Histology and Its methods of study 1.pptx

Introduction to histology and its methods of study.

1. Introduction to Histology & Its Methods of Study

2. Histology Histology is the study of the tissues of the body and how these tissues are arranged to constitute organs. This subject involves all aspects of tissue biology, with the focus on how cells’ structure and arrangement optimize functions specific to each organ.

3. History The term histology was coined in 1819 by Karl Mayer, who combined the two Greek words histos (tissues) and logos (study). The idea that organs were composed of tissues wasn’t truly understood until the late 1700s when Marie-François Xavier Bichat introduced the term “tissue” to the medical lexicon and proposed that tissue within an organ may be impaired without the entire organ failing. Histological staining also dates to the 1700s.

4. History Marcello Malpighi (10 March 1628 – 30 November 1694) “Founder of microscopical anatomy, histology & Father of physiology and embryology”

5. History

6. Preparation of tissues for study The most common procedure used in histologic research is the preparation of tissue slices or “sections” that can be examined under a light microscope. As most tissues are too thick for light to pass through, thin translucent sections are cut from them and placed on glass slides for microscopic examination. The ideal microscopic preparation is preserved so that the tissue on the slide has the same structural features it had in the body

7. Steps in tissue preparation Fixation : Small pieces of tissue are placed in solutions of chemicals that cross-link proteins and inactivate degradative enzymes, which preserve cell and tissue structure. Fixative for light microscopy is formalin , a buffered isotonic solution of 37% formaldehyde

8. Steps in tissue preparation Dehydration : The tissue is transferred through a series of increasingly concentrated alcohol solutions, ending in 100%, which removes all water. Clearing : Alcohol is removed in organic solvents in which both alcohol and paraffin are miscible. Infiltration : The tissue is then placed in melted paraffin until it becomes completely infiltrated with this substance

9. Steps in tissue preparation Tissue processor Dehydration Clearing Infiltration Formalin Alcohol Xylene Paraffin

10. Steps in tissue preparation Embedding : The paraffin-infiltrated tissue is placed in a small mold with melted paraffin and allowed to harden. Embedding station

11. Steps in tissue preparation Sectioning : The process of cutting tissue into thin slices. Microtome

12. Steps in tissue preparation Staining. Most cells and extracellular material are completely colorless, and to be studied microscopically tissue sections must be stained (dyed). Dyes stain material selectively, often behaving like acidic or basic compounds and forming electrostatic (salt) linkages with ionizable radicals of macromolecules in tissues. Cell components, such as nucleic acids with a net negative charge (anionic), have an affinity for basic dyes and are termed basophilic . Cationic components, such as proteins with many ionized amino groups, stain more readily with acidic dyes and are termed acidophilic.

13. Steps in tissue preparation… Staining Hematoxilin and Eosin H/E

14. Steps in tissue preparation Mounting and labeling . To preserve and support a stained section for light microscopy, it is mounted on a clear glass slide, and covered with a thin glass coverslip and labeled with the information of the tissue.

15. Steps in tissue preparation

16. Steps in tissue preparation

17. Light microscopy Conventional bright-field microscopy and more specialized applications like fluorescence, phase-contrast, confocal, and polarizing microscopy are all based on the interaction of light with tissue components and are used to reveal and study tissue features.

18. Bright-Field Microscopy Stained tissue is examined with ordinary light passing through the preparation . C :\Users\ADMIN\OneDrive\Documents\LEGNA\Histology\Optical parts of a microscope and their functions.docx

19. Fluorescence microscopy Uses UV light, under which only fluorescent molecules are visible, allowing localization of fluorescent probes which can be much more specific than routine stains. Detects microorganisms, lipids, amyloid, elastic fibers.

20. Confocal Microscopy The primary functions of a confocal microscope are to produce a point source of light and reject out-of-focus light, which provides the ability to image deep into tissues with high resolution, and optical sectioning for 3D reconstructions of imaged samples.

21. Phase-Contrast Microscopy Uses a lens system that produces visible images from transparent objects and can be used with living, cultured cells. They allow the examination of cells without fixation or staining. They are prominent tools in all cell culture laboratories.

22. Polarizing Microscopy Polarization contrast is a contrast method to detect birefringence, which is a material characteristic that can be found in minerals, polymers, crystals, pharmaceutical samples, biomedical samples and even botanical samples.

23. Cells Smallest More than 30 millions RBC, brain cells….. Tissues Group of cells organized for common purpose 4 basic types Epithelial Connective Nervous Muscle Organs A group of tissues organized for common purpose. Organ systems A group of organs organized for common purpose . Organism All organ systems organized for a common purpose. Hierarchical organization of living matter

24. Histology……… Looking at slides with purple dots and pink stuff . Hematoxilin eosin stain (H&E) The most widely used stain in histology and pathology . Hematoxilin stains nuclei purple Eosin stains proteins pink

25. Epithelium Forms glandular tissue. Lines the lumen of tubular organs and body cavities. Externally covers the body and organs. Consists of cells anchored to a basement membrane with apical and basal surfaces. No extracellular matrix Avascular Basement membrane anchors epithelium with the underlying connective tissue where the capillaries reside.

26. Epithelium ……. Classification Layers of cells+ Shape of cells+ Specialization = Type of epithelium Simple—one single layer of cells

27. Epithelium……. Classification Layers of cells+ Shape of cells+ Specialization = Type of epithelium Stratified- More than one layer of epithelial cells

28. Epithelium……. Classification Layers of cells+ Shape of cells + Specialization = Type of epithelium Flat/ Squamous

29. Epithelium……. Classification Layers of cells+ Shape of cells + Specialization = Type of epithelium Cuboidal

30. Epithelium……. Classification Layers of cells+ Shape of cells + Specialization = Type of epithelium Columnar

31. Epithelium……. Classification Layers of cells+ Shape of cells+ Specialization = Type of epithelium Cilia…..mover Slender, microscopic, hair-like structures or organelles that extend from the surface of the cell

32. Epithelium……. Classification Layers of cells+ Shape of cells+ Specialization = Type of epithelium Microvilli……Increase absorption surface area Microscopic cellular membrane protrusions

33. Epithelium……. Functions Squamous Functions: Diffusion, Filtration, CO2 O2 Pulmonary Alveoli Capillaries H2O, Na, Cl… Capillaries Glomerulus Liver Lubrication Serous membranes (mesothelium)

34. Epithelium……. Functions

35. Epithelium……. Functions Simple cuboidal epithelium Absorption and secretion

36. Epithelium……. Functions Simple cuboidal epithelium Kidney

37. Epithelium……. Functions Simple columnar epithelium Absorption and secretion (cilia and microvilli) Locations: GI tract, Glands, Airways, Fallopian tubes….

38. Epithelium……. Functions Stratified squamous epithelium Protects underlying tissue from abrasion (some cells have keratin) Skin Esophagus Cervix Vagina Vulva Penis

39. Epithelium……. Functions Transitional (urinary) epithelium Stretches and permit distension of urinary organs Dome-shaped apical layer

40. Epithelium……. Functions Transitional (urinary) epithelium

41. Epithelium……. Functions Pseudostratified ciliated columnar epithelium Secretion (mainly mucous) and propulsion of mucous by cilia. Trachea Bronchi Respiratory epithelium

42. Epithelium……. Functions Respiratory epithelium

43. Connective tissue The four different types of connective tissue derived from the same embryonic layer: Mesoderm Proper Cartilage Bone Blood

44. Connective tissue Posses a small number of cells surrounded by an extracellular matrix.

45. Connective tissue Proper Fibroblasts Primary CT cell, synthetize ECM

46. Connective tissue Proper Adipocytes: fat cells Storage lipids in a single droplet

47. Connective tissue Proper Macrophages: Phagocytize and destroy microorganisms and damaged tissues.

48. Connective tissue Proper Extracellular matrix: Material surrounding cells Ground substance: Amorphous material that fills the space between cells. It holds fluids and function as a sieve through H2O/solutes diffuse between capillaries and cells. Fibers: Collagen: Tough structural protein that provides tensile strength. More than 15 types. Most abundant protein in the body. Elastin: Allows stretch and recoil

49. Connective tissue Proper. Types

50. Connective tissue Cartilage

51. Connective tissue Bone

52. Connective tissue Bone

53. Connective tissue Blood

54. Connective tissue

55. Muscle tissue Contractile type of cell Three types: Skeletal , Cardiac and Smooth muscle Voluntary Long muscle fibers, striated and multinucleated

56. Muscle tissue…… Skeletal

57. Muscle tissue..... Skeletal Compartmentalized by sleeves of connective tissue

58. Muscle tissue…….. Skeletal Located: Primarily within muscles that attached to bones.

59. Muscle tissue…… Cardiac Involuntary, straited, with intercalated discs Located in the wall of the heart (myocardium)

60. Muscle tissue…… Smooth Involuntary, non-striated Located in the wall of most hollow organs (Stomach, bladder, Blood vessels)

61. Nervous tissue Is comprised of cells

62. Nervous tissue….. Neurons Send and receive messages from neurotransmitters , separated by synapses Classified based on their functions Sensory neurons Motor neurons Interneuron

63. Nervous tissue…… Neuroglia Non neuronal cells within CNS and PNS Provide physical and metabolic support to neurons

64. Assignment Study the light microscope parts and their functions.