Download Lecture 8

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 – continuous
2 – fenestrated
3 – 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.
Tab. 28.2
Columnar
Squamous
•• Taller
thanpancakes
they are wide
Look like
Cuboidal
• Look like cubes
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/Co
hesion-Transport
1
Water evaporates
through pores
of leaves
water molecules
2
Cohesion of water
molecules to one
another and adhesion
to xylem wall by
hydrogen bonds
creates a "water chain."
heartwood
(xylem)
sapwood
(xylem)
vascular
cambium
bark
secondary
phloem
cork and cork
cambium
flow of water
3
Water enters the
vascular cylinder
of root.
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
Vessel
(xylem)
Sieve tube Source cell
(phloem) (leaf)
H2O
1
Loading of sugar (source!)
Sucrose
1
2
H2O
Uptake of water
Bulk flow by negative pressure
Bulk flow by positive pressure
2
3
Sap Flow…
Sink cell
(storage
root)
4
3
4
H2O
Sucrose
Unloading of sugar (sink!)
EXPERIMENT
How can you test
Aphids
25 µm
contents of pierce
phloem?
the
Sievetube
element
Sap
droplet
Aphid feeding
Stylet
pholoem but
don’t cause it
to stop
flow…
Sap droplet
Stylet in sieve-tube Separated stylet
element
exuding sap
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