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The human circulatory system is subdivided into
- the cardiovascular system
- the lymphatic system
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closed or open cardiovascular system?
closed
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Blood is the
- fluid in the vessels of the cardiovascular system
- it transports everything that must be carried from one place to another in the body
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Blood circulation is powered by the
pumping action of the heart
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Functions of blood:
- carries things throughout the body
- - respiratory gases
- - nutrients, waste
- - hormones
- - cells of the immune system and helps body regulate temperature
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The average volume of blood in the body is about how much in adult males/females
- 5-6 L in adult males
- 4-5 L in adult females
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Classified as a type of connective tissue because it consists of
cellular and liquid components
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-A nonliving fluid matrix called the
plasma
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-Formed elements (Living cells): (3)
- erythrocytes
- leukocytes
- thrombocytes
- (suspended in the plasma)
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-NO Fibers (fibrin threads) visible when
clotting occurs
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• Spinning blood in a centrifuge: Buffy coat contains
leukocytes and platelets
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• Spinning blood in a centrifuge: Hematocrit has the percentage of the blood volume that consists of
erythrocytes (averages 45%; males 47% ±5% and females 42% ± 5%
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When blood is centrifuges, what is the order from top to bottom of the layers?
- Plasma
- Buffy coat
- erythrocytes
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Over 100 different substances are dissolved in suspended in plasma
(90% water): ions, nutrients, gases, hormones, wastes, metabolites, electrolytes, and proteins.
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The composition of plasma varies continuously as cells and
- substances are added and/or removed from the
- blood
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Plasma contains three main types of proteins
- 1) Albumin
- 2) Globulins
- 3) Fibrinogen
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Albumin
contributes to plasma osmotic pressure, which helps keep water from diffusion out of the blood-stream into the extracellular matrix of tissues
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Globulins
include both antibodies and blood proteins that transport lipids, iron, and copper
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Fibrinogen
functions in clotting
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Three types of formed elements are present in blood
- Red blood cells (erythrocytes)
- white blood cells (leukocytes)
- platelets (thrombocytes)
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Functions of the formed elements in blood
- Transport oxygen and a small percentage of carbon dioxide.
- Part of the body’s nonspecific defenses and the immune system
- Hemostatis (blood clot formation)
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Neither erythrocytes (which lack nuclei and organelles) nor platelets (which are cell fragments) are
true cells.
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Only leukocytes are considered
true cells
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Most of the blood cells cannot divide; they survive in the bloodstream for only a short time (hours to months) before being replaced by the division of precursor cells in the
bone marrow
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Oxygen-transporting cells – ___ μm in diameter
7.5
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-Live 100–120 days and originate in the
bone marrow
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Most numerous of the formed elements
- Females: 4.3–5.2 million cells/mm 3
- Males: 5.2–5.8 million cells/mm 3 (~25 trillion total)
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Mature RBCs have no organelles or nuclei... Instead their
- cytoplasm is filled with
- hemoglobin – an oxygen-carrying protein
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_______ pick up oxygen at the lung capillaries and release it
- across other tissue capillaries throughout the body
- Erythrocytes
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Their special structural characteristics contributes to their respiratory
- function:
- 1) Without organelles and discounting water, RBCs are 97% hemoglobin (Each RBC contains ~280 million hemoglobins!!!)
- 2) Their biconcave shape – 30% more surface area for rapid diffusion of oxygen.
- 3) Generate their energy anaerobically...thereby conserving any oxygen they pick up
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Leukocytes (5)
- Neutrophils
- Eosinophils
- Basophils
- Lymphocytes
- Monocytes
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Leukocytes are the only formed elements that are ______ cells, with the usual organelles and prominent nuclei.
complete
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Leukocytes function
- protects the body from infectious microorganisms
- less numerous than erythrocytes... 4,800 to 11,000 leukocytes/mm3
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Leukocytes function outside the bloodstream in the loose connective tissue, where _______ occur
infections
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Diapedesis
process of circulating leukocytes leaving the capillaries
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Which leukocytes are granulocytes?
- neutrophil
- eosinophil
- basophil
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Which leukocytes are agranulocytes?
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Neutrophils:
- -Most numerous WBC (60% of WBCs)
- -Nucleus – has two to six interconnected lobes
- -Granules contain digestive enzymes that specifically destroy the
- cell walls of bacteria.
- -Function: Phagocytize and destroy bacteria; first line of defense in
- an inflammatory response
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Eosinophils:
- - Compose 1–4% of all WBCs
- - Nucleus – has two lobes interconnected by a broad band.
- - Granules contain digestive enzymes (not specific for bacteria).
- -Function: Play roles in ending 1) allergic reactions by phagocytosing allergens and 2) parasitic infections by releasing parasite-digesting enzymes, esp. in the digestive system
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• Basophils:
- - About 0.5% of all leukocytes = rarest
- - Nucleus – usually two lobes
- - Weakly phagocytic
- - Function: Granules secrete histamines (function in mediating inflammation) during allergic responses and parasitic infections
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Lymphocytes:
- - Compose 20–45% of WBCs
- - Nucleus – spherical; occupies most of the cell volume
- - Function: The most important cells of the immune system; most are found in lymphoid tissue; effective in fighting infectious organisms; act against a specific foreign molecule (antigen)
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Two main classes of lymphocytes:
T cells and B cells
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T cells (killer T-lymphocytes):
attack foreign eukaryotic cells directly; bind to antigen-bearing cells and punch holes in its membrane...which triggers apoptosis
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B cells:
- multiply to become plasma cells that secrete antibodies (proteins that mark specific antigens for destruction by macrophages)
- mostly attack bacteria and bacterial toxins
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Natural Killer cells:
attack cells that lack “self” surface molecules
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Monocytes:
- - Compose 4–8% of WBCs
- - The largest leukocytes
- - Nucleus – kidney shaped
- -Transform into macrophages... phagocytic cells that possess pseudopods and ingest a wide variety of foreign cells, molecules, and tiny pieces of debris
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Platelets (thrombocytes):
- -Disc-shaped, plasma membrane-enclosed fragments of cytoplasm that form by breaking off from larger cells called megakaryocytes
- -Function: in clotting of blood by adhering to collagen near the edges of tears in blood vessels and by releasing chemicals that attract clotting proteins, cause vasoconstriction, and initiate inflammation
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Hematopoiesis:
- the process by which blood cells are
- formed
- begins in the early embryo and continues throughout life
- All blood cells originate in the bone marrow, at a rate of 100 billion new cells a day
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Bone marrow is located within
all bones
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-Red marrow:
- actively generates new blood cells
- Contains immature erythrocytes
- remains in proximal epiphyses of humerus and femur, girdles, and axial skeleton in adulthood
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Yellow marrow
- dormant (makes blood cells only in emergencies)
- Contains many fat cells and is located in the medullary cavities of long bones of adults
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All originate from a blood stem cell...
a pluripotential hematopoetic stem cell, which divide continuously and make
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2 types of progenitor cells:
- a) Lymphoid stem cells: give rise to lymphocytes
- b) Myeloid stem cells: give rise to all other blood cells
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