BIOL 3542 Lecture Notes - Lecture 16: Coumarin, Cross-Link, Thrombopoietin
26 Jun 2018
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Human Physiology II
Chapter 16: Blood
Plasma and the Cellular Elements of Blood
blood is connective tissue composed of cellular elements suspended in plasma
plasma makes up ¼ ECF
blood is circulating portion of extracellular compartment
Plasma Is Extracellular Matrix
Plasma: fluid matrix of blood, within which cellular elements are suspended
water is main component (92%)
proteins = 7%
dissolved organic molecules, ions, trace elements and vitamins, dissolved oxygen and
carbon dioxide = 1%
identical in composition to interstitial fluid except for plasma proteins (albumins = 60%,
globulins, fibrinogen, transferrin) made by liver
presence of proteins makes osmotic pressure of blood higher than interstitial fluid, pulls
water from interstitial fluid into capillaries, offsets filtration out of capillaries created by
blood pressure
proteins participate in blood clotting, immune defense, as carriers for steroid hormones,
cholesterol, drugs and certain ions, act as hormones or extracellular enzymes
Blood Cell Production
Pluripotent Hematopoietic Stem Cell: blood cell precursor found in bone marrow that can
develop into many different cell types (soft tissue that fills hollow center of bones)
become uncommitted stem cells, then progenitor cells that’re committed to developing
into one/two cell types
progenitor cells differentiate into red blood cells, lymphocytes other white blood cells,
megakaryocytes (parent of platelets)
Blood Cells Are Produced in the Bone Marrow
Hematopoiesis: synthesis of blood cells
begins early in embryonic development, continues throughout life
3rd week of development: specialized cells in yolk sac of embryo form clusters, some become
endothelial lining of blood vessels, rest become blood cells
common origin of endothelium, blood cells explains why cytokines that control
hematopoiesis are released by vascular endothelium
blood cell production spreads from yolk sac to liver, spleen, bone marrow as embryo
develops
at birth, liver, spleen no longer produce blood cells
hematopoiesis continues in marrow of all bones until age 5
active marrow regions decrease until just the pelvis, spine, ribs, cranium, proximal ends of
long bones are left in adulthood
inactive marrow yellow because of abundance of adipocytes (fat cells)
find more resources at oneclass.com
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active bone marrow is red because it contains hemoglobin
Hemoglobin: oxygen-binding protein of red blood cells
liver, spleen, inactive marrow sites can resume blood cell production in times of need
25% of developing cells = red blood cells; 75% = white blood cells
lifespan of white blood cells (12h) considerably shorter than red blood cells (4mos)
Hematopoiesis Is Controlled by Cytokines
Cytokines (a.k.a. factors): peptides/proteins released from one cell that affect growth/activity of
another cell
colony-stimulating factors made by endothelial cells, white blood cells
erythropoietin controls red blood cell synthesis
Colony-Stimulating Factors Regulate Leukopoiesis
Colony-Stimulating Factors: regulate leukocyte production, development (leukopoiesis)
made by endothelial cells, marrow fibroblasts, leukocytes
induce cell division (mitosis), maturation in stem cells
oleukocyte loses ability to undergo mitosis once it matures
production of new leukocytes regulated by existing white blood cells, allowing leukocyte
development to be tailored to body’s needs
bacterial infection causes elevated numbers of leukocytes in blood (high percentage are
neutrophils)
cytokines released by active leukocytes stimulate production of additional
neutrophils, monocytes
a person with a viral infection may have high, normal or low white cell count but often show
increase in percentage of lymphocytes
Leukemias: group of diseases characterized by abnormal growth, development of leukocytes
Neutropenias: patients have too few leukocytes, unable to fight off bacterial/viral infections
Thrombopoietin Regulates Platelet Production
Thrombopoietin (TPO): glycoprotein that regulates growth, maturation of megakaryocytes
(platelet parent cells)
produced in liver
thrombocyte = platelet
Erythropoietin Regulates RBC Production
red blood cell production (erythropoiesis) controlled by glycoprotein erythropoietin
(EPO), assisted by cytokines
erythropoietin made in adult kidneys
stimulus for EPO synthesis, release is hypoxia (low oxygen levels of tissues) which
stimulates production of transcription factor hypoxia-inducible factor 1 (HIF-1) which turns
on EPO gene to increase EPO synthesis
helps body maintain homeostasis
EPO puts more hemoglobin into circulation to carry oxygen by stimulating synthesis of
red blood cells
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Plasma and the cellular elements of blood blood is connective tissue composed of cellular elements suspended in plasma plasma makes up ecf blood is circulating portion of extracellular compartment. Plasma: fluid matrix of blood, within which cellular elements are suspended. Pluripotent hematopoietic stem cell: blood cell precursor found in bone marrow that can develop into many different cell types (soft tissue that fills hollow center of bones) Become uncommitted stem cells, then progenitor cells that"re committed to developing into one/two cell types. Progenitor cells differentiate into red blood cells, lymphocytes other white blood cells, megakaryocytes (parent of platelets) Blood cells are produced in the bone marrow. Begins early in embryonic development, continues throughout life. 3rd week of development: specialized cells in yolk sac of embryo form clusters, some become endothelial lining of blood vessels, rest become blood cells. Hemoglobin: oxygen-binding protein of red blood cells liver, spleen, inactive marrow sites can resume blood cell production in times of need.
