Pathology

Introduction to Histology;

Why is histology important?

Provides structural basis for gross anatomy (and many life sciences) and is essential for understanding function and pathological change

What are the four categories of tissue

Epithelial tissue, connective tissue, muscular tissue, nervous tissue

Epithelium consists of _______ of cells which perform many specialized functions

Sheets

Function of epithelium

Barrier internally and externally
Mechanical protection
Absorption/Secretion

What are the subdivisions of epithelium

Surface epithelium and glandular epithelium

What are specialized function of the epithelium mediated through

Structural modifications to their surface (microvilli, cilia)
Internal modifications (secretion)
Special types of junctions between cells

Tight junctions (occluding)

-found in tissues where a leak-proof seal is needed between adjacent cells.
-Very important in organs like the stomach and bladder.

Anchoring/adhering junctions (desmosomes)

Link cells together providing mechanical strength

Communicating (gap) junctions

Allow the movement of molecules between cells (free exchange)

Surface epithelia are classified by

1. Number of cell layers (simple or stratified)
2. Shape of surface cells (squamous, cuboidal, columnar)
3. Surface specializations (keratin, cilia, microvilli)

All epithelial cells rest on ________-

basement membrane

What epithelial cells are in the trachea

Stratified ciliated columnar

simple squamous epithelium

Function: Allows passage of materials by diffusion and filtration in sites where protection is not important; secretes lubricating substances in serosae.

Location: Kidney glomeruli, air sacs of lungs, lining of heart, blood vessels, and lymphatic vessels; lining of ventral body cavity(serosae)

simple cuboidal epithelium

Function: secretion and absorption

Location: Kidney tubules; ducts and secretory portions of small glands, ovary surface.

simple columnar epithelium

Function: Absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus (or reproductive cells) by ciliated action.

Location: nonciliated type lines most of the digestive tract (stomach to anal canal), gallbladder and excretory ducts of some glands; ciliated variety lines small bronchi, uterine tubes, and some regions of the uterus.

stratified squamous epithelium

Function: protects underlying tissues in areas subject to abrasion

Location: nonkeratinized type forms the moist lining of the esophagus, mouth, and vagina; keratinized type forms the epidermis of the skin, a dry membrane.

keratinized stratified squamous epithelium

epidermis of skin

stratified cuboidal epithelium

Function: protection

Location: Largest ducts of sweat glands, mammary glands, and salivary glands.

stratified columnar epithelium

Function: protection and secretion

Location: rare in the body; small amounts in male urethra and in large ducts of some glands

transitional epithelium

function: stretches readily and permits distension of urinary organ by contained urine

Location: lines the ureters, urinary bladder, and part of the urethra

psuedostratified ciliated columnar epithelium (with goblet cells)

Function:
Secretes substances, particularly mucus; propulsion of mucus by ciliary action
Location:
Male's sperm carrying duct; ciliated variety lines the trachea, most of the upper respiratory tract.

The goblet cell is described as a _______ gland.

unicellular exocrine

What cells are associated with the epithelium (surface cells)

Single secretory cells ex: goblet cell

Secretory cells embedded in underlying CT include:

Exocrine (duct) = Serous and mucus glands
Endocrine (ductless) = special secretory product (hormones)

What gives rise to exocrine or endocrine glandular tissue

proliferation of surface epithelial cells into the underlying CT

exocrine glands

secrete chemical substances into ducts that lead either to other organs or out of the body

-Serous secretory units stain dark
-Mucus secretory units stain pale
-Sero-mucus (mixed secretion)

What is the function of connective tissue

Framework of the body. Provides support and structure to organs.
-Energy reserve, insulation, medium for transport, vital in healing process

What do all CT's consist of

ECM (made of fibers and amorphous ground substance

What is the extracellular matrix made of?

protein fibers (elastic fibers, collagen fiber, reticular fiber and ground substance

Resident cells of connective tissue

fibroblasts, adipocytes, mesenchymal cells, fixed macrophages

Types of connective tissue fibers

collagen(high tensile strength - low elasticity), elastic (can stretch and recoil) reticular (provides delicate framework in lymph nodes, liver and spleen and around blood vessels and nerves

amorphous ground substance

Cells and fibers of CT are embedded in an amorphous ground substance composed of glycosaminoglycans (GAGs) and proteoglycans

Three types of adult connective tissue

1. Loose connective tissue (more cells than fiber)
2. Dense regular connective tissue (more fibers than cells) - fibers in alignment ex: tendon
3. Dense irregular connective tissue (more fibers than cells) - fibers arranged in multiple directions

Main function of adipose tissue

energy (white fat), padding, insulation/heat production (brown fat)

Three principle areas that muscle is found

-Walls of hollow organs
-Muscles associated with the skeleton
-Heart

Three types of muscle fibers

-Skeletal (striated)
-Cardiac (striated)
-Smooth

On a transverse section of skeletal muscle, what can you see?

Multiple, peripheral nuclei
-Cytoplasm packed full of myofibrils

On a longitudinal section of skeletal muscle, what can you see?

Peripheral nuclei, striated, long unbranched fibers, limited amount of CT between fibers

On a transverse section of cardiac muscle, what can you see?

Single central nucleus present in sectioned fibers, cross sections of fairly uniform size, lots of CT between fibers

In a longitudinal section of cardiac muscle, what can you see?

Central nucleus, striated, short branched fibers, abundant CT between fibers, intercalated discs

On a smooth muscle transverse section, what can you see?

Cross sections variable in diameter, only a few central nuclei

On a longitudinal section of smooth muscle what can you see?

Central nucleus, non-striated, short tapering fibers, limited CT between fibers

What kind of epithelium do your sweat glands have

simple cuboidal with secretory deposits - stratified cuboidal lining the ducts

merocrine glands

Exocrine glands that secrete without losing cellular material (produce and release product)

apocrine glands

Produce product and apical part of the cell schlufs off

Holocrine gland

Secretory cells disintegrate to deliver their accumulated product, oil-producing glands of the scalp

What makes of the extracellular matrix

fibroblasts

What are the main cells of adipose

adipocytes

What is the function of adipose tissue

Protects (cushions structures), stores fat, protection from extreme temperature changes, and insulates

What are infectious diseases caused by?

Bacteria, viruses, prions, parasites, fungi

Zoonoses

Diseases transmitted from animals to humans

ex: salmonella, rabies, cat scratch disease

What happened in the 1920s that killed most cattle in SE Africa

Rinderpest in Arabia - 90% of cattle died and large number of wild ungulates

What virus had 100% mortality rate in chickens in 1983

Chick/Penn/83/influenza virus - 17 million birds destroyed (16 million dollars)

What happened in 1999 that killed 1 million pigs?

Nipah virus - killed 1 million pigs in Malaysia - encephalitis post mortem

What killed 1/3 of the European population in 1348-51

Black death/plague - Yersinia pests (bacterial)

What killed 95% of the indigenous population in the new world in 1492-1550

Small pox

How many people died with the spanish flu? When was it?

1918-20, 20 million people died

What plant cause the great potato famine and when was it?

Fungus Phytophthora infestans - 1845
Ireland population when from 8.5 million to 6.5 million

Most diseases are ________

asymptomatic - infects others but individual will have no symptoms

When does bacterial flora become a problem?

When it moves somewhere in the body it doesn't belong - sepsis
ex: feces in the small intestine from trauma

What do bacteria use as a food source in herbivores

cellulose

How much of a rabbits daily energy comes from volatile fatty acids

20%

Epidemiology definition

The study of the spread of infectious disease within a community or population

What does the spread of a disease in a population depend on

Patients with active disease, symptomless carriers (livestock; salmonella), animal to animal transmission or animal to human transmission (zoonoses)
Food, water, soil
Reservoirs and sources
Immunity

What determines the outcome of any infection?

Relationship between host and microorganism

How does a host defend itself from infection

non-specific defense mechanisms (skin, normal flora, flushing of body fluids ex; crying/saliva, hostile environments (gut pH acidic), phagocytosis = neutrophils and macrophages

Specific defence mechanisms

Antibody response, cell mediated response, cytokines

Virulence

ability to produce disease

What factors affect the host/parasite balance

Genetic characteristics, immunity - naturally acquired and induced, hormonal status (pregnancy), nutritional status (malnourished = less immunity), Underlying infection, drugs (immune suppressive)

Innate immune response

A quick, general immune response that all living things are born with (non specific first line of defense)

Adaptive immune response

The response of antigen-specific B and T lymphocytes to antigen, including the development of immunological memory.

Soluble factors of innate immunity

Lysosome, complement, acute, phase proteins, iron binding proteins

Cells of the innate immune system

phagocytes, natural killer cells, granulocytes

Cells of the Adaptive Immune System

B cells and T cells

Does innate immunity have memory?

no memory

Does adaptive immunity have memory

yes, faster response upon second exposure

Interactions of organisms with host

1. Transient colonisation
2. Prolonged colonisation (colonization doesn't imply disease - colonizing organisms may replicate within the host
3. Replicating organisms infect tissues which may result in tissue damage = disease

Disease occurs when the interaction between ____ and the animal host results in a pathological process

Microbe

Pathogenesis of disease

Acquisition
Colonization
Invasion
Spread (through blood stream)
Damage (Clinical symptoms)
Resolution

Microbial virulence factors

substances or features of a microorganism that help it infect and cause disease

What do viruses, fungi and parasites have that aid in them causing disease?

Virulence factors (ex: rabies and anthrax have extremely high virulence factors)

Immunopathology

The study of disease states associated with overreactivity or underreactivity of the immune response

Most pathogens are ________ which means they cause disease when they get the chance

opportunistic

Viruses replicate within cells by

Subverting their metabolic activity

What does subverting a viruses metabolic activity do?

Re-directs them to the synthesis of new viral components - assemble into infectious particles usually killing the cell it infected
-Lesions are produced and disease spreads into target organ
-Virally infected cells may suffer damage from immune reactions (immunopathology!)

Common superficial fungal infections

Spores in environment grow into hyphal fungi multiply in the skin and utilize keratin
-Ring worm/ athletes foot

Mucous membrane infections

Thrush - yeast

Fungi gaining access to tissue can cause _____-

Subcutaneous infection

What do fungi do in the blood

cause sepsis

Pathogenic mechanisms of parasites

-Depends on life cycle
-Some require arthropod transmission
-Some may be very severe (malaria) or no symptoms (gut nematodes)
-Virulence factors are not well understood

How are infectious diseases diagnosed?

Clinically, laboratory, and imaging

Clinically diagnosing an infectious disease

Look at signs, presenting symptoms, look to see what the problem is

Laboratory diagnosis of infectious disease

Can be caused by more than one microorganism so need lab to confirm which one

Imaging diagnosis of infectious disease

Use of radiology and ultrasound

How can you control infectious disease?

Improving hygiene, nutrition and waste disposal
-Antiseptic techniques
-Sterilization, disinfection, pasteurization
-Vaccination
-Antimicrobial drugs (1940s and onwards)

What is antimicrobial therapy

Drugs used to treat bacterial, fungal, viral and parasitic disease - working by selective toxicity

selective toxicity

A drug that kills harmful microbes without damaging the host

Antibiotics are used for

Bacterial infections

Who invented the smallpox vaccine?

Edward Jenner - 1798 using cowpox

When was small pox eliminated?

1977