Chapter 5: Histology
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INTRODUCTION
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Tissue: group of similar cells that perform
a common function
Matrix: nonliving intercellular material
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PRINCIPAL TYPES OF TISSUE
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Epithelial tissue (Table 5-1)
Connective tissue
Muscle tissue
Nervous tissue
Embryonic development of tissues
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Primary germ layers
• Endoderm
• Mesoderm
• Ectoderm
Histogenesis: process of the primary germ layers
differentiating into different kinds of tissue
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EXTRACELLULAR MATRIX
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Extracellular matrix (ECM) is a complex,
nonliving material between cells in a
tissue (Figure 5-1)
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Some tissues have a large amount of ECM;
other tissues have hardly any
Different kinds of components give ECM in
different tissues a variety of characteristics
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EXTRACELLULAR MATRIX
(cont.)
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Components (Table 5-2)
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Water
Proteins
• Structural proteins
Collagen: strong, flexible protein fiber
 Elastin: elastic fibers
• Includes glycoproteins: proteins with a few carbohydrate
attachments
 Fibronectin and laminin help connect the ECM
components to cells by binding with integrins in
plasma membranes
 Glycoprotein attachments also allow local
communication within a tissue
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EXTRACELLULAR MATRIX
(cont.)
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Proteoglycans
• Hybrid molecules that are mostly carbohydrates
attached to a protein backbone
• Examples: chondroitin sulfate, heparin, and
hyaluronate
• Different proteoglycans give different characteristics
to ECM, such as thickness and shock absorption
(Table 5-2)
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EXTRACELLULAR MATRIX
(cont.)
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Functions
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Helps bind tissues together structurally
• ECM components bind to each other and to
integrins in plasma membranes of cells
• Some tissues are held together primarily by
intercellular junctions
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Allows local communication among ECM and
various cells through connection with integrins
in plasma membranes
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Major Types of Tissues (4)
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Epithelial tissue
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Connective tissue
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ie: Bones, joint cartilage, tendons and ligaments,
blood and fat
Muscle tissue
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ie: outer layer of skin; lining of respiratory
digestive, urinary and reproductive tracts as well
as glands of the body.
ie: Heart, skeletal and smooth mm.
Nervous tissue
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ie: CNS, PNS and sensory organs of the body
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EPITHELIAL TISSUE
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Types and locations
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Epithelium is divided into two types:
• Membranous (covering or lining) epithelium
• Glandular epithelium
Locations
• Membranous epithelium: covers the body and some
of its parts and lines the serous cavities; blood and
lymphatic vessels; and respiratory, digestive, and
genitourinary tracts
• Glandular epithelium: secretory units of endocrine
and exocrine glands
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EPITHELIAL TISSUE (cont.)
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Functions
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Protection
Sensory functions
Secretion
Absorption
Excretion
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EPITHELIAL TISSUE (cont.)
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Generalizations about epithelial tissue
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Limited amount of matrix material
Membranous type attached to a basement
membrane
Avascular
Cells are in close proximity, with many
desmosomes and tight junctions
Capable of reproduction
UNDERGOES MITOSIS
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EPITHELIAL TISSUE:
MEMBRANOUS
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Classification of epithelial tissue
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Membranous (covering or lining) epithelium
(Table 5-3)
Number of cell layers – Simple vs. Stratified
Classification based on cell shape (Figure 5-2)
 Squamous
 Cuboidal
 Columnar
 Pseudostratified columnar
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Simple Squamous Epithelium
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Structure: single layer of flat cells
Location: simple squamous- lining of blood and lymphatic vessels
(endothelium) and small ducts, alveoli of the lungs, loop of Henle in
kidney tubules, lining of serous membranes (mesothelium) and
inner surface of the eardrum.
Functions: diffusion, filtration, some protection against friction,
secretion, absorption.
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Simple Cuboidal Epithelium
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Locations: Kidney tubules, glands and their ducts, choroid plexus of the
brain, lining of terminal bronchioles of the lungs, and surface of the
ovaries.
Structure: single layer of cube-shaped cells; some types have microvilli
(kidney tubules) or cilia (terminal bronchioles of the lungs)
Functions:
 Secretion and absorption in the kidney
 Secretion in glands and choroid plexus
 Movement of mucus out of the terminal bronchioles by ciliated
cells.
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Simple Columnar Epithelium
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Location. Glands and some ducts, bronchioles of lungs, uterine tubes,
stomach, intestines, gallbladder, bile ducts and ventricles of the brain.
Structure: single layer of tall, narrow cells. Some have cilia (bronchioles
of lungs, auditory tubes, uterine tubes, and uterus), microvilli (intestine)
or goblet cells.
Functions:
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Movement of particles out of the bronchioles by ciliated cells
 Aids in the movement of oocytes through the uterine tubes by ciliated cells
 Secretion by glands of the stomach and the intestine
 Absorption by cells of the intestine.
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Stratified Squamous Epithelium
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Locations:
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Moist- mouth, throat, larynx, esophagus, anus, vagina, inferior urethra,
and cornea
 Keratinized- skin
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Structure: multiple layers of cells that are cuboidal in the basal layer
and progressively flatten toward the surface. In moist, surface cells
retain a nucleus and cytoplasm. In keratinized, surface cells are dead.
Functions: protection against abrasion, caustic chemicals, water loss,
and infection.
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Stratified Cuboidal Epithelium
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Locations: sweat gland ducts, pharynx and salivary gland
ducts
Structure: multiple layers of somewhat cube-shaped cells.
Functions: secretion, absorption and protection against
infections.
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Stratified Columnar Epithelium
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Locations: rare in the body, mammary gland duct, larynx,
portion of male urethra.
Structure: multiple layers of cells with tall thin cells resting
on layers of more cuboidal cells. Cells ciliated in the larynx.
Function: protection and secretion.
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Pseudostratified Columnar Epithelium
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Locations: air passages: lining of nasal cavity, nasal sinuses, auditory
tubes, pharynx, trachea, and bronchi of lungs; male reproductive system
Structure: all cells reach basement membrane. Appears stratified because
nuclei are at various levels. Almost always ciliated and associated with
goblet (mucus-producing) cells.
Functions:
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Synthesize and secrete mucus onto the free surface (goblet cells)
 Move mucus (or fluid) that contains foreign particles over the free surface and
from passages (cilia)
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Transitional Epithelium
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Location: lining of urinary bladder, ureters and superior urethra.
Structure: stratified; cells change shape depending upon
amount of distention of the organ.
Functions: accommodates fluctuations in the volume of fluid in
an organ or tube; protection against the caustic effects of urine.
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EPITHELIAL TISSUE:
GLANDULAR EPITHELIUM
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Glandular epithelium
• Specialized for secretory activity
• Exocrine glands: discharge secretions into ducts
and lead to the exterior of the body
• Endocrine glands: “ductless” glands; discharge
secretions directly into blood or interstitial fluid
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EPITHELIAL TISSUE:
GLANDULAR EPITHELIUM (cont.)
• Structural classification of exocrine glands (Figure 511; Table 5-5)
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Multicellular exocrine glands are classified by the
shape of their ducts and the complexity of their duct
system
Shapes include tubular and alveolar
Simple exocrine glands: only one duct leads to the
surface
Compound exocrine glands: have two or more ducts
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EPITHELIAL TISSUE:
GLANDULAR EPITHELIUM (cont.)
• Functional classification of exocrine glands (Figure 5-12)
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Apocrine glands
– Secretory products collect near apex of cell and
are secreted by pinching off the distended end
– Secretion process results in some damage to cell
wall and some loss of cytoplasm
– Mammary glands are good examples
Holocrine glands
– Collect secretion products within the cell, rupture
to release causing death of the cell
– Sebaceous glands are holocrine
Merocrine glands
– Secrete directly through cell membrane
– Secretion proceeds with no damage to cell wall
and no loss of cytoplasm
– Most numerous gland type
– Salivary glands
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CONNECTIVE TISSUE
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Functions, characteristics, and types
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General function: connects, supports,
transports, and protects
General characteristics extracellular matrix (ECM) predominates in most
connective tissues and determines its physical
characteristics; consists of fluid, gel, or solid matrix, with
or without extracellular fibers (collagenous, reticular, and
elastic) and proteoglycans or other compounds that
thicken and hold together the tissue
(Figures 5-1 and 5-14)
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Composition of Extracellular
Matrix: Fibers
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Protein fibers
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Collagen. Most common protein in body; strong,
flexible, inelastic
 Reticular. Fill spaces between tissues and organs.
Fine collagenous, form branching networks
 Elastic. Returns to its original shape after
distension or compression. Contain molecules of
protein elastin that resemble coiled springs;
molecules are cross-linked
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CONNECTIVE TISSUE (cont.)
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Four main types (Table 5-6)
• Fibrous
 Loose (areolar)
 Adipose
 Reticular
 Dense
– Irregular
– Regular (collagenous and elastic)
• Bone
 Compact bone
 Cancellous bone
• Cartilage
 Hyaline
 Fibrocartilage
 Elastic
• Blood
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Functions of Connective Tissue
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Enclose organs as a capsule and separate
organs into layers
Connect tissues to one another. Tendons and
ligaments.
Support and movement. Bones.
Storage. Fat.
Cushion and insulate. Fat.
Transport. Blood.
Protect. Cells of the immune system.
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Adult Connective Tissues
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Loose (areolar). Collagenous fibers are loosely
arranged
Dense. Fibers form thick bundles that nearly fill all
extracellular space
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Dense regular
Dense irregular
With special properties
Cartilage
Bone
Blood and hemopoietic tissue
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Loose (Areolar) Connective Tissue
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Most widely distributed of all tissues
Loose packing material of most organs and tissues
Attaches skin to underlying tissues.
Contains collagen, reticular, elastic fibers
Cells include fibroblasts (make ground substance), mast cells (release
histamine to produce an inflammation response), adipose cells,
macrophages
Soft gel matrix due to hyaluronic acid
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Connective Tissue
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Adipose tissue (Figures 5-17 and 5-18)
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Similar to loose connective tissue but contains mainly fat cells
(adipocytes)
Functions—protection, insulation, support, and food reserve
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Connective Tissue
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Reticular tissue (Figure 5-19)
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Consists of network of branching reticular fibers with reticular
cells overlying them
 Forms framework of spleen, lymph nodes, and bone marrow
 Functions—defense against microorganisms and other
injurious substances; reticular meshwork filters out injurious
particles, and reticular cells phagocytose them
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Dense Irregular FibrousTissue
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Bundles and sheets of collagenous and elastic
fibers oriented in multiple directions
Strong, can withstand stress
Dermis, fascia surrounding muscles,encapsulates
organs
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Dense Regular Collagenous
Fibrous Connective Tissue
Collagenous: tensile
strength
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Tendons: Connect
muscles to bones; fibers
are not necessarily
parallel
Elastic: more stretch
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Ligaments: Connect
bones to bones. Collagen
often less compact,
usually flattened, form
sheets or bands
Arteries – recoil and
stretch depending on
blood pressure
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Connective Tissue
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Bone tissue
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Highly specialized connective tissue type
• Cells—osteocytes—embedded in a calcified matrix
• Inorganic component of matrix accounts for 65%
of total bone tissue and add hardness
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Functions:
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•
•
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Support
Protection
Point of attachment for muscles
Reservoir for minerals
Supports blood-forming tissue
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Connective Tissue
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Compact bone (Figures 5-25 and 5-26)
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Osteon (Haversian system)
• Structural unity of bone
• Spaces for osteocytes called lacunae arranged in concentric rings
called lamellae
• Canaliculi are canals that join lacunae with the central Haversian canal
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Cell types:
• Osteocyte—mature, inactive bone cell
• Osteoblast—active, bone-forming cell
• Osteoclast—bone-destroying cell
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Connective Tissue
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Cancellous bone (Figures 5- 25 and 5-27)
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Trabeculae—thin beams of bone which form framework
Supports red bone marrow
• AKA Myeloid tissue—a type of reticular tissue
• Produces blood cells
Called spongy bone because of its spongelike
appearance
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Cartilage
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Composed of chondrocytes located in matrix-surrounded
spaces called lacunae.
Type of cartilage determined by components of the matrix.
Firm consistency.
Avascular and no nerve supply. Heals slowly.
Perichondrium. Membrane which surrounds cartilage which
allows diffusion of nutrients.
Types of cartilage
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Hyaline
Fibrocartilage
Elastic
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Hyaline Cartilage
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Structure: low amount of collagen fibers evenly distributed in
proteoglycan matrix. Smooth surface in articulations
Locations:
 Found in areas for strong support and some flexibility: rib
cage, trachea, and bronchi
 In embryo forms most of skeleton
 Covers ends of bones which articulate to form joints
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Fibrocartilage
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Strongest and most durable
Shock absorption; slightly compressible and very tough
Locations: found in areas of body where a great deal of
pressure is applied to joints
 Knee, jaw, between vertebrae
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Elastic Cartilage
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Structure: elastic and collagen fibers create
flexibility, rigid but elastic properties
Locations: external ears, larynx and epiglottis
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Blood
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Matrix: plasma 55%
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Liquid and lacks fibers.
Formed elements 45%: red cells (erythrocytes), white cells
(leukocytes), and platelets (thrombocytes)
Movement of respiratory gases,nutrients and waste, constant
body temp, regulates pH
Hematopoietic tissue
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Forms blood cells
Two types of bone marrow
• Yellow
• Red
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Muscle Tissue
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Skeletal Muscle
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Voluntary, striated,multinucleate, long
nonbranching cylindrical cells
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Cardiac Muscle
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Involuntary, striated, uninucleate,
branched cells, intercalated discs
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Smooth Muscle
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Involuntary, uninucleate, spindle shaped,
found in lumen
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Nervous Tissue
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Functions—rapid regulation and integration
of body activities
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Organs
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Brain
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Spinal cord
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Nerves
- neurons
-neuroglia
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Nervous Tissue: Neurons
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Neurons or nerve cells have the ability to
produce action potentials
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Parts:
• Cell body (soma): contains nucleus
• Axon: cell process; conducts impulses away from cell
body; usually only one per neuron
• Dendrite: cell process; receive impulses from other
neurons; can be many per neuron
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Support cells of the
brain, spinal cord
and nerves
Nourish, protect,
and insulate
neurons
Types
-astrocytes form
BBB
-microglia – destroy
pathogens
-oligodendrocytes –
insulate nerve cells
to increase
conduction speed
Neuroglia
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TISSUE REPAIR
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Tissues have a varying capacity to repair
themselves; damaged tissue regenerates or is
replaced by scar tissue
Regeneration: growth of new tissue (Figure 5-36)
Scar: dense, fibrous mass; unusually thick scar is
a keloid (Figure 5-37)
Epithelial and connective tissues have the
greatest ability to regenerate
Muscle and nervous tissues have limited capacity
to regenerate
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Body Membranes
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Thin tissue layers that cover surfaces, line cavities,
and divide spaces or organs (Figure 5-39, Table 5-8)
Epithelial membranes are most common type
(Figure 5-40)
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Cutaneous membrane (skin)
• Primary organ of integumentary system
• One of the most important organs
• Composes approximately 16% of body weight, largest organ
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Serous membrane (serosa)
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•
•
•
Parietal membranes—line closed body cavities
Visceral membranes—cover visceral organs
Pleura—surrounds a lung and lines the thoracic cavity
Peritoneum—covers the abdominal viscera and lines the
abdominal cavity
• Pericardium – surrounds heart
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Body Membranes
• Mucous membrane (mucosa)
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Lines and protects organs that open to the exterior of the body
Found lining ducts and passageways of respiratory, digestive, other tracts
Lamina propria—fibrous connective tissue underlying mucous epithelium
Mucus is made up mostly of water and mucins—proteoglycans that form a
double-layer protection against environmental microbes (Figure 5-41)
Connective tissue membranes
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•
•
•
•
Do not contain epithelial components
Synovial membranes—line the spaces between bone in joints
Have smooth and slick membranes that secrete synovial fluid
Help reduce friction between opposing surfaces in a moveable joint
Synovial membranes also line bursae
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