2 histology
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Histology:The Study of Tissues
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Tissues
A group of closelyassociated cells thatperform related functionsand are similar in
structure Four types-
epithelium (covering)
connective (support)
muscle (movement)
nervous (control)
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Extracellular Matrix Extracellular Protein
Fibers
Ground substance-syrup like fluid
ECF
Interstitial fluid
Tissue fluid
So lets summarize:
Tissues- cells and extracellular matrix (fibersand ground substance).
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Interpreting tissue sections
Histological sections areprepared by a microtome(thin slices of the tissue);smears; spreads
fixative Dehydrated (might occur
with fixation stage)
stained
Review your planes and
be sure you can seehow to put a tissue backtogether!
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Epithelia and Glands Epithelium is a sheet of cells
that covers a body surface orlines a body cavity
Inner lining of stomach andviscera, respiratory tubes,peritoneal cavity, innerlining of blood vessels,most of bodys glands
Occur at interfaces between
two different environments,provide a boundary
Protect and provide sensoryinformation, secrete,absorption, ion transport, formslippery surfaces
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Special Characteristics of Epithelia
1. Cellularity- composed of cells with minimal extracellular material
2. Attachment- anchored to a basement membrane
3. Polarity- free edge (apical) and lower (basal) surface.
4. Avascular but innervated- lack blood vessels but do receivenerve endings
5. Regeneration: Friction resistance! Constantly being rubbed offand replaced.
6.
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Classification of Epithelia
Number of layersShapeALWAYS LOOK AT APICAL LAYER
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Simple Epithelia Single layer of cells Important for passive
diffusion (squamous) orabsorption/secretion(cuboidal or columnar)
Special cases:
endothelium (found in
heart and bloodvessels)
mesothelium (linesserosal cavities)
Pseudostratifiedcolumnar- all cellstouch basementmembrane!
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Simple Squamous
Epithelium
Common sites ofdiffusion andfiltration
Alveoli
Endothelium of
blood capillaries
Glomerulus
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Simple Cuboidal Epithelium
Functions in secretionand absorption
Kidney tubules
Ducts of salivaryglands, thyroid gland,pancreas
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Simple Columnar Epithelium Specialized for
absorption
Presence of gobletcells ( secrete mucus)
Gastrointestinal tract
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Pseudostratified ColumnarEpithelium
Protection, secretion,ciliary movement
often ciliated
Many goblet cells
Lines passages ofrespiratory system-trachea, bronchi
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Stratified Epithelia- 2 or morelayers
More durable andmajor role isprotection
Regenerate frombelow
Keratinized
(waterproofed bydead layer of cells-skin) vs. non-keratinized(esophagus, vagina-)
Stratified Squamous Epithelium
Protection ( wear andtear areas)
Outer layers flattened
Blocks variouschemicals andmicroorganisms fromentering
Found in mouth,esophagus, nasalcavity, anus, vagina,skin 14
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Transitional Epithelium Lines the inside of
hollow urinaryorgans (bladder)and umbilical cord
Allows fordistention(stretching)
Thus, it goesthroughtransitions inshape. 15
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Connective Tissue
Most abundant
Connective tissue proper
Supportive (cartilage and bone) Fluid (blood and lymph)
Function- connect cells, form skeleton (lever system),
store and carry nutrients, surround all the blood vesselsand nerves of the body, fight against infection, heatproduction, physical protection.
Cells always separated by a large amount of nonlivingextracellular material (extracellular matrix)
Originate from mesoderm (mesenchyme).
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Types of Connective tissue
Connective tissues
Connective tissue proper (fibrous) Fluid Supporting
Loose Dense Blood lymph cartilage bone
Solid, rubber
matrixSolid,crystallinematrix
Contained in
Cardiovascularsystem
Contained in
lymphaticsystem
Fibers create
loose, openframework
Fibers densely
packed
AreolarAdiposereticular
RegularIrregular
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Cells you would find in ConnectiveTissue Proper
Fibroblasts- produce fibers andground substance that formsthe matrix
Macrophages (derived frommonocytes- a type of WBC)
Mesenchymal cells
Leukocytes (WBC)
Mast cells-
Histamine- increases bloodflow by dilating bloodvessels
Heparin- inhibits bloodclotting
Adipocytes (fat cells)
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Fibers you would find in
Fibrous Connective Tissue
Collagenous fibers- whitefibers, tough and flexible(resist stretching)
Reticular fibers- thincollagen fibers--Formsponge-like framework(spleen and lymph nodes)
Elastic- Allows stretching
and recoiling (rubber band) Lungs, skin, arteries
Elasticity- NOT theability to stretch, ratherthe ability to recoil whenreleased)
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Areolar connective tissue (model type)
Support and bindingof tissues
Holding body fluids
Defending the bodyagainst infection
Storing nutrients asfat
Waste removal
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Other loose connective tissues Adipose tissue - function
is to store nutrients.Highly vascularized.Mostly found in
hypodermis (telasubcutanea)
Reticular Connectivetissue resembles
areolar tissue, but onlyhas reticular fibers inextracellular matrix.
spleen, lymph nodes,thymus and bone marrow
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Dense Connective Tissue
Dense irregularconnective tissue- similarto areolar tissue, butcollagen fibers muchthicker. Two layers
running perpendicular toeach other.
Dense regular connectivetissue- fibers run in thesame direction- parallel tothe direction of pull(ligaments, tendons,aponeuroses, elastictissue)
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Cartilage Resist compression
and tension
no blood vessels ornerves.
Hyaline-mostabundant
Elastic
fibrocartilage
Cartilage
Hyaline cartilage (glass) most abundant cartilage,many delicate collagen fibrils Provides support through flexibility
Epiphyseal plates, fetal skeleton, trachea, larynx
Elastic cartilage contains many elastic fibers andcollagen fibrils Able to tolerate repeated bending
Ear, external auditory canal, epiglottis
Fibrocartilage resists strong compression and strongtension An intermediate between hyaline and elastic cartilage, many
thick collagen fibers
Intervertebral discs, menisci, pubic symphysis.
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Bone matrix contains inorganic
calcium salts andcollagen fibers.
Spongy- heads of longbones
Compact
Haversian system(osteon) Central canal (Haversian
canal)
Lacunae
Lamellae
Canaliculi
Osteocytes
Periosteum
Osteoblasts
osteoclasts
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Blood Fluid ground substance Transports nutrients,
wastes, gases
Erythrocytes (RBCs)
Leukocytes (WBCs)-neutrophils,eosinophils, basophils,monocytes,lymphocytes (T and Bcells)
Platelets(thrombocytes)
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Muscle Movement
Posture/jointstability
Heat Production
Communication
(facial muscles)
Control of bodyopenings
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3 Classes of Muscle
Based on histological
appearance and function
Skeletal
Striated, voluntary,
myofibers
Cardiac
Striated, involuntary,
branched, cardiocytes
Smooth
Non-striated, involuntary,
fusiform in shape (spindle)
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Skeletal Muscle Striated
Voluntary
Multi-nucleated
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Cardiac Muscle
Striated
Involuntary
Branched
Cardiocytes
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Smooth Muscle Smooth (non-striated)
Involuntary
Fusiform (spindleshaped)
Nervous Tissue
Conductive cell = neuron
Receives/transmitselectrochemical
impulses Dendrites, body (soma),
axon
Glial cells (supportive)
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Homework: Pages 23- 24, due nextmeeting