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?

Thin strands Signup and view all the answers

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

Their multilobulated nuclei Signup and view all the answers

What is a distinctive feature of the cytoplasm of eosinophils?

Abundant coarse eosinophilic granules Signup and view all the answers

What is a characteristic of the nucleus of basophils?

Two or three irregular lobes Signup and view all the answers

What is a function of monocytes?

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

What is a characteristic of platelets?

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

What is a feature of lymphocytes?

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

Which of the following lymphoid organs is classified as primary?

Thymus Signup and view all the answers

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

They are all classified as secondary lymphoid organs Signup and view all the answers

Bone marrow is classified as which type of lymphoid organ?

Primary lymphoid organ Signup and view all the answers

Which of the following is NOT a lymphoid organ?

Liver Signup and view all the answers

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

Participating in the immune response Signup and view all the answers

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

Trabeculae of cancellous bone Signup and view all the answers

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

Hemopoietic cells and sinusoidal endothelial cells Signup and view all the answers

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

Between the sinusoids and adipocytes Signup and view all the answers

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

Identifying the different types of hemopoietic cells Signup and view all the answers

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

To facilitate the exchange of oxygen and nutrients Signup and view all the answers

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

To divide the thymus into many incompletely separated lobules Signup and view all the answers

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

Newly arrived lymphoblasts and macrophages Signup and view all the answers

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

They have both epithelial and reticular characteristics Signup and view all the answers

What is a characteristic of the medulla of the thymus?

It contains fewer and larger, mature lymphocytes Signup and view all the answers

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

Hassall corpuscles Signup and view all the answers

What is a characteristic of the young thymus?

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

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

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

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

Macrophages Signup and view all the answers

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

To present antigens to T-cells during education Signup and view all the answers

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

Type III collagen Signup and view all the answers

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

To support the structure of the epithelial reticular cells Signup and view all the answers

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

400-450 Signup and view all the answers

Which part of the lymph node contains the nodules?

Cortex Signup and view all the answers

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

All of the above Signup and view all the answers

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

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

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

Subcapsular Sinus -> Trabecular sinuses -> Medullary sinuses Signup and view all the answers

What is the primary function of a lymph node?

To filter the blood and serve as an immune organ Signup and view all the answers

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

High endothelial venules (HEVs) Signup and view all the answers

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

To recycle old red blood cells Signup and view all the answers

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

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

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

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

What is the entry point of blood into the spleen?

Splenic artery at the hilus Signup and view all the answers

What is the function of penicillar arterioles?

To piece through the lymphatic sheath and spill into splenic cords Signup and view all the answers

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

Splenic sinuses Signup and view all the answers

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

Splenic vein at the hilus Signup and view all the answers

What surrounds the central arteries in the spleen?

Peri-arterial lymphatic sheath Signup and view all the answers

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

T-cells Signup and view all the answers

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

Lymph nodules Signup and view all the answers

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

To provide a site for T-cell aggregation Signup and view all the answers

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

To remove old red blood cells Signup and view all the answers

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

Periarterial lymphatic sheath Signup and view all the answers

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

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

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

They are involved in the production of antibodies Signup and view all the answers

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

Adaptive immune response Signup and view all the answers

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

White pulp Signup and view all the answers

What is the significance of germinal centers in lymph nodules?

They are involved in the production of antibodies 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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Description

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.

Blood Cells: Identifying Neutrophils

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Questions and Answers

What is a characteristic feature of neutrophils in blood smears?

What is another name for neutrophils?

What happens to the nuclear shape of neutrophils?

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

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

What is a distinctive feature of the cytoplasm of eosinophils?

What is a characteristic of the nucleus of basophils?

What is a function of monocytes?

What is a characteristic of platelets?

What is a feature of lymphocytes?

Which of the following lymphoid organs is classified as primary?

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

Bone marrow is classified as which type of lymphoid organ?

Which of the following is NOT a lymphoid organ?

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

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

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

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

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

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

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

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

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

What is a characteristic of the medulla of the thymus?

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

What is a characteristic of the young thymus?

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

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

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

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

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

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

Which part of the lymph node contains the nodules?

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

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

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

What is the primary function of a lymph node?

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

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

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

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

What is the entry point of blood into the spleen?

What is the function of penicillar arterioles?

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

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

What surrounds the central arteries in the spleen?

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

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

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

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

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

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

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

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

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

What is the significance of germinal centers in lymph nodules?

Study Notes

Neutrophils

Eosinophils

Basophils

Lymphocytes

Monocytes

Platelets

Lymphoid Organs

Primary Lymphoid Organs

Secondary Lymphoid Organs/Tissue

Components of Lymphoid Organs

Bone Marrow Structure

Component Cells

Thymus Structure

Cortex of Thymus

Medulla of Thymus

Characteristics of Young Thymus

Blood-Thymus Barrier

Components of the Blood-Thymus Barrier

Perivascular Connective Tissue