsils - also contain large amounts of white blood cells and are involved in their development.

contents of blood

-erythrocytes

-water

-carbon dioxide

-urea

-inorganic mineral ions (na+/cl-)

-leucocytes