Histology at a Glance E-Book

Michelle Peckham

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Serie: At a Glance
• Sprache: Englisch

Seitenzahl: 202

Veröffentlichungsjahr: 2011

Beschreibung

This brand new title provides a highly illustrated and unambiguous introduction to the science, structure and function of cells, their related pathology, and in particular, helps readers master the basic principles of recognizing features of histological sections.

Histology at a Glance:

• Presents the perfect combination of text and image; key concepts are explained and superbly illustrated
• Provides coverage of all the main body systems and the components of the tissues of these systems
• Features practical information on microscopy, including sample preparation and magnification
• Includes hints and tips to help recognize features in a histological specimen, and overcome common difficulties
• Contains self-assessment questions to help test learning and recognition
• Links to the author’s histological website, which features many more tips and samples, at www.wiley.com/go/histologyataglance

Histology at a Glance is the perfect guide for medical, dentistry and biomedical science students, junior doctors, and is ideal for independent learning programmes in histology.

Leseprobe

CONTENTS

Preface

Acknowledgments

List of abbreviations

1: Preparation of tissues for histology

Sectioning and preparing tissue for staining

Staining

Dehydration and mounting

Other types of sectioning

Sections in electron microscopy

2: Different types of histological stain

Hematoxylin & eosin

Other types of histological stains

Immunocytochemistry

Staining in electron microscopy

3: Sectioning and appearance of sections in the light microscope

Longitudinal and transverse sections

Serial sections

Magnification

4: Light and electron microscopes

The electron microscope

Sectioning for electron microscopy

5: The cell and its components

The plasma membrane

The nucleus

Cellular organelles

Cytoskeleton

6: Cell division

Mitosis

Meiosis

7: Epithelium

Functions of epithelium

Classification of epithelium

Specializations of the epithelium

8: Skeletal muscle

Muscle structure and contraction

Activation of muscle contraction

Muscle damage and repair

9: Cardiac and smooth muscle

Cardiac muscle

Smooth muscle

10: Nerves and supporting cells in the central nervous system

Neurons

Synapses

White and gray matter

Supporting cells in the central nervous system (neuroglia)

11: Nerves and supporting cells in the peripheral nervous system

Nerve ganglia

12: Connective tissue

Types of cell in connective tissue

Extracellular matrix in connective tissue

Types of connective tissue

Basal lamina/basement membrane

13: Blood

Content and functions of blood

Red blood cells

White blood cells

Platelets

14: Hemopoiesis

Multipotent lymphoid stem cells

Multipotent myeloid stem cells

Blood disorders

15: Cartilage

Functions of cartilage

Constituents of cartilage

Two ways that cartilage grows

Types of cartilage

16: Bone

Functions of bone

Types of bone formation

Content of bone

Types of bone

Growth and nourishment of bone

17: Heart

Tunica intima/endocardium

Tunica media/myocardium

Tunica adventitia/epicardium

18: Arteries and arterioles

Elastic arteries

Muscular arteries

Atherosclerosis

19: Capillaries, veins, and venules

Small arteries/arterioles

Capillaries

Types of capillary

Veins

20: Epidermis

Functions of the skin

The epidermis

21: Dermis, hypodermis, and sweat glands

The dermis

The hypodermis

Glands

22: Hair, sebaceous glands, and nails

Hair

Nails

23: Oral tissues (the mouth)

The lip

The mouth

Teeth

The tongue

24: General features and the esophagus

Organization of layers in the gut

Nerve and blood supply to the gut

The esophagus

Cardio-esophageal junction

25: Stomach

Anatomical regions of the stomach

Body of stomach (fundus)

Pyloric region of stomach

26: Small intestine

Mucosa of the duodenum

Mucosa of the jejunum

Other layers of the jejunum

The ileum

27: Large intestine and appendix

The large i ntestine

Human appendix

28: Digestive glands

Salivary glands

The pancreas

Gall bladder

29: Liver

Structure of the I iver

Hepatocytes

30: Trachea

Conducting portion

Basic structure of the conducting portion

Nasal cavities, nasopharynx, and larynx

The trachea

31: Bronchi, bronchioles, and the respiratory portion of the lungs

Tertiary bronchi

Bronchioles

Respiratory portion

32: Renal corpuscle

The kidney

Nephrons

33: Renal tubule

Proximal convoluted tubule

Loop of Henle

Distal convoluted tubule

Collecting tubules

34: Ureter, urethra, and bladder

Ureter

Bladder

Urethra

35: Ovary and oogenesis

The ovary

Oogenesis

36: Female genital tract and mammary glands

The fallopian tube/oviduct

The uterus

The vagina

Mammary glands

37: Testis

The testis

38: Male genital tract

The epididymis

Ductus (vas) deferens

Penis

39: Accessory sex glands

Seminal vesicles

Prostate gland

40: Thyroid, parathyroid, and adrenal glands

Thyroid gland

Parathyroid glands

Adrenal glands

41: Pituitary and pineal glands, and the endocrine pancreas

The pituitary gland

The pineal gland

The endocrine pancreas

42: Thymus and lymph nodes

Primary lymphatic organ

Secondary lymphatic organs

43: Spleen, tonsils, and Peyer's patches

Spleen

Tonsils

Peyer's patches and lymphoid aggregations

44: Eye and ear

The eye

The ear

Self-test questions

Self-test answers

Index

Preface

The aim of this book is to provide a concise overview of histology, particularly for those students who have not studied histology before. The most common complaint that I hear from students studying histology for the first time is that ‘everything looks pink’, which makes it difficult to understand what they are looking at. The images used in each chapter of this book are aimed to help students to understand quickly how tissues are made up from same basic components, and how the organization and appearance of cells in each tissue varies, depending on the function of the tissue.

Acknowledgments

The author would like to thank Tim Lee, Paul Drake, Adele Knibbs, and Steve Paxton at the University of Leeds, for their advice and help in generating some of the images. She would also like to thank her family (James, Helena, Alasdair, and Gabriel) for their support, while putting the book together.

List of abbreviations

ACEangiotensin-converting enzymeACTHadrenocorticotropic hormoneADHantidiuretic hormoneAMLacute myeloid leukemiaA-Vatrio-ventricularCCKcholecystokininCDcluster of differentiation markersCLLchronic lymphocytic leukemiaCNScentral nervous systemDCTdistal convoluted tubuleECMextracellular matrixEELexternal elastic layer (of tunica media)ERendoplasmic reticulumERSexternal root sheath (of hair follicle)FAEfollicle - associated epithelial (cells)FSHfollicle - stimulating hormoneGAGglycosaminoglycanGALTgut - associated lymphoid tissueH&Ehematoxylin & eosinIELinner elastic layer (of tunica intima)IRSinternal root sheath (of hair follicle)LHluteinizing hormoneMALTmucosa - associated lymphoid tissueNMJneuromuscular junctionPALSperiarteriolar lymphoid sheathPASperiodic acid-Schiff (reaction)PCTproximal convoluted tubulePNSperipheral nervous systemPTHparathyroid hormoneRPEretinal pigment epitheliumS-Asino - atrialSRsarcoplasmic reticulumT3tri - iodothyronineT4thyroxineTSHthyroid - stimulating hormoneZFzona fasciculataZGzona glomerulosaZRzona reticularis

1

Preparation of tissues for histology

Histology is the study of tissues and their appearance.

Histos is Greek for ‘web or tissue’, and logia is Greek for ‘branch of learning’.

Anatomists first used the word ‘tissue’ to describe the different textures of parts of the body, as they were being dissected.

Today, histology and pathology (the study of diseased tissues) are routinely used in hospitals and research laboratories to study the organization of tissues and the cells within them.

Sectioning and preparing tissue for staining

To study the structures of cells and their organization within tissues, tissues have to be fixed and ‘sectioned’ (or cut), stained with dyes, and then observed with the light microscope. This is carried out in the following stages (see Fig. 1).

Fixation

A chemical solution containing a fixative at pH 7.0 is added to the tissue (Fig. 1a). The most commonly used fixative is formaldehyde at a concentration of 4%. (Commonly, dilutions are made from a stock of Formalin, i.e., 37% or 40% formaldehyde.) Formaldehyde binds to and cross-links some proteins, and denatures others, but does not interact well with lipids. The overall effect is to harden the tissue and inactivate enzymes, preventing the tissue from degrading.

Dehydration

In order for sections to be cut, the tissue has to be embedded in wax. However, wax is not soluble in water. Therefore, the water in the tissue has to be removed and eventually replaced with a medium in which wax is soluble. This is achieved by, first, sequentially replacing the water with alcohol, placing the tissue in a series of solutions that contain increasing concentrations of alcohol, ending at 100% (Fig. 1b). This process is carried out gradually in order to minimize tissue damage. The tissue must then be ‘cleared’ before it can be embedded in wax.

Clearing

Next, the section is placed in an organic solvent such as xylene or toluene, which replaces the alcohol. Wax is not soluble in alcohol. The clearing agents are so-called, because the tissue often looks completely clear when it is immersed in clearing agent. Finally, the tissue is impregnated with hot wax (Fig. 1b), which is soluble in this type of organic solvent.

Embedding

The tissue is placed in warm paraffin wax in a mould (Fig. 1c). On subsequent cooling, the wax hardens, and tissue slices can now be cut.

Sectioning

Sections (slices) about 10 to 20 microns (µm) thick are cut using a microtome (Fig. 1d).

Mounting

The wax sections are laid onto a glass microscope slide (Fig. 1e).

Staining

To see detail, the components of the tissue have to be stained. However, the stains that are used are all aqueous. Therefore, the wax has to be dissolved and replaced with water (rehydration), for the stains to be able to penetrate the tissue section. The sections are therefore placed in decreasing concentrations of alcohol, ending up at 0% alcohol (water).

A number of different stains can be used but the most common is hematoxylin & eosin (see Chapter 2).

Dehydration and mounting

The stained specimen is once again dehydrated, before placing it into mounting medium dissolved in xylene. Finally, a coverslip is placed on top of the sample to protect it, and the slide can be viewed on the microscope.

Other types of sectioning

Frozen sections

The tissue is rapidly frozen, fixed, and slices cut using a cryostat, before staining.

Semi-thin sections

The tissue is embedded in epoxy or acrylic resin, which has different properties to wax, and allows thinner sections (less than 2 µm) to be cut.

Sections in electron microscopy

See Chapter 4.

2

Different types of histological stain

Cells are colorless and transparent, and it would be difficult to see much detail when observing them using a microscope. Therefore, stains have to be used to make the cells visible.

H&E (hematoxylin & eosin) is the most commonly used stain, but many additional stains are also used, a few of which are described here.

Hematoxylin & eosin

Hematoxylin is derived from the logwood tree (Haematoxylum campechianum), and can only be used as a dye in its oxidized form (hematein). It is a basic dye that binds to acidic structures in cells and stains them a purplish blue. These include:

DNA in the nucleus, in heterochromatin and the nucleolus;RNA in the cytoplasm in ribosomes and rough endoplasmic reticulum;some extracellular materials (e.g., carbohydrates in cartilage).

Eosin is a negatively charged acidic dye. It binds to basic structures in cells and stains them red or pink. These include:

most proteins in the cytoplasm;some extracellular fibers.

Cells in tissue stained with H&E (Fig. 2a) are therefore pink, with a purple nucleus.

Other types of histological stains

Connective tissue stains

Masson’s trichrome method (Fig. 2b) uses three different dyes (hematoxylin, acid fuchsin, and methyl blue), resulting in three colors in the stained section.

Nuclei are stained blue.Cytoplasm, red blood cells (erythrocytes), and keratin are stained bright red.Collagen in the basement membrane, connective tissue, and cartilage are stained green.

A related stain also used to stain connective tissue is Van Gieson.

Giemsa stain

This type of stain is used for bone marrow and blood smears (Fig. 2 c).

Red blood cells are stained pink (they do not have nuclei).White blood cells: cytoplasm is stained pale blue and the nuclei are stained dark blue/purple.

Silver staining (for neurons)

Standard histological stains do not work well on neurons, mainly because their plasma membranes are rich in lipid. Moreover, nuclei are not detected, unless the sections include part of the central nervous system, where the majority of the nuclei are located. However, silver staining (Fig. 2d) does work well. Silver staining stains the nerves and nerve terminals (terminal boutons) black. An alternative method is Golgi-Cox (mercuric chloride, potassium chromate, and dichromate).

Cresyl violet

This stain is used to stain Nissl substance (rough endoplasmic reticulum; ER) in the cell bodies of neurons (Fig. 2e).

Staining carbohydrates and mucins

In the periodic acid-Schiff (PAS) reaction, periodic acid oxidizes carbohydrates and carbohydrate-rich molecules such as glycosaminoglycans, and the Schiff reagent stains the resultant oxidized molecules a deep reddish purple color. In the picture shown here (Fig. 2f), PAS has been combined with the dye, Alcian blue, which stains some mucins (glycosylated proteins) a deep blue color.

Goblet cells, which are rich in carbohydrates and mucin, are stained reddish purple.

Mucin-rich glands towards the bottom of the image shown here are stained a deep blue.

Stains for lipids

Lipid stains include Oil Red O, Sudan black , and Nile blue, and stain myelin sheaths of neurons brownish black (not shown here).

Immunocytochemistry

This technique is becoming much more widely used in histology, as it can detect specific proteins in a section. In this technique, an antibody is used that recognizes a specific antigen on the protein of interest (Fig. 2g). Usually, after incubating the section with the first antibody (primary antibody), a second antibody (secondary antibody) is added, which recognizes the primary antibody (indirect technique). The secondary antibody is commonly labeled using horseradish peroxidase, which turns brown when reacted with a chromogen substrate. This type of staining can be viewed on a normal brightfield microscope. A ‘counterstain’ is used to enable visualization of the overall organization of the cells in the tissue.

Alternatively, the secondary antibody is labeled with a fluorescent dye, in which case the sections have to be viewed using an epifluorescence (or confocal) microscope (see Chapter 4).

Fixing, dehydration, and wax embedding can destroy or mask antigens, which means the antibodies may not work. If this is the case, a number of different ‘antigen retrieval’ methods can be used, which unmask the antigens. These approaches commonly use pressure cookers or microwave ovens. Alternatively, cryosections can be used.

Staining in electron microscopy

See Chapter 4.

5

The cell and its components

The plasma membrane

The plasma membrane (Fig. 5a) is the boundary between the cell and its exterior environment.

It consists of a lipid bilayer, seen by electron microscopy as two parallel electron-dense (dark) lines with a narrow gap between them.

The plasma membrane is only 8-10 nm thick, and cannot be seen by light microscopy without special dyes.

The nucleus

The nucleus (Fig. 5b), about 10 μm in diameter, is enclosed by a nuclear envelope, which forms a barrier between it and the cytoplasm. The nuclear envelope consists of both an outer and an inner nuclear membrane (lipid bilayer). Nuclear pores within the nuclear envelope control which proteins and RNA can pass between the nucleus and the cytoplasm.

Light patches of staining, known as euchromatin, contain DNA that is being actively transcribed. Darker staining patches of heterochromatin contain DNA that is not being actively transcribed. The nucleolus is where ribosomal RNA is processed and assembled into ribosome subunits.

The nucleus and the nucleoli can be seen in sections by light microscopy (Fig. 5c). The appearance of nuclei varies between cells and cell types, and depends on the activity of the cells.

Cellular organelles

Endoplasmic reticulum

The endoplasmic reticulum (ER; Fig. 5d) is a single internal membrane system that extends throughout the cytoplasm, and makes up about 10% of the total cell volume. Its membrane is continuous with the outer nuclear membrane. The ER synthesizes lipids and proteins, generating the membranes of most of the organelles in the cell, and it stores Ca2+. Some proteins are internalized into its lumen and sent to the Golgi to be modified.

Rough ER (Fig. 5d) is organized into parallel layers of flattened sacs and covered with ribosomes. Its lumen is 20-30 nm wide. The cytoplasm of cells rich in rough ER stains a darker pink, or blue/ purple with H&E due to the high amounts of RNA in the many ribosomes, which are acidic, and therefore stain blue/purple with hematoxylin. Rough ER synthesizes secretory proteins and lysosomal enzymes.

Smooth ER (Fig. 5d) is not covered with ribosomes. It is branched and has a wider lumen than rough ER (30-60 nm).

Golgi apparatus

The Golgi apparatus (Fig. 5e) is found close to the nucleus. It glycosylates proteins received from the ER and packages them for transport to the plasma membrane. It also retrieves and recycles proteins.

It consists of 3 to 7 flattened discs of membranes, called cisternae.

The receiving face of the Golgi is called the ‘cis’ (receiving, forming, or entry) face.

Proteins exit via the trans (maturing or exit) face.

Vesicles

Cells contain a large number of vesicles (Fig. 5e).

Secretory vesicles: These travel from the Golgi to the plasma membrane.Endocytic vesicles: