Clinical Pathology Exam 1

Clinical pathology

evaluates disease in animals using lab data collected during analysis of blood, urine, body fluids, and tissue aspirates

Total magnification

the product of the objective lens magnification and the magnification of the eyepiece lens

what is evaluated in a CBC?

• Total protein (plasma protein, total solids)

• WBC Count ( # WBC/mm3 or µL)

• RBC Count ( # RBC/mm3 or µL)

• Hemoglobin (Hgb, Hb); carries Oxygen

• Hematocrit (Hct or Packed Cell volume /PCV)

• Blood smear evaluation

• RBC indices (MCV, MCH, MCHC)

What is another term for Hematocrit?

Packed cell volume or PCV

What tests are included in a RBC Indices?

MCV, MCH, MCHC

What three values measure RBC mass?

RBC count

Hemoglobin

Hematocrit

What does MCV stand for?

Mean corpuscular (cell) volume

What does MCH stand for?

Mean corpuscular (cell) hemoglobin

What does MCHC stand for?

Mean corpuscular hemoglobin concentration

MCV and units

the size or average “volume” of the red blood cell; Volume units - femtoliters (fl)

MCH and units

Amount of Hb (weight, mass) in the average RBC; Weight/mass units = picograms (pg)

MCHC and units

Concentration of Hb in the average RBC; Concentration units = g/dl (grams/deciliter)

Clinical chemistry

measuring the chemical components of body fluids, most commonly blood (serum or plasma)

Red top or tiger top tube

Has no anticoagulant, yields serum

Purple top

Contains EDTA, yields plasma, used for CBCs

Green top

Contains Heparin, yields plasma, used for chemistries and CBCs

Blue top

Contains Sodium Citrate, yields plasma, used for specific tests, platelet function tests

What is the difference in fluid between serum and plasma?

Serum does NOT contain fibrinogen or clotting factors; Plasma DOES contain fibrinogen and clotting factors

Cytology

Microscopic evaluation of exfoliated cells (mass, lesion, organ, etc)

Exudate

a mass of cells and fluid that has seeped out of blood vessels or an organ, especially in inflammation

What can be determined by preforming a cytology?

• Classify a process as inflammatory, neoplastic, degenerative, etc

• Identify infectious organisms (bacteria, fungi, etc.)

• Benign vs malignant

Reference interval

an interval of values in which the majority of healthy patient’s lie

How is a reference interval calculated?

calculated from a group or population of healthy, adult animals of a given species for a specific test

What is a reference interval help to do?

identify abnormalities in sick patients

What is the difference between PCV and HCT (hematocrit)?

PCV is measured manually. HCT is calculated

PCV

percentage of whole blood composed of erythrocytes. It provides an accurate estimate of RBC mass

-% of healthy individuals will be outside the reference interval

5

What are the 3 main variables used to choose a reference population?

1. same species

2. clinically healthy

3. age (adult animals older than 1 year old)

What is the formula for finding a reference interval?

Mean +- 2 SD (standard deviations)

What is the desired shape for a reference interval?

bell shaped (gaussian distribution)

Hemacytometer

a manual counting system uses a specialized chamber containing a 9-square grid on both sides; used to manually perform cell counts in various fluids, Manual WBC count, manual platelet count

Mammalian RBCs are:

• Biconcave discs

• Anuclear

Erythrocyte morphology includes:

• size

• shape

• color

• inclusions

What are some characteristics of a canine RBC?

• Largest mammalian erythrocyte

• Uniform

• Large area of central pallor

• Lifespan: 110-120 days

What are some characteristics of a porcine RBC?

• smaller

• little to no central pallor

• lifespan 70-98 days

What three things are being evaluated during a blood smear for a CBC?

1. Differential count (how many of each WBC type is present out of 100 WBCs)

2. Cell morphology (identify and report significant abnormal morphology; RBC, WBC and Platelets)

3. Platelet Number estimate (counted in each field of view then a calculation is preformed)

How is a hemacytometer used?

• Use 40 x objective

• Count cells in all nine large squares

• Count both sides

• Calculate concentration of cells in fluids

What are the characteristics of a feline RBC?

• Smaller

• Variable size

• little to no central pallor

• Fragile Hgb; more susceptible to injury

• Rouleaux morphology common

• Erythrocyte lifespan 65 - 76 days

What are the characteristics of an equine RBC?

• Smaller

• Little to no central pallor

• Rouleaux extremely common

• Erythrocyte lifespan 140 - 150 days

What are the characteristics of a bovine RBC?

• Smaller

• Little to no central pallor

• Erythrocyte lifespan 160 days

What are the characteristics of an Ovine RBC?

• Smaller

• No central pallor

• Lifespan unknown

What are the characteristics of an Caprine RBC?

• Smallest mammalian erythrocyte

• Approximately half the size of canine RBC’s

• No central pallor

• Erythrocyte lifespan 125 days

What are the characteristics of a Camelid RBC?

• Has oval/elliptical shape

• MCHC significantly higher than other species

• Erythrocyte lifespan 60 days

What are the characteristics of an exotic RBC?

• Includes avian, reptilian, amphibian, and fish

• erythrocytes have a nucleus

• All exotic cells are special

What do RBC indices help determine?

They help determine what type of anemia a patient has.

Formula for MCH

Hemoglobin (g/dL) X 10/ RBC Count (millions/ ul) = MCH (pg)

Formula for MCV

Hematocrit (%) x 10/ RBC Count (millions/ ul) = MCV (fL)

Formula for MCHC

Hemoglobin (g/dL) X 100/ Hematocrit (%)

What are the three major types of blood cells and their functions

1. RBC; Oxygen to tissues

2. WBC; Defense/Immunity

3. Platelets; Hemostasis

What are the mononuclear leukocytes?

Lymphocytes and monocytes

What are the polymorphonuclear leukocytes?

Neutrophils, eosinophils, Basophils

Production of blood cells

Hematopoiesis

What are the agranular leukocytes?

lymphocytes and monocytes

What are the polymorphonuclear WBCs?

Neutrophils, eosinophils, basophils

the fluid part of blood contains —- and —-

nutrients and signal proteins

Production of leukocytes/ WBCs

Myelopoiesis

Production of granulocytes

granulopoiesis

Production of platelets

Thrombopoiesis

Red marrow

active hematopoiesis

Yellow marrow

Adipose tissue

“Medullary” Hematopoiesis

in the medulla of Bone (bone marrow)

“Extramedullary” Hematopoiesis

other tissues than bone marrow

What are the most common sites of “extramedullary” hematopoiesis in order?

1. Spleen

2. Liver

3. Lymph node

What are the two functional compartments of Bone marrow?

Intravascular space and extravascular space

Bone marrow sites for active hematopoiesis in young animals?

involves all bones, marrow is densely cellular (RED) throughout body

Bone marrow sites for active hematopoiesis in mature animals

Flat bone (hip/ilium), irregular bones, ends of long bones

-long bones: end have red marrow, middle is yellow

What do the pores in the intravascular space of bone marrow do?

regulate entry of mature hematopoietic cells into the blood stream

What is the importance of fat and stromal cells in the microenvironment that control hematopoiesis?

they are important regulars; stromal cells contribute to barrier with vascular space

Percentage of hematopoietic cells tends to —-with age

decrease

What two things make up the extravascular space in bone marrow?

1. Hematopoietic cells

2. Fat, stroma (connective tissue)

What are some features of stem cells?

• Self replicating

• Pluripotent = can produce multiple types of cells

• Signal proteins determine the cell type produced

• Morphologically indistinct

Committed Progenitor cells

• Cannot produce all cell types (committed to a specific cell line)

• Morphologically indistinct

• Can be identified using surface markers in cell cultures

Earliest identified precursor in each cell line is a —-

blast

Rubriblast

earliest identified precursor of a RBC

Pro-megakaryocyte

earliest identifiable precursor of a platelet

Myeloblast

earliest identifiable precursor of a neutrophil

Monoblast

earliest identifiable precursor of a monocyte

What is an essential part of the hemoglobin molecule of RBCs

Iron

About —-% of total body iron is found in Hb

60-65

What are the three different classes of signal proteins

1. Cytokines

2. Interleukins (e.g.IL-3)

3. Colony Stimulating Factors (e.g. G-CSF)

What are the important signal proteins in Hematopoiesis? (for RBCs, WBCs, and platelets)

a. Erythrocytes - erythropoietin

b. White cells - G-CSF, GM - CSF (G = granulocyte, gm - granulocyte-monocyte)

c. Platelets - Thrombopoietin

Basophilia

blueness

Why is their decreasing basophilia during hematopoietic cell maturation?

decreasing RNA and protein synthesis

What are some general features of the morphology of hematopoietic cell maturation?

1. Decreasing nulear: cytoplasmic ratio

2. Decreasing cell size

3. Nuclear changes - loss of nucleoli, more dark and dense chromatin, changes in nuclear shape-mainly in granulocytes

4. Cytoplasmic changes - decreasing basophilia, RBCs only: increasing pink/orange color

Why do RBCs get more pink/orange in color during maturation?

Hb synthesis

It takes roughly — days to produce new RBCs under normal circumstances (Rubriblast → RBC)

5 days

Production for RbCs may be decreased to —days if there is strong stimulation. What is that stimulation?

3-4 days; sudden anemia

hypoxia

decreased oxygen in tissues

With onset of anemia it will take —- days before increased polychromasia occurs in blood

3-5 days

Extravascular destruction

When circulating RBCs become old, they are removed from the circulation by macrophages before being destroyed

What are the 3 main sites for extravascular destruction?

spleen, liver, and bone marrow

Hemoglobin is broken down into —- and ——

Heme, globin

After hemoglobin is broken down what happens to globin molecules?

The globin molecules are further digested into amino acids, which can be re-utilized to make new to make new proteins

How is unconjugated bilirubin created?

A molecule of heme has the iron removed and is then broken down into unconjugated bilirubin by the macrophages.

Where does unconjugated bilirubin convert to conjugated bilirubin?

In the liver and is later excreted from the liver through the bile duct into the intestines

What happens to the iron after it is removed from the heme molecule?

The iron is either used right away to make new RBCs or is converted into a storage form (hemosiderin ) within macrophages until needed

Hemolysis

premature destruction of RBCs

The amount of iron in storage influences —— of new iron.

intestinal absorption

Low iron stores cause —- absorption; high iron stores —— absorption

increased; inhibit

Why is it essential for iron to be added to hemoglobin?

it is essential for oxygen binding and transport by the hemoglobin