Transcript Circulatory System

CIRCULATORY SYSTEM
Circulatory System
Circulatory system:
• Efficient distribution system
• Network of 100,000 km of blood vessels
•Supplies cells with nutrients and oxygen and removes
carbon dioxide and waste products
• Transports hormones
•Plays an important role repairing tissues and protecting
the body from infection
Organs of the Circulatory System
* Blood: Type of connective tissue (cells & liquid)
* Heart: Multi-chambered, muscular organ
- Overall flow of blood via blood vessels  from
the heart to the tissues
throughout the body back to the
heart
- Body contains 5 L of blood
3 Types of Blood Vessels
1. Capillaries:
• Microscopic blood vessels- make contact with all cells of the
body
• Walls of capillaries consist of a thin layer of epithelial tissue 
enables diffusion of nutrients and oxygen out of the blood &
the diffusion of waste products into the blood
2. Arteries:
• Blood flows from the heart to the capillaries through thick
walled blood vessels = arteries
• Walls of arteries = epithelial tissue wrapped in layers of
smooth muscle and connective tissue
• Muscle tissue enables arteries to constrict & dilate; Blood in
arteries is under pressure due to the heart’s pumping action
3 Types of Blood Vessels
3. Veins:
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Blood returns from the capillaries to the heart through vessels
= veins
Walls of veins consist of epithelial tissue surrounded by smooth
muscle & connective tissue… but muscle layer is thinner than
that in arteries
Blood is under little pressure
Contracting skeletal muscles squeezes the
veins and forces blood back to the heart
Chemical Exchange between Blood &
Body Tissues
 Most cells are no further than 10 micrometers from a
capillary and the blood inside
 Capillary network
 Critical to accomplishing the main functions of the
circulatory system
 Distribution of oxygen & nutrients, and removal of waste products
 Cells in body tissues  surrounded by interstitial fluid
Chemical Exchange between Blood &
Body Tissues
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Substances in capillaries do not enter tissue
cells directly
1. First: Substances in capillaries enter the
interstitial fluid
2. Second: Substances in the interstitial fluid then
enter the cells
Chemical Exchange between Blood &
Body Tissues
• Exchange of substances between blood & interstitial
fluid occurs in several ways:
• Small molecules (oxygen, carbon dioxide)  diffuse across the
membrane or pass through gaps between the epithelial cells
of the capillary wall
• Oxygen & nutrients move from the blood into the interstitial fluid
• Carbon dioxide & other small waste products move from the
interstitial fluid into the blood
• Larger molecules move across the membranes by exocytosis and
endocytosis
Chemical Exchange between Blood &
Body Tissues
• Exchange of substances between blood & interstitial
fluid occurs in several ways:
• Blood pressure  forces fluid through the capillary wall
•
 At the artery end of a capillary  blood pressure forces
water, small solutes, and some dissolved proteins through the
gaps between the cells… However, blood cells & larger proteins
are too large to pass easily through the openings  remain in
the capillary
•  Result: Vein end of the capillary in hypertonic compared to
the surrounding interstitial fluid  Thus, water reenters the
vein end of the capillary via osmosis… Blood pressure is very
low at the vein end of the capillary, so it does not oppose the
flow of fluid back into the capillary
Blood consists of Cells suspended in
Plasma
 * Blood
 Highly specialized tissue
 Part liquid, part cellular material
 * Plasma
 Composes 55% of the volume of blood
 Plasma = 90% water; Other 10% = dissolved salts,
proteins, transport substances
Blood consists of Cells suspended in
Plasma
 * Red blood cells (Erythrocytes):
 Constitutes the remaining 45% of the blood volume
 Carry oxygen from the lungs to all the tissues in
your body
 Each RBC  contains 250 million molecules of
hemoglobin (Protein that temporarily stores oxygen
for delivery to cells)
 Hemoglobin  Contains iron  Oxygen molecules
bind to the iron portion (heme group) of the
hemoglobin molecule
Red Blood Cells
 * Red blood cells (Erythrocytes):
 Produced in the bone marrow
 Distinctive shape due to the loss of their nuclei and
mitochondria  shape = flat disk, curves inward in
the middle  structure provides increased surface
area for oxygen transport
 Life span of a RBC = 100-120 days
Blood consists of Cells suspended in
Plasma
 * White blood cells (Leukocytes):
 Responsible for fighting infection and preventing
the growth of cancer
 When an infection invades your body  # of WBCs
increases
 Most of the action of the WBC takes place outside
the blood vessels in the interstitial fluid
3 Functions of Blood
 Blood:
 Carries oxygen, nutrients, and hormones
 Removes waste (carbon dioxide)
 Fights infection
Blood consists of cells suspended in
plasma
 Blood:
 Connective tissue
 Flows through blood vessels
 Five liters of blood
 Takes 1 minute to make a complete circuit
 Composed of:
 55% Plasma
 45% RBCs
Blood consists of cells suspended in
plasma
 Plasma (45%)
 90% water
 10% dissolved salts, proteins, and other substances
 RBCs
 Erythrocytes
 Most numerous cells in blood
 5 million RBCs in 1 drop of blood
 Contains hemoglobin
 Produced in the bone marrow (2 million per second)
 Replaced every 120 days
Blood consists of cells suspended in
plasma
 Hemoglobin
 Protein that binds with oxygen for transport to cells
 Contains iron which contains a high affinity for
oxygen
Blood consists of cells suspended in
plasma
 WBCs
 Leukocytes
 Fight infection and prevents growth of cancer
 4,000-11,000 WBCs in 1 drop of blood
 Infection increases the number of WBCs
 Most action takes place in the interstitial fluid
Blood consists of cells suspended in
plasma
 Blood clotting:
 Platelets help with blood clotting
 Originate from the bone marrow
 250,000 – 500,000 in a drop of blood
 Stick to damaged site
 Release clotting factors
 Fibrin produced (Protein)
 Patch forms and dries into a scab