Transport system in animals

Question 1

Why do organisms use a mass flow system?

Answer 1

• SA:V too small to meet demand and remove waste at a suitable rate
  -Diffusion distance is also too large
  -Mass flow takes substances and nutrients closer to the cells
  -more quickly

Question 2

Define closed circulatory system. Advantages?

Answer 2

Blood always moves within blood vessels

-High pressure can be maintained
-Different blood pressure’s in P&S systems
-Blood supply can vary between organs to meet demand
-Lower volume of blood required compared to open system

Question 3

Define double circulatory system. Advantages?

Answer 3

A system where blood passes through the heart twice per complete circuit around the body

-High pressure can be maintained
-Oxygenated and deoxygenated blood do not mix
-Increases efficiency in delivering O2 and glc
-BP in PC and SC can be maintained at different levels

Question 4

Structure of blood vessels

Answer 4

Elastic fibres- contain elastin which allow for stretch and recoil
Smooth muscle- contracts or relaxes which changes site of the lumen
Collagen- provides structural support
Endothelium- single layer of cells with smooth inner surface to reduce friction and resistance

Question 5

Arteries

Answer 5

-Oxygenated blood away from heart at high BP
-Walls contain elastic fibres, smooth muscle and collagen
-Elastic fibres enable them to withstand force of blood and stretch to allow larger blood uptake
-Also recoils between contracts to give a continuous flow

Question 6

Arterioles

Answer 6

-Less high BP
-Link arteries to the capillaries
-More smooth muscles and less elastic in their walls compared to arteries (little pulse surge)
-Regulates flow and distribution by vasoconstriction and vasodilation

Question 7

Capillaries

Answer 7

-Very narrow lumen - RBC pass in single file
-Connect arterioles to venules
-Exchange of substances between cells and blood
-Fenestrations between endothelial cells
-Low BP, no pulse

Question 8

How are capillaries adapted for their role?

Answer 8

-very large SA for diffusion
-Short diffusion distance (single endothelial cell thick)
-Total cross-sectional area larger than arteriole supplying blood, so rate of blood flow falls- more time for exchange of substances

Question 9

Venules

Answer 9

-Thin, some smooth muscle, some elastic fibres
-Receives deoxygenated blood from the capillaries
-low BP, no pulse

Question 10

Veins

Answer 10

-wide lumen, lots of collagen, little elastic fibres, endothelium
-Carry deoxygenated blood to the heart via inferior and superior vena cava
-contain valves to prevent backflow of blood
-Low BP
-No pulse

Question 11

How do veins overcome their low blood pressure?

Answer 11

-Valves close when blood starts to flow backwards
-Contraction of skeletal muscles- increases BP, squeeze veins and forces blood towards heart

Question 12

Systematic circulation diagrams. Oscillations

Answer 12

Arteries:
BP is high due to ventricular systole, surge in pressure
During ventricle diastole, pressure drops momentarily
This is what causes oscillations
Oscillations lessen as blood passes through arteries
(walls expand during when P is H, recoil when L)

Arterioles:
BP falls as it travels through arteries
Blood is more in contact w vessel walls, so BP falls due to increased friction

Capillaries:
Cross sectional area is vast- drop in BP
Increased friction

Venules and Veins:
BP continues to drop to its lowest point as it is the furthest from the heart

Question 13

Pulmonary Circulation. Small oscillation at the beginning

Answer 13

Arterioles:
BP rises as blood flows into the heart and into pulmonary artery
Pressure cause by contraction of LV
Lower pressure as blood has to travels a shorter distance
Oscillations due to heartbeat

Rest: blood pressure continues to drop

Question 14

Measuring blood pressure

Answer 14

Using a sphygmomanometer
units Kpa
Average 120/80 mmHg

Question 15

Hypertension

Answer 15

-persistently high BP

Stage 1: clinic 140/90, home 135/85
Stage 2: clinic 160/90, home 150/95
severe: clinic systolic <180, clinic diastolic <110

risk factors: obesity, smoking, alcoholism, high stress, age

(patient may have white coat syndrome)

Damage to endothelium cells-> aneurysm (rupture of artery wall) or blood clot
Damage to valves
Kidney disease as capillaries in glomerulus are damaged

Question 16

Hypotension

Answer 16

-persistently low BP

symptoms: weakness, tiredness, dizziness, coma

Question 17

Composition of tissue fluid?

Answer 17

-Plasma which has escaped through fenestrations
-Oxygen, water, mineral ions, some WBC (e.g. macrophages)
Does NOT contain large plasma proteins nor RBC

(carbon dioxide and waste products are carried away by TF)

Question 18

Ultrafiltration

Answer 18

-Near arteriole end, higher hydrostatic pressure inside capillaries than in TF
-So, this forces plasma fluid out of the capillaries through fenestrations
-As fluid leaves capillaries, hydrostatic pressure inside them decrease

Question 19

Reabsorption

Answer 19

-At the venous end of the capillaries, hydrostatic pressure inside capillaries is lower than in the TF
-The reduction of fluid raises oncotic pressure (due to plasma proteins in plasma- lower WP inside capillaries)
-So, water re-enters capillaries by osmosis

Question 20

Measuring blood pressure using sphygmomanometer

Answer 20

-BP usually taken on left arm
-Cuff attached to upper arm and is inflated
-Builds up pressure on brachial artery and eventually stops blood flow
-using stethoscope, doctor places it under cuff and listens for sounds of blood flow returning as cuff deflates

Start of sound (Krokoff sounds) = systole pressure
Absence of sound= diastole pressure

Question 21

what is the function of tissue fluid

Answer 21

to deliver nutrients to cells and remove waste products

exchange of material at capillaries