Biology - B3.2 Transport

Through what vessels does the blood flow from the heart, in order?

Heart —> arteries —> arterioles —> capillaries —> venules —> veins

Function arteries

To carry blood away from the heart, carry blood that is oxygen-rich and at high pressure bc pumped from heart

Adaptations of arteries

• Thick layer of elastic fibres and tough collagen fibres to withstand high pressure and stretch to accomodate increase in volume of blood and reduce fluctuations

• Made of smooth muscles to regulate diameter of artery

• Narrow lumen to maintain high blood pressure and push blood onwards

Where is pulse measured?

In radial (wrists) and carotid (neck) arteries

Surge of blood flow there and feel elastic arteries expanding

Systolic vs diastolic pressure, blood pressure

Systolic is heart contracting, so a higher pressure (measured in vessels)

Diastolic is relaxed heart, so lower than systolic (measured in between beats/pumps)

Function capillaries

Exchange of materials between blood and the internal or external environments

Adaptations capillaries

• Branched and narrow vessels for increase in SA:V ratio and slows flow of blood for more time to exchange

• Very thin walls (1 cell thick) for short diffusion distance = rapid diffusion

• Some are fenestrated (gaps) to allow rapid exchange, usually in organs with high metabolic demands (e.g. kidneys but not b

  rain)

Function veins

Return blood to heart, with no pulse, constant flow and at low pressure

Adaptations veins

• Thin and flexible walls to be compressed by skeletal muscles around to aid flow and push blood along

• Large lumen to avoid resistance

• Valves (flaps of tissue) to prevent backflow of blood

Arteries vs. veins

• Arteries have more elastic fibres and smooth muscles than veins

• Arteries have a smaller/more narrow lumen than veins

• Artieries have blood flowing away from heart whilst veins flow towards

• Arteries carry blood with higher pressure

• Valves are only present in veins

• In arteries the wall thickness is to withstand pressure, so thick whilst veins have thinner

• Pulse is only present in arteries

How does occlusion in the coronary arteries occur?

• build up of plaque/fatty deposits, narowing the arteries

• when heart/coronary arteries become blocked, heart can’t pump

• plaques can rupture/tear, causing platelets to form clot which further narrows artery

Consequences of occlusion in coronary arteries

Myocardial infraction, heart attack bc no oxygen

Lifestyle/bodily causes of occlusions

• Increase in blood pressure

• High cholesterol

• Smoking

• Diabetes

• obesity

• lack of exercise

• Genetics/hereditary

Def. occlusion of coronary arteries

Arteries of the heart blocked

Transpiration

Transport of water in plants from roots to the leaves

How does transpiration occur?

Evaporation in the leaf cells, so water from the adjacent cells move to replace it through a type of capillary action, adhesion and cohesion (apoplastic pathway, through cell walls not cytoplasm)

As water moves up in xylem a tension/transpiration pull is generated which moves water up

Negative pressure in xylem bc tension pulls water up whilst gravity pulls water down

Apoplasic vs symplastic movement

Apoplastic is through cell walls

Symplastic is through cells and their plasma membrane

Adaptations xylem

• Lack of cell contents (non-living when mature) space for water & minerals ions to flow

• Incomplete or absent end walls so more movement form 1 to the other is possible

• Cell walls strengthened with lignin spirals or rings to add rigidity and support to prevent imploding of xylem, bc of negative pressure

• Pits between adjacent vessels, so water can move across and choose path of least resistance

What are dicotyledonous plants?

Kargest of the two groups of flowering plants, broad leaves and two seed “leaves” or cotyledons

NOT monocotyledon

Tissues that are in both monocotyledon and dicotyledonous plants

• Epidermis (outermost layer) for protection

• Xylem for water transport

• Phloem for transport of products for photosynthesis

• Cambium

• Cortex as packing cells

Transverse vs longitudinal section

Transverse is cut accross

Longitudinal is lengthways

Structure of stem, transverse

Xylem and phloem distributed in vascular bundles with a region between the two of undifferentiated cells called the cambium (can divide into both). The phloem is on the outside, bc insects need their food from the phloem.

Epidermis is outside layer, cortex is the space between epidermis and phloem

Structure of root, transverse

Xylem and phloem in the centre, xylem makes cross shape whilst phloem cells in between the arms of the cross.

Ring of cells around cross is endodermis

Cortex cells as the rest of the root with epidermis around it all.

Tissue fluid

The fluid that leaks out of capillaries and baths surrounding cells

Tissue fluid and capillaries

At arteriole side the blood pressure is higher and helps to force the fluid out, called pressure filtration

Most tissue fluid then returns to the capillaries at the venous side of the capillaries bc of the lower blood pressure there

Function lymphatic system

Avoids the tissue fluid accumulating and causing swelling and eventually returns it back into the blood system.

Tissue fluid composition vs plasma composition

• Blood plasma has erythrocytes, white blood cells while tissue fluid has phagocytes

• Blood plasma has more larger proteins

• Glucose is only present in blood plasma because it is too large

• Blood plasma has more amino acids

• There is more O2 in blood plasma

• There is less CO2 in blood plasma

How does lymph system work

Lymph moves because of adjacent arteries and skeletal muscles squeezing against them.

Lymph vessels get tissue fluid at tissue cells, transport it to lymph node where the blood is surveyed, transported through lymph ducts and tissue fluid then rejoins blood

Structure lymphatic vessels and lymph ducts

Lymphatic vessels have tissue cells around them, have very thin and permeable walls, are blind-ending (no end, open system), have valves to ensure 1 direction movement

Lymph ducts are lymph vessels joined together

Difference in structure of double vs single circulation

• Double circulation goes to and from the lungs (pulmonary circulation) and to and from all the other organs in the body (systemic circulation), past heart twice

• Single circulation goes in a loop

Examples of single and double circulation

Single: fish

Double: mammals

Why can fish have single circulation?

They have an aquatic living environment with slightly higher pressure so the water pushes on the fish maintaining the pressure to ‘pump’

Cardiac muscle form-function adaptations

• Striated

• Interlacated discs hold cells together

• Gaps/junctions allow communication

• Can contract without anything else, myogenic

• Branched and multinucleated

Pacemaker form-function adaptations

Sinoatrial node and sinoventricular node

Function: initiate myogenic contractions, regulate myogenic activity, governs the rhythm of the heart

• Spread action potential into atrium and ventricle

Atria form-function adaptations

Atria is the receiving chamber

Receives blood at low pressure, distributes it without generating pressure to ventricle

• Has thin muscular walls

• Empties quickly to receive more

Ventricles form-function adaptations

Distributing chambers

Function: generate pressure to distribute, pump into aorta etc.

• Thick walls with muscles to pump

Atrioventricular and semilunar valves form-function

Function: prevent backflow

Atrioventricular: as lower ventricles contract, blood pushes against them, shutting them

• Valves point in direction of flow

Septum form-function

A complete wall between the two sides of the heart

Function: divides heart from high O2 (LA) from low O2 (RA), and from different pressures

Coronary vessels form-function

Arteries after aorta etc., should withstand high pressures

Function: supply heart muscles with oxygen

Flow of blood in heart

Enters through vena cavas or pulmonary veins,

enter atriums,

enter ventricles,

enter aorta or pulmonary artery

Stages in cardiac cycle

1) Blood enters the atria through veins

2) Atrio-ventricular valves open

3) Blood flows passively into the ventricles

4) SA initiates and communicates

5) atria contract

6) Blood forced into ventricles

7) AV node initiates and communicates

8) Ventricles contract

9) Atrio-ventricular valves close

10) Semilunar valves open

11) Blood forced into the aorta and pulmonary artery

12) Ventricles relax

13) Semilunar valves close

Graphs for pressure in the aorta

1) Atria contracts to move blood into ventricle, increase in pressure slightly

2) Increase in ventricle pressure bc its contracting, ONLY AFTER AV valves close

3) When pressure in ventricle=pressure in aorta, semilunar valves open

4) And SL valve closes again when aorta=ventricle

5) Antriventricular valves open when ventricle=atria, second time

Whats the heart beat, related to valves and pressure

You hear the ‘lub’ ‘dub’ when the valves close

How does water enter roots?

Osmosis, which is artificially created by pumping minerals by active transport into roots, increasing solute concentration

Relating water potential and pressure potential in xylem

Negative pressure potential in xylem bc tension/transpiration pull from leaves and gravity

This lowers xylem water potential increasing water that moves into the xylem

Definition root pressure

The active transport of mineral ions into the xylem vessels

Root pressure and solute potential and water movement

If a plant is not transpiring (e.g. at night) the mineral ions will be pumped into the xylem by active transport, decreasing the solute potential so more water moves in.

Results in positive pressure potential

Two components of phloem tissue

Sieve tubes and companion cells

Description of movement inside phloem and function

Symplastic and multidirectional movement/transport of nutrients

Adaptations sieve tube elements

• Reduced contents for fluid to flow

• Sieve plates with holes to allow unimpeded flow and increase regulation

• Associated with companion cells

Adaptions and functions companion cells

• Carry out most metabolic reactions

• Contain many mitochondria to make ATP to relocate nutrients

• Have many plasmodesmata to connect sieve tubes and companion cells

What’s sap in phloem

The fluid in the phloem, organic solutes like sucrose, amino acids or plant hormones

What are sources and sinks inside plants (sap)

Where organic molecules are being stored is the source

Where they are needed or being transported to is the sink

Def translocation

The transport of organic solutes through a plant from source to sink

Process of translocation

1) Sucrose at the source(leaf) is loaded into the phloem tubes by active transport and ATP

2) Increases solute concentration and water flows into phloem by osmosis, from adjacent xylem

3) High hydrostatic pressure at top (or at source) of phloem

4) Causes flow (mass flow/bulk flow) to area with lower hydrostatic pressure, the sink

5) At sink, sucrose is transported out using active transport

6) Lowers solute concentration and water moces back into the adjacent xylem vessels