Transport Systems

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Chapter 7

• Transport Systems

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Transport

• Small, simple organisms living in water can
  obtain nutrients and eliminate wastes through
  diffusion.
• What about larger, more complex organisms?

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Plant Transport Systems

• The first land plants evolved from green algae
  about 430 million years ago.
• Life on land presented challenges for plants
  loss of moisture to the air, ability to get
  nutrients from soil and air, ways to eliminate
  wastes.
• Plants have specialized structures to cope with
  the challenges.

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Plant Terminology

• Vascular Plants are plants with specialized
  tissues for water and nutrient transport.
• Nonvascular Plants are plants without these
  tissues and must live in damp places.
• Lignin is a hard material embedded in the
  cellulose matrix of cell walls to help support
  large vascular plants.

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Plant Terminology Continued

• Xylem is hollow-tube shaped cells that carry
  water and minerals up from the roots.
• Phloem are elongated cells arranged into tubes
  filled with streaming cytoplasm that moves
  organic materials throughout the plants.

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Water Transport

• Xylem is made up of two types of water conducting
  cells.
• Tracheids which have pitted walls through which
  water moves from cell to cell.
• Vessel Elements are wide thin-walled cells that
  are open on the ends, so water flows freely
  through these.

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• Water loss is especially challenging, plants lose
  water through their stomates, which are open to
  facilitate gas exchange for photosynthesis.
• A red maple growing in a humid climate loses as
  much as 2,000L per day (1000 2L coke bottles).
• Plants must constantly replace this lost water.
• How is the water moved from the roots to the very
  tip of the plant?

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• The current hypothesis is the cohesion-tension
  hypothesis.
• Root pressure, cohesion of the water molecules,
  and adhesion of the water to other charged
  molecules (which are found in the walls of the
  tubular cells) and the transpiration of the water
  leaving the plant essentially tug the water up.

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Plant Nutrient Transport

• In plants, nutrients travel through phloem cells
  that are joined end-to-end. Tiny pores in the
  walls at the ends of the phloem cells allow the
  contents of cells to mix.
• Tiny strainer-like cells called sieve tubes are
  located at the tips of the cells.

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• Sugars and Amino Acids move through the phloem
  cells from the leaves to the other parts of the
  plants.
• The best explanation is that the materials move
  from the source to the sink or from areas of
  high pressure to areas of low pressure.

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Transport Systems in Animals
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Circulatory Systems

• Like plants, animals must also have a way to
  exchange materials between cells and the
  environment.
• Unicellular organisms living in water
  environments can rely on diffusion and active
  transport.
• Larger organisms must have specialized systems.

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• The size of an organism and its activity level
  determine the complexity of the transport system.
• In arthropods, (insects, crabs, etc.) there is an
  open circulatory system. There is no separation
  between the blood and other fluids. These
  organisms may or may not have some type of heart
  to help pump the blood throughout their body
  cavity.

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Open Circulatory System

• In an open system, the blood is in the body
  cavity or hemocoel and is pumped by the hearts.

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Closed Circulatory System

• In a closed system, blood is contained in
  vessels.
• These vessels branch into smaller and smaller
  vessels.
• The heart pumps blood through the system.

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Circulation in Vertebrates

• Humans and other vertebrates have closed
  circulatory systems also called cardiovascular
  systems.
• The components are
• The heart
• Blood Vessels
• Blood

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Circulatory System

• This example shows some of the major vessels of
  the human circulatory system.

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Blood Vessels

• There are 3 types of blood vessels.
• Arteries carry blood AWAY from the heart. In all
  but one artery, this is oxygenated blood.
• Veins carry blood TO the heart. In all but one,
  this is de-oxygenated blood.
• Capillaries are the microscopic vessels that form
  a network in the tissues. These are where gas
  exchange occurs (remember the respiratory system)

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Capillary

• Capillaries make the transition from arteries to
  veins.

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The Heart

• Mammals have a 4-chambered heart and most
  amphibians and reptiles have a 3-chambered heart.
• The heart pumps to move blood throughout the
  body.

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The Human Heart
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The Cardiac Cycle

• The cardiac cycle is the series of muscle
  contractions and relaxations. This is the
  heartbeat that is heard with a stethoscope.
• Contraction is called systole and the relaxation
  period is called diastole.
• The chambers contract and relax together.

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Blood Flow through the Heart
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Heartbeat

• Each heart beat starts with the pacemaker. These
  are cells located in the inner wall of the right
  atrium.
• This pacemaker (sinoatrial node) creates
  electrical impulses that cause the cardiac muscle
  to contract.

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• The impulse spreads to the atrioventricular node
  in the left atrium and produces a unified
  contraction of the atria.
• The signal is conducted through fibers in the
  ventricles called the bundle of HIS and the
  Purkinje fibers which generate a strong
  ventricular contraction.

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Composition of Blood

• Blood contains cells, fluids, and dissolved
  substances.
• The main components are
• Erythrocytes red blood cells
• Leukocytes white blood cells
• Plasma fluid portion of blood
• Platelets small cell fragments

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Erythrocytes

• Red blood cells contain the oxygen-transporting
  protein called hemoglobin.
• It gives these cells their characteristic red
  color.
• They live about 120 days.

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Erythroctyes

• New cells are made in the marrow of the long
  bones.
• A hormone in the kidneys regulates the
  production.
• Human RBCs do not have a nucleus.

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Leukocytes

• White blood cells are the bodys second line of
  defense after the skin and mucous membranes.
• There are 5 types of WBCs, each with its own role
  in defending the body.

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Neutrophils

• Neutrophils ingest bacteria at a wound site.
• Most abundant white blood cell.

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Eosinophils

• Eosinophils also destroy bacteria. They are
  cytotoxic.

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Basophils

• Basophils play a role in ridding the body of
  foreign matter by ingesting the substances.

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Monocytes

• Monocytes absorb bacteria with the body at the
  site of an infection.
• Mature into macrophages.
• Increase greatly in response to infection.

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Lymphocytes

• Two types, called B-Cells and T-Cells.
• When stimulated, B-cells become plasma cells.
• T-cells regulate the immune response of the
  leukocytes reduced by AIDS/HIV

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Plasma

• The fluid portion of the blood.
• Contains
• Water,
• Proteins
• Dissolved ions
• Amino acids and sugars
• Carries CO2, wastes, digested food, hormones,

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Platelets

• Platelets are irregularly-shaped, colorless
  bodies that form clots to stop bleeding.
• Platelets gather at the wound and attempt to
  block the blood flow.

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Blood Pressure

• Blood vessels have different amounts of muscle
  and elasticity depending on the function of the
  vessel.
• Arteries are very muscular due to the pressure of
  the blood when the heart contracts. The artery is
  very elastic so that it can expand and contract
  as blood flows.
• The contraction of the artery muscles help push
  blood through the system.

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• Veins are not as muscular or elastic because the
  pressure is not as great.
• Veins have valves to prevent the backflow of
  blood.
• Gravity and skeletal muscle contraction helps
  direct blood through the veins (in addition to
  the blood flow from behind).

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Blood Pressure

• A healthy blood pressure is maintained by
  hormones, and the nervous, excretory, and
  circulatory systems.
• About 20 of the US adult population has high
  blood pressure (hypertension).
• This forces the heart work harder and can damage
  vessels, causes strokes and contributes to
  artherosclerosis.

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Muscle Contraction

• Heart muscle is called cardiac muscle. It is
  involuntary (contacts without your control).
• Muscle is made of two proteins actin and
  myosin.
• Actin filaments are anchored at a z-line. Myosin
  filaments contact the actin with crossbridges.
  During contraction the crossbridges walk along
  the actin toward the z-lines by a release-attach
  motion, which in turn causes contraction.

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Muscle Contraction Animations

• http//bio.winona.msus.edu/berg/ANIMTNS/SlidFila.h
  tm
• http//3dotstudio.com/zz.html
• http//www.sci.sdsu.edu/movies/actin_myosin_gif.ht
  ml