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Chapter 4A: Epithelial Tissue
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Unicellular Organisms:
◦ Entire organism consists of one cell
◦ Single cell is able to perform all necessary functions
for living
◦ Ex. Amoebas
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Multicellular Organisms:
◦ Organism consists of more than one cell
◦ Cellular Specialization occurs different cell types
perform different jobs
 Brain cell vs. muscle cell, etc…
Cell  Tissue  Organ  Organ System  Organism
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Tissues = Groups of cells similar in structure
and function
Histology= the study of tissues
The four types of tissues
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◦
◦
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Epithelial (coverings)
Connective (support)
Muscle (movement)
Nerve (control)
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A sheet of cells that cover a body surface or
lines a body cavity
◦ Form boundaries between different environments
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Functions:
◦
◦
◦
◦
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Protection
Absorption
Filtration
Excretion/Secretion
Sensory reception
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Locations:
◦ Skin
◦ Inner surfaces of the body
(lungs, stomach, intestine,
blood vessels)
◦ Lines cavities
◦ Forms glands
Cellularity: Epithelium is composed of tightly packed
cells with very little space between them
Special Contacts: cells form continuous sheets held
together at many points by lateral contacts such as
tight junctions and desmosomes
Polarity: All epithelia exhibit apical-basal polarity
◦ cell regions near the apical surface differ from those near the
basal surface
 Apical=upper free surface of cell that is exposed to the body
exterior or the cavity of the internal organ
 Basal= lower attached surface of the cell that is attached to
connective tissue by a non-cellular adhesive sheet known as
the basement membrane, consisting of the basal lamina and
the reticular lamina
The basement
membrane
reinforces the
epithelium,
helping it to
resist
stretching and
tearing forces,
and defines
the epithelial
boundary.
Avascular but innervated:
◦ Innervated= supplied by nerve fibers
◦ Avascular= contains no blood vessels
◦ Cells are nourished by substances diffusing from
blood vessels in the underlying connective tissue
Regenerative: rapidly replaces lost cells by cell
division
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Usually have 2 names
◦ 1st name = number of layers
 Simple Epithelia: composed of a single layer of cells
 Thin barrier; good for absorption and filtration (not protection)
 Stratified Epithelia: composed of 2 or more cell layers stacked
on top of one another
 Found in highly abrasive areas; good for protection
◦ 2nd name = shape of cells
 Squamous Epithelia: flat, scale-like cells; nucleus is a flat disc
 Cuboidal Epithelia: box-like cells; as tall as they are wide;
nucleus is a sphere
 Columnar Epithelia: tall and column shaped cells; nucleus is
elongated and close to the bottom of the cell
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Squamous
◦ Flattened
◦ Filtration &
absorption
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Cuboidal
◦ Box-like
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Columnar
◦ Tall
◦ Protection
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Single layer (simple) of flat cells (squamous)
◦ Cytoplasm is sparse in these cells
◦ Resemble “fried egg” from side or tile floor from top
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Functions
◦ Forms membranes
◦ Diffusion and filtration
 Structure allows for rapid exchange of material
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Locations:
◦ Usually lines body cavities
◦ Lines lungs and capillaries (O2/CO2)
◦ Kidney tubules
Found
wherever rapid
diffusion is a
priority!
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Single layer (simple) of cube-like (cuboidal)
cells
◦ As tall as they are wide
◦ Nucleus appears very spherical and stains dark
◦ Looks like a string of beads
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Function: secretion and absorption
Location:
◦ Common in glands and their ducts
◦ Walls of kidney tubules
◦ Covers the ovaries
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Single layer (simple) of tall cells (columnar)
◦ Oval or elongated nuclei
◦ Many contain cilia to propel particles or microvilli
(fingerlike extensions of plasma membrane) to
increase surface area
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Goblet cells are often found in this layer
(produce mucus)
Function: absorption and secretion
Location:
◦ Line digestive tract and gallbladder (nonciliated)
◦ Bronchi and uterine tubes (ciliated)
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Single layer of cells with different heights; all
rest on basement membrane but some do not
reach the apical free surface
◦ b/c not all the cells reach the surface, it gives the
impression that multiple layers are present though
they are not (hence “pseudo”)
◦ Nuclei will be at different levels
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Function: secretion and propulsion of mucus
Location:
◦ Male sperm-carrying ducts
◦ Trachea)
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Cells on free surface are squamous
Underlying cells are cuboidal or columnar
Function: protection of underlying areas
subjected to abrasion
◦ Regenerate from below with basal cells pushing
apically to replace the older surface cells
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Location:
◦ Skin’s epidermis
◦ Linings of the esophagus, mouth, and vagina (all
body openings)
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Stratified cuboidal
◦ Quite rare in the body
◦ Typically two cell layers thick
◦ Location:
 Ducts of some sweat and mammary glands (large
glands)
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Stratified columnar
◦ Rare in the body
◦ Location:
 Found in the pharynx and ducts of large glands
 Transition areas between two other types of epithelia
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Several cell layers, basal (bottom) cells are
cuboidal or columnar, surface cells are dome
shaped (appearance varies depending on the
degree of distension)
Function: Stretches to permit the distension
of the urinary bladder
◦ Filled with urine thins from 5-6 cell layer to 2-3
and dome-like apical cells flatten
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Location:
◦ Lines the urinary bladder, ureters, and part of the
urethra
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A gland is one or more cells that makes and
secretes (export) a particular product
Secretion= water-based fluid containing
proteins that is released from a gland
2 types:
◦ Endocrine glands= internally secreting glands;
release hormones directly into the blood to travel to
target organ
◦ Exocrine glands= externally secreting glands;
secrete their products onto body surfaces (skin) or
into body cavities using ducts (more numerous)
Chapter 4B: Connective Tissue
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Remember…the four types of tissues
◦
◦
◦
◦
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Epithelial (coverings)
Connective (support)
Muscle (movement)
Nerve (control)
Found EVERYWHERE in the body
◦ Most abundant of the 4 main classes
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Not as regenerative as epithelial tissue
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Connective Tissue Proper
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Cartilage
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Bone
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Blood
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Classes of C.T.
Protection, Insulation
Binding & Support,
Protection
Binding & Support,
Protection
Transportation of
substances in the body
Functions
Common Origin:
◦ All arise from Mesenchyme (an embryonic tissue)
Varying degrees of vascularity:
◦ Some tissue types are well vascularized
◦ Some have poor blood supply or are avascular
Extracellular Matrix:
◦ Other classes of tissues are composed mainly of
cells
◦ The main component of connective tissue is
nonliving extracellular matrix
 Surrounds the living cells
 Allows it to bear weight and withstand tension and
abuses that other tissues could not
3 Main Components of ALL Connective Tissue:
1. Ground substance – unstructured material that
fills the space between cells & makes up the
extracellular matrix; “C.T. Glue”
2. Fibers – located in the ground substance of
extracellular matrix; provides support
 Collagen – strong, flexible, but slightly elastic
 Found in tendons
 Most abundant
 Elastic – made of rubber-like protein call elastin; not as
strong, but very stretchy
 Found in skin, lungs, blood vessels, vocal cords
 Reticular – very thin, short, fine collagen fiber
 form supporting networks around small blood vessels
3 Main Components of ALL Connective Tissue:
3. Cells- each class of C.T. has a unique cell type
that exists in immature (“blast”) and mature
(“cyte”) form
Connective Tissue Proper Fibroblast, Fibrocyte
Cartilage Chondroblast, Chondrocyte
Bone Osteoblast, Osteocyte
Blood Hematopoietic Stem Cell
*Other cells will be found in C.T. also, such as fat cells
and those that respond to injury (WBC’s, mast cells,
macrophages)
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Connective Tissue Proper (least rigid)
◦ Loose Connective Tissue (fibers are not packed tightly)
 Areolar
 Adipose
 Reticular
◦ Dense Connective Tissue (fibers are packed more tight)
 Dense Regular
 Dense Irregular
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Cartilage (moderately rigid)
◦ Hyaline cartilage
◦ Elastic cartilage
◦ Fibrocartilage
Bone (most rigid)
Blood (Fluid)
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Areolar connective tissue
◦ Function: supports & binds body parts and tissues
together while allowing free movement; holds body fluid
(interstitial fluid); helps defend against infection
◦ Contains all three connective tissue fibers arranged
loosely
◦ Location: widely distributed throughout body
 Wraps and cushions organs, blood vessels, & nerves
 Surrounds glands
 Forms subcutaneous tissue (cushions and attaches skin to
underlying tissue)
Universal Packing Material Between Tissues
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Adipose connective tissue (fat tissue)
◦ Function: extremely high nutrient storing ability,
insulates against heat loss, and supports and
protects
◦ Location: anywhere that areolar C.T. is found
 Under skin, around kidneys, behind eyeballs, within
abdomen, and in breasts
◦ Local fat deposits serve nutrient needs of highly
active organs
◦ Minimal E.C. matrix; cells are packed closely
together
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Reticular connective tissue
◦ Reticular cells lie in a fiber network
◦ Function: Forms a soft internal skeleton that
supports other cell types
◦ Location: Very limited distribution
 lymph nodes, bone marrow, and the spleen
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Dense regular connective tissue
◦ Closely packed, PARALLEL collagen fibers with a few
elastic fibers
 Mostly fiber, little ground substance
 Structure of collagen fibers provides great resistance
to tension in ONE direction
 NOTE- collagen fibers are slightly wavy
◦ Function: Attaches muscles to bone or to other
muscles, and bone to bone
◦ Location: all tendons (muscle to bone), all ligaments
(bone to bone)
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Dense Irregular Connective Tissue
◦ Irregularly (not parallel; run in more than one plane)
arranged thicker collagen fibers with some elastic
fibers
◦ Function: Withstands tension in many directions
providing structural strength
◦ Location: dermis, digestive tract, fibrous joint
capsules, surround some organs
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Tough but flexible (more flexible than bone)
◦ Rigidity somewhere between dense connective
tissue and bone
◦ Withstands tension and compression
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Lacks nerve fibers, Lacks blood vessels
(avascular)  heals slowly when injured
Aging cartilage cells lose ability to divide
◦ Chondroblasts make new cartilage until skeleton
stops growing
 Cartilage hardens into bone over time
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Up to 80% water
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Hyaline Cartilage
◦ Most abundant type of cartilage in the body
◦ Function: Supports, reinforces, cushions, and
resists compression
◦ Locations: Forms the costal cartilage (between ribs
and sternum), embryonic skeleton, the end of long
bones, nose, trachea, and larynx
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Elastic Cartilage
◦ Function: Maintains shape and structure while
allowing flexibility
◦ Location: Supports external ear (pinna) and the
epiglottis
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Fibrocartilage
◦ Intermediate between Dense C.T. and Hyaline (least
rigid cartilage)
◦ Function: Provides strong support and absorbs
compression shock
◦ Location: intervertebral discs, pubic symphysis, and
discs of the knee joint
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More collagen fibers, inorganic calcium salts,
blood vessels, and lacunae (small spaces)
than cartilage
◦ Extremely rigid and hard
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Vascularized  heals faster than cartilage
Functions: Supports, protects, and provides
levers for muscular action
◦ Stores calcium, minerals, and fat
◦ Marrow inside bones is the site of hematopoiesis
(forms blood cells)
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Location: Bone
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Most atypical type of connective tissue
◦ Does not connect things or provide
support/structure
◦ Considered C.T. because it develops from the same
mesenchyme and consists of living cells in a
nonliving matrix
 Red and white cells in a fluid matrix (plasma)
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Location: within blood vessels
Function: transport of respiratory gases,
nutrients, and wastes
Chapter 4C: Nervous & Muscle Tissue
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Contains 2 types of cells
◦ Neurons: highly specialized nerve cells that
generate and conduct electrical impulses
◦ Neuroglia-supporting cells: support, insulate, and
protect neurons
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Function: Transmits electrical signals from
sensory receptors to effectors
◦ Regulates and controls body functions
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Location: Throughout the nervous system
◦ brain, spinal cord, and peripheral nerves
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Highly cellular
Well vascularized
Function: Responsible for movement
◦ Contractile in nature
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3 Types:
◦ Skeletal
◦ Cardiac
◦ Smooth
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Long, cylindrical, multinucleate cells with
obvious striations (banding); no branching
Function: Initiates and controls voluntary
movement(pull of bone and skin to produce
movement); locomotion; manipulation of the
environment
Location: skeletal muscles that attach to
bones or skin
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Cylindrical cells with branching, striated,
uninucleate cells interlocking at intercalated
discs (junctions between cells)
Involuntary Muscle not under our conscious
control
Function: Propels blood into circulation
through all parts of the body
Location: walls of the heart only
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Sheets of spindle-shaped cells with central
nuclei that have no striations
Involuntary Muscle not under our conscious
control
Function: Propels substances along internal
passageways (i.e. peristalsis)
Location: walls of hollow organs; digestive
and urinary tract organs; uterus; blood
vessels
Occurs through 1 of 2 methods:
 Regeneration: replacement of destroyed
tissue with the same kind of tissue
 Fibrosis: repair by dense fibrous connective
tissue (scar tissue)
 Determination of method
◦ Type of tissue damaged
◦ Severity of the injury
◦ Nutrition, Circulation, Age of person
Strong
Epithelial
Areolar
Dense Irregular
Blood
Bone
Weak
Smooth Muscle
Dense Regular
* No Regenerative Capacity *
Cardiac Muscle
Nervous Tissue
Skeletal Muscle
Cartilage