Download Ch 4: Tissues

Ch 4: Tissues
Intro to tissues
• Tissues –
– Groups of cells that are similar in structure
and function
• 4 primary tissue types – Epithelial (covering & linings)
– Connective (support)
– Nervous (control)
– Muscular (movement)
Epithelial tissue
• Epithelium –
– Epithe = “laid on, covering”
– A sheet of cells that covers a body surface or lines
a cavity
– Forms boundaries between environments
– Functions –
• Protection
• Absorption (process by which the products of digestion pass through the
alimentary tube mucosa into the blood or lymph)
• Filtration (passage of a solvent and dissolved substances through a
membrane or filter)
• Excretion (elimination of waste products from the body)
• Secretion (passage of material formed by a cell to its exterior)
• Sensory reception
– Occurs in the body as...
• A covering or lining epithelium
• Or as glandular epithelium
Special characteristics of epithelium
• Cellularity –
– Composed of closely packed cells with little
extracellular material between
• Specialized contacts –
– Bound together by specialized contacts
(desmosomes & tight junctions)
– Forms continuous sheets
• Polarity –
– Possess an apical & basal surface
• Apical – free and exposed – most have microvilli
– Cilia – propel substances along their free surface (trachea)
• Basal – attached surface
– Basal lamina – thin supporting sheets made mostly of
glycoproteins – acts as a selective filter for the diffusion of
nutrients
Specialized characteristics cont.
• Support –
– All epithelial tissue rest & are supported by
connective tissue
– Reticular lamina –
• Below basal lamina
• Contains collagen fibers of the connective tissue
– Reticular lamina + basal lamina = basement
membrane
• Reinforces epithelium (helps resist tearing & stretching)
• Avascular but innervated –
– Avascular = no blood vessels
• Nourished by diffusing nutrients from underlying
connective tissue
– Innervated = supplied by nerves
• Regeneration –
– High regeneration capacity
Cell shapes
Classification of epithelium
• Naming –
– First name –
• Indicates the number of layers present
• Simple – one layer
– Absorption and filtration
• Stratified – more than one
– Highly abrasive
– Shape differs among cell layers
– Named due to the apical layer
– Second name • Describes the shape of the cell
• Squamous –
– Flat and scale like
• Cuboidal –
– Box/cube like
• Columnar –
– Tall and column shaped
Epithelium
• Simple epithelia are mostly concerned with
absorption, secretion, and filtration
– Simple squamous –
•
•
•
•
•
Single layer of flattened cells
Sparse cytoplasm
Bulging nucleus
Filtration & exchange
Special examples;
– Endothelium –
» “inner covering”
» Slick & friction reducing
» Lymphatic vessels, blood vessels, heart, & capillaries
– Mesothelium –
» “middle covering”
» Serous membrane lining ventral body cavities
» Covers organs
Simple squamous
Epithelium cont.
• Simple cuboidal –
– Single layer of cube-shaped cells
– Forming the smallest ducts of glands
– Kidney tubules
– Secretion & absorption
– Spherical nuclei
• Simple columnar –
– Single layer of column-shaped cells
– Line the digestive tract (stomach to rectum)
• Dense microvili to increase absorption
– Goblet cells –
• secrete protective mucus
Simple cuboidal
Simple columnar
Epithelium cont.
• Pseudostratified columnar –
– Contains cells of varying heights
– Gives the false (psuedo) impression that there are
many layers
• Nuclei are at various heights – gives the false impression
–
–
–
–
All cells rest on basement membrane
Tallest cells reach the free apical surface
May contain cilia & goblet cells
Line the respiratory tract
Pseudostratified
Stratified epithelium
• Stratified epithelia’s main function is
protection.
• Consists of two or more cell layers
• Regeneration occurs at the basal
surface
• More durable than simple epithelium
• Stratified cuboidal –
– Rare
– Ducts of large glands
Stratified epithelium cont.
• Stratified squamous –
– Most common
– Several cell layers
– Cells on free surface are squamous shaped
(named for free exposed surface)
– Underlying cells are cuboidal or columnar
– Protection
– Basal cells replace apical cells
– Apical cells are squamous shaped because they
are not receiving adequate nutrients
• Rely on diffusion of nutrients
– External part of the skin & extends into every body
opening
Stratified squamous
Stratified epithelium cont.
• Stratified columnar –
– Limited distribution
– Small amounts in pharynx, male urethra, & some
glandular ducts
• Transitional –
–
–
–
–
Forms the hollow organs of the urinary system
Allows for stretch
Basal cells = cuboidal or columnar
Apical cells vary in appearance depending on the
level of stretch
– Not stretched – multilayered membrane
– Stretched (distension) – membrane becomes
squamous like
Transitional
Glandular epithelia
• Gland –
– Cells that make or secrete (export) a product
• Secretion = Active Process
– Secretion – aqueous fluid containing proteins
– 2 types –
• Endocrine
– Internally secreting
– Ductless (they loose their ducts)
– Secrete hormones by exocytosis
» Directly into lymph or blood systems
» Or directly into the extracellular space
• Exocrine
–
–
–
–
–
Externally secreting
Have ducts
More numerous in the body
Secrete onto a surface or into body cavities
Sweat, oil, salivary glands
Connective tissue
• Found everywhere in the body
• Consist of living cells surrounded by a matrix
• Differences = cell type & fiber type & the
amount of the two
• Main classes –
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–
–
–
Connective tissue proper – fat and fibrous tissue
Cartilage
Bone
Blood
• Major functions –
–
–
–
–
Binding & support
Protection
Insulation
Transportation
Connective tissue cont.
• Common characteristics –
– Common origin –
• All connective tissues arises from embryonic tissue
called mesenchyme
– Degrees of vascularity –
• Connective tissue ranges from avascular to highly
vascularized
• Cartilage – avascular
• Dense connective tissue – poor vascularization
• All other connective tissue – rich blood supply
– Extracellular matrix –
• Connective tissue is composed mainly of nonliving
extracellular matrix
• Separates the cells of the tissue
• Allows connective tissue to –
– Bear weight
– Withstand tension
– Endure physical trauma
Connective tissue cont.
• Ground substance –
– Unrestricted material that fills the space between
the cells and contains fibers
– Mechanism through which nutrients and other
dissolved substances can diffuse
– Composed of:
• Interstitial fluid
• Cell adhesion proteins
• Proteoglycans – helps determine the stiffness of the
ground substance
• Fibers – makes the fluid less pliable
Connective tissue cont.
• Fibers –
– Provide support
– Collagen fibers –
• Strong
• Provide large amounts of tensile strength (ability to resist
longitudinal strain)
• Composed of fiberous protein: collagen
• Has a glistening appearance; also called white fibers
– Elastic fibers –
• Elastin proteins
• Allows fibers to stretch & recoil
• Skin, lungs, & blood vessels
– Reticular fibers –
•
•
•
•
Reticul – “network”
Fine collagenous fibers that form networks
Extensive branching network
Surrounds blood vessels, supports soft tissue organs, & around
basement membranes
Connective tissue cont.
• Fundamental cell types –
– All connective tissues have an immature
and mature cell form
– “blast” – actively forming cells – secrete
ground substance & fibers characteristic of
the matrix
• 4 primary blast cells –
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–
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Osteoblast – bone cells
Fibroblast – connective tissue proper
Chondroblast – cartilage
Hematopoietic stem cell – blood
– “cyte” – inactive mature cells
• Osteocyte – mature bone cells
• Chondrocyte – mature cartilage cells
Types of connective tissue
• Connective tissue proper –
– Loose connective
• Areolar, adipose, & reticular
– Dense connective
• Dense regular, dense irregular
Loose connective tissue
• Areolar –
– “areola” – a small open space
– Binds body parts together while allowing them to
move freely over one another
– Wraps small blood vessels & nerves
– Surrounds glands
– Forms subcutaneous tissue
– Most widely distributed connective tissue
– Contains fibroblasts –actively mitotic fiber cells
– Loose arrangement of tissue – provides a
reservoir of water and salt
Areolar
Loose connective tissue
• Adipose –
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–
–
–
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Fat tissue
Contain a pure fat droplet, displaces nucleus
Highly vascularized – high metabolic activity
Closely packed cells – little matrix
Adipocytes –
• Fat cells
• Mature cells are some of the largest cells in the body
• Mature cells can’t divide
– Develops where areolar tissue is plentiful
– Insulation, stores nutrients, & shock absorber
– Brown fat –
• Consumes its stored nutrients to generate heat to warm
the body
• Occurs in babies who lack the ability to produce their
own heat through shivering
Adipose
Loose connective tissue
• Reticular connective tissue –
– Resembles areolar tissue
– Contains only reticular fibers
– Forms stroma • Internal framework
• Supports blood cells
• Lymph system, spleen, & bone marrow
– Limited within the body even though
reticular fibers are numerous
Reticular
Dense connective tissue
• Dense regular –
– Contains closely packed bundles of collagen fibers
running in the same direction
– Run parallel to the direction of pull
– Makes up tendons (attach muscle to bone) and
ligaments (attach bone to other joints)
– Great resistance to tension – exerted in a single
direction
– Poorly vascularized – slow regeneration
Dense regular
Dense connective tissue
• Dense irregular tissue –
– Contains thick bundles of collagen fibers
– Arranged in an irregular (more than one
plane) fashion
– Found in:
• Dermis
• Joint capsules
Dense irregular
Cartilage
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•
•
Lacks nerve fibers (not innervated)
Avascular
Withstands tension & compression
Tough but flexible
Ground substance –
– Collagen fibers
– Elastic fibers
– Water (80%)
• Allows cartilage to rebound after being compressed
• Nourishes the cartilage cells
• Chondroblasts – produces new matrix
• Chondrocytes – found in small groups w/in cavities
(lacunae)
Cartilage cont.
• Hyaline –
– Hyalin = glass
– Collagen fibers are not apparent within the matrix
– gives it a glass like appearance
– Gristle
– Most abundant cartilage
– Providing firm support with some pliability
– Covers the ends of long bones
– Absorbs compression
– Supports the tip of the nose & connects ribs to
sternum
– Epiphyseal plates – actively growing regions near
the end of long bones – continued growth in length
Hyaline
Cartilage cont.
• Elastic –
– Found where strength & exceptional
stretch are needed
– Contains large amounts of elastin fibers –
• Allows for repeated bending
– External ear
– Epiglottis – covering the respiratory system
Elastic
Cartilage cont.
• Fibrocartilage –
– Found where strong support & ability to
withstand pressure are required
– Rows of chondrocytes alternating with
rows of thick collagen fibers
– Compresses and resists tension
– Intervertebral disks
– Spongy cartilage of the knee joint
Fibrocartilage
Bone
• Bone –
– Osseous
– Supports & protects the body
– Additional collagen fibers & calcium salts found in
extracellular matrix
– Provides cavities for fat storage & blood cells
– Osteoblasts – produce organic portions of the
matrix – bone salts deposited on & between the
fibers
– Osteocytes – reside in the lacunae
– Highly vascularized
Bone (osseous tissue)
Blood
• Blood –
– Classified as a connective tissue
because...
• Developed from mesenchyme
• Consists of blood cells & plasma proteins
surrounded by plasma
• Fibers – soluble protein molecules that become
visible during clotting
• Transport vehicle for the body
Blood
Nervous tissue
• Nervous tissue –
– Main component of the nervous system
– Regulates & controls body functions
– Brain, spinal cord, & nerves
– Composed of 2 cell types –
• Neurons –
– Specialized cells that generate and conduct electrical
impulses
– Branching cells
– Cytoplasmic extensions – allows them to transmit
electrical impulses
• Supporting cells –
– Nonconductive cells that support, insulate, and
protect the neurons
Nervous tissue
Muscle tissue
• Muscle tissue –
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Highly cellular
Well vascularized
Responsible for movement
3 types –
• Skeletal –
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Attaches to the skeleton & produces voluntary body movement
Packaged by connective tissue
Form the flesh of the body
Contain many nuclei & striations (indicates the alignment of myofilaments)
Voluntary muscle
• Cardiac –
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Only in the walls of the heart
Responsible for the involuntary movement of the heart
Contain striations
Uninucleated
Branching cells that fit together & the intercalated disc junctions
Involuntary muscle
• Smooth –
– No visible striations
– One nucleus
– Found in the walls of hollow organs (other than the heart) – digestive,
reproductive, & urinary organs
– Involuntary muscle
Muscles
Membranes
• Cutaneous membrane –
– Cutaneous membrane, or skin, is an organ system
consisting of keratinized squamous epithelium (epidermis)
firmly attached to a thick layer of dense irregular connective
tissue (dermis)
– Dry membrane because its exposed to the air
• Mucous membrane –
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–
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Line hollow body cavities (ie. digestive organs)
Open to the exterior
Adapted for absorption or secretion
Bathed in mucus
Contain stratified squamous or simple columnar epithelium
• Serous membrane –
– Found in closed cavities
– Serous fluid that lubricates the facing surface
– Named for their location & organ association (ie. pleura,
pericardium)
– Consist of simple squamous epithelium
– Rests on a thin layer of areolar (loose connective) tissue
Membranes
Tissue repair
• Tissue repair occurs in two ways:
regeneration (replacement of destroyed
tissue with the same kind of tissue) & fibrosis
(replaces damaged tissue with fibrous
connective tissue – scar tisse)
• 3 steps in the repair process –
– Inflammation –
• Prepares the area for the repair process
• Allows white blood cells & plasma to seep into the injured
area
• Forms a clot & holds the wound together
– Organization –
• Restores the blood supply
• Clot is replaced by delicate pink tissue – granulation
tissue
• Restores blood supply
– Regeneration & fibrosis –
• Permanent repair
• New tissue regenerates under the scab
Embryonic & fetal development
• Primary germ layers –
– Ectoderm –
• Most superficial layer (external layer)
• Nervous tissue
– Mesoderm –
• Middle layer
• Muscle and connective tissue
– Endoderm –
• Deepest layer (internal layer)
• Epithelial tissue
Primary Germ layers
Aging
• Increased age –
– Epithelia becomes thin
– Number of collagen fibers decreases
– Bone, muscle, nervous tissue begin to
atrophy