Histology

• Histology


  The branch of biology and medicine concerned with the study of the microscopic structure of tissues and organs
• Histology


  • It examines how cells and tissue systems are organized and how they work together to support the functions of the body
• Pharmacy students learning histology


  It provides a deep understanding of how drugs interact with cells and tissues, influencing their therapeutic effects and side effects
• Stages of human life

  • Prenatal period (Before birth)
  • Postnatal period (After birth)
• Subdivisions of Prenatal period

  • Pre-embryonic period
  • Embryonic period
  • Fetal period
• Pre-embryonic period


  Extends from conception (fertilization) and formation of the zygote to the end of the second week of intrauterine life
• Embryonic period


  Extends from beginning of the third week to the end of the eight week of intrauterine life. The living organism in this period is called the Embryo. This period is also known as the organogenetic period (All organs and systems are formed in this period)
• Fetal period


  Extends from beginning of the ninth week (57th day) to birth. The human being in this period is called the Fetus
• Teratogens


  Substances that may cause birth defects via a toxic effect on an embryo or fetus
• Major teratogens


  • Alcohol
  • Nicotine
  • Some drugs
  • Radiation
  • Pathogens
• Teratology


  The branch of science that studies the cause, mechanisms, and patterns of abnormal development
• "Biggest man-made medical disaster ever – flipper babies": 'In the late 1950s and early 1960s, the use of thalidomide in 46 countries by women who were pregnant or who subsequently became pregnant resulted in the "biggest man-made medical disaster ever," with more than 10,000 children born with a range of severe deformities, such as phocomelia, as well as thousands of miscarriages.'
• Postnatal periods


  • Infancy period
  • Childhood period
  • Puberty period
  • Adolescence period
  • Adulthood period
  • Senility-Geriatry
• Hierarchy of life - Level I

  • Chemical and molecular level (the smallest unit): Atoms
  • Inorganic molecules
  • Organic molecules
  • Monomers
  • Polymers (biomolecules)
• Hierarchy of life - Level II

  • Organelle and Cell level: Cell membrane
  • Ribosomes
  • Mitochondrion
  • Endoplasmic reticulum
  • Golgi
  • Lysosomes
  • Nucleus
  • RBCs
  • Muscle cells
  • Macrophages and leukocytes
  • Nerve cells
  • Sperm and oocyte
• Hierarchy of life - Level III

  • Tissue level: Epithelial tissue
  • Connective tissue
  • Muscular tissue
  • Nervous tissue
• Hierarchy of life - Level IV

  • Organ level
• Hierarchy of life - Level V

  • Organ System level
• Structural parts of the microscope

  • Head
  • Arm
  • Base
• Optical parts of the microscope

  • Eyepiece
  • Eyepiece tube
  • Diopter Adjustment
  • Nose piece
  • Objective lenses
  • Fine Adjustment Knob
  • Coarse Adjustment Knob
  • Stage
  • Stage Control Knobs
  • Aperture
  • Microscopic illuminator
  • Condenser
  • Diaphragm
• Tissue processing


  Histological techniques and pharmacists - why is it important?
• Pharmacists


  • Their work is not always associated with working in a pharmacy
  • They can work as scientists, researching how individual drugs interact with tissues and organs
  • Knowledge of histological techniques is necessary for this
• Questions pharmacists may encounter

  • Doctor took a biopsy of my wife's breast, we wonder if it's cancer or not, we haven't been able to sleep for days
  • What will they do to this biopsy piece, how many days will we get the result, can we trust the result?
• Learning Outcomes


  • Definition and importance of tissue processing to accurate histopathological diagnosis
  • Steps that are performed on biological tissue samples in order to prepare them for microscopic examination
  • Basic differences of Routine histopathological techniques, Histochemical Techniques and Immunohistochemical Techniques (IHC)
• Tissue Processing


  • Tissues from the body taken for diagnosis of disease processes must be processed in the histology laboratory to produce microscopic slides that are viewed under the microscope by pathologists
  • Including the techniques for processing the tissues, whether biopsies, larger specimens removed at surgery, or tissues from autopsy
  • The persons who do the tissue processing and make the glass microscopic slides are histotechnologists
• Biopsy


  A small piece of an organ is removed to find out if it is a benign, innocent tumor or cancer (malignant)
• Biopsy example


  • 30 years old woman, she has a lump on her breast
  • The doctor examines her and says she needs to take a small piece of the breast (biopsy) and send it to the lab for pathological examination
• • A patient can be considered as a cancer although she is a healthy person and even might lead to removal of that organ
  • Or we might come across with the controversy situation, where the patient has cancer but this was not diagnosed due to errors in sample preparation and treatment can not be started on time
  • That is why, each step that I am going to mention is very important
  • Mistakes done during any of the steps might lead to a wrong diagnosis
• Removal of Tissue (A small piece of organ)

  1. First step is to remove the tissue (a piece of organ) from the body

  2. The process of removing a small piece from an organ is called biopsy

  3. Biopsy samples are classified into three categories: Fine needle biopsy, Endoscopic biopsy, Excisional biopsy
• Fine needle biopsy


  Thyroid, liver, spleen, kidney, mammary glands, salivary glands and all other organs owing a solid structure can be subjected for needle biopsy
• Endoscopic biopsy


  • Removal of tissue with the help gastroscopic, colonoscopic and bronchoscopic techniques
  • The instrument used for this technique includes a light and a camera as well as a knife on the very end which enable both monitorizing and removal of a tissue at the same time
• Excisional biopsy


  • Entire lesion or entire affected area is removed
  • For instance, the dermatologist needs to completely remove the lesion in order to examine
• Biopsy types


  • Needle Biopsy
  • Endoscopic Biopsy
  • Excisional Biopsy
• Tissue processing steps


  1. Tissue

  2. Fixation

  3. Dehydration

  4. Clearing

  5. Infiltration

  6. Embedding (wax or plastic)

  7. Sectioning

  8. Section on slide ready to be stained

  9. Stained sections on slide
• Autolysis


  The destruction of cells or tissues by their own enzymes, lysosomal self-digestion
• Infection


  Pathogenic microorganisms such as bacteria, fungi, viruses
• Fixation of Tissue


  • The purpose is to avoid lysosomal autolysis (self-digestion), protect the tissue from bacterial infection, and preserve from decay
  • It is like taking a photograph of the last and closest to the real state of the cells that make up the tissue
• Chemical fixation methods


  • Some chemical solutions are used fix the samples, this method is called immersion methods
  • Specimens should be immersed in chemical fixative solution immediately after they are removed from the body
  • Most commonly used chemical fixative is 10% Neutral Buffered Formalin, a aqueous solution of formaldehyde
• Frozen Method


  • This method is carried out during a surgical operation
  • Surgeon removes a piece of suspicious sample and places into liquid nitrogen tank and send it to pathologist
  • Pathologist is going to slice the frozen sample and stains immediately to get the result in a very short period of time
• Dehydration


  • 70% of human body is composed of water
  • Best way to dehydrate is to wash with ethyl alcohol, which removes water from tissues solidifies to allow thin sections to be cut
  • Samples are transferred through baths of progressively more concentrated ethanol (70-80-90 and 100 %) to remove the water