CHAPTER 5: TISSUES
Tissues
• Groups of cells similar in structure and function
• The four types of tissues
• Epithelial
• Connective
• Muscle
• Nerve
Epithelial Tissue
• Cellularity – composed almost entirely of cells
• Covers organs, forms the inner lining of body cavities, &
lines hollow organs
• Special contacts – form continuous sheets held together
by tight junctions and desmosomes
• Polarity – apical (free surface side) and basal (thin, nonliving basement membrane) surfaces
Epithelial Tissue
• Supported by connective tissue – reticular and basal
laminae
• Avascular but innervated – contains no blood vessels but
supplied by nerve fibers
• Get nutrients and excrete wastes via diffusion
• Regenerative – rapidly replaces lost cells by cell division
• Ex) skin
Classification of Epithelia
• Simple (one layer) or
stratified (2 or more
layers)
• Name is based on the
apical surface
• Functions
• Simple – filtration,
absorption, secretion
• Stratified - protection
Classification of Epithelia
• Squamous, cuboidal,
or columnar
• Have hexagon shape
• Makes it more efficient
Epithelia: Simple Squamous
• Single layer of flattened cells with disc-shaped nuclei
& sparse cytoplasm
• Fit tightly together (floor tiles)
• Functions
• Diffusion & filtration
• Provide a slick, friction-reducing lining in lymphatic and
cardiovascular systems
• Present in kidney glomeruli, lining of heart, blood
vessels, lymphatic vessels, & serosae
Epithelia: Simple Squamous
• Substances pass pretty easily through it
• Ex) lines the air sacs (alveoli) in lungs where oxygen and carbon
dioxide are exchanged
• Since it is so thin and delicate, it is easily damaged
Simple Squamous
• Description: single layer of flattened cells with disc-
shaped central nuclei & sparse cytoplasm; the simplest of
the epithelia
• Function: allows passage of materials by diffusion &
filtration in sites where protection is not important;
secretes lubricating substances in serosae
• Location: kidney glomeruli, air sacs of lungs, lining of
heart, blood vessels & lymphatic vessels, lining of ventral
body cavity (serosae)
Simple Squamous Epithelium
Simple Cuboidal Epithelium
• Single layer of cube-shaped cells
• Usually have large, centrally located, spherical nuclei
• Present in ovaries, kidney tubules (filtration), & ducts of
certain smaller glands like the salivary, thyroid, pancreas,
& liver glands
• Tissue secretes glandular products
Simple Cuboidal Epithelium
Simple Columnar Epithelium
• Single layer of elongated cells with large, spherical nuclei
• Goblet cells are often found in this layer
• Secrete mucus for protection on the apical surface
• Functions: secretes digestive fluids & absorbs nutrients
from digested foods
• Found in most organs of the digestive tract (stomach,
large & small intestines) and the uterus
Simple Columnar Epithelium
• Absorption cells  have microvilli on their apical surface
• This increases their surface area so more of the
substance can be absorbed
Simple Columnar Epithelium
Pseudostratified Columnar Epithelium
• Single layer of cells with different heights; some do not
reach the free surface
• Nuclei are seen at different layers
• Nonciliated cells are present in the male sperm-carrying
ducts
• Ciliated cells have cilia on the apical surface of the cells
• Constantly moving, goblet cells are present and cilia sweeps the
mucus away
• Present in the passages of the respiratory system
• Mucus from goblet cells trap dust & microorganisms; the cilia move
the mucus & captured particles up and out of the airways
Pseudostratified Columnar Epithelium
Stratified Squamous Epithelium
• This membrane composed of several layers of cells
• Function in protection from underlying areas subjected to
abrasion
• Forms the external part of the skin’s epidermis
(keratinized cells) and linings of the esophagus, mouth,
and vagina (nonkeratinized cells)
• Good at regeneration – lost cells are replaced by ones
from below
Stratified Squamous Epithelium
• Upper layers may be dead because they do not receive
enough nutrients
• Keratinized cells – contain a protective protein
• Cells in the top layer DON’T contain nuclei
• Nonkeratinized cells – do not contain the protective
protein
• Top layer of cells DO contain nuclei
Stratified Squamous Epithelium
Stratified Cuboidal Epithelium
• Two or three layers of cuboidal cells that form the lining of
a lumen
• Layering of cells provides more protection than a single
layer
• Lines the larger ducts of the mammary glands, sweat
glands, salivary glands, and pancreas
• Pretty rare in the body
Stratified Cuboidal Epithelium
Stratified Columnar Epithelium
• Limited distribution in the body
• Found in the pharynx, male urethra, and lining some
glandular ducts
• *also occurs at transition areas between two other types
of epithelia
Stratified Columnar Epithelium
Transitional Epithelium
• Specialized to change in response to increased tension
• Has several cell layers, basal cells are cuboidal, surface
cells are dome shaped
• Stretches to permit the distension of the urinary bladder
• Forms a barrier that helps prevent the contents of the
urinary tract from diffusing back into body
• Lines the urinary bladder, ureters, and part of the urethra
(only found in organs of the urinary system)
Transitional Epithelium
Glandular Epithelium
• A gland is one or more cells that makes and secretes an
aqueous fluid
• Usually found within columnar and cuboidal epithelia
• Contain a lot of rough ER
• Secretory vesicles fuse w/ membrane & secrete fluid
• Secrete lipids, proteins, steroids
• Classified by:
• Site of product release – endocrine or exocrine
• Relative number of cells forming the gland – unicellular (goblet) or
multicellular
Endocrine Glands
• Ductless glands that produce hormones
• Secretions include amino acids, proteins, glycoproteins &
steroids
• Release secretions to surrounding systems & the
hormones are transported by blood or lymphatic fluid to
organs
• Ex) estrogen & testosterone
Exocrine Glands
• More numerous than endocrine glands
• Secrete their products onto body surfaces (skin) or into
body cavities
• Ex) mucous, sweat, oil & salivary glands
• The only important unicellular gland is the goblet cell
• Multicellular exocrine glands are composed of a duct and
secretory unit
Connective Tissue
• Found throughout the body; most abundant and widely
distributed of the primary tissues
• Types of connective tissue:
• Loose connective tissue
• Adipose tissue
• Dense connective tissue
• Cartilage
• Bone
• Blood
Functions of Connective Tissue
• Binding & support of surrounding tissues
• Protection
• Insulation (adipose)
• Transportation
• Materials are able to go through the extracellular matrix
Characteristics of Connective Tissue
• Connective tissues have:
• Mesenchyme as their common tissue of origin
• Varying degrees of vascularity
• Nonliving extracellular matrix consisting of ground substances and
fibers  fills spaces between cells
• Collagen fibers
• Elastic fibers
• Reticular fibers
Structural Elements of Connective Tissue
• Ground substance – unstructured material that fills the
space between cells
• Fibers – collagen, elastic, or reticular
• Cells – fibroblasts, chondroblasts, osteoblasts, and
hematopoietic stem cells
Ground Substance
• Interstitial (tissue) fluid
• Adhesion proteins – fibronectin and laminin
• Proteoglycans – glycosaminoglycans (GAGs)
• Functions as a molecular sieve through which nutrients
diffuse between blood capillaries and cells
Fibers
• Collagen – tough; provides high tensile strength (thickest)
• Elastic – long, thin fibers that allow for stretch (medium)
• Reticular – branched collagenous fibers that form delicate
networks (thinnest)
Cells
• Fibroblasts – connective tissue proper
• Chondroblasts – cartilage
• Osteoblasts – bone
• Hematopoietic stem cells – blood
• White blood cells, plasma cells, macrophages, and mast
cells
Loose Connective Tissue
• Also know as areolar tissue
• Forms delicate, thin membranes throughout the body;
widely distributed
• The cells of this tissue are mainly fibroblasts; they are
separated by a gel-like matrix that contains many
collagenous and elastic fibers
• Binds the skin to the underlying organs and fills spaces
between muscles
• Wraps and cushions organs
Loose Connective Tissue
Adipose Tissue
• Fat
• Develops when certain cells store fat in droplets within
their cytoplasm and enlarge
• When these cells are so numerous that they crowd other
cells types they form adipose tissue
• Lies beneath the skin, spaces between muscles, around
the kidneys, behind the eyeballs, in abdomen, on the
surface of the heart, and around certain joints
• Cushions joints and the kidneys, insulates the body,
stores energy in fat molecules
Adipose Tissue
Dense Connective Tissue
• Consists of many closely packed, thick, collagenous fibers
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and a fine network of elastic fibers
It has relatively few cells  most are fibroblasts
Collagenous fibers of dense connective tissue are very
strong  enables the tissue to withstand pulling forces
Often binds body parts together as parts of tendons and
ligaments
Protective white layer of the eyeball & in the deeper skin
layers
Tissue repair is slow because of the poor blood supply to
dense connective tissue
Dense Connective Tissue
• Attaches muscles to bone or to other muscles and bone
to bone
• Found in:
• Tendons – attaches muscle to bone
• Ligaments – attaches bone to bone
• Aponeuroses – attaches muscle to muscle
Dense Connective Tissue
Cartilage
• Rigid connective tissue
• Provides support, frameworks, and attachments, protects
underlying tissues and forms structural models for many
developing bones
• Cartilage matrix is abundant and largely composed of
collagenous fibers embedded in a gel-like ground
substance
• Chondrocytes  cartilage cells
• Occupy small chambers called lacunae and are completely within
the matrix
Cartilage
• Cartilaginous structure is enclosed in a covering of
connective tissue call perichondrium
• Perichondrium contains blood vessels that provide
cartilage cells with nutrients by diffusion
• Cartilage does not heal quickly and chondrocytes do not
divide frequently because of a lack of a direct blood
supply
Cartilage
• Three types of cartilage:
• Hyaline cartilage
• Elastic cartilage
• Fibrocartilage  matrix similar to hyaline cartilage but less firm with
thick collagen fibers
• Provides tensile strength and absorbs compression shock
• Found in the intervertebral discs, the pubic symphysis, and in discs of
the knee joint
Hyaline Cartilage
• Amorphous, firm matrix w/ imperceptible network of
collagen fibers
• Supports, reinforces, cushions, and resists compression
• Found in embryonic skeleton, the end of long bones, nose, trachea,
and larynx
Elastic Cartilage
• Similar to hyaline cartilage but with more elastic fibers
• Maintains shape and structure while allowing flexibility
• Supports external ear (pinna) and the epiglottis
Fibrocartilage
• Matrix similar to hyaline cartilage but less firm with thick
collagen fibers
• Provides tensile strength and absorbs compression shock
• Found in the intervertebral discs, the pubic symphysis, and in discs
of the knee joint
Bone
• Hard, calcified matrix with collagen fibers found in bond
• Osteocytes are found in lacunae and are well
vascularized
• Supports, protects, and provides levers for muscular
action
• Stores calcium, minerals, and fat
• Marrow inside bones is the site of hematopoiesis 
making of red blood cells
Bone
Blood
• Red and white cells in a fluid matrix (plasma)
• Contained within blood vessels
• Functions in the transport or respiratory gases, nutrients,
and wastes
Nervous Tissue
• Branched neurons with long cellular processes and
support cells
• Transmits electrical signals from sensory receptors to
effectors
• Receptors  Brain  Effectors
• Found in the brain, spinal cord, and peripheral nerves
Nervous Tissue
Muscle Tissue
• Contractile – the elongated cells (muscle fibers) can
shorten
• As muscle tissues contract, the fibers pull at their attached
ends
• This moves body parts
• Three types:
• Skeletal
• Smooth
• Cardiac
Skeletal Muscle Tissue
• Long, cylindrical, multinucleated cells with obvious
striations
• Multinucleated because many cells are fused together to make 1
long cell
• Initiates and controls voluntary movement
• Found in skeletal muscles that attach to bones or skin
Skeletal Muscle Tissue
Smooth Muscle Tissue
• Sheets of spindle-shaped cells with central nuclei that
have no striations  why its called smooth
• Shorter than skeletal muscle
• Usually can’t be stimulated to contract by conscious
efforts
• Propels substances along internal passageways
• Ex) food down the digestive tract, constricts blood vessels, empties
the urinary bladder
• Found in the walls of hollow organs
• Stomach, intestines, urinary bladder, uterus, blood vessels
Smooth Muscle Tissue
Cardiac Muscle Tissue
• Only found in the walls of the heart
• Cells are striated with a single nucleus
• Where cells connect to one another it is a specialized
intercellular junction  intercalated disk
• Cardiac muscle is controlled involuntarily
• Pumps blood through the heart chambers and into blood
vessels
Cardiac Muscle Tissue