Histology – Study of TissuesHistology – Study of Tissues

Tissue Tissue

- Group of closely associated cells that are Group of closely associated cells that are similar in structure and work together to similar in structure and work together to perform a function.perform a function.- Cells are nearly always embedded in or Cells are nearly always embedded in or

surrounded by nonliving matrixsurrounded by nonliving matrix

- Most organs contain some of each of the Most organs contain some of each of the four main tissue types:four main tissue types:- Epithelial, connective, muscle, nervousEpithelial, connective, muscle, nervous

Embryonic Germ Embryonic Germ LayersLayers

1.1. EndodermEndoderm- inner layer which forms the lining of - inner layer which forms the lining of the digestive systemthe digestive system

2.2. MesodermMesoderm- middle layer which forms muscles, - middle layer which forms muscles, bones, and blood vesselsbones, and blood vessels

3.3. EctodermEctoderm- outer layer that forms the skin and - outer layer that forms the skin and nervous systemnervous system

Primary Germ LayersPrimary Germ Layers

Epithelial TissueEpithelial Tissue

Serve to cover a body surface or line a cavityServe to cover a body surface or line a cavityTwo main types:Two main types:

1. Covering and lining epithelium1. Covering and lining epithelium- all substances entering and leaving the - all substances entering and leaving the body must pass through body must pass through 2. glandular epithelium makes-up the glands 2. glandular epithelium makes-up the glands of the bodyof the body

FunctionsFunctionsA)A) ProtectionProtection

- from mechanical and chemical injury- from mechanical and chemical injury- from invasion by bacteria and viruses- from invasion by bacteria and viruses

B)B) Sensory Sensory - specialized epithelium found in skin, nose, - specialized epithelium found in skin, nose, eye, and eareye, and ear

C) SecretionC) Secretion

- glandular epithelium secretes hormones, - glandular epithelium secretes hormones, mucus, digestive juices, and sweatmucus, digestive juices, and sweat

D) AbsorptionD) Absorption

- lining epithelium of intestines and respiratory - lining epithelium of intestines and respiratory systems allow absorption of nutrients and gasessystems allow absorption of nutrients and gases

E) ExcretionE) Excretion

- in kidneys and skin waste products are excreted- in kidneys and skin waste products are excreted

F) FiltrationF) Filtration

- specialized epithelium in the kidneys filter - specialized epithelium in the kidneys filter waste products from the bloodwaste products from the blood

Characteristics of Epithelial TissueCharacteristics of Epithelial Tissue1.1. CellularityCellularity

- composed almost entirely of cells- composed almost entirely of cells

- very little extracellular material- very little extracellular material

2.2. Specialized contactsSpecialized contacts

- are held together in continuous sheets by - are held together in continuous sheets by many lateral contactsmany lateral contacts

3. Polarity3. Polarity

- free surface = apical surface- free surface = apical surface

- exposed surface- exposed surface

- cells often have microvilli or cilia - cells often have microvilli or cilia attached to attached to increase surface areaincrease surface area

- basal surface = attached- basal surface = attached

4.4. Basement MembraneBasement Membrane

- basal lamina is a noncellular adhesive sheet - basal lamina is a noncellular adhesive sheet that attaches epithelial tissue to underlying that attaches epithelial tissue to underlying structuresstructures

- serves as a selective filter- serves as a selective filter

- important in healing of wounds- important in healing of wounds

- reticular lamina is connective fibers produced - reticular lamina is connective fibers produced by underlying connective tissueby underlying connective tissue

- cancerous epithelial cells can pass through - cancerous epithelial cells can pass through the basement membrane to underlying tissuesthe basement membrane to underlying tissues

5. Innervated but avascular5. Innervated but avascular

- contains nerve endings, but no blood vessels- contains nerve endings, but no blood vessels

- nutrients must diffuse into the tissue from - nutrients must diffuse into the tissue from underlying tissuesunderlying tissues

6. Regeneration6. Regeneration

- as long as they receive nutrients they can - as long as they receive nutrients they can regenerate by mitosisregenerate by mitosis

Classification of EpitheliaClassification of EpitheliaEach epithelium is given two names:Each epithelium is given two names:

First name indicates number of cell layers:First name indicates number of cell layers:

A. Simple – single layer of cellsA. Simple – single layer of cells

- - often found in areas of absorption and often found in areas of absorption and filtrationfiltration

B. Stratified – consists of two or more layers of B. Stratified – consists of two or more layers of cellscells

- found in areas of abrasion- found in areas of abrasion

Second name indicates the shape of the cells:Second name indicates the shape of the cells:

A. squamous – flattened and scale-likeA. squamous – flattened and scale-like

B. cuboidal – cells are about as tall as they are wideB. cuboidal – cells are about as tall as they are wide

C. columnar – cells are taller and column shapedC. columnar – cells are taller and column shaped

Classification of Epithelial TissuesClassification of Epithelial Tissues

Simple Squamous Simple Squamous

- single layer of flattened- single layer of flattened

cellscells

- linings of alveoli, blood- linings of alveoli, blood

vessels, and manyvessels, and many

membranesmembranes

- absorption, filtration,- absorption, filtration,

secretionsecretion

Simple Squamous lining of lung.Simple Squamous lining of lung.

Simple cuboidal epitheliumSimple cuboidal epithelium

Simple columnar epitheliumSimple columnar epithelium

Pseudostratified ciliated epitheliumPseudostratified ciliated epithelium- - lines trachea, bronchi, epididymis, and vas lines trachea, bronchi, epididymis, and vas deferensdeferens

- protection and movement of mucus- protection and movement of mucus

Stratified squamous (keratinized) Stratified squamous (keratinized) epitheliumepithelium- forms epidermis of skin, surface of cornea, - forms epidermis of skin, surface of cornea, lining of mouth, esophagus, anuslining of mouth, esophagus, anus

- protection- protection

Stratified Squamous (nonkeratinized) Stratified Squamous (nonkeratinized) epitheliumepithelium

Transitional epitheliumTransitional epithelium- often found in areas that are subjected to - often found in areas that are subjected to stress and tension changes, such as urinary stress and tension changes, such as urinary bladderbladder

- usually composed of 10 or more layers of - usually composed of 10 or more layers of cuboidal cellscuboidal cells

Glandular EpitheliumGlandular Epithelium- specialized for secretory activity- specialized for secretory activity

- cells may function as unicellular or multicellular - cells may function as unicellular or multicellular glandsglands

Glands are classified as:Glands are classified as:

1. Exocrine 1. Exocrine

- discharge through ducts- discharge through ducts

- ex.: salivary glands- ex.: salivary glands

2. Endocrine2. Endocrine

- secrete products directly into the blood or - secrete products directly into the blood or interstitial fluidinterstitial fluid

- ex.: pituitary, thyroid, adrenals- ex.: pituitary, thyroid, adrenals

Connective TissuesConnective TissuesFunctions:Functions:

A. Binding and supportA. Binding and support

- tendons and ligaments hold bones and muscles - tendons and ligaments hold bones and muscles to each otherto each other

- in soft organs, connective tissue supports and - in soft organs, connective tissue supports and binds cells togetherbinds cells together

B. ProtectionB. Protection

- bone and cartilage support and protect body - bone and cartilage support and protect body organsorgans

C. InsulationC. Insulation

- fat cushions, insulates, and protects body - fat cushions, insulates, and protects body organs as well as providing reserve energy fuelorgans as well as providing reserve energy fuel

D. TransportationD. Transportation

- blood transports materials within the body- blood transports materials within the body

Characteristics of Connective TissueCharacteristics of Connective Tissue

1. Intercellular Matrix1. Intercellular Matrix

- non-living material that makes-up most of the - non-living material that makes-up most of the tissuetissue

- cells are embedded in the ground substance- cells are embedded in the ground substance

- gives different connective tissues their varying - gives different connective tissues their varying qualitiesqualities

- allows it to bear lots of weight, withstand - allows it to bear lots of weight, withstand tension, and endure physical abusetension, and endure physical abuse

2. Common origin2. Common origin

- all originate from mesoderm- all originate from mesoderm

3. Various degrees of vascularity3. Various degrees of vascularity

Fibers in connective tissue:Fibers in connective tissue:

A. Collagenous (white) A. Collagenous (white)

- tough, often in bundles, high tensile strength, - tough, often in bundles, high tensile strength, non-elasticnon-elastic

- found in tendons and ligaments (tough, flexible - found in tendons and ligaments (tough, flexible support)support)

- collagen is the most abundant protein in our - collagen is the most abundant protein in our bodiesbodies

B. Reticular fibersB. Reticular fibers

- delicate fibers found in networks with elastic - delicate fibers found in networks with elastic and collagenous fibersand collagenous fibers

- slightly elastic- slightly elastic

- found in lymphatic tissues (nodes) and - found in lymphatic tissues (nodes) and supporting small structuressupporting small structures

C. Elastic fibers (yellow)C. Elastic fibers (yellow)

- tough, elastic fibers that are not found in - tough, elastic fibers that are not found in bundlesbundles

- tough, expandable support- tough, expandable support

- in aorta, arteries, trachea, and bronchi- in aorta, arteries, trachea, and bronchi

Four main categories of connective Four main categories of connective tissues based on the matrix:tissues based on the matrix:

1. Fibrous1. Fibrous

- extracellular fibers are predominant features- extracellular fibers are predominant features

2. Bone2. Bone

- has fibers and a hard mineral ground substance- has fibers and a hard mineral ground substance

3. Cartilage3. Cartilage

- fibers with a specialized ground substance that - fibers with a specialized ground substance that traps water to form a firm geltraps water to form a firm gel

4. Blood4. Blood

- lacks fibers- lacks fibers

- liquid matrix - plasma- liquid matrix - plasma

Cells in connective tissues are designated by their Cells in connective tissues are designated by their suffixsuffix

as to what they do:as to what they do:

- blast – creates the matrix- blast – creates the matrix

- cyte – maintains the matrix- cyte – maintains the matrix

- clast – breaks down the matrix- clast – breaks down the matrix

Examples of Connective TissuesExamples of Connective Tissues

A. Loose (Areolar)A. Loose (Areolar)

- widely distributed- widely distributed

- ground substance is a soft viscous fluid- ground substance is a soft viscous fluid

- collagenous and elastic fibers in a loose - collagenous and elastic fibers in a loose networknetwork

- elastic glue – holds, but allows movement- elastic glue – holds, but allows movement

- found under skin – superficial fascia- found under skin – superficial fascia

B. Adipose TissueB. Adipose Tissue

- same matrix and fibers as areolar, but majority of - same matrix and fibers as areolar, but majority of tissue is composed of fat cellstissue is composed of fat cells

- fat cells are large, round, and delicate w/ nucleus- fat cells are large, round, and delicate w/ nucleus

- act as padding around organs, insulation for heat - act as padding around organs, insulation for heat conservation, and as a reserve energy storage conservation, and as a reserve energy storage sitesite

Fat storage areas – males versus femalesFat storage areas – males versus females

C. Reticular connective tissue C. Reticular connective tissue

- spleen and lymph nodes- spleen and lymph nodes

- function in filtering and cleaning the blood- function in filtering and cleaning the blood

D. Dense fibrous (regular) connective tissue D. Dense fibrous (regular) connective tissue

- mostly fibers packed densely in the matrix- mostly fibers packed densely in the matrix

- found in areas needing tensile strength and - found in areas needing tensile strength and flexibilityflexibility

- tendon, ligaments, dermis, scar tissue- tendon, ligaments, dermis, scar tissue

E. Dense fibrous (irregular) connective E. Dense fibrous (irregular) connective tissue - dermistissue - dermis

F. Bone tissueF. Bone tissue

- matrix of inorganic - matrix of inorganic calcium salts and calcium salts and collagenous fiberscollagenous fibers

- osteocytes – bone - osteocytes – bone maintaining cellsmaintaining cells

- organized in Haversion - organized in Haversion Systems - OsteonsSystems - Osteons

osteocytes in lacunae

- lamellae – concentric circles of matrix

- canaliculi – small canals connecting lacunae -

G. CartilageG. Cartilage

- fiber matrix of collagenous and elastic fibers- fiber matrix of collagenous and elastic fibers

- chondrocytes – cartilage generating cells that - chondrocytes – cartilage generating cells that secrete matrix and ground substancesecrete matrix and ground substance

- firm, tough and flexible- firm, tough and flexible

- lacks blood vessels- lacks blood vessels

FibrocartilageFibrocartilage Elastic CartilageElastic Cartilage

H. BloodH. Blood

- matrix = plasma- matrix = plasma

- 90% water w/ dissolved proteins, food, - 90% water w/ dissolved proteins, food, metabolic wastes and dissolved gasesmetabolic wastes and dissolved gases

- formed elements made in bone marrow- formed elements made in bone marrow

- erythrocytes – red blood cells – carry oxygen- erythrocytes – red blood cells – carry oxygen

- leukocytes – white blood cells – defense against - leukocytes – white blood cells – defense against microbesmicrobes

- thrombocytes/platelets – help in clotting- thrombocytes/platelets – help in clotting

Muscle TissueMuscle Tissue- highly cellular and well vascularized- highly cellular and well vascularized

- composed of contractile protein fibers called - composed of contractile protein fibers called myofilamentsmyofilaments

FunctionsFunctions

- provide movement- provide movement

- squeeze contents of internal organs- squeeze contents of internal organs

- generate heat- generate heat

Striated vs. NonstriatedStriated vs. Nonstriated

- striated muscle is arranged so that it has a - striated muscle is arranged so that it has a striped appearance under the microscopestriped appearance under the microscope

Voluntary vs. InvoluntaryVoluntary vs. Involuntary

- voluntary muscles can be consciously controlled- voluntary muscles can be consciously controlled

Smooth muscleSmooth muscle

- found in internal organs- found in internal organs

- normally involuntary- normally involuntary

- spindle-shaped cells w/ one - spindle-shaped cells w/ one nucleusnucleus

Skeletal muscleSkeletal muscle- voluntary muscles - voluntary muscles responsible for responsible for movementmovement- long, cylindrical fibers- long, cylindrical fibers- striated- striatedmultinucleatemultinucleate

Cardiac muscleCardiac muscle

- muscle of the heart- muscle of the heart

- branching fibers with - branching fibers with single nucleussingle nucleus

- intercalated discs - intercalated discs connect cellsconnect cells

- striated- striated

Nervous tissue – functions in control mechanisms Nervous tissue – functions in control mechanisms of the body and in coordinating responses to the of the body and in coordinating responses to the environmentenvironment

NeuronsNeurons

- nerve cells which transmit electrochemical signals- nerve cells which transmit electrochemical signals

- soma = cell body- soma = cell body

- axon – carries impulse away from soma- axon – carries impulse away from soma

- dendrite – carries impulse toward soma- dendrite – carries impulse toward soma

1. Afferent = sensory1. Afferent = sensory

- transmit impulses to CNS from sense organs- transmit impulses to CNS from sense organs

2. Efferent = motor, secretory, accelerator, 2. Efferent = motor, secretory, accelerator, inhibitoryinhibitory

- transmit impulses from CNS to muscles or effector - transmit impulses from CNS to muscles or effector organsorgans

3. Association3. Association

- within CNS- within CNS

- run between afferent and efferent neurons- run between afferent and efferent neurons

NeurogliaNeuroglia

- helper cells which nourish, protect, and insulate - helper cells which nourish, protect, and insulate neuronsneurons

MembranesMembranes- thin sheet of tissue that covers a structure or lines a - thin sheet of tissue that covers a structure or lines a

cavitycavity

- most are derived from epithelial and connective - most are derived from epithelial and connective tissuestissues

1. Serous membranes1. Serous membranes

- line cavities that do not open to outside of body- line cavities that do not open to outside of body

- normally composed of simple squamous epithelium- normally composed of simple squamous epithelium

- secretes fluid to decrease friction between - secretes fluid to decrease friction between structuresstructures

- - parietal layerparietal layer – covers the body wall – covers the body wall

- - visceral layervisceral layer – covers the outer part of the organ – covers the outer part of the organ

2. Mucous membranes2. Mucous membranes

- line cavities that do open to the outside- line cavities that do open to the outside

- stratified squamous epithelium w/ connective tissue - stratified squamous epithelium w/ connective tissue belowbelow

- produces a fluid to trap particles or to keep - produces a fluid to trap particles or to keep underlying tissues moistunderlying tissues moist

3. Synovial membranes3. Synovial membranes

- line synovial joints (mostly movable joints)- line synovial joints (mostly movable joints)

- produce a liquid that lubricates and cushions - produce a liquid that lubricates and cushions the jointthe joint

Tumors and CancerTumors and CancerNeoplasms, also called tumors, are any abnormal Neoplasms, also called tumors, are any abnormal

growth of cellsgrowth of cells

Benign tumorsBenign tumors do not spread to other tissues and do not spread to other tissues and normally grow slowly. normally grow slowly.

- cells tend to stay together and are often in a - cells tend to stay together and are often in a capsulecapsule

- normally not life threatening unless they - normally not life threatening unless they interfere with organ functioninterfere with organ function

Malignant tumorsMalignant tumors, or , or cancerscancers, are not encapsulated , are not encapsulated and tend to spread to other regions.and tend to spread to other regions.

- spread to other regions in blood or lymph- spread to other regions in blood or lymph

- metastasis – spread of a cancer- metastasis – spread of a cancer

Cancer factors:Cancer factors:

- genetic factors, carcinogens, age- genetic factors, carcinogens, age

Detection and Treatment Detection and Treatment

Cancer specialists are OncologistsCancer specialists are Oncologists

- early detection is important- early detection is important

1. Self-examination1. Self-examination

- some cancers (breast and testicular for - some cancers (breast and testicular for example) can be detected by self-examinationexample) can be detected by self-examination

2. Medical imaging2. Medical imaging

- radiography – x-ray photographs can find many - radiography – x-ray photographs can find many

- mammography- mammography

- computed tomography (CT) – x-ray scanning- computed tomography (CT) – x-ray scanning

- magnetic resonance imaging (MRI) - magnetic resonance imaging (MRI)

- ultrasonography- ultrasonography

3. Blood tests can detect abnormalities3. Blood tests can detect abnormalities

4. Biopsy is removal and examination of living 4. Biopsy is removal and examination of living tissuetissue

Without treatment cancer usually results in death.Without treatment cancer usually results in death.

A. Surgical removalA. Surgical removal

B. ChemotherapyB. Chemotherapy

- uses cytotoxic compounds and antineoplastic - uses cytotoxic compounds and antineoplastic drugs to kill malignant cellsdrugs to kill malignant cells

C. Radiation therapyC. Radiation therapy

- uses x-ray or gamma radiation to destroy - uses x-ray or gamma radiation to destroy cancercancer

- used alone or with chemotherapy- used alone or with chemotherapy

D. Laser therapyD. Laser therapy

- uses an intense beam of light to destroy a - uses an intense beam of light to destroy a tumortumor

E. ImmunotherapyE. Immunotherapy

- attempts to bolster the body’s own immune - attempts to bolster the body’s own immune system against cancersystem against cancer