Histology“study of tissues”

History of the Microscope

Robert Hooke- 1665• Created the first

microscope• Looked at cork tissue• Coined the term cells

History of the MicroscopeAnthony van Leeuwenhoek-

1673• Created microscopes that

magnified 200X, brighter and clearer

• First saw microscopic organism in pond water

Microscope parts

Magnification• 10X Ocular (eye piece)

• 4X Scanning objective)– Is used for initial location of the specimen

• 10X Low power objective – May also be used for initial location of the specimen or for observing

specimens that don't need greater magnification

• 40X High-dry objective– Is used for specimens requiring greater magnification– Does not require the use of oil

• 100X Oil immersion objective – Used for magnification of extremely small specimens– Oil prevents refraction of light so images are less distorted

Calculating Magnification

Eye piece X Objective lens= Total magnification

10 X 40 = 400

10X 100X oil

Functions

• Stage- used to set slide on

• Mechanical Stage- had adjustable brackets that move stage around

• Condenser- between light source and stage, concentrates light

• Diaphragm- controls amount of light coming in and out

Functions

• Coarse adjustment knob- used first to locate specimen**never use in high-dry or oil immersion or you

will crack the slide

• Fine adjustment know- moves very little used to focus in high powers

Resolution

• The resolution limit, or resolving power, of a microscope lens is a function of its numerical aperture, the wavelength of light, and the design of the condenser.

• The maximum resolution of the best microscopes is around .2µm. This means that two small objects that are 0.2µm apart will be seen as separate entities; objects closer than that will be seen as a single object.

Resolution

Lens Care

• Dust, oil and other contaminants on the lens can reduce resolution.

• Only lint free tissues should be used to clean the lens

• If there is still contaminants on the lens you may use some mild soap and water with lens tissue to clean the lens

Oil Immersion

• Oil can be used to enhance the resolving power of the microscope

• Locate the object in either low or high dry magnification

• Rotate the oil immersion objective lens in half-way position.

• Place a drop of immersion oil on the slide and lower the lens

• Open the diaphragm as much as possible, the manipulation of light is critical

• Always clean the lens and slide before returning the microscope to the cabinet.

Histology

• Tissue- a group of cells that perform a similar function– Can be one cell thick or a

mass of millions of cells• Matrix- non-living

intercellular material that surrounds cells– Some tissues are

surrounded entirely by matrix others have very little

• Desmosome and tight junctions hold tissues together

Germ Layers

• Zygote form in hollow balls of cells called a blastocyst

• Blastocyst undergoes gastrulation and the layers begin to form different tissues

MesodermMuscles

Skelton (bones & cartilage)

Blood

Epithelial lining of blood vessels

Dermis of skin Organs(except lining) excretory & reproductive

Connective tissue

EctodermEpithelium9epidermis) of skin

Lining of mouth, anus, nostrils

Sweat glands and sebaceous glands

Nervous system

Epithelial (sensory) parts of eyes, nose, ear

EndodermEpithelial (lining) of digestive & respiratory systems

Secretory parts of liver & pancreas

Urinary bladder

Epithelial lining of urethra

Thyroid, parathyroid, thymus

Types of Tissue

1. Epithelial

2. Connective

3. Muscle

4. Nervous

Functions of Epithelial Tissue• Covers & protects• Lines cavities• Secretion & Glands

– Mucus– Hormones– Sweat

• Excretion– Kidneys

• Absorption– Lining of gut – Lining of respiratory tract

General Characteristics of Epithelial Tissue

• Limited intercellular space or matrix• Continuous sheets packed tightly together• Avascular, contains no blood vessels

– Nutrients move through diffusion

• Basement membrane adheres it to connective tissue– Integrins bind cytoskelton of cells to basement

membrane

• Because they go through so much wear and tear they have a high mitotic rate

Classification of Epithelial Tissues

Simple Squamous Epithelial

• One layer, flat scale like cells

• Substances can diffuse/filter easily– Examples

• Alveoli• Blood vessels• Pleural membranes

Simple Squamous Epithelial

Simple Cuboidal Epithelium

• One layer of cuboidal cells resting on basement membrane– Examples

• Glands and ducts• Ducts & tubules of

kidneys

Tubules in kidneys

Simple Columnar Epithelium

• Adapted for secretion• Examples

– Lines stomach– Uterus & ovaries– Eyes

• Modifications– Goblet cells

• Have vesicles filled with mucus – Microvilli & Cilia

• Plasma membrane extends out

Pseudostratified Columnar Epithelium

• All the cells touch the basement membrane

• Irregular placement of nuclei

• Not all reach the top layer

• Lots of goblet cells and cilia

• Examples– Lining air passages– Segment of male

urethra

Pseudostratified Columnar Epithelium

Stratified Squamous (Keratinized) Epithelium

• Multiple layers• Flatted cells on

surface• Dead keratinized

cells at surface– Examples

• Skin, kertin provides protection

Stratified Squamous (Keratinized) Epithelium

Stratified Squamous (Non-keratinized) Epithelium

• Look for nuclei at superior border• Flattened cells at surface• Many layers• Surface is moist

– Examples• Vagina• Mouth• esophagus

Stratified Squamous (Non-keratinized) Epithelium

Stratified Cuboidal Epithelium

• Two or more rows of cuboidal cells

• Arranged randomly– Examples

• Sweat gland ducts• Pharynx• epiglottis

Stratified Cuboidal Epithelium

Stratified Columnar Epithelium

• Only most superficial cells are columnar in appearance

• Protective epithelium– Examples

• Male urethra• Mucosa layer near

anus

Stratified Columnar Epithelium

Stratified Transitional Epithelium

• Found in areas subject to stress and tension

• Prevent tearing• When stretched cell

change shape from cuboidal to squamous– Examples

• Bladder

Glandular Epithelium• Glandular secretions rely on

highly regulated cellular activity that requires using stored energy

• Mulitcellular or unicellular(goblet cell) Often formed from cuboidal cells.

• Exocrine Glands -release secretion into ducts– Salivary glands– Sebaceous glands– Sweat glands– lacrymal glands

• Endocrine Glands- ductless glands that release secretions(hormones) directly into blood– Pituitary gland– Thyroid gland– adrenal

Thyroid gland Islet of Langerhans

Exocrine Glands• Apocrine glands

– Secretion collect in tip(apex) of gland– Secretions are released when distended end

is pinched off– Cell loses cytoplasm and is damaged– Recovery is quick and cell continues to

release secretions• Mammary glands• Sweat glands

• Holocrine glands– Collect secretions inside the cell– Rupture completely to release secretion– Cell is destroyed

• Sebaceous glands

• Merocrine glands– Secretion is released directly through plasma

membrane– No loss of cytoplasm or damage to cells– Most common gland

• Salivary glands• Sweat glands not associated with hair

Exocrine Glands

Apocrine gland

Holocrine gland

Merocrine gland

Connective Tissue

• Most common tissue found in body• Can be delicate-thin, tough-rigid or

fluid

Main Functions • Connect

– Muscle to muscle– muscle to bone– Bone to bone

• Supports – Framework for body and organs

• Transports– blood

• Defends– Protects against microorganisms

Connective Tissue

Characteristics• Matrix-intercellular material, fibers• Ground substance, provides medium for

exchange of substances• components of matrix and ground tissue

define the type of tissue• Highly vascular and innervated (not all)• Mesenchyme- tissue in embryo that all

other connective tissue arises from

Types of Fibers

Fibroblasts create these protein fibers1. Collagen (white fibers) most common protein in body

• Tough and strong• Occur in bundles• Hydrated form known as gelatin

2. Reticular • Special type of collagen, reticulin• Occur in bundles yet are delicate• Supports capillaries and nerve fibers

3. Elastic fibers• Retains shape after being stretched• Made from protein elastin• Found in stretchy tissue such as the external ear

4. Proteoglycans• Made of polysaccharide chains containing glucosamine• Thicken the matrix to create barrier against

bacteria/microbes• Transparent lubricant that hold tissue together

Classification of Connective Tissue

1. Fibrous (loose)• Areolar (ordinary)• Adipose• Reticular• Dense

2. Bone

3. Cartilage• Hyaline• Fibrocartilage• Elastic

4. Blood

Areolar(loose ordinary)• Elastic glue that permits

movement

• Stretchable and very common

• Matrix is soft thick gel, contains hyaluronidase

• Hyaluronidase is an enzyme that can change thick gel matrix to watery state

• Contain interwoven fibers of collagen and elastin

• Main types of cells– Fibroblasts- synthesizes ground

substance and fibers

– Macrophages(histiocytes)- carry on phagocytosis

– Mast cells- wandering white blood cell

– Fat & plasma cells

Areolar(loose ordinary)

Adipose Tissue

• Mainly fat cells• Few fibroblasts,

mast cells and macrophages

• Cushions organs• Stores excess

energy• Conserves body

heat

Adipose Tissue

Reticular Tissue

• 3 dimentional meshwork of reticular fibers

• Defense against microorganims and injurious substances

• Filters toxic substance out of blood and lymph

• Framework for spleen, lymph nodes and bone marrow

Reticular Tissue

Dense Fibrous Tissue• Fibers are densely

packed in matrix• Bundles of collagen fibers• Flexible but very strong

• Regular is parallel fibers– Tendons(muscle to bone)– Ligaments, more elastin (bone to bone)

• Irregular (wavy) dense tissue withstands stress from any direction

– Forms dermis– Outer capsule of kidneys & spleen

Dense Fibrous Irregular

Dense Fibrous Tissue

Dense Fibrous Regular

Bone (osseous tissue)

Characteristics• Osteocytes- mature bone cells• Matrix contains mineral salts

and collagen• Mineral salts are responsible

for hardness of bone• Ostecytes are trapped in small

spaces called lacunae • Haversian canals allow blood

vessels to bring nutrition to cells

Functions• Protection • Movement• Mineral storage• Create blood cells

Bone Tissue

Ossified Bone (hard bone)

Cancellous Bone (spongy bone)

Cartilage Tissue

Characteritics• Chondrocyte- only type

of cell in cartilage• Chondrocyte produce

tough fibers and ground substance

• *Chondrocyte found in *Chondrocyte found in lacunaelacunae

• Avascular and no nerves• Substances must diffuse

through connective tissue surrounding cartilage called perichondrium

Types of Cartilage

Hyaline(greek for glass)• Low amounts of

collagen• Shiny translucent

appearance• Found in respiratory

rings end of bones

Hyaline CartilageHyaline Cartilage

Types of CartilageFibrocartilage• Strongest type of cartilage• Densely packed with white collagen• Shock absorbers• Intevertebral discs and knee joints

Intervertebral Disc

Fibrocartilage

Dense Fibrous Connective

100X

400X

Types of Cartilage

Elastic Cartilage• Very little collagen• Many very fine

elastin fibers• Highly flexible• External ear, voice

box, layrnx• “Hairier” that hyaline

Elastic Cartilage

Blood Tissue

• Has neither ground substance nor fibers

• Exists in liquid state, plasma

• Erythrocytes- red blood cells

• Leukocytes- white blood cells

• Thrombocytes- platelets• Moves gases, nutrients

& wastes• Hematopoietic tissue-

blood forming tissue

Blood Tissue

Muscle Tissue

• High degree of contractility • Provide movement and

produce heat– Skeletal (striated voluntary)– Smooth (non striated

involuntary or visceral)– Cardiac (striated involuntary)

Skeletal Muscle

Skeletal Muscle

Smooth Muscle

Smooth Muscle

Smooth Muscle

Cardiac Muscle

Cardiac Muscle

Nerve Tissue• Functions

– Regulates and integrates body functions

– High conductivity and excitability

• Structures– Neurons– Neuroglia (supporting

cells)– Brain, spinal cord,

nerves

Nerve Tissue

Body Membranes

• Protect body surfaces

• Line cavities• Anchor organs• Reduce friction

Histology Review Website

• http://www.histology-world.com

• http://www.histology-world.com/audioslides/audio.htm