Blood Cells: Identifying Neutrophils
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Questions and Answers

What is a characteristic feature of neutrophils in blood smears?

  • Multilobulated nuclei with thick strands
  • Multilobulated nuclei with very thin strands (correct)
  • No visible nucleus
  • Monolobulated nuclei with thin strands

    • What is another name for neutrophils?

  • Multilobulated cells
  • Polymorphonuclear leukocytes (correct)
  • Mononuclear leukocytes
  • Lymphoid cells

    • What happens to the nuclear shape of neutrophils?

  • It changes frequently (correct)
  • It remains constant
  • It becomes smaller
  • It becomes larger

    • What is the term used to describe the connection between the lobules of neutrophils' nuclei?

    <p>Thin strands</p> Signup and view all the answers

    What is the characteristic of neutrophils that allows them to be identified in blood smears?

    <p>Their multilobulated nuclei</p> Signup and view all the answers

    What is a distinctive feature of the cytoplasm of eosinophils?

    <p>Abundant coarse eosinophilic granules</p> Signup and view all the answers

    What is a characteristic of the nucleus of basophils?

    <p>Two or three irregular lobes</p> Signup and view all the answers

    What is a function of monocytes?

    <p>To mature into macrophages and other cells of the mononuclear phagocyte system</p> Signup and view all the answers

    What is a characteristic of platelets?

    <p>They have a lightly stained hyalomere region surrounding a more darkly stained central granulomere</p> Signup and view all the answers

    What is a feature of lymphocytes?

    <p>They have a thin rim of basophilic cytoplasm around the nucleus</p> Signup and view all the answers

    Which of the following lymphoid organs is classified as primary?

    <p>Thymus</p> Signup and view all the answers

    What is a common feature among lymph nodes, spleen, and mucosa associated lymphoid tissue?

    <p>They are all classified as secondary lymphoid organs</p> Signup and view all the answers

    Bone marrow is classified as which type of lymphoid organ?

    <p>Primary lymphoid organ</p> Signup and view all the answers

    Which of the following is NOT a lymphoid organ?

    <p>Liver</p> Signup and view all the answers

    What is a common function among thymus, bone marrow, spleen, and lymph nodes?

    <p>Participating in the immune response</p> Signup and view all the answers

    What is a major component of sections of red bone marrow?

    <p>Trabeculae of cancellous bone</p> Signup and view all the answers

    What type of cells can be distinguished at higher magnification in red bone marrow?

    <p>Hemopoietic cells and sinusoidal endothelial cells</p> Signup and view all the answers

    What is the location of hemopoietic cells in red bone marrow?

    <p>Between the sinusoids and adipocytes</p> Signup and view all the answers

    What is a challenge in identifying cells in routinely stained sections of red bone marrow?

    <p>Identifying the different types of hemopoietic cells</p> Signup and view all the answers

    What is the function of blood-filled sinusoids in red bone marrow?

    <p>To facilitate the exchange of oxygen and nutrients</p> Signup and view all the answers

    What is the function of the septa that extend into the thymus?

    <p>To divide the thymus into many incompletely separated lobules</p> Signup and view all the answers

    What type of cells are found in the cortex of the thymus?

    <p>Newly arrived lymphoblasts and macrophages</p> Signup and view all the answers

    What is a characteristic feature of thymic epithelial cells (TECs)?

    <p>They have both epithelial and reticular characteristics</p> Signup and view all the answers

    What is a characteristic of the medulla of the thymus?

    <p>It contains fewer and larger, mature lymphocytes</p> Signup and view all the answers

    What is a type of structure found in the medulla of the thymus?

    <p>Hassall corpuscles</p> Signup and view all the answers

    What is a characteristic of the young thymus?

    <p>It has a lot of lymphocytes in the cortex and fewer in the medulla</p> Signup and view all the answers

    What is the primary function of the blood-thymus barrier?

    <p>To prevent non-epithelial cells and free antigens from entering the thymus</p> Signup and view all the answers

    Which of the following components is NOT part of the blood capillary wall in the blood-thymus barrier?

    <p>Macrophages</p> Signup and view all the answers

    What is the function of the epithelioreticular cell layer in the blood-thymus barrier?

    <p>To present antigens to T-cells during education</p> Signup and view all the answers

    Which type of collagen is present in the perivascular connective tissue of the blood-thymus barrier?

    <p>Type III collagen</p> Signup and view all the answers

    What is the purpose of the basal lamina of the epithelial reticular cells in the blood-thymus barrier?

    <p>To support the structure of the epithelial reticular cells</p> Signup and view all the answers

    What is the approximate number of lymph nodes in the human body?

    <p>400-450</p> Signup and view all the answers

    Which part of the lymph node contains the nodules?

    <p>Cortex</p> Signup and view all the answers

    Where do lymphocytes and macrophages pass easily between the sinuses and the tissue of the lymph node?

    <p>All of the above</p> Signup and view all the answers

    What is the role of macrophages in the lymph node sinuses?

    <p>To phagocytose antigenic material and present it to T- and B-cells</p> Signup and view all the answers

    What is the order of lymph flow through a lymph node?

    <p>Subcapsular Sinus -&gt; Trabecular sinuses -&gt; Medullary sinuses</p> Signup and view all the answers

    What is the primary function of a lymph node?

    <p>To filter the blood and serve as an immune organ</p> Signup and view all the answers

    What type of vessels drain the capillary beds in a lymph node?

    <p>High endothelial venules (HEVs)</p> Signup and view all the answers

    What is the function of the red pulp in a lymph node?

    <p>To recycle old red blood cells</p> Signup and view all the answers

    What is the role of high endothelial venules (HEVs) in a lymph node?

    <p>To allow lymphocytes to leave the bloodstream and enter the lymph node tissue</p> Signup and view all the answers

    What is the significance of the hilus in a lymph node?

    <p>It is the site where blood vessels enter and leave the lymph node</p> Signup and view all the answers

    What is the entry point of blood into the spleen?

    <p>Splenic artery at the hilus</p> Signup and view all the answers

    What is the function of penicillar arterioles?

    <p>To piece through the lymphatic sheath and spill into splenic cords</p> Signup and view all the answers

    Which structure does blood percolate through after entering the splenic cords?

    <p>Splenic sinuses</p> Signup and view all the answers

    What is the final destination of blood after passing through the splenic sinuses?

    <p>Splenic vein at the hilus</p> Signup and view all the answers

    What surrounds the central arteries in the spleen?

    <p>Peri-arterial lymphatic sheath</p> Signup and view all the answers

    What is the primary component of the white pulp in the spleen?

    <p>T-cells</p> Signup and view all the answers

    Where are B-cells primarily located in the spleen's white pulp?

    <p>Lymph nodules</p> Signup and view all the answers

    What is the function of the periarterial lymphatic sheath in the spleen's white pulp?

    <p>To provide a site for T-cell aggregation</p> Signup and view all the answers

    What is the primary function of the red pulp in the spleen?

    <p>To remove old red blood cells</p> Signup and view all the answers

    What is the location of T-cells in the spleen's white pulp?

    <p>Periarterial lymphatic sheath</p> Signup and view all the answers

    What occurs in the white pulp of the spleen as the body is exposed to antigens?

    <p>Lymph nodules (w/ germinal centers) appear</p> Signup and view all the answers

    What is the significance of lymph nodules with germinal centers in the spleen?

    <p>They are involved in the production of antibodies</p> Signup and view all the answers

    What type of immune response leads to the appearance of lymph nodules with germinal centers in the spleen?

    <p>Adaptive immune response</p> Signup and view all the answers

    Where are lymph nodules with germinal centers located in the spleen?

    <p>White pulp</p> Signup and view all the answers

    What is the significance of germinal centers in lymph nodules?

    <p>They are involved in the production of antibodies</p> Signup and view all the answers

    Study Notes

    Neutrophils

    • Identified in blood smears by their multilobulated nuclei
    • Nuclei consist of lobules connected by very thin strands
    • Also known as polymorphonuclear leukocytes (PMNs) or polymorphs due to their multilobulated nuclei
    • Cells are dynamic, with nuclear shape changing frequently

    Eosinophils

    • Characterized by bilobed nuclei and abundant coarse cytoplasmic granules
    • Cytoplasm contains brightly eosinophilic specific granules and some azurophilic granules

    Basophils

    • Distinguished by large, strongly basophilic specific granules
    • Nucleus is often obscured by granules and has 2-3 irregular lobes

    Lymphocytes

    • Have a single nucleus that occupies most of the cell
    • Thin rim of basophilic cytoplasm surrounds the nucleus
    • Contain azurophilic granules

    Monocytes

    • Large agranulocytes that mature into macrophages and other cells of the mononuclear phagocyte system
    • Nuclei are eccentric, indented, kidney-shaped, or U-shaped

    Platelets

    • Often found in aggregates
    • Consist of a lightly stained hyalomere region surrounding a darker central granulomere containing membrane-enclosed granules

    Lymphoid Organs

    • Lymphoid organs are classified into two categories: primary and secondary lymphoid organs.

    Primary Lymphoid Organs

    • Thymus is a primary lymphoid organ.
    • Bone marrow is a primary lymphoid organ.

    Secondary Lymphoid Organs/Tissue

    • Spleen is a secondary lymphoid organ.
    • Lymph nodes are secondary lymphoid organs.
    • Lymphoid tissue is also classified as a secondary lymphoid organ.

    Components of Lymphoid Organs

    • Lymphoid organs include lymphocytes.
    • Thymus is a component of lymphoid organs.
    • Mucosa associated lymphoid tissue (MALT) is a component of lymphoid organs.
    • Lymph nodes are components of lymphoid organs.
    • Spleen is a component of lymphoid organs.

    Bone Marrow Structure

    • Red bone marrow consists of trabeculae of cancellous bone, adipocytes, and blood-filled sinusoids.
    • Sinusoids are located between hemopoietic cords or islands of developing blood cells.

    Component Cells

    • Sinusoidal endothelial cells have flattened nuclei.
    • Hemopoietic cells are densely packed in the cords between sinusoids and adipocytes.
    • Stromal cells and specific cells of the hemopoietic lineages are difficult to identify with certainty in routinely stained sections of marrow.

    Thymus Structure

    • The thymus is composed of vascularized connective tissue with a capsule that extends septa into the parenchyma, dividing the organ into many incompletely separated lobules.
    • The thymus consists of two main parts: the cortex and the medulla.

    Cortex of Thymus

    • The cortex is composed of newly arrived lymphoblasts, macrophages, and thymic epithelial cells (TECs).
    • TECs have characteristics of both epithelial and reticular cells and are morphologically and functionally diverse.
    • The cortex is divided into three layers.

    Medulla of Thymus

    • The medulla contains fewer and larger, mature lymphocytes.
    • The medulla has three related types of medullary TECs that form:
      • A second layer of the boundary between the cortex and medulla.
      • A cytoreticulum that supports less densely packed T lymphocytes, dendritic cells, and macrophages, and expresses many specialized proteins specific to cells of other organs.
      • Large aggregates of TECs, called Hassall corpuscles, sometimes arranged concentrically.

    Characteristics of Young Thymus

    • The young thymus is surrounded by a connective tissue (CT) capsule.
    • The cortex has a large number of lymphocytes, while the medulla has fewer.
    • The thymus does not have germinal centers.

    Blood-Thymus Barrier

    • The education of T-cells requires a highly controlled environment where antigens are presented exclusively by epithelial reticular cells.
    • The Blood-Thymus Barrier is crucial to ensure the absence of other cells and free antigens in this environment.

    Components of the Blood-Thymus Barrier

    • The blood capillary wall consists of: • Endothelial cells • Endothelial cell basal laminae • Pericytes

    Perivascular Connective Tissue

    • Composed of: • Type III collagen • Macrophages

    Epithelioreticular Cell Layer

    • Consists of: • Basal lamina of the epithelial reticular cells (type I ERCs) • Epithelial reticular cells

    Lymph Nodes

    • Bean-shaped and encapsulated structures
    • Human body has approximately 400-450 lymph nodes
    • Each lymph node has three major regions:
      • Outer cortex containing nodules
      • Deeper paracortex region lacking nodules
      • Medulla with prominent draining sinusoids adjacent to the hilum

    Lymphatic Circulation through a Lymph Node

    • Lymph nodes filter lymph
    • Lymph flow:
      • Afferent lymphatic vessels → Subcapsular Sinus
      • Subcapsular Sinus → Trabecular sinuses
      • Trabecular sinuses → Medullary sinuses
    • Lymphocytes and macrophages can easily pass between sinuses and lymph node tissue
    • Macrophages in sinuses monitor fluids, phagocytose antigenic material, and present it to T- and B-cells

    Blood Circulation Through a Lymph Node

    • Blood circulation into a lymph node begins with the entry of blood through an artery at the hilus.
    • The hilar artery branches into arterioles, which then feed into capillary beds.
    • The capillary beds are drained by high endothelial venules (HEVs), which are specialized sites where lymphocytes can leave the bloodstream and enter the lymph node tissue.

    Functions of the Spleen

    • The spleen filters the blood.
    • It destroys old red blood cells.
    • It serves as an immune organ.
    • The spleen is divided into two main parts: the Red Pulp and the White Pulp.

    Red Pulp

    • Responsible for RBC/hemoglobin recycling.

    White Pulp

    • Responsible for immune functions.

    Splenic Circulation

    • Blood enters the spleen via the splenic artery at the hilus
    • The splenic artery branches into trabecular arteries, which are surrounded by connective tissue trabeculae
    • Trabecular arteries give off central arteries, which leave the trabeculae and enter the spleen's substance, covered by a peri-arterial lymphatic sheath
    • Central arteries branch into penicillar arterioles, which pierce the lymphatic sheath and spill into splenic cords
    • Blood percolates through splenic cords and across the walls of splenic sinuses
    • Splenic sinuses drain into pulp veins
    • Pulp veins drain into trabecular veins, which then drain into the splenic vein at the hilus

    Blood and Lymphoid Tissue

    • Neutrophils: • Identified by their multilobulated nuclei, with lobules held together by very thin strands • Also called polymorphonuclear leukocytes, PMNs, or polymorphs • Dynamic cells with frequently changing nuclear shape
    • Eosinophils: • Bilobed nuclei • Abundant coarse cytoplasmic granules • Cytoplasm filled with brightly eosinophilic specific granules and azurophilic granules
    • Basophils: • Large, strongly basophilic specific granules • Granules usually obstruct the appearance of the nucleus, which has two or three irregular lobes
    • Lymphocytes: • Single nucleus occupying most of the cell • Thin rim of cytoplasm with fine azurophilic granules
    • Monocytes: • Large agranulocytes • Precursors to macrophages and other cells of the mononuclear phagocyte system • Eccentric nuclei, indented, kidney-shaped, or U-shaped
    • Platelets: • Often found in aggregates • Individual platelets have a lightly stained hyalomere region surrounding a more darkly stained central granulomere containing membrane-enclosed granules

    The Immune System and Lymphoid Organs

    • Lymphoid organs: • Classified as primary and secondary (effector) lymphoid organs/tissues • Include thymus, bone marrow, spleen, lymph nodes, mucosa-associated lymphoid tissue (MALT)
    • Primary lymphoid organs: • Thymus • Bone marrow
    • Secondary (effector) lymphoid organs/tissues: • Spleen • Lymph nodes • Mucosa-associated lymphoid tissue (MALT)

    Bone Marrow

    • Sections of red bone marrow: • Trabeculae of cancellous bone • Adipocytes (A) • Blood-filled sinusoids between hemopoietic cords or islands of developing blood cells
    • At higher magnification: • Flattened nuclei of sinusoidal endothelial cells can be distinguished • Variety of densely packed hemopoietic cells in the cords between the sinusoids and adipocytes

    Thymus

    • Vascularized connective tissue capsule • Extends septa into paranchyme, dividing the organ into many incompletely lobules
    • Cortex: • Composed of newly arrived lymphoblasts, macrophages, and thymic epithelial cells (TECs) • TECs have both epithelial and reticular cell characteristics • Divided into three groups (layers)
    • Medulla: • Contains fewer and larger, mature lymphocytes • Three related types of medullary TECs form a boundary layer, cytoreticulum, and Hassall corpuscles

    Blood-Thymus Barrier

    • Education of T-cells must occur in a controlled environment where antigens are only presented by epithelial reticular cells
    • The blood-thymus barrier ensures that no other cells or free antigens are present
    • Consists of: • Blood capillary wall (endothelial cells, endothelial cell basal laminae, pericytes) • Perivascular connective tissue (type III collagen, macrophages) • Epithelioreticular cell layer (basal lamina of the epithelial reticular cells, epithelial reticular cells)

    Lymph Nodes

    • Bean-shaped, encapsulated structures • Approximately 400-450 lymph nodes • Three major regions within each lymph node:
      • Outer cortex containing nodules
      • Deeper extension of cortex called the paracortex, which lacks nodules
      • Medulla with prominent draining sinusoids adjacent to the hilum

    Lymphatic Circulation through a Lymph Node

    • Lymph nodes filter lymph • Afferent lymphatic vessels drain lymph into the Subcapsular Sinus • Lymph then passes to the Trabecular sinuses • From there, the lymph goes to the Medullary sinuses • Lymphocytes and macrophages pass easily between these sinuses and the tissue of the lymph node

    Blood Circulation through a Lymph Node

    • Blood enters through an artery at the hilus • Arterioles branch from hilar artery to feed into capillary beds • Capillary beds are drained by high endothelial venules (HEVs) • HEVs drain into hilar vein • HEVs are sites where lymphocytes can leave the bloodstream to enter the lymph node tissue bed

    Spleen

    • Functions: • Filters the blood • Destroys old red blood cells • Serves as an immune organ • Divided into Red Pulp (RBC/hemoglobin recycling) and White Pulp (responsible for immune functions)

    Splenic Circulation

    • Blood enters via splenic artery at hilus • Splenic artery branches into trabecular arteries (which travel within connective tissue trabeculae) • Trabecular arteries give off branches known as central arteries which leave the trabecula and enter the substance of the spleen (covered by a peri-arterial lymphatic sheath) • Central arteries branch into penicillar arterioles that piece through the lymphatic sheath and spill into splenic cords • Blood percolates through splenic cords and across walls of splenic sinuses • Splenic sinuses drain into pulp veins • Pulp veins drain into trabecular veins • Trabecular veins drain into splenic vein at the hilus

    Blood and Lymphoid Tissue

    • Neutrophils: • Identified by their multilobulated nuclei, with lobules held together by very thin strands • Also called polymorphonuclear leukocytes, PMNs, or polymorphs • Dynamic cells with frequently changing nuclear shape
    • Eosinophils: • Bilobed nuclei • Abundant coarse cytoplasmic granules • Cytoplasm filled with brightly eosinophilic specific granules and azurophilic granules
    • Basophils: • Large, strongly basophilic specific granules • Granules usually obstruct the appearance of the nucleus, which has two or three irregular lobes
    • Lymphocytes: • Single nucleus occupying most of the cell • Thin rim of cytoplasm with fine azurophilic granules
    • Monocytes: • Large agranulocytes • Precursors to macrophages and other cells of the mononuclear phagocyte system • Eccentric nuclei, indented, kidney-shaped, or U-shaped
    • Platelets: • Often found in aggregates • Individual platelets have a lightly stained hyalomere region surrounding a more darkly stained central granulomere containing membrane-enclosed granules

    The Immune System and Lymphoid Organs

    • Lymphoid organs: • Classified as primary and secondary (effector) lymphoid organs/tissues • Include thymus, bone marrow, spleen, lymph nodes, mucosa-associated lymphoid tissue (MALT)
    • Primary lymphoid organs: • Thymus • Bone marrow
    • Secondary (effector) lymphoid organs/tissues: • Spleen • Lymph nodes • Mucosa-associated lymphoid tissue (MALT)

    Bone Marrow

    • Sections of red bone marrow: • Trabeculae of cancellous bone • Adipocytes (A) • Blood-filled sinusoids between hemopoietic cords or islands of developing blood cells
    • At higher magnification: • Flattened nuclei of sinusoidal endothelial cells can be distinguished • Variety of densely packed hemopoietic cells in the cords between the sinusoids and adipocytes

    Thymus

    • Vascularized connective tissue capsule • Extends septa into paranchyme, dividing the organ into many incompletely lobules
    • Cortex: • Composed of newly arrived lymphoblasts, macrophages, and thymic epithelial cells (TECs) • TECs have both epithelial and reticular cell characteristics • Divided into three groups (layers)
    • Medulla: • Contains fewer and larger, mature lymphocytes • Three related types of medullary TECs form a boundary layer, cytoreticulum, and Hassall corpuscles

    Blood-Thymus Barrier

    • Education of T-cells must occur in a controlled environment where antigens are only presented by epithelial reticular cells
    • The blood-thymus barrier ensures that no other cells or free antigens are present
    • Consists of: • Blood capillary wall (endothelial cells, endothelial cell basal laminae, pericytes) • Perivascular connective tissue (type III collagen, macrophages) • Epithelioreticular cell layer (basal lamina of the epithelial reticular cells, epithelial reticular cells)

    Lymph Nodes

    • Bean-shaped, encapsulated structures • Approximately 400-450 lymph nodes • Three major regions within each lymph node:
      • Outer cortex containing nodules
      • Deeper extension of cortex called the paracortex, which lacks nodules
      • Medulla with prominent draining sinusoids adjacent to the hilum

    Lymphatic Circulation through a Lymph Node

    • Lymph nodes filter lymph • Afferent lymphatic vessels drain lymph into the Subcapsular Sinus • Lymph then passes to the Trabecular sinuses • From there, the lymph goes to the Medullary sinuses • Lymphocytes and macrophages pass easily between these sinuses and the tissue of the lymph node

    Blood Circulation through a Lymph Node

    • Blood enters through an artery at the hilus • Arterioles branch from hilar artery to feed into capillary beds • Capillary beds are drained by high endothelial venules (HEVs) • HEVs drain into hilar vein • HEVs are sites where lymphocytes can leave the bloodstream to enter the lymph node tissue bed

    Spleen

    • Functions: • Filters the blood • Destroys old red blood cells • Serves as an immune organ • Divided into Red Pulp (RBC/hemoglobin recycling) and White Pulp (responsible for immune functions)

    Splenic Circulation

    • Blood enters via splenic artery at hilus • Splenic artery branches into trabecular arteries (which travel within connective tissue trabeculae) • Trabecular arteries give off branches known as central arteries which leave the trabecula and enter the substance of the spleen (covered by a peri-arterial lymphatic sheath) • Central arteries branch into penicillar arterioles that piece through the lymphatic sheath and spill into splenic cords • Blood percolates through splenic cords and across walls of splenic sinuses • Splenic sinuses drain into pulp veins • Pulp veins drain into trabecular veins • Trabecular veins drain into splenic vein at the hilus

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    Learn to identify neutrophils in blood smears by their multilobulated nuclei and other distinct features. Discover how these dynamic cells are also known as polymorphonuclear leukocytes or PMNs.

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