Transcript The Tissue Level Of Organization

The Tissue Level Of
Organization
Chapter 4
Introduction
• Tissues are collection of specialized
cells and cell products that are
organized to perform a relatively
limited number of functions.
• The four tissue types are:
– Epithelial tissue, connective tissues,
muscle tissue and neural tissue
Histology is the study of tissues
Epithelial Tissue
• A epithelium is an avascular layer
of cells that form a barrier that
covers internal or external
surfaces.
• Glands are secretory structures
derived from epithelia
Functions of Epithelia
• Epithelia provide physical
protection, control permeability,
provide sensations, and produce
specialized secretions.
– Gland cells are epithelial cells that
produce secretions.
• Exocrine secretions are released onto
body surfaces
• Endocrine secretions, known as
hormones, are released by gland cells
into the surrounding tissues.
Intercellular Connections
• The individual cels that make up
tissues attach to one another or to
extracellular protein fibers in three
major ways:
– Tight junctions, gap junctions and
desmosomes
• At a tight junction, the outer
surfaces of the two cell
membranes are bound tightly
together.
• These are the strongest
intercellular connections.
• At a gap junction, two cells are
held together by interlocked
membrane proteins, forming a
narrow passageway
• A desmosome has a very thin layer
of intercellular cement between
the cell membranes, reinforced by
a network of protein fibers.
The Epithelial Surface
• Many epithelial cells have
microvilli, and some have
stereocilia. The coordinated
beating of the cilia on a ciliated
epithelium moves materials across
the epithelial surface.
The Basement Membrane
• The inner surface of each
epithelium is connected to a
noncellular basement membrane.
Epithelial Renewal and
Repair
• Divisions by stem cells, or
germinative cells, continually
replace the short-lived epithelial
cells.
Classifying Epithelia
• Epithelia are classified on the basis
of the number of cell layers and
the shape of the exposed cells.
Simple epithelium
• Simple epithelium
has a single layer
of cells covering
the basement
membrane
Stratified epithelium
• Stratified
epithelium has
several layers
Squamous epithelium
• In squamous
epithelium the
cells are thin and
flat
Cuboidal epithelium
• The cells
resemble little
hexagonal boxes
Columnar epithelium
• The cells are
taller and more
slender.
Glandular Epithelia
• A glandular epithelial cell may
release its secretions through
– Merocrine
– Apocrine
– holocrine
• Merocrine secretions:
– The most common method of
secretion,
– The product is released through
exocytosis
• Apocrine secretion
– Involves the loss of both secretory product
and cytoplasm
– Holocrine secretion
• Unlike the first two methods, this
destroys the cell, which becomes packed
with secretions and finally bursts.
• Exocrine secretions may be
serous(watery, usually containing
enzymes)
• Mucous-thick and slippery
• Mixed-containing enzymes and
lubricants.
Epithelium Quiz
What is this type of
epithelium?
???
• What about this?
Answers
• Simple cuboidal
• Stratified columnar
• Simple columnar.
Connective tissues
• All connective tissues have
specialized cells and a matrix,
composed of extracellular protein
fibers and a ground substance.
• Connective tissues are internal tissues
with many important functions
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Establishing a structural framework
Transporting fluids and dissolved materials
Protecting delicate organs
Supporting, surrounding, and
interconnecting tissues
– Storing energy reserves
– Defending the body from microorganisms.
Classifying connective
tissues
• Connective tissue proper refers to
connective tissues that contain
varied cell populations and fiber
types surrounded by a syrupy
ground substance.
• Fluid connective tissues have a
distinctive population of cells
suspended in a watery ground
substance containing dissolved
proteins
• The two types are blood and lymph
• Supporting connective tissues have
a less diverse cell population than
connective tissue proper and a
dense matrix that contains closely
packed fibers.
• The two types of supporting
connective tissues are cartilage
and bone.
Connective tissue Proper
• Connective tissue proper contains
fibers, a viscous ground substance,
and a varied cell population.
• Resident and migrating cells may
include fibroblasts, macrophages,
rat cells, mast cells and various
white blood cells.
• There are three types of fiber in
connective tissue
– Collagen fibers
– Reticular fibers
– Elastic fibers.
• Connective tissue proper is
classified as loose or dense
connective tissues.
• Loose connective tissues include
loose connective tissue, or areolar
tissue and adipose tissue.
• Most of the volume in dense
connective tissues consists of
fibers.
• Dense connective tissues form
tendons and ligaments.
Fluid Connective tissues
• Blood and lymph
are connective
tissues that
contain distinctive
collections of cells
in a fluid matrix
• Blood contains red blood cells, white
blood cells, and platelets
• The watery ground substance is called
plasma.
• Arteries carry blood from the heart and
toward capillaries, where water and
small solutes move into the interstitial
fluid of surrounding tissues.
• Veins return blood to the heart.
• Lymph forms as interstitial fluid
enters the lymphatic vessels,
which return lymph to the
cardiovascular system.
Supporting Connective
Tissues
• Cartilage and bone are called
supporting connective tissues
because they support the rest of
the body.
• The matrix of cartilage consists of
a firm gel and cells called
chondrocytes.
• A fibrous perichondrium separates
cartilage from surrounding tissues.
• The three types of cartilage are
hyaline cartilage, elastic cartilage
and fibrocartilage.
• Chondrocytes rely on diffusion
through the avascular matrix to
obtain nutrients.
• Bone or osseous tissue, has a matrix
primarily consisting of collagen fibers
and calcium salts which give it unique
properties.
• Osteocytes depend on diffusion through
canaliculi for nutrient intake.
• Each bone is surrounded by a
periosteum.
Membranes
• Membranes form a barrier or an
interface. Epithelia and connective
tissues combine to form
membrane that cover and protect
other structures and tissues.
• There are four types of
membranes
– Mucous, serous, cutaneous, and
synovial.
Mucous membranes
• Mucous membrane line cavities
that communicate with the
exterior. Their surfaces are
normally moistened by mucous
secretions.
Serous membranes
• Serous membranes line internal
cavities and are delicate, moist,
and very permeable.
Cutaneous membranes
• The cutaneous membrane covers
the body surface. Unlike serous
and mucous membranes, it is
relatively thick, waterproof, and
usually dry.
Synovial Membranes
• Synovial membranes, located at
joints, or articulations, produce
synovial fluid in joint cavities.
Synovial fluid helps lubricate the
joint and promotes smooth
movement.
Identify the following
connective tissues
And the answers are….
• Elastic cartilage
• Blood
• Hyaline cartilage
• Bone
• Adipose
• Areolar
Muscle Tissue
• Muscle tissue is specialized for
contraction.
• The three types of muscles tissue
are:
– Skeletal muscle
– Cardiac muscle
– Smooth muscle.
Skeletal Muscle Tissue
• Skeletal muscle tissue contains large
cells, or muscle fibers, tied together by
collagen and elastic fibers.
• Skeletal muscle fibers are
multinucleated and have a striped
appearance because of the organization
of contractile proteins.
• Because we can control the
contraction of skeletal muscle
fibers through the nervous system,
skeletal muscle can be considered
striated voluntary muscle.
Cardiac Muscle Tissue
• Cardiac muscle tissue is found only
in the heart.
• The nervous system does not
provide voluntary control over
cardiac muscle cells.
• Cardiac muscle is striated
involuntary muscle.
Smooth Muscle Tissue
• Smooth muscle tissue is found in
the walls of blood vessels, around
hollow organs, and in layers
around various tract.
• It is classified as nonstriated
involuntary muscle.
Identify the following
muscle types
• What char. Help
you identify the
type of muscle?
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Striations?
Nuclei?
Branching?
Intercalated
disks?
• Characteristics
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Striations?
Branching?
Nuclei?
Intercalated
disks?
• Characteristics?
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Striations?
Nuclei?
Branching?
Intercalated
disks?
And the Answers are…
• Cardiac tissue
– Branching, striated, intercalated disks
• Smooth muscle Tissue
– No branching, not striated, single
nucleus
• Skeletal Muscle Tissue
– Striated, multiple nuclei
Neural Tissue
• Neural tissue is specialized to
conduct electrical impulses that
convey information from one area
of the body to another.
• Cells in neural tissue are either
neurons or neuroglia.
• Neurons transmit information as
electrical impulses in their cell
membranes.
• Several kinds of neuroglia serve
both supporting and defense
functions.
• A typical neuron
has a cell body,
dendrites, and an
axon, which ends
at synaptic
terminals.
Tissue Injuries and
Repairs
• Any injury affects several tissues
types simultaneously, and they
respond in a coordinated manner.
• Homeostasis is restored in two
processes
– Inflammation and regeneration
• Inflammation or the inflammatory
response, isolates the injured area
while damaged cells, tissue
components, and any dangerous
microorganisms are cleaned up.
• Regeneration is the repair process
that resores normal functions.
Tissues and Aging
• Tissues change with age. Repair and
maintenance grow less efficient and the
structure and chemical composition of
many tissues are altered.
• Cancer incidence increases with age,
with roughly three-quarters of all cases
caused by exposure to chemicals or
environmental factors.