Chapter 15 The Urinary System Biology 112 Tri-County Technical College Pendleton, SC.
Chapter 3--Tissues Biology 110 Tri-County Technical College Pendleton, SC.
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Transcript of Chapter 3--Tissues Biology 110 Tri-County Technical College Pendleton, SC.
Chapter 3--Tissues
Biology 110
Tri-County Technical College
Pendleton, SC
Definition and Types
Tissue is group of cells that are “similar” in structure and function
There are four primary tissue types in the human body: Epithelium Connective Nervous Muscle
Epithelial Tissue Function
Is the lining, covering, and glandular tissue of the body
Functions include: Protection, absorption, filtration, and secretion
Epithelium has some special characteristics Cells fit close together to form continuous
sheets Neighboring cells bound together by cell
junctions including desmosomes and tight junctions
Epithelial Functions, ctd.
Membranes all have ONE free (unattached) surface or edge This apical surface exposed to body’s exterior
or to cavity of internal organs May be slick/smooth or covered with
microvilli or cilia Lower surface rests on BASEMENT
MEMBRANE-structureless material secreted by cells
Epithelial cells have NO blood supply of their own (avascular)-depend on diffusion from capillaries in underlying connective tissue
Classifying Epithelium (layering)
Each epithelium is given two names First indicates relative number of cell
layers it has Second describes the shape of its cells SIMPLE is composed of only ONE layer
of cells STRATIFIED is composed of MORE than
one cell layer Stratified named for cells at free surface and
NOT those resting on basement membrane
Epithelium Classification, ctd.
SQUAMOUS epithelium cells are flattened like fish scales
CUBOIDAL epithelium cells are cube-shaped like dice
COLUMNAR epithelium cells are shaped like columns
Terms describing arrangement and shape are combined to describe epithelium fully
Use arrangement name first and shape name second
Simple Squamous Single layer of thin squamous cells resting
on basement membrane Usually forms membranes where filtration
or exchange of substances by rapid diffusion occurs
Composes air sacs of lungs, walls of capillaries, and the SEROUS MEMBRANES (serosae), the slick membranes that line ventral body cavities and cover organs in that cavity
Simple Cuboidal
ONE layer of cuboidal cells resting on BM Common in glands and their ducts
Salivary glands and pancreas for examples Forms wall of kidney tubules and covers
surface of the ovaries
Simple Columnar ONE layer of columnar cells resting on BM Tall cells that fit closely together Specialized for absorption and secretion GOBLET CELLS often found in this
epithelium type—produce lubricating mucus Line entire digestive tract from stomach to
anus Epithelial membranes that line body cavities
open to body exterior called MUCOSAE or mucous membranes
Pseudostratified Columnar All pseudostratified columnar epithelium
cells rest on basement membrane Some shorter than others and their nuclei
appear at different heights above BM Results in psuedo (false) impression that its
stratified Specialized for absorption and secretion Ciliated variety lines most of respiratory
tract Mucus produced by GC traps dust/debris
and cilia propel mucus upward away from lungs
Stratified Squamous Most common stratified epithelium in body Cells close to edge are squamous whereas
cells close to BM are cuboidal/columnar Usually consists of several layers of cells Found in sites that receive abuse or friction Esophagus, mouth, and outer portion of
skin
Stratified Cuboidal & Columnar
Stratified Cuboidal usually 2 layers thick Found along ducts of sweat glands and
larger ducts of mammary glands Stratified Columnar basal cells vary in size
and shape Provides protection along portions of
pharynx, epiglottis, urethra, anus, salivary gland ducts, and along few large excretory ducts
Both are fairly rare in the human body
Transitional Epithelium
Is highly modified stratified squamous epithelium that forms lining of only few organs
Found in urinary bladder, ureters, and part of urethra
Found where “stretching” is necessary Basal cells are cuboidal/columnar while those at
surface vary in appearance Ability of cells to “slide past” each other and
change shape allows “stretching” Ureter wall/urethra/urinary bladder…enough said
Glandular Epithelium Gland consists of one or more cells that
make/secrete particular product (secretion) Usually proteins in aqueous fluid
Two major types of glands form from epithelial sheets
ENDOCRINE glands lose connection to surface; called “ductless glands” Their secretions (hormones) diffuse directly
in blood vessels that run through the glands THYROID, ADRENALS, PITUITARY,
ETC.
Glandular Epithelium, ctd. EXOCRINE glands retain their ducts and
their secretions empty through ducts to epithelial surface
Glands located both internally/externally Sweat and oil glands Liver and pancreas (be careful with
pancreas, it also has endocrine function)
Connective Tissue Overview
Connects body parts and is most abundant and widely distributed of tissue types
Connective tissue has some common characteristics
Most are well vascularized (good blood supply) but there are exceptions Tendons and ligaments have poor blood
supply Cartilages are avascular
As result, these structures heal very slowly (if at all) when injured
CT Overview, ctd. Connective tissues composed of many different cell
types plus varying amounts of nonliving substances found outside cells called EXTRACELLULAR MATRIX Is what makes connective tissue so different
Matrix produced by CT cells and secreted to exterior May be liquid, semisolid/gel-like, or very hard
Because of EC matrix, CT able to stand stretching and other abuses (abrasion) that no other tissue could endure
As always, there are exceptions
CT Overview, ctd. Fat tissue (adipose) mostly cells with soft
EC matrix Bone and cartilage tissue has very few cells
and large amounts of hard EC matrix which makes them very strong
Various types/amounts of fibers deposited in and form part of EC matrix
Collagen (white) fibers, Elastic (yellow) fibers, and Reticular (fine collagen) fibers Made by CT cells and secreted to outside
CT Overview, ctd. Connective tissue performs many
functions: Protecting, Supporting, & Binding together other body tissues
All CT consist of living cells surround by a matrix
Their major differences reflecdt fiber type and number of fibers in their matrix
From the overview to the specific-let us discuss the Connective Tissue
Bone Tissue Often called “osseous tissue” Composed of bone cells in cavities called
LUCUNAE Surrounded by layers of very hard matrix
containing calcium salts and large numbers of collagen fibers
Because of this hardness, bone has exceptional ability to protect/support other body organs
Hyaline Cartilage Less hard and more flexible than bone Hyaline cartilage is most widespread Has abundant collagen fibers hidden by
rubbery matrix with blue-white appearance Forms supporting structures of larynx
(voice box), attaches ribs to breastbone, and covers ends of bones where they form joints
**skeleton of fetus made of hyaline cartilage
More Cartilage…Yeah!!
ELASTIC cartilage found where structure with elasticity desired Supports external ear
FIBROCARTILAGE highly compressable Forms cushionlike disks between vertebrae of
spinal column
Dense Fibrous Tissue Also known as Dense Connective Tissue Has collagen fibers as main matrix Crowded between collagen fibers are rows of
FIBROBLASTS (fiber-forming cells) Forms strong, ropelike structures such as tendons
and ligaments TENDONS attach skeletal muscles to bone Ligaments connect bone to bone at joints
More stretchy/contains more elastic fibers
Makes up lower layers of skin (arranged in sheets)
Areolar Tissue
Also known as Loose Connective tissue & is most widely distributed CT variety
Soft & pliable tissue that cushions/protects body organs it wraps
Functions as universal packing tissue and “glue” because it helps hold internal organs together and in their proper positions
Soft layer of areolar tissue (LAMINA PROPRIA) underlies all mucous membranes
Areolar Tissue, ctd. Fluid matrix contains all types of fibers in
loose network Provides reservoir of water and salts for
surrounding tissues **Essentially all body cells obtain their
nutrients from and release their wastes into this “tissue fluid”
When body region inflamed, areolar tissues in area soak up excess fluid like sponge and area swells and becomes puffy This condition is called EDEMA
Adipose Tissue
Is an areolar tissue in which fat cells predominate Glistening drop of fat occupies most of cell’s
volume Often called “signet ring cells” Forms subcutaneous tissue beneath skin
Insulates body Protects some organs individually Kidneys surrounded by capsule of fat; cushions
eyeballs in sockets
Fat “depots” in body (hips/breasts) store fat (fuel)
Reticular Connective Tissue
Consists of delicate network of interwoven reticular fibers associated with RETICULAR CELLS which resemble fibroblasts
Limited to certain sites Forms STROMA (bed/mattress) which is internal
supporting framework Stroma can support many free blood cells (mostly
lumphocytes) in lymph organs such as lymph nodes, spleen, and bone marrow
Blood Connective Tissue Blood (vascular tissue) composed of blood
cells surrounded by nonliving matrix (blood plasma)
Fibers are soluble protein molecules that become visible only during blood clotting
Transport vehicle for cardiovascular system
Carries nutrients, wastes, respiratory gases, and many other substances throughout body
Nervous Tissue Functional unit is the NEURON Neurons receive and conduct electrochemical
impulses from one part of body to another IRRITABILITY and CONDUCTIVITY are two
major functions of nervous tissue Neurons may be quite long (up to 3 feet) because
cytoplasm may be drawn out into extensions Neurons along with supporting cells (called glial
or neuroglial cells that insulate, support, and protect neurons) make up structures of nervous system Brain, spinal cord, and nerves
Muscle Tissue Overview Highly specialized to contract (shorten) Muscle cells elongated to provide long axis
for contraction Called muscle “fibers”
Three types of muscle tissue SKELETAL, CARDIAC, and SMOOTH
Skeletal Muscle, and more…
Packaged by connective tissue sheets into organs called skeletal muscles which are attached to skeleton
Can be controlled voluntarily and form flesh of body (word of caution here)
When contract, they pull on bones or skin Result is body movement of change in facial
expressions Cells are long, cylindrical, and
multinucleate Have obvious striations (stripes)
That’s the beat of a heart…
Cardiac muscle found only in the heart Has striations, uninucleate, branching cells
that fit tightly together at junctions called INTERCALATED DISKS
Contain gap junctions that allow ions to free pass from cell to cell
Results in rapid conduction of exciting electrical impulse across heart
Involuntary/not under conscious control
Smooth Muscle Tissue Also called VISCERAL muscle because NO
striations are visible Spindle shaped cells with single nucleus Found in walls of hollow organs (stomach,
bladder, uterus, and blood vessels) When contracts, cavity of organ constricts or
dilates so that substances are propelled through organ along specific pathway
Contracts much more slowly than skeletal/cardiac PERISTALSIS is wavelike motion that keeps
food moving through small intestine (typical of smooth muscle tissue)
Tissue Repair Tissue injury stimulates body’s inflammatory and
immune responses and healing process begins almost immediately
Tissue repair (wound healing) occurs in 2 major ways
REGENERATION is replaced of destroyed tissue by the same kind of cell
FIBROSIS involves repair by dense (fibrous) CT; i.e., formation of SCAR tissue
Which of these occurs depends on TYPE of tissue damaged and SEVERITY of injury
Tissue Repair, ctd. Clean cuts (incisions) heal more
successfully that ragged tears (lacerations) Tissue injury triggers series of events CAPILLAIRES become very permeable
allowing fluids rich in clotting proteins to seep into injured area
Leaked clotting proteins form clot, stopping blood loss, holds edges of wound together, and seals off damaged area Prevents bacteria (other harmful stuff) from
spreading to surrounding tissues
Tissue Repair, ctd. Clot exposed to air, dries and hardens to
form scab GRANULATION tissue next phase
Delicate, pink tissue composed largely of capillaries that grow into damaged area
Capillaries are delicate and bleed freely Also contains phagocytes and connective
tissue cells (fibroblasts) that synthesize collagen fibers (scar tissue) to permanently bridge the gap
Tissue Repair, ctd.
Surface epithelium begins to regenerate and cover granulation tissue beneath scab
Final result is fully regenerated surface epithelium that covers area of fibrous scar
Scar is either invisible or visible as white line depending on severity of wound
Epithelial tissues such as skin epidermins, mucous membranes, and fibrous connective tissue regenerate beautifully
Tissue Repair, ctd. Skeletal muscle regenerates poorly, if at all Cardiac and nervous tissue replaced only
by SCAR tissue Scar tissue is strong but lacks flexibility of
more normal tissues Is unable to perform normal functioning of
tissue it replaces May hamper functioning of an organ
(bladder, heart, etc.)