Biology 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.

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 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 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 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 a

Fig 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… 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

3 Water enters the vascular cylinder of root. flow of water

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 How translocation works

Vessel (xylem) Sieve tube (phloem) Source cell (leaf) Loading of sugar (source!) Uptake of water Sap Flow… Unloading of sugar (sink!) Sink cell (storage root) Sucrose H2OH2O H2OH2O Bulk flow by negative pressure H2OH2O Sucrose Bulk flow by positive pressure

Sap droplet 25 µm Sieve- tube element Stylet Sap droplet Aphid feeding Stylet in sieve-tube element Separated stylet exuding 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