Podcast
Questions and Answers
What is the main structural component of large elastic arteries, such as the aorta?
Which type of artery is defined as having a relatively thin tunica adventitia and mainly consists of elastic fibers?
What type of capillary is characterized by endothelial cells that have no fenestrae?
Which functional role do pericytes in capillaries potentially serve?
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Where can sinusoidal capillaries primarily be found?
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What is the typical diameter range of normal red blood cells (erythrocytes)?
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Which type of white blood cell constitutes 50-70% of the total leukocyte count?
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What is the primary function of eosinophils in the vascular system?
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What is the structure of neutrophils characterized by?
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What distinguishes reticulocytes from mature erythrocytes?
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How many millions of red blood cells (RBCs) are typically found in one mm³ of blood?
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What type of leukocyte has a nucleus that often appears S-shaped?
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What characterizes the cytoplasm of eosinophils?
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What is the function of heparin secreted by specific granules?
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Which type of lymphocyte is primarily responsible for humoral immunity?
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What characteristic is used to differentiate large lymphocytes from small lymphocytes?
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Which layer of blood vessels contains circular smooth muscle cells?
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What is a primary function of monocytes?
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What components are found in the granulomere of blood platelets?
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Which structure is considered the innermost layer of blood vessels?
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What type of granules do mast cells contain that is similar to specific granules?
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Study Notes
Blood Cells
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Red Blood Cells (RBCs or Erythrocytes)
- Shape: Biconcave discs
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Size: 6-9 microns in diameter (average 7.5 µm)
- Normocytes: Normal size RBCs
- Macrocytes: RBCs larger than 9 µm (e.g., macrocytic anemia)
- Microcytes: RBCs smaller than 6 µm (e.g., microcytic anemia)
- Number: 4.5-5.5 million/mm3 of blood
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Structure:
- Lack nuclei and organelles
- Contain hemoglobin (Hb) enclosed by cell membrane
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Reticulocytes: Immature RBCs (1% of circulating RBCs)
- Slightly larger than mature RBCs
- Contain free ribosomes and a few mitochondria
White Blood Cells (WBCs or Leukocytes)
- Total Leukocytic Count: 4,000 – 11,000/mm3 of blood
- Differential Leukocytic Count: Percentage of each type of WBC in total WBC count
Granular Leukocytes
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Neutrophils (Polymorphs or Polymorphonuclear Leukocytes): 50-70% of WBCs
- Nucleus: Segmented (lobulated) with 2-5 lobes (usually 3)
- Cytoplasm: Contains specific granules (small, numerous) and non-specific (azurophilic) granules (large, less numerous, lysosomes)
- Function: Antibacterial, crucial for acute inflammation
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Eosinophils: 1-4% of WBCs
- Nucleus: Bilobed, horse-shoe shaped
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Cytoplasm:
- Specific eosinophilic granules: Contain antiparasitic and histaminase
- Non-specific granules: Lysosomes containing hydrolytic enzymes
- Functions: Antiallergic, antiparasitic
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Basophils: 0-0.5% of WBCs
- Nucleus: S-shaped
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Cytoplasm:
- Specific granules: Contain heparin (anticoagulant) and histamine (allergy)
- Non-specific granules: Lysosomes containing hydrolytic enzymes
- Functions: Secretion of heparin and histamine
Non-Granular Leukocytes
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Lymphocytes: 20-40% of WBCs
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Small lymphocytes:
- Nucleus: Large, rounded, condensed chromatin
- Cytoplasm: Scanty, few organelles
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Large lymphocytes:
- Nucleus: Large, rounded with indentation, less condensed chromatin
- Cytoplasm: Basophilic (due to increased ribosomes)
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Functions:
- Humoral immunity (B-lymphocytes)
- Cellular immunity (T-lymphocytes)
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Small lymphocytes:
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Monocytes: 2-8% of WBCs
- Nucleus: Oval or kidney-shaped, eccentrically placed
- Cytoplasm: Contains lysosomes
- Functions: Phagocytosis, production of mononuclear phagocytic system (MPS)
Blood Platelets (Thrombocytes)
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Light Microscopy (L/M):
- Peripheral hyalomere (pale)
- Central granulomere (granular)
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Electron Microscopy (EM):
- Hyalomere: Contains microtubules, actin, and myosin filaments
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Granulomere: Contains:
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Dense granules:
- Alpha granules: Fibrinogen
- Delta granules: ADP, ATP, epinephrine, and serotonin
- Lambda granules: Lysosomes
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Dense granules:
Blood Vessels
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Cardiovascular System: Heart + blood vessels
- Arteries: Carry blood from the heart to tissues
- Veins: Carry blood from tissues to the heart
- Capillaries: Arterio-venous connections for exchange
General Structure of Blood Vessels
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Tunica Intima (Innermost):
- Endothelium: Simple squamous cells
- Subendothelium: Loose connective tissue
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Tunica Media (Middle):
- Smooth muscle cells: Circular arrangement
- Elastic fibers: Variable amounts
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Tunica Adventitia (Outermost):
- Loose connective tissue
- Vasa vasorum: Small blood vessels that supply the outer part of the vessel wall
Arteries
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Large (Elastic) Arteries: Aorta and its major branches
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Specific Features:
- Tunica media: Concentric layers of elastic laminae with circular smooth muscle between them
- Tunica adventitia: Relatively thin
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Specific Features:
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Medium Sized (Muscular) Arteries:
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Specific Features:
- Tunica media: Predominantly smooth muscle
- Tunica adventitia: Thicker than in large arteries
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Specific Features:
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Arterioles: Smallest arteries
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Specific Features:
- Tunica media: One or two layers of smooth muscle
- Tunica adventitia: Thin
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Specific Features:
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Metarterioles: Connect arterioles to capillaries
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Specific Features:
- Precapillary sphincters: Regulate blood flow into capillaries
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Specific Features:
Veins
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Large veins:
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Specific Features:
- Tunica media: Thin with few layers of smooth muscle
- Tunica adventitia: Thickest layer, contains longitudinal smooth muscle
- Valves: Prevent backflow of blood
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Specific Features:
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Medium sized veins:
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Specific Features:
- Tunica media: Thinner than arteries of similar size
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Specific Features:
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Venules: Smallest veins
Capillaries
- Smallest channels in the circulatory system
- Arise from metarterioles or directly from arterioles
- Re-collect to form venules
Structure of Capillaries
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Light Microscopy (L/M):
- Endothelial cells: Single layer (1-3 cells)
- Basal lamina:
- Pericytes: Partly surround endothelial cells with long cytoplasmic processes, contain actin and myosin (contractile function), produce new smooth muscle cells after injury
Types of Blood Capillaries
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Continuous capillary: No fenestrae (pores)
- Location: Brain
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Fenestrated capillary: Large fenestrae in endothelial cells, continuous basal lamina
- Location: Renal glomeruli, endocrine glands
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Sinusoidal capillary: Tortuous, wide lumen, multiple fenestrae, discontinuous basal lamina
- Location: Liver, bone marrow, spleen
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Description
This quiz covers the essential characteristics of red and white blood cells, including their structure, types, and functions. Learn about the differences between normocytes, macrocytes, and microcytes, along with the various types of leukocytes and their percentages in blood. Test your understanding of hematology with this informative quiz.