Transcript A&P ch. 4 - Catherine Huff`s Site

Tissues: Living
Communities
Chapter 4
Introduction
• Since cells are differentiated, they have
lost ability to perform all metabolic
functions required to sustain life as an
isolated entity.
• Cells exist in cooperative communities in
multicellular organisms
• Cells of similar type and function cluster
together to form tissues.
Classification of Tissues
• Epithelial tissue
• Covers and lines
• Connective tissue
• Provides support
• Muscle tissue
• Enables movement
• Nervous tissue
• Controls work
Classification continued
• Most organs contain all 4 tissue types.
• The study of microscopic structures of
tissues and organs is called histology or
microscopic anatomy.
• What is gross anatomy?
Epithelial Tissue
• Composed of sheets of cells that cover
and line other tissues.
• Bladder, mouth, blood vessels, thorax,
etc.
• Have an exposed surface that affords
access to the surrounding environment or
to the inner openings of chambers and
ducts.
• Acts as interface layer that separates and
defines the beginning and ending of
different types of tissues.
Epithelial functions
•
•
•
•
Acts as protection for underlying tissues
Filter of biochemical substances
May be absorptive
May play an important role in sensory
input
• Secretion and excretion of biochemical
substances
• Epithelia that do this are called
glandular epithelia
• Individual glandular epithelia are goblet
cells.
Characteristics of Epithelia
• Organized into tightly packed groups that form
sheets of tissue.
• Can be composed of single layer or multiple layers
depending on location.
• Epithelial cells share the following characteristics:
• Polar - Each epithelial cell has an apical
surface and a basal surface
• Apical surface faces the lumen or body
cavity
• Basal surface faces the underlying
connective tissue
• Lateral surfaces are connected to neighboring
cells by junctional complexes
• Epithelial cells are avascular
• Most epithelial cells are innervated
Epithelial Tissue: Cellular Attachments
• Epithelial cells are held together in many ways
• Between the cell membranes of adjacent cells are channels that
carry nutrients to the cells and waste away
• Junctional Complexes – specialized attachments between
epithelial cells
• 3 major types:
• Desmosomes
• Welded plaque
• Tough, resist tension and stretching (like Velcro)
• Skin, heart, uterus
• Gap junctions
• Cytoplasm continuous
• Exchange ions, nutrients – quickly transmit signals
through connexons
• Cardiac, smooth muscles
• Tight junctions
• Nothing can penetrate
• Prevent leakage
Epithelial Cells: Basement Membrane
• Foundation of epithelial cells
• Meshwork of fibers that cements epithelial cell to
underlying connective tissue (CT)
• Also called basal lamina
• Varies in thickness
• Where might thickness vary?
• Helps prevent cell from being torn off by intraluminal
pressures
• Acts as a partial barrier between epithelial cell and
underlying CT – substances have to travel through
basement membrane to get in and out of epithelial cells.
Surface Specialization
• Surfaces vary depending on location in body and
function
• May be smooth or contain microvilli-fingerlike
projections, or cilia-hairs
• If the cell contains microvilli, it is said to have a
brush border.
• Brush border helps to increase surface
area, which aids in absorption. (can add up
to 20 times of surface area).
• Skin may have keratin-waterproof substance
• Keratin may accumulate as cell matures and
moves from basal layer to superficial layer of
integument.
Classifications of Epithelia
•
Characterized by 3 characteristics
• Number of layers of cells
• Single layer is called simple
• Found in protected parts of body because
provide minimal protection to underlying
structures
• More than one layer is called stratified.
• Thicker and stronger and are on parts of
body that are subjected to mechanical or
chemical stress.
• Shape of cells
• Based on shape that is on exposed or luminal
surface
• Squamous, cuboidal, and columnar
• Presence of surface specializations
• Keratinized, ciliated, etc.
Simple Squamous Epithelium
• Fragile and thin
• Found lining surfaces involved
in the passage of either gas
or liquid (lining of lungs, kidneys)
• Flat and smooth
• Mesothelium – lining of chest
(pleura), abdomen (peritoneum),
and pericardium
• Endothelium – lining of blood
vessels
Simple Cuboidal Epithelium
• Single layer of cube-shaped
cells
• Round, dark-staining nuclei
aligned in a single row
• Occurs in areas of the body
where secretion and absorption
take place
• Surface of ovaries, glands, lining
of ducts of liver, kidneys,
pancreas
Simple Columnar Epithelium
• Elongated and closely packed
together - thicker
• Nuclei aligned in a row at the
base of the cell near the
basement membrane
• Line the GI tract from stomach
to rectum
• absorptive cell- apical surface is blanketed by
dense microvilli that maximize absorption by
increasing surface contact with nutrient-filled
lumen.
• goblet cell- manufacture and store mucus for
lubrication
• Found in many excretory ducts
Stratified Squamous Epithelium
• Multilayered
• Occur in areas of the body
subject to mechanical
and chemical stresses
• Mouth, esophagus, vagina,
rectum
• Continually being worn
away or sheared off
• Replaced by cells from a
deeper layer
Stratified Cuboidal Epithelium
• Usually two layers of
cuboidal cells
• Found primarily along
large excretory ducts
• Salivary glands,
mammary glands,
sweat glands
Stratified Columnar Epithelium
• Found only in select parts
of the respiratory,
digestive, reproductive
systems and along some
excretory ducts
• Rare
• Function in secretion and
protection
Pseudostratified Columnar
Epithelium
• “False” stratified – truly simple
• Cell nuclei are found at different levels
across the length of the tissue
• Some cells do not reach luminal
surface but all attach to basement
membrane.
• Usually ciliated
• Found in respiratory tract and in
portions of male reproductive tract
• trachea
Transitional Epithelium
• Stratified epithelium
• basal layer of cuboidal or columnar cells
• superficial layer of cuboidal or squamous
cells
• Ability to stretch - found in areas
where changes in volume occur
• Bladder, ureters, urethra
• As epithelia stretches, layers often
thin depending on how much volume
is present
• Also form a leak-proof barrier
Glandular Epithelia
•
•
•
Gland- a cell or group of cells that have ability to manufacture
and discharge a secretion.
Secretions- specialized protein molecules that are produced
in the RER, packaged by the golgi and discharged from the
cell.
Glands can be organized by factors:
• Presence or absence of ducts
• Endocrine vs. Exocrine
• Number of cells that compose them
• Unicellular vs multicellular
• Shape of secreting ducts
• Simple or compound
• Complexity of glandular structure
• Tubular, acinar, tubuloacinar
• Type of secretion made
• Mucoid or serous
• Manner in which secretion is stored and discharged
• Merocrine, apocrine, or holocrine
Endocrine Glands
• No ducts
• Blood stream delivers secretions to entire body
• Secrete hormones
• Regulate body functions (growth, maturity, sex cycle)
• Part of Endocrine System
Exocrine Glands
• Contain ducts (except for Goblet cells)
• Have local effect
• Salivary
• Pancreas, liver (digestive enzymes)
• Musk (scent)
• Sweat
• Anal (scent glands)
Unicellular Exocrine Gland:
Goblet Cell
• Ductless
• Opens into GI, respiratory
tracts, conjunctiva
• Composed of modified
columnar epithelial cell
• Secretes mucin: mixed with
water → mucus
Multicellular Exocrine Glands
• Contains:
• 1) secretory unit
• Secretory unit usually surrounded
by connective tissue rich in blood
vessels and nerve fibers
• 2) a duct
• May be surrounded by
myoepithelial cells that assist with
the discharge of secretions into
the glandular duct
Classification of Multicellular
Exocrine Glands: Shape
• Based on shape and number of tubes
Classification of Exocrine Glands:
Manner of secretion
• Merocrine
• glands package their secretions and release
them via exocytosis as they are manufactured
• Majority of glands
•
(ex: pancreas, sweat, salivary)
• Apocrine
• glands store their secretions and then release
the top part (apex) of the cell into the duct
system
•
(ex: mammary, some sweat)
• Holocrine
• glands store their secretions and then release
the entire contents of the cell
•
(ex: sebaceous)
Classification of Exocrine
Glands:Type of Secretions Produced
Type of secretion produced
• Serous secretions
• Watery
• Contain a high concentration of enzymes
• Pancreatic secretion
• Mucous secretions
• Thick, viscous
• Mucus membranes (GI, resp)
• Composed of glycoproteins
• Mixed exocrine glands contain both
mucous and serous components
Connective Tissue
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•
•
•
•
Found everywhere in the body and represents most abundant tissue
by weight.
Some systems are almost exclusively composed of connective tissue
• Skeletal, integumentary
• Appearance varies.
Is derived from mesoderm, and composed of nonliving extracellular
matrix- matrix surrounds and separates the cells providing important
structural and nutritional support to epithelial cells. Is combination of
extracellular fibers and ground substance.
Form and function may be different.
• Reserve for energy
• Protection
• Provides framework of structural support
Is vascularized.
• Level of vascularity varies among connective tissue type.
Connective Tissue Components
•
All connective tissue is composed of distinct components
• 1. Extracellular fibers
• Collagenous
• Reticular
• Elastic
• 2. Ground substance
• 3. Cells
• Fixed cells
• Fibroblasts
• Adipocytes (fat cells)
• Reticular cells
• Wandering cells
• Mast cells
• Leukocytes (white blood cells)
• Macrophages (fixed and wandering)
Connective Tissue Components
Connective Tissue Components:
Ground Substance
• An amorphous, homogenous material that
ranges from liquid to gel to solid.
• Composed of glycoproteins called
glycosaminolglycans (GAGs)
• Is medium through which cells exchange
nutrients and waste with the bloodstream.
• Acts as shock absorbing cushion and
helps to protect underlying delicate cells.
• Serves as obstacle for invading
microorganisms.
Fibers of Connective Tissue
• Collagenous:
• Strong and thick.
• Composed of collagen.
• Organized into bundles
• Found in tendons and ligaments that
are continuously being pulled and
stretched.
• Sometimes called white fibers
• Density and arrangement can vary.
• Loose to dense.
Fibers of Connective Tissue
• Reticular:
• Composed of collagen, but are not thick
• Thin and delicate and branched into
complicated networks.
• Form support for around other cellular organs
like endocrine glands.
• Elastic:
• Composed primarily of elastin.
• Are branched to form networks
• Lack tensile strength of collagenous fibers.
• Can stretch and contract.
• Found in vocal cords, lungs, blood vessles.
• May be referred to as yellow fibers.
Major Cell Types of Connective
Tissue
• Fixed Cells:
• Remain in the connective tissue
• Fibroblast: secrete fibers and ground substance
of particular matrix.
• Can reproduce and are metabolically active.
• Called based on location
• Chondroblast, osteoblast, etc.
• As mature, cells are less active and are
called –cytes. Can revert back though if
more matrix is needed.
• Chondrocyte, osteocyte, fibrocyte
• Fixed cells continued.
• Adipose cells/Adipocytes:
• Found throughout connective tissue
• Form adipose tissue.
• Filled with lipid or fat.
• Reticular Cells:
• Form net-like connections through
cells
• Involved in immune response and
manufacture of reticular fibers.
• Transient or Wandering Cells
• Move in and out of connective tissue as
needed.
• Leukoctyes: white blood cells
• Found in blood and move into connective
tissue during periods of infection.
• Important in immune function.
• Mast cells: carry histamine and heparin which
initiate inflammatory response when released
into tissue
• Usually found near blood stream where can
mount response.
• Wandering cells continued..
• Macrophages: phagocytotic scavengers
that may be either fixed or transient in
connective tissue.
• Engulf microbes, dead cells and
debris
• What digests the cell?
• Given different names depending on
locatons
• Kupffer cells, microglial cells,
histiocytes.
Types of Connective Tissue
• Categorized as:
• Loose
• Areolar
• Adipose
• Reticular
• Dense
• Regular
• Dense irregular
• Elastic
Areolar Tissue
• Most common type of connective tissue
• Found everywhere in body
• Acts to support and cushion organs and other
delicate structures.
• Moderately elastic but tears easily compared to
other connective tissue.
• Has “open” spaces
• Filling of spaces during trauma is called edema
• Pitting edema- when tissue leaves pits in tissue
after being compressed.
• Viscous ground substance
Adipose Tissue
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•
•
•
Commonly known as fat.
Part of areolar tissue in which adipocytes dominate.
Highly vascularized
Cells expand based on amount of lipid being
stored.
• Important energy store.
• May be classified as:
• White:
• Found throughout body
• Brown:
• Found in newborns and hibernating animals
• Specialized form plays role in temperature
regulation
Reticular Connective Tissue
• Resembles areolar connective tissue but
only contains reticular fibers
• Found in limited sites of body
Dense Regular Connective
Tissue
• Tightly paced, parallel collagen fibers
• Tremendous tensile strength in one
direction.
• Makes up tendons and ligaments
Dense Irregular Connective
Tissue
• Collagen fibers in thicker bundles than those in
regular connective tissue.
• Can withstand force from many different directions.
• Found in dermis and fibrous coverings.
• Forms tough capsule of joints.
Elastic Connective Tissue
• High concentration of elastic fibers that is
extremely flexible.
• Found in few regions of body.
• Stomach, large airways, bladder, etc.
Specialized Connective Tissues
• Cartilage
• Hyaline Cartilage
• Elastic Cartilage
• Fibrocartilage
• Bone
• Blood
Cartilage
• Tough, specialized connective tissue.
• May be called gristle.
• More rigid than dense connective tissue, more
flexible than bone.
• Does not contain nerves.
• Can take a great deal of compression.
• Composed of cells (chondrocytes) and matrix.
• 3 types of cartilage:
• Hyaline cartilage
• Elastic Cartilage
• Fibrocartilage
Types of Cartilage
• Hyaline Cartilage
• Most common type of cartilage found in body.
• Found as articular cartilage at end of long
bones and joints and connects ribs to the
sternum.
• Most rigid type of cartilage.
• Elastic Cartilage
• Similar to hyaline cartilage but contains elastic
fibers
• Can withstand repeated bending.
• Found in pinnae
Types of cartilage continued
• Fibrocartilage
• Found merged with hyaline cartilage
and dense connective tissue.
• Found between vertebrae and spine
Bone
• Also called osseous connective tissue
• Hardest and most rigid type of connective
tissue
• Is well vascularized
• Provides protection.
• Structure
• Ground matrix - osteoid – calcium
phosphate and collagen fibers
• Haversian canals – channels in bone
that carry blood supply and nerves
• Periosteum – fibrous membrane that
covers the bone
Blood
• Most atypical type of connective
tissue.
• Composed of specialized cells:
• Erythrocytes (red blood cells)
• Leukocytes (white blood cells)
• Thrombocytes (platelets)
Membranes
• Epithelial and connective tissue may be
linked to form membranes.
• Are thin, protective layers that line body
cavities, separate organs and cover
surfaces.
• Four common epithelial membranes are:
• Mucous
• Serous
• Cutaneous
• Synovial
Mucous Membranes
• Always found lining organs that have connection to
outside environment.
• Esophagus, mouth, colon, etc.
• Produces protective and lubricating mucous
• Play role in monitoring and controlling what enters
into body and form barrier.
• How are mucous membranes important to us?
• CRT
• Are very absorptive
• Buprenex
Serous Membranes
• Also called Serosa
• Line walls and cover organs that fill closed body
cavities
• Characterized by continous sheet that is doubled
over to form two layers with a narrow space.
• Remember parietal vs. visceral?
• Fluid is thin and watery (a transudate).
• Large amount of fluid is called effusion.
• Fluid in abdomen is termed ascites.
• Adhesions are connections between parietal
and visceral layers.
Cutaneous Membranes
• The integument
• What else is this called?
• Perpetually exposed to environment.
• Composed of keratinized stratified
squamous epithelium called epidermis
• Epidermis is attached to underlying
Dermis.
Synovial Membranes
• Line the cavities of joints
• Contain no epithelium
• Manufacture synovial fluid that fills the joint
spaces and reduces friction and abrasion
at the ends of bones.
Muscle Tissue
• Uniquely designed for contraction.
• Composed of myosin and actin
• Three types of muscle tissue:
• Skeletal
• Smooth
• Cardiac
Skeletal Muscle
• Large and numerous cells
• Usually controlled by conscience thought
therefore is voluntary.
• Are striated or striped
• Held together by loose connective tissue.
Smooth Muscle
• Composed of small spindle-shape cells
that lack striation or bands and appear
smooth.
• Can not be consciously controlled.
• Found in walls of hollow organs
Cardiac Muscle
• Possesses ability to contract even when
neural input has been altered.
• Exists only in the heart.
• Completely involuntary.
• Cells are smooth and only contain one
nucleus
• Branches to form complex network.
• Are striated and connected to other cells
via an intercalated disk
• Contract at set rate.
Nervous Tissue
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•
•
Neural tissue is designed to send and receive electrical
and chemical signals.
Found in brain, spinal cord, and peripheral nerves
Composed of two cell types
• Neurons
• Longest cells in body.
• Composed of three parts
• Cell body (perikaryon)
• Cytoplasmic extensions (dendrites)
• Long single extension (axon)
• Forms connections with many other tissues
• Sensitive to electrical and chemical changes
• Neuroglial cells
• Found in greater numbers than neurons
• Do not transmit impulses
• Are supportive to the neurons
Tissue Healing and Repair
• Body’s initial response to injury is inflammation.
• Repair includes organization of granulation tissue
and regeneration of lost tissue or formation of scar
tissue
• Inflammation:
• Area generally becomes swollen, red and hot.
• Sometimes is decreased function in that part.
• This isolates area to prevent further damage
• Inflammation is not same as infection.
Steps in the Process of
Inflammation
• 1. Inflammation begins and then
vasodilation. Blood flow and oxygen and
nutrient supply is increased to area.
• 2. Swelling occurs
• 3. Clot formation takes place
• 4. Debris is removed by phagocytic cells
• 5. Histamine and Heparin help to reduce
swelling and heat.
Organization: The formation of
Granulation Tissue
• New tissue is formed called granulation
tissue
• Composed of collagen fibers that has
been manufactured by fibroblasts.
• If granulation tissue becomes too thick, will
be called proud flesh.
• Granulation tissue is slowly replaced by
fibrous scar tissue
• Helps to pull wound closed.
• Is less flexible than normal tissue
Proud Flesh
Classifications of Wound Healing
• First intention:
• Wound edges are held closed
• Usually by sutures
• Skin forms a primary union without formation of
granulation tissue or significant scarring
• Second Intention:
• Edges of wound separated
• Granulation tissue forms to close gap; scarring
results
• Third Intention:
• Contaminated wound left open until
contamination is reduced and inflammation
subsides; later closed by first intention; also
called delayed primary closure
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