Transcript Slide 1

Tissues
Chapter 3
Histology
• Study of tissues (approximately 220 types!)
• Tissues: groups of highly specialized cells
performing functions that benefit the organism as
a whole
– Cells must be similar in structure & function and come
from similar embryonic origin
• Four Primary tissue types
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Epithelium (covering)
Connective (support)
Muscle (movement)
Nervous (control)
• Organs contain several tissue types, and
arrangement of tissues determines organ’s
structure & function
Primary Germ Layers
• All tissues & organs of the body develop from
one of three primary germ layers:
– Ectoderm (outside)
• Lining, skin, nervous
– Endoderm (inside)
• Organs, mucosae &
glands, linings of cavities
and tracts
– Mesoderm (middle)
• Connective tissue
(i.e. blood, bone) and most
muscle tissue
Extracellular Materials
• ECF: usually fluid, but can be more gel-like or
calcified (i.e. bone)
• ECF provides a medium for:
– Dissolving & mixing solutes
– Transporting substances
– Carrying out chemical reactions
Epithelial Tissue
• a.k.a. epithelium (“epithe” = laid on, covering)
• Lining, covering, and glandular tissue of the body
• Covers all free body surfaces and contains
versatile cells
• Nearly all substances that the body gives off or
receives must pass through epithelium
• Functions:
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Protection
Filtration
Absorption
Secretion
Characteristics of Epithelium
• Cells fit closely together to form continuous sheets – single or
multiple layers (desmosomes & tight junctions); little
extracellular materials
• Membranes always have one free (unattached) surface or edge
(apical surface) that is exposed to body’s exterior or to the
cavity of an internal organ (some have modifications like cilia
or microvilli)
• Basal surface (lower) of epithelium rests on a basement
membrane – structureless material secreted by both epithelial
cells and connective tissue cells that border the epithelium
• Epithelial tissues have no blood supply of their own
(avascular) and depend on diffusion from the capillaries in
underlying connective tissue for food and oxygen
• Regenerate easily (high mitotic rate)
• Have a nerve supply
• Derived from all three primary germ layers
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Classification of Epithelium
• Two names:
– 1st indicates relative number of cell layers
• Simple (one layer) or stratified (multiple layers) or pseudostratified
(looks like multiple layers)
– 2nd indicates the shape of its cells
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Squamous (flat)
Cuboidal (cube)
Columnar (shaped like columns)
Transitional (varies)
• Stratified epithelium is named based on cells at the
free surface!
• Arrangement reflects location and function
Types of Epithelial Tissue
• Covering & Lining Epithelium
– Simple Epithelia
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Simple squamous epithelium
Simple cuboidal epithelium
Simple columnar epithelium
Pseudostratified columnar epithelium
– Stratified Epithelia
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Stratified squamous epithelium
Stratified cuboidal epithelium
Stratified columnar epithelium
Transitional epithelium
• Glandular Epithelium
Epithelial Tissue ID Quiz
Tissues you need to
be able to identify:
• Simple squamous
• Simple cuboidal
• Simple columnar
• Stratified squamous
• Transitional
• Pseudostratified
Tissue/ cell parts you
need to know:
• Nucleus
• Apical (free) surface
• Basal surface
• Basement membrane
• Cilia
• Goblet cell
• Keratin
Simple Squamous Epithelium
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Single layer, flat shape
All cells attached to basement membrane
Fit closely together
Forms membranes where filtration or exchange of
substances by rapid diffusion occurs (absorption,
secretion, filtration)
• Ex: air sacs of lungs (O2 & CO2 exchanged), walls of
capillaries (nutrients and gases pass between the tissue
cells and blood in capillaries), form serous membranes
(serosae) – slick membranes that line ventral body
cavity and cover organs in that cavity
• Endothelium – lines blood vessels
• Mesothelium – lines body cavities and mesenteries
Simple Cuboidal Epithelium
• Single layer/cube shape
• Common in glands and their ducts
• Ex. Salivary glands and pancreas, walls of kidney
tubules, covers surface of ovaries
Simple Columnar Epithelium
• Single layer/column (tall) shape
• Often have goblet cells – produce lubricating mucus
• Ex: lines entire length of digestive tract from stomach to
anus
• Mucosae (mucous membranes): epithelial membranes
that line body cavities open to the body exterior
Pseudostratified Columnar Epithelium
• Appear to be multi-layered, but are actually one
single layer that rest on the basement membrane
• Nuclei appear at different heights and some cells
shorter than others
• Mainly functions in absorption and secretion
• Can be ciliated (pseudostratified ciliated columnar
epithelium)
• Also can have goblet cells
• Ex: respiratory tract – mucus produced by goblet
cells in this epithelium traps dust and other debris,
and the cilia propel the mucus upward and away
from the lungs
Stratified Squamous Epithelium
• Multiple layers, flat shape
• Most common stratified epithelium in body
• Cells at free edge are squamous, and those close to
basement membrane can be cuboidal or columnar
• Found in sites that receive a good deal of abuse or
friction
• Keratin – protein coating on apical surface (i.e.
skin)
– Can be keratinized or non-keratinized
• Ex. Esophagus, mouth, outer portion of skin
Non-keratinized
Keratinized
Stratified Cuboidal Epithelium
• Two cell layers with (at least) the surface cells being
cuboidal in shape
• Fairly rare in body; distribution extremely limited
• Mainly in ducts of large glands (larger ducts of
mammary glands, sweat and salivary glands, pancreas)
Stratified Columnar Epithelium
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Multiple layers/Columnar cells
Basal cells vary in size and shape, see multiple nuclei
Even less common in body; distribution extremely limited
Mainly in ducts of large glands
Ex. Urethra, pharynx
Transitional Epithelium
• Variable shapes
• Highly modified, sratified squamous epithelium
that forms the lining of only a few organs
– Urinary bladder, ureters, and part of the urethra
• Subject to considerable stretching
• Cells of basal layer cuboidal or columnar & cells at
free surface vary in appearance
• Not stretched: superficial cells rounded and
domelike
• Distended: epithelium thins and surface cells
flatten and become squamouslike
Distended
Glandular Epithelium
• Gland: one or more cells that make and secrete a
particular product
• Secretion: typically contains protein molecules in
an aqueous fluid
• Endocrine glands: ductless glands; secretions
(hormones) diffuse directly into the blood vessels
that weave through the glands (i.e. thyroid,
adrenals, pituitary)
• Exocrine glands: ducts; secretions empty through
ducts to epithelial surface (i.e. sweat & oil glands,
liver, pancreas)
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Connective Tissue
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Connects body parts
Found everywhere in body
Most abundant and widely distributed tissue
Primary functions:
– Protecting
– Supporting
– Binding together body
tissues
Connective Tissue Characteristics
• Three basic elements: cells, ground substance, fibers
– Extracellular matrix: ground substance + fibers
• Fibers made of protein (collagen is most abundant protein
in body – 25%)
• No free surface (connects!)
• Has nerve supply (except cartilage)
• Highly vascular
– except cartilage (avascular) & tendon (poorly vascularized)
• Matrix may be fluid, semifluid, gelatinous, fibrous, or
calcified (depends on ground substance)
– Secreted by connective tissue cells & adjacent cells
– ground substance: structureless; water plus some adhesion
proteins & large, charged, polysaccharide molecules
– Determines tissue’s qualities
Embryonic Origin
• Mesenchyme: undifferentiated connective tissue cells
in embryo
• All Connective tissue is derived from mesoderm!!
– How is this different from Epithelial tissue?
Embryonic Connective Tissue
• Embryo (0-2 months); Fetus (2 mos.-birth)
• Mesenchyme: almost exclusively in embryo; tissue from which
all connective tissue will eventually arise
• Mucous (Wharton’s Jelly): umbilical cord of fetus – gives
support
Connective Tissue Cells
• Mesenchymal cells become blast cells (immature)
• Blast cells undergo mitosis and secrete the matrix
• Mature cells do not divide & make matrix – just maintain what is
there
Connective Tissue Fibers
• Type of fiber depends on type of tissue
• Fibers made of proteins
• Types of fibers:
– Collagen fibers – tough & resistant to stretching/pulling forces;
bone, cartilage, tendons, ligaments
– Elastic fibers – strength & stretching; skin, blood vessels, lungs
(smaller than collagen fibers)
– Reticular fibers – collagen + glycoprotein; support in blood vessel
walls & form strong supporting network around fat cells, nerve
fibers, skeletal/smooth muscle fibers; form basement membrane
and framework of soft organs
Types of Connective Tissue
• All CT consist of living cells surrounded by a matrix
• Differences: special cell types, fiber types, # of fibers
• Types:
• Bone (Osseous)
• Cartilage
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Hyaline cartilage
Fibrocartilage
Elastic cartilage
• Dense Connective
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Dense regular
Dense irregular
Dense elastic
• Loose Connective
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Loose areolar
Adipose
Loose reticular
• Blood
Connective Tissue ID Quiz
Tissue types:
• Loose areolar
• Adipose
• Dense connective
• Cartilage
• Bone
• Blood
Parts:
• Fibroblast
• Fibers
• Nucleus
• Adipocyte
• Lipids (fats)
• Chondrocyte
• Lacuna(e)
• Osteocyte
• Canaliculi
• Haversian system (osteon)
• Red blood cell (erythrocyte)
• White blood cell (leukocyte)
• Platelet (thrombocyte)
Bone (Osseous Tissue)
p. 139 –
Bone chapter
• composed of osteocytes (bone cells) sitting in lacunae (pits)
• Surrounded by layers of very hard matrix of calcium salts &
collagen fibers
• Exceptional ability to protect & support other body organs
– Great strength & some flexibility
• Movement, storing minerals, houses blood-forming tissue,
stores lipids (yellow marrow)
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haversian system (osteon) – basic unit
canaliculi – small canals that supply nutrients
central canal – contains blood vessels and nerves
Periosteum surrounds central canal – made of dense irregular CT
Lamellae – rings of matrix (mineral salts & collagen)
Cartilage
• Less hard and more flexible than bone
• Chondrocyte: cartilage cells
• Hyaline cartilage (most widespread)
– Abundant collagen fibers hidden by a rubbery matrix with a
glassy, blue-white appearance
– Supporting structures of larynx (voice box), attaches ribs to the
breastbone, and covers the ends of many bones where they form
joints
– Makes up the fetal skeleton
– Epiphyseal (growth) plates in long bones during youth
• Fibrocartilage
– Highly compressible, forms the cushionlike disks between the
vertebrae of the spinal column
• Elastic Cartilage
– Found in structures with elasticity
– Supports external ear
Hyaline Cartilage
• No blood vessels (except perichondrium)
Fibrocartilage
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Bundles of collagen in matrix
Pubic symphysis, intervertebral discs, meniscus of knee
Support & fusion
No perichondrium
Strongest type: strength & rigidity
Elastic Cartilage
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Threadlike fibers in gel matrix
Support & maintains shape
Has perichondrium
Similar to hyaline, but more elastic fibers
– Strength & exceptional stretchability
• Epiglottis (“lid” on larynx), auditory tubes
Dense Connective Tissue
• Also called dense fibrous tissue
• Collagen fibers are main matrix element
• Fibroblasts (fiber-forming cells) manufacture the building
blocks of the fibers
• Forms long, ropelike structures
– Tendons: attach skeletal muscles to bones
– Ligaments: connect bones to bones at joints (contain more
elastic fibers than tendons)
• Also makes up lower layers of skin (dermis)
• Types:
– Dense Regular
– Dense Irregular
– Dense Elastic
Dense Regular Connective Tissue
• Closely packed bundles of collagen fibers running in same
direction – fibers regular and parallel
• Great resistance to tension
• Crowded between collagen fibers are fibroblasts that make
fibers & ground substance
• Found in tendons, ligaments, aponeuroses, and fascia
Dense Irregular Connective Tissue
• Randomly arranged collagen fibers & few fibroblasts
• Fascia, dermis of skin, periosteum, perichondrium, joint
capsules, membrane capsules around organs, heart valves
• Provides strength
• Places where pulling in various directions occurs (found in
sheets)
• Same structural elements as dense regular, just arranged
irregularly and with thicker fibers
Dense Elastic Connective Tissue
• Elastic fibers & fibroblasts
• Allows stretching of various organs and elasticity (returns to
original shape)
• Lungs, walls of trachea, arteries, bronchial tubes, true vocal
cords, and some ligaments
Loose Connective Tissue
• Softer, more cells and fewer fibers than any other connective
tissue type (*except blood)
• Types:
– Areolar Tissue
– Adipose Tissue
– Reticular Connective Tissue
Loose Areolar Connective Tissue
• All three types of fibers, semi-fluid ground substance, several
cells
• Most widely distributed connective tissue
• Soft, pliable – cushions and protects body organs
• Universal packing tissue and connective tissue “glue”
– Holds organs together and in proper positions
• Reservoir of water and salts for surrounding tissues
– All cells obtain nutrients from & release wastes into this “tissue fluid”
• Edema: areolar tissue in area soaks up excess fluid when area
is inflamed – area swells and becomes puffy
• Phagocytes scavenge for bacteria and debris and dead cells in
this tissue to destroy
Adipose Tissue
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Commonly called fat
Adipocytes: specialized to store triglycerides
Droplet of oil occupies most of fat cell & compresses nucleus
Subcutaneous tissue beneath skin – insulates body and
protects from bumps and extremes of heat & cold
• Cushions individual organs and stores fat for fuel if needed
• Newborns – brown fat (rich blood supply & more
mitochondria)
– Helps them maintain body temperature
Loose Reticular Connective Tissue
• Made of reticular cells (resemble fibroblasts) & reticular fibers
• Limited to certain sites – forms “stroma”
– internal framework that supports free blood cells (lymphocytes)
in lymphoid organs (i.e. lymph nodes, liver, spleen, bone
marrow)
• Binds together smooth muscle
Blood (Vascular Tissue)
• Plasma + formed elements (erythrocytes, leukocytes, thrombocytes)
• Blood plasma = nonliving, fluid matrix
– “fibers” – soluble protein molecules that are visible only during
blood clotting
• Transport vehicle for cardivoascular system
– Carries nutrients, wastes & respiratory gases; immunity; clotting
Muscle Tissue
• Highly specialized to contract and produce movement
• Types of muscle tissue:
– Skeletal Muscle
– Cardiac Muscle
– Smooth Muscle
Muscle & Nervous Tissue ID Quiz
Tissue types:
• Skeletal muscle
• Cardiac muscle
• Smooth muscle
• Nervous tissue
Parts:
• Nucleus
• Striations (bands)
• Intercalated disc
• Neuron
• Cell body
• Dendrite
• Axon
• Neuroglia
Skeletal Muscle Tissue
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Packaged by connective tissue sheets into organs
Attached to bones
Controlled movements/voluntary movements
Muscular System
Cells are long, cylindrical, multinucleate, have striations (stripes)
Cells called “muscle fibers” because they are elongated
Fibers run parallel to each other
Function: Motion, maintenance of posture, heat production
(maintaining temperature)
Cardiac Muscle Tissue
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Only in heart wall
Function: pump and propel blood
Involuntary
Striations, uninucleate
relatively short, branching cells that fit tightly together at
intercalated discs (attach cells end to end)
• Contain gap junctions that allow ions to pass freely from cell to cell
resulting in rapid conduction of electrical impulse across the heart
Smooth Muscle Tissue
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no striations visible
Involuntary muscle
Single nucleus, spindle-shaped (pointed at each end)
Stomach, uterus, blood vessels, airways, walls of hollow organs
(viscera) i.e. urinary & gall bladder
– Contracts: cavity becomes smaller (constriction)
– Relaxes: cavity dilates and enlarges (dilation)
• Peristalsis – wavelike motion keeps food moving through small
intestine
• Contracts more slowly than other types
Nervous Tissue
• Internal communication
• Found in brain, spinal cord, and nerves
• Two types of cells:
– Neurons: receive and conduct electrochemical impulses from
one part of the body to another
– Neuroglia: supporting cells that insulate, support, and protect
delicate neurons within the structures of the nervous system
Neurons
• Receive & conduct electrochemical impulses
• Two functional characteristics:
– Irritability
– Conductivity
• Cytoplasm drawn out into long processes
• Parts:
– Cell body – nucleus & organelles
– Dendrites – processes that receive impulse
– Axons – process(es) that send impulse
Neuroglia
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Supporting cells of the nervous tissue
Don’t generate nerve impulse
Often sites of tumors because they can divide
Insulate, support, protect neurons
Tissue Repair (Wound Healing)
• Tissue injury stimulates the body’s inflammatory and immune
responses and healing begins almost immediately
• Returning to homeostasis
• Tissue repair/wound healing occurs in two ways:
– Regeneration – replacement of destroyed tissue by the same
kind of cells (parenchyma cells – functioning cells of organ)
– Fibrosis – repair by dense (fibrous) connective tissue (scar tissue)
– (stroma – supporting cells of organ – connective tissue)
– Which type depends on:
• Type of tissue damaged
• Severity of injury
• Different tissue types have different capacities for renewal of
parenchyma cells
– During embryonic development, muscle & nervous become highly
differentiated and lose capacity for mitosis; epithelial and connective
tissues general have a capacity for renewal
Tissue Repair (Wound Healing)
1. Inflammation
– Nonspecific body response that tries to prevent further injury
– Inflammatory chemicals are released and make capillaries
permeable
– Fluid with clotting proteins seep into injured area from blood
– Clot is constructed to stop loss of blood and hold wound
together
– Scab forms where clot is exposed to air
Tissue Repair (Wound Healing)
2. Granulation Tissue
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Delicate pink tissue composed largely of new capillaries
Grow into damaged area from undamaged blood vessels nearby
Fragile & bleed freely (i.e. when scab picked)
Contains phagocytes that dispose of blood clot
Contains connective tissue cells (fibroblasts) that produce the
building blocks of collagen fibers (scar tissue) to permanently
bridge the gap
Tissue Repair (Wound Healing)
3. Regeneration & Fibrosis
– Surface epithelium regenerates across the granulation tissue
below the scab
– Scab detaches when surface epithelium has covered wound
– Fibrosis (scar) usually underneath regenerated epithelium
• Scar Tissue: strong, lacks flexibility, in ability to perform
normal tissue functions
• Adhesions can result
from fibrosis and cause
abnormal joining of
adjacent tissue (recent
surgery sites) – can cause
obstructions (abdomen)
Tissue Repair (Wound Healing)
• Tissue repair can be affected by:
– Nutrition
– Blood circulation
• Transport of oxygen, nutrients, antibodies, etc.
• Removal of tissue fluids, bacteria, and debris
– Age
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Young are better nutritionally
Better blood supply
Cells have higher metabolic rate
Cells & extracellular components change with age
Collagen/elastic fibers change with age