Blood Flashcards
Blood 1
• Description – An atypical connective tissue – Develops from mesenchyme – Red blood cells (erythrocytes), platelets, and white blood cells (leukocytes) in a liquid fluid matrix (plasma) • Function – Transport of respiratory gases, nutrients, hormones, and wastes – Helps body regulate temperature • Location – Within blood vessels and heart
Blood 2
• Blood circulation is powered by the pumping action of the heart • Blood volume – Males: 5–6 liters – Females: 4–5 liters
Composition of Blood
• Contains cellular and liquid components
• A specialized connective tissue
– Erythrocytes (45% of blood)
– Leukocytes and platelets (<1% of blood)
– Plasma (55% of blood)—fluid portion with
fibrinogen and other clotting factors
• Hematocrit—measure of % RBC volume in
blood
– Males: 47% ± 5%
– Females: 42% ± 5%
Blood Plasma
• Straw-colored, sticky fluid portion of blood
which lacks RBCs, WBCs, and platelets
• Approximately 90% water
• Contains over 100 kinds of molecules
– Ions e.g. Na+ and Cl–
– Nutrients: sugars, lipids, amino acids, and
proteins
– Three main proteins: albumin, globulins,
and fibrinogen
Erythrocytes 1
• Oxygen-transporting cells—7.5 µm in
diameter (diameter of capillary 8—10 µm)
• Most numerous of the formed elements
– Females: 4.3–5.2 million cells/cubic mm
– Males: 5.2–5.8 million cells/cubic mm
• Have no organelles or nuclei
• Are the ideal measuring tool for estimating
sizes of nearby structures
Erythrocytes 2
Are packed with oxygen-carrying hemoglobin • Hemoglobin molecule bears oxygen molecules • Oxidation of iron atoms in hemoglobin molecules gives blood its red color
Erythrocytes 3
Pick up O2 at lung capillaries • Release O2 across other tissue capillaries • Structural characteristics contribute to respiratory function – Biconcave shape 30% more surface area – Lack mitochondria and do not consume O2 they pick up
Leukocytes =
White Blood Cells (WBCs) 1
• Originate in bone marrow
• 4,800–11,000 WBCs/cubic millimeter
• Protect the body from infectious microorganisms
• Function outside the bloodstream in loose
connective tissue where they move in amoeboid
fashion
• Diapedesis—circulating leukocytes leave
capillaries and venules by actively squeezing
between the endothelial cells
Leukocytes =
White Blood Cells (WBCs) 2
• Two types of leukocytes
– Granulocytes
– Agranulocytes
• Never Let Monkeys Eat Bananas • Neutrophils, Lymphocytes, Monocytes, Eosinophils, Basophils
Relative percentages of
leukocytes (= White Blood Cells)
Granulocytes (contain cytoplasmic granules)
• Neutrophils (50-70%)
• Eosinophils (1-4%)
• Basophils (0.5-1%)
Agranulocytes (lack cytoplasmic granules)
• Lymphocytes (20-45%)
• Monocytes (3-8%)
Granulocyte neutrophils
• Neutrophils—most numerous WBC at 50-70% – Phagocytize and destroy bacteria – Nucleus—has two to six lobes
Granulocyte eosinophils
Eosinophils— compose 1–4% of all WBCs – Bilobed nucleus – Play roles in human defense response to: • allergic reactions • parasitic infections
Granulocyte basophils
• Basophils—about 0.5-1% of all leukocytes – Nucleus—usually bilobed – Cytoplasmic granules secrete histamines – Function in inflammation mediation – Similar function to mast cells
Agranulocyte lymphocytes
• Lymphocytes—compose 20–45% of WBCs – The most important cells of the immune system – Large spherical nucleus— stains dark purple – Effective in fighting infectious organisms – Act against a specific foreign molecule (antigen)
Agranulocyte lymphocytes
• Two main classes of lymphocytes
– T cells—attack foreign cells directly
– B cells—multiply to become plasma
cells that secrete antibodies
Agranulocyte monocyte
Monocytes— compose 3–8% of WBCs – The largest leukocyte – Nucleus is kidney shaped – Transform into macrophages which are phagocytic cells
Platelets
Cell fragments which break off from
megakaryocytes
• Function in clotting of blood
Blood Cell Formation
Hematopoiesis—process by which
blood cells are formed in red bone
marrow
Red Bone Marrow as the Site
of Hematopoiesis
• Actively generates new blood cells • Contains immature erythrocytes • In adults, red bone marrow is located – between trabeculae of spongy bone of axial skeleton – In pelvic girdle is made of two hip bones – in proximal epiphyses of humerus & femur
Red Bone Marrow as the Site
of Hematopoiesis
Tissue framework of bone marrow made of
reticular connective tissue rich in reticular
fibers
• Fibroblasts covering and secreting the
reticular fiber network are reticular cells
• Blood sinusoids run throughout the reticular
tissue and blood cells enter the blood stream
via sinusoidal capillaries in red marrow
Red Bone Marrow
• Reticular tissue of bone marrow also
contains macrophages that extend
pseudopods to capture antigens and clean
the blood
• Some cells of the reticular network are
mesenchymal stem cells that can give rise
to fat cells, osteoblasts, chondrocytes,
fibroblasts, and muscle cells
Yellow marrow
- Contain many adipose cells
- Located in long bones of adults
- Typically is dormant
Cell Lines in Blood Cell
Formation
Blood cells originate in bone marrow
• All originate from one cell type: blood stem
cell (multipotential hematopoeitic stem cell)
– Lymphoid stem cells
• give rise to lymphocytes
– Myeloid stem cells
• give rise to all other blood cells
Lymphoid stem cells form:
- B-cell lymphocytes
* T-cell lymphocytes
Myeloid stem cells
form the following
Megaloblasts form platelets • Proerythroblasts form erythrocytes • Myeloblasts form granulocytes (eosinophil, basophil, neutrophils) • Monoblasts form monocytes
Genesis of erythrocytes
• Committed cells are proerythroblasts
• Remain in the reticulocyte stage for 1–2
days in blood circulation
• Reticulocytes make up about 1–2% of all
erythrocytes
Formation of leukocytes
- Myeloblasts form granulocytes
* Monoblasts form monocytes
Formation of platelets
• Megakaryoblasts form
megakaryocytes which break apart
into platelets
Disorders of platelets
• Thrombocytopenia: abnormally low
concentration of platelets
Disorders of erythrocytes
Polycythemia: abnormal high level of erythrocytes • Anemia: low erythrocyte levels (hematocrit) and/or low hemoglobin concentrations • Hemachromatosis: inherited disorder with abnormal excess of iron
Sickle cell disease
• Inherited condition • Results from a defective hemoglobin molecule in erythrocytes • Erythrocytes distort into a sickle shape which protects person from malaria
Disorders of Leukocytes
• Leukemia—a form of cancer with two main
types:
• Abnormal lymphoblastic cells
• Abnormal myeloblastic cells
The Blood Throughout Life
By three weeks gestation, the first blood cells
develop in blood islands of the yolk sac
• Late in the second month gestation, liver and
spleen take over blood formation
• Bone marrow becomes major hematopoietic
organ at seventh month gestation
