Chapter 4
Tissues
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• Tissue: a group of similar cells with
similar functions
• Four basic types of tissues
1.
2.
3.
4.
Epithelial
Connective
Muscle
Nerve
4.1 Epithelial Tissues
• Five distinguishing characteristics
1. Closely packed cells
2. Attached to connective tissue by a
basement membrane
3. Tissue surface opposite the basement
membrane is not attached to other
tissues
4. Tissue has no blood vessels
5. Tissues regenerate rapidly
• Functions vary with location and tissue
type
– Protection, absorption, filtration, secretion
• Glandular epithelium can be found
inside glands
– Exocrine glands
– Endocrine glands
4.2 Connective Tissues
•
•
•
•
•
Most abundant body tissues
Support and bind other tissues
Never found on exposed surfaces
Have the ability to regenerate
Consist of few, loosely arranged cells and
intercellular substance called matrix
• Two broad categories of connective
tissues
– Connective Tissue Proper
• Common tissues that bind other tissues and
organs
– Connective tissues with specialized
functions
• Connective Tissue Proper
– Functions
• Bind together other tissues
• Basic supporting framework of organs
– Matrix consists of ground substance
– Fibroblasts are the most abundant cells
– Two types of protein fibers
• Collagenous fibers
• Elastic fibers
– Loose connective
tissue, or Areolar
• Most abundant in body
• Named for its loosely
arranged protein fibers
• Attaches skin to muscles
• Supporting framework for
internal organs, nerves,
blood vessels
• Site for immune reactions
– Adipose tissue
• Has large numbers of
adipocytes that store
fat droplets
• Common beneath skin
and around internal
organs
• Aids in fat storage and
body insulation
• Provides a protective
cushion
– Fibrous connective
tissue
• Has an abundance of
tightly packed
collagenous fibers
and few cells
• Great strength and
flexibility
• Component of
ligaments, tendons,
and dermis
• Poor blood supply
resulting in slow
healing
– Elastic connective tissue
• Has an abundance of elastic fibers
• Found where elasticity is needed
• Lungs, air passages, arterial walls
• Cartilage
– Semisolid matrix with embedded
chondrocytes living in lacunae
– Major functions are support and protection
– There are three types of cartilage
• Hyaline cartilage
• Elastic cartilage
• Fibrocartilage
• Bone or osseous tissue
– Hardest and most rigid due to calcium salts in
its matrix, along with collagenous fibers
– Provides rigidity and strength to support the
body
– Matrix is deposited in lamellae around
osteonic (Haversian) canals
– Osteocytes, located between lamellae, are
connected by canaliculi
• Blood
– Consists of numerous cells in a liquid matrix
– Three types of cells
• Red blood cells
• White blood cells
• Platelets
– Vital role in transporting material throughout the body
4.3 Muscle Tissues
• Cells are unable to divide so regeneration
is not possible
• Cells are called muscle fibers due to their
long, thin appearance
• Cells use specialized protein fibers for
contraction
• Contraction moves the body and
produces heat
• Skeletal Muscle
Tissue
– Attached to bones
and move the body
– Voluntary muscle
– Cells are elongated
and cylindrical, with
many nuclei and
striations
• Cardiac Muscle Tissue
– Found only in walls of heart
– Involuntary muscle
– Branching muscle fibers that interconnect at
intercalated discs
– Possess one nucleus and striations
• Smooth Muscle Tissue
– Occurs in the walls of hollow organs
– Involuntary muscle
– Cells possess a spindle shape, one nucleus, and
not striations
4.4 Nerve Tissue
• Found in brain, spinal cord, and nerves
• Two main types of cells
– Neurons
– Neuroglia
• Neuroglia are supporting cells that
nourish, insulate, and protect neurons
• Neurons
– The functional units of nerve tissue
– Possess a cell body and one or more neuron process
– Respond to environmental changes by making neural
impulses
4.5 Body Membranes
• Thin sheets of tissue
• Line cavities, cover surfaces, or
separate tissues or organs
• Two types of body membranes
– Epithelial membranes
– Connective tissue membranes
• Epithelial Membranes
– Composed of epithelial tissue overlying
loose connective tissue
– Serous membranes
• Line ventral body cavity and cover internal
organs
• Secrete serous fluid to reduce friction
• Examples: pleurae, pericardium, peritoneum
– Mucous membranes
•
•
•
•
Line tubes and cavities open to the exterior
Possess goblet cells to make mucus
Keeps cells moist and lubricated
Examples: digestive and respiratory tracts
– Cutaneous membrane
• Skin
• Connective Tissue Membranes
– Formed only of connective tissue
– Examples:
1.
2.
3.
4.
Meninges
Perichondrium
Periosteum
Synovial membrane
Tissue Repair
• Following minor injuries, tissues repair
themselves by regeneration
– the division of the remaining intact cells.
• The capacity to regenerate varies
among different tissues.
Tissue Repair
– Epithelial tissues, loose connective tissue,
and bone readily regenerate.
– Cartilage and skeletal muscle have little
capacity for regeneration.
– Cardiac muscle never regenerates.
– Nerve tissue in the brain and spinal cord
usually does not regenerate.
Tissue Repair
• After severe injuries, repair
involves fibrosis, the formation of scar tissue.
– Formed by an excess production of collagenous
fibers by fibroblasts.
– A keloid is a mass of scar tissue forming on the
skin surface due to excessive connective tissue
– Scar tissues that join together tissues or organs
abnormally are called adhesions, which
sometimes form following abdominal surgery.
Tissues and Tumors
• Because epithelial and connective tissue cells
are active in cell division, they are prone to
the formation of tumors when normal control
of cell division is lost.
• The most common types of cancer arise from
epithelial cells
– possibly due to increase exposure
to carcinogens, cancer-causing agents, in the
environment.
Tissues and Tumors
• A cancer derived from epithelial cells is called
a carcinoma.
• Malignant tumors that originate in connective
tissue are also common types of cancer. A
cancer of connective tissue is called
a sarcoma.