Histology Lab

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Histology Lab

• Blood and Lymphatics

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BLOOD LABORATORY

• This laboratory is concerned with the
  identification of the cellular components of
  peripheral blood and the bone marrow.Be able to
  distinguish each of the cells of this system and
  recognize their salient features as described in
  the text associated with each of the images.

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• Blood smear-Peripheral. Wrights stain. This is a
  smear of peripheral blood illustrating
  erythrocytes, leukocytes (white blood cells), and
  platelets. Erythrocytes or red blood cells
  comprise the largest cell population or
  peripheral blood. These anucleated cells are
  approximately 7.5u in diameter and number about 5
  million/ul. They are biconcave in shape and thus
  the central part of the cell appears lighter than
  the periphery. Leukocytes number approximately
  7-10,000/ul. They utilize the vascular system for
  transport however, their main functions are
  carried out in connective tissue. Platelets
  number about 250,000/ul.N Neutrophils contain
  lots of membrane-bound granules in their
  cytoplasm, however, with this stain, they stain
  very pale lavender. They tend to have two to five
  nuclear lobes each connected by thin strands of
  chromatin. Neutrophils comprise about 70 of the
  leukocytes.E Eosinophils have bi-lobed nuclei.
  The cytoplasm of these cells is filled with
  membrane-bound granules that stain pink. The
  granules tend to be about the same in size and
  shape. Eosinophils comprise about 1-3 of the
  leukocytes.B Basophils have granules scattered
  about the cytoplasm. The granules are somewhat
  irregular in size and shape and tend to mask out
  the nucleus. Basophils comprise about 0.5-1 of
  the leukocytes.L Lymphocytes are about the same
  size as the erythrocytes (red blood cells). The
  darkly staining nucleus almost fills the entire
  cell. There is a small rim of basophilic
  cytoplasm. Lymphocytes comprise about 20-30 of
  the leukocytes.M Monocytes tend to be 2-3 times
  the size of erythrocytes. They have
  light-staining nuclei that are somewhat irregular
  in shape. Monocytes comprise about 3-8 of the
  leukocytes.P Platelets are small fragments of
  cytoplasm surrounded by plasmalemma. They bud off
  from megakaryocytes located in the bone marrow.

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• Proerythroblast. The central cell in this image
  is a Proerythroblast (red arrow), one of the
  first identifiable stages of red cell
  development. The cytoplasm stains basophilic due
  to a number of ribosomes that will be involved in
  the production of hemoglobin. The nucleus, which
  occupies about 80 of the cell volume, contains
  fine chromatin and 1-2 nucleoli (yellow arrows).
  Note that with Wrights stain, the nucleoli do
  not stain dark as with H E. Wrights stain
  colors DNA but not RNA. As a result, the nucleoli
  appears light with a thin rim of dark-staining
  material around it (this represents the
  nucleolar-associated DNA of the acrocentric
  chromosomes. The black arrow is indicating a
  polychromatophilic erythroblast (a later stage of
  development).

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• Proerythroblast. The central cell is another
  example of a proerythroblast (red arrow). The
  yellow arrows are pointing to nucleoli. Note the
  text of the previous image for a description of
  this developmental stage. The green arrow is
  indicating a polychromtophilic erythroblast and
  the black arrow is pointing to an eosinophilic
  myelocyte, a developmental stage of one of the
  leukocytes.

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• Basophilic Erythroblast. Proerythroblasts undergo
  several mitoses some of the daughter cells
  differentiate into the next stage of development,
  Basophilic Erythroblasts (red arrows). The
  cytoplasm is usually more basophilic than that of
  proerythroblasts due to larger numbers of
  ribosomes. Nucleoli are absent and the chromatin
  appears darker than the previous stage. Note that
  the nucleus still occupies are large portion of
  the cell volume. The black arrow is indicating a
  polychromatophilic erythroblast.

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• Polychromatophilic Erythroblast. The black arrows
  are pointing to basophilic erythroblasts. These
  cells undergo several mitoses some of the
  daughter cells differentiate into the next stage
  of development, Polychromatophilic Erythroblast
  (red arrow). Note that the cytoplasm appears
  somewhat gray. This is due the presence of
  hemoglobin that is being produced by the
  ribosomes. There are fewer ribosomes at this
  stage than previous stages, thus less blue and
  more pink gray color. Note also that the
  nucleus is denser than previous stages.

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• Polychromatophilic Erythroblast. Another image of
  a polychromatophilic erythroblast. Note the dense
  nucleus and gray cytoplasm. These cells undergo
  mitoses some of the daughter cells differentiate
  into the next type, the orthochromatophilic
  erythroblast.

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• Orthochromatophilic Erythroblast/ Reticulocyte.
  Orthochromatophilic Erythroblasts (red arrow)
  have a cytoplasmic color that approximates that
  of an erythrocyte. Thus nucleus initially is
  somewhat centrally located and very dense. It
  then moves to an eccentric position, becomes
  pyncnotic and then is extruded. Once the nucleus
  is lost, the cell is termed a Reticulocyte (blue
  arrow). It is not yet biconcave and thus lacks a
  central halo. It still contains a scant amount of
  RNA and thus stains positive with an RNA stain.
  After about 24 hours, all RNA is gone and the
  cell assumes a biconcave shape and is then termed
  an erythrocyte (black arrow). About 1 of the
  circulating red blood cells are reticulocytes.

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• Myeloblast. The Myeloblast (red arrow) is one of
  the first recognizable stages in the development
  of granulocytes. The nucleus occupies about
  50-60 of the cell volume. It has a fine
  chromatin pattern and 1 or 2 nucleoli (yellow
  arrows). No granules are present at this stage
  thus one cannot determine whether this cell will
  develop into a neutrophil, eosinophil, or
  basophil. The cytoplasm is basophilic due to the
  content of ribosomes. Present in this image are
  two orthochromatophilic erythroblasts (black
  arrows) and a reticulocyte (blue arrow). These
  cells undergo mitoses some of the daughter cells
  differentiate into the next type, the
  promyelocyte.

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• Promyelocyte. The characteristic feature of this
  stage is the presence of primary or azurophilic
  granules in the basophilic cytoplasm. One is
  still unable to determine whether this cell will
  develop into a neutrophil, eosinophil, or
  basophil. Like the myeloblast, the nucleus has a
  fine chromatin pattern and 1 or 2 nucleoli
  (yellow arrows). The cytoplasm is basophilic. Can
  you name the cell indicated by the black
  pointer??

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• Promyelocyte. This is another image of a
  promyelocyte. The green arrows are pointing to
  the azurophilic granules the yellow arrow to a
  nucleolus. This cell undergoes mitoses some of
  the daughter cells will differentiate into the
  next stage, a myelocyte.

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• Neutrophilic Myelocyte. An early stage of
  Myelocyte development is the production of
  secondary granules. The staining characteristic
  of these granules allows the identification of
  the cell as a neutrophilic myelocyte,
  eosinophilic myelocyte, or basophilic myelocyte.
  The central cell indicated by the green arrow is
  a neutrophilic myelocyte. The yellow arrow is
  pointing a light-staining area of the cell
  representing the Golgi apparatus producing
  neutrophilic granules. As the myelocyte becomes
  more differentiated, the secondary granules
  become more numerous, masking the azurophilic
  granules. The cell becomes somewhat smaller and
  the chromatin denser. Nucleoli are absent at this
  stage. The red arrows are pointing to three
  neutrophilic myelocytes.

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• Neutrophilic Myelocyte. Two neutrophilic
  myelocytes are illustrated in this image. A few
  azurophilic granules can be visualized in the
  cytoplasm of the left cell. Note that the nucleus
  of the cell indicated by the black pointer is
  just beginning to segment.

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• Neutrophilic Myelocyte. A neutrophilic myelocyte
  is illustrated in this image. Note the
  azurophilic granules in the cytoplasm and the
  dense chromatin of the nucleus. The black arrow
  indicates a neutrophilic band cell. Myelocytes
  undergo mitoses and give rise to more myelocytes
  some of which will differentiate into
  metamyelocytes. Myelocytes are the last stage to
  undergo cell division.

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• Neutrophilic Metamyelocyte. The identification of
  the granulocytes beyond the myelocyte stage is
  based on nuclear morphology. The nucleus indents
  on one side and eventually becomes band shaped.
  Illustrated in this image is a neutrophilic
  metamyelocyte. This cell stage is identified as
  having nuclear indentation (black arrow) less
  than 50.

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• Neutrophilic Bands. As the nuclear indentation
  progresses, the nucleus becomes horseshoe or
  band-shaped (red arrows). Band cells are
  occasionally found in the peripheral blood.

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• Early Neutrophil. The early sign of maturation is
  nuclear segmentation (black arrow). This is a
  process whereby the nucleus segments into two or
  more lobes, each connected by strands of
  chromatin. Neutrophils may contain 2-5 lobes
  whereas eosinophils are normally bi-lobed.

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• Neutrophils. These are two images of neutrophils,
  each having three nuclear lobes. The left
  neutrophil has a small amount of chromatin
  projecting off one of the lobes (black arrow).
  This known as a Barr body (which are common in
  females) and represents an inactive X-chromosome.

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• Neutrophils. This is an image of two neutrophils,
  each having four nuclear lobes.

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• Megakaryoblasts. Megakaryoblasts are located in
  the bone marrow near the sinusoids. They develop
  into megakaryocytes that function in the
  production of platelets. This process involves
  the budding of small portions of cytoplasm
  surrounded by a plasmalemma. Megakaryoblasts are
  large cells, measuring about 30 um in diameter.
  During the period of differentiation of a
  megakaryocyte, the cytoplasm increases in amount
  and the nuclear DNA undergoes several
  replications. The end result is a large cell,
  measuring about 70-100 um, with a multi-lobulated
  nucleus.

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• Megakaryocytes

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LYMPHATIC SYSTEM LABORATORY

• This laboratory is concerned with the
  identification of the structural components of
  lymphatic tissue. The main cellular components of
  lymphatic tissue include lymphocytes, plasma
  cells, macrophages, and phagocytic reticular
  cells.Be able to distinguish each of the
  tissues/organs of this system and recognize their
  salient features as described in the text
  associated with each of the images.

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• Diffuse Lymphatic Tissue. This is a section of
  the ileum illustrating diffuse lymphatic tissue.
  Diffuse lymphatic tissue may be classified as
  either loose or dense. Loose diffuse lymphatic
  tissue consists of lymphocytes that are scattered
  about within connective tissue (red arrows). When
  large numbers of lymphocytes are very closely
  associated with each other, the tissue is
  classified as dense diffuse lymphatic tissue
  (yellow arrow).

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• Diffuse Lymphatic Tissue. This is a section of
  the jejunum illustrating a dense diffuse
  lymphatic tissue consisting primarily of large
  numbers of closely associated lymphocytes giving
  it a dark appearance (red arrows).

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• Nodular lymphatic tissue. This is a section of
  appendix, which typically contains large numbers
  of lymphatic nodules (red arrows). These nodules
  are classified as secondary due to the presence
  of germinal centers (yellow arrows). The green
  arrow is indicating a patch of dense diffuse
  lymphatic tissue.

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• Palatine Tonsil. This is a section of palatine
  tonsil containing several secondary nodules
  (yellow arrows) embedded in dense diffuse
  lymphatic tissue (orange arrow). The surface of
  the tonsil is lined by a non-keratinized
  stratified squamous epithelium (red arrow). A
  small amount of connective tissue lies just deep
  to the epithelium.

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• Palatine Tonsil. This is a higher magnification
  of the previous image illustrating the epithelial
  lining (red arrow). A small amount of connective
  tissue lies just deep to the epithelium (green
  arrow). Nodular lymphatic tissue is located deep
  to the connective tissue.

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• Palatine Tonsil. This image illustrates one of
  several crypts typically found associated with
  palatine tonsil (red arrow). Debris can collect
  in these crypts, as there is no effective
  flushing mechanism.

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• Palatine Tonsil - Capsule. Palatine tonsils are
  classified (along with pharyngeal and lingual
  tonsils) as partially encapsulated lymphatic
  organs. Dense connective tissue forms a band
  (partial capsule) around the deep portion of the
  tonsil (green line).

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• Lymph Node. Lymph nodes are surrounded by a dense
  connective tissue capsule (black arrows). Deep to
  the capsule is the cortex of the lymph node (C).
  This area contains lymphatic nodules (red arrows)
  embedded in a dense diffuse lymphatic tissue. The
  central portion of a lymph node is called the
  medulla (M) and contains cords of lymphatic
  tissue, but no nodules. The two areas are
  separated by the red line in this illustration.

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• Lymph Node-Medulla. This is a high magnification
  of the medullary portion of a lymph node. Red
  arrows are indicating medullary sinuses
  containing lymph coming from the cortical region
  on its way to the hilus of the node where it will
  enter efferent lymphatic vessels.

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• Lymph Node-Cortex. This is a high magnification
  of the outer portion of a lymph node. The green
  arrow is indicating the dense connective capsule.
  Projecting off of the capsule are bands of
  connective tissue, termed trabeculae (blue arrow)
  that penetrate the cortex. Just deep to the
  capsule is the subcapsular sinus (red arrow)
  containing lymph that entered this region via
  afferent lymphatic vessels. The lymph may
  percolate through the nodular lymphatic tissue to
  the medulla or pass to the medulla via trabecular
  sinuses (yellow arrow) surrounding the
  trabeculae.

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• Lymph Node-Cortex. This is a higher magnification
  of the outer portion of a lymph node illustrating
  the capsule (green arrow), subcapsular sinus (red
  arrow), and trabecular sinus (yellow arrow). The
  cortical region of a secondary nodule, containing
  small lymphocytes, is separated from the germinal
  center (GC) by the red line. The germinal center
  contains small and large lymphocytes,
  macrophages, and plasma cells.

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• Lymph Node-Afferent Vessels. Lymph enters the
  subcapsular sinuses via afferent lymphatic
  vessels (red arrow). The lymph then passes to the
  medullary sinuses via the trabecular sinuses
  (fast route) or by percolating through the
  cortical lymphatic tissue (slow route).

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• Spleen. The image on the left is a low
  magnification of a spleen. A capsule of dense
  connective tissue and smooth muscle surrounds
  this organ. The bulk of the spleen contains red
  pulp (black arrows), which consists of cords of
  lymphatic tissue among blood vascular sinuses.
  The white pulp (encircled in red) consists of
  dense collections of lymphocytes surrounding
  central arteries (yellow arrows). The image on
  the right is a high magnification of the red pulp
  illustrating several splenic cords or cords of
  Billroth (red arrows).

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• Spleen. This is high magnification of the splenic
  capsule (green arrow). This structure consists of
  dense connective tissue and smooth muscle.
  Numerous trabeculae (black arrow) project off of
  the capsule and penetrate the substance of the
  organ. White pulp is separated from the red pulp
  by red lines. Yellow arrows point to the central
  arteries.

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• Spleen. This is a high magnification of the
  parenchyma of the spleen. Numerous areas of white
  pulp are separated from the red pulp by red
  lines.

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• Spleen-White Pulp. This is a high magnification
  of white pulp (encircled in red). A central
  artery is indicated by a black arrow. The red
  pulp contains numerous blood vascular sinuses.

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• Thymus. The thymus is surrounded by a capsule of
  connective tissue (not shown). Projections from
  the capsule separate the organ into lobes and
  lobules. The central portion of a lobule, the
  medulla (M), is light staining and contains small
  and large lymphocytes. The outer part of the
  lobule is dark staining and termed the cortex and
  contains small lymphocytes. The thymus lacks
  lymphatic nodules. Stroma is composed of
  epithelial reticular cells.

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• Thymus. The thymus is surrounded by a capsule of
  connective tissue (black arrow). Projections from
  the capsule separate the organ into lobes and
  lobules (green arrows). The central portion of a
  lobule, the medulla (M), is light staining and
  contains small and large lymphocytes. The outer
  part of the lobule is dark staining and termed
  the cortex and contains small lymphocytes. The
  thymus lacks lymphatic nodules. The stroma is
  composed of epithelial reticular cells.

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• Thymus. This image is a high magnification of the
  approximate separation of the medulla and the
  cortex (red line). The medulla contains unique
  structures termed Hassalls (thymic) corpuscles
  (red arrows). These whorl-shaped structures,
  which increase with age, consist of concentric
  layers of epithelial reticular cells.

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• Thymus-Medulla. The image on the left is a high
  magnification of a thymic medulla illustrating
  Hassalls corpuscles (red arrows). The image on
  the right is a high magnification of a Hassalls
  corpuscle (yellow arrows) demonstrating the
  concentric arrangement of the epithelial
  reticular cells. The central portion of the
  corpuscle may contain keratin and occasionally,
  calcification.

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Welcome back! I hope you had a great summer
break and that your mind will allow you to get
back into studying 26 hours a day.
Enjoy Histo and watch your summer break fade away