circulatory system. circulatory system circulatory system: efficient distribution system network of...
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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 Vessels1. 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 Vessels3. Veins: 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 networkCritical to accomplishing the main functions of
the circulatory systemDistribution of oxygen & nutrients, and removal of waste
products
Cells in body tissues surrounded by interstitial fluid
Chemical Exchange between Blood & Body Tissues
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 tissuePart liquid, part cellular material
* PlasmaComposes 55% of the volume of bloodPlasma = 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 hormonesRemoves waste (carbon dioxide)Fights infection
Blood consists of cells suspended in plasma
Blood:Connective tissueFlows through blood vesselsFive liters of blood
Takes 1 minute to make a complete circuitComposed of:
55% Plasma45% RBCs
Blood consists of cells suspended in plasmaPlasma (45%)
90% water10% dissolved salts, proteins, and other
substancesRBCs
ErythrocytesMost numerous cells in blood5 million RBCs in 1 drop of bloodContains hemoglobinProduced in the bone marrow (2 million per
second)Replaced every 120 days
Blood consists of cells suspended in plasma
HemoglobinProtein that binds with oxygen for transport
to cellsContains iron which contains a high affinity
for oxygen
Blood consists of cells suspended in plasma
WBCsLeukocytesFight infection and prevents growth of cancer4,000-11,000 WBCs in 1 drop of bloodInfection increases the number of WBCsMost action takes place in the interstitial fluid
Blood consists of cells suspended in plasma
Blood clotting:Platelets help with blood clottingOriginate from the bone marrow250,000 – 500,000 in a drop of bloodStick to damaged siteRelease clotting factorsFibrin produced (Protein)Patch forms and dries into a scab