T11 Chapter 4 The Tissue Level of Organization - Copy - Copy.pdf

Principles of Human Anatomy and Physiology, 11e
1
Chapter 4
The Tissue Level of Organization
Lecture Outline

INTRODUCTION
•
A tissue is a group of similar cells that usually have a similar
embryological origin and are specialized for a particular
function.
•
The nature of the extracellular material that surrounds the
connections between the cells that compose the tissue
influence the structure and properties of a specific tissue.
•
Pathologists , physicians who specialize in laboratory studies
of cells and tissues, aid other physicians in making
diagnoses; they also perform autopsies.

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Chapter 4 The Tissue Level of
Organization
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Histology
–
the study of tissues

TYPES OF TISSUES AND THEIR ORIGINS
Four principal types based on function and structure
•
Epithelial tissue
–
covers body surfaces, lines hollow organs, body cavities,
and ducts; and forms glands.
•
Connective tissue
–
protects and supports the body and its organs, binds
organs together, stores energy reserves as fat, and
provides immunity.
•
Muscle tissue
–
is responsible for movement and generation of force.
•
Nervous tissue
–
initiates and transmits action potentials (nerve impulses)
that help coordinate body activities.

Origin of Tissues
•
Primary germ layers within the embryo
–
endoderm
–
mesoderm
–
Ectoderm
•
Tissue derivations
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epithelium from all 3 germ layers
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connective tissue & muscle from mesoderm
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nerve tissue from ectoderm
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Table 29.1 provides a list of structures derived
from the primary germ layers.

DEVELOPMENT
•
Normally, most cells within a tissue remain in place,
anchored to
–
other cells
–
a basement membranes
–
connective tissues
•
Exceptions include phagocytes and embryonic cells involved
in differentiation and growth.

Biopsy
•
Removal of living tissue for microscopic examination
–
surgery
–
needle biopsy
•
Useful for diagnosis, especially cancer
•
Tissue preserved, sectioned and stained before microscopic
viewing

CELL JUNCTIONS
•
Cell junctions are points of contact between adjacent
plasma membranes.
•
Depending on their structure, cell junctions may serve one
of three functions.
–
Some cell junctions form fluid-tight seals between cells.
–
Other cell junctions anchor cells together or to
extracellular material.
–
Still others act as channels, which allow ions and
molecules to pass from cell to cell within a tissue.

CELL JUNCTIONS
•
The five most
important kinds of
cell junctions are
tight junctions,
adherens
junctions,
desmosomes,
hemidesmosomes,
and gap junctions
(Figure 4.1)

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Cell Junctions
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Tight junctions
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Adherens junctions
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Gap junctions
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Desmosomes
•
Hemidesmosomes

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Tight Junctions
•
Watertight seal between cells
•
Plasma membranes fused with
a strip of proteins
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Common between cells that line
GI and bladder

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Adherens Junctions
•
Holds epithelial cells together
•
Structural components
–
plaque = dense layer of