Biology 103 - Main points/Questions

1. Remember the heart?

2. What tissue lines your vessels?

3. How do plants circulate fluids?

This side of the heart gets blood from the

and ships it to the

.

This side of the heart gets blood from the and ships it to the

.

Arteries• Blood leaving the heart

• Deal with high pressure

• Very little exchange with surrounding tissue

Capillaries• Lower pressure

• Major location of exchange

• Very “leaky”

Three kinds of capillaries:1 – continuous2 – fenestrated3 – sinusoids (most leaky)

.Veins• Return blood to the heart

• Lowest pressure

Fig. 29.7

Low pressure in veins means:

• Valves

• “muscle assist”

Why does exchange happen in capillaries?

Speed of blood in capillaries is much lower

• Like a wide spot in a river…

Capillary bed leaks fluid into interstitial fluid

• This “stirs” the interstitial fluid

• Makes diffusion even more efficient

• But more fluid leaves than returns…

Fig. 29.9

What type of tissue?

Tissue of the Day - Epithelial

• Has one surface open to space

• Other side is attached to connective tissue

• Build linings and membranes of your body

– Line blood vessels

– Line mouth

– Outer layer of skin

Tissue of the Day - Epithelial

Named based on 2 properties

How many layers

• 1layer = simple, multiple layers = stratified

Type of cells

Several types of epithelial tissue are found including thin flattened cells good for diffusion and thicker cells specialized for secreting or absorbing.

Cuboidal • Look like cubes

Tab. 28.2

Squamous• Look like pancakes

Columnar • Taller than they are wide

Tissue of the Day - Epithelial

Named based on 2 properties

How many layers

• 1layer = simple, multiple layers = stratified

Type of cells

Squamous, cuboidal, columnar

Capillaries• Lined with simple

squamous epithelial

• Near all your body cells

• Can be opened and closed

Fig. 29.3.a

Fig. 29.3.b

Your circulatory system keeps all your cells constantly supplied with nutrients

But what happens in plants? (remember they don’t have muscle)

Plants must move water to leaves and sugars to roots! How do they do this? Lets look at a plant…

Do you think this section is through a root or a shoot?

The next slide is a blow up of this region!}

}

Notice this ring of

cells – endodermis!

What type of cells do

you think these are?

These are sugar

transporting cells!

Circulation in Plants• Plants have two systems for moving fluids

– Phloem for sugar transport

– Xylem – 2 cell types (?)

Figure 23.6 Comparison of vessel elements and tracheids

Circulation in Plants• Plants have two systems for moving fluids

– Xylem – 2 cell types (?)

– Phloem for sugar transport

• These systems work in very different ways

– Xylem transports using negative pressure

– Phloem transports using positive pressure

– First look at xylem

Xylem function

• Xylem cells form a continuous tube

– Stretches from root to leaf

– Water attractions keep water from falling

• Power for xylem sap movement

– Driven by evaporation from leaf pours

– Ultimately energy comes from heat/sunlight

Watch water transport video…

http://www.dnatube.com/video/1873/Cohesion-Transport

1 Water evaporates through pores of leaves

water molecules

2 Cohesion of watermolecules to oneanother and adhesionto xylem wall byhydrogen bondscreates a "water chain."

heartwood(xylem)

sapwood(xylem)

vascularcambium

bark

secondaryphloem

cork and corkcambium

3 Water enters thevascular cylinderof root.

flow

of w

ate

r

Phloem cells • Two main types - both alive at maturity

– Sieve tube element - lack a nucleus

– Companion cells provide for both cells

Figure 23.7 Sieve tubes & Companion cells

Phloem cells • Two main types - both alive at maturity

– Sieve tube element - lack a nucleus

– Companion cells provide for both cells

• Transports sugar

– Moves under high pressure

– Moves from source to sink (direction of movement can change!)

Phloem transport

• To generate pressure

– Actively load sugar (sucrose) into sieve tube cells

– Water “follows” the sugar (osmosis!)

– Sugar is actively unloaded where it is needed

• Transport is from loading (source) to unloading (sink)

– Direction of flow changes

Figure 23.23 How

translocation works

Figure 23.23 How

translocation works

4

3

2

1

1

2

34

Vessel(xylem)

Sieve tube(phloem)

Source cell(leaf) Loading of sugar (source!)

Uptake of water

Sap Flow…

Unloading of sugar (sink!)

Sink cell(storageroot)

Sucrose

H2O

H2O

Bu

lk f

low

by

ne

ga

tiv

e p

res

su

re

H2O

Sucrose

Bu

lk f

low

by

po

sit

ive

pre

ss

ure

Sapdroplet

25 µm

Sieve-tubeelement

Stylet Sap droplet

Aphid feeding Stylet in sieve-tubeelement

Separated styletexuding sap

EXPERIMENT

Aphids pierce the

pholoem but don’t cause it

to stop flow…

How can you test contents of phloem?

honeydew droplet

stylet of aphid

• Storage roots

– Store sugar (or starch)

in the fall so phloem

flows towards root in

fall

– These sugars fuel

early spring growth so

in spring flow is from

root to shoot!

Circulation across the kingdoms• Plants and animals push extracellular fluids

– Plants generate flow w/o muscle tissue

– Animals generate flow with pumping muscles

• Fungi move intracellular fluids

– Use cytoplasmic streaming - Proteins inside the

cytoplasm (actin mainly) “stir” the cytoplasm moving

nutrients etc. to rapidly growing hyphae.

• Protists use mainly diffusion and streaming