Tissue: The Living Fabric
Chapter 4
Chapter Outline
Epithelial Tissue Connective Tissue Epithelial Membranes Nervous Tissue Muscle Tissue Tissue Repair Developmental Aspects of Tissue
Introduction to Tissue The human body is a multicellular
organism– Its cells form tight communities that have
similar functions– Cell specialization allows for division of
labor – However, the risk is that loss of specialized
cells means the loss of that function and potentially the individual
Introduction to Tissue A tissue is defined as a group of closely
associated cells that perform related functions are similar in structure
Tissue do not consist entirely of cells as between the living cells is nonliving extracellular material
Tissue Groups of closely associated cells that are
similar in structure and function are called tissues
Four primary tissues interweave to form the “fabric” of the body– Epithelial (covering)– Connective (support)– Muscle (movement)– Nervous (control)
Organs
Tissues are organized into organs – Most organs contain all four tissue types– However, most organs will have one
predominant tissue type present– The arrangement and proportion of tissues
present determines the function of the organ
SECTION I
EPITHELIAL TISSUE
Epithelial Tissue Epithelial tissue is a sheet of cells that
covers a body surface, a body cavity, or has a glandular function
Epithelia form the boundaries between environments
Epithelial has many functions including; protection, absorption, filtration, excretion, secretion, and sensory reception
Epithelial Tissue Epithelial tissue constitutes all the inner and
outer surfaces of the body including;– Skin– Viscera of the digestive and respiratory system– The lining of body cavities– Linings of blood vessels– Most glandular tissue
Special Characteristics of Epithelium Cellularity Epithelial tissue is composed
almost entirely of close packed cells with little extracellular material lying in the space between them
Specialized Cells form continuous sheets. contacts Adjacent cells are bound
together at many points by lateral contacts including, tight junctions and desmosomes
Special Characteristics of Epithelium
Junctions & Desmosomes
Tight junctions occur where protein molecules in adjacent cells fuse together to form an impermeable junction
Desmosomes are anchoring junctions that bind adjoining cells and prevent their separation
Gap Junctions
Gap junctions allow chemical substances to pass to adjacent cells
Cells connected by hollow connexons
Found in electrically excitable tissues (heart and smooth muscle)
Ion passage from one cell to another helps to synchronize electrical activity
Special Characteristics of Epithelium Polarity
– All epithelial tissue has an upper (apical) surface exposed to the body exterior or an internal cavity
– All epithelia exhibit polarity where the cells near the apical surface differ from those at the basal surface
– Apical surfaces can be smooth, most have microvilli, and some have cilia
– The basal surface of epithelium is called the basal lamina, which acts as a selective filter that determines which molecules are allowed to enter the epithelium
Special Characteristics of Epithelium
Special Characteristics of Epithelium The basal surface of epithelium lies on a thin
sheet called a basal lamina, which is part of the basement membrane
Deep to the basal lamina is a layer of reticular fibers belonging to the underlying connective tissue
Together the reticular fibers and the basal lamina form the basement membrane
Special Characteristics of Epithelium Supported by connective tissue
– All epithelial tissue sheets rest upon and are supported by connective tissue
– Deep to the basal lamina is the reticular lamina, a layer of extracellular material containing a fine network of collagen fibers from the underlying connective tissue
– The basement membrane reinforces the epithelial sheet enabling it to resist stretching and tearing
– It also defines the epithelial boundary
Special Characteristics of Epithelium
Innervated but avascular– Epithelial tissues are supplied with nerve
cells• Thus they can contribute to sensory function
– Epithelial tissues contain no blood vessels• Epithelial tissue receive nutrients by substances
diffusing from blood vessels in the underlying connective tissue layers
Special Characteristics of Epithelium
Regeneration– Epithelial cells have a high regenerative
capacity– Epithelial cells are exposed to friction, others
are damaged by hostile substances in their environment
– If nourished adequately, epithelial tissue can replace lost cells rapidly by cell division
Classification of Epithelia
Each epithelium is given two names:– The first name references the number of
epithelial cell layers present• Simple
• Stratified
– The second name describes the shape of the cells present in the epithelial cell layer
• Squamous
• Cuboidal
• Columnar
Simple and Stratified Epithelium
Simple epithelium is composed of a single tissue layer– It is usually found where absorption and
filtration occur, thus a thin layer facilitates these processes
Stratified epithelium consists of two or more layers stacked one upon the other– It is usually found in areas of high abrasion
and functions to protect underlying cell layers
Epithelial cells All epithelial cells are hexagon shaped This shape allows the cells to be tightly
packed with little wasted space Epithelial cells look like a honeycomb Epithelial cells vary in height and are
named on the basis of shape– Squamous cells are flattened and scalelike– Cuboidal cells are boxlike in appearance– Columnar cells are tall and column shaped
Epithelial shape
Squamous - flat and scale-like
Cuboidal - boxlike Columnar - tall
and column shaped
Simple Epithelia All the cells in the layer have the same
shape There are four major classes of simple
epithelia– Simple squamous– Simple cuboidal– Simple columnar– Pseudostratified columnar (Highly modified
simple epithelium)
Stratified Epithelia There are also four major classes of
stratified epithelia– Stratified squamous– Stratified cuboidal– Stratified columnar– Transitional epithelium (a modified
stratified squamous epithelium)
Simple Squamous Epithelium The simplest form of epithelium A single layer of flattened cells Thin and permeable, this type is often
found where filtration or diffusion is a priority
Two simple squamous epithelium have special names related to their location– Endothelium (lining blood vessels)– Mesothelium (found in serous membranes)
Simple EpitheliaSimple Squamous Epithelium
Simple squamous epithelium forming walls of alveoli (air sacs) of the lung
Simple Epithelium:Simple Cuboidal Epithelium
Single layer of cube like cells Important functions are secretion and
absorption It forms ducts and secretary portions of
small glands and tubules in the kidneys
Simple Epithelium:Simple Cuboidal Epithelium
Simple cuboidal epithelium in kidney tubules
Simple Epithelium:Simple Columnar Epithelium
Consists of a single layer of tall, closely packed cells
It lines the digestive tube from stomach to anal canal
Important functions are secretion and absorption and it forms a layer thin enough for ion transport yet thick enough to house the cellular structures of ion transport
Simple Epithelia:Simple Columnar Epithelium
Consists of a single layer of tall cells– unciliated in the digestive tract
• associated with absorption and secretion
• mircovilli add surface area and aid absorption
• globlet cells secret protective lubricants
– ciliated in the respiratory passages• cilia “sweep” or propel mucus by ciliary action
Simple Epithelium:Simple columnar epithelium
Simple columnar epithelium of the stomach mucosa
Simple Epithelium:Pseudostratified Columnar
Epithelium Single layer of cells of differing heights The cell nuclei are located at differing
levels above the basement membrane giving the false (pseudo) impression of multiple cell layers
Ciliated in the upper respiratory tracts Nonciliated in large body ducts
Simple Epithelium:Pseudostratified Epithelium
Pseudostratified ciliated epithelium lining the human trachea
Stratified Epithelium:Stratified Squamous Epithelium Tissue is composed of several cell layers Surface cells are flattened (squamous)
while deeper cell layers are cuboidal or columnar
Surface cells are full of keratin and dead, while basal cells are alive and active in cell mitosis
Protective in function, these cells are found in areas subjected to abrasion
Stratified Epithelium:Stratified Squamous Epithelium
Stratified squamous epithelium lining the esophagus
Stratified Epithelium:Stratified Cuboidal Epithelium Generally two layers of cube-shaped cells Form large ducts of some glands Function to protect Relatively rare tissue type
Stratified Epithelium:Stratified Cuboidal Epithelium Location
– Largest ducts of sweat glands, mammary glands and salivary glands
– No table provided in Marieb A & P, 5th edition
– Table 4.3f in 3th edition Marieb and Mallatt
Stratified Epithelium:Stratified Cuboidal Epithelium
Stratified cuboidal forming a salivary duct
Stratified Epithelium:Stratified Columnar Epithelia
Several Cell layers present Basal cells are cuboidal while superficial
cells are columnar Rare in the body; found in the large ducts
of some glands and in the male urethra Functions include protection and secretion
Stratified Epithelium:Stratified Columnar Epithelium
Stratified columnar epithelium lining the male urethra
Stratified Epithelium:Transitional Epithelium
Forms the lining of hollow urinary organs Resembles both stratified squamous and
cuboidal The cells vary in appearance depending on
the degree of distension of the organ The ability of the epithelium to thin under
pressure allows for a greater volume of urine to pass through these organs
Transitional Epithelium
Transitional epithelium lining of the bladder, relaxed state
Epithelial Surface Features The apical, lateral and basal cell surfaces
of epithelia have special features Apical surfaces have microvilli and cilia Lateral surfaces have cell junctions Basal surface has a basal lamina
Apical Surface Features Microvilli are fingerlike extension of the
plasma membrane of apical epithelial cells They occur on almost very moist
epithelium in the body Most abundant on epithelia that absorb
nutrients (small intestine) or transport ions (kidney)
Microvilli maximize the surface area across which small molecules enter or leave cells
Apical Surface Features Microvilli are abundant on epithelia that
secrete mucus, where they help anchor the mucus sheets to the epithelial surface
Finally, microvilli may act as “stiff knobs” to resist abrasion
Apical Surface Features Cilia are whip-like,
highly motile extensions of the apical surface membranes of certain epithelia cells
Each cilium contains a core of micro- tubules, nine pairs which encircle one pair
Apical Surface Features The center set of
microtubules is an axonene and each pair is called a doublet
Ciliary movement is generated when adjacent doublets grip one another with side arms made of the protein dynein causing ocillation
Apical Surface Features When the side arms
start to oscillate the doublets slide against one another causing the cilium to bend
The cilia on an epithelium bend and move in coordinated waves
The waves push mucus over its surface
Apical Surface Features
Each cilium executes a propulsive power stroke, followed by a recovery stroke
This sequence ensures that fluid is moved in one direction only
Apical Surface Features An extremely long, isolated cilium is
called a flagellum The only flagellated cells in the human
body are male sperm Sperm use their flagella to swim through
the female reproductive tract
Lateral Surface Features Three factors act to hold epithelial cells
to one another– Immunoglobulin-like proteins in the plasma
membranes are linked together– The wavy contours of the membranes of
adjacent cells join in a tongue and groove fashion
– There are special cell junctions seal off the extracellular space
Cells junctions are characteristic of epithelia cells but can be found in other tissue types as well
Lateral Surface Features
Desmosomes are the main junctions for binding cells together and are scattered along cell margins
Lateral Surface Features
The surface of each plasma membrane has an area called the circular plaque
Lateral Surface Features
The plaques of adjacent cells are joined by linker proteins called cadherins
Lateral Surface Features
Cadherins project from the cell membranes of both cells and interdigitate like the teeth of a zipper in the extracellular space
Lateral Surface Features
Intermediate filaments which are cytoskeletal elements that resist tension insert into each plaque from the inner cytoplasmic side
Lateral Surface Features
Cadherins project from the cell membranes of both cells and interdigitate like the teeth of a zipper in the extracellular space
Lateral Surface Features Bundles of intermediate filaments extend
across the cytoplasm and anchor at other desmosomes on the opposite side of the same cell
This arrangement holds not only adjacent cells together but also interconnects all the intermediate filaments of the entire epithelium into one continuous network of strong “guy wires”
This distributes tension forces evenly across the entire epithelial sheet
Lateral Surface Features
Tight junctions seal off the extracellular space
Lateral Surface Features
Tight junctions are typically located in the apical region of most epithelial cells
Lateral Surface Features At tight junctions the adjacent cells are
so close that some proteins in their plasma membranes are fuse
Fusion forms a seal that closes off the extracellular space
This prevents molecules from passing between the cells of epithelial tissue
Lateral Surface Features
Gap junctions or nexus is a spot-like junction that can occur anywhere along the lateral membranes of adjacent cells
Lateral Surface Features Gap junctions let small molecules move
directly between neighboring cells At gap junctions the adjacent plasma
membranes are very close and the cells are connected by hollow cylinders of protein (connexons)
Ions, simple sugars, and other small molecules pass through these cylinders from one cell to the next
Basal Lamina Features
At the border between the epithelium and the connective tissue is a supporting sheet called the basal lamina
Basal Lamina Features The basal lamina is a thin, noncellular
sheet consisting of proteins secreted by the epithelial cells in the overlying layer
Functionally, the basal lamina acts as a selective filter
It determines which molecules from capillaries in the underlying connective tissue will be allowed to enter the epithelium
Basal Lamina Features The basal lamina also acts as scaffolding
along which regenerating epithelial cells can migrate
Regeneration can typically occur because infections and mechanisms that destroy the epithelial cells usually leave the basal lamina intact
Without a basal lamina, regeneration of the epithelial tissue is more difficult
Basal Lamina Features
Directly deep to the basal lamina is a layer of reticular fibers belonging to the underlying connective tissue
Basal Lamina Features Combined the reticular fibers and the
basal lamina form the basement membrane
While the basal lamina and the basement membrane are different structures the terms are sometimes used interchangeably which is incorrect
Glandular Epithelia A gland consists of one or more cells that
make a secretion Many epithelial cells make secretions Secretions are usually water based fluids
containing proteins Secretion is a process whereby gland cells
obtain needed substances from the blood and transform them chemically into a product that is discharged from the cell
Glandular Epithelia Glands are classified on where they release
their secretion:– endocrine (internal secretion)– exocrine (external secretion)
Glands are classified by number of cells: – unicellular exocrine glands– multicellular exocrine glands
Unicellular glands are scattered within epithelial sheets
Multicellular glands develop by invaginating into an epithelial sheet and connective tissue
Endocrine Glands All endocrine glands eventually lose their
ducts and are considered to be ductless Endocrine glands produce hormones that
regulate body functions These glands secrete directly into the
extracellular space The hormones then enter the blood or
lymphatic fluid– Pituitary, Thyroid, Parathyroid, Adrenal,
Thymus,, and others
Exocrine Glands Exocrine glands are far more numerous
than endocrine These glands secrete their products
through a duct onto a body surface or into a body cavity
These glands secrete mucous, sweat, oil, saliva, bile, digestive enzymes, and many other substances
Unicellular Exocrine Glands
The only important example of a unicellular gland is the goblet cell
Shaped liked a goblet Distributed in the epithelial linings of the
intestinal and respiratory tract amid columnar cells with other functions
Produces mucin which when dissolved in water forms mucus, a slimy coating that protects and lubricates surfaces
Goblet cells
Found in columnar epithelium cells lining the intestinal and respiratory tract
Multicellular Exocrine Glands Multicellular exocrince glands have two
common structural elements– An epithelium derived duct – A secretory unit consisting of secreting cells
In all but the simplest glands connective tissue surrounds the secretory unit supplying it with blood an nerve fibers
Often the connective tissue forms a fibrous capsule and may subdivide the gland into lobes
Multicellular Exocrine GlandsStructural Classification
On the basis of their duct structures, multicellular exocrine glands are either simple or compound– Simple glands have a single unbranched duct– Compound glands have a branched duct
The glands are further categorized by their secretory units– Tubular (forms tubes)– Alveolar (forms sacs)– Tubuloalveolar (contains both types)
Simple Duct Structure
Compound Duct Structure
Multicellular Exocrine GlandsModes of Secretion
Merocrine glands (salivary, sweat, pancreas)– Secret their products by exocytosis and gland is
not altered Holocrine glands (sebaceous oil glands)
– The entire cell ruptures releasing the secretions Apocrine glands (mammary?)
– The apex of the secretory cell pinches off and release its secretion
Chief Modes of Secretion
Merocrine glands– Secrete products
by exocytosis
– Secretions do not alter gland
– Secretions leave gland via duct
Chief Modes of Secretion
Holocrine glands– Accumulate their
products within the gland until they rupture
– They are replaced by the division of underlying cells
– Sebaceous oil glands are the only true example in humans
Chief Modes of Secretion Apocrine glands
– Accumulate products just beneath free surface
– Apex of the cell pinches off releasing its contents
– Cell repairs the damage and the process is repeated
– Some controversy as to its presence in humans
CONNECTIVE TISSUE
SECTION II
Connective Tissue:An Introduction
Connective tissue is found everywhere in the body but the proportion present in a tissue varies
Its major functions are:– support and binding– holding body fluids– defending the body against infection– Storing nutrients as fat
Common Characteristics Common origin
– All tissue arise from mesenchyme layer Varying degrees of vascularity
– Tissue vary from rich vascular supply to avascular
Extracellular matrix– The living cells are widely distributed within
a matrix of nonliving extracellular substances
– The matrix creates the ability to bear weight, withstand tension, and abrasion
Connective Tissue: Cells in a Matrix
Structural Elements Any connective tissue is made up of three
elements; ground substance, fibers, and cells
Ground substance and fibers make up the extracellular matrix
The composition and arrangement of extracellular elements yields the diversity of connective tissues
It can be delicate and fragile, or thick, dense and strong
Ground Substance Ground substance is an unstructured material
that fills the space between cells and contain the fiber that support the tissue
It is composed of interstitial fluid, cell adhesion proteins, and proteoglycans
The ground substance holds fluid and functions as a medium through which nutrients and substances can diffuse between blood vessels and cells
Ground Substance Nutrients and oxygen diffuse out of the
capillaries and travel through a watery fluid in the extracellular matrix to reach the surrounding cells
Waste molecules from cells diffuse back through this fluid into the capillaries to be taken away by the bloodstream
The fluid through which these substances move is interstitial fluid (tissue fluid) and it derives from the blood itself
Ground Substance Ground substance is a jelly-like material
consisting of large sugar and sugar-protein molecules that soak up fluid
The molecules are called glycosaminoglygens and proteogylcans
Adhesion Proteins
Adhesion proteins serve as the “glue” that allows connective tissue cells to attach to matrix elements
Adhesion proteins include:– Fibronectin– Laminin
Proteoglycans
Proteoglycans consist of a protein core to which (GAGs) attach
GAG’s (glycoaminoglycans) are large, negatively charged polysaccharides that stick out from the core protein like fibers of a bottle brush
The polysaccharides trap water and determine the properties of the matrix
The matrix may vary from fluid to a semi stiff gel
Connective Tissue: Fibers
The fibers within connective tissue provide support
Three type of fibers are found in connective tissue matrix– Collagen– Elastic – Reticular
Collagen Fibers
Collagen fibers are extremely tough and have a high tensile strength
Fibers are able to withstand great longitudinal stresses
Collagen fibers align along lines of stress Collagen fibers are located wherever
support is needed to reinforce an organ or joint
Elastic Fibers Elastin has a randomly coiled structure
that allows it to stretch and recoil Elastin in the matrix gives it a resilient
quality Collagen fibers limit distension of the
tissue and elastin fibers return the tissue to its normal length and shape
Found where elasticity is needed– Skin, lungs, walls of blood vessels
Reticular Fibers Fine collagen fibers with a special type of
collagen unit fibril Form branching networks of delicate
fibers that surround blood vessels and support soft tissue of organs
Very apparent where connective tissue abuts other tissue types– Basement membranes of epithelial cells
Connective Tissue: Cells Each major class of connective tissue has
a fundamental cell type Actively mitotic cells are called “blast”
which implies a forming cell The primary cells types of connective
tissue are:– fibroblast - connective tissue– chondroblast - cartilage– osteoblast - bone– hemocytoblast (hematopiotetic stem cell)-
blood
Cells (con’t) Once the blast cells have synthesized the
matrix they become less active and are referred to (chrondocyte)
Mature cells maintain the health of the matrix
If the tissue is damaged they become active to repair and regenerate the matrix
Cells (con’t)
Connective tissue also harbor an assortment of other cell types– white blood cells - infection
• Neutrophils, eosinophils, lymphocytes
– mast cells - detect foreign substances and initiate a local inflammatory response
– macrophages - phagocytize a broad variety of foreign molecules and bacteria
Defense Cells Fight Infection
Areolar connective tissue is the main battlefield in the body’s war against infectious microorganisms such as bacteria, viruses, fungi and parasites
Every effort is made by the body to destroy infection at the entry site to prevent entry into the circulatory system and the potential spread throughout the body
Defense Cells Fight Infection
Areolar connective tissue contains a variety of defense cells that originate as blood cells and migrate to the connective tissues by leaving the capillaries
These defensive cells gather at infection sites in large numbers
These cells fights infection using a variety of mechanisms
Defense Cells Fight Infection Macrophages are
cells ruffled by pseudopods
These cells are non-specific phagocytic cells that devour a variety of foreign materials
Marcophages will also dispose of dead tissue cells
Defense Cells Fight Infection Plasma cells secrete protein molecules called
antibodies Antibodies bind to foreign micro organisms
and mark them for destruction Once marked a greater amount are destroyed
Defense Cells Fight Infection Mast cells lie near
small blood vessels Mast cells possess
many small granules containing chemicals that mediate inflammation especially in severe allergies
Defense Cells Fight Infection Chemical mediators include histamine,
heparin and proteases (protein degrading enzymes) and are secreted in response to infections– Histamine increases the permeability of the
nearby capillaries, causing more tissue fluid to leave the bloodstream with the subsequent swelling of the areolar tissue with fluid is a major symptom of infection
Defense Cells Fight Infection Chemicals (continued)
– Heparin in mast cells binds and stores the other mast cell molecules and regulate their action
Mast cells also play a role in defense against parasitic worms, our natural immunity against bacteria, and the normal repair of fibers, ground substance, and blood vessels in connective tissue
Defense Cells Fight Infection Neutrophils,
lymphocytes, and eosinophils are white blood cells that leave the bloodstream to fight infection
Neutrophils quickly enter infected areas and phagocytize bacteria
Defense Cells Fight Infection Additional defenses to infection comes
from both the ground substances and the collagen fibers which slow the progress of invading microorganisms
However, some bacteria secrete enzymes that rapidly break down ground substances or collagen
Connective Tissue: Mesenchyme Mesenchyme tissue is the first tissue
formed from the mesodermal germ layer It is made up of star shaped
mesenchymal cells It is a gel-like ground substance
containing fine fibers During embryonic development other
tissues differentiate from it
Mesenchyme
Connective Tissue:Connective Tissue Proper
Loose Connective Tissue– Areolar
– Adipose
– Reticular
Dense Connective Tissue– Dense Regular
– Dense Irregular
– Elastic
Areolar Connective Tissue A gel-like matrix with a loose arrange-
ment of all three fiber types Contains cells, fibroblasts, macrophages,
mast cells, and some white blood cells Because of the loose nature of the tissue it
serves as a reservoir for water and salts for the surrounding tissues
Areolar: Location
Most widely distributed type of connective tissue
Serves as the universal packing material between tissues
Packages organs Surrounds capillaries Forms subcutaneous tissue Present in all mucus membranes
Areolar Tissue: Function Wraps and cushions organs Macrophages phagocytize bacteria Plays important role in inflammation Holds and conveys fluid
Areolar Tissue
Adipose (fat) Tissue Adipose tissue is basically areolar
connective tissue in which the nutrient storing functioning is greatly increased
Adipocytes predominate tissue as little matrix is present
Oil (fat) occupies most of cell volume Compression of the cell nucleus to one side
gives it a name of “signet” cells Tissue is richly vascular owing to high
metabolic activity
Adipose Tissue: Location
Under skin Around kidneys and eyeballs In bones Within abdomen Within breasts
Adipose Tissue: Function
Provides reserve food source for fuel Insulates against heat loss Supports and protects organs
Adipose Tissue
Reticular connective tissue Reticular connective tissue resembles
areolar tissue, but the only fibers in the matrix are reticular
Fibers form a delicate internal network along which fibroblasts are distributed
Widely distributed in the body, the tissue provides internal support for many lymphocytes within lymphatic tissues such as lymph nodes, the spleen, and bone marrow
Reticular Connective Tissue:Location
Lymphoid organs– Lymph nodes– Bone marrow– Spleen
Reticular Connective Tissue:Function
Fibers form the soft internal skeleton (stroma) that supports other cell types
Supports many free blood cells in lymphatic tissue
Reticular Connective Tissue
Dense Regular Connective Tissue
A type of connective tissue consisting of dense bundles of collagen fibers
Collagen fibers are arranged in parallel that lie in the direction of pull or stress
Great resistance to tension Slightly wavy alignment allows for some
degree of stretch Has few other cells and is poorly
vascularized
Dense Regular Connective Tissue: Location
Dense regular connective tissue forms:– Tendons Muscle to bone – Aponeuroses Muscle to muscle or
bone– Ligaments Bone to bone
Ligaments have a little stretch, tendons very little
Dense Regular Connective Tissue:Function
Attaches muscle to bones or to muscles Attaches bones to bones Withstands great tensile stress when
pulling force is applied in one direction
Dense Regular Connective Tissue
Dense Irregular Connective Tissue Same structural components as regular
variety Dense bundles of collagen fibers are
thicker and arranged with fibers flowing in more than one plane
Fibers form sheets of tissue that cope with tension from a variety of directions
Dense Irregular Connective Tissue:Location
Dermis of the skin Submucosa of digestive tract Fibrous capsules of organs and joints
Dense Irregular Connective Tissue:Function
Able to withstand tension exerted in many directions
Provides structural strength to many diverse tissues and organs
Dense Irregular Connective Tissue
Cartilage Has qualities that intermediate between
dense connective tissue and bone It is tough but flexible, providing a
resilient rigidity to the structure it supports
Cartilage is avascular and devoid of nerve fibers
Ground substance contains large amounts of GAG, a major adhesion protein
Cartilage continued Ground substance contain many collagen
fibers and in some cases elastic fibers to yield a substance that is quite firm
Cartilage matrix is approximately 80%water Movement of tissue fluid in its matrix
enables cartilage to rebound after being compressed
Movement of tissue fluid helps to nourish cartilage cells
Cartilage continued
The surfaces of most cartilage structures are surrounded by a well vascularized dense irregular tissue membrane called a perichondrium
Nutrients diffuse from the perichondrium to the matrix and then to the chondrocytes
Cartilage continued
Chondroblasts in growing cartilage produce new matrix that becomes bone– During interstitial growth chondroblasts
secrete new matrix to form the cartilage piece from which a bone will develop
– During appositional growth chondroblasts secrete new matrix on the superficial surface of the cartilage structure
The firm cartilage matrix prevents the cells from becoming widely separated
Hyaline Cartilage Hyaline cartilage contains large amounts of
collagen fibers formed in an imperceptible network
Hyaline cartilage provides firm support with some pliability
It has resilient properties that resist compression
Matrix appears blue-white with a smooth almost slick surface
Hyaline Cartilage: Location
Forms most of the embryonic skeleton Covers the ends of long bones in joint
cavities Forms costal cartilages of the ribs Cartilages of the nose, trachea, and
larynx
Hyaline Cartilage: Function
Supports and reinforces with some pliability
Has resilient cushioning properties Resists compressive stress
Hyaline Cartilage
Elastic Cartilage
Similar to hyaline cartilage but with more elastic fibers in the matrix
Elastic fibers gives this tissue greater resilience to repeated bending
Found where the tissue supports the shape of the structure while allowing great flexibility
Elastic Cartilage: Location
Supports the external ear Epiglottis
Elastic Cartilage: Function
Maintain shape of structure while allowing great flexibility
Elastic cartilage
Fibrocartilage
Consists of alternating rows of thick collagen fibers
Matrix is similar to hyaline cartilage but less firm
It is compressible and resists tension well Located where strong support and the
ability to withstand heavy pressure is required
Fibrocartilage: Location
Intervertebral disks of the vertebral column
Pubic symphysis Disks of knee joint
Fibrocartilage: Function
Tensile strength with the ability to absorb compressive shock
Fibrocartilage
Bone Bone matrix is similar to that of cartilage
but is harder and more rigid Differs from cartilage in that it contains
more collagen fibers and an added matrix element of inorganic calcium salts
Osteoblasts produce the matrix then bone salts are deposited on and between fibers
Well supplied with blood vessels
Bone: Location
All structural elements of the skeletal system
Appears as long, flat, short, and irregular bones
Includes compact and spongy bone
Bone: Function
Supports the weight of the body Protects vital organs and structures Provides levels for muscles to act upon Stores calcium, other minerals, and fat Bone marrow is the site for blood cell
formation
Bone
Blood Classified as a connective tissue because
it consists of blood cells surrounded by a nonliving matrix
The fibers of blood are soluble protein molecules that become visible only during blood clotting
Blood: Location
Contained within blood vessels of the circulatory system
Blood
Blood: Function
Transport vehicle of the circulatory system
Carries nutrients, wastes, respiratory gases, and many other substances throughout the body
Blood
EPITHELIAL MEMBRANES
SECTION III
Epithelial Membranes: Epithelial membranes incorporate both
connective and epithelial tissues Epithelial membranes are a continuous
multicellular sheet composed of at least two primary tissues
Can be considered a simple organ The three common forms of epithelial
membranes are cutaneous, mucous, and serous
Cutaneous membrane
It is an organ system consisting of ketatinized stratified squamous epithelium attached to a layer of dense irregular connective tissue
A dry membrane
Mucous membranes Mucosae line body
cavities that are open to the exterior
These are moist membranes bathed by secretions
Often adapted for absorption and secretion
Serous membranes Moist membranes
found in the central body cavities
Each consists of a parietal and visceral layer
Serous fluid lubricates the two layers
NERVOUS TISSUE
SECTION IV
Nervous Tissue Nervous tissue makes regulates and
controls body functions Neurons are highly specialized cells that
generate and conduct nerve impulses Support cells are nonconducting tissue
that support, insulate and protect the delicate neurons
Nervous Tissue: Location
Brain and spinal cord of the central nervous system (CNS)
All cranial and spinal nerves of the peripheral nervous system (PNS)
Nervous Tissue: Function
Transmit electrical signals from sensory receptors to the brain
Brain interprets impulse for potential response
Signals from brain to effectors (muscles and glands) control response
Nervous Tissue
MUSCLE TISSUE
SECTION V
Muscle Tissue: Muscle tissues are highly cellular, well-
vascularized tissue responsible for most types of body movement
Muscle provides contractile force by shortening their elongated shape
Muscle cells possess myofilaments The three kinds of muscle tissue are
skeletal, cardiac and smooth
Skeletal muscle
Skeletal muscle is wrapped by connective tissue into organs called muscles which attach to bones
As skeletal muscle contracts it causes gross body movements
Skeletal muscle is identified by its long cylindrical form and obvious striations
Voluntary control
Skeletal muscle: Location
Skeletal muscle attach to bones of the skeletal system
Occasionally muscle will attach to skin
Skeletal Muscle: Function
Produces movement– Locomotion– Manipulation of the environment– Facial expression
Maintains posture Stabilizes joints Generates heat
Skeletal Muscle
Cardiac muscle
Occurs in the walls of the heart and no where else in the body
Muscle cells are striated Uninucleate cells fit together at unique
junctions called intercalated discs
Cardiac muscle: Location
Found only in the myocardium of the heart
Cardiac Muscle
Smooth muscle
Smooth muscle is so named because its fibers have no visible striations
Spindle shaped muscle cells contain one centrally located nuclei
Closely arranged to form sheets
Smooth muscle: Location
Occurs mainly in the walls of hollow organs– digestive tract– blood vessels
Smooth muscle: Function
Act to propel substances or objects along internal passageways– Food– Urine– Baby
Involuntary control Long, sustained contractions
Smooth Muscle
TISSUE REPAIR
SECTION VI
Tissue Repair Tissue repairs requires cells to divide and
migrate in response to hormones released by damaged cells
Tissue repair occurs in two major ways: by regeneration and by fibrosis
Which healing process to occur depends upon:– The type of tissue damaged – The extent of the injury
Tissue Repair
Regeneration is the replacement of destroyed tissue with the same kind of tissue
Fibrosis involves the proliferation of fibrous connective tissue called scar tissue
Tissue Repair: Inflammation Inflammation of
injury site due to release of histamine
Capillaries dilate, become permeable
White blood cells, antibodies, clotting proteins arrive
Clotting isolates injured area
Tissue Repair: Organization Blood clot replaced
by granulation tissue
Capillary buds invade area
Fibroblasts secret collagen fibers
Macrophages digest and remove dead cells
Tissue Repair: Regeneration Surface epithelium
begins to regenerate
Granulation tissue is replaced by epithelium
Fibrosed area is found deep to epithelium
Scar may not be evident
Factors Affecting Tissue Repair
The type of tissue injured Type of injury and the immediate care
received Nutrition Adequacy of blood supply State of health of the individual Age of the individual
Tissue Repair: Tissue Type Epithelial tissues regenerate very well Bone and fibrous tissue heal quite well Smooth muscle and dense regular
connective tissue have very limited capacity for regeneration
Skeletal muscle and cartilage regenerate poorly
Cardiac and nerve tissue have no regenerative capacity and are replaced by scar tissue
DEVELOPMENTAL ASPECTS OF TISSUES
SECTION VII
Developmental Aspects of Tissue
One of the first events of embryonic development is the formation of the three primary germ layers
These three germ layers are the ectoderm, mesoderm and endoderm
These primary germ layers begin to form the four primary tissues from which all body organs are derived
Tissue Origins Epithelial tissue are formed from all
three tissue layers Muscle and connective tissue form from
the mesoderm Nervous tissue forms from the ectoderm
Embryonic Germ Layers
Cell Development By the end of the second month of
development, the primary tissues have appeared, and all major organs have been laid down
Tissue growth continues on at a rapid rate throughout the embryonic and fetal periods
Most tissues cells except neurons continue to undergo cell mitosis until adulthood
Adulthood In adulthood only epithelia and blood
forming tissue are highly mitotic With increasing age the amount of
collagen generated decreases making tissue repair less efficient
Declining circulatory efficiency results in less nutrients delivered to tissue
Dietary choices also influences tissue repair
TISSUE: THE LIVING FABRIC
END OF CHAPTER 4