Histology “study of tissues”
Jan 03, 2016
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